JPH0599949A - Rotation detecting apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] Increasing sensitivity in a rotation detection device [Construction] 1 is a substrate on which a magnetoresistive element is mounted, 2 and 3 are magnetoresistive elements, 4 is a point through which a rotation axis of a rotating body passes, 5 , 7 indicates the magnetic sensitive direction, and 6 and 8 indicate the direction of the center line of the magnetoresistive element. 2 shows a magnetoresistive element in which the magnetic sensitivity direction is deviated from the center line direction in the second magnetoresistive element. The angle 9 formed by the magneto-sensitive directions of the two magnetoresistive elements is 135 °, but the angle 10 formed by the center line direction is larger than 135 °. Further, depending on the outer shape of the magnetoresistive element, the angle formed by the magnetically sensitive directions of the two magnetoresistive elements may be 45 °. [Effect] In the rotation detecting device due to a weak magnetic field, distortion of the output of the magnetoresistive element can be eliminated and a sufficient output can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rotation detecting device.

[0002]

2. Description of the Related Art Conventionally, a normal rotation and a reverse rotation are detected which are composed of a rotating body in which two permanent magnets are symmetrically arranged about a rotation axis on a disk and two magnetoresistive elements for detecting the rotation of the rotating body. In the rotation detection device, the two magnetoresistive elements (outer shape)
The angle formed by is set to 135 ° in order to detect forward rotation and reverse rotation. FIG. 2 shows the arrangement of a conventional magnetoresistive element. The angle 10 formed by the center line directions of the two magnetoresistive elements is 135 °, but the angle 9 formed by the magnetically sensitive directions is smaller than 135 °.

[0003]

As described in "Prior Art", the angle formed by two magnetoresistive elements is determined by the outer shapes of the two magnetoresistive elements. Ideally, the magnetic sensitive direction is the same as the center line of the external shape, but the magnetic sensitive direction may deviate from the center line direction during the process of forming the element, so the magnetic resistance in the detection in a weak magnetic field In some cases, the output of the device was distorted and a sufficient output could not be obtained.

[0004]

The present invention is to solve the above-mentioned problems, and senses the rotation of a rotor having two permanent magnets symmetrically arranged about a rotation axis on a disk. In a rotation detecting device for detecting forward rotation and reverse rotation composed of two magnetoresistive elements, the angle formed by the magneto-sensitive directions of the two magnetoresistive elements is 135 °.

[0005]

There are three possible methods for increasing the sensitivity of the rotation detecting device. 1. Increase the magnetic field strength of the permanent magnet. 2. Reduce the distance between the magnetoresistive element and the rotating body. 3.
Increase the sensitivity of the magnetoresistive element. Item 1 cannot be strengthened to some extent when the influence must be taken into account for external factors (eg, the global field). The method of item 2 is restricted by the outer shape and cannot be approached to a certain extent. That is, in order to increase the detection sensitivity (sensitivity is limited in a low-power-consumption magnetoresistive element), the output waveform output from the magnetoresistive element must be closer to a sine wave. As described in the “Problem”, the magnetic sensitive direction ideally points in the same direction as the center line of the outer shape, but the magnetic sensitive direction may shift from the center line direction in the process of forming the element. In the detection with a weak magnetic field, the output of the magnetoresistive element may be distorted and a sufficient output may not be obtained.

[0006]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a plan view of the magnetoresistive element substrate viewed from the direction of the rotating body.
In FIG. 1, 1 is a substrate on which a magnetoresistive element is mounted, 2 and 3 are magnetoresistive elements, 4 is a point through which a rotation axis of a rotating body passes, 5 and 7 are magnetic sensitive directions, and 6 and 8 are centerline directions of the magnetoresistive elements. Are shown respectively. In the case of this example, in the magnetoresistive element of 2, the magnetoresistive element is deviated from the center line direction and the magnetic sensitive direction.

In this example, the angle 9 formed by the magneto-sensitive directions of the two magnetoresistive elements is 135 °, but the angle 10 formed by the center line direction is larger than 135 °. In this example, it is assumed that one of the magnetoresistive elements has the center line direction and the magnetic sensitivity direction coincide with each other. Actually, however, such an example is rare, and both the center line direction and the magnetic sensitive direction often do not match.

Further, in this embodiment, the angle formed by the magneto-sensitive directions of the two magneto-resistive elements is 135 °, but the angle formed by the magneto-sensitive directions of the two magneto-resistive elements is 45 ° depending on the outer shape of the magneto-resistive elements. If the magnetoresistive element can be brought closer to the rotation axis (the horizontal magnetic field strength is strong on the rotation axis), the angle formed by the magneto-sensitive directions of the two magnetoresistive elements should be 45 ° instead of 135 °. Is also necessary. Further, although the outer shape of the magnetoresistive element is shown as a rectangle in this embodiment, various shapes can be considered for the outer shape of the magnetoresistive element. Therefore, according to the present invention, the magnetoresistive elements are arranged at an angle formed by the magnetic sensitive directions. You can decide

[0009]

As described above, according to the present invention, it is possible to eliminate the distortion of the output of the magnetoresistive element in the rotation detecting device due to the weak magnetic field and to secure a sufficient output.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional example.

FIG. 3 is a diagram showing a configuration of the present invention.

[Explanation of symbols]

 1. A substrate on which the magnetoresistive element is arranged. Magnetoresistive element 3. Magnetoresistive element 4. 4. Points through which the rotation axis passes Center line of magnetoresistive element 6. Center line of magnetoresistive element 7. Magnetosensitive direction of magnetoresistive element 8. Magneto-sensitive direction of magneto-resistive element 9. Angle formed by magneto-sensitive directions of two magneto-resistive elements 10.2 Angle formed by center lines of two magneto-resistive elements 101. Rotating body 102. Permanent magnet 103. permanent magnet

Claims (1)

[Claims] 1. A rotation for detecting forward and reverse rotations, which comprises a rotating body in which two permanent magnets are symmetrically arranged about a rotation axis on a disk, and two magnetoresistive elements for sensing the rotation of the rotating body. In the detection device, the angle formed by the magneto-sensitive directions of the two magneto-resistive elements (the direction of the magnetic field where the output of the magneto-resistive elements is maximum) is 135 °.