wabco brakes 3

1011

5.

EBS - Electronically ControlledBraking System

102 1

EBS - Electronically Controlled Braking System5.

Introduction: Increasing competition in the transporttrade has also caused the requirementsfor braking systems to be increasedsteadily. The introduction of the Elec-tronically controlled Braking SystemEBS is the logical step to meet this andother requirements. EBS permits perpet-ual optimized balancing of the brakingforces among the individual wheelbrakes, and of the towing vehicle and itstrailer.

The comprehensive diagnostic and mon-itoring functions of the Electronicallycontrolled Braking System are one of thebasic requirements for effective fleet lo-gistics. EBS enhances vehicle and roadsafety by means of reducing the stoppingdistance, achieving improved brakingstability and montitoring the braking sys-tem. In addition, EBS considerably im-proves both economic efficiency anddriving comfort.

Benefits of EBS EBS Effectively Reduces Maintenance Costs.

� EBS combines a large number offunctions. The objective is to reducemaintenance costs whilst maximizingbraking safety, e.g. by minimizinglining wear of the wheel brakes.

� Individual control according to thewear criteria on both front and rearaxles harmonizes lining wear. Byevenly spreading the load across allwheel brakes, total wear is minimi-zed. In addition, maintenance andlining change intervals coincide. Lai-dup costs are drastically reduced.

System Design For this reason, EBS will be included innew vehicle series, the pioneer beingACTROS from Daimler-Benz which hasan electronically controlled air brakingsystem fitted as standard equipment.This system by name of ”Telligent®Braking System“ from Daimler-Benz (for-merly EPB), is a joint development byDaimler-Benz and WABCO.

Please note:The term ”Telligent® Braking System“comprises the whole of the braking sys-tem, not only its controlling system whichwe call EPB.

The ACTROS ”Telligent® Braking Sys-tem“ contains some specific Daimler-Benz features for which WABCO, in ap-plications for vehicles from other manu-facturers, has substituted its ownsolutions. These include the followingfunctions described in the publication inmore detail:

– redundancy valve, rear axle redun-dancy

– special control functions in the areaof brake force distribution (differenti-al, drive-slip control DSR), liningwear control and trailer control

– testing and diagnostic methods typi-cal for ACTROS.

Modular Design of WABCO EBSThe configuration and the structure ofWABCO’s EBS permits a high degree offlexibility for the vehicle manufacturer

when designing the system. For this rea-son, the most varied of needs can bemet:

• partial or full system,• type of redundancy, • trailer control strategy, • elecrical interfaces, etc.

For meeting the essential requirementsof the vehicle owner, WABCO recom-mends an EBS which comprises indivi-dual pressure control on front and rearaxles and trailer control, and which provi-des for pneumatic redundancies in allbraking circuits.

This EBS consists of a dual circuit andan overriding single-circuit electro-pneu-matic circuit. This configuration is descri-bed as 2P/1E-EBS.The single circuit electro-pneumatic partof the system consists of one centralelectronic control unit (central module),the axle modulator with integrated elec-tronics for the rear axle, a brake signaltransmitter with parely pneumatical inte-grated stroke sensors and brake swit-ches, an electro-pneumatic control valveand two ABS valves for the front axle,plus an electro-pneumatic trailer controlvalve.An expansion of this configuration by anadditional axle modulator for the rear ax-les would then provide a 6-channel EBS.The structure of the subordinate dual-cir-cuit pneumatic part of the system is basi-cally identical with that of a conventionalbraking circuit. This part of the systemserves as a backup and becomes effec-tive only if the electro-pneumatic circuitfails.

1031

EBS - Electronically ControlledBraking System 5.

EBS Brake System for Track 4x2:

Legend: 1 Central Module 4 Solenoid Modulator Valve - ABS 7 Trailer Control Valve2 Brake Signal Transmitter 5 Rear Axle Modulator3 Proportional Relay Valve 6 Backup Valve

104


Legend:

1 Brake Signal Transmitter (BWG)2 Proportional-Relay Valve3 Solenoid Modulator Valve - ABS4 Speed Sensor5 Wear Sensor6 Backup Valve7 Rear Axle Modulator8 Trailer Control Valve

Function Scheme:

105


The brake signal transmitter is used togenerate electrical and pneumatic si-gnals to apply to, or release pressurefrom, the Electronically controlled Bra-king System (EBS). This unit is designedfor two pneumatic and electrical circuitsrespectively. Commencement of actuati-on is electrically recorded. The start ofactuation is electrically perceived by adouble switch (1). The travel of the actu-ating plunger (b) is picked up and resultsin the pulse-width modulated output as

an electrical signal. In addition, the pneu-matic redundancy pressures in Circuits 1(Port 21) and 2 (Port 22) are transmitted,that of Circuit 2 being retained slightly.Via an additional pilot connection 4 it ispossible (at a customer’s specific re-quest) to adjust the pneumatic charac-teristic of the 2nd circuit. In the event ofone circuit failing (electrical or pneumat-ic), the other circuits remain operational.

Brake Signal Transmitter480 001 . . . 0

The central module is used to controland monitor the Electronically controlledBraking System. From the signal re-ceived from the brake signal transmitterit determines the vehicle’s intended re-tardation. Together with the wheelspeeds measured by the wheel speedsensors, the intended retardation is theinput signal for EBS control which usesthese readings to establish the indexpressure values for the front and rear ax-les and the trailer control valve. The in-dex pressure for the front axle iscompared with the actual value taken,and any differences are balanced bymeans of the proportional relay valve.

Output of the trailer control pressure isachieved in a similar manner. In addition,the wheel speeds are evaluated to com-mence ABS control by modulating thebrake pressures in the brake cylinders inthe event of the wheels showing a ten-dency to lock. The central module ex-changes data, via the EBS system bus,with the axle modulator (or axle modula-tors in 6S/6M systems). Electrical braking systems for trailers areactuated via a data interface to ISO11992. The central module communi-cates with other systems of the towingvehicle (engine control, retarder, etc.) viaa vehicle data bus.

Central Module446 130 . . . 0

Zentralmodul Central Module

106


Proportional Relay Valve 480 202 ... 0

In the Electronically controlled BrakingSystem, the proportional relay valve isused as an actuator for the output ofbrake pressures at the front axle.

It consists of a proportional solenoidvalve (a), a relay valve (b) and a pres-sure sensor (c). Electrical actuation andmonitoring are effected by the centralmodule of the hybrid system.

The control current determined by theelectronics is converted by the propor-

tional relay valve (a) into control pressurefor the relay valve. The output pressure(port 2) of the proportional relay valve isproportional to that pressure. The pneu-matic actuation of the relay valve (port 4)is effected by the redundant pressure ofthe brake signal transmitter (port 22).

Backup Valve 480 205 ... 0

The backup valve is used to rapidly in-crease or decrease the pressure for thebrake cylinders on the rear axle in thecase of a backup; it consists of severalvalve units which have to perform the fol-lowing functions, among others:

� 3/2-way valve to prevent backup ope-ration if the electro-pneumatic bra-king circuit is not defective

� relay valve function for improving thetime response of the backup

� pressure retention in order to syn-chronize the commencement of pres-sure output on the front and rearaxles in the event of a backup

� pressure reduction to avoid overbra-king of the rear axle to the largestpossible extent in the case of a backup.

107


The axle modulator controls the brakecylinder pressures on both sides of oneor two rear axles. It contains two inde-pendent pneumatic pressure controlchannels (Channels A and B), each con-taining one inlet and one exhaust valve,plus one pressure sensor, sharing oneelectronic control unit. The index pres-sures and external monitoring functionsare provided by the central module.

In addition, two speed sensors monitorand evaluate the wheel speeds. In theevent of a tendency to lock or to spin be-ing detected, the index value provided isadjusted.

Two sensors can be connected for mon-itoring lining wear.

The axle modulator has one additionalport for connecting a backup pneumaticbraking circuit. One double check valveper side transmits the higher of the twopressures (electro-pneumatic or redun-dant) to the brake cylinder.

Axle Modulator480 103 . . . 0

108 1


Trailer Control Valve 480 204 . . . 0

In the Electronically controlled BrakingSystem, the trailer control valve is usedas a control element to output the hosecoupling pressures.

The trailer control valve consists of a pro-portional solenoid valve (a), a relay valve(c), a breakaway emergency valve (d)and a pressure sensor (b). Electrical ac-tuation and monitoring are effected bythe central module.

The control current determined by theelectronics is converted by the propor-

tional solenoid valve into control pres-sure for the relay valve. The outputpressure of the trailer control valve isproportional to that pressure.

The pneumatic actuation of the relayvalve is effected by means of the backuppressure from the brake signal transmit-ter (port 42) and the output pressurefrom the hand brake valve (port 43).

1091

EBS On The Trailer The scheme on page 64 and 65 eachshow EC air braking systems widelyused in Europe today. On a semitrailer,this braking system essentially consistsof a relay emergency valve, a load-sens-ing valve and the ABS.In the Vario-Compact System shownhere, the ABS relay valves and the elec-tronic control unit have been combined.Frequently, however, these componentsare fitted separately. On the drawbartrailer, another load-sensing valve, athird ABS relay valve, an adapter valveon the front axle and a pressure limitingvalve on the rear axle are added to thecomponents listed above. Although thisEC braking system is now highly sophis-ticated, especially through the use ofABS, there is still room for the improve-ments listed below:

� Reduction of the variety/number ofcomponents and thus installationscosts.

� Dispensing with the required air val-

ves and their adjustment by introdu-cing electronic control and the simplesetting of parameters this permits.

� By using pressure control circuitswhich operate with a high degree ofprecision, it is possible to almostcompletely eliminate the deviations incharacteristics encountered today.

� The ”electrical brake line“ and elec-tronic control can considerably impro-ve the time response and thuscontribute towards reducing the stop-ping distance and improving the sta-bility of the tractor-trailer combination.

� Extending the diagnostic features forthe whole of the braking system,including maintenance and repair in-structions.

It was these possible improvementswhich provided the basis for the develop-ment of an electronically controlled EBSon the trailer

EBS For Semitrailers 4S/2M1 EBS relay emergency valve2 EBS trailer modulator3 ABS sensor4 axle load sensor5 pressure sensor6 pressure switch7 redundancy valve

System DescriptionFi. 1 shows the standard EBS for a 3-axle semitrailer. It electronically controlslateral braking pressures. The systemconsists of a compact dual-circuit trailermodulator with a digital data interface toISO 1199-2 to the EBS towing vehicle,an EBS relay emergency valve, an axleload sensor and ABS sensor. When used

on drawbar trailers or semitrailers with asteering axle, a system is needed whichincludes an additional EBS relay valveon the steering axles, see Fig 2.

Trailers with the electronic braking sys-tem described must be compatible withboth conventional towing vehicles andtowing vehicles which use EBS, allowing


Abb. 1 Fig. 1

Reserve

Brake

110 1

EBS For Drawbar Trailers4S/2M1 EBS relay emergency valve2 EBS trailer modulator3 ABS sensor4 axle load sensor5 pressure sensor6 pressure switch7 redundancy valve8 EBS relay valve

pneumatic redundant braking in theevent of EBS failure. This results in three possible types of op-eration:

Operation with new towing vehicleswith EBS and extended ISO-7638plug-in connection with CAN inter-face.

All EBS functions can be utilized. Thetrailer receives the index values from thetowing vehicle via the data interface.

Oeration with conventional towing ve-hicles with ISO-7638 plug-in connec-tion for the trailer’s ABS supply butwith no CAN interface

All EBS functions can be utilized, with theexception of the transmission of the in-dex values via the CAN data interface.

The index values are provided by thepressure sensor in the relay emergencyvalve which picks up the actuating pres-sure for the trailer.

Redundancy Operation

In the event of a failure of the electricalvoltage supply, ordinary pneumatic brak-ing can always be achieved, althoughwith no load-sensing or ABS functions.In redundancy operation, the time re-sponse is similar to that of today’s con-ventional braking systems. If the EBStrailer is operated pneumatically, an im-proved time response is achieved sinceelectrical sensing of the actuating pres-sure saves time. When used with an EBStowing vehicle and actuation via CAN,the pressure in the EBS trailer builds upalmost simultaneously with that in thetowing vehicle.


