JPH07333236A - Magnetic detector - Google Patents

Abstract

PURPOSE:To provide a magnetic detector of a hollow magnet structure which enables the minimizing of a drop in the sensitivity of a magnetoresistance element. CONSTITUTION:A bias magnet 3 is prepared to generate a bias magnetic field toward a gear 5 and a through hole 4 is formed hollow in the bias magnet 3. Magnetoresistance elements 7 and 8 are held with a mold material 2 which 2 is arranged to pierce the through hole 4 of the bias magnet 3. The magnetoresistance elements 7 and 8 are so arranged that the surface position of the bias magnet 3 is set at 3a or 3b between the bias magnet 3 and the gear 5 and changes in the condition of the bias magnetic field are detected from a change in resistance values of the magnetoresistance elements 7 and 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a magnetic change by utilizing a change in resistance value with respect to a change in magnetic field of a magnetoresistive element. The present invention relates to a magnetic detection device for detecting.

[0002]

2. Description of the Related Art Usually, a proximity type rotation sensor for detecting rotation of a gear-shaped gear by a magnetic resistance element has a magnetic circuit structure in which a magnet surface and a sensor element are parallel to each other (on the back surface of the sensor element). Place a magnet) is the most. In this method, the deflection angle of the magnetic vector in the direction perpendicular to the current direction of the magnetoresistive element is used for detection. However, when the deflection angle becomes large, a waveform crack is generated in the output waveform. It may cause malfunction.

Therefore, in Japanese Unexamined Patent Publication (Kokai) No. 3-195970, the sensor element is arranged vertically to the magnet surface.
In addition, the magnetoresistive element in the sensor element is arranged at 45 degrees so that the waveform crack can be prevented. Further, the inventors of the present application make the bias magnet hollow relative to the sensor disclosed in Japanese Patent Application No. 4-329670 and insert a sensor element in the hollow so that the distance between the sensor element and the bias magnet becomes as short as possible. Thus, a sensor structure is provided which can prevent the sensitivity of the sensor element from being lowered.

[0004]

However, as shown in FIG. 23, for example, the gear side of the hollow magnet 3 (not shown).
If the pole facing to the N pole is an N pole, the magnetic vector is attracted toward the through hole 4 (hollow portion) in the vicinity of the surface of the hollow structure of the magnet 3 regardless of the magnetic circuit with the gear, so that accurate rotation with respect to the gear is prevented. There are areas where sensitivity cannot be obtained. It is considered that the region where the magnetic flux is disturbed is related to the magnetic field strength of the surface 3S of the magnet 3 and the hollow shape. Therefore, when the sensor element was inserted into the hollow magnet 3, it was clarified by the experiments by the present inventors that the sensitivity is lowered depending on the arrangement position.

Therefore, an object of the present invention is to provide a magnetic detection device having a hollow magnet structure in which the sensitivity of the magnetoresistive element is prevented from being lowered as much as possible.

[0006]

A magnetic detection device according to claim 1, wherein a bias magnet for generating a bias magnetic field toward a detection target having a magnetic material, and the bias according to the movement of the detection target. A magnetic detection device comprising a magnetoresistive element that causes a change in resistance due to a magnetic field, wherein the bias magnet has a hollow shape, wherein the bias magnetic field is detected by a change in the resistance value of the magnetoresistive element. A magnetoresistive element is arranged so as to penetrate this hollow portion, and a part or just the whole of the magnetoresistive element projects from the hollow portion of the bias magnet to the surface of the bias magnet facing the detection target. It is characterized by being arranged like this.

According to a second aspect of the present invention, there is provided a magnetic detection device which produces a bias magnetic field for generating a bias magnetic field toward an object to be detected having a magnetic material and a bias magnetic field corresponding to the movement of the object to be detected to cause a resistance change. A magnetic detection device comprising a magnetoresistive element, wherein the change in the state of the bias magnetic field is detected by a change in the resistance value of the magnetoresistive element, wherein the bias magnet is hollow, and the magnetoresistive element is It is characterized in that it is arranged so as to penetrate through the portion, and that the entire magnetoresistive element is soaked into the hollow portion of the bias magnet from the surface of the bias magnet facing the object to be detected.

