JP2000298037A - Rotation sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect rotation displacement of a rotor by improving the resolution. SOLUTION: A rotation sensor 1 has a gear 2 and a pair of magnetic reluctance elements 3 and 4 arranged facing to the gear 2. One magnetic reluctance element 3 is arranged with a shift to the other magnetic reluctance element 4 to the direction perpendicular to the rotation direction. By this, the magnetic reluctance elements 3 and 4 can be arranged close in the rotation direction of the gear 2 and the change in the magnetic field due to the rotation of the gear 2 can be detected at high resolution. That is, the change in the magnetic field due to the rotation of the gear 2 is output as electric signal due to the reluctance change of the magnetic reluctance elements 4 and 5, and with the output signal, the rotation displacement of the gear 2 is exactly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation sensor for detecting a rotational displacement of a rotating body using a magnetoelectric conversion element.

[0002]

2. Description of the Related Art Conventionally, as a rotation sensor, for example, a magnetic rotation sensor using a magnetoelectric element such as a magnetoresistive element has been known (Japanese Patent Application Laid-Open No. H8-233841). This type of rotation sensor detects the number of rotations, rotation position, and the like of a rotating body from a change in a magnetic field accompanying rotation of the rotating body.

A magnetoresistive element is an element whose electric resistance changes according to an applied magnetic field. A rotation sensor using the element always outputs a signal of the same level regardless of the rotation speed of a rotating body. It has advantages such as long operating life. On the other hand, magnetoresistive elements have poor temperature characteristics,
Rotation detection is performed using two magnetoresistive elements.

More specifically, as shown in FIGS. 8 (a) and 8 (b), a rotation sensor 20 is arranged opposite to a gear 21 fixed to a rotation shaft (not shown). It has a pair of magnetoresistive elements 22 and 23, and the rotational sensor 20 detects the rotational displacement of the rotating shaft. Gear 21
Is made of a magnetic material and has a plurality of convex teeth formed on an outer peripheral surface thereof. The magneto-resistive element 22 is a magneto-resistive element 2
3, the magnetic field applied to the magnetoresistive elements 22 and 23 changes according to the rotation of the gear 21 in a direction shifted by ピ ッ チ pitch in the rotation direction of the gear 21 (the direction of the arrow X in the figure). It is configured as follows. Here, one pitch refers to the interval between adjacent teeth.

More specifically, as shown in FIG.
2 and the convex teeth (convex portions) of the gear 21 face each other,
The magnetic field applied to the magnetoresistive element 22 increases, and the electric resistance of the magnetoresistive element 22 increases. Further, the magnetic field applied to the magnetoresistive element 23 is reduced by opposing the magnetoresistive element 23 and the tooth groove (recess) of the gear 21,
The electric resistance of the magnetoresistive element 23 decreases. Therefore, by connecting the magnetoresistive elements 22 and 23 in series and outputting the midpoint potential as a sensor output, an output signal corresponding to the teeth of the gear 21 can be obtained. In addition, the influence of temperature can be canceled by the configuration that outputs the midpoint potential of the magnetoresistive elements 22 and 23 connected in series. The rotational displacement of the rotary shaft is detected based on the output signal of the rotation sensor 20, and various controls are performed.

In recent years, a rotation sensor having a high resolution has been desired in order to increase control accuracy. for that reason,
The teeth formed on the outer peripheral surface of the gear 21 are made finer to improve the resolution of the rotation sensor.

[0007]

However, there is a limit to providing the magnetoresistive elements 22 and 23 in the rotation direction of the gear 21. If the teeth of the gear 21 become fine and the pitch becomes narrow as shown in FIG. In addition, the two magnetoresistive elements 22 and 23 simultaneously face the convex teeth (or tooth grooves), and the rotation of the gear 21 cannot be detected. That is, 2
Since the electric resistances of the two elements 22 and 23 change similarly, an output signal corresponding to the rotation of the gear 21 cannot be obtained, and the rotational displacement of the rotating shaft cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a rotation sensor capable of improving the resolution and accurately detecting the rotational displacement of a rotating body. is there.

