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The Principle of Power Steering Gear

Power steering gear is one kind of hydraulic unit which using the power of engine to change the car direction. The engine drives the oil pump to create hydraulic pressure, then the hydraulic pressure affects on the power cylinder piston, making the pinion produce auxiliary force to the rack. The auxiliary force is concerned with the piston pressure. Therefore, if more steering power is needed, the pressure should be increased. The hydraulic pressure is controlled by the control valve linked to the steering shaft.

The Function of Power Steering Gear

When turning, the steering gear reduces the operation strength on the steering wheel; controls the returning speed of the steering wheel. When turning in place, it can provide essential force. It is sensitive to steering, convenient to operate, and needs little power on the steering wheel so as to reduce the labor intensity of the driver. Provide the fast driving cars with stable steering ability. When the steering device expires, it can maintain the mechanical steering system work effectively. It can absorb the shock to the front wheel which come from the road, and reduce the impact to the steering wheel. (The power steering system consists of steering tank, steering pump, steering column and steering gear.)

The rotary valve structure power steering gear

It generally operates with the ceaselessly working steering oil pump. The pump absorbs oil from the oil tank and supplies it to the power steering gear control valve. When the gear is still, the control valve is often in the middle position. And the oil goes right through the control valves back to the oil tank.


The Functional Scheme of the Power Steering System



The Middle Position

When the car runs straight (steering wheel fixed), oil pump supplies hydraulic oil from the oil inlet. After running through the gap (see chart ), the oil flows into two working chambers. Because right now the rotary valve is motionless, the two working chambers have the same oil pressure and do not produce power. Then, the hydraulic oil comes back to the oil tank.

Steering Process

When rotating the steering wheel, the gap between the spool and the valve changes, making the oil differential pressure in the two working chambers corresponds with the steering resistance. The oil differential pressure acts on the rack piston to drive it to overcome the steering resistance and produce displacement, thus making the front wheel rotate.

Returning Process

After finishing rotating, the force on steering wheel disappeared. In the effect of aligning torque produced by the internal torsion bar and front wheel, the oil differential pressure in the two working chambers disappears. The steering wheel will back to the position of running straight.

The Steering Feeling

The steering feeling effect is the ability to feel rotating. When the driver exerts force on the steering wheel, at the same time acts on the steering gear to make it turn around and make the torsion bar twist. The deformation depends on the steering resistance, the larger steering resistance, the deformation also increased. So the driver can judge the resistance according to the force he acted on the steering wheel so as to get "the steering feeling" effect.

The Structure Principle of Power Steering Gear

It is a rack and pinion steering gear. On the back of the pinion, there is an adjustive semicircle. It is pressed on the rack by the pressure come from the spring so that the rack can touch the pinion with appropriate pressure. The gap in the steering mechanism is adjusted by the adjustive semicircle and the spring.





1.adjustive nut 2.adjustive screw 3. adjustive spring 4.adjustive semicircle 5.adjustive semicirle gasket 6.bottom shell bearings 7.end plate nut 8.end plate screw 9.bottom shell 10.oil tank 11.long oil pipe 12.short oil pipe 13.under-chassis 14.tube ferrule 15.dust cover 16.strap 17.tie rod nut 18.tie rod end assembly 19.valve tooth bearings 20.valve tooth oil seal 21.valve tooth 22.valve body 23.valve body seal ring 24.spool 25.top shell bearings 26.top shell oil seal 27.top shell 28.shell connecting screw 29.rack 30.piston seal ring 31.O-ring piston 32.piston 33.piston jump ring 34.high-pressure oil seal 35.sliding bearings 36.oil tank oil seal covering1 37.oil tank oil seal covering2 38.oil tank jump ring

Its main design parameters are as follows

Example:

Transmission Ratio 46.67
Center Distance 20mm
Total Turning Circles 3.3±0.1
Route 158mm
Fan Modulus 1.85
Direction Left
The Highest Working Pressure 8.5Mpa
Input Torque 4-6N.m
Output 8157N
Diameter
Rack
Φ35、Φ36、Φ38、 Φ39、Φ40、41、 Φ42、Φ42.5、Φ43、 Φ43.5、Φ44、Φ45、 Φ46、Φ48、Φ49、Φ50、Φ52、Φ53、 Φ55、Φ56 Φ22、Φ23、Φ24、 Φ25、Φ26、27、
Φ27.7、Φ28、 Φ30、 Φ32、Φ35、 Φ38

