JP3487452B2 - Magnetic detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetism detecting device using a magnetoelectric conversion element. The magnetic detection device of the present invention is applied to, for example, a rotation detection device. 2. Description of the Related Art FIG. 11 shows an example of a conventional magnetic detector using an MR element (hereinafter also referred to as an MR type magnetic detector). This device is a rotation detecting device, which is disposed 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. A plate-shaped sensor unit 11 in which a magnetoresistive element is disposed on a main surface and disposed at a position P
2 and a gear 114 having highly magnetically permeable teeth 113 rotating in the direction perpendicular to the main direction M of the magnetic field in the vicinity of the position P. Reference numeral 115 denotes a spacer made of a flat plate having a fixed thickness fixed on the N-pole surface of the bias magnet. Reference numeral 116 denotes a base plate to which the bias magnet 111 is fixed. In the sensor unit 112, an MR element is arranged in a bridge circuit configuration or a single or half-bridge circuit configuration in the vicinity of the position P.
The rotation is detected mainly by detecting a change in the magnetic field in the X direction at the R element position. FIG. 12 shows a waveform of an 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 flow mainly in the y direction. By the change of the value, a sinusoidal output voltage Vo is obtained. However, in the above-described conventional magnetic detecting device, if the relative position between the MR element and the bias magnet is displaced in the main surface direction, that is, in the x and y directions in the figure, the MR element will not move. The initial bias magnetic field varies, thereby causing an offset error in the resistance value of the MR element, and the offset error increases at both ends. Similarly, in an MR element configured as a bridge circuit (hereinafter, also referred to as an MR element bridge), a DC component of a signal voltage generated as a midpoint potential of the bridge varies, and an offset error voltage increases. FIG. 13A schematically shows the magnetic pole surface of the bias magnet 111, FIG. 13B shows a cross-sectional view in a direction perpendicular to the magnetic pole surface of the bias magnet 111, and FIG. FIG. 1 shows a change in the x-direction magnetic field component (Hx) on a line extending in the x-direction through a magnetic detection position P separated by a predetermined distance d in the z-direction from the center k of the main surface of the pole surface.
3 (d), a y-direction magnetic field component (Hy) on a line extending in the y direction through a magnetic detection position P separated by a predetermined distance d in the z direction from the center k of the main surface of the N pole surface of the bias magnet 111 in the y direction.
Shows the change. The electric resistance of the MR element on the sensor unit 112 is represented by an x-direction magnetic field component (Hx) or a y-direction magnetic field component (Hy).
Will change due to changes in That is, such an increase in the offset error has been a serious obstacle in improving sensor sensitivity and accuracy. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic detector capable of reducing an offset error due to a displacement between a bias magnet and a magnetoelectric transducer in a magnetic detection direction of a sensor unit. , Its purpose. [0006] According to an aspect of the present invention, the bias magnet is arranged close to the magnetic detection position to detect a magnetic field to form a predetermined bias magnetic field to the magnetic detection position, the magnetic
A sensor unit having a magneto-electric transducer which is arranged in the gas detection position is converted into electrical change a change in the bias magnetic field in the magnetic detection position, the change of the magnetic field of the magnetic detection position
And a gear having highly magnetically permeable teeth , wherein at least a pair of the bias magnets are opposite to each other in the x direction parallel to the magnetic detection direction of the magnetoelectric conversion element with the magnetic detection position interposed therebetween. before similar position Symbol x
Wherein together are extended respectively in the direction perpendicular y-direction
The bias magnetic field is formed substantially in the x direction at the magnetic detection position
The gear moves toward the magnetic detection position while
A magnetic detection device characterized by rotating at right angles to a direction . [0007] Preferably, the magnetoelectric conversion element is a magnetoresistive element . Preferably, the pole face of the bias magnet Ru are arranged in parallel to the main surface of the sensor portion. Preferably, one main surface of a non-magnetic spacer made of a flat plate having a fixed thickness is fixed on magnetic pole surfaces of different polarities of the pair of bias magnets, and the sensor unit is fixed to an opposite main surface of the spacer. . Preferably, the magnetoresistive element is mainly constituted by a magneto-sensitive conductive path portion extending back and forth in the y direction on the main surface of the sensor portion . Preferably, the magnetoelectric conversion element is a Hall element . According to the present invention , the pair of bias magnets are arranged such that the pair of bias magnets are positioned opposite to each other in the x direction parallel to the magnetic detection direction of the sensor with the magnetic detection position interposed therebetween. They are respectively extended in the y direction parallel to the magnetic detection direction and perpendicular to the x direction. Furthermore, both the bias magnet, the magnetic sensing position
