Transmission Speed Sensor, Component Description - GF27.19-D-5151H
TRANSMISSION 722.6 in MODEL 906.111/113/131/133/135/153/155/211/213/231/233/235/253/255/611/613/631/633/635/637/653/655/657/711/713/731/733/735 with CODE (J19) Automatic 1 day/2 driver tachograph (EC)
Location
The speed sensor is located at the rear right of the transmission housing.
Task
The speed sensor detects the rotational speed of the output shaft and passes this value on to the instrument cluster (A1) and to the tachograph (A56). The serial number is transmitted to the tachograph at the same time.
Setup, schematic representation
The speed sensor consists of the Hall sensor and the electronic analysis system. The Hall sensor is designed as follows:
- Magnet holder
- Solenoid
- Capacitors
- Flexible printed circuit board
- Hall IC
The electronic analysis system is mounted on the flexible printed circuit board. The electronic analysis system has the following layout:
- Signal preparation
- Microprocessor with peripherals
- Driver (digital signal)
- Signal driver (analog signal)
- Power supply unit with voltage monitoring
Function, schematic representation
Function
The speed sensor is supplied with power from the power supply unit of the tachograph via the power supply unit with voltage monitoring of the speed sensor. This causes a magnetic field to be formed around the magnets integrated in the Hall sensor. The segment gear on the output shaft passes through the magnetic field and in doing so alters it. A voltage signal in the millivolt (mV) range is generated in the Hall sensor. The Hall IC integrated in the Hall sensor converts this voltage signal into a square wave signal. This square wave signal is amplified by the signal preparation module of the speed sensor and is passed on to the microprocessor with peripherals as well as to the signal driver (analog signal) of the speed sensor. The amplified square wave signal is sent as an analog signal from the signal driver (analog signal) of the speed sensor to the signal preparation module of the tachograph.
At the same time, the amplified square wave signal is coded and digitized by the microprocessor with peripherals of the speed sensor. The coded and digitized signals are sent via the driver (coded, digital signals) of the speed sensor to the driver (coded, digital signals) of the tachograph.
An analog signal and coded, digital signals are sent so that the tachograph can check the authenticity of the speed signal from the speed sensor by means of a causality check, thus making it impossible to manipulate the vehicle speed signal. Following this causality check, the signals are made available for the tachograph functions by the microprocessor with peripherals of the tachograph. In addition, the tachograph sends commands and data to the speed sensor.