JPH08178937A - Magnetism detecting device - Google Patents

Abstract

PURPOSE: To provide a magnetism detecting device wherein offset error caused by deviation between a bias magnet and a magnetic reluctance element in the direction of a principal plane of a sensor part is reduced. CONSTITUTION: A pair of bias magnets 11 and 12 are, with a magnetism detecting position P in between, while at the opposite positions in x-direction parallel with a principal plane of a sensor part, extended in y-direction which is parallel with the principal plane of the sensor part and perpendicular to the x-direction. Further, pole faces on the side facing the sensor part of both the bias magnets 11 and 12 have polarities reverse to each other. Thus magnetic field almost toward the x-direction is formed at the magnetism detecting position P, so that magnetic field intensity at each point on a line extending in the x-direction, including the magnetism detecting position P, are almost equal to each other. So that, even when a magnetic reluctance element of the sensor part is relatively displaced in the x-direction to the bias magnets, magnetic field component acting upon the magneto-resistance element is hardly changed, and the change in reluctance value is also small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detector using a magnetoelectric conversion element. The magnetic detection device of the present invention is applied to, for example, a rotation detection device.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a conventional magnetic detection device using an MR element (hereinafter also referred to as an MR type magnetic detection device). This device is a rotation detecting device, and is a bias magnet 111 which is arranged close to a magnetic detection position P where a magnetic field is to be detected and forms a predetermined bias magnetic field at this position P, and a resistance value changes according to the magnetic field. The plate-shaped sensor unit 11 in which the magnetoresistive element is arranged on the main surface and is arranged at the position P
2 and a gear 114 having a highly magnetically permeable tooth portion 113 that rotates close to the position P in the direction perpendicular to the main direction M of the magnetic field. Reference numeral 115 is a spacer made of a flat plate having a constant thickness fixed to the N pole surface of the bias magnet, and 116 is a base plate to which the bias magnet 111 is fixed. In the sensor unit 112, an MR element is arranged in the vicinity of the position P in a bridge circuit configuration or a single or half bridge circuit configuration, and M due to the proximity or separation of the tooth portion 113.
Rotation is detected mainly by detecting a magnetic field change in the X direction at the R element position.

FIG. 12 shows a waveform of the output voltage Vo when a pair of MR elements are arranged in a half bridge circuit configuration. The MR element r1 is arranged in a zigzag shape so as to flow mainly in the x direction, and the MR element r2 is arranged in a zigzag shape so as to mainly flow in the y direction. As a result, the resistance of the MR element r2 is caused by the rotation of the tooth portion 113. A sinusoidal output voltage Vo is obtained by changing the value.

[0004]

However, in the above-mentioned conventional magnetic detecting device, when the relative position between the MR element and the bias magnet is deviated in the principal plane direction, that is, in the x and y directions in the drawing, the initial bias magnetic field of the MR element is generated. , Which causes an offset error in the resistance value of the MR element, and the offset error increases at both ends thereof. Similarly, in an MR element having a bridge circuit configuration (hereinafter, also referred to as an MR element bridge), the DC component of the signal voltage generated as the midpoint potential of the bridge varies and the offset error voltage increases. FIG. 13A schematically shows the magnetic pole surface of the bias magnet 111, FIG. 13B shows a sectional view in a direction perpendicular to the magnetic pole surface of the bias magnet 111, and FIG. 13C shows N of the bias magnet 111. 1 shows changes in the x-direction magnetic field component (Hx) on a line extending in the x direction through a magnetic detection position P that is apart from the principal surface center k of the pole surface in the z direction by a predetermined distance d.
3 (d), the y-direction magnetic field component (Hy) on the line extending in the y direction through the magnetic detection position P separated from the principal plane center k of the N pole surface of the bias magnet 111 in the z direction by the predetermined distance d in the z direction.
Shows the change in The electric resistance of the MR element on the sensor unit 112 is the x-direction magnetic field component (Hx) or the y-direction magnetic field component (Hy).
Will change due to changes in. That is, such an increase in offset error has been a serious obstacle to improving sensor sensitivity and accuracy.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a magnetic detection device capable of reducing an offset error due to a positional deviation between a bias magnet and a magnetoelectric conversion element in a magnetic detection direction of a sensor section. , Its purpose is.

