DAF 95XF. Manual - part 407

4

XF ENGINE BRAKE

General

95

XF series

2-12

Hydraulic control of the exhaust valves
To open an exhaust valve hydraulically at the
end of a compression stroke, optimal use is
made of the valve diagram.
This means that the DEB uses an exhaust valve
rocker of one cylinder to open an exhaust valve
for another cylinder.

Cylinders 1, 2 and 3
Exhaust valve rocker of cylinder 1 hydraulically
opens the exhaust valve of cylinder 3

Exhaust valve rocker of cylinder 2 hydraulically
opens the exhaust valve of cylinder 1

Exhaust valve rocker of cylinder 3 hydraulically
opens the exhaust valve of cylinder 2

Cylinders 4, 5 and 6
Exhaust valve rocker of cylinder 4 hydraulically
opens the exhaust valve of cylinder 5

Exhaust valve rocker of cylinder 5 hydraulically
opens the exhaust valve of cylinder 6

Exhaust valve rocker of cylinder 6 hydraulically
opens the exhaust valve of cylinder 4

1

3

2

4

6

5

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4

95

XF series

General

XF ENGINE BRAKE

2-13

Preventing the exhaust valve from opening
too far
Inside the set screw (10) is a spring-loaded pin.
This pin projects approx. 2.7 mm from the set
screw (10).
The operating piston (3) has a hole which is
closed by the pin in the set screw (10).
If the operating piston (3) is hydraulically moved
too far down, the hole in the operating piston (3)
will no longer be closed. Oil in the high-pressure
area escapes via the hole in the operating
piston (3), preventing the exhaust valve from
opening any further.

Position A:
Operating piston inactive.

Position B:
Operating piston during regular operation.

Position C:
Operating piston hydraulically opened too far, oil
pressure is discharged via the operating piston.

A

B

C

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10

3

10

3

10

3

4

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4

XF ENGINE BRAKE

General

95

XF series

2-14

Protection against excess lubricating-oil
pressure
There are 2 springs above the control valve.
When the DEB is switched on, the control valve
will be moved upwards by the engine oil
pressure against the direction of the pressure of
the inner spring.
This clears the way for the lubricating oil to pass
to the high-pressure area of the DEB.
If the lubricating-oil pressure in the engine is too
high (



 8 bar), the control valve will be moved

upwards against the pressure of both springs.
The control valve will move up further than
usual, preventing the route to the high-pressure
area of the DEB from being cleared.
The DEB will not function in this case.

Note:
A pressure in excess of 8 bar may result from:
-

cold lubricating oil

-

defective lubricating-oil pressure-relief valve

Position A:
DEB switched off

Position B:
DEB switched on
Lubricating-oil pressure between 1.5 and 8 bar

Position C:
DEB switched on
Lubricating-oil pressure 



 8 bar

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A

B

2

C

2

4

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4

95

XF series

General

XF ENGINE BRAKE

2-15

2.6

DESCRIPTION OF EXHAUST BRAKE SYSTEM

i 400185

4

3

1

5

2

1.

Engine stop operating cylinder

2.

Butterfly valve operating cylinder

3.

Engine stop valve

4.

Supply pressure

5.

Butterfly valve housing

4

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