JP2008020299A - Angle detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive angle detection device hardly influenced by fluctuation of a magnetic field, capable of detecting an accurate angle. <P>SOLUTION: This device is equipped with a rotating member 1 wherein a magnet 14 forming an N-pole domain N and a magnet 15 forming an S-pole domain S are arranged alternately around the rotation center C; a sensor element 2 arranged outward in the radial direction of the rotating member 1, for detecting the magnitude of each magnetic field component in at least two directions, relative to the magnetic field formed around the rotating member 1; and an operation means 4 for calculating a rotation angle of the rotating member 1 to the sensor element 2 based on a detection result by the sensor element 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotating member in which N-pole regions and S-pole regions are alternately arranged around the rotation center, a sensor element that detects a magnetic field formed around the rotating member, and a magnetic field detected by the sensor element. The present invention relates to an angle detection device including a calculation unit that calculates a rotation angle of the rotation member based on the calculation unit.

This type of angle detection device is characterized in that the rotation shaft member can pass through the rotation member, and is used for various applications such as a steering angle sensor of an automobile and a shift position sensor of a transmission. .
Conventionally, various devices of this type have been proposed. For example, Patent Document 1 discloses an angle detection device including a sensor element capable of detecting the intensity of a unidirectional component of a magnetic field such as a Hall element, and a rotating member provided with an N-pole region and an S-pole region. Yes.
In this angle detection device, a set of N-pole region and S-pole region is provided over a substantially entire circumference on a part of the outer periphery of the rotating member. In the initial position, the sensor element is set to be located at the center of the N-pole region or the S-pole region. Then, the rotation angle is detected based on a change in the intensity of the magnetic field component in one direction accompanying the displacement from the initial position when the rotating member rotates with respect to the sensor element.

Japanese Patent No. 2842482 ([Claim 1] and description, column 6, line 50 to column 7, line 18)

  In the angle detection device described in Patent Document 1, the rotation angle is detected based on the intensity of the magnetic field component in one direction. For this reason, for example, when the magnetic field strength changes due to temperature change or deterioration with time of the magnetic material, the change in the magnetic field strength cannot be corrected, or accurate correction is difficult. It may be difficult to detect the angle.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an angle detection device that is not easily affected by fluctuations in a magnetic field and can detect an accurate angle at a low cost. .

  A first characteristic configuration of the present invention is a rotating member in which a magnet that forms an N-pole region and a magnet that forms an S-pole region are alternately arranged around a rotation center, and are arranged outward in the radial direction of the rotating member. A sensor element that detects the magnitude of a magnetic field component in at least two directions with respect to a magnetic field formed around the rotating member, and calculates a rotation angle of the rotating member relative to the sensor element based on a detection result of the sensor element. It is in the point provided with the calculation means.

With this configuration, the sensor element detects the magnitude of the magnetic field component in at least two directions, and the calculation means calculates the rotation angle of the rotating member based on, for example, the ratio of the detection results of each direction component. For this reason, for example, even when the strength of the magnetic field changes due to temperature change or deterioration over time of the rotating member, the magnetic field strength of each direction component changes at substantially the same rate, and the detection result ratio hardly changes. The rotation angle can be prevented from fluctuating and an accurate angle can be detected.
Further, since the N-pole region and the S-pole region are formed with a simple configuration in which a magnet is disposed around the rotation center of the rotating member, the manufacturing cost can be reduced.

  The second characteristic configuration of the present invention is that the magnet forming the N-pole region and the magnet forming the S-pole region have a rectangular parallelepiped shape.

  With this configuration, for example, a magnet that forms the N-pole region and a magnet that forms the S-pole region can be obtained simply by cutting the base material of the block-shaped magnet into a rectangular parallelepiped shape. Since a complicated manufacturing process is not required when obtaining these magnets, it is possible to obtain magnets that are inexpensive and have good dimensional accuracy. As a result, an inexpensive and highly accurate angle detection device can be realized.

  According to a third characteristic configuration of the present invention, the N-pole region and the S-pole region are provided in a fan-shaped range centered on the rotation center, and the bisector of the central angle of the fan-shaped The magnet is arranged so that each of the N-pole region and the S-pole region is symmetrical.

