Patent ID: 6291815
Filing Date: 2001-09-18
Classification: G01D

Abstract:
A device for measuring a rotation angle of a rotary element, comprising:first, second and third detection means;rotary means rotatable about a central axis thereof in accordance with a rotation of the rotary element, the rotary means having first and second circular arrays of signaling means arranged coaxially around the central axis thereof, the first array of signaling means being adapted to be detectable by the first detection means so as to generate a first signal alternating between ""on"" and ""off"" each time the rotary means rotates five times of a unit angle, the second array of signaling means being adapted to be detectable by the second and third detection means so as to generate second and third signals, respectively, the second and third signals each alternating between either ""on"" and ""off"" or ""off"" and ""on"" each time when the rotary means rotates alternatively two times and three times of the unit angle, the ""on"" and ""off"" alternations of the first, second and third signals being shifted from one another by an integer times of the unit angle;means for increasing a measurement value of the rotation angle of the rotary element by the unit angle each time when one of the ""on"" and ""off"" alternations of the first, second and third signals successively occurs in a first order with regard to the first, second and third signals corresponding to a rotation of the rotary element in a first rotational direction, while decreasing the measurement value by the unit angle each time when one of the ""on"" and ""off"" alternations of the first, second and third signals successively occurs in a second order with regard to the first, second and third signals corresponding to a rotation of the rotary element in a second rotational direction opposite to the first rotary direction so as to provide the measurement value with a positive/negative sign indicative of the rotational direction; andmeans for checking each occurrence of the ""on"" and ""off"" alternations of the first, second and third signals with respect to at least one of the first and second orders in each set of five consecutive occurrences of the ""on"" and ""off"" alternations, so as to detect an error in the order, when occurred.