Function

Function

Steering, adaptive steering column




1. Fixed bracket
2. Running bracket
3. Upper steering section
4. Adjuster lever
5. Steering shaft
6. Tear plate
7. Pin (only USA/CDN)
8. Explosive charge (only USA/CDN)
9. Steering lock.

Deformation in the event of a collision
An impact of approximately 2 kN is required for the steering column to start to deform. Deformation takes place in three stages:
1. The upper steering section (3) is pushed into the running bracket (2) equivalent to the remaining potential adjustment in the adjustment mechanism (4)
2. The tear plate (6) is deformed. The running bracket (2) is pushed into the fixed bracket (1). The groove for the running bracket controls the length of deformation
3. The steering shaft (5) with its telescopic design slides together.
The maximum movement (deformation) of the steering column is approximately 95 mm.

Collision process (only USA/CDN)
Driver not wearing seat belt:
The pin (7) engages. This results in the tear plate using its entire structure to absorb energy. The deformation takes place stiffly and slowly.
Driver wearing seat belt:
The explosive charge (8) is activated and pushes down the pin (7) out of the tear plate (6). The tear plate is weakened and the kinetic energy of the collision is transferred on in the system. This produces a relatively soft deformation process.
The collision protection system only works if the driver is wearing a seat belt and the airbag deploys.

Collision process (not USA/CDN)
The steering column does not have an explosive charge. The pin (7) is therefore always engaged. This means that the tear plate (6) uses its entire structure to absorb energy, irrespective of whether or not the driver is wearing a seat belt. The deformation takes place stiffly and slowly.

Electrical steering lock with mechanical locking function
The steering lock (9) is secured in the steering column with two security bolts.
The mechanical locking function for the locking mechanism consists of:
- a lug on the steering wheel lock
- a pipe and catch on the steering column
- a pin for locking the lug.
The lug is pushed into the tube with the catch, locking the steering wheel. In the event of damage to the steering lock cover, the pin blocks the lug in the locked position.

Steering, steering gear




1. Neutral
2. Steering left
3. Steering right
4. Servo oil, free flow
5. Servo oil, high pressure
6. Servo oil, low pressure
7. Air.
The steering gear power steering function is schematically displayed in the above illustration and under Steering, valve section.
The force of oil pressure built up in the power steering pump affects the piston on the steering rack. The oil flow to the right or left-hand side of the piston is regulated in the valve housing. External pipes lead to both sides from the valve housing. The power steering pump pressure hose is connected to the valve housing.
The valve spool has three radial grooves, a small one that is fed by the power steering pump and an upper and a lower groove that are connected with the working cylinders via the outer pipe.

Steering, valve section





Neutral
1. To the right-hand side of the piston
2. To the left-hand side of the piston
3. Outward
4. Fluid return
5. Servo oil, free flow
The valve is open when the vehicle's engine is running and there is no steering input. In the open position, none of the ducts to the operating cylinders are blocked. The servo oil circulates freely through the valve.





Steering left
6. Servo oil, low pressure
7. Servo oil, high pressure
When the steering wheel is turned to the left and the wheel resistance is so great that the torsion bar inertia is overcome, the steering gear input shaft moves to the left in relation to the worm screw, within the play between the lugs.
With this movement the input shaft stops the free flow through the valve and sends the fluid through the upper feed pipe to the right-hand side of the piston.
As long as the torsion bar is affected by steering input, the oil pressure continues to push the steering rack to the left and servo assistance is obtained. If the steering input reduces, the torsion bar springs back. The valve section then reverts to the center position so that the oil can circulate freely through the valve housing.





Steering right
6. Servo oil, low pressure
7. Servo oil, high pressure
The function when turning right is, in principle, the same as to the left. The only difference is that the steering gear input shaft stops the flow of high pressure oil through the return and down through the groove on the inside of the valve and out through the low pressure pipe to the left-hand side of the piston.

Steering, electrical power steering module (EPS)
The power steering system employs the electro-hydraulic principle and is controlled by the electric power steering module (EPS).
Its task is to regulate the power steering affect for the vehicle optimally, using relevant input signals, and always to provide optimum servo assistance, regardless of whether the vehicle is stationary with the engine running or being driven at high speed.
The pump is a gear type pump.
The pump motor is controlled by the electric power steering module (EPS). The pump motor has Hall sensors, which inform the electric power steering module (EPS) about the present pump motor speed. At the same time, information is provided about the relevant hydraulic pressure, which is indirectly dependent on the speed.
For further information about the electric power steering module (EPS), see Design and Function, electric power steering module (EPS).