vp44 co ee14e-11130

Pub. No. EE14E-11130

SERVICE MANUAL CONSTRUCTION& OPERATION

VP44

FOREWORDThis service manual describes the constructionand operation of the VP 44 (Radial plungerdistributor type fuel injection pump).This manual is intended for use by vehiclemaintenance technicians or persons with anadequate knowledge of injection pumps.

The contents of the manual, includingillustrations, drawings and specifications werethe latest available at the time of printing.The right is reserved to make changes inspecifications and procedures at any timewithout notice.

Tokyo, Japan

CONTENTS

PageCOMPONENT OUTLINE ........................ 1

1. OUTLINE ................................................ 1

2. FEATURES............................................. 2

3. SPECIFICATIONS .................................. 3

4. FUEL SYSTEM ....................................... 4

5. SYSTEM CONTROL DIAGRAM ............. 7

6. CONTROL UNIT SYSTEM

CONTROL DIAGRAMS ......................... 8

CONSTRUCTION ................................... 9

1. EXTERNAL VIEW................................... 9

2. CROSS-SECTIONAL VIEW ................. 10

3. EXPLODED VIEW ................................ 11

4. CONSTRUCTION ................................. 12

OPERATION ........................................ 21

1. LOW PRESSURE FUEL CIRCUIT ....... 21

2. HIGH PRESSURE FUEL CIRCUIT ...... 23

3. TIMING CONTROL ............................... 29

4. ANGULAR ENCODER ......................... 34

5. PUMP CONTROL UNIT........................ 35

- 1 -

COMPONENT OUTLINE

With radial plunger distributor type fuel injectionpumps, the fuel is pressurized by a radialplunger high pressure pump (with 2 or 3cylinders, depending on the number of enginecylinders) positioned axially to the driveshaft.Fuel injection quantity and timing are preciselycontrolled by two electronic control units.A high pressure solenoid valve and a TCV (atimer) are controlled by a pump control unitinstalled at the top of the pump. This controlunit works together with a second control unit,ie, the engine control unit (which detects suchvehicle information as engine speed andaccelerator pedal position), in a dual control unitsystem to ensure high reliability.

1. OUTLINE

Instead of utilizing the previous face cam, theradial plunger distributor type fuel injection pumputilizes a cam ring to enable fuel injection at highpressures, making it suitable for small, highspeed direct injection diesel engines.This pump was developed to provide the mostsuitable fuel injection quantity and injectiontiming to satisfy the demand for engine reliability,driveability, low smoke, low noise, high outputand cleaner exhaust emissions.

Pump control unit

Radial plunger high pressure pump

High pressure solenoid valve

Driveshaft

P-VP4C-001

TCV

- 2 -

COMPONENT OUTLINE

2. FEATURES[1] High pressure injectionThe radial plunger distributor type injectionpump can generate pressure of 100 MPa{approx 1,000 kgf/cm2} demanded by the small,fuel efficient, high pressure, high speed directinjection diesel engines.[2] High pressure atomization of fuel

injected from the nozzleThrough high pressure injection of fuel, the fuelinjection from the nozzle is atomized at highpressure with a high penetrating force (the fueldroplets penetrate further) and with greaterdispersion and distribution (mixing with air isimproved) so that combustion is improved. Thiscontributes to cleaner emissions.[3] Optimum fuel injection systemHigh speed control of fuel injection quantity andfuel injection timing suitable for the engine isperformed by the control unit, enabling lowerfuel cost and high output.[4] Improved enduranceThe components used in the pump are veryresistant to high pressure, ensuring improvedendurance.[5] Improved engine matchingAs fuel injection to the engine can be controlledfor each cylinder, matching to the engine isimproved.[6] Improved reliabilityAs a dual control unit system with both an enginecontrol unit and a pump control unit is used, thecontrol system is extremely reliable.

[7] Improved power performanceAs the optimum fuel injection quantitycorresponding to accelerator position iscontrolled by the control unit, increased torquein low accelerator pedal positions is possible,enabling improved power performance.[8] Decreased smoke at accelerationWhen fuel injection is increased to increaseengine power at acceleration, smoke is usuallygenerated by the excess fuel. The VP44 fuelinjection pump, however, accurately controlsfuel injection quantity even in this range toprevent the generation of smoke withoutadversely affecting acceleration.[9] Additional devices are unnecessarySuch addit ional devices as the boostcompensator and the aneroid compensator areunnecessary as compensation is made by thecontrol unit based on signals from each sensor.This results in less ‘clutter’ around the injectionpump.[10] Self diagnosis functionThe system includes a self diagnosis functionwhich displays error codes to facilitate thediagnosis of malfunctions.

- 3 -

COMPONENT OUTLINE

3. SPECIFICATIONSItem

Injection pump typeApplicable vehicles

Applicable number of engine cylindersDirection of rotationDrive methodInjection performance

Maximum pump pressurePlunger diameter x number

Maximum liftMaximum plunger speedMaximum allowable drive torque

SystemMinimum drive voltageMaximum high pressure solenoidvalve currentControl unit type

Battery specificationStandard performance

Standard control method

Timing feed backCompensation for variation betweenpump fuel injection quantitiesTimer advance angle range

Pump sizeWeight

SpecificationsVP44Passenger vehicles, recreational vehicles, small andmedium sized trucks (less than 1 / cylinder)4 cylinders, 6 cylindersClockwise / counter clockwiseToothed belt, gear, chain

100 MPa {approx 1000 kgf/cm2}4 cylinder: φ6.5 mm x 2, φ7 mm x 2, φ7.5 mm x 26 cylinder: φ7 mm x 3, φ7.5 mm x 33.5 mm1.9 m/second: 1000 r/min200 N.m {20.4 kgf.m}: 3 holed flange260 N.m {26.5 kgf.m: 4 holed flange(Maximum drive torque necessary under actual usageconditions: 150 N.m {15.3 kgf.m} limit)

