Abstract: 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.

Abstract: A single sensor is located close to a ring gear on the periphery of which teeth are disposed equiangularly except at an angular reference position. When the ring gear rotates, the sensor generates output signals, with the period of the output pulse which corresponds to the reference position being larger than that of the other output pulses which correspond to the angular positions. A capacitor is charged during half of each the periods of the output pulses, so that the reference position can be discriminated by comparing the amplitude of the charged voltage or the discharging period of the capacitor with a predetermined value.

Abstract: This invention discloses a rotational position detecting apparatus for an internal combustion engine for detecting the rotational position of a crank shaft of the engine.

Abstract: The angle through which the crankshaft of an engine rotates within any given time is proportional to the rotational speed of the engine. Consequently, where the ignition system is of the type in which the integrated value of an integrator circuit or the count value of a counter circuit is varied so as to control the spark advance, if the rate of increase or decrease of the integrated value or the count value within a portion of the increasing or decreasing time is made different from that within the remaining portion of the time, the integrated value or the count value is directly affected by the engine rotational speed. In other words, the spark advance is directly controlled by the factor of the engine rotational speed, thus ensuring satisfactory response characteristic and accuracy for the ignition system.