According to a third aspect of the present invention, there is provided the magnetic detection device according to the first or second aspect, wherein an angle formed by the magnetoresistive element with a hollow direction of a hollow portion of the bias magnet is an angle. It is characterized in that it has at least one pattern patterned so as to form an angle of about 45 °. The magnetic detection device according to claim 4 is the magnetic detection device according to any one of claims 1 to 3, further comprising a protection member for protecting the magnetoresistive element, wherein the protection member and the hollow portion are provided. It is characterized in that the bias magnet has a fitting portion fitted to each other.

[0009]

[Advantageous effects] A bias magnetic field is generated, and a bias magnet having a hollow structure and a magnetoresistive element arranged in this hollow structure are provided, and the motion of a magnetic body to be detected is applied to the magnetoresistive element. In the magnetic detection device configured to detect the change in the bias magnetic field of the bias magnet, as shown in FIGS. 6 to 15, the magnetic resistance depends on the position of the hollow portion of the bias magnet. It can be seen that the rate of resistance change greatly changes. It can be seen that there are two positions where the rate of change in magnetic resistance is maximum depending on the arrangement position. One is the position where the magnetoresistive element is completely inside the hollow structure, and the other is a part or substantially the whole of the magnetoresistive element protruding from the hollow structure of the bias magnet to its surface. The position.

Therefore, in the magnetic detection device according to the first or second aspect, since the magnetoresistive element is arranged so as to match the two positions, a large magnetoresistive change can be obtained. Therefore, it has an excellent effect that the detection sensitivity is improved. Further, in the magnetic detection device according to claim 3, the angle formed by the magnetoresistive element and the hollow direction of the hollow portion of the bias magnet is approximately 45 °.
Since it has at least one pattern that is patterned so as to have the above-mentioned effect, it is possible to prevent waveform cracking even when the deflection angle of the bias magnetic field accompanying the movement of the detection target is large. I have.

Further, in the magnetic detection device according to the present invention, there is provided a protection member for protecting the magnetoresistive element,
Since the protective member and the bias magnet having the hollow portion have fitting portions that are fitted to each other, an excellent effect that the magnetoresistive element can be easily arranged at the position according to claim 1 or 2. Is to have.

[0012]

【Example】

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a magnetic rotation detector (front view) of this embodiment. 2 is a plan view of the magnetic rotation detecting device, and FIG. 3 is a view taken in the direction of arrow A in FIG.

The sensor element 1 is molded with a molding material 2, and the molding material 2 is formed in a rod shape having a rectangular cross section. The sensor element 1 is arranged on the tip side of the molding material 2. Further, the lead frame 22 is molded with the molding material 2, and the lead frame 22 at the right end portion in FIG. 1 is exposed. In this embodiment, epoxy resin is used as the molding material.

The bias magnet 3 made of a permanent magnet has a cylindrical shape, and a rectangular through hole 4 is formed in the center thereof.
Extend in the longitudinal direction of the bias magnet 3. In this way, the bias magnet 3 has a hollow shape. In this embodiment, the bias magnet 3 is a ferrite plastic magnet. The bias magnet 3 does not have to have a columnar shape, and may have a quadrangular prism shape, for example.

The molding material 2 is inserted and fixed in the through hole 4 of the bias magnet 3. That is, the molding material 2 is inserted into the through hole 4 of the bias magnet 3 in a fitted state and fixed at a predetermined position with an adhesive. The gear 5 is a detection target having a magnetic material, and the gear 5 has a large number of teeth 6. The sensor element 1 is arranged so as to face the teeth 6 of the gear 5. That is, as shown in FIG. 4, the sensor element 1 is provided with two magnetoresistive elements 7 and 8 in the chip 9.
Are arranged substantially perpendicular to the magnet surface and substantially parallel to the gear rotation direction surface. The magnetoresistive elements 7 and 8 are the chip 9
Inside, a pair of magnets are arranged in the same plane as the magnetic field direction of the bias magnet 3 at an angle of plus / minus 45 degrees with respect to the magnetic field direction (indicated by W in FIG. 4).

Further, as shown in FIG. 2, the molding material 2 and the sensor element 1 are arranged on the center line (not shown) of the gear 5. Regarding the principle of magnetism detection, Japanese Patent Application Laid-Open No. 3-195970 or Japanese Patent Application No. 4-32967.
I will omit the explanation here as you refer to the publication No. 0.

