Steering Overview
Steering
Overview
1. Steering column
2. Steering shaft
3. Inner seal
4. Outer seal
5. Tie rod
6. Steering gear
7. Servo pump
8. Filling container for servo oil
9. Heat shield
10. Pump motor
11. Electrical power steering module (EPS).
Mechanical
Mechanical steering wheel movements are transferred to the wheels via the steering column (1), steering shaft (2), steering gear (6) and tie rods (5). The wheel deflection is limited by a stop in the steering gear.
Hydraulics
The steering system is electro-hydraulic and is servo operated. The electric power steering module (EPS) (11), pump motor (10), oil reservoir (8) and servo pump (7) constitute a single unit.
The steering gear is of the rack and pinion type and grease lubricated.
It is installed with two screws in the sub-frame.
The total oil volume in the steering system is 1.2 liters.
The oil level is checked with the aid of the filling container (8).
The outer seal (4) is secured with catches in the steering gear pinion housing. The inner seal (3) is secured with plastic mounting elements against the cowl panel from inside the passenger compartment. The seals prevent sound from the engine compartment being transferred into the passenger compartment. They also seal against water, dirt and fire.
The heat shield (9) is secured to the steering gear housing using three screws. It protects the steering gear from heat radiation from the three-way catalytic converter (TWC), exhaust pipe and turbocharger (TC).
Adaptive steering column
The adaptive steering column is a complete unit. It contains the following components:
1. Fixed bracket
2. Running bracket
3. Upper steering section
4. Adjuster lever
5. Lock mechanism
6. Upper joint
7. Lower joint
8. Steering shaft.
The fixed bracket (1) is mounted in a bracket on the pipe arm and the cowl panel.
The steering column is adjustable for both height and reach.
It has an electrical steering lock with a mechanical locking function.
The steering shaft is divided into two parts and has two joints. A joint between the upper and lower steering shaft sections and a joint as the connection to the steering gear.
Steering gear
1. Input shaft
2. Torsion bar
3. Dust boot
4. Seal
5. Rotary valve
6. Seal
7. Journal bearing
8. Gear drive
9. Actuating piston
10. Bearing
11. Steering gear housing
12. Rack
13. Cylinder pipe
14. Tie rod
15. Protecting bellow
16. Seal
17. Internal pipe.
This description refers to the steering gear on left-hand drive vehicles. The gear in right-hand drive vehicles is a mirror image of the left-hand drive version.
The steering gear is of the rack and pinion type with the mechanical and servo assisted elements combined in one module.
The mechanical element consists of the gear drive (8), steering rack (12) and tie rods (14).
The gear drive is carried by a journal bearing (7) and a roller bearing (10) in the steering gear housing.
The steering rack is carried by a journal bearing on the right end and in the housing is guided by the gear drive (8) and the sprung actuating piston (9).
A cylinder pipe (13) is secured to the steering gear housing (11). This pipe functions as the power steering working cylinder for the hydraulic piston fastened to the steering rack.
The oil flow to the hydraulic cylinder is regulated in the valve housing which is integrated into the steering gear housing.
Valve assembly
The gear drive is driven by the steering gear input shaft (1) which has exterior lugs. There is radial play between the lugs.
A torsion bar (2) which joins the input shaft to the gear drive holds the lugs in a position where the play is equal on each side when there is no steering input on the shaft.
The torsion bar is pressed into the gear drive. The gear drive is fastened to the input shaft with a pressed in lock pin.
A rotary valve (5) is located in the valve assembly and fixed to the gear drive with a lock pin. The valve operating range is radial between four narrow vertical channels in the rotary valve and four milled grooves in the input shaft.
The valve is balanced as a complete unit and cannot be rebalanced.
Electrical servo pump
1. Electrical power steering module (EPS)
2. Oil reservoir and servo pump
3. Pump motor and sealed control module
4. Filling container for servo oil
5. Steering gear.
The electric power steering module (EPS) (1), pump motor (3), oil reservoir and servo pump (2) constitute a replaceable unit.
The electrical connections for the control module are located on the top of the control module.
The servo pump contains a gear pump and a pump motor. The pump is located in the oil reservoir (2). The pump motor (3) is located under the oil reservoir. The pump motor is a DC motor containing no brushes. The pump motor has four rotary windings. The control module is sealed in the pump motor.
For more detailed information about the electric power steering module (EPS), see Design and Function, electric power steering module (EPS).