JP2009002737A - Rotation angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detector 1 which can reduce an angular error and prevent deterioration in response without increasing sensor size and costs. <P>SOLUTION: The rotation angle detector 1 has a circular base magnet 3 and an auxiliary magnet 4 fixed to a rotating shaft 2 and two Hall elements 6, 7 which are arranged so that their magnetosensitive surfaces are orthogonal to each other. When there is a phase shift between the outputs of the two Hall elements 6, 7, it is corrected by displacing the rotation angle position of the auxiliary magnet 4 by a predetermined angle in accordance with the phase shift. In other words, the rotation angle position of the auxiliary magnet 4 is displaced by a predetermined angle with respect to the base magnet 3 so that the phase shift between the two outputs caused by the arrangement displacement of the two Hall elements 6, 7 is zero degree, or so that the phase difference between the two outputs is 90 degrees. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotation angle detection device that detects a rotation angle of, for example, a throttle valve or a steering wheel of an automobile.

As a prior art, there is a rotation angle detection device disclosed in Patent Document 1.
As shown in FIG. 11, the rotation angle detection device includes a disk-shaped magnet 110 attached to the rotation shaft 100 and two Hall elements (first Hall element 120, Second Hall element 130). FIG. 11A is an axial plan view of the rotation angle detection device, and FIG. 11B is a side view of the device.
The first Hall element 120 is arranged such that the magnetic sensitive surface for detecting magnetism faces the rotation axis 100 which is the rotation center of the magnet 110, and the second Hall element 130 has the magnetic sensitive surface for detecting magnetism as the first magnetic element. The hall element 120 is disposed so as to face in a direction orthogonal to the magnetic sensitive surface. That is, the two Hall elements 120 and 130 are arranged so that their outputs are in a phase relationship that is shifted by 90 °.

According to the above configuration, the phase of the output of the first Hall element 120 and the output of the second Hall element 130 is shifted by 90 degrees. Therefore, when the magnet 110 rotates together with the rotating shaft 100, as shown in FIG. A sine wave signal a is output from the Hall element 120, and a cosine wave signal b is output from the second Hall element 130. By converting these two outputs into linear characteristics by inverse trigonometric function calculation, the rotation angle of the rotating shaft 100 can be detected in the range of 0 ° to 360 °.
JP 2003-75108 A

However, in the above rotation angle detection device, if the first Hall element 120 and the second Hall element 130 are misaligned with respect to the magnet 110, the output of the first Hall element 120 and the output of the second Hall element 130 are A phase shift occurs between them.
For example, as shown in FIG. 6, when the magnetic sensitive surfaces of the first Hall element 120 and the second Hall element 130 are inclined with respect to the magnet 110 by a predetermined angle α (hereinafter referred to as displacement), as shown in FIG. In addition, the phase difference between the output of the first Hall element 120 and the output of the second Hall element 130 does not become 90 °, and a phase shift occurs.

Note that the graph shown in FIG. 6 shows that the output signals (the output a of the first Hall element 120, the second Hall element 130) when the two Hall elements 120 and 130 are normally arranged, that is, there is no misalignment. Output b) and output signals (output a1 of the first Hall element 120, output b1 of the second Hall element 130) when the two Hall elements 120 and 130 have a displacement of α = 5 ° are shown. ing.
Comparing the output when there is no misalignment between the two Hall elements 120 and 130 and the output when there is a misalignment, the output a of the first Hall element 120 and the output of the second Hall element 130 when there is no misalignment. Whereas the phase difference from the output b is 90 °, the phase difference between the output a1 of the first Hall element 120 and the output b1 of the second Hall element 130 when there is a misalignment is 78.3 °. ing. When the rotation angle is detected based on the output when the two Hall elements 120 and 130 are misaligned, an angle error is generated according to the rotation angle position of the magnet 110 as shown in FIG.

By the way, as a means for reducing the angle error, a method of reading the output of the first Hall element 120 and the output of the second Hall element 130 with an IC and correcting the map so as to reduce the phase shift between them can be considered. However, this method requires a large number of maps in order to further reduce the angle error, so that the circuit scale of the IC increases, leading to an increase in sensor size and cost. Furthermore, since the correction value in the map is output, there is a drawback that the response speed is also slow.
The present invention has been made based on the above circumstances, and its purpose is to reduce the angle error caused by the misalignment of the two magnetic detection elements without increasing the physique of the sensor or increasing the cost. And it is providing the rotation angle detection apparatus which can prevent the deterioration of responsiveness.

