[ Pobierz całość w formacie PDF ]however, but by the separate hydraulic power steering assistance as with conventional
steering.
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E70 Lateral Dynamics Systems
Motor Position Sensor
The motor position sensor for the actuating unit is located at the rear of the AS actuating
unit electric motor and consists of a sensor chip (magneto resistive element) and a
magnet.
The motor position sensor in the actuating unit detects the rotor position of the electric
motor in accordance with the magneto resistive principle.
The sensor chip receives signals along the vertical and horizontal from the measurement
of the magnetic field direction. The sensor chip digitizes this angle information and
transfers this square-wave signal through the two-wire connection to the AS control unit,
on which the motor position sensor, in turn, receives its 7.5 V power supply. The motor
position sensor in the actuating unit has a measuring range of 180°.
The number of half turns is counted by the AS control unit and stored when the ignition
is switched off. The information about the rotor position is sent by the AS control unit via
a direct line as a pulse-width-modulated signal.
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E70 Lateral Dynamics Systems
Steering Column Switch Cluster
The SZL steering column switch cluster consists of the following components:
" SZL electronics
" Steering angle sensor
" Cruise control steering column switch
" Turn indicator steering column switch
" Wipers steering column switch
" Flat spring cassette.
The SZL can only be replaced as a complete unit. The flat spring cassette is attached to
the steering column switch cluster. The flat spring cassette can be removed and
replaced separately.
Index Explanation
1 Turn signal indicator switch
2 Cruise control switch
3 Code disc
4 Steering column switch cluster with optical sensor
5 Wiper switch
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E70 Lateral Dynamics Systems
SZL Electronics
The SZL electronics include a processor, a power supply and the following interfaces:
" F-CAN
" Optical switches
" Electrical switches
The optical sensor for measuring the steering angle is integrated into the control unit
circuit board.
Steering Angle Sensor
The steering angle sensor is designed as a contact-free, optical angle measurement
system. The system consists of a code disc and an optical sensor. The code disc is
directly connected to the steering wheel via a driver. If the steering wheel is moved, the
code disc turns within the optical sensor.
Code disc
Optical sensor
Code Disc
The code disc is black and has a pattern of lines. This pattern consists of two continu-
ous lines on the outside and inside of the code disc.
Between the two continuous lines, there are discontinuous lines at certain distances from
each other. These represent the digital range of the sensor. The digital code changes
every 2°.
The diagonal lines around the outside represent the analogue range of the sensor.
These lines allow a more precise measurement (0.1°) of the steering angle.
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E70 Lateral Dynamics Systems
Optical Sensor
The optical sensor is structured as follows:
Index Explanation Index Explanation
1 Light guide 5 Output: conversion into electrical signals
2 Code disc 6 Circuit board
3 Steering column 7 LED
4 Line camera
LED and Light Guide
The function of LED and light guide is to project light onto the code disc from above.
The light diode is soldered directly onto the SZL circuit board. The light guide is fixed to
the circuit board with two screws. The LED and light guide form the optical sensor
together with the line camera.
Line Camera
The line camera is fitted under the code
disc. The line camera converts optical
signals that penetrate the code disc into
electrical signals.
Index Explanation
1 Line camera
2 Light guide and LED
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E70 Lateral Dynamics Systems
Hydraulic Pump
Electronically Controlled Bypass Valve (EVV)
The EVV regulates the volumetric flow of hydraulic fluid in the hydraulic pump to ensure
that only the volumetric flow currently required to provide power assistance is made
available.
Example:
When the vehicle is being driven straight
ahead without power assistance, the circula-
tion pressure in the steering hydraulic circuit
drops, thus reducing the circulation pressure
and the power consumption. If a steering
movement is required, the volumetric flow is
immediately raised again and the usual steer-
ing-angle speed is ensured.
The EVV therefore controls the power
consumption of the hydraulic pump, thus
reducing the fuel consumption and the CO2
Index Explanation
emissions of the combustion engine.
1 Proportional valve (EVV)
Power Steering Hydraulic Circuit Diagram
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E70 Lateral Dynamics Systems
Legend for Power Steering Hydraulic Circuit Diagram
Index Explanation Index Explanation
1 Rack and pinion steering unit 5 Combustion engine
2 Steering valve 6 Electronically controlled bypass valve (EVV)
3 Flow regulating piston in the vane-cell pump 7 Throttle (restriction)
4 Vane-cell pump
Power Steering Cooler
The power steering cooler is located in the engine cooling module. The power
steering cooler consists of a continuous pipe with soldered rectangular fins.
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E70 Lateral Dynamics Systems
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