6V≦20 A

Engine control unit, pump control unit(dual control unit system)12V specification, 24V specification

Fuel injection quantity control: high pressure solenoidvalve, time controlInjection timing control: TCV duty solenoid system,hydraulic timerCam position feed backPump EPROM, multi point compensation

Maximum advance angle: 15゜Identical to COVEC-FApprox 8.0 kg

- 4 -

COMPONENT OUTLINE

(1) Fuel piping systemCentering around the radial plunger distributortype fuel injection pump, the fuel piping systemconsists of a fuel tank, a feed pump, a fuel filter,nozzle holder assemblies and the pipingconnecting these components.(2) Fuel intakeThe fuel in the fuel tank is supplied to theinjection pump through the fuel inlet by the feedpumps in the fuel tank and the injection pump,after first passing through the fuel filter.The fuel filter is installed to filter the fuel, andalso has a sedimenter in the bottom to separateany water from the fuel.(3) Regulating fuel feed pressure and

delivery pressureThe fuel taken in at the fuel intake port ispressurized by the feed pump inside theinjection pump, and is then supplied to theplunger chamber through the high pressuresolenoid valve’s valve needle, which controlsthe direction of fuel flow.

4. FUEL SYSTEM[1] Fuel system schematic

Fuel tank

Feed pump

Fuel filter

Radial plunger distributortype fuel injection pump

Low pressure pipe

Nozzle holder assembly

Engine controlunit

P-VP4C-002

High pressure pipe

Pump control unit Overflow valve

At this time, the fuel pressure is greatest inproportion to pump rotational speed. When itexceeds a specified pressure, excess fuel isreturned to the intake side through the regulatingvalve.(4) Fuel pressurizationThe fuel delivered to the plunger chamber ispressurized by the radial plungers.(5) Determining the optimum fuel injection

quantity and fuel injection timingThe optimum quantity of high pressure fuel ispressure fed to the nozzle holder assembly atthe optimum timing by the high pressuresolenoid valve and the TCV (timer) controlledby the pump control unit.

- 5 -

COMPONENT OUTLINE

[2] Injection pump fuel intake system

[3] Injection pump fuel pressure feed system

Engine control unit

Fuel intake

Pump control unit

Feed pump

Regulating valve

Overflow valve

High pressuresolenoid valve

Constantpressurevalve

Radial plungerhigh pressure pump

Distr ibutor head

P-VP4C-003

P-VP4C-004

- 6 -

COMPONENT OUTLINE

[4] Fuel pressurization control

P-VP4C-005

Accumulatordiaphragm

Diaphragmchamber

Overflow valve

Feed pump

Regulating valve

TCV

To feed pump intake

Servo valve

Hydraulicstopper

Timer pistondrive fuelcharge

Timer piston



Radial plunger

Valve needle

High pressurepassage

Timer pistondrive fuel return

- 7 -

COMPONENT OUTLINE

5. SYSTEM CONTROL DIAGRAM

P-VP4C-006

Engine speed(crank shaft)

Accelerator pedal

Idle switch

Boost pressure

Air flow volume

Air temperature

Cooling watertemperature

Vehicle speed

Cruise controloperation panel

Brake

Clutch

Air conditioner

Beginning ofinjection

+12V (24V)

Engine control unit

Power supply

Atmospheric pressure sensorSignal inputSignal evaluation

Signal processing・ Fuel injection quantity・ Beginning of pressure feed・ EGR・ Boost pressure・ Vehicle speed・ Engine load・ Monitor・ Minimum function

maintenance・ Calibration

Power outputSignal output

InterfaceDiagnosis

Radial plunger distr ibutor typeinjection pump

Pump control unit

+12V(24V)

CAN

DZG

MAB

LGS

EPC

EPC

Option

EGR valve

Turbo charger

A/C compressor

Diagnostic lamp

Diagnosticrequirement

Service tester

CAN

AutomatictransmissionEngine control unit

CAN: Control area networkDZG: Crankshaft speedMAB: Solenoid valve switch OFFLGS: Low idle signal

- 8 -

COMPONENT OUTLINE

6. CONTROL UNIT SYSTEM CONTROL DIAGRAMS[1] Block diagram

[2] Circuit diagram

Engine control unit(ECU)

Pumpcontrol unit(PCU)

Fuel injectionpump(mechanicalsection)

Injection timing

Injection quantity

Response signal

Additionalsignals

Engine speed

Accelerator pedal

Air temperature

Boost pressure

Air flow volume

Others

Sensors

Additionaloperations

To high pressure solenoid valve

Timer controldevice

Cam ring rotational angle


To timer control device

Self diagnosis / interface / signal

Engine speed(crank)

Accelerator pedalIdle switch

Engine control unit Pump control unit

Pump speed

Injection quantity

Injection timing


CAN

MAB

DZG


P-VP4C-007

CAN: Control area networkMAB: Solenoid valve switch OFFDZG: Crankshaft speed

Fuel temperature

- 9 -

CONSTRUCTION

1. EXTERNAL VIEW

Side view (drive side on right)

Side view (drive side on left)

Fuel inlet Overflow valve

P-VP4C-008

Regulating valve

Top view (drive side on right)

- 10 -

CONSTRUCTION

2. CROSS-SECTIONAL VIEW

Pump control unit

Feed pump

Driveshaft

Distributor head

Timer TCV (duty solenoid)

