steering unit with switchable reaction - hydraulik nord...

Steering unit with switchable reaction

HE 11873 / 10.2017

Nominal sizes 50 – 400Series 1 xMaximum flow 50 l / min

Information sheet

Steering unit with switchable reaction | HE 11873 / 10.20172

Steering unit with switchable reaction | HE 11873 / 10.2017 3

© All rights with Hydraulik Nord Fluidtechnik GmbH & Co. KG, also in case of applications for industrial property protection. We retain all rights to disposal, copying and forwarding. The data provided only serves to describe the product. A statement about a certain property or suitability for a specific purpose cannot be derived from this information. The information does not relieve the user of his duty to carry out his own evaluations and tests. It should be noted that our products are subject to natural wear and aging.

Content

Features

Versions

Function

Application

Benefits

Page

4

4 – 5

6 – 7

8 – 9

10


1. Features

→ Can be switched between reaction and non-reaction → Full steering capabilities (normal and manual) in each mode→ For use in mobile work machines with Ackermann steering kinematics units and, in particular, automatic steering systems (GPS) → Can be switched by means of a solenoid valve between reaction, e. g. use on roads, and non-reaction e. g. for GPS steering mode or field work→ Emergency steering behaviour is maintained in both modes → Available as Open Center and Closed Center→ Compact design

2. Versions

OC = Open CenterLD = Closed Center

LAGC Baugröße OC LD

50

63

80

100

125

140

160

200

250

320

400

LAGZ Baugröße OC LD

125 / 60

140 / 80

160 / 60

160 / 80

190 / 60

200 / 80

220 / 60

240 / 80

260 / 60

300 / 100

420 / 100

The ordering codes of the steering units with switchable reaction mode are as similar as the standard LAGC or LAGZ. There is only a “SR” to add after the first “ .../ “ at the open center units or the SR is to add after the “...LD” at the closed center LD versions.

= Standard programme = Extended programme


If automatic steering systems are parallel aranged to the steering unit, it is important that the reaction mode of the hydrostatic steering unit is switched off in automatic steering mode. On the other hand the reaction mode is beneficial when the vehicle is on the road (driving straight, return to straight after cornering).

The general system is already used in GPS-controlled tractors. Existing solutions use additional valves to shut off the reaction steering. Those are located between the steering valve and the cylinders. (Fig. 4 page 8)

The HNF switchable steering units are a Plug & Play solutions without any further components. Hydraulic or electrical inter-faces are reduced. The steering capability with the steering wheel is completely retained in the reaction mode and also in the non-reaction mode. A solenoid valve is used to shut off the reaction mode. The attached valve plate and the solenoid valve create a 30 mm larger installation space.

Fig. 1: Steering system with switchable steering unit and automatic steering

1 Reaction steering unit2 Reaction shutoff valve3 Steering wheel angle sensor 1)

4 Automatic steering 1)

5 Steering angle sensor 1)

1) not included in delivery

P T

R L

Rx Lx

AchseU, I

Lenk

radU, I

Automatic steering


3. Function

→ Reaction steering unit→ Valve plate LVP with a reaction shutoff solenoid valve

Fig. 2: LVP (solenoid valve) switched

3.1 Servo mode manual controlled in reaction mode

→ The reaction shutoff valve is switched (see Fig. 2), the cylinder lines of the steering unit are open in the neutral position, and the reaction mode is active.→ In the reaction mode, both sides of the steering cylinder (L, R) are connected to the rotor set in the neutral position via the open cross sections of the rotary control valve.→ The tractive resistances that act on the wheels and effect a change of direction are transferred in a typical manner to the steering wheel (similar to a car or lorry steering unit).


Fig. 3: LVP (solenoid valve) not switched

3.2 Servo mode manual controlled in non-reaction mode

→ The reaction shutoff valve is not switched (current-free, see Fig. 3), the cylinder lines of the steering unit are closed in the neutral position, the reaction mode is deactivated. → The vehicle is steered with the steering unit in non-reaction mode.