Abb. 2

Reserve

Brake

Fig. 2

1111

6.

Air Suspension Systems And ECAS(Electronically Controlled Air Suspension)

112 1

Air Suspension Systems6.In commercial vehicles and motor coach-es, more and more air-suspensions arebeing used.

In commercial vehicles with interchange-able platforms they achieve a considera-ble reduction in loading and unloadingtimes. On coaches, ride comfort is im-proved by means of the spring force be-ing adjusted to the number ofpassengers travelling on the coach and aboarding level which remains the sameat all times.

Air Suspension SystemWhen planning and designing air sus-pension systems, the following systemtypes have been used to date:

� a)air suspensions with a closed aircircuit

� b)air suspensions with a semi-closedair circuit

� c)air suspensions with an open aircircuit.

The systems mentioned under a) and b)are mainly used in passenger cars, theirbenefit being that they consume a smallamount of air so that the compressor canbe smaller due to its lesser delivery re-quirements. In addition, there is little con-densate or dirt. Such systems are,however, technically complex and fairlyexpensive to buy.

For that reason, motor coaches andcommercial vehicles use air suspensionsystems with an open air circuit. Sincethis system evacuates air which is not re-quired back to atmosphere, the air com-pressor has to be larger. This type of airsuspension system is straightforward interms of its circuit and the valves it uses.

Of course neither types of suspension(mechanical spring suspension elementsor air suspension systems) can meet alltechnical requirements. Comparing bothsystem types, however, shows that airsuspensions offer significant advantagesover mechanical suspensions. This ap-plies especially where the wheel suspen-sion elements are to be separated fromother suspension members to achievebetter road holding qualities.

Benefits of Air Suspension Systems

1. By adjusting the bellows pressure asa ratio of the load carried, the dis-tance between the road surface andthe vehicle’s superstructure will al-ways be the same. This means thatnot only is the boarding or loadinglevel constant, but also the headlightsetting.

2. Due to the adjusting pressure in thebellows, spring comfort is not sub-ject to any major changes, regard-less of the load carried. Thepassenger on a motor coach will al-ways perceive the same pleasanttype of oscillation. Sensitive loadsare carried without any major dam-age. An empty or partially laden ve-hicle will no longer ‘jump’.

3. Both steering stability and the trans-mission of brake forces are im-proved since tyre-road adhesion isalways achieved for all wheels.

4. The pressure in the air suspensionbellows which is dependent on theload carried is also ideal for control-ling load-sensitive braking (‘ALB’).

5. In interchangeable platform opera-tion, air suspension systemsachieve efficient loading and unload-ing of container vehicles.

6. Protects the road surface.

In an air suspension system, the equip-ment for air compression, for the storageof compressed air and for pneumaticcontrol must form a unit with the wheelsuspension and other elements. The dia-gram on this page illustrates this for anair suspension system on semitrailers.

2, 3 41 42

21

ALB-Regler

Vorrat

von derBetriebsbremsanlage 6

4

1

5

Luftfederbalg

8

1 21

7

8

2221

2423

191 2

1 2

22

2312

Example for Semitrailers (raise and lower)

supply

from the servicebraking system

air suspension bellows

load-sensing valve

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Purpose:To control the pressure in the air suspen-sion bellows in proportion to the vehicleload.Levelling Valve 464 006 100 0 has anadditional 3/2 directional control valvewhich closes from a pre-defined, adjust-able lever angle and which takes on anexhaust function when the lever ismoved further. This "height limitation"prevents the vehicle being raised abovethe permissible level by means of theraise/lower valve.

Operation:The vehicle body with its levelling valvewill move down as the load on the bodyis increased. The linkage between thevehicle axle and the levelling valve rais-es both lever (f) and guide (d) via eccen-tric cam (e). As guide (d) moves up, italso lifts its pin, thus opening inlet valve(b), allowing air from the reservoir to flowthrough the valve via port 1 and checkvalve (a) into the air bellows which areconnected to ports 21 and 22. In order tominimize air consumption, the outside ofthe pin is machined in such a way thatthe passage of air through the valve isregulated at two levels depending on thedeflection of lever (f).

As the pressure in the air bellows in-creases, the chassis height is adjusted,and lever (f) causes inlet valve (b) toclose. In this position, ports 21 and 22are connected to each other via a trans-verse throttle.

When the vehicle load is decreased, thereverse process takes place. The vehiclechassis is now raised by the excesspressure in the air suspension bellowsand lever (f) with eccentric cam (e) andguide (d) are pulled down. This causesthe pin to be moved downwards from itsseat on inlet valve (b), permitting excesspressure from the air bellows to escapeto atmosphere via drilling (c) and ventholes 3. With this drop in pressure in theair bellows, the chassis height is loweredand lever (f) is returned to its normal hor-izontal position. As drilling (c) is blockedby the pin resting on inlet valve (b), thelevelling valve is again in a balanced po-sition.

Levelling Valve464 006 . . . 0

Air Suspension Systems 6.

114 1

Raise/Lower Valve463 032 . . . 0

Purpose:To raise and lower the chassis of air-sprung semi-trailers and vehicles with in-terchangeable platforms (lifting facility).

Operation:In the "travelling" position of the hand le-ver, the lifting mechanism is inoperative.The raise/lower valve allows the freepassage of air from the levelling valves(ports 21 and 23) to the air suspensionbellows (ports 22 and 24).

The valve also permits four more posi-tions of the hand lever for filling and emp-tying the air suspension bellows forraising and lowering purposes.

To raise the chassis, the hand lever isunlocked by axial pressure and moved tothe "raise" position in which ports 21 and23 are closed, blocking the action of thelevelling valves, while the suspensionbellows 22 and 24 are connected to thereservoir by port 1.

When the required lift height has beenattained, the hand lever is moved to the

"raise stop" position in which the levellingvalve ports 21 and 23 and the suspen-sion bellows ports 22 and 24 are closed.The platform supports can now beswung into position.

It is then necessary to lower the chassisbelow its normal level to deposit the con-tainer or platform on the supports and todrive out the chassis. This is done withthe hand lever in the "lower" position. Asin the "raise" position, ports 21 and 23are closed but air suspension bellows 22and 24 are now exhausted through ex-haust port 3.

This operation, too, is terminated bymoving the lever to the "lower stop" posi-tion. Ports 21, 23, 22 and 24 are closed.Before the vehicle is driven, the hand le-ver must be moved to the "travelling" po-sition to allow the levelling valves to bere-connected to the air bellows.

Air Suspension Systems6.

212223

24

13

STOP STOP

I II III IV V

1151

The letters ECAS stand for

ElectronicallyControlledAirSuspension

ECAS is an Electronically Controlled AirSuspension system for vehicles and in-cludes a large number of functions. Theconventional system has been signifi-cantly enhanced through the use of anElectronic Control Unit (ECU):

� Reduction of air consumed whilst thevehicle is moving

� It is possible to maintain different le-vels (e.g. ramp operation) by meansof automatic readjustment

� In the case of complex systems, in-stallation is easier

� Additional functions such as tractionhelp, programmable vehicle levels,tyre deflection compensator, over-load protection and automatic liftingaxle control can easily be integrated

� Due to large valve diameters, pres-surizing and venting processes areaccelerated

� Easy operation and maximum safetyfor those operating the system due toone single control unit

� Highly flexible system due to the factthat electronics can be programmedvia operating parameters (trailingend programming)

� Clear-cut safety concept and diagno-stic facility.

With conventional air suspension sys-tems, the valve which measures theheight also controls the air bellows,where as ECAS achieves control bymeans of an electronic control unit(ECU) actuating the air bellows via sole-noid valves, using information receivedfrom sensors.

The ECU not only controls the normalheight of the vehicle, it also, via the re-mote control unit, permits control of theother functions which, in conventional airsuspension systems, require additionalvalves such as height adjustment valvesand height limiting valves.

Over that, a large number of additionalsystem functions are available

ECAS is adjustable to suit the differenttypes of trailer.

ECAS only works when the ignition isON. Power supply for the trailer is nor-mally provided via the ABS system. Con-necting the ABS system is alsonecessary to ensure that ECAS receivesthe so-called C3 signal, i.e. informationon the current speed of the vehicle.

To permit adjustment of the level of atrailer not connected to a towing vehicle,an optional facility for a storage batterymay be provided for an additional powersupply on the trailer.

ECAS -Electronically Controlled Air Suspension 6.

Introduction:

Example for operation in a semi-trailer without lifting axle

Basic system:1 ECU (Electronic Control Unit) 2 RCU (Remote Control Unit)3 Height Sensor4 Solenoid Valve5 Air Bellows

leve

l

116 1

ECAS - Electronically Controlled Air Suspension6.

Description of operationA Height Sensor (3) will continuouslymonitor the vehicle's height and send itsreadings to the ECU (1). In the event ofthe ECU finding that the normal level isnot being maintained, a Solenoid Valve(4) is activated in such a way that, bypressurizing or venting, the level is ad-justed accordingly.

Below a pre-defined speed (and whenvehicle is stationary), the RCU (2) can beused to change the index level (useful forloading-ramp operation, for example).

An indicator lamp (situated on the front ofthe trailer, and visible from the truck's cabthrough the rear-view mirror) is used tonotify the driver that the trailer is outsideits normal ride height and to inform aboutany faults the ECU may have discovered.

Circuit diagram of basic system:1 ECU (Electronic Control Unit) 2 RCU (Remote Control Unit)3 Height Sensor4 Solenoid Valve5 Air Bellows

ECAS electronic

diagnostics

Power Supply module ECAS

ABS Vario C

24N ISO 7638 24S

stop

ligh

t

spee

d si

gnal

grou

nd

Kl. 3

0 Kl

. 15

1171

ECAS-Electronic Control Unit (ECU)446 055 . . 0

The Electronic Control Unit (ECU)The Electronic Control Unit is the heart ofthe system and is connected with the in-dividual components on the motor vehi-cle by means of a 35-pole or 25-poleplug-in terminal. The ECU is located in-side the driver’s cab.

Together with a plug-in terminal for con-necting the ECAS ECU for trailer’s to theother components, the ECU is mountedon the trailer's chassis in a protectivehousing. This protective housing is simi-lar to that of the ABS VARIO-C system.The ECU can be used for implementinga large number of system configurations.The plug-in terminal has a connector forevery height sensor, pressure sensorand solenoid valve. Depending on thesystem used, parts of the terminal maynot be used.

As in the ABS system, the cables are fedthrough glands in the lower part of thehousing. To facilitate the allocation of theindividual cables to the plugs, bands aretaped around the cables.

OperationThe ECU contains a microprocessorwhich processes digital signals only. Amemory managing the data is connected

to this processor. The outlets to the sole-noid valves and to the indicator lamp areswitched via driver modules.

The ECU is responsible for– constantly monitoring the incoming

signals

– converting these signals into counts

– comparing these values (actual va-lues) to the values stored (index va-lues)

– computing the required controllingreaction in the event of any deviation

– actuating the solenoid valves

Furthermore, the ECU is responsi-ble for– managing and storing the various in-

dex values (normal levels, memory,etc.)

– data exchange with the RCU and theDiagnostic Controller

– regularly monitoring the function ofall system components

– monitoring the axle loads (in sy-stems with pressure sensors)

– plausibility testing of the signals re-ceived (for error detection)

– error recovery.

In order to ensure rapid control reactionto any changes in actual values, the mi-croprocessor processes a fixed programin cycles of some milli-seconds, with oneprogram cycle covering all of the abovetasks.

This program cannot be modified and isfixed in a program module (ROM). How-ever, it will use values stored in a freelyprogrammable memory. These values,the parameters, effect the computingprocesses and thus the ECU's control-ling reactions. They are used to commu-nicate to the computing program thecalibrating positions, the system configu-ration and the other preset values con-cerning the vehicle and functions.


ECU 35 pins

ECU 25 pinsECU for Trailer’s

ECU 35 pins

118 1

ECAS Solenoid Valve472 900 05 . 0

Valve for the axle with two height sensors

The solenoid valve shown in the illustra-tions below has three solenoids. One so-lenoid (6.1) controls a central breathervalve (also known as a central 3/2 direc-tional control valve), the others controlthe connection between the two air bel-lows (2/2 directional control valves) andthe central breather valve.

