ELECTRONICALLY CONTROLLED BRAKE SYSTEM SYSTEM DESCRIPTION


  1. FUNCTION DESCRIPTION


    1. Electronically Controlled Brake System


      1. The electronically controlled brake system detects the amount that the brake pedal is depressed based on signals from the brake pedal stroke sensor. The system uses the skid control ECU to adjust the pressure supplied from the hydraulic pressure source for each wheel, generating optimal braking force.

    2. Regenerative Braking Cooperative Control


      1. This control performs cooperative control with regenerative braking that is specific to hybrid vehicles to efficiently charge the HV battery.

    3. Vehicle Dynamics Integrated Management (VDIM)


      1. VDIM integrates hybrid drive brake control (ABS with EBD, BA, TRC, VSC and hill-start assist control) and steering assist control to enhance active safety when accelerating, turning and stopping.

    4. Steering Cooperation Control


      1. Performs cooperative control with the power steering ECU in order to provide steering torque assist in accordance with present vehicle dynamics.

    5. Anti-lock Brake System (ABS)


      1. The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.

    6. Electronic Brake force Distribution (EBD)


      1. EBD control utilizes the ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, when braking while cornering, it also controls the brake force applied to the right and left wheels, helping to stabilize vehicle behavior.

    7. Brake Assist (BA)


      1. The primary purpose of brake assist is to provide supplementary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping ensure the vehicles braking performance.

    8. Traction Control (TRC)


      1. The TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.

    9. Vehicle Stability Control (VSC)


      1. The VSC helps restraint sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid, such as may occur while cornering.

    10. Hill-start Assist Control


      1. The hill-start assist control generates four-wheel hydraulic pressure when the brake pedal is further depressed while the vehicle is stationary in order to prevent the vehicle from moving backward.

    11. Limited Slip Differential (LSD) Function


      1. The LSD function detects the vehicles turning condition and wheel slippage. Brake force is then applied to the inner wheels to limit slippage and transmit power to the outer wheels, ensuring acceleration performance while turning.

    12. Emergency Brake Signal (w/ Emergency Brake Signal)


      1. In the case of emergency braking, emergency stop light control flashes the stoplights to alert the drivers in following vehicles.

  2. FUNCTION OF COMPONENTS

    Component Function
    Skid Control ECU Monitors the driving conditions of the vehicle in accordance with the signals received from the sensors and through cooperative control with the power management control ECU and power steering ECU calculates the required amount of braking force, and controls the brake actuator.
    ABS Main Relay Controlled by the skid control ECU. In addition to supplying power to each solenoid, it supplies power to the skid control ECU.
    ABS Motor Relay (ECB* MTR1 Relay and ECB* MTR2 Relay)

    • These are two types of pump motor relays with different pump actuation speeds.

    • If one relay fails, the other relay operates to actuate the pump.
    Stop Light Control Relay

    • Illuminates the stop lights when hill-start assist control is operating.

    • Blinks the stop lights while emergency stop light control is operating.*1
    Speed Sensor Detect the wheel speed of each of the four wheels.
    Yaw Rate and Acceleration Sensor

    • Detects the vehicles yaw rate.

    • Detects the vehicles longitudinal and lateral acceleration and deceleration.
    Steering Angle Sensor Detects the steering direction and angle of the steering wheel.
    Brake Pedal Stroke Sensor Directly detects the extent of the brake pedal stroke operated by the driver.
    Stop Light Switch Detects brake pedal operation.
    VSC OFF Switch Enables the driver to select normal mode, TRC off mode, or VSC off mode.
    Parking Brake Switch Detects parking brake operation.
    Hazard Warning Switch*1 Transmits a hazard warning light on/off request to the main body ECU.
    Brake Control Power Supply

    • An auxiliary power supply to provide stable electrical power to the brake system.

    • When the voltage of the auxiliary battery is low, the power source backup unit supplements the supply of power to the brake system by providing the electric charge that is stored in the unit.
    Skid Control Buzzer

    • The skid control buzzer emits a warning sound to inform the driver during VSC operation.

    • Emits a warning sound to inform the driver when hill-start assist control operation is started or finished.

    • Sounds continuously to inform the driver if there is a hydraulic pressure malfunction or power supply failure.

    • Sounds to inform the driver of a change in brake pedal feeling if the skid control ECU has not learned the conditions of the linear solenoid valves in the brake actuator.
    Power Management Control ECU

    • Actuates regenerative braking upon receiving a signal from the skid control ECU.