[0009]

According to a first aspect of the present invention, there is provided a magnetic recording device, comprising: a pair of magneto-electric conversion elements disposed opposite to a rotating body; In the rotation sensor for detecting the change in the position, one of the pair of magnetoelectric conversion elements is shifted in the rotation direction of the rotating body with respect to the other magnetoelectric conversion element and is shifted in the direction orthogonal to the rotation direction. The point is to do. According to a second aspect of the present invention, in the rotation sensor according to the first aspect, the rotating body is a gear having a plurality of convex teeth formed on an outer peripheral surface thereof. The gist of the invention is that the element is shifted by 変 換 pitch in the rotation direction of the gear with respect to the magnetoelectric conversion element. According to a third aspect of the present invention, in the rotation sensor according to the first or second aspect, the magnetoelectric conversion element is a magnetoresistance element whose electric resistance changes according to an applied magnetic field. According to a fourth aspect of the present invention, there is provided a pair of the rotation sensors according to any one of the first to third aspects, and one of the rotation sensors is displaced in the rotation direction of the rotating body with respect to the other rotation sensor. In addition, the gist is to displace in the direction orthogonal to the rotation direction. According to a fifth aspect of the present invention, in the rotation sensor according to the fourth aspect, the one rotation sensor is rotated one direction with respect to the other rotation sensor.
The gist of the invention is to dispose it by / 4 pitch.

(Operation) According to the first aspect of the present invention,
By displacing one magnetoelectric conversion element in the direction orthogonal to the rotation direction with respect to the other magnetoelectric conversion element, it is possible to arrange each magnetoelectric conversion element close to the rotation direction of the rotating body Becomes Therefore, if each magnetoelectric conversion element is arranged close to the rotating direction of the rotating body, a change in the magnetic field accompanying the rotation of the rotating body can be detected with high resolution. That is, the resolution is improved, and the rotational displacement of the rotating body is accurately detected.

According to the second aspect of the present invention, one of the magnetoelectric conversion elements is disposed at a position shifted from the other magnetoelectric conversion element by a half pitch in the rotation direction of the gear. Is opposed to the convex tooth, the other magnetoelectric conversion element is opposed to the tooth groove. Therefore, a change in the magnetic field due to the rotation of the gear is properly detected by the pair of magneto-electric conversion elements. According to the invention described in claim 3, the electric resistance of the magnetoresistive element changes according to the applied magnetic field,
The rotational displacement of the rotating body is detected by the resistance change.

According to the fourth aspect of the present invention, one of the rotation sensors is displaced from the other rotation sensor in the rotation direction of the rotating body. Is a signal whose phase is shifted from the output signal of the rotation sensor. Therefore, it is possible to detect the rotation direction of the rotating body by using the two output signals whose phases are shifted. Further, since one rotation sensor is displaced from the other rotation sensor in a direction orthogonal to the rotation direction, the resolution of the sensor output is improved.

According to the fifth aspect of the present invention, the output signal of one rotation sensor is a signal whose phase is shifted by 90 ° from the output signal of the other rotation sensor. Therefore, using these signals, it is possible to generate a signal having twice the resolution with respect to a change in the magnetic field.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

The rotation sensor according to the present embodiment is applied to a power steering device. For example, the rotation sensor is disposed on a steering shaft and detects a steering angle according to an operation of a steering wheel.

FIG. 1A is a side view showing a schematic configuration of the rotation sensor 1 in the present embodiment, and FIG.
It is the top view. As shown in FIGS. 1A and 1B, a rotation sensor 1 includes a gear 2 fixed to a steering shaft (not shown), and a pair of magnetoresistive elements 3 and 4 arranged opposite to the gear 2. And Note that a predetermined magnetic field is applied to the pair of magnetoresistive elements 3 and 4 by a magnet (not shown) disposed behind the pair of magnetoresistive elements.

