JP2003240602A - Rotation angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle sensor capable of reducing an angle error caused by shaft displacement. <P>SOLUTION: A magnet 300 formed in a discoid shape is supported by a rotation shaft 303 and rotated in the circumferential direction around a rotation center line Z<SB>1</SB>together with the rotation shaft 303. Magnetic sensors A<SB>1</SB>, A<SB>2</SB>and B<SB>1</SB>, B<SB>2</SB>arranged near the circumference of the magnet 300 are fixed on a plane P parallel to a discoid face of the magnet 300. One pair of the magnetic sensors A<SB>1</SB>, A<SB>2</SB>are arranged symmetrically with respect to a reference point O on the plane P, and the other pair of the magnetic sensors B<SB>1</SB>, B<SB>2</SB>are arranged symmetrically with respect to the reference point O. The distance m from the reference point O approximately agreeing with an intersection point of the plane P with the rotation center line Z<SB>1</SB>of the magnet 300 to the center of each magnetic sensor is different from the radius r of the magnet 300. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle sensor, and more particularly, to a rotation angle sensor which detects a non-contact angle using a plurality of magnetic sensors.

[0002]

2. Description of the Related Art Conventionally, as a rotation angle sensor of this type, a rotating body having magnets of N and S poles forming a magnetic circuit and a magnetic sensor for detecting magnetic strength are combined to form a rotary angle sensor. There are many structures that detect a rotation angle by rotating a body with respect to a magnetic sensor, and are used in various fields such as an automobile engine and a DC motor. In particular, a non-contact rotation angle sensor is known that uses a Hall element as a magnetic sensor, and by combining this with a highly accurate magnetic circuit, it is possible to output an analog signal for the rotation angle of a rotating body. There is.
For example, documents such as Japanese Patent Laid-Open Nos. 11-295022 and 8-35809 disclose such a rotation angle sensor.

FIG. 1 is a view conceptually showing an external structure of a conventional rotation angle sensor. (A) is a bottom view and (b) is FIG.
It is the side view shown from the arrow W direction of (a). In this figure, magnetic sensors A ₁ and B ₁ detect a magnetic field,
It is a Hall element that outputs a value according to the strength of the magnetic field, and both have the same temperature characteristics. In addition, the magnetic sensor A
₁ and B ₁ are arranged on the plane P.

The reference point O on this plane P and the magnetic sensor A ₁
The angle formed by the straight line 101 passing through the substantial center of the line and the straight line 102 passing through the reference point O and the approximate center of the magnetic sensor B ₁ is approximately 90 degrees.

The disk-shaped magnet 100 has a rotating shaft 1
03, and a rotation center line Z ₁ perpendicular to the plane P
Is configured to be rotatable in the circumferential direction, that is, in the direction indicated by the white arrow. In an ideal state, the reference point O
Exists on the rotation center line Z ₁ .

Thus, by calculating the angle from the output values of the two magnetic sensors, it is possible to compensate for the influence of the temperature characteristic.

Further, the conventional rotation using four magnetic sensors
2 (a) and 2 (b) showing an example of the configuration of the angle sensor.
If the magnetic sensor A₁And A_Two, Magnetic sensor B₁And
And B _TwoAre arranged immediately below the circumference of the magnet 200.

As shown in FIG. 3, the output value V from the magnetic sensors A ₁ , A ₂ , B ₁ and B ₂ in the rotation angle sensor shown in FIG.
Negative values are output on the pole side. Further, the absolute value of the output value V becomes larger as the magnetic flux density becomes higher.

Now, in the example shown in FIG. 2, the output values from the magnetic sensors A ₁ , A ₂ , B ₁ and B ₂ are set to V.
₁ (A ₁ ), V ₁ (A ₂ ), V ₁ (B ₁ ), V
_When expressed by ₁ (B ₂ ), the rotation angle θ ₁ of the magnet 300 from the predetermined reference position of the magnet is

[0010]

[Equation 1]

It can be obtained by Here, since the magnetic sensor is arranged as shown in FIG.
There is a relationship of ₁ (A ₁ )> 0 and V ₁ (A ₂ ) <0.