A magnetic field extending substantially in the x-direction is formed at the position. [0011] If in this manner, since the magnetic field toward the substantially x-direction is formed on the magnetic position detection, the magnetic field intensity of each point on the line extending in the x-direction comprise a magnetic detection position is almost equal. Therefore, even if the magnetoelectric conversion element of the sensor unit 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, an offset error caused by a displacement between the bias magnet and the magnetoelectric conversion element in the x direction of the sensor unit is significantly reduced as compared with the related art. If magnetoelectric transducer is a magnetoresistive element can be converted to changes in the magnetic field to be detected change in the resistance value. If the pole face of the bias magnet is arranged parallel to the main surface of the sensor section, thereby facilitating the arrangement. [0013] Is fixed is different polarities nonmagnetic one major surface of the spacer made from a constant thickness of the flat plate on the pole face of the pair of bias magnets, the sensor unit when it is secured to the opposite major surface of the spacer arrangement is It becomes even easier . Magnetoresistive elements, when composed primarily sensitive permeative electrical path portion that extends back and forth in the y-direction in the main surface of the sensor portion, it is possible to improve the sensitivity (resistance change rate) it can. (Embodiment 1) One embodiment of the magnetic detection apparatus 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 which are arranged close to a magnetic detection position P where a magnetic field is to be detected and form a predetermined bias magnetic field at this position P, and whose resistance value depends on the magnetic field. (A chip-shaped) sensor unit 2 disposed at the position P and rotating in the x and z planes close to the position P. And a gear 4 having teeth 3 having high magnetic permeability. 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. Reference numeral 6 denotes a spacer made of a non-magnetic flat plate having a constant thickness, and the upper surfaces thereof are the N-pole surface of the bias magnet 11 and the S
The sensor part 2 is adhered to the lower surface thereof. That is, the spacer 6 is used to secure a constant interval between the bias magnets 11 and 12 and the sensor unit 2 in order to make the magnitude and direction of the bias magnetic field as close to the magnetic detection position P as possible. It is. More specifically, the bias magnets 11 and 12
Is composed of a magnetized portion of a ferrite-based plastic magnet plate 1 which has a substantially square plate shape and has anisotropy in the plate thickness direction, as shown in FIGS. 2 (a) and 2 (b). The magnet is magnetized in the y-direction between distances d1 and d2 from both left and right ends of the plastic magnet plate 1. (A) is a diagram in which the plastic magnet plate 1 is seen upward in the z direction (in FIG. 1), and (b) is a diagram showing a cross section in the x and z directions. These bias magnets 11, 12 extending in the y direction
Other parts of the plastic magnet plate 1 are not magnetized. In this embodiment, a line connecting the magnetic detection position P and the axis of the gear 4 extends in the z direction, and the x direction is a 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 defined as the y direction. The origin of the three-dimensional space coordinates is a magnetic detection position P. The main surface of the plastic magnet plate 1 and the main surface of the sensor unit 2 extend in the x and y planes. The four sides of the plastic magnet plate 1 shown in FIG. Shall extend. A point k shown in FIG. 2B is a center point of the downward main surface of the plastic magnet plate 1, and a point k is a point separated from the magnetic detection position P by a predetermined distance d in the z direction. That is, the point k is displaced from the point P toward the non-gear side by the thickness of the spacer 6 and the thickness of the sensor section 2. The sensor section 2 comprises a pair of MR elements 21 and 22 which are formed on a silicon substrate by forming a pattern shown in FIG. 3 with a thin film of a ferromagnetic metal to form a half bridge circuit, and an output voltage of the half bridge circuit. It has an amplifier circuit (not shown) for amplifying (signal voltage), a constant voltage circuit, and the like. These MR elements are formed on the gear-side main surface of the sensor unit 2. More specifically, the MR element 21 mainly includes a magneto-sensitive conductive path portion 21a extending reciprocally in the y direction, and the MR element 22 includes a magneto-sensitive conductive path portion 22a extending reciprocally in the x direction. Mainly, the magnetic detection position P is set in the middle between the two elements 21 and 22 as shown in FIG. 3, and the two elements 21 and 22 are arranged in the x direction. Of course, other arrangements are possible as long as the two elements 21 and 22 are arranged close to the magnetic detection position P. For example, the magnetic detection position P is set at a point P ′ in FIG. Is also good. Since the gear 5 is made of a highly magnetically permeable material, the gear 5
As the tooth 3 moves, the magnetic field acting on the MR elements 21 and 22 changes. Hereinafter, the magnetic field strength (generally, the magnetic field strength is also simply referred to as a magnetic field) at each position on a line extending in the x direction through the magnetic detection position P is shown in FIG. FIG. 2D shows the magnetic field strength (generally, the magnetic field strength is also simply referred to as a magnetic field) at each position on a line extending in the direction and the y direction. 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 change little even when displaced from the magnetic detection position P in the x and y directions. Therefore, the sensor unit 2 is provided with the bias magnets 11 and 12.
