GF32.50-P-4202R ABC Front Axle Valve Unit, Component Description

GF32.50-P-4202R ABC front axle valve unit, component description
- with CODE (487) Active body control (ABC)
- as of 1.3.06 up to model year 08

Component Identification:

Location
The ABC front axle valve unit is located at left front next to the washer fluid reservoir.

Design
The following valves and sensors are integrated in the ABC front axle valve unit:

^ Right front suspension strut control valve (Y36/1y3)
^ Left front suspension strut control valve (Y36/1y1)
^ Left front suspension strut blocking valve (Y36/1y2)
^ Right front suspension strut blocking valve (Y36/1y4)
^ ABC pressure sensor (B4/5)
^ Left front ABC pressure sensor (B4/8)
^ Right front ABC pressure sensor (B4/9)

Left front suspension strut control valve and right front suspension strut control valve

Task
The control valves (linear motor valves) are used to adjust the hydraulic suspension struts and to control the flow of oil.

Function
The valves are 3/3-way valves. To reduce leakage, the valves are equipped with a valve actuator cover at the center position. The valve is a linear motor valve which is closed when de-energized (center position of the double-spring-loaded valve actuator).

If the valve is energized, oil is supplied to the suspension strut from the oil feed pressure circuit (suspension strut extends). If, however, the flow direction of the electric current is changed, the valve actuator moves across the center position in the other direction and allows oil to flow back out of the respective suspension strut and into the return circuit (suspension strut retracts).

The ABC control unit (N51/2) needs four current-controlled output stages in a H-bridge circuit to actuate the control valves. Current control is intended to reduce the power loss and is achieved by means of pulse-width-modulated (PWM) actuation.

An overload diode is fitted in the control unit for the OFF phase of PWM actuation. The valves can be deactivated redundantly if PWM actuation should fail.

Left front suspension strut blocking valve and right front suspension strut blocking valve

Task
The left front suspension strut blocking valve and right front suspension strut blocking valve are required for the safety concept. They prevent the vehicle, when not in use, from being lowered or raised as a result of residual leakage of the control valves.

Function
The left front suspension strut blocking valve and right front suspension strut blocking valve are closed when de-energized. Since the valves are permanently open under normal operating conditions (i.e. energized), a current-controlled valve output stage is provided in the control unit in order to reduce the power loss at the valves. When the valves are switched on (opened), they are supplied with increased current for a certain period of time (push phase). The current is then reduced to the holding current.

A redundant shutdown circuit is provided for the valves. The valves can also be shut down.