Elements of the braking system with ABS
1 – modulators; 2 – main brake cylinder; 3 – pressure regulator; 4 – brake pipes; 5 – toothed belts
ABS modulator
1 – pulley; 2 – shaft; 3 – flywheel; 4 – eccentric; 5 – pump plunger; 6 – Low speed stopper; 7 – friction clutch; 8 – ball stopper
ABS drive
1 – control module; 2 – pulley; 3 – toothed drive belt; 4 – drive pulley; 5 – drive shaft; 6 – toothed belt cover
Anti-lock braking system
1 – vacuum brake booster with master brake cylinder; 2 – return pipeline; 3 – regulator; 4 – brake pipes; 5 – outer belt cover; 6 – toothed belt; 7 – drive shaft pulley; 8 – regulator mount; 9 – electric belt tension drive; 10 – inner belt cover
The wheel speed control system includes two modulators that receive drive from the drive shafts via a toothed belt. In vehicles equipped with an anti-lock braking system, a brake regulator is installed that reacts to the vehicle load.
The anti-lock braking system works as follows. During sharp braking, if the deceleration of the front wheel exceeds a certain value, the tendency of the wheel to lock is transmitted via a toothed belt to a modulator connected to it. At this moment, a flywheel is activated in the modulator, controlling the brake system valves, which reduce or restore the pressure of the brake fluid in the wheel cylinder.
Over time, the flywheel speed drops and, since the shut-off valve simultaneously interrupts the pressure transfer from the master brake cylinder to the brake, the braking intensity decreases. As a result, the front wheel again increases its speed to the decreasing number of flywheel speeds. Then the pressure relief valve in the modulator closes, the pressure from the master brake cylinder is again transmitted unhindered to the wheel brake cylinder and the wheel is braked. The pressure increases until the regulation process is repeated or until it equalizes with the pressure in the master brake cylinder, as a result of which the shut-off valve opens and the braking system continues to operate normally.
Checking the belt tension
1 – lid; 2 – window for checking belt tension; 3 – sliding contact; 4 – switch
Timing belt deflection
The deflection of the toothed belt at the point indicated by the arrow, under normal tension, should be 5 mm.
During vehicle operation, it is necessary to periodically check the tension of the toothed belt, the deflection of which from pressing with a finger on the middle of the belt should be equal to 5 mm. The check is carried out through the window in the cover of the toothed belt of the ABS drive.
With the ignition on, turn on the switch and press the belt with the sliding contact. The control lamp lights up to indicate that the belt is not tensioned enough.
To prevent the rear wheels from locking, a pressure regulator is installed in the rear brake drive on cars with an anti-lock braking system, depending on the load on the rear axle of the car. As the load increases, it ensures the passage of fluid to the wheel cylinders of the rear brakes, which increases the pressure in their circuit and improves the efficiency of the rear brake mechanisms. As the load decreases, the regulator reduces the supply of fluid to the brake mechanisms until it is completely cut off, as a result of which the pressure in the rear brake drive decreases and the likelihood that the rear wheels will lock earlier than the front ones decreases. This prevents the rear wheels from slipping and the car from skidding.