ABS Components

System Description (cont'd)

 19-66  

ABS Modulator

The ABS modulator consists of the inlet solenoid valve, outlet solenoid valve, reservoir, pump, pump motor and the damping chamber. The modulator reduces the calliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates through the calliper, reservoir and the master cylinder. The hydraulic control has three modes: pressure intensifying, pressure retaining and pressure reducing. The hydraulic circuit is an independent four-channel type, one channel for each wheel.

ABS MODULATOR-CONTROL UNIT

  1. MODULATOR UNIT
  2. PUMP MOTOR
  3. ABS CONTROL UNIT

IN: INLET VALVE (NORMALLY OPEN)

OUT: OUTLET VALVE (NORMALLY CLOSED)

Pressure intensifying mode: Inlet valve open, outlet valve closed
  Master cylinder fluid is pumped out to the calliper.
Pressure retaining mode: Inlet valve closed, outlet valve closed
  Calliper fluid is retained by the inlet valve and outlet valve.
Pressure reducing mode: Inlet valve closed, outlet valve open
  Calliper fluid flows through the outlet valve to the reservoir.
Motor operation mode: When starting the pressure reducing mode, the pump motor is ON.
  When stopping ABS operation, the pump motor is OFF.
  The reservoir fluid is pumped out by the pump, through the damping chamber, to the master cylinder.