This valve can be used for establishingwhat is known as 2-point control in whichboth height sensors on both sides of theaxle separately control the level of bothsides of the vehicle so that the body iskept horizontal even when the load is notevenly distributed.

Design of the ValveSolenoid 6.1 actuates a pilot valve (1),and the actuating pressure from thisvalve flows through hole (2) and acts onpiston valve (3) of the breather valve.The pilot valve receives its pressure viaport 11 (supply) and connecting hole (4).

This drawing shows the breather valve inits venting position in which air fromchamber (5) can flow to port 3 via thehole of the piston valve.

As solenoid 6.1 is energized, pistonvalve (3) is pushed downwards, initiallycausing valve plate (6) to close the holeof the piston valve. The valve plate isthen pushed off its seat (hence the name'seat valve'), and supply pressure canflow into chamber (5).

The other two valves connect the air sus-pension bellows with chamber (5). De-pending on which solenoids (6.2 or 6.3)are energized, piston valves (9) or(10)are pressurized via holes (7) or (8),opening valve plates (11) and (12) toports 22 and 23.A solenoid valve for control of the otheraxle can be fitted to port 21.


Solenoid Valves Special solenoid valve blocks have beendeveloped for the ECAS system. Bycombining several solenoid valves inone compact block, both space and in-stallation time are kept to a minimum.

The solenoid valves are actuated by theECU as a control element; they convertthe voltage present into a pressurizing orventing process, i.e. they increase, re-duce or maintain the air volume in thebellows.

In order to achieve a large throughput ofair, pilot valves are used. The solenoidsinitially actuate those valves with a smallnominal width, and their control pressure

is then passed to the piston surfaces ofthe actual switching valves (NW 10 andNW 7 respectively).

Different types of solenoid valves areused, depending on the application: Forcontrolling a single axle, one seat valveis sufficient whilst a complex slidingvalve is required for controlling the liftingaxle.

Both types of solenoid valves are basedon a modular principle: Depending onthe application, the same housing isused to accommodate different parts ofvalves and solenoids.

119

This valve is similar to the valve de-scribed above but it contains fewer parts.

Since port 14 is connected to port 21 ofthe valve described above, no breathervalve is needed and only one pilot valve(1) is used. The piston valves (3) of bothair suspension bellows valves are pres-surized via two connecting holes (2) sothat each pressurizing or venting proc-ess is effected evenly for both bellowsvia chamber (5).

If the solenoid is not energized, thevalves are closed, as shown in the illus-tration. At this time, the only connectionbetween the bellows is the lateral choke(7), through which any difference in pres-sures can gradually be compensated.

The valve is connected to the air supplyvia port 12. This port is needed merely topermit the pilot valve to displace the pis-ton valve.


Valve for an axle with one height sensor

ECAS Solenoid Valve472 905 1 . . 0

Sliding valve with rear axle block and lifting axle block


Valve for the bus with a kneeling function


120

By means of the RCU the driver can in-fluence the vehicle's level within the per-missible maximum limits. However, thiscan only be done whilst the vehicle iseither stationary or has not exceeded thedriving speed parameter.

The control keys for changing the vehi-cle's level are accommodated in a handyhousing which is connected, via a coiledcable and a socket on the vehicle, withthe ECU.

There are different RCUs depending onthe type of system used. The above illus-tration shows a unit with the largest pos-

sible number of functions. The functionsof this RCU are:

– raising and lowering of the chassis

– setting normal level

– stop

– storage and actuation of two prefe-rence levels

– raising and lowering of the lifting ax-le, or unloading or loading the trai-ling axle

– switching automatic lifting axle ope-ration on and off.

ECAS Height Sensor441 050 0 . . 0

From the outside, the height sensorlooks similar to WABCO's conventionallevelling valve which means that it canoften be fitted in the same location on thevehicle frame (the pattern of the two up-per mounting bores is similar to that ofthe levelling valve).

The sensor housing contains a coil inwhich an armature is moved up anddown. Via a connecting rod, the arma-ture is connected to a cam on the lever's

shaft. The lever is connected to the vehi-cle axle.

As the distance between the superstruc-ture and the axle changes, the lever isturned, causing the armature to moveinto or out of the coil. This changes thecoil's inductance.

This inductance is being measured bythe electronic control unit at short inter-vals and converted into a height signal.


ECAS Remote Control Unit446 056 0 . . 0

446 056 0.. 0 446 056 1.. 0

121

The pressure sensor produces a voltageoutput which is proportional to the pres-sure present. The measuring range liesbetween 0 and 10 bar; a pressure of 16bar must not be exceeded.

The signal voltage is sent to the ECU viaa connecting plug. Furthermore, the sen-sor must receive a supply voltage fromthe ECU via a third conductor. The cableharness must be encased in a hose orsimilar material in such a way that thehousing - which is otherwise waterproof -can ”breathe“.

Under no circumstances should thepressure sensor be connected to theconnecting line between air suspensionbellows and solenoid valve since thiscould result in wrong readings whenpressurizing or venting is in progress.

If air suspension bellows with two thread-ed ports, as offered by renowned manu-facturers of air suspension systems,cannot be used, a special connectormust be fitted.

This connector can consist of a T-shaped pipe union, with a small pipe be-ing welded into its pressure sensor con-nection protruding into the inside of thebellows, thereby sensing the ”settled“bellows pressure (these fittings areavailable from WABCO).

A normal tee-piece can be used but onlywhen a high raise/lowering-speed is notrequired. Two examples:

– One axle is sensed (drawbar-trailerwith one LA). The feed pipe frombellows to solenoid should be small(nominal size ø 6) but the connec-tion between bellows and sensor lar-ge.

– Two axles are sensed (3-axle semi-trailer with one LA). Use ø 12 pipebetween the sensed bellows. Fit thepressure sensor in a tee piece nextto one bellows. The line from the so-lenoid valve should be ø 9) enteringthe system at the other bellows.

Pressure Sensor441 040 00 . 0


1231

7.

Clutch Servos

124 1

Clutch Servos7.Clutch Servo970 051 ... 0Modular Series

Purpose:To reduce the force required to pushdown the clutch pedal and to permit sen-sitive and accurate actuation of theclutch.

Design:The clutch servo consists of three parts:

– hydraulic slave cylinder

– control valve

– pneumatic servo cylinder.

Possible variants:

– trigger valve for transmission control

– optional feature for pressure sen-sors

– wear indicator.

Operation:The clutch servo is connected with the airreservoir for ancillary consumers via Port1, and with the pedal-operated hydraulicmaster cylinder via Port 1-4.

a) Clutch not engaged:During the declutching process, the airpressurized by the pedal-operated mas-ter cylinder is forced into Chambers Cand D through Port 1-4. This causes pis-

ton (a) to move to the left, closing the out-let (b) and opening the inlet (c). It thusallows the compressed air to pass fromPort 1 into Chamber A and from therethrough the duct (d) into Chamber B.Pneumatic and hydraulic pressures forcepiston (e) to the right, causing the clutchto disengage through the forcing lever (f).The air pressure in Chamber A balancesthe hydraulic pressure in Chamber D andthe control valve is in its neutral position.

b) Clutch engagedWhen the clutch is engaged once again,the oil from Chambers C and D returns tothe pedal-operated master cylinder. Pis-ton (a) returns to its original position onthe right, the inlet (c) closes and the pres-sure in Chambers B and A is evacuatedthrough the opening outlet (b) and Vent3.

The hydraulic and pneumatic pressuresat piston (e) fall, releasing the way backinto the engaged position. Through duct(g), the pressure in Chamber E can riseor fall.

The pressure in Chamber B remains pro-portional to the hydraulic pressure inChamber C at all times, thus giving thedriver full control when engaging theclutch.

If the air pressure is insufficient, it is pos-sible to declutch solely with the hydraulicpressure acting on piston (e). However,this requires greater force to be appliedto the clutch pedal.

The design of the modular series in-cludes automatic readjustment of theclutch, and some variants also have amechanical wear indicator.

For vehicles with Electronic Drive Con-trol (EAS), clutch servos from the 970051 4.. 0 series have a pressure sensorfitted.

EAS is a system which permits pulling ofand changing gear with standard aggre-gates without a clutch pedal having to beactuated. The driver can either changegear manually by actuating a master unitsimilar to EPS, or the process can be au-tomatic through the electronic controlunit.

1251

Clutch Servos

Purpose:To reduce the clutch pedal effort and toprovide a smooth and precise clutch op-eration.

Design:The clutch servo consists of two parts:

– a servo device: hydraulically control-led pneumatic control valve

– an actuating unit: differential cylinderunder hydraulic and pneumatic pres-sure which transmits force to theclutch mechanism.

Different modifications are possible:

– pneumatic valve with plunger (3 wayvalve),

– threaded port at the pneumatic ser-vo chamber,

– clutch wear warning device: electri-cal, mechanical or pneumatic,

– integral pneumatic pressure limitingdevice.

Operation:The clutch servo is connected to the aux-iliary reservoir via port 1, and via port 1-4to the pedal actuated hydraulic mastercylinder.

Clutch disengagement position:When disengaging the clutch, the oilforced by the pedal actuated clutch mas-ter cylinder enters through port 1-4 intochambers (C) and (D). Piston (a) movesto the right, closes outlet (b), opens inlet(c) allowing the compressed air from port1 to enter into chamber (A), and to flowthrough channel (g) into chamber (B).

Forced by the pneumatic pressure, pis-ton (f) moves to the right causing theclutch to disengage by means of a pushrod connected to the clutch actuating le-ver. The pneumatic pressure in chamber(A) balances the hydraulic force in cham-ber (D) closing inlet (c).

Clutch engagement position:When reengaging the clutch, the oil inchambers (C) and (D) is returned to the

pedal controlled clutch master cylinder.Piston (a) returns to the right, closes inlet(c), opens outlet (b) and allows the com-pressed air to be vented from chambers(A) and (B) to the atmosphere throughport 3. The hydraulic and pneumaticpressures on pistons (e and f) decrease,allowing them to return to the left, to theclutch engagement position. The airpressure partially returning throughchannel (d) compensates for the vacuumin chamber (E).

At all times, the pneumatic pressure inchamber (B) remains proportional to thehydraulic pressure in chamber (C) thusgiving the driver full control of the clutchengagement.

If there is insufficien't compressed air,clutch disengagement is still possiblewith the hydraulic pressure acting on pis-ton (e). However, this requires greaterpedal effort.

The spring behind piston (e) compen-sates for clutch friction wear.

7.Clutch Servo970 051 . . . 0Special Design

127

8.

Air Braking Systems InAgricultural Vehicles

128

Air Braking Systems In Agricultural Vehicles8.

Brief Description Of The Dif-ferent Air Braking SystemsIn the single-line braking system, a singleair line between the tractor and its traileris used to fill the air reservoirs on thetrailer while the vehicle is in motion, andas the trailer is braked the pressure inthat line is reduced.

In the twin-line braking system, there isone line each between the tractor and itstrailer, one for filling the trailer’s air reser-voirs and one for controlling the brakingprocess (by reducing the pressure). Thebenefit of such a system is that the sup-ply of compressed air on the trailer isalso being topped up during the brakingprocess.

In a combined single and twin-line brak-ing system, this system can use eitherthe principle of the single-line or the twin-line system. Towing vehicles with a sin-gle-line and a twin-line connection for thetrailer thus permit both trailers with a sin-gle-line or with a twin-line braking systemto be connected.

It is important to remember that thebrakes of a trailer with a single-line sys-tem cannot be operated if it is used be-

hind a tractor with a twin-line brakingsystem; the same also applies vice-ver-sa.

Benefits Of A Twin-Line Air Braking System� The operating pressure and thus the

additional braking force can be sensi-tively graded. The same also appliesto long downhill gradients.

� Because of its adjustable predomi-nance on the relay emergency valve,the tractor-trailer combinationremains stretched-out and the trailerdoes not run up to its tractor.

� Less wear on the tractor’s brakes andthus longer life and lower mainte-nance cost.

� Any slight leakage does not effect theperformance. The compressor al-ways supplies sufficient compressedair for the braking system, also duringthe braking process.

� Unintentional disconnection of thetrailer from the tractor causes the trai-ler to be braked automatically (brea-kaway brake).

