DAF LF45, LF55 Series. Manual - part 449

©

 200436

2-17

Description of components

OPERATION OF BRAKE COMPONENTS

ΛΦ45/55 series

6

3

Reducing pressure at connecting point 2
By activating the magnet coil (9), the solenoid 

valve (11) will open bore 15 and close bore 22. As 

a result, input pressure enters space 15 above 

diaphragm 5 via a bore. Diaphragm 5 seals 

against seat 7, so that no more pressure can 

build up.

By activating the magnet coil (10) at the same 

time, bore 16 opens and bore 23 closes.

By opening bore 16, the pressure under 

diaphragm 6 can be reduced via the bleed vent. 

The pressure in the brake chamber can now 

escape via connecting point 2, space 20 and an 

internal bore to the bleed vent.

6

19

20

16

7

5

10

22

11

15

9

12

4

23

2

1

R600630

P  (bar)

t (sec)

2

OPERATION OF BRAKE COMPONENTS

2-18

©

 200436

Description of components

3

ΛΦ45/55 series

6

Maintaining pressure at connecting point 2
By deactivating the magnet coil (10), the input 

pressure can be guided through a bore past the 

magnet coil (10) into space 19 under diaphragm 

6, thus sealing off diaphragm 6.

The pressure in the brake chamber can now no 

longer be guided to the bleed vent via space 20.

This keeps the pressure in the brake chamber 

constant.

R600631

2

1

6

20

19

16

10

12

23

P  (bar)

t (sec)

2

©

 200436

2-19

Description of components

OPERATION OF BRAKE COMPONENTS

ΛΦ45/55 series

6

3

2.10 TWO-WAY VALVE

This valve is used in drum brakes as a double 

check valve, that is to say a safety measure so 

that the maximum service brake and parking 

brake cannot operate the wheel brakes at the 

same time.

Purpose
The purpose of this valve is to let through 

unchanged the highest of two submitted pressure 

signals.

Operation
When pressure is applied to one of the entrances 

or if the pressure on one entrance is higher than 

on the other, the little piston will shut off the other 

entrance and the air can leave the valve 

unhindered again via the exit.

No connection can be established between the 

two entrances.

11

21

12

R600747

OPERATION OF BRAKE COMPONENTS

2-20

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Description of components

3

ΛΦ45/55 series

6

2.11 ASR SOLENOID VALVE

The ASR valve serves to transfer brake pressure 

to the ABS valve during an ASR differential brake 

control. Depending on the slip, the ABS valve will 

control the brake pressure to the respective brake 

chamber.

The ASR valve is a simple electropneumatic 

valve, which is normally closed, that transfers air 

pressure when it is electrically energised.

The energising is controlled by the ABS/ASR 

electronic unit.

Note:

The bleed vent (3) must always point downwards.

If coil E of the ASR valve is energised, core B will 

move down against the pressure of spring F.

Seal A will now open connecting point 1, so that 

supply pressure can leave the valve via 

connecting point 2. Opening C and therefore 

bleed vent 3 are also closed as core B moves 

downwards.

When coil E is no longer energised, core B will 

move upward under the influence of spring F.

This action will close connecting point 1 and open 

opening C. Connecting point 2 is now linked to 

bleed vent 3.

R600601

2

3

C

B

D

E

F

A

1

4