BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Brake Booster with Master Cylinder Assembly Skid Control ECU

    • Operates the brake actuator assembly and brake actuator to control the brake fluid pressure of each wheel based on signals from each sensor and ECU.

    • Performs regenerative cooperative brake control by communicating with each ECU.

    • Sends an emergency braking signal request signal to the stop light control relay based on signals received from each sensor and the operation of the brake pedal.
    Master Cylinder Generates brake fluid pressure in accordance with the depression amount of the brake pedal.
    Stroke Simulator Generates a natural brake pedal feel in response to depression of the brake pedal by the driver.
    Brake Master Cylinder Reservoir Assembly Brake Fluid Level Warning Switch Detects when the brake fluid level is low.
    Brake Actuator Regulator

    • Supplies pressurized brake fluid which is controlled by the linear solenoid valve to the servo chamber when the skid control ECU is operating.

    • Supplies brake fluid pressure from the accumulator to the servo chamber when the skid control ECU is not operating or during back-up when the skid control ECU is malfunctioning.
    Linear Solenoid Valve (SLA, SLR) Adjusts the regulator to control the servo pressure as requested.
    Gap Hold Valve (SGH)

    • During normal control, transmits the brake fluid pressure generated by the depression of the brake pedal by the driver to the stroke simulator.

    • During a malfunction, seals the brake fluid pressure of the gap hold chamber.
    Stroke Simulator Cut Valve (SSA) Allows the stroke simulator pressure to flow to the brake master cylinder reservoir assembly such as when the system is malfunctioning.
    Relief Valve Opens to prevent excessive fluid pressure if the pump motor operates continuously such as during a malfunction of the accumulator pressure sensor.
    Accumulator Pressure Sensor(Pacc) Detects the accumulator brake fluid pressure and is used to control the pump motor.
    Servo Pressure Sensor(Psrv) Detects the fluid pressure of the servo chamber.
    Stroke Simulator Pressure Sensor(Prct) Detects the brake fluid pressure in the stroke simulator which is generated by the depression of the brake pedal by the driver.
    Brake Actuator Assembly Independently controls the brake fluid pressure of the 4 wheels when ABS, TRC, VSC, etc. is operating.
    Brake Booster Pump Assembly Pump Motor Pumps the brake fluid from the brake master cylinder reservoir assembly to the accumulator.
    Accumulator Accumulates brake fluid supplied by the pump motor under pressure.
    Speed Sensor Detects the wheel speed of each of the 4 wheels.
    Airbag Sensor Assembly Yawrate Sensor Detects the angular velocity of the vehicle.
    Acceleration Sensor Detects the longitudinal and lateral acceleration of the vehicle.
    Steering Sensor Detects the steering direction and angle of the steering wheel.
    Stop Light Switch Assembly Detects when the brake pedal is depressed.
    Combination Switch Assembly VSC OFF Switch Disables TRC and VSC functions when pressed.
    Brake Pedal Stroke Sensor Assembly Detects the stroke distance of the brake pedal.
    Front Door Courtesy Light Switch Assembly (Driver Side) Outputs whether the driver door is open or closed to the skid control ECU.
    Parking Brake Switch Assembly Outputs the parking brake operation status to the main body ECU (multiplex network body ECU).
    Hybrid Vehicle Control ECU Controls the regenerative braking force via communication with the skid control ECU during regenerative cooperative braking. Also, controls drive force when TRC or VSC is operating.
    Inverter with Converter Assembly MG ECU Sends information regarding the motor to the skid control ECU during regenerative cooperative braking.
    ECM Controls the engine output based on signals received from the hybrid vehicle control ECU.
    Main Body ECU (Multiplex Network Body ECU) Sends the parking brake status signal to the skid control ECU via CAN communication.
    Power Steering ECU Assembly Controls the steering assist torque based on signals received from the skid control ECU during steering cooperative control.
    Driving Support ECU Assembly* Sends brake request signals to the skid control ECU.
    Network Gateway ECU Relays data between buses.

    *: Models with pre-crash safety system

  2. FAIL-SAFE


    1. If a malfunction is detected in the brake system, the fail-safe function operates. Depending on the type of malfunction, the fail-safe function informs the driver via warning indicators in the combination meter assembly and continues brake control via the use of non-malfunctioning parts. Also, when the system is not operating, the fluid pressure generated in the brake master cylinder by the depression of the brake pedal works as a back-up mechanism to ensure braking force.

  3. DIAGNOSIS


    1. A diagnosis function is provided in consideration of serviceability in order to simplify the inspection of systems. For details of the diagnosis function, refer to Repair Manual.