� High level of safety and enhancedride comfort. The jerking commonwith trailers which have had overrunbrakes fitted is prevented.

� It is not possible to mismatch hosecouplings due to the built-in mis-match-safeguard.

� Non-polluting because the medium,air, can be emitted directly to at-mosphere.

� Easy and simple to retrofit the air bra-king system.

Design of the Air Braking SystemThe air braking system shown in the illus-tration is a high pressure braking system(HPR) whose pressure level is controlledby an unloader valve (2). This supplypressure of 14 bar is limited to 7.3 bar bythe pressure limiting valve (4) locateddownstream from the air reservoir, thusin effect achieving a normal pressurebraking system (NPR). The trailer's brak-ing system (in this illustration it is a dualline braking system) is actuated by themaster cylinder (7) via an air/hydraulicdual line trailer control valve (8).

129

Air Braking Systems In AgriculturalVehicles 8.

Operation:Driving PositionThe compressed air from the compres-sor (1) flows via the unloader valve (2)which automatically controls the operat-ing pressure of the tractor's air compres-sion system, into the air reservoir (3).The supply pressure reading is shown onthe pressure gauge (5).

From the air reservoir (3), the air flowsvia the pressure limiting valve (4), set to7.3 bar, to the dual line trailer controlvalve (8), the 3/2 way valve (6), the sin-gle line trailer control valve (9) and on tothe supply hose coupling. In the trailercontrol valve (9), the pressure is limitedto 5.3 bar which reaches the hose cou-pling (11) (single line).

If a dual line trailer is attached, the supplypressure of 7.3 bar flows via the hosecouplings (10) to the trailer passing theline filter (15), the relay emergency valve(16) and finally the air reservoir (22).

To supply a second trailer with com-pressed air, two additional hose cou-plings (23 and 24) have been providedon the trailer. These are connected to thesupply and pilot lines downstream fromthe relay emergency valve (16).

Braking PositionWhen the brake pedals are actuated, the3/2 way valve (6) is opened and the trail-er control valve (8) receives the supplypressure of 7.3 bar.

This causes a small amount of pressureto reach the relay emergency valve (16)through the pilot line, actuating it. Thetrailer’s air supply now flows from the airreservoir (22) through the relay emer-gency valve, the adapter valve (17) andthe load-sensing valve (18) to the brakecylinders (20) on the front axle, andthrough the pressure limiting valve (19)and the load-sensing valve (18) to thebrake cylinders on the rear axle.

When the brake pedal is pushed downfurther, pressure is built up in the hydrau-lic master cylinder (7) which increasesthe actuating pressure at the trailer con-trol valve (8). Depending on the level ofhydraulic pressure, the trailer controlvalve (8) also builds up the pressure inthe pilot line leading to the relay emer-gency valve (16) and, through the load-sensing valves (18), transmitted to thebrake cylinders as a ratio of the load car-ried.

When the hydraulic braking pressure inthe tractor's braking system has been re-

duced, the air pressure in the pilot lineleading to the relay emergency valvealso falls, causing the pressure in thebrake chambers (20) to be reduced viathe adjusting valve and the load sensingvalves. The passage in the 3/2 way valveis closed once again, and the supplypressure of 5.3 bar (single line) begins tobuild up in the line between the trailercontrol valve (9) and the hose coupling(11).

130 1


Purpose:Limitation of output pressure.

Operation:Compressed air directed into chamber Athrough high-pressure port 1 flowsthrough inlet (j) and chamber B to low-pressure port 2. Pressure is thereby alsobrought to bear via hole (c) on diaphragmpiston (b), which is initially retained in itslower position by compression spring (a).

When pressure in chamber B reachesthe level to which the low-pressure sideis adjusted, diaphragm piston (b) over-comes the force of spring (a) and movesupwards with spring-loaded valve (i),thus closing inlet (j).

If pressure in chamber B rises above theset level, diaphragm piston (b) movesfurther upwards and is thereby lifted offvalve (i). Excess compressed air es-capes to atmosphere through hole (h) ofvalve (i) and exhaust 3.

If pressure starts to drop in the low-pres-sure line, this relieves diaphragm piston(b) of pressure so that it moves down-wards and pushes valve (i) open until asufficient quantity of compressed air hasbeen supplied through inlet (j).

Should the pressure in the high-pressureline rise above the maximum permittedlevel, safety valve (g) opens against theforce of compression spring (f) and al-

lows the excess compressed air to es-cape to atmosphere through hole (e) anddust cover (d). Pressure in the low-pres-sure line is not affected by this process.

The pressure existing in the low-pres-sure line is fully retained when the high-pressure line is evacuated.

The line at low-pressure port 2 can beevacuated only through equipment con-nected on that side.

Pressure Limiting Valve973 503 . . . 0

Compressed Air Generating System:

normal pressure - combined sin-gle line and dual line system hy-draulically actuated

Legend:1 Compressor2 Combined Unloader3 Air Reservoir 20 l4 Drain Valve5 Pressure Gauge7 Trailer Control Valve, single line8 Hose Coupling, supply line9 Hose Coupling, control line

10 Hose Coupling, single line11 Trailer Control Valve12 3/2-Directional Control Valve13 Master Cylinder

1311


3/2-Directional Control Valve563 020 . . . 0

Purpose:To alternately control the pilot line withthe supply line or the exhaust upon actu-ation of the brake.

Operation:When the tractor's brake pedals are ac-tuated, Piston (a) is forced to its upperposition by the spring force. The com-pressed air from the supply line at PortP2 now reaches Port A and from there

the downstream trailer control valve.This causes a brake pressure to be out-put for the trailer even before the hydrau-lic tractor brake becomes effective.

When the tractor's brake is released,Piston (a) is pushed downward onceagain by the brake pedal and the pas-sage is closed. The compressed air fromthe pilot line is now reduced via theopened passage to Port R2.

Shut-Off Cock452 002 . . . 0 and952 002 . . . 0

Purpose:To shut off an air line and vent the downstream line.

Operation:When the lever (a) is parallel to the lon-gitudinal axis of the stop cock the eccen-tric shaft (c) pushes valve (d) to the leftagainst the spring (e). Air passes unre-stricted from port 1 through the inlet (f) to

the line leading from port 2. If the lever(a) is turned through 90 degrees to itsstop, the spring (e) moves valve (d) tothe right and the inlet (f) is closed. Theline leading from port 2 is vented throughthe exhaust drilling (b).

132 1


Purpose:To control the dual line braking system ofthe trailer in connection with the trailer'shydraulic master brake cylinder or its hy-draulic transmitter.

Variant 252 provides for additional pneu-matic actuation, causing trailer brakepressure to be activated ven before thetractor's brake becomes effective.

Operation:In the release position, CompressionSpring (e) pushes Valve Sleeve (d) ontoInlet (c), keeping it closed. Port 2 is con-nected with Exhaust 3 via Outlet (b).

When the brake pedal is depressed, thehydraulic control pressure will act on Pis-ton (h) via Port 4, displacing that piston,together with Graduating Piston (a), tothe right. Outlet (b) is closed, Inlet (c)opens and the compressed air present atPort 1 flows to the relay emergency valvevia Port 2. The compressed air acting onGraduating Piston (a) moves it to the leftagainst the hydraulic control pressure,and Inlet (c) is closed. A final positionhas now been reached.

Some dual circuit Variants is also fittedwith an additional pneumatic controlport. This permits an upstream 3/2-way

valve to pressurize Port 42 and thusChamber A with an actuating pressure of7.3 bar when the brake pedal is de-pressed. Piston (a) closes Outlet (b),opening Inlet (c). Thus a small amount ofactuating pressure reaches the relayemergency valve via Port 2 before actu-ating pressure builds up at Port 4.

Any increase in the hydraulic actuatingpressure will also cause the pressure atPort 2 to be increased. As the brake ped-al is released, Ports 4 and 42 will be de-pressurized, causing the pressure inPort 2 to return Graduating Piston (a) toits original position. Outlet (b) opens, andPort 2 is vented via Exhaust 3.

The Trailer Control Valve also has aHand Brake Lever (f) which, as the handbrake is actuated, will push Piston (a)against Valve Sleeve (d), thus openingInlet (c), causing full braking of the trailer.

Trailer Control Valvefor dual line trailer braking systems470 015 . . . 0

1331

Purpose:To control the single or dual line brakingsystem of the trailer in connection withthe trailer's hydraulic master brake cylin-der or its hydraulic transmitter.

Operation:In the valve's release position, Compres-sion Spring (e) pushes Valve Sleeve (d)onto Inlet (c). The air supplied via Port 1flows via Hole A into Chamber B, raisingPiston (h) which takes with it Piston (k)and Valve (i). Inlet (l) is opened, permit-ting the air supplied to flow via Port Z intothe trailer's (single) control line. Whenthe forces of Pistons (h and k) are bal-anced, Inlet (l) is closed and the pressureat Port Z is limited to 5.2 bar. Port 2 isvented via Outlet (b) and Exhaust 31.

When the brake pedal is depressed, thehydraulic control pressure will act on Pis-ton (m) via Port 4, displacing that piston,together with Graduating Piston (a), tothe right. Outlet (b) is closed, Inlet (c)opens and the compressed air can nowflow via Port 2 to the control line trailer'sdual line braking system. The com-pressed air acting on Graduating Piston(a) moves it against the hydraulic controlpressure, and Inlet (c) is closed. A finalposition has now been reached. At thesame time, the pressurized Piston (h) ispushed downwards. Outlet (j) is opened,

and Port Z is partially vented via Exhaust32. A final braking position has beenreached when the force in Chamber Bacting on the underside of Piston (h) isgreater than the force acting on the top ofPistons (h and k). Piston (h) is raised toa point where Outlet (j) and Inlet (l) areclosed.

When the brake pedal is released, Port 4is depressurized, causing the pressurein Port 2 to return Graduating Piston (a)to its original position, opening Outlet (b).Port 2 is vented via Exhaust 31. At thesame time, the pressure acting on thetop of Piston (h) is reduced and the sup-ply pressure in Chamber B pushes it toits top end position. Via opened Inlet (l),Port Z is once again pressurized up to5.2 bar.

The Trailer Control Valve also has aHand Brake Lever (f) which, as the handbrake is actuated, will push Piston (a)against Valve Sleeve (d), thus openingInlet (c), causing full braking of the trailer.


Trailer Control Valvefor single or dual line trailer braking systems470 015 5 . . 0

134 1

Trailer Control Valvewith pressure control471 200 . . . 0

Purpose:To control the single line air braking sys-tem of the trailer in combination with thetrailer control valve attached to the footbrake lever for the tractor's dual line trail-er braking system and for limiting theoutput pressure to 5.2 bar.

Operation:In the release position, CompressionSpring (a) will hold Diaphragm Pistonwith Valve Sleeve (c) in its lower end po-sition. Outlet (d) is closed and Inlet (e)open. The compressed air from the trac-tor's air reseervoir flows via Port 1 to Port2 and reaches the relay emergencyvalve via the hose couplings. At thesame time, the compressed air flows, viaHole C, into Chamber D below Piston(h), and via Hole A into Chamber Eabove Piston (h). As soon as the pres-sure in Chamber B and in the line to thetrailer has reached 5.2 bar, Valve (g) isforced downwards against the force ofCompression Spring (f) until Inlet (e) isclosed.

When the tractor's foot brake is actuated,the output pressure from the trailer con-trol valve which is affixed to the footbrake lever for the dual line trailer brak-ing system will, via Port 4, reach Cham-ber F where a pressure will now build upbelow the Cup Collar which forces Dia-phragm Piston (b) with Valve Sleeve (c)upwards against the force of Compres-

sion Spring (a). Outlet (d) opens.Through Valve Speeve (c) and ExhaustHole 3, sufficient air will now be emittedto atmosphere to achieve the abruüt re-duction in pressure required for ad-vanced retardation of the trailer.

At the same time, the pressure in Cham-ber D will fall and Piston (h) is forceddownwards by the supply pressure inChamber E acting on its upper portion. Ittakes with it Valve Sleeve (c) which inturn closes Outlet (d) as it settles on thedouble cone valve.