Angular encoder



Highpressuresolenoidvalve

Rotor shaft

Barrel Valve needleFuel returnAnnularpassage

Accumulator diaphragm

Diaphragm chamber

Low pressure inlet

Distributor slit

High pressure outlet

Constant pressurevalve holder

Radialplunger

P-VP4C-009

P-VP4C-010

Distributor slit

Annularpassage

Barrel

Valveneedle

Low pressure inlet

High pressure passage


- 11 -

CO

NS

TR

UC

TIO

N

133134

135/2

123

471

50/5

50/7

109

213

424

59

135/1

135/4107

127

3167

480

111

7/3

7/4

135/3135/5

271

206207

270

105104

3432

4142

35/335/6

39

35/4

50/1650/15

35/1

30

61

50/6

50/11

50/8

50/1

50/2

62

59

6349

12

19

17

424

4

31/1/2

4257/2

400

7/1

2122

20

23

25

3738

104105

1

35/2

36

35/5

58

50/12

50/109

10

50/950/3

54

5150/4

50/14

50/1333

3.E

XP

LO

DE

D V

IEW

P-VP4C-011

- 12 -

CONSTRUCTION

The following functional components are locatedeither inside the radial plunger distributor typeinjection pump housing or compactly installedon the pump.● Feed pump (a vane type pump) and

regulating valve● Radial plunger high pressure pump and

constant pressure valve● Distributor head● High pressure solenoid valve● Timer and TCV (duty solenoid)● Angular encoder● Pump control unit

4. CONSTRUCTION[1] Fuel injection pump body

Feed pumpAngular encoder

Pump control unit


Timer


Driveshaft

Through the combination of each component’sfunctions, the strictly defined target values aremaintained and the performance characteristicsdemanded by the engine are satisfied.The radial plunger distributor type injection pumpis fixed directly to the engine by a flange anddriven by a chain, gear or toothed belt. Toprevent mistaken installation of the injectionpipes, symbols (A, B...F) are marked on thedistributor head on the side of the constantpressure valve so that each constant pressurevalve holder can be matched with i tscorresponding engine cylinder.

Distributor head

P-VP4C-001

Constant pressurevalve holder

TCV (duty solenoid)

Constant pressure valve

- 13 -

CONSTRUCTION

[3] Regulating valveThe regulating valve consists of a valve holder,a spring and a valve piston. Ports are arrangedradially in the valve holder.The valve piston is pushed to block the ports bythe spring force.The valve piston opening pressure can beadjusted by adjusting the spring’s set force.

[2] Feed pump (low pressure section)The feed pump consists of a rotor, vanes and acasing ring. The rotor is driven by the driveshaft.Four vanes are assembled in the rotor.A spring is assembled on the inside of eachvane, and each vane is always pushed againstthe casing by this spring force and centrifugalforce.When the rotor is driven by the driveshaft, thevolume of the inlet side chamber increases andfuel from the fuel tank is sucked in through theinlet.Conversely, the volume of the outlet sidechamber decreases and fuel is delivered to theradial plunger high pressure pump through aregulating valve, which maintains the fueldelivery pressure from the outlet at a pressurenot exceeding a specified pressure.

Driveshaft

Rotor Casing ring

Inlet

Vane

Chamber

Outlet

Vane

Spring

Valve holder

Spring

Valve piston

Port

From outlet

To inlet

To radial plungerhigh pressurepump

Regulating valveFuel intake

Feed pump

P-VP4C-012

P-VP4C-013

P-VP4C-014

Timer

- 14 -

CONSTRUCTION

[4] Radial plunger high pressure pump (high pressure section)

Timer

The radial plungers are pushed against thecam faces by feed pump delivery pressurevia the roller shoes assembled in thedriveshaft’s guide slits and the rollers.With driveshaft rotation, the radial plungersare pushed in towards the center of the rotorshaft by the cams ring’s inner race cams tocompress the fuel.

Plunger chamber

Driveshaft guide slit

From feed pump



● The suction and compression of fuel into theradial plunger high pressure pump arecontrolled by the high pressure solenoidvalve.

Constantpressure valveholder

● The radial plunger high pressure pumpconsists of a cam ring, a rotor shaft, rollershoes, rollers and radial plungers.The cam ring has cams on the inner race (4cylinder engines: 4 cams; 6 cylinderengines: 6 cams) and the outer race isconnected to the timer by a ball pin.The rotor shaft is driven by a fuse plateconnected to the driveshaft. The radialplungers are assembled inside the rotorshaft.

P-VP4C-015

P-VP4C-016

Cam ring

Driveshaft

Rotor shaft

Roller shoe

Radial plungers

Ball pin

Roller

- 15 -

CONSTRUCTION

● Types of radial plunger high pressure pumpThere are either two or three radial plungers, depending on the number of engine cylinders.

For 4 cylinders

Radial plungers: 2

[5] Constant pressure valve (CPV)The constant pressure valve (CPV) consists ofa holder, a spacer, a valve spring, a valve, aseat, a ball, a ball support, a spring and a plug.The valve is equipped with an orifice to suppressthe reflected pressure wave (the cause ofsecondary injection) that results at nozzleclosing at the end of injection.The valve is opened by high pressure fuel andthis high pressure fuel is delivered to the nozzleholder assembly.

HolderSpacer

Valve spring

ValveSeatBall

Ball supportSpring

Plug

Orifice

P-VP4C-017

P-VP4C-018

Inner race cam:4 cam slopes Radial plungers: 3

Inner race cam:6 cam slopes

For 6 cylinders

- 16 -

CONSTRUCTION

[6] Distributor head

● At the end of injection, the high pressuresolenoid valve current is turned OFF andthe valve needle seat is opened, althoughcompression continues until the radialplunger reaches the cam’s top dead center.After the completion of pressure delivery, theexcess fuel flows through the passage tothe diaphragm chamber, where pressure isdecreased by the accumulator diaphragmand, simultaneously, accumulated for thenext injection.

