Apparatus for detecting both rotational speed and reference rotational angle of a rotary member

Claim 1

Apparatus for producing a signal indicative of a rotational speed of a rotary member and another signal indicative of a reference rotational angle of said rotary member, comprising: (a) a plurality of magnetized elements arranged circumferentially on said rotary member, said plurality of magnetized elements having normal-pitch elements and small-pitch elements which are arranged in a predetermined fashion or pattern given by 2 n ·K in units of said normal-pitch where n=1, 2, 3, . . . and K is a positive integer, the number of said small-pitch elements being at least three, and the distance between any two consecutive small-pitch elements being different from another; (b) a plurality of signal generating circuits arranged circumferentially on a stator to oppose said plurality of magnetized elements when said rotary member rotates, said plurality of signal generating circuits being connected in series to form a series circuit so as to develop a resultant voltage across two terminals of said series circuit with said signal generating circuits being caused by said magnetized elements to generate a voltage, said plurality of signal generating circuits having normal-pitch circuits and small-pitch circuits which are arranged in said predetermined fashion or pattern so that said normal-pitch magnetized elements face said normal-pitch circuits and said small-pitch magnetized elements face said small-pitch circuits respectively only once per rotation of said rotary member over a predetermined angle; (c) a first comparator responsive to said resultant voltage and to a first threshold voltage for producing said signal indicative of a rotational speed; and (d) a second comparator responsive to said resultant voltage and to a second threshold voltage, which is different from said first threshold voltage, for producing said other signal indicative of a reference rotational angle of said rotary member.