[0006]

The first structure of the present invention is as follows.
The magnetic detection includes a bias magnet that is arranged close to a magnetic detection position where a magnetic field is to be detected and that forms a predetermined bias magnetic field at the magnetic detection position, and a magnetoelectric conversion element that converts a change in the bias magnetic field into an electrical change. In a magnetic detection device including a position or a sensor unit arranged in the vicinity thereof,
At least a pair of the bias magnets are parallel to the magnetic detection direction of the sensor unit and are perpendicular to the x direction at positions opposite to each other in the x direction parallel to the magnetic detection direction of the sensor unit with the magnetic detection position sandwiched therebetween. The magnetic detection device is characterized in that it extends in the y-direction and has magnetic pole surfaces of opposite polarities facing the sensor unit.

A second structure of the present invention is characterized in that, in the first structure, the magnetoelectric conversion element is a magnetoresistive element. The third configuration of the present invention is the above first aspect.
Further, in the above configuration, the magnetic pole surface of the bias magnet is arranged parallel to the main surface of the sensor unit. In a fourth configuration of the present invention, in addition to the third configuration, one main surface of a non-magnetic spacer made of a flat plate having a constant thickness is fixed on the magnetic pole surfaces of the pair of bias magnets having different polarities, The sensor part is fixed to the opposite main surface of the spacer.

According to a fifth aspect of the present invention, in addition to the second configuration, the magnetoresistive element is a magnetically sensitive conductive member extending back and forth in the y direction on the main surface of the sensor section. It is characterized in that it is mainly composed of road parts. A sixth configuration of the present invention is characterized in that, in the first configuration, the magnetoelectric conversion element is a Hall element.

A seventh structure of the present invention is characterized in that, in the first structure, the both bias magnets have magnetic pole surfaces facing each other with polarities opposite to each other. An eighth structure of the present invention further includes a gear having a highly magnetically permeable tooth portion that is rotatable in the x direction while being close to the magnetic detection position in the first to seventh structures. It is characterized by being used as a device.

[0010]

According to the first structure of the present invention, the pair of bias magnets are arranged such that the pair of bias magnets are arranged at opposite positions in the x direction parallel to the magnetic detection direction of the sensor unit with the magnetic detection position interposed therebetween. It extends in the y direction parallel to the detection direction and perpendicular to the x direction. Further, the magnetic pole surfaces of the both bias magnets on the side facing the sensor section have polarities opposite to each other.

With this configuration, a magnetic field that extends substantially in the x direction is formed at the magnetic detection position, so that the magnetic field strengths at points on the line extending in the x direction including the magnetic detection position are almost equal. Therefore, even if the magnetoelectric conversion element of the sensor section is displaced relative to the bias magnet in the x direction, the magnetic field component acting on the magnetoelectric conversion element hardly changes and the electrical change is small.

Therefore, the offset error due to the positional displacement between the bias magnet and the magnetoelectric conversion element in the x direction of the sensor section is significantly reduced as compared with the prior art. Second of the present invention
In the above configuration, since the magnetoelectric conversion element is a magnetoresistive element in the first configuration, a change in the magnetic field to be detected can be converted into a change in resistance value. In the third configuration of the present invention,
Further, in the second configuration, the magnetic pole surface of the bias magnet is arranged parallel to the main surface of the sensor portion, which facilitates the arrangement.

In a fourth structure of the present invention, in addition to the third structure, one main surface of a nonmagnetic spacer made of a flat plate having a constant thickness is fixed on the magnetic pole surfaces of the pair of bias magnets having different polarities. Since the sensor portion is fixed to the opposite main surface of the spacer, the arrangement becomes easier. In a fifth configuration of the present invention, in addition to the second configuration, the magnetoresistive element is mainly composed of a magnetically sensitive conductive path portion extending back and forth in the y direction on the main surface of the sensor portion. Therefore, the sensitivity (rate of change in resistance value) can be improved.