, 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, the so-called offset error voltage, is hardly changed due to these displacements. It turns out that it does not occur. FIG. 4 shows the magnetic field-resistance change characteristics of the MR elements 21 and 22. A is a change in the rate of change in resistance due to a change in the y-direction component of the magnetic field in the MR element 21, or
A change in the resistance change rate due to a change in the x-direction component of the magnetic field in the element 22 is indicated by B. A resistance change due to a change in the y-direction component of the magnetic field in the MR element 22 or the MR element 21
5 shows a resistance change 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 greatly changes due to the approach and the separation of the tooth portion 3 in the x direction. MR element 21, 2
2 constitutes a half-bridge circuit as shown in FIG. 3, so that its output voltage changes in accordance with the change in the resistance value of the MR element 21, whereby the rotation of the rotating shaft can be detected. Note that the spacer 6 can 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 has an N pole, and the left half in FIG. 5 is magnetized so that the lower main surface has an S pole. Thus, the same effects as in the first embodiment can be obtained. (Embodiment 3) Another embodiment is shown in FIG. In this embodiment, the non-magnetized portion at the center in the x direction to which the sensor portion 2 is adhered protrudes downward in the z direction from the magnetized portions on both sides thereof.
Can be omitted. (Embodiment 4) FIG. 7 shows another embodiment. However, components having the same functions as in the first embodiment are denoted by the same reference numerals. In this embodiment, the bias magnets 11 and 12 and the sensor unit 2 are adhered to the resin plate 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 bonded to the resin plate 2 in a posture slightly inclined toward the sensor unit 2. With this arrangement, 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, Embodiment 1
Components having the same functions as those described above are denoted by the same reference numerals. In this embodiment, the bias magnets 11 and 12 and the sensor unit 2 are provided on the same surface of a resin plate 9 which is a kind of spacer and base.
Is glued. However, the N-pole surface of the bias magnet 11 and the S-pole surface of the bias magnet 12 face directly in front of each other with the sensor unit 2 interposed therebetween. As a result, the change in the magnetic field at each position in the x direction is further reduced. 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.
In the fixing hole drilled in the hole, the Hall element portion 101 is disposed in proximity to the magnetic detection position P.
The magnetic sensor 1 is fixed through the Hall sensor 10 so that the magnetic detection direction is parallel to the main surface of the plastic magnet plate 1. By doing so, the first embodiment can be applied to the Hall sensor.
It has the same effect as.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a schematic front view showing one embodiment of the magnetic detection device of the present invention. FIG. 2 (b) is a magnetic force diagram showing the distribution of magnetic flux Φ in the apparatus of FIG. FIG. 2A is a plan view of the plastic magnet plate 1 of FIG. (B) It is x, z direction sectional drawing. (C) is a characteristic diagram illustrating a change in the magnetic field Hx when the magnetic detection position P moves in the x direction. (D) is a characteristic diagram illustrating a change in the magnetic field Hx when the magnetic detection position P moves in the y direction. FIG. 3 shows an MR element 21 formed in the sensor unit 2 of FIG. 1;
FIG. 22 is a schematic layout view of No. 22. FIG. 4 is a characteristic diagram showing a relationship between a change in a magnetic field in the x direction or the y direction of the MR elements 21 and 22 and a resistance value. FIG. 5 is a front view of a magnetic detection device according to a 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 according to a fifth embodiment. FIG. 9 is a plan view of the magnetic detection device of FIG. 8; 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. FIG. 12 is a timing chart showing output characteristics of the conventional device of FIG. FIG. 13 (a) is a plane view of the bias magnet of FIG. FIG. 12B is a front sectional view of the bias magnet of FIG. 11. (C) is a characteristic diagram illustrating a change in the magnetic field Hx when the magnetic detection position P moves in the x direction. (D) is a characteristic diagram illustrating a change in the magnetic field Hx when the magnetic detection position P moves in the y direction. [Description of Signs] P is a magnetic detection position, 1 is a plastic magnet plate, 2 is a sensor section, 3 is a tooth section, 4 is a gear, 6 is a spacer, 11, 12
Is a bias magnet.

Continuation of the front page (72) Inventor Masaki Aoyama 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-2-208569 (JP, A) JP-A 4-282481 (JP) , A) JP-A-3-2455061 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 3/488 G01D 5/245

Claims (1)

(57) 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 which is arranged at the magnetic detection position. Said
A sensor unit having a magneto-electric transducer for converting a change in the bias magnetic field in the magnetic detection position electrical change, the magnetic
Highly permeable teeth that change the magnetic field at the air detection position
And a gear , wherein at least one pair of the bias magnets is x parallel to a magnetic detection direction of the magnetoelectric conversion element with the magnetic detection position interposed therebetween.
The magnetic detection position together are extended respectively to the front Symbol x direction perpendicular y-direction similar positions opposite to each other in the direction
The bias magnetic field is formed substantially in the x direction at
With respect to the y direction while approaching the magnetic detection position.
A magnetic detection device characterized by rotating at right angles .