As described above, the increased brak-ing effect of the tractor causes the pres-sure of the trailer's control line to befurther reduced whilst the advanced re-tardation of the trailer is maintained.When the tractor brake is released, thepressure in Chamber F is reduced onceagain, causing Diaphragm Piston (b) andValve Sleeve (c) being forced down-wards through the force of CompressionSpring (a). Inlet (e) opens and the supplyair present at Port 1 flows to the trailer'scontrol line via Port 2.


1351

Purpose:To control the braking forces of the trail-er’s brake cylinders as a ratio of the loadsetting.

Operation:When the brakes are applied, the pres-sure from the flanged relay emergencyvalve arriving at Port 1 flows into Cham-ber A and through the opened inlet (d)and Chamber B to Port 2 and thus to thetrailer’s brake cylinders. At the sametime, pressure is applied to the piston (e)which is initially being held in its upperend position by the spring (f). The forceof the spring (f) is dependent on the posi-tion of the lever (g) - together with thecam (j) - which is either ‘empty’, ‘halfload, or ‘full load (or even ‘1/4 load’ or ‘¾load’, on some vehicles). As soon as thecontrol pressure in the cylinders and onthe piston (e) corresponding to the loadsetting has been reached, the piston (e),together with valve (c) and spring-loadedvalve (a) will slide downwards, closing in-lets (b and d). This prevents the pressurein the cylinders from rising further.

In the event of any leakages in the trail-er’s braking system, the drop in pressurewill cause valve (a) to be raised by thepiston (e). Inlet (b) opens and more com-pressed air is supplied accordingly.

When the tractor’s brakes are released,Port 1 and Chamber A become pressure-

less. The higher pressure in Chamber Braises valve (c) and with valve(a). Inlet(d) opens and the brake cylinders areevacuated through Port 1 and the relayemergency valve. The reduction in thepressure acting on piston (e) causes thatpiston to be returned to its upper end po-sition by the spring (f).

The ‘release’ position which a number ofvariants of this load apportioning valvehave is used to release the brake whenno trailer is attached. To achieve this, theshape of the cam (j) relaxes the spring (f)to the point where piston (e) movesdownward, opening the outlet of thevalve (a). The compressed air from thebrake cylinders can escape to atmos-phere through the axial hole in piston (e)and Vent 3.

The adjuster screw (i) is used to adjustthe pressure reaching the cylinders fromthe load apportioning valve in the ‘empty’position. When the lever of the load ap-portioning valve is in its ‘full load’ posi-tion, that screw is accessible afterremoving the cap in Vent 3 and permitsthe initial tension of the spring (f) to beadjusted. Unscrewing the screw (i) caus-es the pressure in the cylinders to be in-creased, screwing it in causes thatpressure to be reduced. The pressurecan be similarly adjusted for the ‘halfload’ position. To do this, the ‘release’position is selected, and the adjustment

is achieved by turning screw (h). On loadapportioning valves which do not have a‘release’ position, screw (h) is reachedby selecting the ‘empty’ position and un-screwing the screw on the side of thebottom housing (this screw being foundonly on those variants).

When turning the screws (h or i), the loadapportioning valve must always be pres-sureless.


Load Apportioning Valve475 604 . . . 0

1371

9.

ETS and MTS - Electronic DoorControl System For Motor Coaches

138 1

System Design of ETS

ETS - Electronic Door Control System For Motor Coaches9.

Introduction Due to more stringent safety regulations,the motor buses of urban public transportand the motor coaches of private opera-tors in Germany have had to have safetycontrols fitted since the early eighties toprotect their passengers and to reducethe hazard of accidents in workshops.The two major criteria which have had tobe met since then are:

� features for opening and closingdoors to protect both persons andobjects

� features for the prevention of sud-den door movements after re-pres-surizing of cylinders.

Although these demands focusing on im-provements in technical safety were metby the introduction of the two WABCOsystems, following the pressureless andthe pressure-reduced principle, it verysoon turned out that - in terms of thenumber of appliances fitted and ease ofmaintenance - there was still room forfurther improvements.

This caused WABCO to develop an elec-tronically controlled system which fullytakes into account the following key re-quirements:

– safety for passengers

– reduction of the safety hazard in theworkshop

– easy to use by workshop staff

– reduction of system cost

– no service or maintenance required.

The development, focusing on these de-mands, resulted in the Electronic DoorControl System which has been pro-duced since late 1987 and is known bythe abbreviation

* E T S *The most important improvements whichhave been achieved are as follows:

– elimination of the limit and drum-type switches

– no more adjustment work to be doneby the vehicle manufacturer ortransport company

– development of a standard systemaccepted by all bus manufacturersin terms of their respective safetypolicies

– use of ETS in combination with sim-ple, time-tested pneumatic actuati-ons

– reduction of jamming forces.

Pneumatic ControlCompared with the pressureless and thepressure-reduced circuits, the use ofETS achieves a considerable reductionin the number of components fitted. Theyare replaced by a single door valvewhich has two key attributes:

� increasing and decreasing thepressure in the cylinder chambers(4/2 function = ordinary door ope-ration)

� reducing door slamming after re-pressurizing the cylinders followingthe actuation of the emergencycock. The door continues to be‘powerless’ after this process. Thedoor leaves can be moved by handto prevent any hazard to passen-gers.

139

ETS - Electronic Door Control SystemFor Motor Coaches 9.

Fig. 1

emergency cock

door valve

dynamic pressure switch displacement transducer

Fig. 1Example for an ETS system with rota-ry drive

The layout of an ETS door control systemshown above illustrates how the variousdoor components are connected. Thisexample shows a system with a rotarydrive, i. e. the door operating cylinder ismounted directly to the rotary pillar of thedoor leaf.

In this example, the door is monitored bya dynamic pressure switch in addition tothe displacement transducer. The dy-namic pressure switch is actuated by apressure pulse from the rubber seal ofthe main front edge. The ETS ECU has aseparate inlet for this function.

Fig. 2ETS system with linear door drive

.

This diagram shows the pneumatic con-nection with a linear cylinder drive. Theelectrical circuit is identical to that of therotary drive.

In both types of drive, the opening and

closing speeds of the door leaves can beadjusted by means of suitable throttlesor panels. For details on such adjust-ments, please refer to the vehicle docu-ments provided by the vehiclemanufacturer.

Fig. 2

140


Electronic ControlElectrical control is achieved by an elec-tronic control unit with a micro-controllerinside. It is available in two basic ver-sions:

– actuation control by the driver only

– automatic system for automatic dooractuation.

Both types of ECU contain identical com-puter programmes. Adjustment to the

various functions is made by means of aspecial programming process. The typeof ECU can be identified by the plug-inconnectors:

The ordinary control unit has a 25-poleterminal, as does the automatic controlunit which, however, also has a 15-polesocket for the automatic functions and atwo-way (manual-automatic) switch.

ETS - ECU446 020 . . . 0

4/2-Way Cock(Emergency Cock)952 003 . . . 0

Purpose:The emergency cock is needed to evac-uate the air in the door operating cylin-ders in a hazard situation, for thepurpose of repairs, or if the door operat-ing system has failed to permit the doorleaves to be moved by hand. At thesame time, it actuates the door valve insuch a way that when the door operatingsystem is pressurized once more, thedoor operating cylinders are rendered‘powerless’. Variant 952 003 031 0 of thisemergency cock has a switch for actuat-ing a warning facility.

Operation:In the normal position of the T-handle(a), compressed air from the supply lineflows through Port 1, through the 4/2-way cock and on through Ports 2 into theoperating lines.

By turning the handle (a) through 90° intothe emergency position, the supply lineis cut off and the operating lines areevacuated through Port 3.

normal position emergency position

1411


Purpose:In normal operation, the door valve actslike a 4/2-way valve and is used to alter-nately pressurize the chambers of thedoor operating cylinders. Unlike oldersystems, the door of the vehicle - if itmakes contact with an obstacle whileopening - becomes ‘powerless’ whichmeans that the door valve simultaneous-ly pressurizes all chambers of the cylin-der, causing the door to stop. Thisprevents people getting jammed, and thedoor leaves can be pushed by hand.

Operation:Opening And Closing of DoorsTo switch the door valve to ‘open’, a but-ton on the dashboard has to be pushed.This causes the ECU (outlet PIN 15) toclose the electric circuit to Solenoid A ofthe door valve, and the armature movesupward. The compressed air in hole (b)flows into chamber (c), acting on piston(a) which is forced to the right, also push-ing piston (f) into its end position on theright. In this position, Port 11 (energysupply) is connected with Port 21/22 andthe compressed air flows through thedoor valve into the opening chamber ofthe door operating cylinders. Since Port23/24 is connected with Vent 3, the doorsopen.

When the driver pushes the door buttonon the dashboard once more, the doorvalve is reversed into the ‘close’ positionby energizing Solenoid B (piston (f)moves piston (a) into its left end posi-tion). The closing chambers of the door

operating cylinders are pressurized, orthe opening chambers are evacuated.The doors close.

Jamming Protection: Reversal WhenClosing the DoorIf a person or an object gets jammed be-tween the main front edges of the doors,the motion of the door is impeded. Viathe electronic displacement transducer(potentiometer), this impediment is de-tected and processed in the electronics.The door’s electronics now reverse thedoor valve to its opening direction andthe doors are opened by the reversalprocess. After the driver has againpushed the button on the dashboard,thus providing another switching pulse,the door cylinders are pressurized intheir closing direction and the doors willclose.

Jamming Protection: Reversal WhenOpening the DoorIn order to comply with the guidelines forautomatic doors and for doors on motorcoaches actuated by the driver, the con-struction must be such to ensure thatpassengers who are located within thedoor area on the vehicle cannot getjammed as the doors open.

For this purpose, Solenoid C of the doorvalve is used, together with the electronicdisplacement transducers. If a person oran object is jammed by the back edge ofthe opening door, this impediment is per-ceived by the electronic displacementtransducer and processed by the elec-tronics. Solenoid C of the door valve is

energized. The valve reverses and pres-surizes chamber (g); both pistons (a andf) are in their end positions and bothsides of the door operating cylinders arepressurized through Ports 21/22 and 23/24. This causes the door operating cylin-ders to be virtually ‘powerless’. The doorleaves are brought to a stop and can bemoved by hand.

In this context it is important to know that- due to the difference in the surfaces ofthe pistons of the door operating cylinder- the door leaves slowly move to theiropen position when the obstacle hasbeen removed. However, the door cannow be closed at any time when the driv-er pushes the button on the dashboard.

Actuation of Emergency CockWhen the emergency cock is actuated,the door valve is actuated pneumaticallythrough Port 4. The door operating sys-tem is evacuated via the emergencycock. The door operating cylinders arepressureless, so that the door does notmove and can be opened manually. If thedoor is to be operated once again it issufficient to return the emergency cock toits normal position. Through the doorvalve (pneumatically operated via Port 4)all chambers of the door operating cylin-ders are pressurized - as described un-der ‘Jamming Protection: ReversalWhen Opening the Door’. The driver canthen close the door again by pushing thebutton on the dashboard.

4/3-Way Solenoid Valve(Door Valve)372 060 . . . 0

142 1


Door Operating Cylinderfor single-phase closing motions with damping on both sides422 802 . . . 0

Purpose:To open and close hinged and foldingdoors.

Operation:When the door valve is actuated, thecompressed air flows through Port 12into Chamber A. The pressure buildingup there forces the piston (c) and thepressure bar (d) to the right, opening thehinged door. At the same time, ChamberB is evacuated through Port 11 and theupstream door valve.

When the door valve is actuated onceagain, Chamber B is pressurizedthrough Port 11 and the pressure inChamber A is reduced through Port 12.The alternating increase in pressure onthe piston (c) forces it, together with thepressure bar (d), back to the left, and thehinged door closes.

The speed of the opening and closingprocess can be adjusted by means of thethrottle screws (a and f). To preventheavy and noisy impact of the door as itopens or closes, the door operating cyl-inder has two additional throttles (b ande) which achieve a buffering effect (slow-ing the motion towards the end).

The compressed air displaced by thefront end of the piston (c) in the door’sopening motion initially escapes evenlythrough throttle (f) and Port 11. However,approx. 40 mm before the end of thestroke has been reached it has to passthe buffer throttle (e) since the reinforcedpart of the pressure bar (d) protrudinginto the radial seal (g) prevents a furtherevacuation of Chamber B through throt-tle (f). The buffer effect for the closingdoor is achieved in a similar manner. Thecompressed air initially escaping evenlyfrom Chamber A through throttle (a) andPort 12 is forced past buffer throttle (b)approx. 40 mm before the end of thestroke.