Overflow valve

To fuel tank


Valve needle

Diaphragm chamber


P-VP4C-010

P-VP4C-019

Rotor shaft

BarrelValve needle

Fuel returnAnnular passage


Diaphragm chamber

Low pressure inlet

Distributor slit


Radialplunger

Distributor slit

Annular passage

Barrel

Valve needle

Low pressure inlet



Head

The radial plunger is pushed outwards(towards the cam ring) by the feed pump’sfuel delivery pressure, and excess fuelreturns to the fuel tank through the fuelreturn and the overflow valve. During thefuel pressure-delivery process, the highpressure solenoid valve’s valve seat isclosed (as the current is ON). The highpressure fuel compressed by the radialplunger, through rotor shaft rotation, flowsthrough the distributor slits connected to theinjection cylinder’s high pressure outlets andto the nozzle holder assembly via theconstant pressure valve holder.

● The distributor head consists of a head, abarrel pressfitted to the head, a rotor shaftwhich slides inside the barrel, a highpressure solenoid valve needle and anaccumulator diaphragm.The fuel oil supplied by the feed pump flowsthrough the low pressure inlet, theaccumulator diaphragm chamber and anannular passage.During the fuel suction process, the highpressure solenoid valve’s valve needle seatis open (as the current is OFF) and fuel fillsthe high pressure passage.

- 17 -

CONSTRUCTION

[8] High pressure solenoid valveThe high pressure solenoid valve consists of avalve seat, a valve needle, a magnet anchor (amovable iron core), a coil and a magnet. Thevalve needle rotates together with the rotor shaft.When current controlled by the pump controlunit flows to the coil, the magnet anchor andthe valve needle are pushed towards the valveseat.When the valve seat is completely closed bythe valve needle, the fuel in the high pressurepassage is isolated from the low pressurepassage, is compressed by the radial plungerhigh pressure pump, and injected into the enginecylinder through the nozzle holder assembly.When the injection quantity reaches thatdemanded by the engine, the current to the coilis cut, the valve seat opens and injection of fuelis completed.The high pressure solenoid valve determinesthe supply of fuel to the radial plunger highpressure pump and the injection quantity foreach cylinder.

[7] Overflow valveThe overflow valve consists of a valve holder, aspring and a ball valve, and is installed on theside of the injection pump.The valve holder is equipped with a port and anorifice port. The orifice port assists in automaticair bleeding.When the excess fuel returned from thedistributor head’s fuel return exceeds a specifiedpressure, the fuel pressure pushes the ball valveup so that the fuel can return to the fuel tank.The overflow valve maintains the returned fuelat a specified pressure, and also works to coolthe injection pump body.

Valve holder

Spring

Ball valveOrifice por t

To fuel tank

From fuel return

Overflow valve


Valve seat

Valve closingdirection Valve needle

Magnet anchor(movable iron core)

Coil Magnet

Rotor shaft

P-VP4C-020

P-VP4C-021

P-VP4C-022

P-VP4C-023

Port

- 18 -

CONSTRUCTION

[9] Timer

The timer piston contains a servo valve,which opens and closes a control port; ahydraulic stopper, which, acting in the sameaxial direction, sets the position of the servovalve; and a return spring.On the left of the timer piston is the timerpiston drive pressure chamber (a highpressure chamber), and on the right is thetimer’s low pressure chamber.The delivery pressure of the fuel deliveredfrom the feed pump acts on the annularchamber, which is connected to the TCV.

● The left hand figure shows a side view ofthe timer.The timer piston has a return channelconnecting the high pressure chamber to thelow pressure chamber through the servovalve. (This is the return passage for fuel attimer piston retard.)

● The timer consists of a timer piston, a servovalve, a servo valve set spring, a hydraulicstopper, a hydraulic stopper return springand a timer piston return spring.The timer is installed on the bottom of thepump housing at right angles to the injectionpump’s axial orientation.The timer piston is connected to the ball ofthe cam ring so that axial movement of thetimer piston is converted to cam ring rotation.

P-VP4C-024

P-VP4C-025

Timer pistondrive pressure chamber(high pressure chamber)

Servo valve

Timer piston

Timer piston return springServo valve set spring

Timer’s lowpressure chamber

Hydraulic stopperreturn spring

Hydraulic stopper

Annular chamber

Cam ringBall

Side view of the timer

Return channel

Timer pistonHighpressurechamber

Low pressurechamber

Servo valve

- 19 -

CONSTRUCTION

P-VP4C-026

● The left hand figure shows a top view of thetimer.The timer piston has an inlet channelconnecting the high pressure chamber andthe feed pump’s outlet side passage throughthe servo valve. (This is the fuel passage attimer piston advance.)The inlet channel is equipped with a checkvalve (with a ball valve on the orifice side,and a pin pressfitted on the opposite side)to prevent reverse flow from the highpressure chamber to the feed pump.

Top view of timer

Inlet channel

P-VP4C-027Oblique view of timer

● The left hand figure shows an oblique viewof the timer.The timer piston has a spring chamberbalance port connecting the servo valve setspring chamber and the low pressurechamber. (This passage equalizes thepressure of the servo valve set springchamber.)

Spring chamber pressurebalance port

[10] TCVThe TCV consists of a valve body, a valveneedle, a valve casing, a magnet anchor (amovable iron core), a coil, a flange plate (forinstallation) and a connector. The valve bodyis equipped with an orifice port.The TCV is installed on the pump housing atright angles to the timer ’s axial orientation, andcontrols the pressure of the annular chamberof the timer’s hydraulic stopper.