The gear 2 is made of a magnetic material, and has a number of convex teeth formed on the outer peripheral surface of the gear 2 so that the direction of the tooth trace is parallel to the axis. The tooth thickness of the gear 2 is equal to the width of the tooth groove. Each of the magnetoresistive elements 3 and 4 is a rectangular element having two terminals, and is formed of, for example, a semiconductor material of InSb. The magnetoresistive element 3 is shifted from the magnetoresistive element 4 by a half pitch in the rotation direction (the arrow direction X in the drawing), and as shown in FIG. (Direction) is shifted by a predetermined distance. Here, one pitch refers to the interval between adjacent teeth. Thus, the two magnetoresistive elements 3,
By displacing 4 in a direction orthogonal to the rotation direction, the distance between the two magnetoresistive elements 3 and 4 in the rotation direction (the X arrow direction in the figure) is reduced as shown in FIG. State.

Next, a detection circuit of the rotation sensor 1 will be described with reference to FIG. As shown in FIG. 2, a predetermined voltage V is applied to the magnetoresistive elements 3 and 4 connected in series. Then, both ends of the magnetoresistive element 3 are connected to the controller 5, and the potential of the midpoint A of the magnetoresistive elements 3 and 4 (voltage applied to the magnetoresistive element 3) is output to the controller 5 as a sensor output.

In the above configuration, the magnetoresistive elements 3, 4
Is that the magnetic field applied when facing the convex teeth of the gear 2 increases, the electrical resistance increases, and the tooth grooves (recesses) of the gear 2
When applied, the applied magnetic field decreases and the electric resistance decreases. Therefore, as shown in FIG. 1, when the magnetoresistive element 3 faces the convex teeth of the gear 2 and the magnetoresistive element 4 faces the recess of the gear 2, the electric resistance of the magnetoresistive element 3 increases. Then, since the electric resistance of the magnetoresistive element 4 decreases,
The output of the rotation sensor 1 becomes Hi level. When the gear 2 rotates by a half pitch from the state shown in FIG. 1, the magnetoresistive element 3 and the concave portion of the gear 2 face each other, and the magnetoresistive element 4 and the convex teeth of the gear 2 face each other. In this case, the electric resistance of the magnetoresistive element 3 decreases and the electric resistance of the magnetoresistive element 4 increases, so that the output of the rotation sensor 1 becomes Lo level.

As a result, the controller 5 can obtain a detection signal corresponding to the teeth of the gear 2 as shown in FIG. Specifically, a signal that repeats Hi / Lo according to the rotation of the gear 2 at a half pitch can be detected. That is, one pitch rotation of the gear 2 corresponds to the period T of the detection signal. Therefore, based on this signal, the controller 5 can detect the rotational displacement of the gear 2, that is, the rotational displacement of the steering shaft.

In this embodiment, the gear 2 corresponds to a rotating body, and the magnetoresistive elements 3 and 4 correspond to magneto-electric conversion elements. The rotation sensor 1 and the controller 5 constitute a rotation detection device.

As described above, the present embodiment has the following features. (1) One magnetoresistive element 3 is replaced with the other magnetoresistive element 4
To the direction orthogonal to the rotation direction of the gear 2 (tooth trace direction)
, Each magnetoresistive element 3, 4
The gears 2 can be arranged at arbitrary intervals in the rotation direction. Therefore, if the magnetoresistive element 3 is arranged close to the magnetoresistive element 4 in the rotation direction of the gear 2 as shown in FIG. 1, a change in the magnetic field accompanying the rotation of the gear 2 can be detected with high resolution. That is, the rotational displacement of the steering shaft can be detected with high accuracy. Therefore, if the rotation sensor 1 of the present embodiment is applied, the control accuracy of the power steering device can be improved.

