DAF CF65, CF75, CF85 Series . Manual - part 950

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General

STEERING GEAR, GENERAL

ΧΦ65/75/85 series

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2.5 SYSTEM DESCRIPTION, SINGLE-CIRCUIT SYSTEM

From the reservoir (1) mounted over the steering 

pump (4), the oil flows through the supply pipe (3) 

to the steering pump (4).

The steering pump is a non-regenerative vane 

pump. When the pump is supplying output, the 

steering pump (4) does become regenerative, 

thus causing a negative pressure in the supply 

pipe (3).

The steering pump (4) pumps the oil through the 

delivery pipe (5) to the steering box (6).

From the steering box (6), the oil is returned to the 

reservoir (1) through the return pipe (7) via the 

filter (2). The return pipe (7) always has a low 

pressure.

The pressure in the delivery pipe (5) varies and 

depends on the steering force. If there is no 

steering action, the delivery pipe is at circulation 

pressure.

If a steering action takes place, the pressure in 

the delivery pipe can increase to the preset value 

of the pressure relief valve.

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ΧΦ65/75/85 series

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This maximum pressure can occur when the 

vehicle is steered while at a standstill on a skid-

resistant road surface or when the vehicle is 

parked against a curb and the steering wheel is 

turned.

When at maximum pressure a major 

transmission of energy will take place, resulting in 

the release of much heat. If this situation lasts too 

long, the steering pump can be damaged by the 

heat development.

The steering pump can develop very high 

pressure within a short period of time. This very 

high pressure can cause certain steering gear 

components to become overloaded or even to 

break off.

A pressure-limiting valve is intended to protect 

the steering gear against excessive pressure. 

The system pressure may not be increased.

The pressure-limiting valve is located in the 

steering box. This can be checked using the type 

plate on the steering box.

If a pressure value is mentioned on the type plate, 

the component concerned contains a pressure-

limiting valve.

It can be very dangerous to replace 

the steering box or the steering 

pump with a different type without 

DAF's express permission. Such 

replacements are therefore 

prohibited. If the original type is no 

longer available, DAF will supply 

another approved type.

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©

 200423

2-7

General

STEERING GEAR, GENERAL

ΧΦ65/75/85 series

7

2

2.6 SYSTEM DESCRIPTION, SINGLE-CIRCUIT SYSTEM WITH SLAVE CYLINDER

The steering gear can contain a slave cylinder (8) 

for additional steering power. This slave cylinder 

is located parallel to the steering box cylinder and 

is supplied with oil through the steering box.

System operation is identical to that of the single-

circuit system.

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ΧΦ65/75/85 series

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2.7 SYSTEM DESCRIPTION, DUAL-CIRCUIT SYSTEM

During normal operation, the engine-driven main 

steering pump (4) supplies oil to the dual-circuit 

valve (6), which is part of the steering box (7).

The oil arrives at the steering box (7) through the 

dual-circuit valve (6). 

The emergency steering pump (16) is attached to 

the gearbox and is driven by the gearbox output 

shaft. At a vehicle road speed exceeding approx. 

10 km per hour, the emergency fuel pump 

supplies sufficient oil. During normal operation, 

the oil from the emergency steering pump is 

returned to the emergency steering pump 

reservoir (13) via the dual-circuit valve (6).

Reservoirs (1) and (10) are interconnected by an 

overflow pipe (9). This pipe is connected in such 

a way that if one of the circuits leaks the other 

circuit remains functional.

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R1

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