The two-section brake valve (Fig. 1) is designed to control the actuators of the vehicle’s service brake system, as well as to control the trailer brake actuator valve
The brake valve consists of an upper and lower body.
A crane linkage is attached to the upper body. The body of the lever is protected from dirt and moisture by a cover.
The upper cylinder controls the brakes of the trailer (semi-trailer), the lower cylinder controls the brakes of the tractor.
In fig. 2 - 4 shows in detail the device - the covers of the upper and lower cylinders of the brake valve.
The valve is removed from the car and partially or completely disassembled to eliminate air leakage through the outlet due to leaks in valves 15 or cuffs 13 and 19 (see Fig. 1).
The place of air leakage must be determined before removing the valve from the car according to the following signs:
leakage stopped after turning the parking brake lever 4 - valve 15 of the upper cylinder is leaky;
The leak did not stop after turning the parking brake lever - the cuff 13 of the piston of the upper cylinder is leaky;
The leak did not stop after pressing the brake pedal - valve 15 or cuff 19 of the piston of the lower cylinder are leaky.
Scheme for checking the tightness of cuffs with pistons is shown in fig. 5.
The brake valve is mounted on a special bracket under the cab and secured with three bolts on the inside of the left side member of the frame.
When removing the brake valve, unpin the pins of the rods, disconnect the ends of the drive rods from levers 2 and 4 (see Fig. 1) of the brake valve.
Unscrew the union nuts and disconnect the lines from the brake valve.
Unscrew the nuts of the crane mounting bolts, remove the washers, the brake valve and its bracket from the bolts.
Crane repair
Replace damaged parts during repair with new ones, factory-made.
When assembling the brake valve after repair, tighten the rod nut 1 so that the free play of the end of the lever 2 is 0.2-4.0 mm, and the working one is 19-21 mm, the free play of the lever is 4 - 8 - 12 mm, and the full — 44—47 mm.
After assembly, check the brake valve and, if necessary, adjust it on a special stand at a constant air pressure of 6.00-6.50 kgf / cm2.
When the levers 2 and 4 are in the free position, the air pressure in the trailer brake pneumatic line should be 4.8-5.3 kgf/cm2, and there should be no air pressure in the car brake pneumatic line.
Adjust by turning nut 3, having previously unscrewed locking bolt 6. If the air pressure in the brake line is less than 4.8—5.3 kgf/m2, nut 3 must be rotated clockwise.
When lever 2 is fully retracted, the air pressure in the trailer pneumatic line must be absent, in the vehicle brake pneumatic line it must be equal to the air pressure in the air tank.
Adjustment should be made with the rod nut 1 within the working stroke of the end of the lever 19-21 mm.
It is necessary to check the adjustments at three fixed positions of the regime ring 22, which must be turned with a key without jamming.
When lever 4 is fully retracted, there should be no air pressure in the car brake pneumatic line, and in the trailer brake pneumatic line it should decrease from 4.8–5.3 kgf/cm2 to 0.
When the lever is returned to its original position, the air pressure in the pneumatic line of the trailer should increase to 4.8-5.3 kgf/cm2.
In the case when the air pressure in the pneumatic line of the trailer brakes has not decreased to 0, then it is necessary to adjust the valve by rotating the guide washer 3 (see Fig. 3) relative to the nut 1, reducing the dimension a, equal to 97.5 mm.
After adjusting the position of the washer relative to nut 1 and pipe 4, fix it with locking ring 2 by drilling a new hole in the nut and pipe.
Install the checked and adjusted brake valve on the car, connect the ends of the rods and pipelines.
Check and, if necessary, adjust the brake valve drive.
The maximum air pressure in the pneumatic system after the brake valve (upper scale of the manometer) is regulated by bolt 12 (Fig. 6), which limits the stroke of the brake pedal and should be within 4.0–4.5 kgf/cm2
After adjusting, lock the bolt by tightening locknut 11.
Regulate the free travel of the brake pedal by changing the length of the rod 16.
It should be within 15-30 mm.
The start of the stroke is determined by a significant increase in pedal effort.
In When connecting the lever to the rod, there should be a gap between the pin and the bracket of 2 mm, no more. Adjust by changing the length of the rod.
Brake valve drive (see Fig. 6) is structurally made together with the clutch control drive and consists of a suspension pedal 5, levers 22 and 24, rods 8 and 16.
Removal and disassembly of the clutch and brake valve control actuator
Disconnect and remove springs 1 and 13.
Unpin the pins and remove the rods 8, 9, 16 and 17. Unscrew the bolts 7, 19 and remove the brackets 10, 21 as an assembly.
When disassembling bracket 10, unpin the ends of shaft 32 and remove washers 28 and 34.
Remove pinch bolt 31 of lever 26.
Remove clutch pedal 2 and brake pedal 5, clutch pedal key 33.
Move lever 26 towards the clutch pedal and remove key 30. Remove shaft 32 from the bracket, remove levers 24 and 26.
When disassembling the bracket 21, unscrew the coupling bolts 18, remove the levers 20 and 23, the keys, the shaft and the lever 22. If necessary, press the bushings out of the levers and brackets.
Data for monitoring the technical condition of brake and clutch drive parts are given in the table.
|
Detail |
Size, mm |
|
|---|---|---|
|
Denomination |
tolerance |
|
|
Clutch pedal shaft Outer diameter |
20-0.020 |
19.50 |
|
Clutch pedal shaft bushing Inner diameter |
20+0.150 |
20.50 |
|
Brake pedal bushing Inner diameter |
32+0.150 |
32.50 |
|
Brake pedal shaft Outer diameter |
32-0.100 |
31.50 |
|
Clutch release shaft Outer diameter |
20-0.020 |
19.50 |
|
Brake valve control lever assembly Shaft sleeve hole diameter |
20+0.150 |
20.50 |
Assemble the brake and clutch control drive in the reverse order of disassembly.
When assembling, bushings and shafts must be lubricated with graphite grease.
Connect the brake pedal shaft and lever 24 according to the marks made on the ends of the splined part of these parts.
We also look at the article "Two-section brake valve"
Determining the brake pedal freeplay
Measure the brake pedal free play (fig. 7). If it is more or less than 15 - 25 mm, adjust it by changing the length of the rod 2.
When measuring the free play, the drive lever must be pressed against the stop of the top cover of the brake valve. The beginning of the working stroke is determined by a significant increase in effort.