DAF CF65, CF75, CF85 Series . Manual — part 951

©

200423

2-9

General

STEERING GEAR, GENERAL

ΧΦ65/75/85 series

7

2

If the oil output of the main steering pump (4)

becomes too low, the dual-circuit valve (6) adds

the output of the emergency steering pump (13)

to the remaining output of the main steering

pump (4). The return pipe (8) of the main steering

pump is also cut off.

The output of both pumps is returned to the

emergency steering pump reservoir (10).

If more oil is supplied to the emergency steering

pump reservoir than is drawn in by the

emergency steering pump, the excess oil is

discharged to the main steering pump

reservoir (1) through the overflow pipe (9).

Dual-circuit valve
In the dual-circuit valve (6) an output

indicator (16) is fitted to signal that the oil output

from the main steering pump (4) is too low. The

output indicator (16) activates the circuit 1

warning indicator when the emergency steering

pump (13) is activated.

The output indicator for circuit 2 is fitted in pipe

connection (P2) (emergency steering pump (13)

delivery pipe connection on the dual-circuit

valve).

When the output from the emergency steering

pump (13) is too low, the output indicator

activates the circuit 2 warning indicator.

The emergency steering pump (13) is fitted with a

pressure limiting valve with a higher opening

pressure than the pressure limiting valve in the

steering box. The function of this valve is to serve

peak demands, which can occur when switching

circuit 2 on and off. When the valve opens, the

delivery pipe (14) is connected to the supply

pipe (12).

Operation of dual-circuit valve
When the engine is running, the pressure from

the main steering pump (P1) will cause control

slide A to move to the left against the spring

pressure. The supply from the main steering

pump goes to the steering box via exit (P). The

return from the steering box (R) is connected to

the main steering pump reservoir via exit (R1). At

the same time the connection of the emergency

steering pump (P2) and the steering box is

broken. The oil supplied by the emergency

steering pump while the vehicle is being driven

goes to the emergency steering pump reservoir

via entrance (P2) and exit (R2). Control slide B is

only used with vehicles equipped with a slave

cylinder.

S700935

1

C1

R1 R R2 P2

P

P1

C2

C

2

B

A

STEERING GEAR, GENERAL

2-10

©

200423

General

2

ΧΦ65/75/85 series

7

If a main steering pump failure causes the

pressure (P1) drop to zero while the vehicle is

being driven, the spring will move control slide A

to the right. As a result, the emergency steering

pump (P2) is connected to the steering box (P).

The steering power is now produced by the

emergency steering pump. To ensure that the oil

of the main steering pump does not leak away in

case of leakage, the return (R) of the steering box

is led to the emergency steering pump reservoir

(R2).

1

C1

R1 R R2 P2

P

P1

C2

2

S700936

B

A

C

©

200423

2-11

General

STEERING GEAR, GENERAL

ΧΦ65/75/85 series

7

2

2.8 SYSTEM DESCRIPTION, DUAL-CIRCUIT SYSTEM WITH SLAVE CYLINDER

The steering gear can contain a slave

cylinder (10) for additional steering power. This

slave cylinder is located parallel to the steering

box cylinder and is supplied with oil through the

dual-circuit valve.

System operation is identical to that of the dual-

circuit system.

Dual-circuit valve
The steering box is provided with an extra valve,

which cuts off the oil supply to the slave cylinder

(10) and connects both pipes (9) and (11) of the

slave cylinder when the output of the main

steering pump is too low. Just like the dual-circuit

valve this valve is operated by the emergency

steering pump pressure.

In the dual-circuit valve (6) an output

indicator (19) is fitted to signal that the oil output

from the main steering pump (4) is too low. The

output indicator (19) activates the circuit 1

warning indicator when the emergency steering

pump (16) is activated.

4

R1

R2

P2

P1

C1

C2

+

1

3

5

7

13

15

16

14

9

19

17

18

10

11

12

6

20

2

S700913

8

21

STEERING GEAR, GENERAL

2-12

©

200423

General

2

ΧΦ65/75/85 series

7

The output indicator (20) for circuit 2 is fitted in

pipe connection (P2) (emergency steering

pump (16) delivery pipe connection on the dual-

circuit valve).

When the output from the emergency steering

pump (16) is too low, the output indicator (20)

activates the circuit 2 warning indicator.

The emergency steering pump (16) is fitted with a

pressure limiting valve with a higher opening

pressure than the pressure limiting valve in the

steering box. The function of this valve is to serve

peak demands, which can occur when switching

circuit 2 on and off. When the valve opens, the

delivery pipe (17) is connected to the supply pipe

(15).

Operation of dual-circuit valve
When the engine is running, the pressure from

the main steering pump (P1) will cause control

slide A to move to the left against the spring

pressure. The supply from the main steering

pump goes to the steering box via exit (P). The

return from the steering box (R) is connected to

the main steering pump reservoir via exit (R1). At

the same time the connection of the emergency

steering pump (P2) and the steering box is

broken. The oil supplied by the emergency

steering pump while the vehicle is being driven

goes to the emergency steering pump reservoir

via entrance (P2) and exit (R2).

When the main steering pump is active, control

slide B moves to the left against the spring

pressure. Connections (C1) and (C2) of the slave

cylinder are connected to the connections on the

left (1) and right (2) of the steering box.

If a main steering pump failure causes the

pressure (P1) drop to zero while the vehicle is

being driven, the spring will move control slide A

to the right. As a result, the emergency steering

pump (P2) is connected to the steering box (P).

The steering power is now produced by the

emergency steering pump. To ensure that the oil

of the main steering pump does not leak away in

case of leakage, the return (R) of the steering box

is led to the emergency steering pump reservoir

(R2).

If the pressure of the main steering pump drops

to zero, the spring pressure will cause control

slide B to move to the right. The connections (C1)

and (C2) between the slave cylinder (1) and the

steering box (2) are closed off. At the same time

the slave cylinder connections (C1) and (C2) are

interconnected. While pressure is being built up

in the slave cylinder due to the different

capacities of the two chambers in the cylinder,

valve C will open.

S700935

1

C1

R1 R R2 P2

P

P1

C2

C

2

B

A

1

C1

R1 R R2 P2

P

P1

C2

2

S700936

B

A

C