Rotational position detector having initial setting function

Apparatus for detecting a rotational position of a rotor, comprising:

• a rotor having a tooth to be detected;
• pick-up means, disposed in a vicinity of said rotor, for generating a rotation detection signal which indicates a proximity of a rotational position of said tooth with respect to said pick-up means;
• change-over timing detecting means for detecting timing for said tooth to rotate between a first state in which said tooth is proximate to said pick-up means and a second state in which said tooth is not proximate to said pick-up means, on a basis of a variation of said rotation detection signal;
• pulse signal outputting means for outputting a pulse signal which changes cyclically between a first level corresponding to said first state and a second level corresponding to said second state in accordance with a detection result of said change-over timing detecting means;
• rotational position detecting means for detecting a rotational position of said rotor in accordance with said pulse signal;
• compulsory setting means for compulsorily setting said pulse signal to an initial value of a predetermined one of said first level and said second level when said rotor starts to rotate from a stationary state;
• determining means for determining whether or not said initial value of said pulse signal set compulsorily has been inverted in response to a first change-over timing detection made by said change-over timing detecting means;
• artificial change-over signal outputting means for outputting an artificial change-over signal artificially representing a change-over timing to said rotational position detecting means in response to said first change-over timing detection when said determining means determines that said initial value of said pulse signal set compulsorily has not been inverted;
• and
• means for converting said rotation detection signal into a digital output signal;
• said change-over timing detecting means comprising:
• a reference value rewriting decision and latch circuit for generating a reference value signal by providing non-linear hysteresis characteristics having a predetermined hysteresis width to a value represented by said digital output signal,
• a difference detecting circuit for obtaining a difference signal between said reference value signal and said digital output signal which are input to said difference detecting circuit, said difference signal having a most significant bit for which "1" or "0" is set depending on whether or not said difference signal is larger than 0,
• a hysteresis arithmetic circuit for obtaining a hysteresis signal given by subtracting said hysteresis width from an absolute value of said difference signal, said hysteresis signal having a most significant bit for which "1" or "0" is set depending on whether or not said hysteresis signal is larger than 0, and for outputting the most significant bit of said hysteresis signal, and
• an output latch circuit for outputting a binary output signal, an initial value of said output latch circuit being fixed to a predetermined one of "1" or "0" in accordance with said most significant bit of said hysteresis signal and said most significant bit of said difference signal, said binary output signal being determined by a rotational phase of said rotor after at least a half rotation thereof.

Apparatus for detecting a rotational position of a rotor, comprising:

• a rotor having a protruding tooth;
• pick-up means, disposed in a vicinity of said rotor, for generating a rotation detection signal which indicates a rotational position of said tooth with respect to a proximity of said tooth to said pick-up means;
• change-over timing detecting means for detecting timing for said tooth to rotate between a first state in which said tooth is proximate to said pick-up means and a second state in which said tooth is not proximate to said pick-up means, on a basis of a variation of said rotation detection signal;
• pulse signal outputting means for outputting a pulse signal which changes cyclically between a first level corresponding to said first state and a second level corresponding to said second state in accordance with a detection result of said change-over timing detecting means;
• compulsory setting means for compulsorily setting said pulse signal to an initial value of one of said first level and said second level when said rotor starts to rotate from a stationary state in contravention to said actual rotational position of said rotor.