DAF CF65, CF75, CF85 Series . Manual - part 959

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General

STEERING BOX

ΧΦ65/75/85 series

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2. GENERAL

2.1 OVERVIEW DRAWING, STEERING BOX

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1.

Attachment pin, torsion bar

2.

Input shaft

3.

Pressure-limiting valve

4.

Cover

5.

Torsion bar

6.

Control valve

7.

Bushing

8.

Attachment pin, torsion bar

9.

Wheel deflection limiting valve

10.

Ball nut

11.

Sector shaft

12.

Worm shaft

13.

Piston

14.

Wheel deflection limiting valve

15.

Housing

16.

Adjusting bolt, wheel deflection limiting 

valves

STEERING BOX

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General

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ΧΦ65/75/85 series

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2.2 OPERATION OF THE STEERING BOX

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General

STEERING BOX

ΧΦ65/75/85 series

7

3

Hydraulic power steering
The oil flow in the steering box is controlled by the 

control valve (6).

The control valve (6) consists of a bushing (7), 

which is attached to the input shaft (2) and the 

space in the worm shaft (12).

On the outside, the bushing (7) has a number of 

recesses. The delivery line and the return line 

and the channels leading to the cylinder halves 

end in the chamber of the worm shaft (12). The 

delivery line and the return line can be connected 

to the channels leading to the cylinder halves 

through the recesses of the bushing (7).

If the bushing (7) is turned in relation to the space 

in the worm shaft (12), one cylinder half connects 

to the delivery line and the other to the return line. 

If the input shaft (2) is turned the other way, the 

bushing (7) will switch the delivery line and return 

line connections to the cylinder halves.

Because the control valve (6) increases the oil 

flow to one side of the piston during steering and 

connects the other side of the piston to the return 

line, the oil can no longer circulate through the 

steering box. As a result, pressure builds up on 

one side of the piston and the piston moves.

If no steering takes place, the control valve (6) is 

in its neutral position. In the neutral position the oil 

flow to the left-hand and the right-hand side of the 

piston is such that the forces exerted on the 

piston by the oil are equal. Therefore, the piston 

will not move. This is called the "hydraulic central 

position" of the steering box. The oil pressure in 

this situation is called the circulation pressure.

The neutral position of the steering box is factory-

set and cannot be changed.

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STEERING BOX

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General

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ΧΦ65/75/85 series

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A torsion bar (5) is fitted between the input 

shaft (2) and the worm shaft (12) and connected 

to the input shaft (2) and the worm shaft (12) 

using pins (1) and (8).

While steering, the input shaft (2) will turn in 

relation to the worm shaft (12), resulting in a 

twisting movement of the torsion bar (5). The 

torsion bar (5) ensures that when no torque is 

exerted at the input shaft (and steering no longer 

takes place), the input shaft (2) is returned to its 

neutral position in relation to the worm shaft (12). 

As a result, the control valve (6) also returns to 

the neutral position and the hydraulic power 

steering is deactivated.

Pressure limiting
The pressure-limiting valve (3) protects the 

system from excessive system pressures. If the 

preset valve pressure is reached, the valve opens 

and connects the delivery line to the return line.

Bleeding
The steering box is auto-bleeding.

At circulation pressure, the steering box auto-

bleeds. At a higher system pressure, the bleeding 

system is closed.

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