Description

Item Component

922-3 Hydraulic trailer brake measuring point 922-4 Service brake measuring point

Y106 Parking brake solenoid valve

Z12 Parking brake actual value switch Z81 Service brake pressure actual value switch Z102-2 Steering hydraulics filter bypass actual value switch (bypass open) Z104 Brake accumulator pressure actual value switch

Description

Oil supply The oil supply is by the steering hydraulics pump (218). The volume flow flows to the EHL valve block (VI), opens the non-return valve (731-1) and is fed into the main brake valve (VII) at port (P). When the accumulator pressure in the accumulators (516) drops below 125 bar, the charge valve (784) moves to the position shown and directs the control pressure to the volume flow controller (772) of the steering hydraulics pump (218). The steering hydraulics pump (218) swivels out and pumps volume flow into the brake system (loading). This makes the hydraulic pressure rise; when the operating pressure of 150 bar has been reached, the charge valve (784) relieves the control pressure to the tank and the entire volume flow is available for steering hydraulics. In order to feel the brake pressure generated, a feedback to the service brake valve (642) against the pedal force results from the actuation (brake pedal). When a pressure of 5 bar (Z80) is present in the brake circuit, the signal is transmitted to the drive control unit. Measuring point XP-BR This measuring point is used for measuring the pressure during charging of the brake system.

Recharging the accumulator manually

–Diesel engine OFF. –Wheels in straight-ahead position.Do not turn the steering wheel during the measurement. –Install pressure gauge (0 to 200 bar) into the measuring point (XP-BR). –Press the service brake pedal about 10 times. The accumulators are now discharged. –Start the diesel engine.Now volume flow is fed into the main brake valve (VII). The pressure rises to approx. 150 bar. When the accumulators are filled, the pressure drops to 25+2 bar. Parking brake Parking brake solenoid valve (Y106) not energised = Parking brake is actuated. The parking brake is closed by belleville springs.Parking brake solenoid valve (Y106) energised = Parking brake is not actuated. When the parking brake solenoid valve (Y106) is energised, the applied volume flow (P) is directed to the parking brake hydraulic cylinder (3008). This acts against the belleville springs and opens the parking brake. Service brake The service brakes are actuated by the hydraulic cylinders (3007) in the wheel hubs. Control is modulated via the brake valve (642) which is actuated by the service brake pedal.

The floating axle (1) and the rigid axle (2) have separate brake circuits. A shuttle valve allows using the highest of the two pressure values for controlling the trailer brake valve (783). The highest brake pressure can be measured at measuring point (922-3). The maximum brake pressure is to be 85+10 bar (factory setting). This adjustment is made on the adjusting bolt (E). Pressure accumulator The accumulators (516) for the service brake and (519) for the parking brake contain the energy necessary for braking (pressure). With each braking, the pressure in the accumulators drops - they are discharged. The hydraulic pressure (accumulator charge) can be measured at measuring point (922-4). This is monitored by switch (Z104). The brake accumulator warning signal is fed into the CEBIS terminal (see electric system). Input pressure balance (763) not used.