The steering includes a steering gear 10 (Fig. 1) with a built-in distributor, a column 2, a steering wheel 1, a power cylinder 9, a pump 3, an oil tank 4, and hoses.
To diagnose the operation of the hydraulic steering system, remember the following:
- - when the spool passes through the neutral position (turning the steering wheel to the left - to the right of the middle position) and the temperature of the working fluid (50 ± 5) ° С, the pressure in the pressure line should not exceed 0.3 MPa (3 kgf / cm 2);
- - at a crankshaft speed of 1500 min1 and the extreme (left or right) position of the steered wheels, the maximum pressure in the pressure line should not exceed 11 MPa (110 kgf/cm2).
The axis of the outer surface of the liners 12 is shifted relative to the axis of the bore of the bearings 13 by the amount of eccentricity "h", which makes it possible to adjust the gearing by turning the liners 12.
The preload of bearings 1 is adjusted using shims 9.
The steering gear with built-in distributor and fluid pressure limiting valve is shown in fig. 2.
It is possible to install a steering mechanism on cars (Fig. 3).
Power steering distributor - spool type, built into the steering gear.
In body 6 (fig. 4) of the spool there are three annular bores C, E, D.
The middle annular bore E is connected to channel "B" for supplying the working fluid from the pump, and the extreme C and D are connected to channel A for draining fluid to the drain.
Plungers 25 are placed freely, with the possibility of axial movement, in three reactive chambers of the body b of the spool.
A spool 26 is installed in the central hole of the body, fixed by thrust bearings 4 and 11 on the sleeve 12, which is splined without lateral clearance with the screw 28 of the steering mechanism with the possibility of axial movement, and with a screw connection with the input shaft 18.
The spline connection of the input shaft 18 and the screw 28 is made with a gap n.
The gap is chosen from the condition of ensuring the full stroke of the spool.
In addition, the input shaft 18 is connected by a torsion bar 20 to the screw 28 of the steering mechanism.
A non-return valve 7 is screwed into the channel of the middle annular bore E.
The power steering works as follows.
When the car moves in a straight line, the spool 5 (Fig. 5) occupies a neutral position and the working fluid from the pump 18 flows to the middle annular bore E (see Fig. 4) of the spool housing through the oil pipeline 11 (see Fig. 5) and through extreme bores C and D (see Fig. 4) - to the drain through the oil pipeline 13 (see Fig. 5), while filling the reactive chambers between the plungers 6 and through channels K and D (see Fig. 4) in the housing along oil pipelines 8 (see Fig. 5) and 12 - the cavity of the power cylinder 17.
When the steering wheel is turned counterclockwise and, consequently, the input shaft 1, due to the screw connection, the sleeve 3 with the spool 5 fixed to it moves axially upward along the splines of the shaft 7.
At the initial moment of displacement, when the pressure in the system is insignificant, the force on the steering wheel is mainly created by the torsion bar 2, which directly acts on the input shaft 1.
At the same time, the screw connection moves the spool and is practically not loaded.
When the spool is displaced, the value of which is limited by the gap n in the spline connection, the access of the working fluid to the annular bore C is stopped (see Fig. 4).
The working fluid from the pump is supplied to the middle bore E, and then through the channel K in the housing and the oil line 12 (see Fig. 5) enters the sub-piston cavity of the power cylinder 17, as a result of which the piston 19 with the rod 16 moves, turning along clockwise, the sector shaft with the steering arm 14, and through the steering longitudinal rod 15 turns the steered wheels to the left.
From the rod end of the power cylinder, the working fluid flows through oil line 8 and channel E (see Fig. 4) in the housing toannular boring D and further along the oil pipeline 13 (see Fig. 5) into the oil tank 10.
When the steering wheel is turned clockwise, bushing 3 with spool 5 moves down.
The supply of working fluid to the annular bore D (see Fig. 4) is stopped.
The working fluid from the pump enters the middle bore E and then through channel F and oil line 8 (see Fig. 5) into the rod end of the cylinder.
The piston with the rod moves by turning the steering arm 14 counterclockwise, and through the longitudinal rod turns the steered wheels to the right.
From the under-piston cavity of the cylinder, the working fluid flows through the oil line 12 and channel K (see Fig. 4) in the body into the annular bore C and then through the oil line 13 (see Fig. 5) into the oil tank.
With an increase in the moment of resistance to the rotation of the steered wheels, the pressure of the working fluid in the system and, consequently, in the jet chambers increases, which causes a proportional increase in the effort on the steering wheel.
Thus, the driver has a "feeling of the road".
When the force is removed from the steering wheel, the torsion bar 2 and plungers 6 return the spool to the neutral position.
When the pump is not working or the hydraulic booster is not efficient enough, a gap (n) is selected in the spline connection of the input shaft 1 with shaft 7 and the force from the steering wheel is transmitted as in steering without power steering.
At the same time, the check valve 9 bypasses the working fluid from one cavity of the power cylinder to another.
Possible malfunctions of the steering and methods for their elimination
Increased effort on the steering wheel when turning right and left:
- Lower oil level in the reservoir - Open the reservoir and, with the engine running, fill it with oil at least up to the upper mark on the dipstick. Check system for leaks and repair if necessary
- There is air in the hydraulic system - Check suction port and pump shaft seal for leaks. Bleed the hydraulic steering system and add oil
- Power cylinder piston seal damaged - Replace the power cylinder piston seal and, if necessary, tighten the piston nut on the rod
- The performance of the pump flow and pressure valve is impaired (foreign particles enter under the ball or between the plunger and the flow and pressure valve body) - Remove the spring-loaded plunger from the pump, disassemble, rinse and check. Wedging of the plunger in the pump housing is not allowed
- The pressure relief valve plunger does not return after turning the steered wheels to the extreme left or right position - Remove the pressure relief valve, wash, clean, eliminate stuck plungers
Poor vehicle handling when driving straight ahead:
- Lower oil level in the reservoir - Fill the reservoir with oil to the upper mark, with the engine running
- When the oil level is normal, air enters the system - Eliminate air leakage and bleed the hydraulic system
- Steering gear itself is loose or spring ladders are loose - Check and fix the problem
- Wheels misaligned - Adjust toe-in
- Increased steering shaft play - Adjust screw bearing preload and mesh clearance
- Radial play in steering column cardan shaft - Replace cardan shaft
High effort on the steering wheel at higher speeds:
- Flow and pressure valve malfunction - Remove the plunger from the pump, disassemble, flush and check
- Pump not supplying enough oil due to worn parts - Replace pump
Vibration on the steering wheel while driving:
- Steering wheels or brake drums out of balance - Balance or replace steering wheels and brake drums
Spontaneous turning of the steered wheels to the end position:
- Input shaft and spool actuator sleeve not connected correctly - Remove distributor and properly connect input shaft to spool actuator sleeve
Increased noise during pump operation:
- Reduced oil level in reservoir
- Air in oil - Fill reservoir with oil
- Check suction port and pump shaft seal for leaks.
- Bleed hydraulic steering system and add oil