JPS628122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation angle detection device that uses a magneto-electric transducer, and more particularly to a rotation detection device that uses a detection method that expands the angle detection range using a single magnetoresistive element.

An angle detection device for a rotating body using a magnetoresistive element detects the angle by sensing changes in the direction of the magnetic field of a permanent magnet attached to the rotating body. Usually, the detection range of a single magnetoresistive element is the same as that of the permanent magnet. ±45° with respect to the direction of the magnetic field. In other words, the electrical output voltage E of the angle sensor using a magnetoresistive element is equal to the reference applied voltage.
For E ₀ , the relationship is E=E ₀ sin2θ. Therefore, the conventional angle sensor using a magnetoresistive element only enables detection in a range of 1/4 rotation (1/2π), that is, in one quadrant.
It was not possible to detect all angles of rotation. In other words, it is virtually impossible to continuously detect the angle over the entire circumference of the rotating body using the magnetoresistive element.

Therefore, the present invention has been proposed in view of the above, and an object of the present invention is to provide a new and improved angle detection device using a magnetoresistive element.

The angle sensor according to the present invention is characterized in that, when a permanent magnet is attached to a rotating body of an object to be detected whose angle is to be detected, the magnetic direction of the permanent magnet is arranged at an angle with respect to the main axis direction of the rotating body. . In other words, a permanent magnet is arranged on the rotating body and has a magnetic axis formed at an inclination angle of 45° or less with respect to the main rotational axis of the rotating body, and a magnetoresistive element is fixedly arranged on a plane parallel to the rotational main axis of the rotating body. The magnetic field of a permanent magnet, which rotates integrally with the rotating body at a predetermined angle of inclination, affects the fixed side magnetic resistance element parallel to the rotational main axis to cause a resistance change that changes depending on the rotation angle. What should be noted here is the setting of the inclination angle between the rotation main axis and the magnetic axis, and by setting the inclination angle to 45° or less, the angle detection range of the magnetoresistive element was expanded to ±90°. . As a result, the angle detection range of one magnetoresistive element in the conventional method has been increased.

Another important feature of the present invention is that the permanent magnet has a magnetic axis inclined at an angle with respect to the main axis of the rotating body;
It is an object of the present invention to provide a rotation angle detection device comprising magnetoresistive elements fixedly arranged orthogonally to each other. And the electric output Ex=Esinθ and Ey=
By obtaining Ecos θ and inputting it to an x-y display device, the rotational state can be easily displayed, and it can be used as an input signal for an oscilloscope or an XY recorder. Further, the rotation angle detection device according to the present invention includes a wind direction indicator,
It has great practical applications, such as radar devices, track recording devices, electrical output converters for mechanical rotation indicators, and other applications such as detection of rotational irregularities and engine control.

In the rotation angle detection device of the present invention, as the above-mentioned inclination angle approaches zero, the electrical output level decreases, but on the other hand, the linearity of the rotation angle versus output is improved. Therefore, in order to improve detection accuracy, the tilt angle should be set small, and since improving linearity and increasing output level are contradictory, consideration must be given to this point.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a main part of a rotation angle detection device according to the present invention, which is a rotation angle detection device for a rotating body 1. FIG. The rotating body 1 has a shaft portion 2 extending in the axial direction, and a permanent magnet 5 is integrally attached to the rotating body 1 along a magnetic axis 4 having a specific inclination angle a with respect to the main axis of rotation 3. ing. Therefore, when the rotating body 1 rotates counterclockwise, that is, rotates by the rotation angle θ in the direction of the arrow of the main axis 3, the permanent magnet 5 moves to the position shown by the dotted line. On the other hand, first and second magnetoresistive elements 6 and 7 are fixedly arranged perpendicularly to a plane parallel to the main axis of rotation 3 of this rotating body 1, and electric circuits 8 and 9 are connected to them, respectively. outputs the detected value to the output terminals Ex and Ey of the electric circuit.

In the rotation angle detection device with the above configuration, the first magnetoresistive element 6 generates an electrical output Ex=Esinθ according to a change in the magnetic field direction of the permanent magnet 5 attached to the rotating body 1.
At the same time, the second magnetoresistive element 7 similarly generates an electrical output Ey=Ecos θ. However, E≒
E ₀ ·2tan a, details of which will be described later. Therefore, the detection output of the electric circuit with respect to the rotation angle of the rotating body 1 obtains an output curve shown in FIG. As is clear from this characteristic curve, each magnetoresistive element 6 or 7 exhibits an output change with one period of 2π (=360°), and the range of π (=180°) of ±90° is effective for angle detection. About the horn bird detection is possible. Therefore, two magnetoresistive elements 6, 7 arranged orthogonally to each other
The use of allows detection of all angles in one revolution. This is extremely practical because it simplifies the configuration of the angle detection device compared to conventional methods.

Figures 3 to 5 show electrical output Ex for detecting the magnetoresistive element in the angle detection device according to the present invention.
2 is a schematic diagram illustrating the introduction of =Esinθ and Ey=Ecosθ, and is a planar schematic diagram, an elevational schematic diagram, and a perspective schematic diagram, which are explained in relation to the angle detection device of FIG. 1. FIG. Here, the spherical rotating body 11 has its main axis 1
A permanent magnet 1 with a magnetic axis 14 having an inclination angle a with respect to 3
5 is carried in its central part, and this rotating body 1
It is configured to detect the angle θ of the rotating body by means of flat surfaces 16 and 17 of two magnetoresistive elements fixedly disposed orthogonal to a plane parallel to the main axis 13 of the rotating body. Next, consider the above-mentioned electrical output Ex=Esinθ of the magnetoresistive element 16 fixed on the X axis of the XY coordinate.