The door operating cylinder has beendesigned in such a way that by switchingover the lines from the door valve endingat Ports 11 and 12, the motions are re-versed. The door will then open when thepiston rod is retracted, and close whenthe piston rod is extended.

1431


Door Cylinderfor single phase closing mo-tion with damping when pis-ton rod extends or retracts422 808 . . . 0

Purpose:To open and close slide glide and bifolddoors for buses. Application is specifical-ly for doors equipped with reverse con-trol system.

Operation:Upon activating the door valve, com-pressed air flows via port 12 into cham-ber (A). The pressure build up movespiston (a) as well as piston rod (b) to theright thereby opening the attached door.Simultaneously, chamber (B) is ventedvia port 11 and the subsequent solenoiddoor valve. At the same time, the twoports of the reverse switch, which areconnected to ports 41 and 42, are pres-surized or vented.

Reactivating the door valve, pressurizeschamber (B) via port 11, and chamber(A) pressure decreases via port 12. Dueto the pressure differences acting uponpiston (a), piston (a) and piston rod (b)move this time to the left and close theattached door. Also the reverse controlswitch is pressurized or vented as in thedoor opening process.

The door cylinder is equipped with an ad-justable throttle (d) which produces con-siderable damping as the piston rodnears the end of its motion preventingthe attached door from slamming.

Fig. A with damping as the piston rodapproaches full extension:During the initial phase of door opening,displaced air escapes unhindered viabore (C), however, at approximately 40mm before the end of the stroke, the wid-er diameter segment of the piston rodpenetrates the radial seal, preventingfurther venting of chamber (B) via bore(C), instead forcing air to vent throughthe damping throttle, which is adjustableby set screw (d).

Fig. B with damping as the piston rodapproaches full retraction:Approximately 40 mm before the end ofthe stroke, the inner bore of piston rod(b) surrounds and seals tube (e), nowforcing compressed air in chamber (A) tovent through throttle (d), which is adjust-able by set screw (d).

Fig. A

Fig. B

144 1


Pressure Switch441 014 . . . 0

The pressure switch is used to switchsolenoid valves or indicator lamps offand on. Correspondingly, there is an on-switch and an off-switch.

The switch position is dependent uponthe detail function of the facility to be

controlled. The pressure switch is not ad-justable within the respective series.

For purpose and operation, please referto Page 99.

Displacement Transducer446 020 4 . . 0

The displacement transducer (sensor)is a displacement-controlled potentiome-ter. In the opening process, the voltagerises from approx. 0.9 volts to approx.14 volts whilst in the closing process itfalls from approx. 14 volts to approx.0.9 volts. These voltage variations are

detected and processed by the door’selectronics. If the door hits an obstacleas it opens or closes, the electronics per-ceive this immediately and actuate thedoor valve 372 060 ... 0 accordingly.

145

MTS - Modular Door ControlFor Motor Coaches 9.

1

System MTS:

MTS was developed and first used in1997 based on the experience acquiredwith ETS. The special feature of this sys-tem is that it can be used with any doormodel. Inward swivelling doors, outwardswinging doors and swivel sliding doorswith pneumatic or electrical drive can becombined with one another without prob-lems!

Another innovation is also the connec-tion to the vehicle electric unit. Here, it ispossible to use a CAN data bus. There-fore, only two lines are required to controlup to 5 motor coach doors.

For vehicles without a central data bus,conventional cabling can be used as analternative. However, contrary to othersystems, the lines must only be connect-ed to the electronic control unit of the firstdoor.

Whether you are using a CAN or conven-tional cabling, the individual doors mustbe connected via the system CAN bus

and signal processing is centralised inthe control unit on the first door. Thisalso enables you to avoid the complicat-ed relay interconnections inherent in tra-ditional control.

Many parameters can be set in the soft-ware, in order to easily adapt control tospecific customer requirements. For allvehicle doors this data is stored on thecontrol unit of the first door. This way,the electronic control units on all the oth-er doors can be changed without takingthe parameters into account.

Naturally, the MTS system can perform adiagnosis: diagnosis takes place via thevehicle CAN bus or via a separate “K“line, regardless of the type of connectionused.

If Pneumatic doors are used, they aremonitored via pressure switches andnewly developed potentiometers whichare fitted directly on the heel post. Dueto mechanical coding, these sensors donot require any settings. Electrically driv-en doors can equally be monitored with

the help of these potentiometers; alter-natively, pulse generators installed in theengine can be used together with an in-dex switch.

A simple start-up program is used to bal-ance all the tolerances while using eachdoor for the first time. For this you onlyneed to move the doors once to the twostop positions by pressing the workshoppush buttons continuously.

The well-proven ETS principle was de-veloped for pneumatically driven doors.As a result, the damping mechanism in-tegrated into the cylinders is no longernecessary. This function is now per-formed by the door control valve. Sinceit is electronically controlled, damping ispossible at any moment. Apart from thecost-related advantages, this also resultsin much more flexible adaptability to themovement of the different doors. Thisalso prevents misadjustments, therebyincreasing operational safety.

MTS system principle:

Connection to a vehicle with CAN data bus

Connection to a vehicle with conventional cabling

Vehicle data bus

System data bus

Basic module

Extension module

Extension module

Door signals

Door drive

Door signals

Door drive

Door signals

Door driveSafety

devicesSafety devices

Safety devices

Door 1 Door 2 Door “n“

System data bus

Basic module

Extension module

Extension module

Door signals

Door drive

Door signals

Door drive

Door signals

Door driveSafety

devicesSafety devices

Safety devices

Door 1 Door 2 Door “n“

Conventional lines

Diagnosis K-Line

146

MTS - Modular Door Control For Motor Coaches9.

1

Principle of a 2-wing pneumatic door

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147


1

MTS electronic control unit 446 190 . . . 0

MTS electronic control units have 60PINs, divided into 5 different 3-seriesplugs (6, 9, 12, 15 and 18 PINs), whichmakes confusion impossible. Specialcare was taken to combine functionalgroups as much as possible, and toavoid double pinning.

9-pin: CAN data bus interfaces ofthe vehicle and system bus,diagnosis interface, addressinputs

18-pin:* power supply, drive (valvesand/or engines), sensoranalysis

15-pin: door-specific functions, e.g.workshop push button, feel-ing wing edge, ramp, en-trance lighting, automaticfunctions, etc.

12-pin:* used only on door 1 for con-ventional connection, for in-stance, of driver's pushbut-tons, fault indication light,halt brake, red/green indica-tor, etc., if no CAN vehicledata bus is available.

6-pin:* used only on door 1 for con-ventional connection (most-ly) of automatic functions, forinstance door release, babycarriage function, stop re-quest output, etc. if no CAN

vehicle data bus is available.It is also possible here toconnect a driver's pushbut-ton for door 3 (not allowed byGermany lt. § 35e of StVZO!)

There are differences on the plug side,between pneumatic door controls andelectronic door controls, especially withregard to the composition of the 18-pinplug. For MTS-P, 1 or 2 door control valves, 1or 2 position sensors and 2 or 4 pressureswitches are connected, depending onthe number of door wings and/or the re-quired function. For MTS-E, 1 or 2 engines with 2-chan-nel incremental indicators and the corre-sponding limit switches or analogueposition sensors can be connected ac-cordingly. The power supply connectionand speed signal connection are identi-cal (only on door 1).

*): For pneumatic doors, an under-equipped MTS variant (“extensionmodule“) is available for use only ondoor 2. The 6-pin and 12-pin plughave no function here. The extension module can only con-trol one door control valve

MTS door sensor 446 190 15 . 0

148

MTS - Modular Door Control For Motor Coaches9.

1

4/3 solenoid valve (MTS door control valve) 472 600 . . . 0

A switch-selected exhaust air throttlewas added to the MTS valve in additionto the functions described on page 141(door control valve). Since the cylinders are controlled by theelectronic control unit, they are brakedbefore reaching the respective end posi-tions.

Door operating cylinder exhaustiontakes place without restriction if sole-noids A, B, and C are idle, since pres-sure is exerted on the diaphragm (g).

An additional solenoid C is actuated bythe electronic control unit to brake thedoor operating cylinder, depending onthe direction of movement (one of the ex-ternal solenoids A or B is activated). Airis supplied to the chamber (h), exertspressure on the diaphragm (g) and thelatter closes the passage to exhaust 3.Now, exhaust air from the door operatingcylinder can only escape into the atmos-phere via the adjustable throttle.

MTS - door operating cylinder 422 812 . . . 0

The compressed air expelled from thedoor control valve flows through port 12into the cylinder and moves the piston tothe right. Pressure is reduced at thesame time from chamber B via port 11and the connected door control valve.

If the door control valve is activatedagain, chamber B is pressurized via port

11 and the pressure in chamber A is re-duced via port 12. Due to the changingpiston pressurisation, the piston movesback to the left together with the push rodand the linked door closes.

149


1

MTS emergency cock with switch 952 003 . . . 0

In normal position, air supply flowsthrough port 1 via the cock and entersthe door control valve through port 2.Port 4 is connected to exhaust (port 3).

If the emergency cock is moved 90° tothe emergency position, air supply thenflows to port 4 and the downstream doorcontrol valve is pneumatically switchedto “powerless function“ (pressure is re-duced from both door operating cylindersides).

At the same time, the electronic controlunit receives an emergency cock activa-tion signal via the integrated switch.

To prevent the door wings from movingsuddenly after emergency cock reset,the door control valve always pressuris-es both cylinder sides simultaneously af-ter a “powerless function“.

1511

10.

Installation Of Pipes AndScrew Unions

152 1

Installation Of Pipes And Screw Unions10.The dimensions and versions of the butt-joint couplings are mainly based on DINstandards 74 313 to 74 319.Push-in couplings correspond mainly toDIN standard 2353. Butt-joint couplingsare approved for use up to a pressure of10 bar, push-in couplings up to a pres-sure of 100 bar.

Steel couplings are used for steel andnylon pipes. The surface of adaptors andnuts are bonderized and oiled or brightgalvanized and yellow passivated.

For copper pipes, brass couplings areavailable.

General Informations

Push in couplings are used for the follow-ing pipe diameters:

Consisting of the following parts:

1 Connector with internal taper2 Cutting ring3 Pipe nut

Butt joint couplings are used for the fol-lowing pipe diameters:


1 Connector2 Sealing washer (internal)3 Thrust ring4 Cutting ring5 Pipe nut

The function of the cutting ring is thesame in both kinds of couplings. Whenthe pipe nut is tightened, the cutting ringis compressed by the internal taper of theconnector and cuts into the outer wall ofthe pipe to create a collar and form asealed joint. The additional thrust ring inbutt-joint couplings is sealed with a seal-ing washer normally made of fiber, or ofzinc in couplings exposed to high tem-peratures.

Important:Before fitting the coupling, check thethread for damage. Any damagedthreads must be reworked. In order toprevent the thread seizing, it should begreased using graphite grease, Part No.830 503 004 4 (50 gramme tube).

Since all sealing washers settle underload, the fittings of new vehicles or instal-lations must be retightened after a shorttime. The same also applies after the re-placement of devices, since new sealingwashers must always be used. Beforeretightening unions, first loosen the pipenut to avoid damaging the pipe.

Any non-compliance could lead to loss ofpressure within the system and thus tobrake failure!

Road vehicles

6 x 1 Instrumentation lines and control lines

8 x 1Engine exhaust brake,door actuating devices,special equipment

10 x 1 Control lines

12 x 1 Brake lines and supply lines

Road vehicles

15 x 1.5 Brake lines and supply lines

18 x 2Connection from compressor to pressure regulator, supply lines

1 2 3

1 2 3 4 5

General Information for Steel Pipes

1531

Installation Of Pipes And Screw Unions

The pipe must be cut off at right angles.A pipe saw-jig should be used.

After sawing the pipe, the resulting burrsand swarf must be carefully removed. Inorder to avoid these parts getting into thepiping system after fitting, thus destroy-ing valve seats or blocking filters, either

of which would cause failure of the brak-ing system.