When the N-pole region and the S-pole region are provided in a fan-shaped range centered on the rotation center and arranged so that the N-pole region and the S-pole region are symmetric with respect to the central angle of the fan-shaped, It has been found that the variation in the direction of the magnetic field when the distance from the rotating member varies is smaller than when the N pole region and the S pole region are arranged asymmetrically with respect to the segment.
For this reason, this configuration can reduce fluctuations in the direction of the magnetic field that occur when the radial distance between the rotating member and the sensor element fluctuates. Variations in results can be reduced.
Further, even when the rotation member and the sensor element are close to or separated from each other due to the shake of the rotation shaft when the angle detection device is used, fluctuations in the detection result can be reduced.

  According to a fourth characteristic configuration of the present application, a cylindrical yoke is extrapolated to the shaft portion of the rotating member, the magnet is disposed along an outer periphery of the yoke, and the yoke is formed by a resin portion integrally formed with the shaft portion. And the magnet is covered.

With this configuration, since the yoke and the magnet are covered with the resin portion integrally formed with the shaft portion of the rotating member, the magnet can be reliably fixed at an intended position. Further, since the shaft portion and the resin portion of the rotating member are integrally formed, the strength can be increased as compared with the case where the shaft portion and the resin portion are provided separately.
Further, since the magnets are arranged along the outer periphery of the yoke, the outward magnetic field in the radial direction of the rotating member can be strengthened by the shielding effect. For this reason, even when the magnet is covered with the resin portion, an intended magnetic field can be formed around the rotating member.

  A fifth characteristic configuration of the present invention is that the magnet has a rectangular parallelepiped shape, and a contact surface with which one side of the magnet contacts is provided at a position corresponding to the magnet on the outer periphery of the yoke.

With this configuration, the contact surface provided on the outer peripheral surface of the yoke comes into contact with one surface of the rectangular parallelepiped magnet. For this reason, the shielding effect by the yoke is enhanced, and the outward magnetic field in the radial direction of the rotating member can be strengthened.
In addition, positioning when placing the magnet on the outer periphery of the yoke is facilitated, and the N-pole region and the S-pole region can be placed accurately.

  A sixth characteristic configuration of the present invention is that a correction unit capable of correcting the magnitude of at least one of the magnetic field components detected by the sensor element is provided.

The angle detection apparatus according to the present invention detects the rotation angle based on the magnitude of the magnetic field component in two directions on the assumption that the shape of the magnetic field formed around the rotating member is an intended shape. Therefore, when the shape of the magnetic field is disturbed for some reason, it is difficult to accurately detect the rotation angle.
Therefore, as in the present configuration, a correction unit that can correct the magnitude of at least one of the magnetic field components can be provided. As a result, even when the shape of the magnetic field is disturbed, the corrector can detect the accurate rotation angle by correcting the magnitude of the magnetic field component.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, an angle detection device according to the present invention includes a rotating member 1 provided on a rotating shaft 31 that is a detection object 3 so as to be integrally rotatable, and an outer fixed side in the radial direction of the rotating member 1. The sensor element 2 fixed to the member 5 is provided.

The rotating member 1 includes a cylindrical yoke 12, a magnet 14 that forms an N-pole region N, and a magnet 15 that forms an S-pole region S. Magnets 14 and magnets 15 are alternately arranged along the outer peripheral surface of the yoke. Thereby, the N pole region N and the S pole region S are alternately formed around the rotation center C in the rotating member 1. Although the shape of the magnets 14 and 15 is not specifically limited, For example, the rectangular magnets 14 and 15 can be used.
The rotating member 1 also includes a shaft portion 16 for extrapolating the yoke 12 and a resin portion 13 that covers the yoke 12 and the magnets 14 and 15. The shaft portion 16 is provided with a hole portion 16a into which the rotating shaft 31 is inserted. The shaft portion 16 and the resin portion 13 are integrally provided by, for example, resin injection molding after the yoke 12 and the magnets 14 and 15 are arranged at predetermined positions in the mold.

  The sensor element 2 is composed of an element capable of detecting the direction and strength of the magnetic field from the rotating member 1 such as a Hall IC. Specifically, for example, a magnetic field detection element such as MLX90316 manufactured by Melexis is used. The magnetic field detection element detects magnetic field strengths in two orthogonal directions, and detects the direction of the magnetic field based on the ratio of the magnetic field strengths in the two directions. Since the direction of the magnetic field is detected based on the ratio of the magnetic field strengths in the two directions, the influence due to fluctuations in the magnetic field strength can be canceled.

