POWER RACK AND
POWER RACK AND
PINION STEERING
PINION STEERING
A typical power rack-and-pinion steering assembly is used on many
cars. This rack-and-pinion assembly is a hydraulic-mechanical unit with an
integral piston and rack assembly. An internal rotary valve direct power
steering fluid flow and controls pressure to reduce steering effort.
When the steering wheel is turned, resistance created by the weight of the
car and tires-to-road friction causes a torsion bar in the rotary valve to
deflect. This changes the position of the valve spool and sleeve, thereby
directing fluid under pressure to the proper end of the power cylinder.
The difference in pressure on either side of the piston (attached to rack)
helps move the rack to reduce turning effort. The fluid in the opposite end
of the power cylinder is forced to the control valve and back to the pump
reservoir. When the steering efforts stops, the control valve is centered by
the twisting force of the torsion bar, pressure is equalized on both sides of
the piston, and the front wheels return to the straight ahead position.
POWER RACK AND PINION
STEERING
Steering Column
Power Steering Pump
Power Steering Gear
POWER RACK AND PINION
STEERING
System construction
System construction
POWER RACK AND PINION
STEERING
The rack-and-pinion power steering system consists of:
-

inner rod to shorten or lengthen the tie rod assembly.
POWER RACK AND PINION
STEERING
POWER RACK AND PINION
STEERING
1. Tie rod end
2. Lock nut
3. Boot clip
4. Boot
5. Boot wire
6. Inner ball joint
7. Rack bushing
8. O-ring
9. Seal
10. Lock nut
11. Yoke plug
12. Spring
13. Support yoke
14. Snap ring
15. Seal
16. Bearing
17. Pinion shaft assembly
18. Bolt
19. Valve housing
20. O-ring
21. Steering gear housing
22. Mounting rubber
23. Mounting bracket
24. Oil pipe
25. Rack

Bearing
[Section A-A]
Cutaway of a Rack-and-Pinion
steering gear
Cutaway of a Rack-and-Pinion steering gear
POWER RACK AND PINION
STEERING
To cylinder tube right chamber
To cylinder tube left chamber
Torsion bar
Rotary valve
Input shaft
To oil reservoir
From oil pump
[Section B-B]
Operation of the pinion and valve assembly (at the center position)
POWER RACK AND PINION
STEERING
Chamber “A”
Port a
Port d
To the left
cylinder tube
From the oil pump
To the right cylinder tube
Port c
Port b
Operation of the pinion and valve assembly (at the center position)
POWER RACK AND PINION
STEERING

Port b
Port a
Operation of the pinion and valve assembly (turning left)
POWER RACK AND PINION
STEERING
Oil pump
Oil reservoir
R’
Oil passage-way R
Oil passage-way L
L’
Operation of the pinion and valve assembly (turning left)
POWER RACK AND PINION
STEERING
Oil reservoir
Oil pump
Sleeve c
Chamber “A”
Port b
Sleeve b
Sleeve a
Sleeve b
Port d
Port a
Port c
Operation of the pinion and valve assembly (turning right)
POWER RACK AND PINION
STEERING
Chamber “A”
Port d

left chamber
Cylinder tube right chamber
Chamber “A”
Torsion bar
Input shaft
Sleeve b
Port b
Sleeve b
Rotary valve
Sleeve a
Sleeve c
Port a
POWER STEERING PUMP
Oil pump construction
1. Pulley
2. Shaft
3. Pressure switch
4. P/S pump body
5. Flow control valve ass’y
(built in relief valve)
6. Cam ring
7. Rotor
8. Vane
9. Cover
Oil pump construction
POWER STEERING PUMP
Operation of the oil pump
POWER STEERING PUMP
Intake side
Vane