Antilock Brakes / Traction Control Systems: Description and Operation
ABS (W/ Traction Control)SYSTEM OUTLINE
The vehicle could be in an extreme over steering or under steering tendency due to unexpected accidents, road conditions, vehicle speed, or by other external factors. In such a case, this system automatically controls the engine output and the braking to each wheel, to decrease the extreme over steering and under steering.
- To decrease extreme over steering tendency
When the system determines that the over steering tendency is large, the system applies brakes to the outer wheels according to the degree of over steering, and creates a moment towards the outer side of the vehicle, to decrease the tendency of over steering. Also, when the brakes are applied, the vehicle speed decreases while the stability increases.
- To decrease extreme under steering tendency
When the system determines that the under steering tendency is large, the system applies brakes to the front or rear wheels according to the degree of under steering, to decrease the tendency of under steering.
- VSC OFF SW
The SW to send the VSC system into OFF mode. When the SW is pushed after starting the engine, the system will be in OFF mode, and the VSC off indicator light will turn on. When the SW is pushed again, the system will be in standby mode. When the engine is stopped and re - started, regardless of the VSC OFF SW, the system will be in standby mode.
Information to the driver
The VSC system informs the driver when the tyre grip is about to exceed its grip capacity, by blinking the slip indicator light and turning on the buzzer. Accordingly, the driver is informed to drive more gently.
ABS (W/O Traction Control)
SYSTEM OUTLINE
ABS is a brake system designed for the purpose to improve the operating ability securing the stability of the vehicle by preventing the locking-up of the vehicle controlling the wheel cylinder pressure of all the four wheels at the time of sudden braking.
1. INPUT SIGNALS
1. Speed sensor signal
The speed of the wheels is detected and input to TERMINALS FL+, FR+, RL+, and RR+ of the ABS actuator and ECU.
2. Stop light SW signal
A signal is input to TERMINAL STP of the ABS actuator and ECU when brake pedal is depressed.
2. SYSTEM OPERATION
When the wheels are to be locked-up, the solenoid inside the actuator will be controlled by the signal from the ABS actuator and ECU and the brake fluid in the wheel cylinder will flow through the reservoir and reduce the hydraulic pressure.
While the ABS is in operation, as the ABS actuator and ECU always outputs the operation signal to the pump inside the actuator, brake fluid stored inside the reservoir will be sucked up by the pump inside the actuator and returned to the master cylinder.
When the hydraulic pressure of the wheel cylinder is decompressed or increased until the necessary hydraulic pressure, the solenoid inside the actuator is controlled by the control signal from the ABS actuator and ECU and as a result, hydraulic pressure of the wheel cylinder will be closed at both routes of the master cylinder and reservoir sides and the hydraulic pressure of the wheel cylinder will become to be in the holding condition.
If the increase of hydraulic pressure volume of the wheel cylinder becomes necessary, with the control signal from the ABS actuator and ECU, the solenoid inside the actuator will be controlled and become the same condition as usual and the brake fluid of the master cylinder will be sent to the wheel cylinder and will increase the hydraulic pressure of the wheel cylinder. At this time, in the case that the brake fluid stays left in the reservoir, it will be suctioned up by the pump inside the actuator and will be sent to the wheel cylinder.
Also, increasing speed of the hydraulic pressure is controlled by outputting the increasing and the said holding one after another.