When the rotating shaft 31 rotates, the rotating member 1 integrally fixed to the rotating shaft 31 also rotates in conjunction with it. When the rotating member 1 rotates, the relative positions in the circumferential direction of the N pole region N and S pole region S in the circumferential direction and the sensor element 2 change. For this reason, the direction of the magnetic field passing through the sensor element 2 changes periodically. Based on the detection result of the sensor element 2, the calculation means 4 calculates the rotation angle of the rotation shaft 31 that is the detected object 3 with respect to the fixed member 5.
Although not an essential component, the correction unit 7 may be provided so that the magnitude of at least one of the magnetic field components detected by the sensor element 2 can be corrected. In this case, the correction unit 7 may be one that gives the calculation unit 4 a correction function.

[Example 1]
FIG. 2 is a view showing an example of the rotating member 1 according to the present invention.
In the rotating member 1, a rectangular parallelepiped magnet 14 forming the N pole region N and a rectangular parallelepiped magnet 15 forming the S pole region S are alternately arranged around the rotation center C at a predetermined arrangement pitch α. is there. In FIG. 2, α = 45 °, and a total of three magnets, one magnet 14 and two magnets 15, are arranged.
Further, the N-pole region N and the S-pole with respect to the bisector CM having a fan-shaped central angle connecting the rotation center C and both ends in the circumferential direction where the N-pole region N and the S-pole region S are provided. Magnets 14 and 15 are arranged so that region S is symmetric. That is, one magnet (magnet 14 in this embodiment) is arranged at a position that is bisected by the bisector CM, and the other magnet (magnet 15 in this embodiment) is the bisector. They are arranged at positions that are symmetrical with respect to the CM. A cylindrical yoke 12 formed of a soft magnetic material is disposed on the inner circumference of the magnets 14 and 15. A sensor element 2 is disposed on the outer circumference side of the rotating member 1. The rotation angle of the rotating member 1 from the initial position is detected with the position where the line segment connecting the sensor element 2 and the rotation center C coincides with the bisector CM as the initial position of the rotating member 1.

FIG. 3 is a graph showing the relationship between the rotation angle when the rotary member 1 shown in FIG. 2 is rotationally displaced and the output of the sensor element 2 (that is, the direction of the magnetic field applied to the sensor element 2).
FIG. 4 shows a rotating member 100 used as a comparative example. The rotating member 100 is provided with an N-pole region N and an S-pole region S by magnetizing a ring-shaped magnetic body. N-pole regions N and S-pole regions S are alternately arranged around the rotation center C at a pitch α = 45 °, and four N-pole regions N and four S-pole regions S are provided.
FIG. 5 is a graph showing the relationship between the rotation angle when the rotary member shown in FIG. 4 is rotationally displaced and the output of the sensor element 2 (that is, the direction of the magnetic field applied to the sensor element 2).

When the result when the rotating member 1 is used (FIG. 3) is compared with the result when the rotating member 100 is used (FIG. 5), the case where the rotating member 100 is used even when the rotating member 1 is used. Equivalent linearity was obtained.
Further, even when the distance from the outer peripheral surface of the rotating member 1 to the sensor element 2 is changed, the relationship between the rotation angle of the rotating member 1 and the output of the sensor element 2 is the same as when the rotating member 100 is used. Changed little.
As described above, even in the rotating member 1 in which the three pole-shaped magnets are arranged to form the N-pole region N and the S-pole region S, the ring-shaped magnetic body is magnetized over the entire circumference, and N A characteristic equivalent to that of the rotating member 100 in which the polar region N and the S polar region S were formed was obtained.

When manufacturing the rotary member 100 having a ring-shaped magnet, the manufacturing cost increases because the volume of the necessary magnetic material increases and the magnetic material needs to be processed into a ring shape.
However, as described above, even with the rotating member 1 of the present invention, since the same characteristics as the rotating member 100 can be obtained, three rectangular magnets are arranged so that the N-pole region N and the S-pole region S are arranged. The rotary member 1 can be obtained with a simple configuration that is simply formed. For this reason, the angle detection apparatus which can detect a rotation angle correctly at low cost can be obtained.

