Valvetronic Sensors

Valvetronic Sensors: Each eccentric shaft is monitored by a magneto-resistive position sensor. The N62 engine has two sensor assemblies, one for each eccentric shaft. These sensors are very durable for the environment (inside the cylinder head) and cope well with vibrations and high temperatures. The sensor assembly consists of:







- Measuring Sensor
- Evaluation Sensor
- communication Electronics

A magnetic wheel is mounted on the end of the eccentric shaft. The eccentric shaft sensor is mounted through the cylinder head cover at the back.

Both sensors monitor the eccentric shaft rotation angle of 180°. The Valvetronic control module supplies the sensors with 5 volts and ground.







The magneto-resistive element consists of a ferromagnetic layer. The resistance R is dependent on the angle (a) under the influence of a strong magnetic field. The magnetic field is generated by permanent magnets.

The resistance of the magneto-resistive element (1) in the sensor is dependent on the direction of the lines of the magnetic field (2) as influenced by the eccentric shaft magnetic wheel. The angle value signal of the measuring sensor is opposite to that of the evaluation sensor (opposing voltage values) during the rotation of the eccentric shaft. The Valvetronic control module constantly compares the values with each other.

The position data "message" is transmitted via a serial interface from the eccentric shaft sensors to the Valvetronic control module. Each of the two sensors requires three interfaces for data transfer:

- CS (chip select - measuring sensor or evaluation sensor)
- DAT (data transfer - of eccentric shaft position)
- CLK (clock line - signals the sensor requesting an update)

There is only one clock line, but it works inside the sensor assembly on both the measuring and evaluation sensor. The measuring sensor transmits the eccentric shaft positions to the Valvetronic control module at shorter intervals than the evaluation sensor.

Once the exact position of the eccentric shaft has been recorded by the magneto-resistive bridge circuit, this value is stored in an internal register. The Valvetronic control module sends the command to the measuring sensor via the CS line to transmit or upload the data from the internal register to the output register. The Valvetronic control unit then sends the command to the output register via the CLK line to transfer the data.

The data "message" from the measuring sensor is then issued on the DAT line, giving the exact position of the eccentric shaft (at a frequency of 250 kHz). The evaluation sensor works similarly but is only periodically checked for position (plausibility).