The parking brake control valve is used to control the spring-loaded energy accumulators of the parking and spare brakes (Fig. 1, a - c)

Parking brake control valve

The manual brake valve is used to control the spring-loaded energy accumulators of the parking and emergency brake systems

According to the principle of operation, a reverse-acting brake valve - controls pneumatic elements that operate when compressed air is released

In the initial position (without braking, figure b), the guide cap 8 and the stem 9, under the action of their springs, occupy the lowest positions, and the exhaust valve 10, cut off from the piston seat 11 by the edge of the stem 9, separates output I from the atmospheric output II and communicates output I with output III.

Compressed air through the hole in the piston 11 enters cavity A and through the inlet window of the valve seat, made at the bottom of the piston 11, into cavity B, from where it passes through a vertical channel to port III and then to an accelerator valve that supplies compressed air to spring energy storage cylinders.

Springs of energy accumulators are compressed under the action of compressed air.

To activate the spare brake system, turn the crank handle. In this case (figure (c)) together with the cover 7, the guide cap 8 is rotated.

Sliding along the helical surfaces of the curly protrusions of the ring 5, the cap 8 rises and drags the stem 9 along with it.

The lower edge of the stem 9 breaks away from the valve 10 and the latter, under the action of the spring 1, sits in the piston seat 11, separating the output I from the output III and communicating the atmospheric output II with the output III.

The flow of compressed air from port I to port III stops, and the compressed air from the control line of the relay valve through port III, valve opening 10 and port II goes into the atmosphere until the pressure in cavity A under piston 11 overcomes the total the force of the balancing spring 3 and the pressure on the piston in cavity B.

If the forces are equal, the piston 11, together with the valve 10, rises until the valve fits on the edge of the rod 9. The air is released from the accelerator pump control line through port III, i.e., a follow-up action is carried out.

When compressed air is released from the control line of the accelerating valve, the latter disconnects the cavity of the cylinders of the spring energy accumulators from the supply line and connects them to the atmospheric outlet of the accelerating valve.

Compressed air from the cylinders is released into the atmosphere, and spring-loaded energy accumulators brake the wheels of the car's rear bogie.

The characteristics of the springs of the energy accumulators are selected in such a way that they provide a direct dependence of the pressure, and, consequently, the braking forces on the wheels, on the angle of rotation of the handle.

The crane stopper has an automatic return of the handle to its original position when it is released

To activate the parking brake system, it is necessary to turn the crane handle back until it stops, where it is fixed with a locking latch.

At the same time, the air from outlet III completely escapes into the atmospheric outlet II, since the piston 11 rests against the spring limiter 4 and the valve 10 does not reach the lower edge of the stem 9. To release the parking brake system, turn the valve handle forward until it stops.

In this case, compressed air will flow from the air cylinder to the spring-loaded cylinders. Under the action of compressed air, the springs are compressed and the brake mechanisms are released

Scheme of operation of the Kamaz parking crane

Replacing the parking brake control valve

We replace the valve in case of the following malfunctions:

  • - piston and valve hanging;
  • - damage to sealing rings;
  • - mechanical damage to the body, handle, mechanism of its fixation, impairing the normal operation of the crane

Tools will be required: a screwdriver, wrenches for 10, 12, 14, 17

Crane removal

We prepare the car and release air from the receivers 19 of the parking brake circuit

We unscrew the union nuts of the pipelines suitable for the tap, and disconnect the pipelines from the tap fittings

We unscrew the nuts of the screws securing the crane to the bracket and remove the crane

Crane installation

We install the crane on the bracket and fix it

We connect pipelines to the fittings of the crane and tighten the union nuts of the pipelines

We start the engine, create pressure in the pneumatic drive of the brake systems and check the operation of the crane on the spot and in motion

Repair of the parking brake control valve

To complete the task, you will need tools: a vice with soft jaws, a screwdriver, special pliers I801.23.000-01, a set of probes, pliers, a hammer

Crane disassembly

Install the brake valve in a vise with the cap up

 Ремонт крана управления стояночной тормозной системой

We unscrew the screws 3 with washers 4, 5, 6 fastening the cover 7 of the tap to the body 28