[0012]

However, in the conventional rotation angle sensor as described above, the magnetic sensor is installed at the peripheral edge of the magnet, where the magnetic field strength generated by the disk-shaped magnet of the rotation angle sensor is the strongest. . Therefore, when stress in the radial direction of the magnet is applied to the rotation axis of the magnet, the displacement of the rotation center line Z ₁ of the magnet with respect to the reference point O of the arrangement of the magnetic sensor (hereinafter referred to as “axis deviation”) causes An angle error will occur.

For example, in the case of the rotation angle sensor shown in FIG. 2, the output values V ₂ (A ₁ ), V ₂ (A ₂ ), V ₂ (B) from the respective Hall elements are caused by the axis shift in the arrow X direction.
₁ ) and V ₂ (B ₂ ) change as follows.

[0014]

[Equation 2]

Here, ΔV (A ₁ ), ΔV (A ₂ ), Δ
Let V (B ₁ ), ΔV (B ₂ )> 0. When the movement amount (axis deviation amount) of the rotation center line of the magnet is sufficiently smaller than the diameter of the magnet, the following relationship holds.

[0016]

[Equation 3]

Therefore, the measurement angle θ when the axis shift occurs
₂ is

[Equation 4] Therefore, the measurement angle changes due to the axis deviation. Therefore, there is a problem in that highly accurate alignment is required such that lateral stress does not occur on the rotation shaft when the rotation angle sensor is attached.

For the same reason, it is necessary to limit the use of the rotation angle sensor such that no lateral stress is generated on the rotation axis after the rotation angle sensor is attached. Therefore, there is a problem in that it is difficult to design the entire machine using the rotation angle sensor, for example, when the temperature change in the use environment is large, stress due to the difference in thermal expansion coefficient is not generated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotation angle sensor capable of reducing an angular error due to an axis deviation.

[0020]

In order to achieve such an object, the invention described in claim 1 is a disk-shaped magnet, which rotates in the circumferential direction of the disk, and a magnetic field. A rotation angle sensor comprising at least one pair of magnetic sensors for detecting strength and outputting a value according to a rotation angle of the magnet, wherein the at least one pair of magnetic sensors is a disc of the magnet. Located on a plane parallel to the plane, at a symmetrical position from a reference point that substantially coincides with the intersection of the plane and the rotation center line of the magnet, and the distance from the reference point to the center of the magnetic sensor is It is different from the radius of the magnet.

The invention described in claim 2 is the same as claim 1
The rotation angle sensor according to claim 1, wherein the magnetic sensor includes a first pair and a second pair, and a straight line passing through a center of each of the magnetic sensors included in the first pair and a second pair included in the second pair. The angle formed by the straight line passing through the center of each magnetic sensor is 30 degrees or more and 150 degrees or less.

The invention described in claim 3 is the same as claim 1
Alternatively, in the rotation angle sensor according to the second aspect, the magnetic sensor is arranged within a range in which a magnetic flux density detectable by the magnetic sensor changes linearly with respect to a radial displacement of the magnet. And

Further, the invention according to claim 4 is the rotation angle sensor according to any one of claims 1 to 3, wherein the magnetic sensor is sealed in a container which can be surface-mounted on a mounting surface on which the magnetic sensor is mounted. It is characterized by being stopped.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. In addition, in the present specification, the “magnetism-sensitive surface” refers to a surface capable of detecting magnetism in the magnetic sensor. The "center of the magnetic sensor" means the center of the magnetically sensitive surface of the magnetic sensor.

(First Embodiment) FIG. 4 is a view conceptually showing the external structure of a rotation angle sensor according to the present embodiment.
4A is a bottom view, and FIG. 4B is a side view shown in the arrow W direction in FIG.

In this figure, the magnet 3 is formed in a disk shape.
00 is supported by the rotary shaft 303, and the rotary shaft 3
It is configured to be rotatable in the circumferential direction, that is, in the direction indicated by the white arrow around the rotation center line Z ₁ together with 03.

