Valve Operation (Abs Function And EBD Function)
The following descriptions explains the control of front brake right side, as an example.
Under Normal Brake Operation
Since power is not supplied to the ABS IN valve and the ABS OUT valve, the ABS IN valve port is open and the ABS OUT valve port is closed. This allows the master cylinder fluid pressure to be sent to the front RH caliper and blocks the brake fluid passage to the reservoir.
When Pressure Increases
The control unit pressurizes the inside of the brake caliper by opening the ABS IN valve port and closing the ABS OUT valve port. After breaking the circuit, the valves operate in the same way as described in "Under Normal Brake Operation." The fluid amount supplied from the master cylinder to the brake caliper is controlled, according to the power supply cut-off time (time to open the port) to the ABS IN valve.
When Pressure Holds
The control unit passes an electric current to the ABS IN valve and closes the ABS IN valve port. Since power is not supplied to the ABS OUT valve, its port is closed. The paths to the brake caliper, master cylinder, and reservoir are cut off. This allows the front RH caliper fluid pressure to be maintained.
When Pressure Decreases
The control unit closes the ABS IN valve port and opens the ABS OUT valve port by supplying power to the ABS IN valve and the ABS OUT valve. The brake fluid of the front RH caliper passes through the ABS OUT valve to the reservoir and stays in the reservoir. After this the brake fluid is pumped up to return to the master cylinder.
When brake released
The fluid pressure returns from the front RH caliper to the master cylinder through the return check valve opened by the ABS IN valve port and fluid pressure.
Component Parts and Function
| Component | Function |
|---|---|
| Pump | Feeds brake fluid by the motor. |
| Motor | Activates the pump according to signals from ABS actuator and electric unit (control unit). |
| ABS IN valve | Switches the fluid pressure line to increase or hold according to signals from control unit. |
| ABS OUT valve | Switches the fluid pressure line to increase, hold or decrease according to signals from control unit. |
| Cut valve 1 Cut valve 2 |
Shuts off the ordinary brake line from master cylinder, when VDC function, TCS function and brake limited slip differential (BLSD) function are activated. |
| Suction valve 1 Suction valve 2 |
Supplies the brake fluid from master cylinder to the pump, when VDC function, TCS function and brake limited slip differential (BLSD) function are activated. |
| Inlet valve | Brake fluid sucked from the reservoir by the pump does not backflow. |
| Outlet valve | Brake fluid discharged from the pump does not backflow. |
| Return check valve | Returns the brake fluid from brake caliper and wheel cylinder to master cylinder by bypassing orifice of each valve when brake is released. |
| Pressure sensor | Detects the brake fluid pressure and transmits signal to control unit. |
| Reservoir | Temporarily reserves the brake fluid drained from brake caliper, so that pressure efficiently decreases when decreasing pressure of brake caliper and wheel cylinder. |
| Damper | Reduces the vibrations travelling to the brake pedal during the operation of the VDC function, TCS function, ABS function, EBD function, or brake limited slip differential (BLSD) function. |