BRAKE CONTROL SYSTEM DETAILS BRAKE CONTROL

OPERATION

1. Engine Output Control during TRC or VSC Operation

   1. During the TRC or VSC operation, the skid control ECU outputs the engine output control signal to the ECM. Upon receiving this signal, the ECM inhibits the engine output.

      

2. ABS with EBD

   1. Based on the signals received from the 4 speed sensors, the skid control ECU calculates each wheel speed and deceleration, and checks wheel slipping conditions. According to the slipping condition, the skid control ECU controls each pressure holding valve and pressure reduction valve in order to adjust the fluid pressure of each wheel cylinder in the following 3 modes: pressure reduction, pressure holding and pressure increase modes.

      

      *1	Port A	*2	Port B
      *3	Pressure Holding Solenoid Valve	*4	Pressure Reduction Solenoid Valve
      *a	Increase Mode	*b	Holding Mode
      *c	Reduction Mode	*d	to Wheel Cylinder
      *e	to Reservoir and Pump	*f	from Wheel Cylinder

      Not Activated	Normal Braking	-	-
      Activated	Increase Mode	Holding Mode	Reduction Mode
      Pressure Holding Solenoid Valve (Port A)	OFF (Open)	ON (Close)	ON (Close)
      Pressure Reduction Solenoid Valve (Port B)	OFF (Close)	OFF (Close)	ON (Open)
      Wheel Cylinder Pressure	Increased	Held	Reduced

3. Brake Assist

   1. In the event of emergency braking, the skid control ECU determines the driver's intentions based on the speed of the pressure increase in the master cylinder detected by the master cylinder pressure sensor signal. If the skid control ECU judges the need for additional brake assist, pressure to supplement the amount provided by the master cylinder is generated by the pump in the brake actuator and directed to each wheel cylinder.

      

      

      *1	Brake Master Cylinder Sub-assembly	*2	Brake Actuator Assembly
      *3	Master Cylinder Pressure Sensor	*4	Pump
      *5	Reservoir	*6	Front Brake Caliper (Left Side)
      *7	Rear Brake Caliper (Right Side)	*8	Rear Brake Caliper (Left Side)
      *9	Front Brake Caliper (Right Side)	-	-

   2. Each valve operates as shown below:

      Item			Port	Brake Assist Not Activated	Brake Assist Activated
      Master Cylinder Cut Solenoid Valve		(1), (4)	(A), (D)	OFF (Open)	ON*
      Reservoir Cut Solenoid Valve		(2), (3)	(B), (C)	OFF (Closed)	ON (Open)
      Front Brakes	Pressure Holding Solenoid Valve	(5), (8)	(E), (H)	OFF (Open)	OFF (Open)
      	Pressure Reduction Solenoid Valve	(9), (12)	(I), (L)	OFF (Closed)	OFF (Closed)
      Rear Brakes	Pressure Holding Solenoid Valve	(6), (7)	(F), (G)	OFF (Open)	OFF (Open)
      	Pressure Reduction Solenoid Valve	(10), (11)	(J), (K)	OFF (Closed)	OFF (Closed)
      Pump				OFF	ON

      *: Hydraulic pressure is controlled by continuously cycling the solenoid valves between open and closed, according to the operating conditions.

4. TRC

   1. The fluid pressure generated by the pump is regulated by the master cylinder cut solenoid valve to achieve the required pressure. Thus, the brakes for the drive wheels are controlled in the following 3 modes: pressure reduction, pressure holding, and pressure increase modes, to control slippage of the drive wheels.

   2. The diagram shows the hydraulic circuit in pressure increase mode when TRC is activated. Each pressure holding solenoid valve and pressure reduction solenoid valve is turned ON/OFF according to the ABS and EBD operation pattern.