The magnetic sensors A ₁ , A ₂ , B ₁ and B ₂ arranged near the circumference of the magnet 300 detect the strength of the magnetic field and output a value corresponding to the strength of the magnetic field. They are elements and have the same temperature characteristics. These plural magnetic sensors are fixed on a plane P parallel to the disc surface of the magnet 300. The plane P is virtual, and the mounting surface of the magnetic sensor itself does not necessarily have to be a plane.

More specifically, the distance m from the reference point O to the center of each magnetic sensor is different from the radius r of the magnet 300. Here, the reference point O is the magnetic sensor A forming a pair.
It is the intersection of a straight line 301 connecting the centers of ₁ and A ₂ and a straight line 302 connecting the centers of the magnetic sensors B ₁ and B ₂ forming another pair. Therefore, the reference point O is uniquely determined from the position of the magnetic sensor and does not change even if the axis is deviated. In the ideal configuration, the perpendicular line of the plane P passing through the reference point O coincides with the rotation center line Z ₁ .

A major feature of the present invention is that the distance m is different from the radius r of the magnet 300. In this embodiment, the relationship of m <r is satisfied for all the magnetic sensors.

Among these magnetic sensors, a pair of magnetic sensors A ₁ and A ₂ are symmetrically arranged at a reference point O on a plane P, and another pair of magnetic sensors B ₁ and B ₂ is a reference point. It is arranged symmetrically to O. The angle formed by the straight line 301 and the straight line 302 is approximately 90 degrees.

The output value V from the Hall element constituting each magnetic sensor satisfies the relationship shown in FIG. 3, and a positive value is output on the N pole side and a negative value is output on the S pole side. . Further, the absolute value of the output value V becomes larger as the magnetic flux density becomes higher.

Now, the magnetic sensor A₁And A_TwoNavi
To B₁And B_TwoOutput value from V ₁(A₁), V
₁(A_Two), V₁(B₁), V₁(B_Two)
Rotation angle θ of the magnet 300 from the predetermined reference position of the stone₁Is

[0033]

[Equation 5]

It can be obtained by Here, since the magnetic sensor is arranged as shown in FIG.
There is a relationship of ₁ (A ₁ )> 0 and V ₁ (A ₂ ) <0.

As shown in FIG. 5, when the center of rotation of the magnet 300 is displaced in the radial direction of the magnet indicated by the arrow X and the original Z ₁ is moved to Z ₂ while maintaining the arrangement of the magnetic sensors. think of. The output from each Hall element due to this axis shift changes as follows.

[0036]

[Equation 6]

Here, ΔV (A ₁ ), ΔV (A ₂ ), Δ
Let V (B ₁ ), ΔV (B ₂ )> 0. When the magnet movement amount (axis deviation amount) is sufficiently smaller than the magnet diameter,
The following relationship holds.

[0038]

[Equation 7]

Therefore, the measured angle θ when the axis shift occurs
₂ is

[0040]

[Equation 8]

Therefore, the influence of the axis deviation does not appear in the measurement angle.

The effect of this embodiment is as shown in FIG.
And it can be explained as follows using FIG. FIG. 6 is a graph showing the magnetic field distribution generated by the magnet 300 on the plane P. The horizontal axis indicates the distance (mm) from the reference point O on the plane P of the magnet 300 in the X direction, and the vertical axis indicates the Z axis direction. The magnetic flux density Bz (mT) of is shown. Further, FIG. 7 is an enlarged view near the maximum value of the magnetic flux density Bz shown in FIG. 6, where (a) is an N pole side and (b) is an S pole side.

Attention is now paid to the pair of magnetic sensors A ₁ and A ₂ which are symmetrically arranged with respect to the reference point O. In the initial state, the magnetic sensor A ₁ is located at the position x ₁₁ and the magnetic sensor A ₂ is located at the position x ₂₁ in FIG. 7. The magnetic flux density at the position x ₁₁ is y ₁₁ , and the magnetic flux density at the position x ₂₁ is y ₂₁ . In this state, the difference V ₁ (A ₁ ) − between the output values from the magnetic sensors A ₁ and A ₂
V ₁ (A ₂ ) has a value proportional to the difference y ₁₁ −y ₂₁ of the magnetic flux densities.