3.3 Servo mode by GPS application

→ The reaction shutoff valve is not switched (current-free, see Fig. 3), the cylinder lines of the steering unit are closed in the neutral position, the reaction mode is deactivated→ The vehicle can be steered with the GPS-steering or the joystick without the steering wheel turning. → The manual steering mode on the steering wheel in non-reaction remains always activated during GPS or joystick steering. That is valid for the servo and for the emergency operation. → If the GPS navigation fails, the steering unit can override the GPS-steering system


4. Application

4.1 Steering unit with reaction and parallel arranged automatic steering based on the example of a GPS-controlled system (previous model)

1 Reaction steering unit2 Shutoff valve (reaction switching)3 Steering wheel angle sensor4 Automatic steering5 Steering angle sensor

P T

R L

Lenk

radU, I

AchseU,I

→ Figure 4 shows an example of a steering system – not using a switchable steering unit – comprising the hydrostatic steering unit with reaction (1) and an automatic steering system (4) that are arranged in parallel.→ The steering wheel angle sensor recognises whether the driver is using the steering wheel (manual control mode).→ Shutoff valves (2) are switched respective to the flow to and from the steering cylinder.→ When the automatic steering is used, the shutoff valve (2) blocks the steering cylinder lines to the steering unit (1) to shut off the reaction mode. As a result the steering unit is completely switched off.→ This is necessary so that the steering wheel does not turn when the automatic steering valves (4) is activated.→ This actuates the steering cylinder piston whose movement is detected by the steering angle sensor and is reported to a control unit.→ Automatic steering valve (4) is triggered by the GPS antenna and a control unit. (neither are shown in Fig. 4)→ Automatic steering valve (4) also processes the signals from the attached sensors.→ The vehicle is steered with the steering unit (1) in the manual controlled reaction steering mode when on the road. → When used off-road, the vehicle can be steered either with the steering unit (1) in the manual controlled reaction steering mode or with the automatic steering system. → If the GPS triggering fails, the steering capability of the steering unit can only be realized by switching the shutoff valves (2) in the cylinder lines return in the open position.

Fig. 4: Example of the steering unit (reaction) and automatic steering

Automatic steering


4. Application

4.2 Steering unit with switchable reaction and automatic steering

→ Figure 5 shows an example of a steering system comprising the hydrostatic steering unit with reaction (1) and an automatic steering system (4) that are arranged in parallel→ The steering wheel angle sensor recognises whether the driver is using the steering wheel (manual control mode)→ The vehicle can be steered with the steering unit (1) in the manual controlled reaction steering mode or non-reaction when on the road → When used off-road, the vehicle can be steered either with the steering unit (1) in the manual controlled reaction or non-reaction steering modes or with the automatic steering system (4) + non-reaction mode→ Only the reaction shutoff valve (2) is required for switching the steering modes → If the GPS triggering fails, the vehicle can always be steered in manual controlled steering mode, shutoff valves are not required in the cylinder lines

Fig. 5: Example of a steering unit (switchable reaction) and automatic steering in the neutral position

P T

R L

Rx Lx

AchseU, I

Lenk

radU, I

1 Reaction steering unit2 Reaction shutoff valve3 Steering wheel angle sensor 1)

4 Automatic steering 1)

5 Steering angle sensor 1)

1) not included in delivery

Automatic steering


5. Benefits

→ The manual controlled steering mode of the steering unit with a switchable reaction is always available, even in non-reaction mode

→ Steering units with a switchable reaction are an inexpensive solution to previous models. Instead of shutoff valves in the cylinder lines, a reaction shutoff valve deactivates the reaction

behaviour directly on the steering unit and the non-reaction mode is available.

→ No monitoring scenarios are required. The vehicle can always be steered with the steering wheel.

→ Reduces the risk of failures and also the assembly and logistics effort


6. Notes

HYDRAULIK NORD FLUIDTECHNIK GmbH & Co. KG Ludwigsluster Chaussee 5, 19370 Parchim www.hn-group.com

steering unit with switchable reaction - hydraulik nord...

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