(2) Since the magnetoresistive elements 3 and 4 are arranged with a shift of 1/2 pitch in the rotation direction of the gear 2, one of the magnetoresistive elements 3 and 4 is provided with the convex teeth of the gear 2. When facing, the other element will face the gear groove (recess) of the gear 2. Therefore, a change in the magnetic field accompanying the rotation of the gear 2 can be properly detected.

(3) In this embodiment, the magnetoresistive elements 3 and 4 having two terminals are applied as magnetoelectric elements.
Therefore, the circuit configuration is simpler than that of a rotation sensor using a Hall element having four terminals, which is practically preferable.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described. In addition, about the structure similar to 1st Embodiment, the detailed description and drawing are abbreviate | omitted.

As shown in FIG. 4, the rotation sensor 10 of the present embodiment is embodied by adding a pair of magnetoresistive elements 11 and 12 to the rotation sensor 1 of FIG. More specifically, the pair of magnetoresistive elements 11 and 12 are shifted from the pair of magnetoresistive elements 3 and 4 described above by １ ／ pitch in the rotational direction, and at the same time, in the direction perpendicular to the rotational direction of the gear 2 (tooth trace Direction). In addition,
The magnetoresistive element 11 is arranged at a position shifted from the magnetoresistive element 12 by a half pitch in the rotation direction and at a predetermined distance in a direction orthogonal to the rotation direction. Then, as shown in FIG. 5, the magneto-resistive elements 11 and 12 connected in series are connected in parallel to the magneto-resistive elements 3 and 4. The midpoint B between the magnetoresistive element 11 and the magnetoresistive element 12 is connected to the controller 5, and the potential of the midpoint B (voltage applied to the magnetoresistive element 11)
Is output to the controller 5.

With this configuration, the magnetoresistive element 3,
4 (see FIG. 6A), a quarter pitch, that is, when the period T is 360 °,
A signal with a 90 ° phase shift (see FIG. 6B) can be obtained. Based on these signal changes, the controller 5
Can determine the rotation direction of the gear 2.

From these output signals, it is possible to obtain a signal shown in FIG. 6C by using, for example, an exclusive OR circuit. That is, it is possible to obtain a signal having twice the resolution with respect to a change in the magnetic field according to the teeth of the gear 2.

In this embodiment, one rotation sensor is constituted by the pair of magnetoresistive elements 3 and 4, and the other is constituted by the pair of magnetoresistive elements 11 and 12.

As described above, the present embodiment has the following features. (1) By using the magnetoresistive elements 11 and 12, a signal whose phase is shifted by 90 ° from the output signal from the magnetoresistive elements 3 and 4 can be obtained, and the rotation direction of the gear 2 can be determined. Further, it is possible to obtain a signal having twice the resolution with respect to a change in the magnetic field due to the rotation of the gear 2.

The above embodiments may be implemented in the following modes. In the above embodiments, the magnetoresistive elements 3, 4, 11, and 12 are applied as magnetoelectric elements, but Hall elements may be used. Specifically, for example, the present invention is applied to a rotation sensor that detects a rotational displacement, a rotational direction, and the like of a rotating body using two Hall elements. Also in this case, the resolution of the sensor can be increased, and the control accuracy can be improved.

In the above embodiments, the rotation sensors 1, 1
Although 0 is for detecting the rotational displacement of the steering shaft, for example, in a power steering device, it may be for detecting the rotational displacement of a drive motor for generating a steering assist force. In this case, the gear 2 is fixed to the rotating shaft of the drive motor, and the rotational displacement of the rotating shaft is detected.

In addition, the rotation sensors 1, 1
0 may be applied to detection of rotational displacement of a rotating body not only in an automobile but also in a home electric appliance or the like. In each of the above embodiments, the magnetoresistive elements 3 and 11 are arranged so as to be shifted from the magnetoresistive elements 4 and 12 by ピ ッ チ pitch in the rotational direction, but the present invention is not limited to this. For example, as shown in FIG.
And the magnetoresistive element 15 may be embodied by overlapping with each other in the rotation direction of the gear 2 (the X arrow direction in the figure). Also in this case, the rotational displacement of the gear 2 can be detected. In short, it is sufficient that the pair of magnetoelectric conversion elements are arranged so as to be shifted in the rotation direction and also shifted in the direction orthogonal to the rotation direction.

