8.3. Pressure regulator drive: A, B, C – holes; 1 – pressure regulator; 2, 16 – pressure regulator mounting bolts; 3 – pressure regulator drive lever bracket; 4 – pin; 5 – pressure regulator drive lever; 6 – axis of the pressure regulator drive lever; 7 – lever spring; 8 – body bracket; 9 – pressure regulator mounting bracket; 10 – elastic lever of pressure regulator drive; 11 – earring; 12 – earring bracket; 13 – washer; 14 – retaining ring; 15 – bracket pin
The pressure regulator 1 (Fig. 8.3) is attached to the bracket 9 by two bolts 2 and 16. The fork-shaped bracket 3 of the lever 5 of the pressure regulator drive is simultaneously attached by the front bolt 2. The two-arm lever 5 is pivotally secured to the finger of this bracket by means of a pin 4. Its upper arm is connected to the elastic lever 10, the other end of which is pivotally connected to the bracket of the rear suspension lever via an earring 11. The bracket 3 together with the lever 5 can be moved relative to the pressure regulator due to the oval holes for the fastening bolt. By means of this, the force with which the lever 5 acts on the piston of the regulator is adjusted (see Fig. "Adjusting the pressure regulator drive").
8.4. Pressure regulator: A, D – chambers connected to the master cylinder; B, C – chambers connected to the wheel cylinders of the rear brakes; E – control hole; K, M, H – gaps; 1 – pressure regulator body; 2 – piston; 3 – protective cap; 4, 8 – retaining rings; 5 – piston bushing; 6 – piston spring; 7 – body bushing; 9, 22 – support washers; 10 – pusher sealing rings; 11 – support plate; 12 – pusher bushing spring; 13 – valve seat sealing ring; 14 – valve seat; 15 – sealing gasket; 16 – cork; 17 – valve spring; 18 – valve; 19 – pusher bushing; 20 – pusher; 21 – piston head seal; 23 – piston rod seal; 24 – plug
The regulator has four chambers: A and D (Fig. 8.4) are connected to the master cylinder, B to the right, and C to the left working cylinder of the rear brakes.
In the initial position of the brake pedal, piston 2 is pressed by lever 5 (see fig. 8.3) through the leaf spring 7 to the pusher 20 (see fig. 8.4), which is pressed by this force against the seat 14 of the valve 18. The latter is pressed away from the seat, a gap H and a gap K are formed between the piston head and the seal 21. Through these gaps, chambers A and D communicate with chambers B and C.
When the brake pedal is pressed, the fluid enters the wheel cylinders of the brake mechanisms through the gaps K and H and the chambers B and C. As the fluid pressure increases, the force on the piston increases, tending to push it out of the housing. If the force from the fluid pressure exceeds the force from the elastic lever, the piston begins to move out of the housing, and after it, the pusher 20 moves under the action of springs 12 and 17 together with the bushing 19 and rings 10. The gap M increases, and the gaps H and K decrease. When the gap H is completely selected and the valve 18 isolates the chamber D from the chamber C, the pusher 20 together with the parts located on it will stop moving after the piston. Now the pressure in chamber C will change depending on the pressure in chamber B. With a further increase in the force on the brake pedal, the pressure in chambers D, B and A increases, piston 2 continues to move out of the housing, and bushing 19 together with sealing rings 10 and plate 11 under the increasing pressure in chamber B moves towards plug 16. The gap M begins to decrease. Due to the decrease in the volume of chamber C, the pressure in it, and therefore in the brake drive, increases and will be practically equal to the pressure in chamber B. When the gap K becomes equal to zero, the pressure in chamber B, and therefore in chamber C, will increase to a lesser extent than the pressure in chamber A, due to throttling of the fluid between the piston head and seal 21. The relationship between the pressure in chambers B and A is determined by the ratio of the difference in the areas of the piston head and rod to the area of the head. As the vehicle load increases, elastic lever 10 (see fig. 8.3) is loaded more and the force from lever 5 on the piston increases, i.e. the moment of contact between the piston head and seal 21 (see fig. 8.4) is achieved with higher pressure in the master brake cylinder. Thus, the efficiency of the rear brakes increases with increasing load.
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In case of failure of the right front-left rear brake circuit, sealing rings 10, bushing 19 under the pressure of the fluid in chamber B will shift towards plug 16 until plate 11 stops against seat 14. The pressure in the rear brake will be regulated by the part of the regulator, which includes piston 2 with seal 21 and bushing 7. The operation of this part of the regulator in case of failure of the said circuit is similar to the operation with a serviceable system. The nature of the pressure change at the regulator outlet is the same as with a serviceable system. In case of failure of the left front-right rear brake circuit, pusher 20 with bushing 19, sealing rings 10 shifts towards the piston under the pressure of the brake fluid, pushing it out of the housing. The gap M increases, and the gap H decreases. When valve 18 touches seat 14, the pressure increase in chamber C stops, i.e. the regulator in this case operates as a pressure limiter. However, the pressure achieved is sufficient for reliable operation of the rear brake.
In the housing 1 there is a hole E, closed by a plug 24. The leakage of liquid from under the plug when it is squeezed out indicates a leak in the rings 10.