Accelerator valve supplies compressed air to the energy accumulators and is designed to reduce the actuation time of the parking and reserve brakes by reducing the length of the compressed air inlet line to the spring energy accumulators and releasing it into the atmosphere

It consists of a control chamber 2, a piston 3, an exhaust valve 1 and an intake valve 4, and an intake valve spring 5. The III terminal is constantly supplied with compressed air from the receiver.

Outlet IV is connected to a hand brake valve, outlet I is connected to the cylinder cavities of spring energy accumulators, outlet II is connected to the atmosphere.

Relay valve

In the initial position, when the car is disengaged (Fig. b), piston 3 is in the lower position, under the action of compressed air, exhaust valve 1 is closed, inlet valve 4 is open, since the area of ​​the upper part of piston 3 is larger than the area of ​​the lower one, and the pressure in cavity A and chamber 2 is the same.

Output I is decoupled from the atmospheric output II, and the pistons of spring energy accumulators are under compressed air pressure and do not affect the rods of the brake chambers.

When braking (Fig. 1c), compressed air from chamber 2 is released into the atmosphere through the atmospheric outlet of the manual brake valve.

With the pressure drop in chamber 2, piston 3 moves upwards, inlet valve 4 closes under the action of spring 5, and outlet valve 1 opens.

Through the output I and the open exhaust valve 1, the cavities of the spring energy accumulators communicate with the atmospheric output II.

The pressure in the cavities of the cylinders of spring energy accumulators decreases, the springs are released, and the brake mechanisms are braked.

The release is carried out by supplying compressed air from the valve to the output IV and then to chamber 2.

Piston 3, moving down, first opens the exhaust valve 1, then the intake valve 4.

Compressed air comes from the receiver into the cavities of spring energy accumulators.

The pressure in the cavities of the cylinders of spring energy accumulators increases, the springs the tires are compressed, and the brake mechanisms are released.

Proportionality between the control pressure in the output IV and the pressure in the cavities of the spring energy accumulators (in the output I) is maintained by piston 3.

When a certain pressure is reached in the output I, the piston 3 moves up to the closed inlet valve 4, which moves under the action of the spring 5, and further pressure growth stops.

When the pressure in the port IV decreases, the piston 3 moves up under the action of a higher pressure in the port I and breaks away from the outlet valve 1.

Compressed air from the cavities of spring energy accumulators goes into the atmosphere through the open valve 1 and the atmospheric outlet II, the pressure in the cavity A decreases.

Relay valve replacement

The relay valve must be replaced if the following malfunctions occur:

  • - violation of the tightness of the valve. An external sign is air leakage through the terminals in the places where the cover is attached to the valve body;
  • - mechanical damage to the body, cover and pistons of the valve, disrupting its operation

You will need tools: wrenches 22x24, 17x19, 12x13, spanner wrench 13x17, vise

Remote valve removal

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

We unscrew the union nuts of the pipelines connected to the terminals of the relay valve 22 and the two-way valve 20

Unscrew the nuts securing the relay valve bracket to the frame. We disconnect the pipelines from the valve outlets and remove the valve 22 together with the valve 20 and the bracket

Disconnect the relay valve from the bracket by unscrewing the bracket nuts

Disconnect the valve 20 with the union from the valve 22

Relay valve installation

We install the bracket on the valve and fix it with nuts, we attach the two-line valve 20 together with the through fitting

We install the assembled valve with a bracket on the frame and fix it with nuts

We insert the pipelines into the valve outlets, tighten the union nuts of the pipelines and fixI eat the valve on the bracket to the frame

Tightening the union nuts of the pipelines on the valve outlets

We start the engine and create pressure in the pneumatic drive of the brake systems

Check the tightness of the pipelines and the relay valve. Air leakage is not allowed

Checking the operation of the accelerating valve during braking and releasing the car

Relay valve repair

We need tools: a vice with soft jaws, a socket wrench 13x17, special pliers I801.23.000-01, dishes for washing parts

Relay Valve Disassembly

Installing the valve in a vise

Relay valve repair

We unscrew the bolts 2 with washers 3 fastening the upper case 7 with the lower case 4

Remove the upper body from the vise

We remove from the lower housing 4 the thrust ring 14, the housing 9 with the inlet and outlet valves, the spring 11, the guide cap 12

Remove the lower case 4 from the vise

Remove piston 6 with o-rings 5 ​​from upper housing 7

Note: apply compressed air to the valve cover and remove the piston

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

Relay valve assembly

Installing the lower body 4 in the vise

We install the guide cap 12, the spring 11, the body 9, the ring 8, the cap 10, the valve 13, the thrust ring 14 into the body 4

Install in housing 7 complete with piston 6

We screw in the bolts 2 fastening the body 7 of the cover to the body 4 with spring washers 3

Remove the valve from the vise

We test the relay valve for performance and tightness

Test order:

- connect the device according to the diagram shown in the figure

Relay Valve Test Scheme

  • - open the valve 7. Using the fine control valve 2, set the pressure on the pressure gauge 3 to 736 kPa (7.5 kgf / cm 2).

There should be no air leakage from the outlet window 8 of the device 4 and through the included tap 7. Close tap 2 fine control

  • - open tap 1. There should be no air leakage from the outlet window 8 of the device 4 and through the included tap 7. Close tap 7
  • - quickly open and close tap 2 for fine control three times. At the same time, the pressure on pressure gauge 5 should change from 0 to 736 kPa (7.5 kgf/cm 2) and back
  • - slowly increase the pressure on the pressure gauge 3 with fine control valve 2. When pressure gauge 3 reaches 29.4-44.1 kPa (0.3-0.45 kgf/cm 2), pressure gauge 5 should start showing pressure
  • - increase the pressure on the pressure gauge 3 to 736 kPa (7.5 kgf / cm 2). At the same time, the pressure should increase synchronously on the pressure gauge 5. With pressure on pressure gauge 3 equal to 647-687 kPa (6.6-7.0 kgf/cm 2), pressure on pressure gauge 5 should become equal to 716.1 kPa (7.3 kgf/cm 2)
  • - with fine control valve 2, slowly reduce the pressure on pressure gauge 3 to 0, on pressure gauge 5, the pressure should simultaneously drop to 0

Stepping of pressure change during all tests should not exceed 19.6 kPa (0.2 kgf / cm 2)

When testing, there should be no air leakage from devices 4 at any pressure at port S.