(Invention of Claim 1)
The present invention is arranged in a disk shape or a ring shape, is magnetized in the radial direction, and rotates integrally with a rotating shaft disposed in the center of the radial direction, and a magnetic field generated by the magnet. A rotation angle detecting device for detecting a rotation angle of a rotary shaft based on a change in magnetism detected by the two magnetic detection elements. Each of the magnetic detection elements is arranged in a positional relationship in which both magnetic detection surfaces are orthogonal to each other, and the magnet is composed of a first magnet and a second magnet, and the first magnet and the second magnet rotate. The rotation angle position of the first magnet and the second magnet is arranged adjacent to each other in the axial direction of the shaft or at a predetermined interval, and according to the phase shift of the outputs of the two magnetic detection elements The phase shift of the outputs of the two magnetic detection elements is made relatively by shifting the angle by a predetermined angle. Characterized in that it positive.

In the rotation angle detection device of the present invention, two magnetic detection elements are arranged in the combined magnetic field of the first magnet and the second magnet, and the rotation angle is detected based on the outputs of the two magnetic detection elements. ing. In this configuration, when the rotation angle positions of the first magnet and the second magnet are relatively shifted, the strength of the combined magnetic field is changed, and the output phase difference between the two magnetic detection elements is shifted. Therefore, when a phase shift occurs between the outputs of the two magnetic detection elements, in other words, when the phase difference between the two outputs deviates from the original phase difference (for example, 90 °), the phase difference shift ( (Referred to as phase shift), the phase shift between the two outputs can be corrected by relatively shifting the rotational angle positions of the first magnet and the second magnet by a predetermined angle.
According to this method, it is not necessary to perform map correction in order to reduce the phase shift between the two outputs, so there is no need to increase the physique of the sensor or increase the cost, and it is necessary to output a correction value on the map. Therefore, the responsiveness is not deteriorated.

(Invention of Claim 2)
The rotation angle detection apparatus according to claim 1, wherein the first magnet and the second magnet have the same shape and the same performance.

(Invention of Claim 3)
3. The rotation angle detection device according to claim 1, wherein each of the two magnetic detection elements is a Hall element that outputs an electric signal corresponding to a magnetic flux density, and the two Hall elements are arranged in one chip. It is characterized by comprising one mounted Hall IC.

(Invention of Claim 4)
The rotation angle detection device according to claim 3 is characterized in that the Hall IC has a correction function capable of adjusting the offset and gain of the outputs of the two Hall elements.

(Invention of Claim 5)
5. The rotation angle detection device according to claim 3, wherein the Hall IC is placed radially outward from the outer peripheral edges of the first magnet and the second magnet, and the first magnet and the second magnet. Are arranged within the range of the axial thickness.

(Invention of Claim 6)
6. The rotation angle detecting device according to claim 5, wherein the Hall IC is arranged on one side of two magnets within an axial thickness obtained by combining the first magnet and the second magnet. It is characterized by being installed within the thickness range of the magnet.

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

FIG. 1A is an axial plan view of the rotation angle detection device 1, and FIG. 1B is a side view of the rotation angle detection device 1.
As shown in FIG. 1 (b), the rotation angle detection device 1 of the present embodiment is arranged with two magnets 3 and 4 fixed to the rotation shaft 2 and close to the two magnets 3 and 4. One Hall IC 5 is provided. The two magnets 3 and 4 are a base magnet 3 and an auxiliary magnet 4 having the same shape and the same performance, and as shown in FIG. It is magnetized. That is, it is magnetized so that half of the radial direction is the S pole and the other half is the N pole. The base magnet 3 and the auxiliary magnet 4 are fixed to the rotating shaft 2 in a state where they are overlapped in the axial direction, and rotate integrally with the rotating shaft 2.

The Hall IC 5 is disposed in a synthetic magnetic field generated by the base magnet 3 and the auxiliary magnet 4. Specifically, it is placed closer to the outside in the radial direction than the outer peripheral edges of the base magnet 3 and the auxiliary magnet 4, and is arranged within the range of the axial thickness of the auxiliary magnet 4. The Hall IC 5 is mounted with two Hall elements (first Hall element 6 and second Hall element 7) that output an electrical signal (for example, a voltage signal) according to the magnetic flux density of the combined magnetic field.
The first Hall element 6 is arranged such that the magnetic sensitive surface for detecting magnetism faces the rotation axis 2 which is the rotation center of the base magnet 3 and the auxiliary magnet 4, and the second Hall element 7 is a magnetic sensitive element for detecting magnetism. The surface is disposed so as to face the direction perpendicular to the magnetic sensitive surface of the first Hall element 6. That is, the two Hall elements 6 and 7 are arranged in a positional relationship in which the two magnetic sensitive surfaces are orthogonal to each other.

