Antilock Control: Description and Operation
Anti-Lock ControlWARNING: Brake fluid contains polyglycol ethers and polyglycols. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts the eyes, flush the eyes with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately. Failure to follow these instructions may result in personal injury.
CAUTION: Use of any other than approved DOT brake fluid will cause permanent damage to brake components and will render the brakes inoperative.
CAUTION: Brake fluid is harmful to painted or plastic surfaces. If brake fluid is spilled onto a painted or plastic surface, immediately rinse it off with water.
The anti-lock brake system operates as follows:
^ Wheel lock-up is prevented during heavy braking by modulating brake pressure.
^ The system permits the driver to maintain steering control and stop the vehicle in the shortest possible distance under most conditions.
^ During the anti-lock brake operation, the driver will sense a pulsation in the brake pedal and hear a clicking sound.
^ The pedal effort and pedal feel during normal braking are similar to that of a conventional power brake system.
Hydraulic and Electronic Control
The hydraulic and electronic control consists of the Hydraulic Control Unit (HCU) and the anti-lock brake system (ABS) module which is an integrated unit.
The HCU consists of an aluminum block containing solenoid valves and a pump motor.
The ABS module consists of a printed circuit board with microprocessors, integrated software and the magnetic coils for driving the solenoid valves in the HCU.
Wheel Speed Sensors
Active wheel speed sensors consist of:
^ four wheel speed sensors, located at each wheel, containing a small processor for sending a digital signal to the ABS module
^ an encoder ring with a magnetic profile embedded within the material
Electronic Brake Distribution
Electronic Brake Force Distribution (EBD) takes the place of Pressure-Conscious Regulators (PCRVs) used in conventional braking systems and is featured in all ABS/TCS systems.
The EBD function is an additional program (software) to the conventional ABS program that allows greater utilization of the rear brakes up to the point of ABS intervention.
EBD can come into operation during regular braking, dependent on the loading of the vehicle and the surface friction. Brake force is determined during EBD control.
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