Here, displacement of the magnet in the radial direction occurs in the rotation angle sensor, and as shown in FIG. 7, the position of the magnetic sensor A ₁ in the magnetic field is x ₁₂ , and the position of the magnetic sensor A ₂ is x.
_Suppose it changed to ₂₂ . The magnetic flux density at the position x ₁₂ is y ₁₂ , and the magnetic flux density at the position x ₂₂ is y ₂₂ .
Therefore, the difference V ₂ (A ₁ ) −V ₂ (A ₂ ) between the output values from the magnetic sensors A ₁ and A ₂ is the difference y ₁₂ between the magnetic flux densities.
It becomes a value proportional to -y _22.

In the example shown in FIG. 7, positions x ₁₁ to x
The magnetic flux density up to ₁₂ and the magnetic flux density between positions x ₂₁ and x ₂₂ are changing on a straight line having almost the same slope. In this case, the difference y ₁₂ -y _{22 in} the magnetic flux density after the axis deviation is the difference y ₁₁ -y before the axis deviation.
_It is almost equal to ₂₁ . Similarly, V ₂ (A ₁ ) -V
_{2 (A 2)} is also _{V 1 (A 1)} is substantially equal to -V 1 _{(A 2).} Therefore, Z that can be detected by the magnetic sensor
Within the range in which the magnetic flux density in the axial direction changes substantially linearly with respect to the displacement of the magnet 300 in the radius r direction, the magnetic sensor A ₁ ,
When A ₂ , B ₁ and B ₂ are arranged, the angle error of the measurement angle can be reduced more effectively.

FIG. 8 shows one of the magnetic sensors shown in FIG.
It is a side surface perspective view of the mounted package (container). Magnetic
Sensor A₁Is sealed in the package 700,
Center of rotation Z₁Surface-mounted on the mounting surface 703 perpendicular to the
Has been. Therefore, the normal 704 of the magnetic sensitive surface 702
It becomes perpendicular to the contact surface 703. In addition, the magnetic sensor A ₁
Is connected to an external circuit through the lead frame 701.
Be done.

As described above, by sealing the magnetic sensor in the surface mountable package on the mounting surface, high reproducibility of assembly and mechanical stability can be obtained in designing the rotation angle sensor.

Examples of the present invention will be described below.

[0049]

EXAMPLES Example 1 The conventional rotation angle sensor shown in FIG. 2 and the rotation angle sensor according to the above embodiment shown in FIG. 3 were manufactured. For these rotation angle sensors, a magnet has a diameter R = 10 mm and a neodymium magnet with a thickness of 3 mmt. The enclosed Hall element was used together. Further, the distance between the magnetic sensor and the magnet was set to 0.5 mm.

Now, as shown in FIG. 9, from the radius r of the magnet 300 of the rotation angle sensor and the rotation center line Z ₁ of the magnet 300 arranged in an ideal state to the center of the magnetic sensor on the mounting surface 802. The difference n from the distance m is defined as the arrangement position of the magnetic sensor. The arrangement position n of the magnetic sensor in the conventional rotation angle sensor is 0 μm. On the other hand, the arrangement position of the magnetic sensor in the rotation angle sensor according to the present embodiment is set to 600 μm.

With respect to the two rotation angle sensors thus constructed, the amount of axis deviation L was changed in the range of 0 mm to 0.30 mm, and the angle error of the measurement angle was measured.

Here, the definition of the angular error will be described with reference to FIG. FIG. 10 is a graph showing the ideal value of the measurement angle, the actual measurement angle by the rotation angle sensor, and the angle error. The horizontal axis represents the rotation angle and the vertical axis represents the measurement angle. When the magnets are ideally arranged in the rotation angle sensor, that is, when the reference point O on the plane and the rotation center line Z ₁ of the cylindrical magnet coincide with each other, the measurement is performed based on the output from the magnetic sensor. The measurement angle is equal to the rotation angle, and the broken line 90
The value shown in 2 (ideal value) is obtained. However, as shown in FIG. 5B, when the rotation center line of the magnet moves from Z ₁ to Z ₂ due to the axis shift, the measurement angle becomes the value shown by the curve 906. The angular error is represented as the width 904 tangent to the curve 906 and between two tangents 908 and 910 parallel to the dashed line 902.

