Crankshaft Position Sensor: Description and Operation

Fig. 35 E.C.C.S. Distributor Components.:

The crank angle sensor detects engine r.p.m. and crank angle (piston position). It sends a signal to the control unit to control various operations. This Sensor is built into the distributor Fig. 35.

SIGNAL ROTOR PLATE
The signal rotor plate has 360 slits at 1° intervals on its periphery (circle). It also has four slits at 90° intervals.
These four slits are used to detect the crank angle (T.D.C.). The 360 teeth are used to provide the 1° signal that is necessary to control engine r.p.m. and ignition timing.

Fig. 34 E.C.C.S. Distributor Components.:

The crank angle sensor has two diodes and a wave forming circuit. When a signal rotor passes through the space between the Light Emitting Diode (L.E.D.) and Photo Diode, the slit of the signal rotor plate alternately cuts the light which is sent to the photo diode from the L.E.D. Fig. 34.

Fig. 36 Crank Angle Sensor Signal To C.E.C.U.:

This causes a alternating voltage and is then converted into an on-off pulse by the wave forming circuit, which is sent to the control unit Fig. 36.

Fig. 37 180 Signal Pick-up:

DETECTING RPM AND IGNITION TIMING
Diodes 1 and 3 in Fig. 37 are used to detect the 1° signal which is created by the 360 slits on the rotor plate. When a slit reaches the space between the L.E.D. and photo diode, the photo diode receives the light from the L.E.D. and this causes an alternating voltage so each wave from each diode is compounded.

Fig. 38 Crank Angle Sensor Signal To C.E.C.U.:

The compound wave is converted into an on-off pulse. This 1° on-off signal is sent to the control unit.

Fig. 37 180 Signal Pick-up:

DETECTING PISTON T.D.C.
Diode 2 in Fig. 37 is used to detect the 180° signal which is created by the 90° slits on the rotor plate. When a slit reaches the space between the L.E.D. and the photo diode, the photo diode catches the light from the L.E.D. and this causes an alternative voltage. At this time, a signal on-off pulse is generated. Since engine r.p.m. is twice that of the distributor, the rotor plate has four slits at 90° intervals.