Valve body

Connector

P-VP4C-028

TCV

P-VP4C-029

Flange plate for installation

CoilMagnet anchor(movable iron core)

Valve casing

Valve needle

Orifice por t

Servo valve

Timer piston

Highpressurechamber

From feed pump

Timer piston Servo valve set spring chamber

Lowpressurechamber

Check valve

- 20 -

CONSTRUCTION

[11] Angular encoderThe angular encoder consists of a flexibleconnecting harness, the angular encoder itself,and the angular encoder retaining ring. A sensorwheel with precisely machined teeth is fixed tothe driveshaft.The sensor wheel has gaps in the teethcorresponding to the cylinder positions. Thesegaps are in a fixed relation to the enginecylinders and the camshaft.The peaks and troughs of the teeth are scannedby the angular encoder to determine the actualspeed of the injection pump.The angular encoder is mounted on the retainingring, which can be rotated and is connected tothe cam ring. Thus, the angular encoder rotateswith the cam ring in response to timermovement.The cam ring’s angular rotation signal and theactual pump speed are transmitted through theflexible connecting harness to the pump controlunit.

Flexible connectingharnessAngular encoder

Sensor wheel

Angular encoderretaining ring

Driveshaft

Flexible connectingharness Angular

encoder

Sensor wheel


Driveshaft

P-VP4C-001

P-VP4C-030

P-VP4C-031

[12] Pump control unitThe pump control unit is installed directly on topof the injection pump and is equipped with atemperature sensor.The pump control unit determines the drivesignals for the TCV and the high pressuresolenoid valve from information from the enginecontrol unit.The pump control unit receives signals from theangular encoder for injection pump speed andcam ring rotation and outputs TCV controlsignals, which are the basic timer drive signalvalues.Fuel injection quantities predetermined in theengine control unit are converted to injectiontiming (time control) by the pump control unitand output as high pressure solenoid valve drivesignals.At this time fuel temperature is taken intoconsideration.The bottom of the pump control unit is cooledby the fuel in the fuel injection pump.

Pump control unit

Cam ring

- 21 -

OPERATION

1. LOW PRESSURE FUEL CIRCUIT

Feed pump

Regulating valveOverflow valve

Fuel suction

To fuel tank

P-VP4C-003

The low pressure fuel circuit must supplysufficient fuel to the high pressure fuel circuit.

[1] Feed pumpThe feed pump, driven by the driveshaft,performs suction and supply of fuel.The vanes assembled in the rotor are pressedagainst the inside of the casing ring by springforce and centrifugal force during rotation to formchambers.When the vanes rotate, the volume of thesechambers increase when they reach recessesin the casing ring connected to the inlet port.Pressure then decreases and fuel is drawn in.When the chambers have passed the inlets andrecesses, the volume decreases and the fuel iscompressed. Fuel pressure increases until thechamber reaches the outlet, where the fuelpasses through the regulating valve to the highpressure fuel circuit.

The main components are the feed pump, theregulating valve and the overflow valve.

Driveshaft

Rotor

Casing ring

Inlet

Fuel suction

Vane

Chamber

Outlet

Fuel supply

P-VP4C-032

- 22 -

OPERATION

Valve piston

Port

From outlet

To inlet

Spring

[2] Regulating valveWhen feed pump speed increases so that thedelivery pressure of the fuel delivered from theoutlet exceeds the regulating valve spring force,the valve piston is pushed up.Excess fuel passes through the ports andreturns to the inlet side, and the deliverypressure is maintained within a specified range.When feed pump speed decreases so that thedelivery pressure decreases, the valve pistonis pushed down by spring force to close the port.

[3] Overflow valveWhen the pressure of the fuel returned from thedistributor head’s fuel return exceeds the springforce, the overflow valve’s ball valve is pushedup.Excess fuel passes through the port and returnsto the tank, and fuel pressure inside the pumpchamber does not exceed a specified pressure.By returning fuel to the tank to prevent the fuelfrom exceeding a specified pressure, theoverflow valve also works to cool the injectionpump and perform air bleeding.The orifice port is installed to assist in automaticair bleeding.

Valve holder

Spring

Ball valve

Orifice por t

To fuel tank

From fuel return

Port

P-VP4C-033

Pump speed

Beginning of regulatingvalve operation

P-VP4C-013

Pu

mp

ch

am

be

rp

ress

ure

- 23 -

OPERATION

2. HIGH PRESSURE FUEL CIRCUIT

Pump control unit

Radial plunger high pressure pump

Distr ibutor head



P-VP4C-004

In addition to a high pressure generating device,the high pressure circuit also consists of fuelpiping, and devices to set the beginning ofinjection and fuel injection quantity.The main components are as follows.

P-VP4C-034

[1] Radial plunger high pressure pumpWhile the radial plungers assembled to the rotorshaft rotate, they are held against the inside ofthe cam ring (via the roller shoes and rollers) byfuel delivery pressure from the feed pump andcentrifugal force.The radial plungers perform rotationalmovement as well as internal cam inducedreciprocating movement to suck in andcompress the fuel in the plunger chamber.

Radial plunger

Rotor shaft

Cam ring

Roller shoe

Roller

Internal cam

Plunger chamber

High pressure generation: Radial plunger highpressure pump

Fuel distribution: Distributor headBeginning of injection timing: Timer (TCV)Prevention ofsecondary injection: Constant pressure valve

- 24 -

OPERATION

P-VP4C-035

When the radial plungers rotate from the topdead center position the volume of the plungerchamber increases. Fuel is sucked in until theplungers reach the bottom dead center position.

(1) Fuel suction

Radial plunger’stop dead center position

Radial plunger’sbottom dead center position

Radial plunger’s intermediate position

When the radial plungers rotate from the bottomdead center, they are pressed up by the camring’s internal cams so that the volume of theplunger chamber decreases, and fuel iscompressed until the plungers reach the topdead center.

