10-10
▶Pressure Decreases in the Circuit when ABS is Operating
Even when the hydraulic pressure on each circuit is stable, the wheel can be locked as the wheel
speed decreases. This is when the ABS ECU detects the wheel speed and the vehicle speed and
gives the optimized braking without locking the wheels. In order to prevent from hydraulic pressure
increases, the inlet valve is closed and the outlet valve is opened. Also, the oil is sent to the low
pressure changer and the wheel speed increases again. The ABS ECU operates the pump to circulate
the oil in the low pressure chamber to the master cylinder. This may make the driver to feel the brake
pedal vibration and some noises.
▶Pressure Increases in the Circuit when ABS is Operating
As the wheel speed increases, the inlet valve opens and the wheel’s pressure increases due to
the master cylinder pressure. The oil in the low pressure chamber circulates to the wheel by the pump
and the wheel speed decreases as the hydraulic pressure at wheel increases. This operation
continues repetitively until there are no signs that the ECU is locking the wheels. When the ABS
hydraulic pressure control takes place, there may be some vibration and noises at the brake pedal.