Important:Do not use a pipe cutter !This would mean that no right angle isachieved in cutting and would result inexcessire burrs, both inside and out.

As a consequence:the internal diameter would be reducedand the union not being tight.

10.Assembly Instructions for Steel Pipe

With pipes with an external diameter upto 10 mm, it is advisable to screw theconnector of the coupling into the deviceand to assemble the pipe directly at theplace of installation.

The prepared pipe end, with pipe nut andcutting ring, is pushed directly into theconnector and the pipe nut is screwed onby hand until contact with the cutting ringis felt.

The pipe must now be pushed againstthe stop in the connector and the pipe nutmust be tightened by about three- quar-ters of a turn, where by the pipe must notrotate with the nut. Since the cutting ringhas now gripped the pipe, further push-

ing of the pipe is unnecessary. Finaltightening is effected by turning the nutby about one turn. Then loosen the pipenut and check whether the cutting ringhas penetrated the outer skin of the pipeand the raised collar is visible in front ofthe edge. If necessary, the pipe nut mustbe tightened further.

It does not matter if the cutting ring canbe rotated on the pipe end.

After completion of the joint, or after loos-ening, the pipe nut is to be tightened witha normal spanner, without applying anyexcessive force.

Push in Couplings

Before tightening the pipe nut

After tightening the pipe nut

1 Butt end3 Cutting ring2 Internal taper4 Visible collar

1

2

3

4

Visible collar

A mark made on the pipe nut makes it easier to count the specified number of turns.

154

Installation Of Pipes And Screw Unions10.Pre-assembly must be carried out in avice. The screw spanner must have alength which is approximately 15 timesthe width across flats. If necessary, itshould be extended using a pipe.

Tighten the coupling in the vice first.Screw on pipe nut by hand up to stop atcutting ring. Press pipe with thrust ringagainst front side of connector. Thentighten pipe nut with a 3/4 turn (Caution:Pipe must not turn at the same time!).The cutting ring now grips the pipe endand further pressing is no longer neces-sary. Final tightening is carried out if thepipe nut is tightened again with a 3/4

turn. The ring now cuts into the pipe, vis-ibly bunching in front of its first cuttingedge.

Final tightening is faciliated if the pipe nutis lossened a number of times, so that oilcan find its way again between the fric-tion surfaces.

During final assembly, please see thateach pipe end the corresponding thrustring get back to the coupling where pre-assembly has been carried out.

Insert thrust ring and sealing washer.


1 Visible collar2 Sealing washer3 Thrust ring4 Cutting ring

These pre-assemblies in large numbersrequire an enormous amount of time ifthey are to be produced in the way de-scribed above. In such cases, a pre-as-sembly unit is advisable. With it thecutting rings can be fitted quickly. Thedevice is not tied to one work-place butcan be used where desired.

1

2 3 4

Butt joint Couplings

Instructions for Bending and Fitting of Pipes

Basically pipe for braking systems mustnever be hotworked since this will de-stroy the surface protection, and thescaling of the pipe can cause break-downs.

Bending of the pipe is best carried outwith a commercial pipe bender.

155

Installation Of Pipes And Screw Unions 10.Assembly Instructions: for Throttle Inserts

By the use of throttled inserts, the charg-ing and exhausting time can be adjustedto the particular requirements. The throt-tle can be inserted into the push-in cou-pling, if the pipe nut has first beenloosened and the pipe pulled out. Pleasemake sure that the pipe end is shortenedby the thickness of the insert's rim.

for Copper PipeThe assembly instructions above are in-tended for the use of steel pipe. If soft-annealed copper pipe (Cu soft) is to beused, sleeve inserts must be used in thepipe ends to prevent crushing the pipewhen tightening the pipe nut.

The insert is to be lightly driven into thepipe until it is flush with the pipe end. Theteeth on the insert are pressed into theinner wall of the pipe so that the insertprevented from moving or failing out dur-ing assembly of the pipe.

The bending radius must never be lessthan 2D. The pipe end behind the bendshould, as far as possible, have a totallenght of at least 2 H..

When fitting the pipes, care must be tak-en that they are without stresses afterthe pipe nuts have been tightened. Thismeans that before tightening, the pipesfit so well that the tightening processdoes not serve to position them properly.

Any non-compliance of this could re-sult in damage to the units, e. g. causefissures in the cylinder base.

Hose CouplingsWithin a compressed air installation thetransition from pipe to hose, or converse-ly from hose to pipe, will repeatedly oc-cur if moving parts have to be connected.If the pipe ends cannot be formed into asatisfactory standard hose nozzle, ahose coupling must be used for such ajoint. It is not permissible to push thehose onto a plain cut-off pipe end.

Any non-compliance can result in thehose slipping off the pipe when pressu-rized. This would result in a sudden fail-ure of the braking system.

Cut off hose at right-angles and pushonto the hose nozzle as far as the stop.The hose must be secured with a hoseclamp.

The tools illustrated in the comments onsteel pipes are available from ERMETO ARMATUREN GMBH, D-33652 Bielefeld, Germany.

Throttle Insert

Insert pushed in

Insert driven in

Push-in coupling with sleeve insert fully assembled

156 1

General Information on Nylon Pipes

Installation Of Pipes And Screw Unions10.Use and Installation in Automotive VehiclesThe physical and mechanical propertiesof nylon pipe are very different fromthose of steel pipe.

Extensive tests and sample installationsin motor vehicles using various grades ofnylon have shown that because of thespecial properties of the material, flexiblenylon pipe of black polyamide 11 arebest suited for pneumatic braking sys-tems and associated equipment.

PropertiesMaterialBlack polyamide 11, flexible, resistant toheat and light, even to intense ultra-violetradiation.

Physical Properties

Mechanical Properties

Permissible TemperaturesIn normal vehicle operation, tempera-tures of - 40 °C to + 60 °C are permissi-ble.

The indicated temperature of + 60 °Cduring continuous loading for the flexiblegrade was selected so that no changesin the properties of the material occur. Attemperatures over + 60 °C the softeningagent contained in this material canslowly disappear and the material as-sumes the properties of the semi-rigidgrade.(Constant temperature loading capacityof the semi-rigid grade + 100 °C).

The physical properties of the semi-rigidand flexible pipes are the same. The val-ues for mechanical properties such astensile strength, elastic elongation andworking pressures are higher in the caseof semi-rigid pipe. By reason of theirgreater mechanical resistance to defor-mation (bending), semi-rigid pipes aremore difficult to lay than flexible ones.

Becauses of the limited temperatureloading capacity of polyamide 11, it is ad-visable not to use nylon pipe in the vicin-ity of the engine or exhaust system.Particular care should be taken whenwelding to ensure that the pipes are notdamaged, and if necessary they shouldfirst be dismantled.

If a sprayed vehicle is dried in a brakingchamber or using radiant heaters, theunpressurised pipework must not besubjected to temperatures up to 130 °Cfor longer than 60 minutes.

In order to avoid damage to nylon pipeswhen welding, a plate should be fitted onthe vehicle:

Available in German only.Part Number 899 144 050 4

Density at +20°C 1.04 g/cm³

Moisture absorption at + 20° C(between 30 and 100%relative air humidity) 0.5 to 1.9%

Specific heat 2.44 J/gK

Thermal conductivity 1.05 kJ/m.h.K.

Linear coefficient of expansion between -20° C and +100° C 15 x 10-5 (1/°C)

Melting point +186°C

tensile strength 4800 N/cm²

Elongation at rupture at 20°C 250%

Elastic elongation 3.7%

PipeDimensions

min. Bursting Pressurein bar

max. WorkingPressure at 20°C in bar

6 x 1 81 278 x 1 57 1910 x 1 45 15

12 x 1,5 57 1915 x 1,5 45 1518 x 2 51 17

This vehicle is equipped with

�� Tecalan nylon pipes Caution during welding operations.

Permissible exposure to heat of unpressurised lines: Not more than 130°C for 60 minutes.

��

157

Chemical ResistancePolyamide 11 is resistant to all mediaused in the motor vehicle such as petro-leum products, oils and greases. Thetubes are also resistant to alkalis, un-chlorinated solvents, organic and inor-ganic acids and diluted oxidising agents.(The use of cleaning agents contain-ing chlorine should be avoided). Ad-vice on resistance to chemicals otherthan those indicated can be given on re-quest.

Change in LengthWhen installing nylon pipes particular at-tention should be paid to their change inlength at different temperatures. Thechange in length of the pipe is approxi-mately 13 times that for a steel pipe.

The coefficients of expansion are:

For steel pipes 1.15 x 10-5 per °C

For nylon pipes 15 x 10-5 per °C

This indicates a change of length per me-tre of 1.5 mm for every 10 °C differencein temperature. This change in lengthmust not be restricted by the fittings hold-ing the pipe.To fasten the pipes in position, plastic-lined pipe clamps or clamps or holdersmade entirely of plastic should, be used.It should be possible for the pipe to moveeasily in the fastenings, so that tempera-ture induced changes in length can bedistributed uniformly over the entirelength of the pipe. The pipe should beclamped at approximately 50 cm inter-vals.

CouplingsThe range of coupling from Wabco usedin vehicles can also be used for nylonpipes. Clamping rings represent similarlyeffective unions for pipes. To ensuregood seal and tight fit of the couplings,sleeve inserts should be used for all as-semblies with cutting rings and thrustrings. The sleeves should not be forcedor driven in, as otherwise the pipes ex-pand and the cutting rings can no longerbe pushed on.

The couplings are made push-in cou-plings and buttjoint couplings.

The function of the cutting ring is thesame in both kinds of union.

When the pipe nut is tightened, the cut-ting ring is compressed by the internal ta-per of the connector and cuts into theouter wall of the pipe - to create a collarand form a sealed joint. The pipe sealedby the firm fit of the cutting ring on the in-ternal taper. The additional thrust ring inbutt-joint couplings is sealed with a seal-ing washer, which normally consists offiber.

Before fitting male couplings, the threadsof the connecting pieces should bechecked for damage. Damaged threadsmust be rectified. In order to prevent thethread seizing it is advisable to smear itwith graphite grease before screwing in.The seal can be made with fiber or alu-minium sealing rings or with thrust ringsand O-rings. Do not use hemp or liquidjointing compounds.

Since all sealing washers settle underload, the couplings of new vehicles or in-stallations must be retightened after ashort time. The same also applies afterthe replacement of devices, since newsealing washers must always be used.Before retightening fittings first loosenthe pipe nut to avoid damaging the pipe.

When assembling the coupling it is im-portant that the end of the pipe istrimmed at right angles and inserted intothe coupling as far as the stop. To trimthe pipe property at right angles, use canbe made of cutting devices which can beobtained for pipes with an external diam-eter of up to 22 mm.

Installation Of Pipes And Screw Unions 10.

158

Assembly Instructions on Nylon Pipes

Installation Of Pipes And Screw Unions10.Push-in couplings used for the followingpipe diameters:


1 Connector with internal taper 2 Sleeve insert 3 Cutting ring 4 Pipe nut

Butt-joint couplings are used forthe following pipe diameters:


1 Connector 2 Sealing washer 3 Thrust ring 4 Sleeve insert 5 Cutting ring 6 Pipe nut

Push-in CouplingsFor pipes with an external diameter of upto 10 mm, it is advisable to screw thethread of the coupling into the device andto assemble the pipes directly at theplace of installation.

The prepared pipe end, with insert, pipenut and cutting ring, is pushed directlyinto the connector and the pipe nut isscrewed up by hand until contact with thecutting ring is felt. (Figure see page 153)

The pipe must now be pushed againstthe stop in the connector and the pipe nutmust be tightened according to thetorque table below. The pipe must not ro-tate with the nut.

Table of permissible tighteningtorques

If the indicated torques are not achieved,the force required for loosening is re-duced, and if they are exceeded thesleeve insert will be deformed.

Before tightening the pipe nut


1 Sleeve insert2 Butt end3 Internal taper4 Cutting ring5 Visible collar

6 x 1 As instrumentation lines

8 x 1 As auxiliary systems, e.g., air suspensions

10 x 1 As control lines with limitedvolumetric throughput

12 x 1.5As control lines with larger vol-umetric throughput, as general lines within a brake system or as lines to the brake actuator.

15 x 1.5Lines for general supply and to braking cylinders in braking systems.