Plunger chamber Radial plungerFuel suction

(2) Fuel compression

Fuel compression

P-VP4C-036

At fuel suction, the high pressure solenoidvalve’s valve needle seat is open (and the highpressure passage from the feed pump is open).

At fuel injection the high pressure solenoidvalve’s valve needle seat is closed (and the highpressure passage from the feed pump isclosed).

Radial plunger’stop dead center position

Radial plunger’sbottom dead center position

Radial plunger’s intermediate position

- 25 -

OPERATION

[2] Distributor headThe distributor head distributes the highpressure fuel that has flowed through therotating rotor shaft’s distributor slits and thebarrel’s high pressure outlets (4 cylinders: 4; 6cylinders: 6) to the engine cylinders throughthe constant pressure valve and the nozzleholder assemblies.The high pressure solenoid valve’s valve needlechanges the passage to the radial plunger highpressure pump between fuel suction and fuelcompression.P-VP4C-037

Rotor shaft

Distributor slit High pressure outlet

Constantpressure valveholder

Barrel

(1) Fuel suction process

Valve needle

P-VP4C-010

When the plungers move in the bottom deadcenter direction from the top dead center, thefuel delivered from the feed pump flows fromthe low pressure inlet, through the annularpassage and the valve needle into the distributorhead, and is delivered into the high pressurepassage.

The radial plungers are pushed against the camring’s inner cams by the fuel delivery pressure,the volume of the plunger chamber increases,and fuel suction is performed. At this time, therotor shaft’s distributor slits are not connectedto the barrel’s high pressure outlets.

Rotor shaft

BarrelValve needle



Diaphragm chamber

Low pressure inlet

Distributor slit


Radial plunger

Distributor slit

Annular passage

Barrel

Valve needle

Low pressure inlet



Head

- 26 -

OPERATION

(2) Fuel pressure delivery process

P-VP4C-038

The radial plungers are pushed up by the camring’s cams, the volume of the plunger chamberdecreases and the fuel is compressed. At thistime, the distributor slits are connected to thebarrel’s high pressure outlets by rotor shaftrotation.

(3) End of fuel pressure deliveryFuel injection quantity control is performed fromthe beginning of pressure delivery at thebeginning of cam lift until the high pressuresolenoid valve opens at the end of pressuredelivery. This interval is called the pressuredelivery interval. Accordingly, the interval thatthe high pressure solenoid valve is closeddetermines the fuel injection quantity (highpressure fuel supply ends when the highpressure solenoid valve opens).Even after the high pressure solenoid valve’send of pressure delivery (high pressure solenoidvalve: open), the radial plungers continue topressure feed fuel until they reach the cams’top dead centers. The excess fuel flows throughthe passage until it reaches the diaphragmchamber. At this time the pressure of the highpressure fuel flowing back through the lowpressure circuit is decreased by the accumulatordiaphragm, and is simultaneously accumulatedin preparation for the next injection.

P-VP4C-039Diaphragm chamber


Rotor shaft

BarrelValve needle



Diaphragm chamber

Low pressure inletDistributor slit


Radial plunger

Distributor slit

Annular passage

Barrel

Valve needle

Low pressure inlet



Head

The high pressure fuel is then delivered throughthe high pressure passage, the distributor slitsand the high pressure outlets, and then throughthe constant pressure valve to the nozzle holderassembly.

- 27 -

OPERATION

P-VP4C-022

P-VP4C-040

P-VP4C-041

P-VP4C-042

Top dead center Top dead center

Radialplunger Bottom dead center

ClosedHighpressuresolenoidvalve

Open

[3] High pressure solenoid valveThe high pressure solenoid valve has a valveneedle, and this valve needle is opened andclosed by the control current from the pumpcontrol unit.This results in the switching of the fuel outflowpassage to control fuel injection quantity.

Valve needle

(1) Beginning of injectionWhen control current from the pump control unitflows to the high pressure solenoid valve coil,the magnet anchor (a movable iron core) ispushed, together with the valve needle, towardsthe valve seat. When the valve seat iscompletely closed by the valve needle, the pathof the fuel in the high pressure passage to thelow pressure circuit is cut.The pressure of the fuel in the high pressurepassage is rapidly increased by radial plungerlift, and the high pressure fuel is deliveredthrough the constant pressure valve to thenozzle holder assembly and is injected into theengine cylinder.(2) End of injectionWhen the fuel injection quantity demanded bythe engine is reached, the current to the coil iscut and the valve seat is reopened by the valveneedle. As a result of this, a path is opened forthe fuel in the high pressure passage to the lowpressure circuit and the pressure decreases.With a decrease in injection pressure the nozzlecloses and fuel injection to the engine ends.To accurately control this process, the controlunit determines the actual closing point of thehigh pressure solenoid valve.

Valve needle Magnet anchor

Valve needle

Coil

High pressurepassage Constant pressure

valve

Coil

Open

- 28 -

OPERATION

[4] Constant pressure valve (CPV)The constant pressure valve decreases thereverse pressure wave (ie, the reflected wave)generated at nozzle valve closing to prevent thenozzle from reopening (ie, secondary injection).

(1) Beginning of deliveryThe radial plunger compresses the fuel in theplunger chamber. When the pressure of thefuel delivered to the CPV overcomes theresidual pressure in the injection pipe and thevalve spring set force, the valve is pushed upand the fuel is delivered to the nozzle holderassembly (beginning of fuel delivery).

P-VP4C-043

From high pressurepassage

To nozzle holderassembly

Valve Valve spring

P-VP4C-018

● When the pressure of the fuel in the pipefalls below a specified pressure, the ball ispushed against the valve by the spring toprevent the return of fuel inside the pipe. Asa result of this, a stable pressure ismaintained in the pipe (residual pressure)until the next delivery interval.

