Steering Angle Sensor: Description and Operation

GF42.45-P-5107GZ Steering angle sensor, component description





The steering angle sensor (N49) is located in the steering column module (N80). It is fastened to the steering column module in connection with the clock spring contact/fanfare horns and airbag (A45).

The task of the steering angle sensor working on an optical basis is to record a steering angle specified by the driver and to pass on to the connected systems.

Component Identification:

The steering angle sensor consists of 2 microcomputers which together with a signal measuring ring form one unit. The 9 light-emitting diodes are located at equal distances in the signal measuring ring. They are located in a light barrier channel which is passed through by 8 blades of different length. The light barriers are located in the upper section of the clock spring contact/fanfare horns and airbag and only form the complete functional unit of the steering angle sensor by assembling (clipping in) both components.

Function of steering angle sensor
In the center position of the steering wheel the 8 blades assumes a defined position relative to the 9 light-emitting diodes. This center position is recorded by the computer in the steering angle sensor.

When the steering wheel is turned, the position of the blades changes with respect to the light-emitting diodes (light/dark). Because of the different lengths of the blades and the different intervals between them, a defined signal pattern is produced for computing the current steering wheel position.

The signal patterns are used to calculate angle values which are converted into serial data for the connected control units.

The signals are recorded by light-emitting diodes and light barriers in 2.5 degrees steps. The signal recording is designed for a steering angle of ± 720 degrees (4 steering wheel rotations from stop to stop).

So that the steering angle is also recorded after "ignition OFF", voltage is supplied via circuit 30. The steering angle sensor must be re-initialized after a voltage interruption (circuit 30). This is done by turning the steering wheel from lock to lock.