Further, as shown in FIG. 3, the Hall IC 5 is amplified by a first amplifier circuit 8 that amplifies the output signal of the first Hall element 6 and a second amplifier circuit 9 that amplifies the output signal of the second Hall element 7. A / D conversion circuit 10 that converts two analog signals into digital signals, a signal processing circuit 11 that calculates a rotation angle based on the two A / D converted digital signals, and a digital value of the calculated rotation angle. A D / A conversion circuit 12 for converting to an analog value is mounted.
The signal processing circuit 11 is constituted by, for example, a known DSP (digital signal processor), and an offset correction circuit 11a that corrects an offset between two digitally converted output signals, a gain correction circuit 11b that corrects a gain, and An arithmetic circuit 11c for performing inverse trigonometric function calculation is included.

Next, the operation of the rotation angle detection device 1 according to this embodiment will be described.
When the base magnet 3 and the auxiliary magnet 4 rotate integrally with the rotating shaft 2, as shown in FIG. 4, a signal a corresponding to the magnetic flux density is output from the first Hall element 6, and the magnetic flux density is changed from the second Hall element 7. A corresponding signal b is output. After the two output signals are amplified and A / D converted, the offset and gain are adjusted, converted into linear characteristics by inverse trigonometric function calculation, and the rotation angle is calculated.
By the way, since the two Hall elements 6 and 7 are arranged in a positional relationship in which their magnetic sensing surfaces are orthogonal to each other, if there is no misalignment between the two Hall elements 6 and 7, The phase difference between the output and the output of the second Hall element 7 (hereinafter referred to as 2 outputs) is 90 °. However, as shown in FIG. 5, if the two Hall elements 6 and 7 are misaligned (shift angle α), the phase difference between the two outputs does not become 90 °, and as shown in FIG. A shift (shift in phase difference) occurs.

  Note that the graph shown in FIG. 6 shows an output signal (output a of the first Hall element 6, output b of the second Hall element 7) when the two Hall elements 6 and 7 are not misaligned, The output signals (the output a1 of the first Hall element 6 and the output b1 of the second Hall element 7) when the Hall elements 6 and 7 have a displacement of α = 5 ° are shown. When the two Hall elements 6 and 7 are not misaligned (α = 0 °), an angular error occurs with respect to the rotational angle positions of the base magnet 3 and the auxiliary magnet 4 as shown by the solid line X in FIG. However, when the two Hall elements 6 and 7 are misaligned (α = 5 °), as shown by the curve Y in FIG. Cause an angle error.

In order to eliminate this angular error, in this embodiment, as shown in FIG. 2, the rotational angle position of the auxiliary magnet 4 is shifted by a predetermined angle φ with respect to the base magnet 3 to correct the phase shift of two outputs. Yes. In other words, the rotation of the auxiliary magnet 4 with respect to the base magnet 3 is such that the phase shift between the two outputs caused by the displacement of the two Hall elements 6 and 7 is 0 ° (the phase difference between the two outputs is 90 °). The angular position is shifted by a predetermined angle φ.
When the positional deviation of the two Hall elements 6 and 7 is α = 5 ° and the relationship between the deviation angle φ of the auxiliary magnet 4 with respect to the base magnet 3 and the phase deviation of the two outputs is measured, the result shown in FIG. 8 is obtained. It is done.

That is, when the misalignment between the two Hall elements 6 and 7 is α = 5 °, the auxiliary magnet 4 is shifted by about 65 ° with respect to the base magnet 3, so that the phase shift between the two outputs becomes 0 °.
Actually, when the outputs of the two Hall elements 6 and 7 are measured with the rotational angle position of the auxiliary magnet 4 shifted by about 65 °, as shown in FIG. 9, before the auxiliary magnet 4 is shifted, that is, the base magnet. 3 and the auxiliary magnet 4 are different from the outputs of the two Hall elements 6 and 7 measured in the same rotational angle position (the state shown in FIG. 1B), the phase difference between the two outputs is 90 °. It has become.

(Effect of Example)
In the rotation angle detection device 1 of the present embodiment, the phase difference between the output of the first Hall element 6 and the output of the second Hall element 7 is 90 ° due to the displacement of the first Hall element 6 and the second Hall element 7. By shifting the rotational angle position of the auxiliary magnet 4 according to the phase shift when there is a shift, that is, when there is a phase shift of two outputs, the phase shift of the two outputs can be easily corrected and the angle error can be reduced. .
According to this method, it is not necessary to perform map correction in order to reduce the phase shift between the two outputs. Therefore, the physique of the Hall IC 5 is not increased and the cost is not increased, and it is necessary to output a correction value on the map. Therefore, the responsiveness is not deteriorated.
In this embodiment, since the first Hall element 6 and the second Hall element 7 are mounted on one Hall IC 5, the environmental conditions of the first Hall element 6 and the second Hall element 7 are substantially equal. is there. In other words, since a temperature difference hardly occurs between the first Hall element 6 and the second Hall element 7, a good and stable angle detection is possible.