BallSpring Valve

(2) End of delivery● When the pressure of the fuel in the high

pressure passage is suddenly decreased bythe opening of the high pressure solenoidvalve, the valve is pushed against the seatby the valve spring set force and closes. Atthis time, the reverse pressure wave (ie, thereflected wave) generated by nozzle closingflows through the orifice, pushes down theball and ball support and is decreased.

P-VP4C-044

From highpressurepassage


Valve

Orifice

Ball

Seat

Valve springBall support

From high pressurepassage


Also, the constant pressure valve suppressesthe generation of cavitation in the high pressurepipe, which is the cause of pipe erosion, andalso maintains a stable pressure in the injectionpipe (residual pressure) to ensure stabilizedbeginning of injection timing for subsequentinjection.

- 29 -

OPERATION

P-VP4C-045

The timer determines the optimum injectiontiming against variations in engine speed.The pressure of the fuel fed from the feed pumpis adjusted in accordance with speed by theregulating valve. This delivery pressure actson the hydraulic stopper’s annular chamber ascontrol pressure. The chamber pressure of theannular chamber is controlled by the TCV.

3. TIMING CONTROL[1] Timer operation

The timer is connected to the radial plunger highpressure pump’s cam ring by a ball pin, and axialtimer piston movement is transferred to the camring in the form of rotational movement.Timer piston movement to the right (to the springside) advances injection timing.The main components are the timer, the TCVand the angular encoder.

TCV

(1) Beginning of injection settingThe engine control unit contains predeterminedbeginning of injection characteristic mapscorresponding to engine operating conditions(engine load, speed and cooling watertemperature).The pump control unit is constantly comparingthe set beginning of injection timing and theactual beginning of injection timing. If there is adifference, the TCV is controlled by the dutyratio. (The actual beginning of injection timingis determined from the angular encoder signal.)

Engineload

Enginespeed

Enginecoolingwatertemperature

Cam ring

Timer piston

Servo valve

Feed pump

Outlet

Inlet

Hydraulic stopper

Fuel suction

Annular chamber

Ball pin

Return passage

Enginecontrol

unit

Pumpcontrol

unitTCV

Angularencoder

- 30 -

OPERATION

(2) When the annular chamber pressure islow (advance angle 0)

When the pressure of the annular chamber isless then the set force of the hydraulic stopper’sreturn spring, the hydraulic stopper is pushedto the left (in the retard direction).Consequently, the servo valve is also pushedto the left and stops at the position where itbalances the force of the servo valve set spring.Because of this, the passage to the timer’s highpressure chamber (ie, the inlet channel) is cut.The timer piston is held on the left hand side(ie, the retard side) by the timer piston returnspring.

P-VP4C-046

Timer piston return spring

P-VP4C-047

(3) When the annular chamber pressure hasincreased (advance)

● When the annular chamber pressureincreases and exceeds the force of thehydraulic stopper return spring, the hydraulicstopper is moved to the right (ie, in theadvance direction).Consequently, the servo valve is also movedto the right by the servo valve set spring andthe inlet channel to the timer’s high pressurechamber is opened.

Side view of timer

Highpressurechamber

Inlet channel

Top view of timer

Annular chamberHydraulic stopper


Servo valve set spring

Servo valve

Timer piston

Returnchannel

Side view of timer

AnnularchamberHydraulic stopper



Servo valve

Returnchannel


Highpressurechamber

Inlet channel

Top view of timer

Timer piston

Return channel Open

Inlet channel Closed

Return channel Closed

Inlet channel Open

- 31 -

OPERATION

P-VP4C-048

P-VP4C-049

● The fuel from the feed pump flows throughthe inlet channel into the timer’s highpressure chamber.When the fuel feed pressure exceeds theset force of the timer piston’s return spring,the timer piston is pushed to the right (ie, inthe advance direction) and the cam ring istu r ned in the advance d i rec t i on .Consequently, the cam ring’s cams advancethe rad ia l p lungers ’ beg inn ing o fcompression interval to bring about anadvance in the beginning of injection.A maximum timer advance angle positionof 15 cam angle degrees (equivalent to 30crankshaft degrees) is possible.

(4) Stable condition● The hydraulic stopper is moved to the right,

the annular chamber pressure and the setforce of the hydraulic stopper return springare balanced, and the hydraulic stopper isstationary.The timer piston, imitating servo valvemovement, is moved in a direction to cut theinlet channel.Consequently, the flow of fuel to the timer’shigh pressure chamber is stopped, and thetimer piston stops in the position where thetimer’s high pressure chamber pressure andthe set force of the timer piston return springare balanced.

Side view of timer




Servo valve

Returnchannel


Highpressurechamber

Inlet channel

Top view of timer

Timer pistonFrom feed pump

Cam ring

Side view of timer




Servo valve

Returnchannel


Highpressurechamber

Inlet channel

Top view of timer

Timer piston


Inlet channel Open



- 32 -

OPERATION

P-VP4C-050

(5) When annular chamber pressure hasdecreased (at timing retard)

● The TCV, in response to pump control unitcontrol signals, increases the time that thereturn passage (between the annularchamber and the feed pump inlet) is opento decrease annular chamber pressure.The annular chamber pressure decreases,and when it is less than the set force of thehydraulic stopper return spring, the hydraulicstopper and the servo valve move to the left(ie, in the retard direction) until the set forcesof the hydraulic stopper return spring andthe servo valve set spring balance theannular chamber pressure.Consequent ly, the re tur n channe lconnecting the timer’s high pressurechamber to the low pressure chamber isopened.

● The fuel in the timer’s high pressure chamberflows through the return channel to returnto the low pressure chamber.Because of the decrease in the highpressure chamber pressure, the timer pistonis moved to the left (ie, in the retard direction)by the timer piston return spring, and thecam ring is rotated in the retard direction.Consequently, the cam ring’s cams retardthe rad ia l p lungers ’ beg inn ing o fcompression interval to retard the beginningof injection.

