Patent ID: 8558539
Filing Date: 2013-10-15
Classification: G01D

Abstract:
1. A stroke amount detecting device for detecting an amount of stroke of a detection object that moves straight, comprising: a first magnetic field generation member; a second magnetic field generation member opposed to the first magnetic field generation member with respect to a direction perpendicular to a stroke direction of the detection object, the first magnetic field generation member and the second magnetic field generation member magnetized such that opposing magnetic poles have a same magnetic polarity; a third magnetic field generation member disposed apart from the first magnetic field generation member by a predetermined distance across a space with respect to the stroke direction, the third magnetic field generation member magnetized in a same direction as the first magnetic field generation member with respect to the direction perpendicular to the stroke direction; a fourth magnetic field generation member disposed apart from the second magnetic field generation member by a predetermined distance across a space with respect to the stroke direction, and opposed to the third magnetic field generation member with respect to the direction perpendicular to the stroke direction, the fourth magnetic field generation member magnetized in a same direction as the second magnetic field generation member with respect to the direction perpendicular to the stroke direction; and a magnetic sensor unit disposed in an area between the first magnetic field generation member or the third magnetic field generation member and the second magnetic field generation member or the fourth magnetic field generation member with respect to the direction perpendicular to the stroke direction, the magnetic sensor unit moving relative to the first to fourth magnetic field generation members along a straight traveling axis in accordance with a stroke motion of the detection object, the magnetic sensor unit including a magnetosensitive surface facing in the stroke direction to detect an amount of stroke of the detection object; wherein the magnetic sensor unit includes a first magnetic sensor element outputting a signal according to a change in a magnetic field caused as traveling relative to the first magnetic field generation member, the second magnetic field generation member, the third magnetic field generation member and the fourth magnetic field generation member; and the magnetic sensor unit further includes a linearity correction element that corrects a magnetic flux density detected by the first magnetic sensor element so that the magnetic flux density detected by the first magnetic sensor element varies linearly relative to an amount of stroke of the detection object.