22:20. Anti-blocking system (ABS)
Prevention
Models without control system of the speed of the movement of the car
The anti-blocking system is installed by the producer on the majority of cars, and it is possible to install on the remained cars as the additional equipment. The system consists of the hydraulic device with three hydraulic electromagnetic valves on one on each forward brake and one valve on back brakes, the pump with the electric drive, three sensors of a wheel and the electronic control device (ECU). The anti-blocking system prevents blocking of wheels at sharp braking. Thanks to it the car at full braking remains operated. On the basis of signals from wheel sensors the ECU block can determine car speed. Due to comparison of speed of separately taken wheel with the average speed of the car the control unit defines a condition of blocking of a wheel. When the wheel approaches blocking, pressure of brake fluid is too high therefore pressure in a support decreases on a signal to the control unit due to turning on of the corresponding electromagnetic valve which isolates a support of the corresponding brake from the main brake cylinder.
If the speed of rotation of a wheel continues to decrease, on a signal of the ECU block the returnable pump turns on and pumps out liquid from the corresponding support in the main brake cylinder. After the wheel begins to rotate with a normal speed, the pump is switched off and the electromagnetic valve therefore brake fluid moves to a support in the normal mode opens and braking of a wheel is made. Work of anti-blocking system at sharp braking repeats on each wheel until the effort is made for a pedal or the car does not stop. The cycle of work of anti-blocking system is repeated to 10 times a second. During the work of anti-blocking system the pulsation on a brake pedal is felt.
At any malfunction in anti-blocks to rovochny system there is its shutdown. In this case the control lamp of ABS on the dashboard lights up and the brake system works in the usual mode. Elimination of malfunctions of anti-blocking system needs to be made at service station.
Models with a control system of the speed of the movement of the car (ASR)
On models with a control system of the speed of the movement of the car the hydraulic system consists of four electromagnetic valves, the returnable pump with the electric drive, the valve which switches the hydraulic device from anti-blocking system to performance of functions of a control system of the speed of the movement of the car and the pressurizing valve of a control system of the speed of the movement. On the car are installed two electronic control devices (ECU), one of which operates the hydraulic block, and the second – executive mechanisms of provision of a butterfly valve. Additional pump and the accumulator of pressure are also installed. To create and support pressure in system, necessary for performance of functions of braking during the work of a control system of the speed of the movement of the car.
The control system of the speed of the movement of the car excludes loss of coupling of wheels with a paving. The system corrects the speed of rotation of back wheels due to braking of a wheel or closing of a butterfly valve depending on the speed of the movement of the car. In certain cases both braking of a wheel, and closing of a butterfly valve can be made.
Braking of a wheel is carried out as follows. At loss of coupling of a wheel with a paving the wheel begins to rotate with the increased speed, and the hydraulic device from the accumulator of pressure gives under pressure brake fluid to a support of the corresponding wheel and slows down a wheel. After return of a wheel to the normal speed of rotation the hydraulic device returns liquid in pressure accumulator.
Management of a butterfly valve happens as follows. After loss of coupling of a wheel with a paving the second electronic control device puts the executive mechanism of a butterfly valve which, closing a butterfly valve, reduces engine turns in action. As soon as the wheel begins to rotate with a normal speed, the executive mechanism of a butterfly valve returns it in a starting position.
At detection of malfunctions in a control system of the speed of the movement of the car it is necessary to address on service station.