Power steering pump 1 with reservoir is mounted on the engine and is driven through a pulley by a V-belt from a pulley located at the front end of the crankshaft

The pulley 1 of the pump is fixed on the shaft 6 with an expanding conical sleeve 30, a key and a nut.

The pump is a vane type, double-acting, i.e. for one revolution of the pump shaft, two complete suction cycles and two discharge cycles are performed.

The rotor 9 of the pump has grooves in which the blades 14 move.

The rotor is splined on pump shaft 6; landing of the rotor on the splines is free.

ZIL-131 power steering pump

The position of the stator 8 relative to the pump housing 3 must be such that the direction of the arrow on the stator coincides with the direction of rotation of the pump shaft.

The pump blades must move in the grooves of the rotor without jamming.

When the pump shaft rotates, the vanes are pressed against the curved surface of the stator under the action of centrifugal force and oil pressure.

In the suction cavities, oil enters the space between the blades, and then, when the rotor rotates, it is displaced into the discharge cavity.

The end surfaces of the body and the distribution disc are carefully ground.

The presence of nicks, burrs, etc. on them, as well as on the rotor, stator and blades, is unacceptable.

A tank 19 for oil is installed on the pump, closed with a lid 23, which is tightened with a wing nut 25.

Under the wing nut there is a washer 24 and a rubber ring 26, which, together with the rubber gasket 20, seal the inner cavity of the tank.

A breather 22 is screwed into the lid of the tank to limit the pressure inside the tank.

All the oil returning from the hydraulic booster to the pump passes through the strainer 2 located inside the tank.

A bypass valve 12 is provided in case of clogging of the filter.

In addition, a filler strainer 21 is installed in the tank.

The pump has two valves located in the cover 11 of the pump.

Safety valve 17, placed inside the bypass valve 12, limits the oil pressure in the system, opening at a pressure of 65-70 kg/cm2.

The bypass valve limits the amount of oil supplied by the pump to the hydraulic booster when the engine speed increases.

The bypass valve works as follows.

The valve seat is connected on one side to the pump discharge cavity, and on the other hand to the hydraulic booster system discharge line, which, in turn, is connected to the pump discharge cavity by a calibrated hole.

With an increase in the oil supply to the hydraulic booster system (as a result of an increase in the number of revolutions of the engine crankshaft), the pressure difference in the pump discharge cavity and the system discharge line increases due to the resistance of the hole K and, therefore, the pressure difference increases at the ends of the bypass valve.

At a certain pressure difference, the force tending to move the valve to the right increases so much that the spring is compressed and the valve, moving, communicates the discharge cavity with the reservoir.

Thus, a further increase in the oil supply to the system almost stops.

To prevent noise and increased wear of the pump at a high number of revolutions of the engine crankshaft, the oil that is bypassed by valve 13 is forcibly directed back into the cavity of the pump housing and into the suction channels.

For this purpose, the collector 18 serves, in which the internal channel communicating with the cavity of the bypass valve has a small cross section.

This leads to a sharp increase in the flow rate of the bypassed oil into the suction cavity of the housing and creates some increase in suction pressure.

The radiator is designed to cool the oil in the power steering system.

ZIL-131 steering

Tubular radiator 14 (see Fig. 2) is installed above the oil cooler of the engine lubrication system.

Oil from the steering gear to the radiator and from the radiator to the pump is supplied by rubber hoses fastened with clamps.