Table 1 below shows the measurement results of the angular error with respect to the axis deviation amount L.

[0054]

[Table 1]

As is clear from Table 1, the rotation angle sensor according to the present embodiment has a smaller angle error of the measurement angle due to the axis deviation than the conventional example.

(Embodiment 2) As in Embodiment 1, FIG.
The rotation angle sensor of the conventional example shown in FIG. 4 and the rotation angle sensor according to the above-described embodiment shown in FIG. 4 were manufactured. These rotation angle sensors have a magnet with a diameter R = 10 mm and a thickness of 3
The size of the neodymium magnet of mmt and the magnetic sensor is 1.5.
A Hall element encapsulated in a resin package having a size of mm × 1.5 mm and a thickness of 0.6 mm (excluding leads) was used together.
Further, the distance between the magnetic sensor and the magnet was set to 0.5 mm.

With respect to the rotation angle sensor thus configured, the magnetic sensor arrangement position n is 200 μm to 800 μm.
When the angle error was measured when the amount of misalignment L was changed to 0.1 mm by changing the value in the range of m, the values shown in the following table were obtained.

[0058]

[Table 2]

As is clear from Table 2 above, the angle error of the measured angle of the rotation angle sensor according to this embodiment is smaller than that of the conventional example.

Further, the axis deviation amount L is from 0 mm to 0.3 mm.
When the angular error was measured in steps of 0.05 mm in the ranges up to, the values shown in Table 3 below were obtained.

[0061]

[Table 3]

For example, when the axial deviation L is 0.1 mm, the rotation angle sensor having the arrangement position of 500 μm has a smaller angular error than the rotation angle sensor having the arrangement position of 600 μm. However, when the axial deviation L is 0.3 mm, the arrangement position is 600
The angle error of the rotation angle sensor of μm is smaller than that of the rotation angle sensor of 500 μm. Thus, it can be seen that there is a width in the optimum magnetic sensor arrangement position for reducing the angle error.

Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiments and can be implemented in various other forms. For example,
As a magnetic sensor forming an angle measuring system to which the present invention is applied, in addition to a Hall element, an MR (Magnetic Resis
tance) element, MI (Magnetic Impedance) element, and flux gate can be used.

In the above embodiment, the angle formed by the straight line passing through the centers of the pair of magnetic sensors and the straight line passing through the centers of the other pair of magnetic sensors is approximately 90 degrees. I explained about this, but this angle is 30 degrees or more 1
If it is within the range of 50 degrees or less, it can be put to practical use.

Further, in the above-described embodiment, an example in which the distance between the reference point and the magnetic sensor is shorter than the radius of the magnet has been described. On the contrary, the distance between the reference point and the magnetic sensor is shorter than the radius of the magnet. May be longer. Also in this case, similarly to the above-described embodiment, each magnetic sensor is arranged within a range in which the magnetic flux density in the direction detectable by the magnetic sensor generated by the magnet changes substantially linearly with respect to the radial displacement of the magnet. Preferably.

When there are a plurality of pairs of magnetic sensors, the distance from the reference point to the magnetic sensors may be different for each pair.

In the above embodiment, an example using two pairs of magnetic sensors has been described, but it goes without saying that the effects of the present invention can be obtained by using at least one pair of magnetic sensors.

Further, in the above-mentioned embodiment, the case where the magnetic sensitive surface of the magnetic sensor is perpendicular to the rotation center line of the magnet has been described as an example, but the magnetic sensitive surface keeps a constant angle with respect to the rotation center line. All magnetic sensors may be arranged as described above.

Further, in the above-mentioned embodiment, an example in which one magnetic sensor is arranged at one place has been described, but a plurality of magnetic sensors may be arranged at one place. In this case, a more accurate output value can be obtained by averaging the output values from the plurality of magnetic sensors to obtain the output value at that position.