The Traits of the Rack and Pinion Steering Gear

Rack and pinion steering gear has a simple structure, easy design procedure, high transmission efficiency. It is produced by the completely sealed devices, so it is reliable. In foreign countries, it is widely used many years ago. But due to the low transmission ratio, the use of this steering gear is restricted. At present it is more used in mini cars. In the rack and pinion steering gear, there is a cylindrical gear in the end of steering shaft. It meshes with the rack in hull which is fixed in the car frame. The rack is linked by two ball joints and two tie rods. It directly drives the tie rods to move to make the car rotate. If the parts in the rack and pinion steering gear wear and the gap appears, the force of the spring will push it to the platen, so as to keep it mesh with the rack, so that the steering wheel is in an appropriate space and raise the manipulation of sensitivity

The Advantages of Rack and Pinion Steering Gear

Rack and pinion steering gear, with no pitman arm axis and rocker unit etc, is simple, easy to decorate, convenient to produce, reliable and has long operating life. Therefore, it is widely used in light, miniature cars.

Installation Instruction

The use of steering oil pump:
Choose the right oil pump according to the vehicle performance requirements and power steering gear basic parameters.
The use of oil:
The steering system should be filled with steering fluid according to the criterion. The gear oil which is 26mm2/S viscosity (temperature 50℃) and freezing point less than -35℃ is recommended. And the recommended criterion will be Dexron or Mercon-M. The oil temperature in power steering gear should between -40℃ and 120℃. 
Filter: net type filter
When installing the power steering gear, there is no use to adjust it.

Announcements


* The oil pipe should be installed correctly. Do not mix up the inlet with the outlet; otherwise the power steering gear will be damaged.Always keep the inside of power steering gear clean.
* The power steering gear is operated by the car engine which drives the oil pump, so the car must not slide when flameout, otherwise it will cause steering problem.
* The driver cannot turn the power steering gear to the limit for more than 5 seconds. Please turn it a little back when you turn it to the limit, otherwise the oil pump may be damaged.
* The spool has been adjusted to its best state and other parts should not be dismantled.
* The oil seal and the junk ring which dismantled when repairing should not be used again.
* The oil refueled should be the same as the original one.
* If the hydraulic system breaks down and cannot work, the driver should increase strength so as to rotate the car temporarily.
* The power steering gear is usually brought back to our service center to be repaired
* When you assemble and dismantle the power steering system, please don't strike or hit the parts strongly, and please keep it clean, any foreign material in the steering system is forbidden.

The Correct Usage and Maintenance of the Power Steering Gear Power Steering Gear Installation Scheme

Care and Maintenance

1.For new power steering kits, please change the automatic gear oil after first running 2500km. Afterwards please change the oil and clean the oil tank for each 50000km running or each year.
2.Please check the oil lever and oil quality each month and fill the oil to the right lever. If you find the oil with many dirties, please change it.
3.Always check and maintain the tire pressure be in accordance with the provisions.
4.The procedure of changing oil or refueling
(1)Put up the epipodium.
(2)Open the lid; unscrew the bolt on the oil outlet and discharge the bottom oil (in idling state). And turn the steering wheel to the limit in both directions for several times until no oil left in the oiler.

(3)Tighten up the bolt on the oil outlet (to keep it clean and in case of dirties).
(4)Refuel in the oiler.
(5)When the car in idling, turn the steering wheel to the limit in both directions for several times until the oil level is stable and no bubble produced.
(6)Refuel until it reaches the mark.
(7)Tighten the oiler lid.

Common Faults and Solutions
1.Steering system of any fault will affect the traffic safety and may cause failure. So the steering system must often be checked.

