JPH042914A - Angle sensor - Google Patents

Abstract

PURPOSE:To effectively decide the angular displacement of an object in a range over 90 degrees by so providing a permanent magnet and a magnetoresistance element as to be radially deviated from the axial center of the shaft to be detected. CONSTITUTION:A disklike holding member 10 formed of nonmagnetic metal is secured to the end of a shaft 1 rotatably supported in a direction of an arrow M. A cutout 10a extending from part of the circumference in a direction of an axial center O is formed, and a permanent magnet 11 is engaged within the cutout 10a. Thus, the magnet 11 is radially deviated to the axial center O. A magnetoresistance element 13 is disposed oppositely at a predetermined gap to the member 10, and radially deviated from the center O. Thus, each time the shaft 1 is rotated one revolution, the magnet 11 is once approached to the element 13 and separated therefrom. Each time the shaft 1 is rotated at 180 degrees, an output voltage varying in response to the resistance of the element 13 is linearly increased and decreased repeatedly to effectively determine the angular displacement of the shaft in a range over 90 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an angle sensor that detects the rotation angle of a shaft to be detected using a magnetoresistive element (MR element).

"Prior Art" Conventionally, an angle sensor using a magnetoresistive element has been constructed as shown in FIG. In this figure, ■ is caused by an arrow M centered around the axis O (not shown) due to a bearing (not shown).
A permanent magnet 2 in the form of a disk is fixed to one end of the shaft. In this case, the permanent magnet 2 is arranged so that one end on its circumference becomes a north pole and the other end becomes a south pole.

Reference numeral 3 denotes a magnetoresistive element which is placed opposite the permanent magnet 2 with a certain gap therebetween, is placed on the axis O''-, and is fixed to a casing (not shown). The magnetoresistive element 3 is made of an element material that has a phenomenon in which the specific resistance changes depending on the strength of the magnetic field (magnetoresistive effect). In this case, the element material may include a semiconductor such as In5b (indium antimony), Or NiFe or NiFe) or N1-
A ferromagnetic material such as Go (nickel cobalt) is used.

In such a configuration, when the permanent magnet 2 rotates in the direction of the arrow M, the strength of the magnetic field acting on the magnetoresistive element 3 changes depending on the rotation angle, and as a result, the strength of the magnetic field acting on the magnetoresistive element 3 changes.
resistance changes. By detecting the resistance change of the magnetoresistive element 3 as a voltage change, an output voltage corresponding to the rotation angle of the Noyaft I can be obtained as shown in FIG. In this case, the output voltage of the magnetoresistive element 3 is
Each time it rotates 90 degrees in one direction, it alternates linear increases and decreases. The linear portion of this output voltage waveform is then used as a portion proportional to the rotation angle.

"Problems to be Solved by the Invention" By the way, in the conventional angle sensor described above, the range in which the output voltage is linear is less than 90 degrees, so the range in which the rotation angle of the shaft I can be effectively determined is limited. There was a problem in that the angle was limited to less than 90 degrees. Furthermore, since the disk-shaped permanent magnet 2 is used, a large amount of expensive permanent magnets + and IN are required, which is one factor that increases manufacturing costs.

This invention was made in view of a series of circumstances, and aims to provide an angle sensor that can effectively discriminate rotation angles of 90 degrees or more and that reduces manufacturing costs. The purpose is

"Means for Solving the Problem" The present invention is directed to a magnetic resistor arranged opposite to the holding member with a certain gap between the magnetic field of the permanent magnet picked up on the shaft to be detected via the holding member +4. An angle sensor that detects the rotation angle of the shaft to be detected by detecting it with an element, characterized in that the permanent magnet and the magnetic resistance element are arranged eccentrically in the radial direction from the axis of the shaft to be detected. It is said that

1 Effect" According to the above configuration, since the permanent magnet and the magnetic resistance element are arranged eccentrically in the radial direction from the axis of the detected shaft,
Every time the detected axis rotates once, the permanent magnet approaches and separates from the magnetoresistive element only once, so that the detected axis
Every time the magneto-resistance element rotates by 0 degrees, the output voltage, which changes depending on the resistance of the magnetoresistive element, alternately increases and decreases linearly.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention. In this figure, reference numeral 10 denotes a disc-shaped holding member made of non-magnetic metal, and is fixed to the end of the shaft 1, which is rotatably supported in the direction of arrow M shown in the figure by a bearing (not shown). . This holding member IO has a notch extending from the circumference "-" in the direction of the axis °0.
a is formed, and a permanent magnet 1 is placed inside this notch 10a.
1 is inserted. Thereby, the permanent magnet II is arranged eccentrically in the radial direction with respect to the axis O.

Further, the permanent magnet 11 is arranged so that one end along the axis 0 is a north pole, and the other end is a south pole. On the other hand, 1
3 is arranged opposite to the holding member 10 with a certain gap in between,
Moreover, it is a magnetoresistive element arranged eccentrically in the radial direction from the axis O.

In such a configuration, when the shaft 1 rotates, the permanent magnet 11 approaches and separates from the magnetoresistive rope 13 only once for every rotation of the shaft 1. This results in
As shown in FIG. 3, each time the shaft l rotates 180 degrees, the output voltage, which changes according to the resistance of the magnetoresistive element 13, alternately increases and decreases linearly, and as a result, the output voltage linearly increases and decreases. The range of rotation angle is 90 degrees or more, and the range in which rotation angle can be effectively determined is 90 degrees or more.
− becomes.

Next, FIG. 2 is a diagram showing the configuration of another embodiment of the present invention. In this embodiment, the permanent magnets 11 are arranged eccentrically in the radial direction with respect to the axis 0, and the permanent magnets 11 are arranged along the radial direction so that the inner side is the N pole and the outer side is the S pole. Even in such a configuration, as in the embodiment described above, the output voltage alternately increases and decreases linearly every time the Nyafu 1.1 rotates 180 degrees (see Figure 3). , the range in which the rotation angle can be effectively determined is 90 degrees or more.

"Effects of the Invention" As explained above, according to the present invention, since the permanent magnet and the magnetoresistive element are arranged eccentrically in the radial direction from the axis of the shaft to be detected, each rotation of the shaft to be detected is In this case, the permanent magnet approaches and separates from the magnetoresistive element only once, so that the output voltage, which changes according to the resistance of the magnetoresistive element, changes linearly every time the detected shaft rotates 180 degrees. As a result, the range in which the output voltage has linearity becomes 90 degrees or more, and the range in which the rotation angle can be effectively determined becomes 90 degrees or more. Furthermore, the permanent magnet that is attached to the detection shaft via the holding member can be smaller than the conventional one, and the manufacturing cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention, and FIG.
Figure 3 is a perspective view showing the configuration of another embodiment of the invention, Figure 3 is a graph showing the relationship between the rotation angle and output voltage of each embodiment of the invention, Figure 4 is a graph of a conventional angle sensor. Fig. 5 is a graph showing the relationship between the rotation angle and the output voltage of the angle sensor.Shaft, - Permanent magnet, - Holding member, - Magnetoresistive element.

Claims (1)

[Scope of Claims] The detected object is detected by detecting the magnetic field of a permanent magnet attached to the detected shaft via a holding member by a magnetoresistive element disposed facing the holding member with a certain gap therebetween. An angle sensor for detecting a rotation angle of a shaft, wherein the permanent magnet and the magnetic resistance element are arranged eccentrically in a radial direction from the axis of the shaft to be detected.