    • Sends the actual regenerative braking control value to the skid control ECU.

    • Controls the drive force based on an output control request signal received from the skid control ECU while the VSC function or TRC function is operating.
    Main Body ECU (Instrument Panel Junction Block)

    • Transmits the parking brake signal to the skid control ECU.

    • Detects the hazard warning switch on/off signal and outputs it to the skid control ECU via CAN communication.*1
    Master Cylinder

    • Generates hydraulic pressure in accordance with the amount of effort applied to the brake pedal by the driver.

    • When a malfunction occurs in the power supply portion of the brake actuator, the brake master cylinder supplies the fluid pressure (which is generated by brake pedal effort) directly to the wheel cylinders.
    Reservoir Tank Stores the brake fluid.
    Brake Fluid Level Warning Switch Detects a low brake fluid level.
    Brake Stroke Simulator Cylinder Provides a pedal stroke during braking in accordance with the drivers pedal effort.
    Stroke Simulator Cut Valve Allows the fluid pressure generated by the master cylinder to flow into the brake stroke simulator cylinder while the electronically controlled brake system operates.
    Brake Booster Pump Accumulator Stores the hydraulic pressure that was generated by the pump. The accumulator is filled with high pressure nitrogen gas.
    Pump and Pump Motor Draws up the brake fluid from the reservoir tank and provides high hydraulic pressure to the accumulator.
    Brake Actuator

    • Consists of two master cut solenoid valves, four pressure application solenoid valves, and four pressure reduction solenoid valves.

    • The master cylinder pressure sensors, the accumulator pressure sensor, the wheel cylinder pressure sensors and the relief valve are installed in the brake actuator.
    Relief Valve Returns the brake fluid to the reservoir tank to prevent excessive pressure if the pump operates continuously due to a malfunction of the accumulator pressure sensor.
    Master Cylinder Pressure Sensor The master cylinder pressure sensor converts the fluid pressure generated by the master cylinder into electrical signals and transmits them to the skid control ECU. Accordingly, the skid control ECU determines the braking force required by the driver.
    Wheel Cylinder Pressure Sensor These sensors detect the fluid pressure that acts on their respective wheel cylinders and transmits the pressure to the skid control ECU to provide feedback. Accordingly, the skid control ECU can monitor the fluid pressure of the wheel cylinders and control the pressure application solenoid valves and the pressure reduction solenoid valves, in order to achieve the optimal wheel cylinder pressures.
    Accumulator Pressure Sensor The accumulator pressure sensor constantly monitors the brake fluid pressure in the accumulator and transmits a signal to the skid control ECU. Accordingly, the skid control ECU controls the pump motor.

    Switching Solenoid Valve

    (Master Cut Solenoid Valve)

    • When the brake pedal is depressed, this valve cuts the hydraulic passage between the master cylinder and its wheel cylinder.

    • When the brake pedal is not depressed or a failure occurs in the hydraulic power source portion, the valves open to maintain the hydraulic passage to the front wheel cylinders and ensure braking.

    • When a failure occurs, a greater effort than normal is required to depress the brake pedal.

    Linear Solenoid Valve

    (Pressure Application Valve)

    		 These valves, which are controlled by the skid control ECU, regulate the fluid pressure from the accumulator in order to amplify the fluid pressure to the wheel cylinders.

    Linear Solenoid Valve

    (Pressure Reduction Valve)

    		 These valves, which are controlled by the skid control ECU, regulate the fluid pressure in order to reduce the fluid pressure to the wheel cylinders.
    Combination Meter ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS or BA.
    Brake Warning Light / Red (Malfunction)

    • Illuminates to alert the driver that the skid control ECU detects the malfunction in the apportioning of the brake.

    • Illuminates to inform the driver when the parking brake is ON or the brake fluid is low.
    Brake Warning Light / Yellow (Minor Malfunction) Illuminates to alert the driver that a minor malfunction which does not affect the braking force has occurred in the brake system.
    VSC OFF Indicator Light Illuminates to inform the driver when VSC off mode is selected.
    Slip Indicator Light

    • Blinks to inform the driver when the ABS, TRC, VSC, or hill-start assist control operates.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TRC or VSC systems.
    Multi-information Display Shows a warning message to alert the driver when the skid control ECU detects a malfunction in the brake control system.

    *: Electronically Controlled Brake System

    *1: w/ Emergency Brake Signal