[Example 2]
6 and 7 are diagrams illustrating another arrangement example of the N-pole region N and the S-pole region S. FIG.
In the rotating member 1 shown in FIG. 6, a rectangular parallelepiped magnet 14 forming the N pole region N and a rectangular parallelepiped magnet 15 forming the S pole region S are alternately arranged around the rotation center C at a pitch α = 45 °. It is arranged in. Here, one magnet 14 and two magnets 15 are arranged. Further, a magnet 14 having a half size in the circumferential direction is arranged adjacent to each magnet 15. Thus, the N pole region N and the S pole region S are arranged so as to be symmetric with respect to the bisector CM over the 180 ° range of the rotating member.

  In the rotating member 1 shown in FIG. 7, the magnets 14 and the magnets 15 are alternately arranged around the rotation center C at an arrangement pitch α = 45 °. A total of four magnets with two magnets 14 and two magnets 15 are arranged. As described above, the N-pole region N and the S-pole region S are arranged so as to be asymmetric with respect to the bisector CM over the 180 ° range of the rotating member 1.

FIG. 8 is a graph showing the amount of change in the direction of the magnetic field at each position in the circumferential direction of the rotating member 1 when the radial distance G from the rotating member 1 shown in FIG. 6 changes. FIG. 9 is a graph showing the amount of change in the direction of the magnetic field at each position in the circumferential direction of the rotating member 1 when the radial distance G from the rotating member 1 shown in FIG. 7 changes.
Position after movement with respect to the direction of the magnetic field at the reference position when moving (adjacent or separated) in the radial direction from a position where the distance from the outer peripheral surface of the rotating member 1 is 5 mm (hereinafter referred to as “reference position”) Fluctuations in the direction of the magnetic field in the were calculated by simulation using the finite element method.

  Comparing both simulation results, the N pole region N and the S pole region S moved in the radial direction from the reference position when arranged so as to be symmetric with respect to the bisector CM. It was found that the amount of fluctuation in the direction of the magnetic field was small.

Therefore, although not particularly limited, it is preferable that the rotating member 1 is arranged so that each of the N-pole region N and the S-pole region S is symmetric with respect to the bisector CM.
In this way, it is possible to reduce the variation in the direction of the magnetic field that occurs when the radial distance G between the rotating member 1 and the sensor element 2 varies. For this reason, the fluctuation | variation of the detection result by the influence of the assembly | attachment error of an angle detection apparatus can be reduced.
Further, even when the distance G in the radial direction between the rotating member 1 and the sensor element 2 varies due to the shake of the rotating shaft when the angle detection device is used, fluctuations in the detection result can be reduced.

[Example 3]
FIG. 10 is a graph showing the linearity at each rotation angle of the graph (FIG. 2) showing the relationship between the rotation angle of the rotating member 1 and the direction of the magnetic field at each rotation angle.
As a reference for linearity, a% FS value indicating a difference between an ideal straight line when a relation between a rotation angle of the rotating member 1 and a magnetic field direction at each rotation angle is linearly approximated and an actual relation is used. As shown in FIG. 10, the% FS value was a waveform for two periods in the range of −45 ° to 45 °, and the amplitude was about 2.0% FS.

By the way, the sensor element 2 detects, for example, the strength of magnetic fields in two orthogonal directions (that is, the magnetic field strength Br in the r direction and the magnetic field strength Bθ in the θ direction), and is based on, for example, the ratio of the magnetic field strength Br and the magnetic field strength Bθ. (For example, by calculating tan ⁻¹ (Bθ / Br)), the rotation angle is calculated.
For this reason, one of the causes that the relationship between the rotation angle of the rotating member 1 and the direction of the magnetic field at each rotation angle is not completely linear is that the amplitude of the magnetic field strength Br and the amplitude of the magnetic field strength Bθ are different. It is believed that there is.

