Position detection apparatus and vehicle mirror angle detection apparatus

Abstract

To provide a position detection apparatus with an expanded range of good linearity in a magnetic sensor's output characteristic with respect to position of a movable body as well as to provide a vehicle mirror angle detection apparatus using the position detection apparatus. Two permanent magnets 42 and 44 and one Hall-effect sensor 46 are used. The permanent magnets 42 and 44 are arranged with their relative position fixed. The Hall-effect sensor 46 is placed laterally to the arrangement of the two permanent magnets 42 and 44. The permanent magnets 42 and 44 and Hall-effect sensor 46 move relative to each other in a direction parallel to the arranging direction of the permanent magnets 42 and 44. Those surfaces 42a and 44a of the permanent magnets 42 and 44 which face the Hall-effect sensor 46 constitute magnetic pole faces of opposite polarity and the magnetic pole faces 42a and 44a are placed with an inward tilt. A magnetic sensing direction F of the Hall-effect sensor 46 is set orthogonally to the arranging direction of the permanent magnets 42 and 44.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an embodiment of a position detection apparatus according to the present invention;

FIG. 2 is a sectional view showing part of an internal structure of a vehicle mirror equipped with a conventional mirror angle detection apparatus;

FIG. 3 is a perspective view showing another arrangement of permanent magnets and magnetic sensor in a conventional vehicle mirror angle detection apparatus;

FIG. 4 is a diagram showing a relationship between mirror angle and Hall voltage in a vehicle mirror angle detection apparatus to illustrate how differences in linearity result in errors in detected angles;

FIG. 5 is a magnetic line distribution chart according to the arrangement in FIG. 1;

FIG. 6 is a diagram showing a characteristic of magnetic flux density in a magnetic sensing direction F of a Hall-effect sensor 46 with respect to position of a movable body 48 in a moving direction E, where the characteristic depends on distance (in a direction orthogonal to the moving direction E) between the Hall-effect sensor 46 and permanent magnets 42 and 44;

FIG. 7 is a diagram showing a relationship of output voltage of the Hall-effect sensor 46 to the position of the movable body 48 in the moving direction E when the angle θ′ in FIG. 5 is set at 45°;

FIG. 8 is a diagram showing a relationship of output voltage of the Hall-effect sensor 46 to the position of the movable body 48 in the moving direction E when the angle θ′ in FIG. 5 is set at 15°;

FIG. 9 is a diagram showing a relationship of output voltage of the Hall-effect sensor 46 to the position of the movable body 48 in the moving direction E when the angle θ′ in FIG. 5 is set at 10°;

FIG. 10 is a diagram showing a relationship of output voltage of the Hall-effect sensor 46 to the position of the movable body 48 in the moving direction E when the angle θ′ in FIG. 5 is set at 0°;

FIG. 11 is a partially exploded perspective view showing an embodiment of a vehicle mirror drive unit equipped with the vehicle mirror angle detection apparatus according to the present invention;

FIG. 12 is an exploded perspective view of a subassembly 59 in the vehicle mirror drive unit 52 in FIG. 11;

FIG. 13 is a sectional view showing part of an internal structure of a vehicle mirror equipped with the vehicle mirror drive unit 52 in FIG. 11 and showing an arrangement of a slide block 96 (98) and Hall-effect sensor 115 (117);

FIG. 14 is a sectional view showing a mirror surface tilted to a maximum angle in one direction from the position shown in FIG. 13; and

FIG. 15 is a sectional view showing the mirror surface tilted to a maximum angle in another direction from the position shown in FIG. 13.

Claims

1. A position detection apparatus, comprising: two permanent magnets and one magnetic sensor,wherein the two permanent magnets are arranged with their relative position fixed;the magnetic sensor is placed laterally to the arrangement of the two permanent magnets;the two permanent magnets and the magnetic sensor move relative to each other in a direction parallel to an arranging direction of the two permanent magnets;those surfaces of the two permanent magnets which face the magnetic sensor constitute magnetic pole faces of opposite polarity and the magnetic pole faces are placed with an inward tilt;a magnetic sensing direction of the magnetic sensor is set orthogonally to the arranging direction of the two permanent magnets; andthe magnetic sensor produces an output corresponding to relative position between the two permanent magnets and the magnetic sensor in the direction of the relative movement.

2. The position detection apparatus according to claim 1, wherein the tilt angle of the magnetic pole faces of the two permanent magnets placed with an inward tilt is larger than 10° and smaller than 80° with respect to the arranging direction of the two permanent magnets.

3. The position detection apparatus according to claim 1, wherein when the two permanent magnets are located at equal distances from the magnetic sensor, the angle formed by a straight line connecting a sensing point of the magnetic sensor and the midpoint of a straight line joining the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor with each of straight lines connecting the sensing point of the magnetic sensor and the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor is set at 45°±5°.

4. The position detection apparatus according to claim 1, wherein distance between the center points of the magnetic pole faces of the two permanent magnets is set such that stroke length of the relative movement between the two permanent magnets and the magnetic sensor will be 80% or less of distance between the center points of the magnetic pole faces of the two permanent magnets.

5. The position detection apparatus according to claim 1, wherein on a plane in which the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor and the sensing point of the magnetic sensor are located, length of the magnetic pole faces of the two permanent magnets is set to equal to or larger than ⅓ of the stroke length of the relative movement but not so large that the two permanent magnets will touch each other.

6. A vehicle mirror angle detection apparatus, comprising: a mirror body which is tiltably supported in a mirror housing and whose mirror angle is adjusted by a motor-driven tilting operation;a slide member which has one end pivotably supported at a position off the center point of the tilting operation on the back of the mirror body and moves linearly in a direction orthogonal to a surface of the mirror body along with the tilting operation of the mirror body;two permanent magnets mounted on the slide member, being arranged along the direction of linear movement; anda magnetic sensor attached to a fixed part in the mirror housing,wherein the two permanent magnets and the magnetic sensor are arranged in the same manner as in the position detection apparatus according to claim 1, andthe magnetic sensor produces an output corresponding to the mirror angle of the mirror body.

7. A vehicle mirror angle detection apparatus according to claim 6, wherein the tilt angle of the magnetic pole faces of the two permanent magnets placed with an inward tilt is larger than 10° and smaller than 80° with respect to the arranging direction of the two permanent magnets.

8. A vehicle mirror angle detection apparatus according to claim 6, wherein when the two permanent magnets are located at equal distances from the magnetic sensor, the angle formed by a straight line connecting a sensing point of the magnetic sensor and the midpoint of a straight line joining the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor with each of straight lines connecting the sensing point of the magnetic sensor and the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor is set at 45°±5°.

9. A vehicle mirror angle detection apparatus according to claim 6, wherein distance between the center points of the magnetic pole faces of the two permanent magnets is set such that stroke length of the relative movement between the two permanent magnets and the magnetic sensor will be 80% or less of distance between the center points of the magnetic pole faces of the two permanent magnets.

10. A vehicle mirror angle detection apparatus according to claim 6, wherein on a plane in which the center points of the magnetic pole faces on those sides of the two permanent magnets which face the magnetic sensor and the sensing point of the magnetic sensor are located, length of the magnetic pole faces of the two permanent magnets is set to equal to or larger than ⅓ of the stroke length of the relative movement but not so large that the two permanent magnets will touch each other.