Hydraulic power steering


Forward-Motion hydraulic power steering


The hydraulic power steering is intended for controlling the turning of the steerable wheels and reducing the force to be applied to the steering wheel for turning the tractor. The hydraulic power steering consists of a metering pump (1), two differential hydraulic cylinders (3) executing the turn, feeding pump (2) driven from the engine and hydraulic fittings.

The hydraulic power steering oil tank is the right-hand section of the oil tank (4) with the 25-micron filter of the working fluid.



1 – metering pump; 2 – feeding pump; 3 – hydraulic cylinders; 4 – oil tank.



Construction and Operation of the hydraulic power steering



The direct-acting metering pump (1) is installed on the bracket of the steering column; the turn hydraulic cylinder (3) – on the brackets attached to the front axle and the feed pump (2) – on the engine. The metering pump is connected to the chambers of the hydraulic cylinder of turning, feed pump and oil tank via pipe-lines.

When in a straight-ahead motion, the cylinder chambers are closed by the metering pump spool belts, and the oil fed from the feed pump and brought to the metering pump returns to the oil tank. When the steering wheel is turned, the metering spool-valve is displaced providing in such a way for oil supply to the chambers of the hydraulic cylinder of turning in the amount proportional to the angle of turn of the steering wheel.

Recommendations for Operation of the hydraulic power steering


When assembling the hydraulic power steering:
Install properly the oil pipelines and hoses in accordance with the hydraulic diagram;
Protect the connecting holes of the metering pumps, hydraulic cylinders, poi pipelines and high-pressure hoses against penetration of dirt;
Prior to starting the engine, check the tightening of all the connections of the hydraulic power steering hydraulic system;
When tightening the fasteners, apply the required torque;
Fill the oil tank to the upper limit as seen on the level indicator;Bleed air from the hydraulic system. 

To do this, proceed as follows:
Start the engine. Turn the steering wheel in both directions 3-4 times at the idling rotational speed of the engine without reaching the extreme positions of turning of the steerable wheels. Add oil to the tank to the required level.
Turn the wheels from one stop to an-other 2-3 times. Hold the steering wheel at the extreme positions for 4...5 seconds.
If necessary, eliminate the oil leaks and add oil to the top level of the tank.
Drive the figure of eight to check the operation of the steering control.

Metering Pump


The metering pump consists of assembly I, distributor II, non-return valve (9), two anti-hammer valves (7), relief valve (6) and two anti-vacuum valves (8).



1 – stator; 2 – rotor; 3 – spool valve; 4 – power shaft; 5 – sleeve; 6 – relief valve; 7 – anti-hammer valves; 8 – anti-vacuum valves; 9 – non-return valve; 10 – body. I – pumping assembly; II – distributor

The Gerotor pumping assembly I consists of the stator (1) fixed on the body and rotating rotor (2) connected to the spool valve (3) by the power shaft (4). The distributor II consists of the body (10), sleeve (5) and spool valve (3) splined onto the tail-end of the power shaft of the steering column:
The relief valve (6) limits the maximum pressure in the pressure mainline to within 17.5...18.0 MPa (175...180 kgf/cm2) in the hydraulic power steering system with the double-rod hydraulic cylinder or to within 14.0...14.5 MPa (140...145 kgf/cm2) in the hydraulic power steering system with two hydraulic cylinders of steering control.

The anti-hammer valves (7) limit pressure in the cylinder mainlines at impact loads. The pressure setting of the anti-hammer valves is within 22.5...24.5 MPa (225...245 kgf/cm2).
The anti-vacuum valves (8) make it possible to ensure the required supply of the working fluid into the hydraulic cylinder in the emergency mode and in case of operation of the anti-hammer valves.