Rpm sensor

RPM SENSOR

The sensor for detecting the rpm is of the inductive type which operates through the change of a magnetic field generated by the passage of the teeth of a toothed pulley (phonic wheel) fitted on the flywheel. The teeth which pass in front of the magnetic field generator change the gap between the pulley and the sensor; therefore, the dispersed flux, which consequently varies, induces an alternate sinusoidal voltage in the coils of the sensor, the amplitude of which depends on the peripheral speed of the phonic wheel, the gap between the tooth and the sensor, the shape of the teeth, the magnetic characteristics of the sensor and on the support system.

The output signal which varies in relation to the rpm is processed by the control unit to obtain a signal at each passage through zero and a constant rectangular oscillation of amplitude to enable the control of the digital circuits inside the control unit.

The interval between the start of one tooth and another is 6° with the exception of the reference mark which is made by eliminating two of the 60 teeth of the pulley. The hollow due to the lack of two teeth gives the control unit a reference point of the crankshaft and each subsequent tooth of the phonic wheel informs the control unit of an increase in its angular position.

1. Soft iron core
2. Winding
3. Permanent magnet

REMOVAL/REFITTING

1. Disconnect the connection of the timing sensor.

1. Slacken the fastening screw and remove the sensor.

8 ÷ 10 Nm
0.8 ÷ 1.0 kgm

CHECKING THE AIR GAP

• Remove the rpm sensor (see specific procedure).

1. Using tool N° 1.820.079.000 (A.2.0449), measure dimension "A".

1. Using a gauge measure dimension "A".

1. With a dial gauge check the value of "B" on the sensor.

• Calculate the rpm sensor gap and check that it is within the specified limits.

A - B = 0.7 ± 0.1 mm