FIG. 10 is a side view of the rotation angle detection device 1.
In the first embodiment, the base magnet 3 and the auxiliary magnet 4 are fixed to the rotary shaft 2 in the state where they are overlapped in the axial direction. However, as shown in FIG. The rotary shaft 2 may be fixed in a state having a predetermined gap X.
Also in this embodiment, as in the first embodiment, when there is a phase shift of two outputs, the phase shift of two outputs can be corrected by shifting the rotational angle position of the auxiliary magnet 4 according to the phase shift. it can.

(Modification)
In the first embodiment, the method of shifting the rotational angle position of the auxiliary magnet 7 with respect to the displacement of the two Hall elements 6 and 7 has been described. However, the base magnet 6 and the auxiliary magnet according to the phase shift of two outputs. The phase shift of the two outputs can be corrected by relatively shifting the rotation angle position with respect to 7 by a predetermined angle.

(A) The axial direction top view of a rotation angle detection apparatus, (b) It is a side view of the same apparatus (Example 1). (A) Side view of rotation angle detection device, (b) Plan view of auxiliary magnet and base magnet. It is a circuit block diagram of Hall IC. It is an output characteristic view of two Hall elements. It is a top view which shows the arrangement | positioning shift | offset | difference of two Hall elements. It is an output characteristic figure which shows the phase shift by the arrangement | positioning shift | offset | difference of two Hall elements. It is a measurement graph which shows the angle error by the arrangement | positioning shift | offset | difference of two Hall elements. It is a correlation diagram which shows the relationship between the shift | offset | difference angle of an auxiliary magnet, and the phase difference of 2 outputs. It is the output characteristic figure of two Hall elements which compared this plan and the conventional plan. (Example 2) which is a side view of a rotation angle detection apparatus. (A) The axial direction top view of a rotation angle detection apparatus, (b) It is a side view of the same apparatus (prior art). It is a top view which shows the arrangement | positioning shift | offset | difference of two Hall elements.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation angle detection apparatus 2 Rotating shaft 3 Base magnet (1st magnet)
4 Auxiliary magnet (second magnet)
5 Hall IC
6 1st Hall element (magnetic detection element)
7 Second Hall element (magnetic detection element)
11a Offset correction circuit (correction function)
11b Gain correction circuit (correction function)

Claims (6)

A magnet that is provided in a disk shape or a ring shape, is magnetized in the radial direction, and rotates integrally with a rotation shaft that is disposed at the center in the radial direction;
It has two magnetism detection elements that are arranged in the magnetic field generated by this magnet and detects magnetism, and based on the change in magnetism detected by these two magnetism detection elements, the rotation angle of the rotating shaft is detected A rotation angle detecting device for
The two magnetic detection elements are arranged in a positional relationship in which both magnetic detection surfaces are orthogonal to each other,
The magnet includes a first magnet and a second magnet, and the first magnet and the second magnet are arranged adjacent to each other in the axial direction of the rotating shaft or at a predetermined interval. In addition, the two magnetic detection elements can be obtained by relatively shifting a rotational angle position between the first magnet and the second magnet in accordance with a phase shift of outputs of the two magnetic detection elements. A rotation angle detecting device for correcting a phase shift of an output of an element. In the rotation angle detection device according to claim 1,
The rotation angle detection device according to claim 1, wherein the first magnet and the second magnet have the same shape and the same performance. In the rotation angle detection device according to claim 1 or 2,
Each of the two magnetic detection elements is a Hall element that outputs an electric signal corresponding to a magnetic flux density, and includes one Hall IC in which the two Hall elements are mounted in one chip. Rotation angle detection device. In the rotation angle detection device according to claim 3,
The Hall IC has a correction function capable of adjusting offsets and gains of outputs of the two Hall elements. In the rotation angle detection device according to claim 3 or 4,
The Hall IC is placed on the outer side in the radial direction from the outer peripheral edges of the first magnet and the second magnet, and the axial thickness range of the first magnet and the second magnet is combined. A rotation angle detection device, wherein the rotation angle detection device is disposed inside. In the rotation angle detection device according to claim 5,
The Hall IC is arranged on one side of two magnets within the axial thickness of the first magnet and the second magnet, and is installed within the range of the thickness of one of the magnets. A rotation angle detection device characterized by being provided.

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