In FIGS. 3 and 4, a spherical rotating body 11
Suppose that it rotates about the main axis 13 by a rotation angle θ. In this case, one end of the permanent magnet on the north pole side moves from the first point 19 to the second point 20, causing a change in rotation angle θ, but due to the rotation of the rotating body, each moving point on the north pole side moves from the first point 19 to the second point 20. It can be assumed that a circular locus 18 is drawn as shown in the figure. Here, the magnetic axis 14 of the permanent magnet has an inclination angle α with respect to the main axis 13 of the rotating body, as shown in FIG. The change in the magnetic field is assumed to be a change in the conical plane of the vector r. Therefore, as is clear from FIG. 4, the vector component r ₁ of the magnetic field corresponding to the radius of the locus 18 is r ₁
=rsin〓.

On the other hand, as is clear from FIG. 3, the effective magnetic field component τx with respect to the plane 16 of the magnetoresistive element is a component parallel to this plane 16, rx=r ₁ sinθ=
The relationship between rsinα and sinθ can be derived. Also, the principal axis 1 projected onto the plane 16 of the magnetoresistive element
3 and the projected inclination angle of the magnetic axis 14 is ax, this inclination angle ax depends on the rotation angle θ, and tan ax=tan
Obtain the relationship a·sinθ or ax=tan ⁻¹ (tan a·sinθ). Therefore, the electrical output Ex due to the plane 16 of the magnetoresistive element is determined from the known relational expression as Ex=E ₀ sin2ax. Here E ₀ is the reference operating voltage.
This electrical output Ex is converted from the above-mentioned relational expression as follows.

Ex＝E ₀ sin2ax＝ E ₀ sin {2tan ^-1 (2tan a ^-1・sinθ)} On the other hand, if tan a≒0, tan a・sinθ≒0
And when x≈0, tan ⁻¹ x≈x, so tan ⁻¹ (tan a·sinθ)≒tan a·sinθ. Also, when x≒0, sin x≒x also holds, so
Ex＝E ₀ sin {(2tan a)・sinθ}≒E ₀ (2tan
a) Obtain ・sin θ. That is, Ex=Esinθ is obtained (here, E≈E ₀ ·2tan a, meaning that the absolute value of the output changes depending on the setting of the inclination angle a).

Electrical output to plane 17 of magnetoresistive element
Similarly, for Ey, we obtain the relationship Ey=Ecosθ≒E ₀・2tana.

The above relationship may also be explained using the perspective schematic diagram of FIG. That is, as shown in FIG. 5, the main axis 13 of the rotating body and the magnetic axis 14 of the permanent magnet
When rotates with an angle of inclination a, the vector r of the magnetic field of the permanent magnet forms a cone with an apex angle 2a and moves within the plane of the cone. Here, the rotation angle θ
The change in is assumed as a change from point 19 to point 20, and the plane 16, 1 of each magnetoresistive element on the XY axis
The effective magnetic field components rx, ry detected by 7 are magnetic field changing components parallel to each plane, and are projected onto each plane at an inclination angle a according to changes in the projection inclination angle ay, ay, that is, the rotation angle θ. Change. Therefore,
The following relationship can also be obtained from FIG.

ax=tan ^-1 (tan a・sinθ), rx=r(sin a・
sin θ) Rx=r(cos ² a+sin ² a・sin ² θ), and ay=tan ⁻¹ (tan a・cosθ), ry=r(sin
a・cos θ) Ry=r(cos ² a+sin ² a・cos ² θ) As a result, we obtained the relationship characteristic curves Ex and Ey of electrical output against rotation angle shown in Fig. Effectively doubles the detection range to 180°.

It should be noted that the closer the value of a is to zero regarding the inclination angle a of the magnetic axis 14 with respect to the main axis 13, the closer the error angle θ' in the detection angle θ approaches zero, resulting in an improvement in linearity. On the other hand, as the inclination angle a approaches zero, the absolute value of the electrical output e becomes smaller. Furthermore, even under the same inclination angle, the error angle θ' and the electrical output e change depending on the value of the detection angle θ. This change not only changes the error angle to positive or negative every 45 degrees in the value of the detected angle θ, but also changes the error angle θ' and the output e periodically. Table 1 shows "error angle θ' at detection angle θ" and Table 2 shows "relative output e at detection angle θ".
were obtained from actual calculations using the inclination angle a as a variable, and are shown at the first period of the 45° periodic variation.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing the angle detection device according to the present invention, FIG. 2 is a characteristic diagram of the electrical output obtained by the electric circuit regarding the rotation of FIG. 1, and FIGS. FIG. 3 is an explanatory schematic diagram for deriving the relationship between the figures, and is a plan view, an elevation view, and a perspective schematic view, respectively. 1, 11... Rotating body, 3, 13... Main axis (line), 4, 14... Magnetic axis (line), 5... Permanent magnet, 6, 7, 16, 17... Magnetic resistance element (plane) ), 18...trajectory.

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Claims (1)

[Scope of Claims] 1. A permanent magnet having a magnetic axis formed at an inclination angle of 45° or less with respect to the main rotational axis of a rotating body, a magnetoresistive element disposed in a plane parallel to the rotational main axis, and this magnetoresistive element. A rotation angle detection device comprising: an electric circuit that drives a rotor and outputs a change in resistance thereof; and detects a rotation angle of the rotating body as an output of the electric circuit through the intervention of a resistance value of the magnetoresistive element. 2. The magnetoresistive element includes first and second magnetoresistive elements disposed on mutually orthogonal planes, and the electric circuit combines outputs corresponding to the resistance values of the respective magnetoresistive elements and generates a signal for the rotating body. The rotation angle detection device according to claim 1, which is capable of detecting all angles.