[4matic] funkcjonowanie elektroniki, Mercedes
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28-030
Electronics
Electronic components
A1e17
ABS warning lamp
L6
Rear axle speed sensor
A1e24
ASD/4MATIC warning lamp
L6/1/2
Left and right front axle speed sensor
A1e25
ASD/4MATIC function indicator lamp
N30
ABS control unit
A7/2
4MATIC valve control unit
N30/3
4MATIC control unit
K1/2
Overvoltage protection relay 87E/87L/30a, (9-pin)
(series K1/1)
N49
Steering angle sensor
S9/1
Stop lamp switch (4MATIC/ASD)
X11/4
Test coupling for diagnosis, pulse readout (8-pin)
Electronics function
The electronics control the engagement and
disengagement of the four-wheel drive and
differential locks. They switch the solenoid valves in
the 4MATIC valve control unit (A7/2).
The electronics consist of the following components:
- Voltage supply
- Rear axle speed sensor (L6)
- Left and right front axle speed sensors (L6/1/2)
- Steering angle sensor (N49)
- Stop lamp switch (4MATIC/ASD) (S9/1)
- 4MATIC control unit (N30/3)
Voltage supply
The voltage supply for the electronics is via the
overvoltage protection relay (K1/2). It is in the right
of the components compartment.
K1/2 Overvoltage protection relay 87E/87L/30a (9-
pin) (series K1/1)
Battery voltage is continuously supplied to terminal
30. A 10 A fuse is installed between terminal 30 and
30a. The fault memory is continuously supplied with
voltage via terminal 30a. When the ignition is
switched on, the relays are controlled by electronics
via terminal 15. In this way the ABS (N30) and
4MATIC (N30/3) control units are supplied with
voltage via terminal 87E and additional equipment
via terminal 87L.
Overvoltage protection is achieved by means of a
22 volt Zener diode. Voltage peaks above 22 volts
which occur upstream of the overvoltage protection
are switched directly to ground by the Zener diode.
An overload is prevented by fuses. Terminals 87E
and 87L are fused separately.
Wheel speed sensors (L6, L6/1/2)
The wheel speed sensors (L6, L6/1/2) comprise a
magnet core and a coil. A toothed rotor moves in
the magnetic field of the wheel speed sensor. The
teeth of the rotor interrupt the magnetic field when
turning. Each tooth induces a voltage pulse in the
coil of the wheel speed sensor. The pulses are
transmitted to the 4MATIC control unit (N30/3)
which determines the speed from the number of
pulses.
Front axle wheel speed sensors (L6/1/2)
The front axle wheel speed sensors (L6/1/2) are
located in the steering knuckle. The rotor toothing
(43) is machined in the front axle drive shaft (44) in
the case of the 4MATIC.
43 Rotor
44 Front axle drive shaft
L6/1/2 Left/right front axle speed sensor
Rear axle wheel speed sensor (L6)
The rear axle speed sensor (L6) is located in the
rear axle casing (45). The rotor (43) is pressed on to
the bevel pinion (44).
Asuitable rotor with a different number of teeth is
required for each rear axle ratio. The mean speed of
both rear wheels is determined via the speed sensor
(L6) on the rear axle.
43
Rotor
44
Rear axle casing
L6
Rear axle speed sensor
Steering angle sensor(N49)
The steering angle sensor (N49) is located
beneath the steering wheel. It senses the steering
movements and transmits them to the 4MATIC
control unit (N30/3).
The magnets are embedded in a plastic slip ring
(a) on the underside of the impact absorber. The
two Hall-effect sensors (b) are offset. Thus
different signals arise between left and right
steering lock.
The steering angle sensor (N49) comprises 72
magnets (c) and two Hall-effect sensors (b). Hall-
effect sensors are semi-conductor elements
whose electrical characteristics are influenced by
magnetic fields.
The 4MATIC control unit (N30/3) compares the
input signals to specified values and engages the
four-wheel drive in the event of lateral skid.
45
Bevel pinion
N49
Steering angle sensor
b
Hall-effect sensor
a
Plastic slip ring
c
Magnets
Stop lamp switch (4MATIC/ASD) (S9/1)
The stop lamp switch (4MATIC/ASD) (S9/1) has an
additional contact (arrow) for the 4MATIC. The stop
lamp contact has one plug connection of 4 mm
Q
and an auxiliary contact of 2.5 mm
Q
.
When the service brake is operated, the stop lamp
contact is closed and the auxiliary contact is opened.
S9/1 Stop lamp switch (4MATIC/ASD)
When the service brake is operated, the 4MATIC
control unit (N30/3) receives a signal via a cable (d)
whereby the 4MATIC is switched off. The second
cable de-energizes the ABS control unit (N30).
The effect of the auxiliary contact is that when the
brake pedal is operated, the rear axle differential
lock valve (A7/2y3) is switched off in each case and
the rear axle lock releases even if there is a fault in
the stop lamp contact or 4MATIC control unit
(N30/3).
S9/1 Stop lamp switch (4MATIC/ASD)
X20 Intermediate plug connector, stop lamp switch (2-pin)
b
Stop lamp
c
Fuse box, fuse 5 (terminal 15)
d
4MATIC control unit (N30/3) and ABS control unit (N30)
e
Rear axle differential lock valve (A7/2y3)
4MATIC control unit (N30/3)
The 4MATIC control unit (N30/3) is located in the
right of the components compartment. It processes
all input signals and controls the solenoid valves
(A7/2y) in the 4MATIC valve control unit (A7/2).
The entire signal conditioning and processing is
performed digitally.
N30/3 4MATIC control unit
f
Overvoltage protection (terminal 87L)
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