The tyre pressure regulation system consists of a pressure control valve, an inter-tank pressure reducing valve, a tyre valve block, a seal block for air supply in the axle stub housing, wheel valves and pipelines.
Air is supplied to the regulation system from air tanks 11.
The tyre pressure control valve is of the spool type and consists of a body 1, in which two seals 5 and a spool 9 are installed.
When the spool moves axially, its annular groove connects the valve cavity either to the atmosphere or to the delivery line.
The pressure control valve lever can be set to three positions:
- - left position – tyre inflation;
- - centre position – neutral;
- - right position – air release from tyres to atmosphere.
Air enters the tyre valve block from the pressure control valve.
The block has six valves with handwheels, corresponding to the number of tyres.
The purpose of each valve is shown in the figure.
When the valves are open and all vehicle tyres are interconnected, the pressure in them is the same.
In this case, inflation and deflation can be carried out simultaneously for all tyres.
The air pressure in the tyres is monitored using the pressure gauge included in the tyre pressure regulation system.
The air supply seal block is installed in the wheel stub axle and consists of four seals.
The two middle seals ensure the tightness of the connection between the channels of the fixed stub axle and the channels of the rotating axle shaft.
The two outer seals serve to retain grease on the working surfaces of the air supply seals.
The inter-tank pressure reducing valve is installed between the air tanks on the right-hand side member of the vehicle.
The reducing valve sets the pressure in the brake system required for safe vehicle movement.
When the air pressure in the first (front) tank exceeds 5 kg/cm², the valve 5 opens, and air flows through the elbow 8, channels 9 and fitting 10 into the second tank.
When the pressure in the brake system drops below 4.5 kg/cm², valve 5 closes, and the system supply is automatically cut off.
If the pressure in the first tank is 0.5 kg/cm² lower than in the second, the reducing valve allows the compressed air reserve from the second tank to be used for the brake system.
In this case, air from the second tank flows through the fitting 10, check valve 7 and elbow 8 to the first tank.
Use and maintenance of the tyre pressure regulation system
During driving, the valves of the tyre valve block and the wheel valves must be fully open, and during long-term parking – closed to prevent air leakage through pipeline imperfections.
The air pressure in the tyres is determined by the pressure gauge with the pressure control valve lever in the neutral position and the wheel valves and tyre valve block valves open.
If a pressure drop is observed, by closing all valves and opening them one by one, it is possible to determine which tyre is leaking air.
The pressure regulation system allows the vehicle to continue moving in the event of a tyre puncture, without resorting to immediate wheel replacement.
However, the compressor output must be sufficient to compensate for the leakage from the damaged inner tube and provide the necessary pressure in the brakes.
The tyre pressure and driving speed must be set according to the nature of the road surface (Table 1).
Table 1. Tyre pressure depending on the road surface
Over-wet meadow, marshy area:
- - permissible air pressure - 0.5-0.75 kg/cm²;
- - maximum vehicle speed - 10 km/h
Loose sand, wet ploughed land, snow virgin land:
- - permissible air pressure - 0.75-1.4 kg/cm²;
- - maximum vehicle speed - 20 km/h
Waterlogged dirt roads, loose soil, wet meadow:
- - permissible air pressure - 1.4-1.7 kg/cm²;
- - maximum vehicle speed - 20 km/h
All types of roads (only during inflation):
- - permissible air pressure - from 1.5 to 3.2 kg/cm²;
- - maximum vehicle speed - 30 km/h
If it is necessary to reduce the tyre pressure, set it according to the driving conditions.
Maintenance of the system consists of checking its tightness.
Detect places of major leakage by ear, places of minor leakage using soap emulsion.
Eliminate air leaks through connections by tightening or replacing the individual connection element.
If the pressure control valve, wheel valves and pipeline connections are found to be tight during inspection, then the leak is occurring through the air supply seals. If the leak is large, replace the seals.
The reliability of the air supply seal block depends, first of all, on the presence and condition of the grease on their friction surfaces.
When installing seals, lubricate these surfaces and pack grease into the cavities between the first and second, and between the third and fourth seals.
When installing the axle shaft, also carefully lubricate the surface of the working journal, ensuring that the grease does not get into the air supply hole.
Install the seals using a special mandrel (position a), which prevents them from being damaged during pressing.
Remove the seals using a special puller (positions b and c) supplied in the tool kit.
In the event of significant damage to the pressure regulation system, inflate the tyre using the hose supplied in the driver's tool kit, connecting it to the air extraction valve and alternately to the wheel valves.
