A device for controlling ignition or fuel injection and the like of an internal combustion engine includes an angular position sensor of a shaft of the engine. The sensor is in the form of a disc rotating together with the shaft and being provided on its periphery with as many radially projecting segments separated by gaps as many cylinders has the engine. A gap between the segments is provided with a single sloping ramp terminating with a steep flank. The flank of one segment and the steep flank of the ramp cooperate with a detector which generates a marking pulse coordinating during single rotation of the shaft the distribution of control pulses to respective cylinders.

A rotational position detecting apparatus includes a rotating member magnetized to induce a large number of magnetic poles on the periphery thereof except at a portion indicative of a rotational reference position, and a pair of magnetically sensitive elements for detecting the magnetic flux from the magnetic poles so as to generate rotational angle signals and reference position signals. The pair of magnetically sensitive elements are positioned side by side such that their output signals generated in response to the magnetic flux from the magnetic poles are different in phase by half the period, and the difference between the outputs of the magnetically sensitive elements is obtained by a differential circuit whose output has an amplitude which is two times the amplitude of the outputs of the magnetically sensitive elements. The magnetic poles on the periphery of the rotating member are dropped out at the reference position in such a manner that the output AC component of the respective magnetically sensitive elements is dropped out at the reference position in a point symmetrical manner on both sides of the zero level of the AC component, thus stably supplying the rotational angle signals and the reference position signals.

A Hall Effect device is provided for use as a rotary position sensor in cooperation with a shaped magnet that imposes a magnetic field on the Hall Effect device which is generally linear and proportional to the angular position of the shaped magnet. Two alternative embodiments are described and illustrated which both provide a high degree of linearity between the electrical output of the Hall device and the rotational position of the shaped magnet. One of the alternative embodiments is generally oblong and the other alternative embodiment is generally bell shaped. Both of these alternative embodiments exhibit a high degree of linearity between the strength of the magnetic field imposed on a Hall Effect element and the rotational, or angular, position of the shaped magnet.

In an angle-based binary encoded crankshaft position sensing system, a target wheel is coupled to a crankshaft and a single VR sensor is juxtaposed with the target wheel for sensing the angular position of the wheel and, hence, the angular position of the crankshaft. To permit the use of a single VR sensor in conjunction with an angle-based binary encoded system, the periphery of the target wheel is formed with teeth and slots defining a binary pattern. The slots are wider than the teeth, and the depth of the slots relative to the portion of the periphery defining a nominal radius is greater than the height of the teeth relative to the nominal periphery. With this structure, the signal generated by the sensor in response to a slot advantageously is symmetric to the signal generated by the sensor in response to a tooth.

The invention relates to monitoring techniques, such as angular movement monitoring techniques, in which an element with at least one peripheral irregularity is moved relative to a magnetic circuit so as to induce a variation in the reluctance in the magnetic circuit which can be detected externally. A device is disclosed including two magnetic elements defining respective magnetic circuits symmetrical with each other. Between the two magnetic members a gap is formed of approximately the same size of a peripheral irregularity, consisting of a notch or a tooth of a moving member, which is passed in front of the two magnetic circuits to cause a corresponding variation in reluctance in the magnetic circuits which produce a disturbance in the characteristics of symmetry, detectable by a sensor preferably a Wiegand-effect sensor.