Patent ID: 7893688
Filing Date: 2011-02-22
Classification: G01D

Abstract:
1. A position sensor comprising: a longitudinally extending permanent magnet member having opposite ends polarized to have opposite magnetic poles, each of the opposite ends being configured to surround a common inside space, at least two longitudinally extending arc-shaped projecting magnetic elements respectively projecting from the opposite ends toward the inside space to confront each other at a distance, thereby providing in the inside space a magnetic field whose magnetic flux density becomes a maximum at a longitudinal center of the inside space and gradually becomes smaller as a position of the inside space shifts from the longitudinal center along a longitudinal axis of the permanent magnet members; a pair of compatible main magnetic sensors disposed in the inside space along the longitudinal axis at an interval so as to generate a pair of output signals when the permanent magnet member shifts along the longitudinal axis, wherein: the arc-shaped projecting elements are arranged so that each of the output signals can be expressed by a cosine of a shift value from the longitudinal center; and the interval is ¼ of the cycle of the cosine.