P-VP4C-051

● The timer piston, imitating servo valvemovement, is moved in a direction to cut thereturn channel.Consequently, the flow of fuel from thetimer’s high pressure chamber to the lowpressure chamber is stopped, and the timerpiston stops in the position where the timer’shigh pressure chamber pressure and the setforce of the timer piston return spring arebalanced (ie, in a stabilized condition).

Side view of timer



Servo valve setspring

Servo valve

Returnchannel


Highpressurechamber

Inlet channel

Top view of timer

Timer piston Low pressure chamber

Side view of timer



Servo valve setspring

Servo valve

Returnchannel

Cam ring


Highpressurechamber

Inlet channel

Top view of timer

Timer piston Lowpressurechamber

Return channel Open


Return channel Open


- 33 -

OPERATION

[2] TCV operation● The TCV acts as a variable throttle, using

the rapid opening and closing (cycling) ofthe valve needle in the TCV.At normal operation, the TCV influencescontrol pressure acting on the annularchamber so that the hydraulic stopper canbe freely set in any position, from the retardposition to the advance position. At this time,the duty ratio is set by the pump’s controlunit.

● Duty ratio is the ratio of the time that theTCV is open to one complete TCV operatingcycle. (A duty ratio change of 100% to 0%is an advance in injection timing.)

Duty ratio = t / T x 100%

P-VP4C-045

TCV

Annular chamber

Control signal Time

Closed

Open

T

t

● When control current flows to the TCV coil,the valve needle opens and the fuel in theannular chamber flows through the orificeto the feed pump inlet. Consequently, thepressure of the annular chamber decreasesand the hydraulic stopper is moved to theretard side.

● When control current to the TCV coil is cut,the valve needle closes and the returnpassage is closed. Consequently, thepressure of the annular chamber increasesand the hydraulic stopper is moved to theadvance side.

P-VP4C-052

Valve needle

To feed pump

From annular chamber Coil

Orifice

P-VP4C-053

Valve needle

From annular chamber

Hydraulic stopper

Returnpassage

Note:COVEC-F displays an OFF duty ratio, while theVP44 displays an ON duty ratio.

Open

Closed

- 34 -

OPERATION

Pulse count

Closed Open

Beginning ofpressure delivery

Pressure delivery�angle

End of pressuredelivery

Effective stroke

Cam

lift

Val

ve li

ft C

ontr

ol p

ulse

Ang

ular

enc

oder

sig

nal

4. ANGULAR ENCODERWhen the driveshaft rotates, the angularencoder receives signals from the sensor wheelteeth, and an electric pulse is sent through theflexible connecting harness to the pump controlunit.From these signals the pump control unit candetermine the average pump speed and themomentary pump speed.The angular encoder is mounted on a retainingring, which can rotate and is connected to thecam ring.Thus, the relationship between the cam ringcams and the angular encoder signal isconstant.The angular encoder signal is utilized for thefollowing purposes.● To determine the momentary angular

position of the cam ring● To calculate the actual speed of the fuel

injection pump● To determine the actual timer position

(1) Momentary cam ring angular positionThe momentary angular position of the cam ringis input into the pump control unit as a highpressure solenoid valve control signal. Frommomentary input of angular position forfluctuations in running conditions, the highpressure solenoid valve open and close intervalscorresponding to the cam ring’s cam lift can beaccurately determined.(2) Actual injection pump speedWhen the crankshaft speed sensor is faulty, theinjection pump speed signal serves as a spareengine control unit signal.(3) Actual timer positionThe actual timer position can be determined bycomparing the crankshaft speed sensor signalwith the angular encoder angle. This positionis used for timer control.

Example: Control signal generated to drive highpressure solenoid valve

Flexible connectingharnessAngular

encoder

Sensor wheel


Driveshaft

P-VP4C-054

P-VP4C-055

Sensorwheel

Angularencoder

Pumpcontrol

unit

・ Cam ring angle・ Pump speed・ Timer position

- 35 -

OPERATION

5. PUMP CONTROL UNIT

The radial plunger distributor type fuel injectionpump has two electronic control devices: thepump control unit and the engine control unit.The pump control unit receives signals from thesensors inside the pump for cam ring rotationangle and fuel temperature to determine enginecontrol unit set values, as well as injection timingand fuel injection quantity. The engine controlunit processes all engine data and dataregarding the surrounding environment receivedfrom external sensors to perform any engineside adjustments.Maps for the above are encoded in both controlunits.

The control units’ input circuits process sensordata. A microprocessor then determinesoperating conditions and calculates set signalsfor optimum running.The interchange of data between the enginecontrol unit and the pump control unit isperformed via a bus system (CAN: controllerarea network).By having two separate control units, the highpressure solenoid valve’s drive circuit can belocated near the solenoid valve to prevent thedischarge of any disturbing signals.

Engine control unit(ECU)

Pumpcontrol unit

(PCU)Fuel injection

pump(mechanical

section)

Injection timing

Injection quantity

Responsesignals

Additionalsignals

Engine speed

Accelerator pedal

Cooling watertemperature

Boost pressure

Air flow volume

Others

Sensor types

Additional operations

To high pressure solenoid valve

Timer controldevice

Cam ring rotational angleFuel temperature


To timer control device

Self diagnosis / interface / signal

Pub. No: EE14E-11130FUEL INJECTION PUMP MODEL VP44Service ManualConstruction & OperationPrinting: September 2000Published by:Bosch Automotive Systems CorporationService DepartmentPrinted in Japan

Copyright 2000,Bosch Automotive Systems Corporation

200-24

Printed on recycled paper

WPGES-01

C

vp44 co ee14e-11130

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