GF42.40-W-0003D | Acceleration slip regulation (ASR), function | 25.10.06 |
MODEL 374.6, 375.4, 940, 942, 943, 944, 950.5 /6, 952.5 /6, 953.6, 954.5
with CODE (BB8) Brake control (BS) with ASR
with CODE (ZX2) EPB II
MODEL 970, 972, 974, 975, 976
with CODE (BB1) Brake control (BS)
with CODE (ZX2) EPB II
MODEL 970, 972, 974, 975, 976
with CODE (BB8) Brake control (BS) with ASR
with CODE (ZX2) EPB II
W42.40-1005-79
12.07 Brake wear sensor
12.08 Rpm sensor
13.08 Central Brake Unit (CBU)
22.01 Combination brake cylinder
24.04 Pressure ratio valve
28.04 Double check valve
31.13 Drive axle axle modulator
33.08a 3/2-way air admission valve
V1 System pressure (circuit 1)
CAN 1 Vehicle CAN
CAN 4 Engine CAN
CAN 6 Brakes CAN
a System pressure
b Brake pressure
c Redundant brake pressure
d Control pressure
A110a1 Brake system (BS) control unit
A3 Drive control (FR) control unit
A6 Engine control (MR) control unit
AV Outlet valve
D Pressure sensor
EV Inlet valve
RD Redundancy valve
RE Control electronics
RV Relay valve
General
The acceleration slip regulation (ASR) attempts to prevent the drive wheels from spinning when grip is lost.
The function of the acceleration slip regulation (ASR) is integrated in the brake system (BS) control unit (A110a1).
ASR engine intervention
From the signals of the rpm sensors (12.08) the drive axle axle modulator (31.13) detects any tendency of the drive wheels to slip and forwards this information to the brake system (BS) control unit (A110a1) for evaluation. In order to reduce the drive slip, the brake system (BS) control unit (A110a1) authorizes a reduction in engine torque via the engine control (MR) control unit (A6).
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Selective ASR brake intervention
From the signals of the rpm sensors (12.08) the drive axle axle modulator (31.13) detects any tendency of a drive wheel to slip and forwards this information to the brake system (BS) control unit (A110a1) for evaluation.
Via the drive axle axle modulator (31.13) the brake system (BS) control unit (A110a1) authorizes an appropriate brake pressure (b) to be sent to the drive wheel that is tending to slip.
The data exchange occurs via the brakes CAN (CAN 6).
Leading and trailing axles are regulated together with the drive axle brake control, but should not be braked when ASR regulation is active. So the drive axle axle modulator (31.13) actuates the 3/2-way air admission valve (33.08a), which holds back the brake pressure (b) via double check valves (28.04).
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ASR shutoff
The acceleration slip regulation (ASR) can be shut off using the ASR cutout button in order to improve traction, e.g. in of-road operations.
The ASR indicator lamp in the Instrument (INS) lights up when ASR control is switched off or during ASR intervention. The function is reactivated automatically when the ignition is switched off and on again.