In the second embodiment, the pair of magnetoresistive elements 11 and 12 are shifted from the pair of magnetoresistive elements 3 and 4 by １ ／ pitch in the rotation direction of the gear 2. It is not limited to. For example, a pair of magnetoresistive elements 11 and 12 are provided for a pair of magnetoresistive elements 3 and 4.
May be shifted by 3/4 pitch in the rotation direction.
Also in this case, an output signal having a phase shift of 90 ° can be obtained. Further, it is not always necessary to obtain a signal whose phase is shifted by 90 °, and any signal may be arranged so as to be shifted in the rotation direction so that the rotation direction can be detected by the two output signals.

Further, technical ideas other than the claims grasped by the above embodiment will be described below together with their effects. (A) A rotation detecting device comprising the rotation sensor according to any one of claims 1 to 5, and detecting a rotational displacement of the rotating body based on an output signal from the rotation sensor. According to this configuration, the rotational displacement of the rotating body can be detected with a high resolution, which is practically preferable.

[0036]

As described in detail above, according to the present invention,
By displacing one magnetoelectric conversion element in the direction orthogonal to the rotation direction of the rotating body with respect to the other magnetoelectric conversion element, the resolution can be improved and the rotational displacement of the rotating body can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a rotation sensor according to a first embodiment.

FIG. 2 is a circuit diagram of a detection circuit according to the first embodiment.

FIG. 3 is a diagram illustrating an output waveform of a rotation sensor according to the first embodiment.

FIG. 4 is a diagram illustrating a rotation sensor according to a second embodiment.

FIG. 5 is a circuit diagram of a detection circuit according to a second embodiment.

FIG. 6 is a diagram showing an output waveform of a rotation sensor according to a second embodiment.

FIG. 7 is a diagram showing a rotation sensor according to another embodiment.

FIG. 8 is a schematic configuration diagram showing a conventional rotation sensor.

FIG. 9 is a schematic configuration diagram showing a conventional rotation sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotation sensor, 2 ... Gear as a rotating body, 3,4 ... Magnetic resistance element as a magnetoelectric conversion element, 10 ... Rotation sensor,
11, 12: magnetoresistive elements as magnetoelectric elements, 1
4, 15: magnetoresistive elements as magnetoelectric elements.

Claims (5)

[Claims] 1. A rotation sensor for detecting a change in a magnetic field accompanying rotation of a rotating body by a pair of magnetoelectric elements arranged opposite to a rotating body, wherein one of the pair of magnetoelectric converting elements is A rotation sensor which is displaced in the direction of rotation of the rotator with respect to the other magnetoelectric conversion element and is displaced in a direction orthogonal to the direction of rotation. 2. The rotation sensor according to claim 1, wherein the rotating body is a gear having a plurality of convex teeth formed on an outer peripheral surface thereof, wherein the one magnetoelectric conversion element and the other magnetoelectric conversion element are provided. A rotation sensor, wherein the rotation sensor is disposed so as to be shifted by a half pitch in the rotation direction of the gear. 3. The rotation sensor according to claim 1, wherein the magnetoelectric conversion element is a magnetoresistance element whose electric resistance changes according to an applied magnetic field. 4. A pair of the rotation sensors according to claim 1, wherein one of the rotation sensors is shifted in the rotation direction of the rotating body with respect to the other rotation sensor. A rotation sensor, which is displaced in a direction orthogonal to the rotation sensor. 5. The rotation sensor according to claim 4, wherein said one rotation sensor is shifted by １ ／ pitch in a rotation direction with respect to the other rotation sensor.