In the sixth structure of the present invention, since the magnetoelectric conversion element is a Hall element in the first structure,
Changes in the magnetic field to be detected can be converted into changes in Hall voltage. In the seventh configuration of the present invention, further, in the first configuration, since both bias magnets have magnetic pole surfaces facing each other with opposite polarities, each point on the line extending in the x direction including the magnetic detection position. The magnetic field strengths of 1 and 2 are further equalized, and the electrical change due to the magnetic field change due to the x-direction displacement of the magnetoelectric conversion element can be further reduced.

[0015]

【Example】

(Embodiment 1) An embodiment of the magnetic detection device of the present invention is shown in FIGS.
This will be described with reference to FIG. This device is a rotation detecting device, and a pair of bias magnets 11 and 12 that are arranged in proximity to a magnetic detection position P where a magnetic field is to be detected and that form a predetermined bias magnetic field at this position P have a resistance value that depends on the magnetic field. The sensor unit 2 in the form of a plate (chip) disposed at the position P and the magnetoresistive element that changes as a function of the magnetoresistive element are rotated in the x and z planes close to the position P. And a gear 4 having a highly magnetically permeable tooth portion 3. The base plate 5 is a flat base plate in which the S pole surface of the bias magnet 11 and the N pole surface of the bias magnet 12 are bonded to the main surface, and is made of a non-magnetic material or a magnetic material. 6 is a spacer made of a non-magnetic flat plate having a constant thickness, the upper surface of which is the N pole surface of the bias magnet 11 and the S of the bias magnet 12.
It is adhered to the polar surface, and the sensor portion 2 is adhered to the lower surface thereof. That is, the spacer 6 is for ensuring a certain space between the bias magnets 11 and 12 and the sensor unit 2 so that the magnitude and direction of the bias magnetic field are as close as possible in the vicinity of the magnetic detection position P. Is.

Explaining further, the bias magnets 11 and 12
Is composed of a magnetized portion of a ferrite-based plastic magnet plate 1 having a substantially square flat plate shape and having anisotropy in the plate thickness direction, as shown in FIGS. 2 (a) and 2 (b). , The plastic magnet plate 1 is magnetized in the y-direction between the left and right ends of the plastic magnet plate 1 at distances d1 to d2. Note that (a) is a view of the plastic magnet plate 1 looking up in the z direction (in FIG. 1), and (b) is a view showing a cross section thereof in the x and z directions. These bias magnets 11, 12 extending in the y direction
The other parts of the plastic magnet plate 1 are not magnetized. In this embodiment, the line connecting the magnetic detection position P and the axis of the gear 4 extends in the z direction, and the x direction is the direction perpendicular to the z direction in the rotation plane of the tooth portion 3, The direction orthogonal to these x and y directions is the y direction. The origin of the three-dimensional space coordinates is the magnetic detection position P. In addition, the main surface of the plastic magnet plate 1 and the main surface of the sensor unit 2 are assumed to extend in the x and y planes, and the four sides of the plastic magnet plate 1 shown in FIG. Shall extend to. Point k shown in FIG. 2B is a center point of the downward main surface of the plastic magnet plate 1, and point k is a point separated from the magnetic detection position P by a predetermined distance d in the z direction. That is, the k point is disposed so as to be displaced from the P point to the opposite gear side by the thickness of the spacer 6 and the thickness of the sensor portion 2.

The sensor section 2 includes a pair of MR elements 21 and 22 each of which has a pattern shown in FIG. 3 formed of a thin film of a ferromagnetic metal on a silicon substrate to form a half bridge circuit, and an output voltage of the half bridge circuit. It has an amplification circuit (not shown) for amplifying (signal voltage), a constant voltage circuit, and the like, and these MR elements are formed on the main surface of the sensor section 2 on the gear side. More specifically, the MR element 21 is mainly composed of a magnetically sensitive conductive path portion 21a extending back and forth in the y direction, and the MR element 22 is composed of a magnetically sensitive conductive path portion 22a extending back and forth in the x direction. It is mainly configured, and the magnetic detection position P is set in the middle of both elements 21 and 22, as shown in FIG. 3, and both elements 21 and 22 are arranged in the x direction. Of course, other arrangements are possible as long as both the elements 21 and 22 are arranged close to the magnetic detection position P. For example, the element 21 is emphasized and the magnetic detection position P is set at the point P ′ in FIG. Good.

