Stroke amount detecting device

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 chance 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 second magnetic sensor element that is spaced from the first magnetic sensor element by a predetermined distance in a direction parallel to the straight traveling axis, and has a magnetic property identical to that of the first magnetic sensor element;
• and
• a calculation element that calculates the amount of stroke of the detection object by a trigonometric function operation based on output signals from the first magnetic sensor element and the second magnetic sensor element.

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 second magnetic field generation member and the first magnetic field generation member magnetized such that opposing magnetic poles have a same magnetic polarity;
• a magnetic sensor unit disposed in an area between the first magnetic field generation member and the second magnetic field generation member with respect to the direction perpendicular to the stroke direction, and moving along a straight traveling axis relative to the first magnetic field generation member and the second magnetic field generation member 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;
• and
• a magnetic flux transmission member made of a magnetic material and including a first wall and a second wall, wherein
• the first wall and the second wall are disposed on opposite sides of the straight traveling axis,
• the first magnetic field generation member is disposed along an inner surface of the first wall,
• the second magnetic field generation member is disposed along an inner surface of the second wall,
• an intersection point of the straight traveling axis with a line, which passes through a center of the first wall with respect to the stroke direction and a center of the second wall with respect to the stroke direction and is perpendicular to the straight traveling axis, is referred to as a zero point of an amount of stroke,
• a stroke range of the detection object is biased toward a negative side of the stroke direction from the zero point of the amount of stroke,
• the first magnetic field generation member and the second magnetic field generation member are offset from the zero point of the amount of stroke to the negative side of the stroke direction,
• 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 and the second 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.

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 second magnetic field generation member and the first magnetic field generation member magnetized such that opposing magnetic soles have a same magnetic polarity;
• a magnetic sensor unit disposed in an area between the first magnetic field generation member and the second magnetic field generation member with respect to the direction perpendicular to the stroke direction, and moving along a straight traveling axis relative to the first magnetic field generation member and the second magnetic field generation member 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;
• and
• a magnetic flux transmission member made of a magnetic material and including a first wall and a second wall, wherein
• the first wall and the second wall are disposed on opposite sides of the straight traveling axis,
• the first magnetic field generation member is disposed along an inner surface of the first wall,
• the second magnetic field generation member is disposed along an inner surface of the second wall,
• an intersection point of the straight traveling axis with a line, which passes through a center of the first wall with respect to the stroke direction and a center of the second wall with respect to the stroke direction and is perpendicular to the straight traveling axis, is referred to as a zero point of an amount of stroke,
• a stroke range of the detection object is biased toward a negative side of the stroke direction from the zero point of the amount of stroke,
• the first magnetic field generation member and the second magnetic field generation member are offset from the zero point of the amount of stroke to the negative side of the stroke direction,
• 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 and the second magnetic field generation member, and
• the magnetic sensor unit further includes:
• a second magnetic sensor element that is spaced from the first magnetic sensor element by a predetermined distance in a direction parallel to the straight traveling axis, and has a magnetic property identical to that of the first magnetic sensor element;
• and
• a calculation element that calculates an amount of stroke of the detection object by a trigonometric function operation based on output signals from the first magnetic sensor element and the second magnetic sensor element.

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 second magnetic field generation member and the first magnetic field generation member magnetized such that opposing magnetic poles have a same magnetic polarity;
• and
• a magnetic sensor unit disposed in an area between the first magnetic field generation member and the second magnetic field generation member with respect to the direction perpendicular to the stroke direction, and moving along a straight traveling axis relative to the first magnetic field generation member and the second magnetic field generation member 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 first magnetic field generation member and the second magnetic field generation member have an identical shape and an identical magnetic property,
• each of the first magnetic field generation member and the second magnetic field generation member is constructed of a magnet group including a plurality of magnets,
• the plurality of magnets in each magnet group are disposed such that magnetic poles having a same magnetic polarity are adjacent to each other,
• 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 and the second 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.