18 x 2Supply line between air reser-voir and relay valve for high air flow.

1 2 3 4

1 2 3 4 5 6

Pipedimensions

Tightening torque

Loosening forces at

6 x 1 13 to 14 Nm 13 Nm = 460 N8 x 1 15 to 18 Nm 15 Nm = 580 N10 x 1 20 to 30 Nm 20 Nm = 870 N12 x 1.5 25 to 35 Nm 30 Nm = 1200 N

1 2

3

4

5

159

The following method can be used tokeep as close as possible to the correcttightening torques when they cannot beaccurately measured:

Tighten the pipe nut of the coupling fin-gertight and then 1½ to 1¾ turns with aspanner. It is necessary for the thread tobe in good condition. Then loosen the pipe nut and checkwhether the cutting ring has penetratedthe outer skin of the pipe and the raisedcollar is visible in front of the edge.

Butt-joint CouplingsButt-joint couplings are assembled asdescribed under push-in couplings. Anadditional thrust ring and sealing washer,however, must be used.


1 Visible collar2 Sealing washer3 Thrust ring4 Cutting ring5 Sleeve insert

Table of permissible tighteningtorques:

Bending of Nylon PipesThe pipe can be bent cold, keeping to thebending radi indicated below. Since,

however, it has a tendency to straighten,it should be fastened before and aftereach bend.

To avoid kinking, the minimum bendingradi shown in the following table must beadhered to. .

Technical Inspection of the Brak-ing System

Inspecting authorities have given theirapproval in principle to the use of nylonpipe for pneumatic lines in vehicles as analternative to the steel pipe and brakehose previously used. This approval issubject to the connection that suitablematerial is used for this purpose, and thatthe installation instructions applicable tonylon piping are complied with.

By marking their nylon pipe with the in-scription „WABCO-TECALAN“, WABCOprovide a guarantee that the material issuitable in accordance with terms of de-livery. Correct installation of the nylonpiping can be checked at the time of finalinspection of the vehicle using the instal-lation instructions mentioned above.

Pipedimen-sions

Tighteningtorques

Looseningforces at

15 x 1.5 30 to 45 Nm 30 Nm = 2100 N18 x 2 40 to 60 Nm 40 Nm = 2450 N

1

2 3 4

5

Dimensions of Pipe

min. Bending Radius r

6 x 1 30 mm8 x 1 40 mm10 x 1 60 mm12 x 1.5 60 mm15 x 1.5 90 mm18 x 2 110 mm


160

WABCO Quick Connecting Fitting System for Air Braking Systems

General Comments

Installation Of Pipes And Screw Unions10.

The connecting elements offer thefollowing benefits:

� A high degree of leakage protection:Cascade dynamic sealing

� No corrosion since the individualcomponents are made of brass orstainless steel.

� Quick assembly since no time-consuming fitting of sleeves,fastening of union nuts and reworkingin the case of leakages is needed.

� The seal against the pipe is effectedby means of a special seal located infront of the clamping element whichmeans that the clamping element

cannot damage the sealing area onthe plastic pipe. The seal preventsboth air getting out and dirt getting in.

� The threaded screw-in portions havean integrated seal suitable forthreaded connections to DIN 3852and for connections the type ofVOSS plug-in unions.

� The throughput resistance is similarto that of the cutting-ring coupling.

� Operating temperature range-45°C to +100°C (peak +125°C).

� Integral Air Passage (Sunnest innersupporting ring wall thickness) forbetter and quicker brake response.

Swivel Part

Connector

Connector Pivot

Applications The quick connection fitting system issuitable for all air lines in vehicles usingplastic pipes.

Any type of plastic pipe can be used:

WABCOPart number

External-Øx wallthickness

Operatingpressure at20°C in bar

828 251 908 6 6 x 1 27

828 251 907 6 8 x 1 19

828 251 906 6 10 x 1 15

828 251 905 6 12 x 1.5 19

828 251 904 6 15 x 1.5 15

828 251 903 6 18 x 2 17

161

Tube in a ConnectorAll Connectors are stamped with tube di-mension, and a batch number.

The pipes must be cut at right angle. Amaximum deviation of 5° is permissible..

The pipe must be pushed fully home intothe push-in connector. No tool is needed.Whilst pushing in the pipe, turn it slightly.

It is advisable to mark the length pushedin to be able to check it later..

The push-in lengths and the forces re-quired for pushing the pipe into the thepush-in connectors are shown in the ta-ble below.

Push-In lengths:

After inserting the pipe, check the clampby applying a pulling force of at least 20 to 50 N.

Tightening torques

General CommentsFor reasons of safety, the connectioncannot be severed once the pipe hasbeen pushed in.

If the unit is to be exchanged, the con-nection must be unscrewed from the unit.The connection will turn on the pipe inthe process. In the event of the sealingring between the unit and the connectionjoint being damaged, it must be re-placed.

For elbows and tees fixed to the unit bymeans of a counter-nut, the same O-rings and compression rings are used asfor the cutting-ring couplings.

L = Push-In length

e = Marking

External pipe-Ø x wall thickness

Push-In lengthin mm (± 0,5)

Push-Inforces in N

6 x 1 20 < 100

8 x 1 21 < 120

10 x 1 25 < 120

10 x 1.25 25 < 120

10 x 1.5 25 < 120

12 x 1.5 25 < 150

15 x 1.5 27 < 150

15 x 2 27 < 150

16 x 2 27 < 180

18 x 2 28 < 200

Thread Tightenningtorques

M 10 x 1 16 - 20 Nm

M 12 x 1.5 22 - 26 Nm

M 14 x 1.5 26 - 30 Nm

M 16 x 1.5 32 - 38 Nm

M 22 x 1.5 36 - 44 Nm

Assembly Instructions:


162

Installation Of Pipes And Screw Unions10.Assembly Instructions: For theRO ConnectionThe range includes two sizes of RO con-nectors: RO 13 and RO 15.

The RO connection: Plug-In Pivot (maleRO) and Plug-On Swivel part (femaleRO) = Building Block (Turnable).

The Plug-In Pivots are straight partswhere as the Plug-In Swivel parts arenumerous form parts:Elbows, Tees; Crosses . . .

The connection should be done manual-ly by pluging the two parts together to thebottom, with a combined rotation.

A twisting pull should then be applied forcontrol.

Because of the swivelling of the buildingblock (turnable), the RO connectionmust not be used:

– Between the truck and it's trailer, orthe axles and the trailer chassis.

– To connect a brake device preca-riously balanced.

When a RO connection is already usedin a kit (swivelling combination). A male/

female screwed connection with a coun-ternut for firm locking after orientation,being the alternative solution.

Replacement and interchangea-billty The interchangeability is possible proivd-ed that:

– The threads used are in accordanceto ISO 4039-1 or ISO 4039-2 (me-tric).

– The tubes used are in accordancewith DIN 74 324/ DIN 73 378 or NFR12-632 (metric) or ISO 7628.

Only the connection RO (between pivotsand swivel parts) is not interchangeablewith parts from other manufacturers be-cause of a exclusive design.

The WABCO quick connection fittingsystem can consequntly be used in re-pleacement of both:

– Tratitional 24° screwed compressionfittings range (with nuts and slee-ves).

– All types of other quick connectionfitting systems.

Plug and rotation

163

Index: Page

1. Components of the Motor Vehicle’s Braking System7Air Cleaner 432 511 ... 0 10Air Dryer 432 4.. ... 0 11Air/Hydraulic Actuators 421 30. ... 0 / 423 0.. ... 0 34Air Intake Filters 432 6.. ... 0 8Air Pressure Gauges 453 ... ... 0 23Air Reservoir 950 ... ... 0 21Anti-Freeze Pump 932 002 ... 0 17APU - Air Processing Unit 932 500 ... 0 20Automatic Load Sensing Valves 68 40. ... 0 / 475 7.. ... 0 45Brake Chamber 421 0.. ... 0 / 423 ... ... 0 33Brake Valves 461 11. ... 0 / 461 3.. ... 0 27Check Valves 434 0.. ... 0 24Charging Valve 434 100 ... 0 25Compressor 411 ... ... 0 / 911 ... ... 0 9Coupling Heads 952 200 ... 0 61Drain Valves 434 300 ... 0 / 934 30. ... 0 22Duo-Matic Quick Coupling 452 80. ... 0 62Emty / Load Valve 473 30. ... 0 52Four-Circuit Protection Valves 934 7.. ... 0 19Hand Brake Valves 961 72. ... 0 37Knuckle Joint 433 30. ... 0 51Pressure Limiting Valves 475 009 ... 0 / 475 015 ... 0 26Pressure Reducing Valve 473 301 ... 0 52Relay Valves 473 017 ... 0 / 973 0.. ... 0 42Safety Valves 434 6.. ... 0 / 934 6.. ... 0 16Slack Adjuster 433 5.. ... 0 36Solenoid Valves 472 ... ... 0 41Three-Circuit Protection Valve 934 701 ... 0 18Trailer Control Valves 973 00. ... 0 54Tristop®-Spring Brake Actuator 425 3.. ... 0 / 925 ... ... 0 35Unloader 975 303 ... 0 15Wendelflex ® -Hose Connection 452 711 ... 0 60

2. Equipment For Trailer Braking Systems 63Adapter Valve 975 001 ... 0 74Automatic Load Sensing Valve 475 713 ... 0 78

475 714 ... 0 79Directional Control Valve 463 036 ... 0 74Height Limiting Valve 964 001 ... 0 73Line Filter 432 500 ... 0 66Load Sensing Relay EmergencyValve 475 712 ... 0 76

475 715 ... 0 80Relay Emergency Valves 971 002 ... 0 68Relay Valves 973 0.. ... 0 72Solenoid Valves 472 1.. ... 0 75Trailer Release Valve 963 00. ... 0 66Pressure Limiting Valve 475 010 ... 0 71Quick Release Valve 973 500 ... 0 73

3. Anti-Lock Braking System (ABS) 83ABS Relay Valve 472 195 ... 0 89ABS Sensor 441 032 ... 0 91

Index 11.

164

Index11.Page

Clamping Bush 899 760 510 4 91Operating Cylinder 421 44. ... 0 93Proportional Solenoid Valve 472 250 ... 0 92Solenoid Control Valve 472 195 ... 0 88

4. Sustained-Action Braking Systems On Motor Vehicles 953/2-Way Valve 463 013 ... 0 97Air Cylinder 421 41. ... 0 98Pressure Switch 441 014 ... 0 99Solenoid Valve 472 170 ... 0 99

5. EBS-Electronically Controlled Braking System 101Axle Modulator 480 103 ... 0 107Backup Valve 480 205 ... 0 106Brake Signal Transmitter 480 001 ... 0 105Central Module 446 130 ... 0 105Proportional Relay Valve 480 202 ... 0 106Trailer Control Valve 480 204 ... 0 108

6. Air Suspension Systems and ECAS (Electronically Controlled Air Suspension) 111ECAS - ECU 446 055 ... 0 117ECAS Height Sensor 441 050 ... 0 120ECAS Remote Control Unit 446 056 ... 0 120Levelling Valve 464 006 ... 0 113Pressure Sensor 441 040 ... 0 121Raise/Lower Valve 463 032 ... 0 114Solenoid Valve 472 90. ... 0 118

7. Clutch Servos 123Clutch Servo 970 051 ... 0 124

8. Air Braking Systems In Agricultural Vehicles 1273/2-Directional Control Valve 563 020 ... 0 131Load Apportioning Valve 475 604 ... 0 135Pressure Limiting Valve 973 503 ... 0 130Shut-Off Cock 452 002 ... 0 / 952 002 ... 0 131Trailer Control Valve 470 015 ... 0 / 471 200 ... 0 132

9. ETS and MTS Elektronic Door Control System For Motor Coaches 1374/2-Way Cock 952 003 ... 0 1404/3-Way Solenoid Valve 372 060 ... 0 1414/3-Way Solenoid Valve 472 600 ... 0 148Dorr Operating Cylinder 422 80. ... 0 142Dorr Operating Cylinder 422 812 ... 0 148Displacement Transducer 446 020 ... 0 144ETS - ECU 446 020 ... 0 140MTS - ECU 446 190 ... 0 147

10. Installation Of Pipes And Screw Unions 151

wabco brakes 3

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