FIG. 11 is a graph showing the r-direction magnetic field strength Br and the θ-direction magnetic field strength Bθ at each circumferential position of the rotating member 1 shown in FIG. 2 with the angle at the position of the sensor element 2 being 0 °. As is apparent from this graph, the amplitude of the magnetic field strength Br is larger than the amplitude of the magnetic field strength Bθ, and the amplitude of the magnetic field strength Br is about 1.3 times the amplitude of the magnetic field strength Bθ.
Therefore, the rotation angle was calculated after correcting the magnetic field intensity Bθ by 1.3 so that the amplitude of the magnetic field intensity Br and the amplitude of the magnetic field intensity Bθ were substantially the same. FIG. 12 is a graph showing the linearity of the relationship between the corrected rotation angle of the rotating member 1 and the direction of the magnetic field at each rotation angle. As shown in FIG. 12, the% FS value was a waveform for one cycle in the range of −45 ° to 45 °, and the amplitude was about 1.0% FS. Thus, the linearity was improved by correcting the magnetic field strength and making the amplitude magnitude of the magnetic field strength in two directions equal.
Therefore, the angle detection apparatus includes the correction unit 7, and the correction unit corrects the magnetic field strength so that the amplitude of the magnetic field strength Br and the amplitude of the magnetic field strength Bθ are substantially the same, thereby more accurately rotating the rotation angle. Can be detected.
In order to detect the rotation angle more accurately, the detection angle range is divided into predetermined intervals in the relationship between the corrected rotation angle and the direction of the magnetic field at each rotation angle, and the inclination is determined for each interval. A calibration curve may be obtained by determining offset values and regarding each section as a straight line.
By using the relationship between the rotation angle after correction and the direction of the magnetic field at each rotation angle, the linearity is improved as compared with that before correction, and therefore the number of divisions can be reduced.

[Another embodiment]
FIG. 13 shows a rotating member 1 according to another embodiment. In the rotating member 1, a contact surface 12 a with which one surface of the rectangular parallelepiped magnets 14 and 15 contacts is provided at a position corresponding to the magnets 14 and 15 on the outer periphery of the yoke 12.
By providing the contact surface 12a in this manner, the adhesion between the contact surface 12a provided on the outer peripheral surface of the yoke 12 and the rectangular parallelepiped magnets 14 and 15 is improved. For this reason, the shielding effect by the yoke 12 is enhanced, and the magnetic field strength in the radial direction of the rotating member 1 is increased. Further, positioning when arranging the magnets 14 and 15 on the outer periphery of the yoke 12 becomes easy, and the N-pole region and the S-pole region can be arranged at appropriate positions.

The figure which shows an example of the angle detection apparatus which concerns on this invention The figure which shows an example of the rotating member which concerns on this invention The graph of the relationship between the rotation angle of the rotation member of FIG. 2, and the output of a sensor element The figure which shows the rotating member of a comparative example The graph of the relationship between the rotation angle of the rotation member of FIG. 4, and the output of a sensor element The figure which shows an example of a rotation member The figure which shows an example of a rotation member The graph of the simulation result when the radial position is changed in FIG. The graph of the simulation result when the radial position is changed in FIG. The figure which shows the magnetic field intensity of 2 directions in each position of a rotating member Graph showing the linearity of the relationship between rotation angle before correction and sensor element output Graph showing the linearity of the relationship between the corrected rotation angle and sensor element output The figure which shows the rotating member which concerns on another embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating member 2 Sensor element 4 Calculation means 7 Correction means 12 Yoke 12a Contact surface 13 Resin part 14 Magnet 15 Magnet 16 Shaft part C Rotation center N N pole area S S pole area CM Bisecting line

Claims (6)

A rotating member in which a magnet that forms an N-pole region and a magnet that forms an S-pole region are alternately arranged around a rotation center;
A sensor element that is disposed outward in the radial direction of the rotating member and detects the magnitude of a magnetic field component in at least two directions with respect to a magnetic field formed around the rotating member;
An angle detection apparatus comprising: a calculation unit that calculates a rotation angle of the rotation member with respect to the sensor element based on a detection result of the sensor element.   The angle detection device according to claim 1, wherein the magnet forming the N-pole region and the magnet forming the S-pole region have a rectangular parallelepiped shape.   The N-pole region and the S-pole region are provided in a fan-shaped range centered on the rotation center, and the N-pole region and the S-pole region are in relation to the bisector of the central angle of the fan-shape. The angle detection device according to claim 1 or 2, wherein the magnets are arranged so as to be symmetrical with each other.   A cylindrical yoke is extrapolated to the shaft portion of the rotating member, the magnet is disposed along the outer periphery of the yoke, and the yoke and the magnet are covered with a resin portion formed integrally with the shaft portion. The angle detection device according to any one of Items 1 to 3.   The angle detection device according to claim 4, wherein the magnet has a rectangular parallelepiped shape, and a contact surface with which one side of the magnet contacts is provided at a position corresponding to the magnet on an outer periphery of the yoke.   The angle detection device according to any one of claims 1 to 5, further comprising a correction unit capable of correcting a magnitude of at least one of the magnetic field components detected by the sensor element.