Modulator Unit
The modulator unit consists of the inlet solenoid valve, the outlet solenoid valve, the VSA NO (normally open) solenoid valve, the VSA NC (normally closed) solenoid valve, the reservoir, the pump, and the pump motor.
The hydraulic control has three modes of ABS action; pressure intensifying, pressure retaining, and pressure reducing. Pressure intensifying mode (VSA) is a combination of the TCS, VSA, and brake assist action.
The hydraulic circuit is an independent four channel type; one channel for each wheel.
Mode
VSA NO Valve
VSA NC Valve
Inlet Solenoid Valve
Outlet Solenoid Valve
Brake Fluid
Pressure intensifying mode
open
closed
open
closed
Master cylinder fluid is pumped out to the caliper.
Pressure retaining mode
open
closed
closed
closed
Caliper fluid is retained by the inlet and outlet valves.
Pressure reducing mode
open
closed
closed
open
  • Caliper fluid flows through the outlet valve to the reservoir.
  • The motor pumps the reservoir fluid through the damping chamber to the master cylinder * .
Pressure intensifying mode (VSA)
closed
open
open
closed
  • Master cylinder fluid is pumped out by pump with motor through VSA NC valve to the caliper.
  • Caliper fluid pressure exceeds master cylinder pressure.

*:
The motor will continue running until the operation of the one anti-lock brake control is finished with the first pressure reducing mode.