[0070]

As described above, according to the present invention,
At least one pair of magnetic sensors are arranged on a plane parallel to the disc surface of the magnet, symmetrically with respect to a reference point substantially coincident with the intersection of the plane and the rotation center line of the magnet. Since the distance to the center of the magnetic sensor is different from the radius of the magnet, it is possible to realize a rotation angle sensor with a small angle error due to axis deviation.

The magnetic sensor comprises a first pair and a second pair, and a straight line passing through the center of each of the magnetic sensors included in the first pair and each of the magnetic sensors included in the second pair. Since the angle formed by the straight line passing through the center is 30 degrees or more and 150 degrees or less, compensation can be performed for the measured rotation angle in consideration of the temperature characteristics.

Further, since the plurality of magnetic sensors are arranged within the range in which the magnetic flux density detectable by the magnetic sensors changes linearly with respect to the radial displacement of the magnet, the angular error due to the axis deviation is eliminated. It can be reduced more effectively.

Furthermore, since the magnetic sensor is sealed in a container that can be surface-mounted on the mounting surface on which the magnetic sensor is mounted, a magnetic sensor having a smaller overall size can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing an external configuration of a conventional rotation angle sensor.

FIG. 2 is a diagram conceptually showing an external configuration of a conventional rotation angle sensor.

FIG. 3 is a diagram conceptually showing an output value from a magnetic sensor in a conventional rotation angle sensor.

FIG. 4 is a diagram conceptually showing an external configuration of a rotation angle sensor according to an embodiment of the present invention.

FIG. 5 is a diagram showing a configuration in the case where an axis deviation occurs in the rotation angle sensor according to the embodiment of the present invention.

FIG. 6 is a graph showing a magnetic field distribution generated by a magnet.

7A and 7B are enlarged views in the vicinity of the maximum value of the magnetic flux density Bz shown in FIG. 6, where FIG. 7A is an N-pole side and FIG. 7B is an S-pole side enlarged view.

FIG. 8 is a side perspective view of a package in which one of the magnetic sensors shown in FIG. 4 is mounted.

FIG. 9 is a diagram showing the definition of the arrangement position of the magnetic sensor.

FIG. 10 is a graph showing an ideal value of a measurement angle, an actual measurement angle by a rotation angle sensor, and an angle error.

[Explanation of symbols]

100, 200, 300 Magnet 101, 102, 201, 202, 301, 302 Straight line 103, 203, 303 Rotating shaft 701 Lead frame 702 Magnetically sensitive surface 703, 802 Mounting surface 704 Normal line A ₁ , A ₂ , B ₁ , B ₂ magnetic sensor O reference point P plane Z ₁ , Z ₂ magnet rotation center line

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masanobu Sato             3050 Okada, Atsugi City, Kanagawa Prefecture Asahi Kasei Corporation             In the company F term (reference) 2F077 AA47 CC02 NN04 NN17 PP12                       QQ05 QQ06 RR03 UU10 VV02                       VV21

Claims (4)

[Claims] 1. A disk-shaped magnet that rotates in the circumferential direction of the disk, and at least one pair of magnets that detect the strength of a magnetic field and output a value according to the rotation angle of the magnet. A rotation angle sensor comprising a magnetic sensor, wherein the at least one pair of magnetic sensors is substantially coincident with an intersection of the plane and a rotation center line of the magnet on a plane parallel to the disc surface of the magnet. The rotation angle sensor is arranged symmetrically with respect to the reference point, and the distance from the reference point to the center of the magnetic sensor is different from the radius of the magnet. 2. The rotation angle sensor according to claim 1, wherein the magnetic sensor is composed of a first pair and a second pair, and a straight line passing through a center of each of the magnetic sensors included in the first pair. An angle formed by a straight line passing through the center of each of the magnetic sensors included in the second pair is 30 degrees or more and 150 degrees or less. 3. The rotation angle sensor according to claim 1, wherein the magnetic sensor is within a range in which a magnetic flux density detectable by the magnetic sensor changes linearly with respect to a radial displacement of the magnet. A rotation angle sensor characterized in that it is arranged in. 4. The rotation angle sensor according to claim 1, wherein the magnetic sensor is sealed in a surface mountable container on a mounting surface on which the magnetic sensor is mounted. Rotation angle sensor.