Remove the cover assembly with handle 1 and spring 2 from the housing

We unscrew the handle 1 from the cover 7

Remove pin 9 from stem 18, remove washer 10, cap 11

We take out from the body 28 the thrust ring 12, the guide 13, the ring 14, the spring 15, the rod 18, the washer 17, the ring 16, the plate 19, the spring 20, the piston 21 as an assembly

We remove the thrust ring 26 from the piston 21, take out the valve ring 22, body 23, support washer 24, spring 25

We remove the body 28 of the crane assembly with washers 29 and ring 27 from the vise

We wash the parts of the brake valve in diesel fuel and blow it with compressed air

Crane assembly

We install in the piston 21 the valve ring 22, the valve body 23, the support washer 24, the spring 25, the thrust ring 26

Note: Before installation, the working surface of the valve body is coated with Ciatim-221 grease.

We install the body 28 assembled with washers 29 and ring 27 in a vice

We install in the valve body the piston 21 assembly, the rod 18, the spring 20, the plate 19, the washer 17, the ring 16, the spring 15, the guide 13 with the ring 14 and the thrust ring 12

Note: before installation, the working surface of the piston and rod is coated with Ciatim-221 grease

We install the guide cap 11 and the washer 10 into the valve body

We install pin 9 in the stem

We screw the handle 1 into the cover 7 of the crane

We install cover 7 assembled with a handle and spring 2 on the body 28 of the crane

We screw the screws 3 fastening the cover with washers into the valve body

Remove the brake valve from the vise

We adjust the gap between the faucet cover and the washer in the following order:

 Регулировка зазоров крана управления

After installing spring 1 and plate 6, we compress the spring to a size a = 13.7 -0.1 mm from the upper end of body 2 to the upper end of plate 6, while the spring force should be equal to 127.5-152.0 N (13, 0-15.5 kgf).

If this force is less than 127.5 N (13.0 kgf), then, by replacing position 5 of the washer (item 100-3537095 or 1003537097), bring the spring force to the required value.

Installing one washer (item 100-3537095) increases the spring force by 41.7 N (4.25 kgf) and provides a pressure drop of 34.3 kPa (0.35 kgf / cm 2), and installing one washer det. 100-353797 increases the spring force by 25.0 N (2.55 kgf) and provides a pressure drop of 20.6 kPa (0.21 kgf / cm 2).

We measure the gap b between cover 3 and washer 4, which should not exceed 0.15 mm.

If this gap is larger, combine washers (part no. 100-3537092) 0.15 mm thick, (part no. 100-3537093) 0.2 mm thick and (part no. 100-3537094) 0.3 mm thick, combine and place on the washer 4 between the cover 3 and the body 2 so that the gap remains no more than the specified value.

Coat the washers with a thin layer of Ciatim-221 lubricant. Washer 4 (det. 100-3537091) with a thickness of 0.5 mm remains constantly at the bottom.

We check whether the crane lever returns easily when it is turned 45 and 70º from position I

We test the brake valve for performance and tightness

Test order:

We connect the tap according to the diagram shown in the figure

 Схема подключения крана для испытания

We set the pressure on pressure gauges 4 and 2, equal to 736 kPa (7.5 kgf / cm 2). In this case, the air from the output "A" should not come out.

Crane handle 3 is slowly moved from position I to position III. When moving the handle, there should be no jamming, and it should be easily fixed in position III.

When turning the handle through an angle of up to 70º, it should automatically return to position I.

Slowly turn the handle from position I. When turning the handle by 8-10º, pressure gauge 2 should show a pressure drop of no more than 147 kPa (1.5 kgf / cm 2).

With a further turn of the handle, the pressure should gradually decrease to 0, and during the reverse movement, it should gradually increase from 0 to 539.4 kPa (5.5 kgf / cm 2).

The step change should not exceed 29.4 kPa (0.3 kgf / cm 2). The pressure drop on pressure gauge 2 to 0 should be achieved by turning the handle 60-70º.

If there is residual pressure, eliminate it by installing a washer (P/N 1003537095) over the spring as indicated in point 1 of transition 19.

Set the handle to position III. At the same time, the pressure on the pressure gauge 2 should be equal to 0, and air should not come out of the output “A”.

We return the handle to position I. The valve must be airtight in any position of the handle.