      

      

      *1	Brake Master Cylinder Sub-assembly	*2	Brake Actuator Assembly
      *3	Master Cylinder Pressure Sensor	*4	Pump
      *5	Reservoir	*6	Front Brake Caliper (Left Side)
      *7	Rear Brake Caliper (Right Side)	*8	Rear Brake Caliper (Left Side)
      *9	Front Brake Caliper (Right Side)	-	-

   3. Each valve operates as shown below:

      Item			Port	TRC Not Activated	TRC Activated
      					Increase Mode	Holding Mode	Reduction Mode
      Master Cylinder Cut Solenoid Valve		(1), (4)	(A), (D)	OFF (Open)	ON*	ON*	ON*
      Reservoir Cut Solenoid Valve		(2), (3)	(B), (C)	OFF (Closed)	ON (Open)	ON (Open)	ON (Open)
      Front Brakes	Pressure Holding Solenoid Valve	(5), (8)	(E), (H)	OFF (Open)	OFF (Open)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(9), (12)	(I), (L)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      	Brake Wheel Cylinder Pressure	-	-	-	Increased	Held	Reduced
      Rear Brakes	Pressure Holding Solenoid Valve	(6), (7)	(F), (G)	OFF (Open)	ON (Closed)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(10), (11)	(J), (K)	OFF (Closed)	ON (Open)	ON (Open)	ON (Open)
      	Brake Wheel Cylinder Pressure	-	-	-	-	-	-
      Pump				OFF	ON	ON	ON

      *: Hydraulic pressure is controlled by continuously cycling the solenoid valves between open and closed, according to the operating conditions.

5. VSC

   1. VSC, by way of solenoid valves, controls fluid pressure generated by the pump and applies it to each wheel cylinder in the following 3 modes: pressure reduction, pressure holding, and pressure increase modes. As a result, understeer and oversteer tendencies are controlled.

      

   2. In understeer restraining control, the skid control ECU controls engine output and applies the brakes of the front and rear wheel on the inside of the turn. Also, depending on whether the brakes are applied and the vehicle condition, there are circumstances in which the brake of a specific wheel may not be applied even if it was targeted for braking. The diagram below shows the hydraulic circuit in pressure increase mode, as it restrains an understeer tendency while the vehicle is making a right turn. In other operating modes, each pressure holding solenoid valve and pressure reduction solenoid valve is turned ON/OFF according to the ABS and EBD operation pattern.

      

      *1	Brake Master Cylinder Sub-assembly	*2	Brake Actuator Assembly
      *3	Master Cylinder Pressure Sensor	*4	Pump
      *5	Reservoir	*6	Front Brake Caliper (Left Side)
      *7	Rear Brake Caliper (Right Side)	*8	Rear Brake Caliper (Left Side)
      *9	Front Brake Caliper (Right Side)	-	-

   3. Each valve operates as shown below:

      Item			Port	VSC Not Activated	VSC Activated
      					Increase Mode	Holding Mode	Reduction Mode
      Master Cylinder Cut Solenoid Valve		(1), (4)	(A), (D)	OFF (Open)	ON*	ON*	ON*
      Reservoir Cut Solenoid Valve		(2), (3)	(B), (C)	OFF (Closed)	ON (Open)	ON (Open)	ON (Open)
      Front Brake	Pressure Holding Solenoid Valve	(5)	(E)	OFF (Open)	ON (Closed)	ON (Closed)	ON (Closed)
      		(8)	(H)	OFF (Open)	OFF (Open)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(9)	(I)	OFF (Closed)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      		(12)	(L)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      	Brake Wheel Cylinder Pressure	Right	-	-	Increased	Held	Reduced
      		Left	-	-	-	-	-
      Rear Brake	Pressure Holding Solenoid Valve	(6)	(F)	OFF (Open)	OFF (Open)	ON (Closed)	ON (Closed)
      		(7)	(G)	OFF (Open)	ON (Closed)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(10)	(J)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      		(11)	(K)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      	Brake Wheel Cylinder Pressure	Right	-	-	Increased	Held	Reduced
      		Left	-	-	-	-	-
      Pump				OFF	ON	ON	ON

      *: Hydraulic pressure is controlled by continuously cycling the solenoid valves between open and closed, according to the operating conditions.

   4. In oversteer restraining control, the skid control ECU applies the brakes of the front and rear wheels on the outside of the turn. Also, depending on whether the brakes are applied and the vehicle condition, the brake of a specific wheel may not be applied even if it was targeted for braking. The diagram below shows the hydraulic circuit in pressure increase mode, as it restrains an oversteer tendency while the vehicle is making a right turn. In other operating modes, each pressure holding solenoid valve and pressure reduction solenoid valve is turned ON/OFF according to the ABS and EBD operation patterns.

