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

©

200436

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