 printable version
Anti-lock brakes (ABS)
Location of anti-lock brakes (ABS) on the car
1 - hydraulic control unit HCV;
2 - Control unit ABS;
3 - the main relay;
4 - motor relay;
5 - wheel speed sensor;
6 - wheel speed sensor; | 7 - a pressure regulator;
8 - the connector;
9 - connector of the engine;
10 - Connector block of hydraulic management HCV. |
The principle of the brake system 1 - Control unit ABS;
2 - speed sensor;
3 - an electric pump;
4 - a reserve tank of brake system;
5 - the master cylinder;
6 - the vacuum brake booster;
7 - the pressure accumulator; | 8 - the brake pedal;
9 - the primary piston;
10 - central valve;
11 - inlet valve;
12 - the wheel speed sensor;
13 - Caliper;
14 - exhaust valve. |
The hydraulic circuit brake system 1 - the vacuum brake booster;
2 - the master cylinder;
3 - the central valve;
4 - reserve tank;
5 - brake fluid level;
6 - the pressure accumulator; | 7 - pump;
8 - the engine;
9 - an inlet valve (NO);
10 - inlet valve (NO);
11 - exhaust valve (NC);
12 - exhaust valve (NC). |
Anti-lock braking system is designed to eliminate wheel lock under heavy braking.
The main function of ABS:
- Reducing the stopping distance by eliminating the wheels from locking under heavy braking;
- Improving the steering stability during braking.
Three-channel anti-lock braking system with four sensors working in such a way that each of the front wheels is controlled independently, and the rear wheels are controlled on the basis of selecting the lowest speed (control hydraulic pressure is produced on the side from which the sliding occurs first).
How ABS works
Braking is performed as in the conventional braking system as long as the ABS control unit detects that the wheel is locked.
In standard mode, the braking solenoid valves do not work, the inlet valve is normally open and the outlet - normally closed.
When ABS is a hydraulic device controlled by the control unit ABS, controls each valve in three stages, maintaining, increasing or decreasing the pressure.
ABS control unit via the wheel speed sensor detects the speed and deceleration of each wheel. In carrying out the braking of the wheel speed decreases, and calculates the difference between the wheel speed and vehicle speed. If the deceleration speed of some of the wheels exceed the expected value (point A), the ABS control unit finds that there was a lock on the wheel and opens the exhaust solenoid valve to reduce the pressure of the brake fluid. If the pressure lock at the respective wheels is exceeded (point B) and the wheel speed increased to point C, the ABS control unit again closes the exhaust valve to increase the brake fluid pressure.
How ABS works
In cars with ABS may experience the following symptoms, indicating, however, on the correct operation of ABS.
Symptom | Description | | The noise of the motor | In managing the ABS hydraulic unit can be heard. | | The noise of the suspension system | Since the ABS braking operation is carried out in three stages, from the suspension system can be affected by noise. | | Fluctuations of the brake pedal | When the ABS comes rippling (rebound) of the brake pedal. |
1. Standard deceleration (braking without ABS)
When you press the brake pedal pressure fluid, increased brake servo, closed center valve and the master cylinder pressure is generated in the hydraulic brake lines. At this point, inlet solenoid valve is open, the outlet valve is closed and the hydraulic pressure of the master cylinder is transmitted to the wheel cylinder. 2. Brakes with ABS
2.1 Maintaining the pressure
After the ABS control unit found that the wheels are locking due to excessive increased pressure, the ABS control unit closes the inlet valve to prevent any further increase in pressure. 2.2 Reduction of pressure
If the wheels still locked, the ABS control unit opens the exhaust valve to the brake fluid can flow into the pressure accumulator, whereby the pressure decreases. The pressure is reduced only in the brakes locked wheels. 2.3 Increasing Pressure
If the wheels that were blocked again began to rotate to the desired speed, the ABS control unit ceases to control the solenoid valve, change the default mode of inhibition.
|