Since the gear 5 is made of a highly magnetically permeable material, the gear 5
The magnetic field acting on the MR elements 21 and 22 changes as the tooth portion 3 moves. Hereinafter, the magnetic field strength (normally, the magnetic field strength is also simply referred to as a magnetic field) at each position on the line extending in the x direction through the magnetic detection position P is shown in FIG. The magnetic field strength at each position on the line extending in the y-direction and the y-direction (normally, the magnetic field strength is also simply referred to as a magnetic field) is shown in FIG. It can be seen that the x-direction component Hx of the magnetic field H and the y-direction component Hy of the magnetic field H have small changes in the magnetic field even when displaced from the magnetic detection position P in the x and y directions. Therefore, the sensor unit 2 is configured such that the bias magnets 11, 12
Relative to the x direction or the y direction, the x direction component Hx or the y direction component Hy of the magnetic field hardly changes, and the DC fluctuation of the output voltage due to these displacements, so-called offset error voltage is almost You can see that it does not occur.

Next, the magnetic field-resistance change characteristics of the MR elements 21 and 22 are shown in FIG. A is the change in resistance change rate due to the change in the y-direction component of the magnetic field in the MR element 21, or MR
The change in the resistance change rate due to the change in the x direction component of the magnetic field in the element 22 is shown, and B is the resistance change due to the change in the y direction component of the magnetic field in the MR element 22, or the MR element 21.
4 shows a change in resistance due to a change in the x-direction component of the magnetic field at. Such characteristics are well known. Therefore,
The resistance value of the MR element 21 changes significantly due to the approach and separation of the tooth portion 3 in the x direction. MR elements 21, 2
Since 2 constitutes a half bridge circuit as shown in FIG. 3, its output voltage changes according to the change in the resistance value of the MR element 21, and the rotation of the rotary shaft can be detected by this. The spacer 6 may be omitted.

(Embodiment 2) Another embodiment is shown in FIG. In this embodiment, the left half of the plastic magnet plate 1 in FIG. 5 is magnetized so that the lower main surface becomes the N pole, and the left half of FIG. 5 is magnetized so that the lower main surface becomes the S pole. The same effect as the first embodiment is obtained.

(Embodiment 3) Another embodiment is shown in FIG. In this embodiment, the non-magnetized portion at the central portion in the x direction to which the sensor portion 2 is adhered is projected downward in the z direction from the magnetized portions on both sides thereof.
Can be omitted.

(Embodiment 4) Another embodiment is shown in FIG. However, components having the same functions as those in the first embodiment are designated by the same reference numerals. In this embodiment, the bias magnets 11 and 12 and the sensor portion 2 are bonded to the resin plate portion 8 which is a kind of spacer and base. However, in this embodiment, the N-pole surface of the bias magnet 11 and the S-pole surface of the bias magnet 12 are respectively bonded to the resin plate portion 2 in a posture inclined slightly toward the sensor portion 2.

By doing so, the change in the magnetic field at each position in the x direction is further reduced. (Embodiment 5) Another embodiment is shown in FIG. However, Example 1
The same reference numerals are given to the components having the same functions as those of the above. In this embodiment, the bias magnets 11 and 12 and the sensor portion 2 are provided on the same surface of the resin plate portion 9 which is also a kind of spacer and base.
Are glued together. However, the N pole surface of the bias magnet 11 and the S pole surface of the bias magnet 12 face each other in front of each other with the sensor unit 2 interposed therebetween, and as a result, the change in the magnetic field at each position in the x direction is further reduced. Note that FIG. 9 is a view as seen from the gear 4 side.

(Embodiment 6) Another embodiment is shown in FIG. In this embodiment, the plastic magnet plate 1 is centered on the point K.
The Hall element portion 101 is disposed near the magnetic detection position P in the fixing hole formed in the
The Hall sensor 10 is passed through and fixed so that the magnetic detection direction of 1 is parallel to the main surface of the plastic magnet plate 1. In this way, the Hall sensor according to the first embodiment
Has the same effect as.

