Patent ID: 6999006
Filing Date: 2006-02-14
Classification: G01D

Abstract:
1. A rotation position detecting device comprising: means for generating an angular signal having pulses the cycle period of which is even when a rotating object rotates at a constant rotation speed and a non-pulse portion which corresponds to a reference position; a clock pulse generating circuit which generates pulses at equal intervals; an up-down command circuit for generating an up-down command signal the frequency of which is divided to a half of the frequency of the angular signal; a first counter for counting up the clock signal when the up-down command signal changes from a first level to a second level to reset and subsequently counting down the clock signal when the up-down command signal changes from the second level to the first level; a second counter for counting up the clock signal when the up-down command signal changes from the second level to the first level to reset and subsequently counting down the clock signal when the up-down command signal changes from the first level to the second level; a first processing circuit for providing a first reference value that is provided by subtracting a product of the counted value of the first counter when the up-down command signal changes from the second level to the first level and a constant that corresponds to the non-pulse portion from a counted value counted by the first counter; a second processing circuit for providing a second reference value that is provided by subtracting a product of the counted value of the second counter when the up-down command signal changes from the first level to the second level and the constant from a counted value counted by the second counter; a first comparator for generating a detection signal when the counted number of the first counter becomes smaller than the first reference value; and a second comparator for generating a detection signal when the counted number of the second counter becomes smaller than the second reference value.