      

      *1	Brake Master Cylinder Sub-assembly	*2	Brake Actuator Assembly
      *3	Master Cylinder Pressure Sensor	*4	Pump
      *5	Reservoir	*6	Front Brake Caliper (Left Side)
      *7	Rear Brake Caliper (Right Side)	*8	Rear Brake Caliper (Left Side)
      *9	Front Brake Caliper (Right Side)	-	-

   5. Each valve operates as shown below:

      Item			Port	VSC Not Activated	VSC Activated
      					Increase Mode	Holding Mode	Reduction Mode
      Master Cylinder Cut Solenoid Valve		(1), (4)	(A), (D)	OFF (Open)	ON*	ON*	ON*
      Reservoir Cut Solenoid Valve		(2), (3)	(B), (C)	OFF (Closed)	ON (Open)	ON (Open)	ON (Open)
      Front Brake	Pressure Holding Solenoid Valve	(5)	(E)	OFF (Open)	OFF (Open)	ON (Closed)	ON (Closed)
      		(8)	(H)	OFF (Open)	ON (Closed)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(9)	(I)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      		(12)	(L)	OFF (Closed)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      	Brake Wheel Cylinder Pressure	Right	-	-	-	-	-
      		Left	-	-	Increased	Held	Reduced
      Rear Brake	Pressure Holding Solenoid Valve	(6)	(F)	OFF (Open)	ON (Closed)	ON (Closed)	ON (Closed)
      		(7)	(G)	OFF (Open)	OFF (Open)	ON (Closed)	ON (Closed)
      	Pressure Reduction Solenoid Valve	(10)	(J)	OFF (Closed)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      		(11)	(K)	OFF (Closed)	OFF (Closed)	OFF (Closed)	ON (Open)
      	Brake Wheel Cylinder Pressure	Right	-	-	-	-	-
      		Left	-	-	Increased	Held	Reduced
      Pump				OFF	ON	ON	ON

      *: Hydraulic pressure is controlled by continuously cycling the solenoid valves between open and closed, according to the operating conditions.

6. Hill-start Assist Operation

   1. When Hill-start Assist Control is operating, the skid control ECU holds the brake fluid pressure.

   2. Based on the information provided by various sensors, switches, and the ECM, the skid control ECU determines whether to activate hill-start assist control.

   3. During hill-start assist control, the stop lights are illuminated.

      

      

      *1	Brake Master Cylinder Sub-assembly	*2	Brake Actuator Assembly
      *3	Master Cylinder Pressure Sensor	*4	Pump
      *5	Reservoir	*6	Front Brake Caliper (Left Side)
      *7	Rear Brake Caliper (Right Side)	*8	Rear Brake Caliper (Left Side)
      *9	Front Brake Caliper (Right Side)	-	-

      Item			Port	Not Activated	Hill-start Assist Control Activated
      					Holding Mode	Reduction Mode
      Master Cylinder Cut Solenoid Valve		(1), (4)	(A), (D)	OFF (Open)	ON*	ON*
      Reservoir Cut Solenoid Valve		(2), (3)	(B), (C)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      Front Brakes	Pressure Holding Solenoid Valve	(5), (8)	(E), (H)	OFF (Open)	OFF (Open)	OFF (Open)
      	Pressure Reduction Solenoid Valve	(9), (12)	(I), (L)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      	Brake Wheel Cylinder Pressure		-	-	Hold	Reduce
      Rear Brakes	Pressure Holding Solenoid Valve	(6), (7)	(F), (G)	OFF (Open)	OFF (Open)	OFF (Open)
      	Pressure Reduction Solenoid Valve	(10), (11)	(J), (K)	OFF (Closed)	OFF (Closed)	OFF (Closed)
      	Brake Wheel Cylinder Pressure		-	-	Hold	Reduce
      Pump				OFF	OFF	OFF

      *: Hydraulic pressure is controlled by continuously cycling the solenoid valves between open and closed, according to the operating conditions.