 

Problem Cause Solution

oblem of rotating The tire pressure is insufficient, engine works unstably To charge the tire and adjust the engine
The caster is too large Check the wheel alignment
Cardan joint wear Change the cardan joint
Ball-and-socket joint wear Change the joint
The steering column gets stuck Check the steering column
The piston wear and the rotary valve gets stuck Repair the steering gear
Too low oil pressure Change the oil pump
Overloading Load shedding
Steering pump Check the steering pump control valve and clean the entire steering system or change the oil cup in necessary.
The belt or the pump gets loose Adjust the belt according to the regulations
There is air in the steering gear Discharge the air
The bolts in the oil pipe gets loose, causing oil leakage Check the oil pipe and tighten the bolts
Problem with rotating 
to one direction
Too low pressure in the tire To charge the tire
One side leakage Repair the steering gear
The rotary valve is not in the middle position
Can not produce pressure in both left and right sides Change the sealing element
Problem with rotating There is air in the connection of the outlet, the inlet, the oil pump and the engine Tighter the joint or change the sealing element
Too low oil pump flow Change the oil pump
Steering wheel shakes The steering wheel and steering shaft gets loose Steering ransmission devices connecting parts get loose The bolts in the steering or the holder gets loose Tighten the loose
Front wheel bearing wear Change the front wheel bearing
Principle axis wear Change the axis
Ball-and-socket joint wear Check the ball-and-socket joint
Ball joint wear or tie rod wear Change the ball joint or tie rod
The wheel gear wear Repair the wheel gear
Too high temperature Too large oil pump flow Change the oil pump
Not free oil flow Change the oil pipe
Turning to the limit takes more than 5 seconds Avoid turning to the limit
Unstable steering The parts in steering system gets loose or is worn Tighten or change
Too little oil Refuel
The bolts in the cardan joint gets loose Tighten the bolt
Poor return-ability The steering wheel gear wear Adjust or repair the steering wheel gear
The steering belt gets loose Adjust the belt
Too little hydraulic oil in the reservoir Check the reservoir
The power steering gear breaks down Check the steering device
Inappropriate tire charging Charging according to the criterion
Inappropriate wheel alignment Check the front wheel alignment
The steering column gets stuck Check the steering column
Noise The steering gear connection gets loose Tighten the steering gear connection
Cardan joint wear Change the cardan joint wear
The wheel gear wear Repair the wheel gear
Deviation Inappropriate front wheel alignment Adjust the front wheel alignment
The rack in the steering gear gets loose Adjust or repair the rack
The steering gear connection is twisted or worn Change the steering gear
Steering fluid produce bubbles There is air in the steering system

Discharge the air an check whether it licks
There is liquid leakage in the steering system

Check the oil cup and refuel

Steering system 
produce noise
There is air in the steering system Discharge the air and check whether it licks
No noise elimination function Use the oil pipe with noise elimination function
Problem with the steering gear valve Change the steering gear

It is dirty inside the steering system

Clean the oil pipe, oil cup, oil pump and steering gear.

2.Check the oil Pressure

Power steering gear system's faults are usually caused by steering difficulty of no auxiliary force. In this case, make clear whether the problem lies in the pump or the cabinet. To do this, use the pressure gauge to check the pressure.


a. Check the pressure after shutting off the valve
Shut off the valve of the pressure gauge and read the pressure rating.
Minimum pressure: 80 kg/cm²(7.8Mpa)
Notice:
● Do not shut off the valve for more than five seconds in case of explosion.
● The temperature should be lower than 80℃.
● If the pressure is low, repair or change the steering pump.

b. Check the differential pressure
Check and record the pressure at 1000 revolution/minute
Check and record the pressure at 3000 revolution/minute
Compare the differential pressure. If it is more than 5 kg/cm²(4.9Mpa), than it should be repaired or the pump should be changed.

c. Check the pressure of rotary valve
Make sure the pressure gauge is in work and the engine is operating slowly.
Minimum pressure: 80 kg/cm²(7.8Mpa)
Notice:
● Do not activate the steering valve for more than five seconds.
● The temperature should be lower than80℃.
● If the pressure is low, it is caused by interior leakage. The power steering gear should be repaired or changed.

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