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 assembly 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 and VSC) and steering assist control to enhance active safety when accelerating, turning and stopping.

    4. Steering Cooperative Control


      1. Performs cooperative control with the power steering ECU assembly 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 vehicle's 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 restrain sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid while cornering.

    10. Brake Hold System


      1. The brake hold operation occurs when the brake pedal is depressed and the vehicle is fully stopped. Under brake hold, the wheel cylinder oil pressure of the 4 wheels is maintained, and the vehicle's fully stopped condition is sustained. When the acceleration pedal is depressed, the wheel cylinder oil pressure is automatically released. Also, depending on the vehicle conditions, the electric parking brake operates.

  2. FUNCTION OF COMPONENTS

    Component Function
    Skid control ECU assembly 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 assembly, calculates the required amount of braking force, and controls the brake actuator assembly.
    ABS main relay Controlled by the skid control ECU assembly. In addition to supplying power to each solenoid, it supplies power to the skid control ECU assembly.
    ABS motor relay (ABS MOTOR NO. 1 relay and ABS MOTOR NO. 2 relay)

    • These are 2 types of pump motor relays with different pump actuation speeds.

    • If one relay fails, the other relay operates to actuate the pump.
    No. 2 integration relay

    • Receives signals from the skid control ECU assembly and turns on the stop lights.*1

    • Illuminates or blinks the stop lights according to signals from the stop light switch assembly and skid control ECU assembly.*2
    Speed sensor Detect the wheel speed of each of the 4 wheels.
    Yaw rate sensor

    • Detects the vehicle's yaw rate.

    • Detects the vehicle's longitudinal and lateral acceleration and deceleration.
    Steering sensor Detects the direction and angle of the steering wheel.
    Brake pedal stroke sensor assembly Directly detects the extent of the brake pedal stroke operated by the driver.
    Stop light switch assembly Detects brake pedal operation.
    VSC OFF switch Enables the driver to select Normal mode, TRC OFF mode, or VSC OFF mode.
    Brake hold switch Permits the brake hold operation.

    Front door courtesy light switch assembly LH*3

    Front door courtesy light switch assembly RH*4

    		 Detects the state of the door and sends signals to the skid control ECU assembly. When the door is opened with the power switch off, the electronically controlled brake system activates.
    Brake control power supply assembly

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

    • When the voltage of the auxiliary battery is low, the brake control power supply assembly supplements the supply of power to the brake system by providing the electric charge that is stored in the unit.
    Skid control buzzer assembly

    • 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 assembly has not learned the conditions of the linear solenoid valves in the brake actuator assembly.
    Power management control ECU

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

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

    • Controls the drive force based on an output control request signal received from the skid control ECU assembly while the VSC function or TRC function is operating.
    Power steering ECU assembly Performs steering torque assist during steering cooperative control according to signals from the skid control ECU assembly.
    Parking brake ECU assembly Drives the parking brake actuator according to signals from the skid control ECU assembly.
    Brake master cylinder sub-assembly

    • 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 assembly, the brake master cylinder supplies the fluid pressure (which is generated by brake pedal effort) directly to the wheel cylinders.
    Brake master cylinder reservoir assembly Brake fluid level warning switch Detects a low brake fluid level.
    Brake stroke simulator cylinder assembly Provides a pedal stroke during braking in accordance with the driver's pedal effort.
    Brake actuator assembly

    • Consists of 2 master cut solenoid valves, 4 pressure application solenoid valves, and 4 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 assembly.
    Brake actuator assembly 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.
    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 assembly. Accordingly, the skid control ECU assembly 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 assembly to provide feedback. Accordingly, the skid control ECU assembly 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 assembly. Accordingly, the skid control ECU assembly 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 assembly, 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 assembly, regulate the fluid pressure in order to reduce the fluid pressure to the wheel cylinders.
    Combination meter assembly ABS warning light Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the ABS.
    Brake warning light / red (malfunction)

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

    • Illuminates to inform the driver when 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 or VSC operates.

    • Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the TRC or VSC systems.
    Multi-information display

    • Displays a warning message to alert the driver when TRC OFF mode is selected.

    • Displays a warning message to alert the driver when the skid control ECU assembly detects a malfunction in the brake control function.
    Master warning light Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the brake control system.
    Brake hold standby indicator light / green Comes on when the system is in the brake hold control permission state.
    Brake hold operated indicator light / amber

    • Comes on when the brake hold is operating.

    • Blinks when a malfunction has occurred during brake hold control selection.

    • *1: w/o Emergency Brake Signal

    • *2: w/ Emergency Brake Signal

    • *3: for LHD

    • *4: for RHD