[Brief description of drawings]

FIG. 1A is a schematic front view showing an embodiment of a magnetic detection device of the present invention. (B) It is a magnetic force diagram which shows distribution of the magnetic flux (PHI) in the apparatus of FIG.

2 (a) is a plan view of the plastic magnet plate 1 of FIG. 1. FIG. (B) It is the x, z direction sectional view. (C) A characteristic diagram showing changes in the magnetic field Hx when the magnetic detection position P moves in the x direction. (D) A characteristic diagram showing a change in the magnetic field Hx when the magnetic detection position P moves in the y direction.

3 is an MR element 21 formed in the sensor unit 2 of FIG.
22 is a schematic layout diagram of 22. FIG.

FIG. 4 is a characteristic diagram showing a relation between a magnetic field change of the MR elements 21 and 22 in the x direction or the y direction and a resistance value.

FIG. 5 is a front view of the magnetic detection device according to the second embodiment.

FIG. 6 is a front view of a magnetic detection device according to a third embodiment.

FIG. 7 is a front view of a magnetic detection device according to a fourth embodiment.

FIG. 8 is a front view of a magnetic detection device of Example 5.

9 is a plan view of the magnetic detection device of FIG. 8. FIG.

FIG. 10 is a front view of a magnetic detection device according to a sixth embodiment.

FIG. 11 is a front view of a conventional magnetic detection device.

12 is a timing chart showing output characteristics of the conventional device of FIG.

13 (a) is a plane of the bias magnet of FIG. 11. FIG. (B) It is a front sectional view of the bias magnet of FIG. 11. (C) A characteristic diagram showing changes in the magnetic field Hx when the magnetic detection position P moves in the x direction. (D) A characteristic diagram showing a change in the magnetic field Hx when the magnetic detection position P moves in the y direction.

[Explanation of symbols]

P is a magnetic detection position, 1 is a plastic magnet plate, 2 is a sensor part, 3 is a tooth part, 4 is a gear, 6 is a spacer, 11, 12
Is a bias magnet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Aoyama 1-1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (8)

[Claims] 1. A bias magnet which is arranged close to a magnetic detection position where a magnetic field is to be detected and forms a predetermined bias magnetic field at the magnetic detection position, and a magnetoelectric conversion element which converts a change in the bias magnetic field into an electrical change. In the magnetic detection device including the magnetic detection position or a sensor unit arranged in the vicinity thereof, at least a pair of the bias magnets are arranged in parallel to the magnetic detection direction of the sensor unit with the magnetic detection position interposed therebetween. The magnetic pole surfaces of the magnetic poles having opposite polarities toward the sensor portion, the magnetic pole surfaces being parallel to the magnetic detection direction of the sensor portion and extending in the y direction perpendicular to the x direction. A magnetic detection device characterized by the above. 2. The magnetic detection device according to claim 1, wherein the magnetoelectric conversion element is a magnetoresistive element. 3. The magnetic detection device according to claim 2, wherein a magnetic pole surface of the bias magnet is arranged parallel to a main surface of the sensor unit. 4. A main surface of a non-magnetic spacer made of a flat plate having a constant thickness is fixed to the magnetic pole surfaces of the pair of bias magnets having different polarities, and the sensor portion is fixed to the opposite main surface of the spacer. The magnetic detection device according to claim 3, 5. The magnetic detection device according to claim 2, wherein the magnetoresistive element is mainly composed of a magnetically sensitive conductive path portion extending back and forth in the y direction on the main surface of the sensor portion. . 6. The magnetic detection device according to claim 1, wherein the magnetoelectric conversion element is a Hall element. 7. The magnetic detection device according to claim 1, wherein the both bias magnets have magnetic pole surfaces facing each other with polarities opposite to each other. 8. The magnetic device according to claim 1, further comprising a gear having a highly magnetically permeable tooth portion that is rotatable in the x direction while being close to the magnetic detection position, and is used as a rotation detecting device. Detection device.