As described above, since the vicinity of the surface of the hollow magnet is in a hollow state, the magnetic flux state is difficult to specify, and it is considered that there is a region where the magnetoresistive element has poor detection sensitivity. Therefore, the present inventors conducted an experiment on this point. In this experiment, the resistance change rate of the magnetoresistive element depending on the distance between the hollow magnet surface and the magnetoresistive element pattern was examined with the air gap, which is the actual distance between the magnetic gear and the magnetoresistive element pattern, as a parameter. . Further, in this experiment, two types of magnets having different sizes of the hollow-shaped opening region were used for the purpose of studying the characteristic change due to the difference in the size of the hollow-shaped opening region. The magnet used this time is a ferrite plastic magnet.

FIG. 5 shows a sample used in the experiment. This is a magnetoresistive element pattern arranged at 45 ° as shown in FIG. 1, but the length of the V-shape is shortened. Two magnetoresistive element patterns MRE are formed on the substrate SUB, and the arrow direction formed by the two patterns is the direction of the gear that is a magnetic body. The length L of the pattern in the gear direction (between u and d in the drawing) is 0.7.
It is 5 mm.

6 to 9 show the results of experiments with the magnet A having a hollow shape and a small opening area, and FIGS. 10 to 13 show the results of experiments with a magnet B having a large hollow area. In these figures, the MM distance represents the distance from the surface of the magnet facing the gear side (3a in FIG. 16) to the position d of the magnetoresistive element pattern in FIG. That is,
When the MM distance is 0 [mm], the magnetoresistive element pattern just protrudes from the hollow magnet surface.
When the MM distance is -0.75 [mm], it means that the magnetoresistive element pattern is housed in the cavity of the hollow magnet. Further, the air gap represents the distance between the gear and the position of u in FIG. 5 in the state where the gear teeth are closest to the magnetoresistive element pattern. The air gap is 1.1 [mm] to 3.1.
The value up to [mm] was changed in 0.5 [mm] units.

The minimum distance is set to 1.1 [mm] because the magnetoresistive element pattern is molded by the molding material 2 as can be seen from FIG. And the mold thickness when the mold material 2 and the bias magnet 3 as shown in FIG. 1 are molded, that is, the secondary mold thickness is taken into consideration, and the maximum distance is 3.1 [mm]. I said
This is because the magnetoresistive element detectable as a sensor has a resistance change rate of about 0.2%, and when the air gap is separated by 3.1 [mm] or more, the resistance change rate falls below 0.2%.

From FIGS. 6 to 15, it can be seen that the resistance change rate exhibits two maximum values when the MM distance is changed. That is, the position where the magnetoresistive element is completely housed in the hollow magnet (hereinafter referred to as the first peak) and the position where part or all of the magnetoresistive element protrudes from the surface of the hollow magnet to the gear side ( Hereinafter, it is referred to as a second peak). Moreover, the air gap is 2.
It can be seen that up to 6 mm, the resistance change rate is larger when the magnetoresistive element is arranged near the first peak than around the second peak. When the air gap is 3.1 [mm], the characteristic diagram is slightly different compared to when the air gap is smaller than that, but the resistance change rate is very small in this region, so it was difficult to measure, and such data was obtained. However, it seems that the actual results will be similar to those of other air gaps. Also, it can be seen that the maximum value shifts to the right as the air gap increases. Further, as shown in FIGS. 6, 7 and 11, when the air gap is 1.1 [mm] or when the magnet has a cylindrical shape of 1.6 [mm], the shaded circles represent unstable magnetic resistance. It is a region that shows changes and is a region that cannot be trusted as a sensor.

Therefore, in order to improve the detection sensitivity, it is preferable to dispose the magnetoresistive element in the hollow magnet so as to match the two peak positions. Bias magnets 3a and 3b in FIG. 1 or 2 show the case where the magnetoresistive elements are arranged so as to match these peak positions. Actually, since the peak is shifted by the air gap, the arrangement of the magnetoresistive elements according to the air gap, that is, FIG.
As shown in FIG. 15, since the peak position is slightly different depending on the magnet, it is necessary to adjust the peak position depending on the magnet used. When the peak position to be combined is set to the first peak,
Since the sensitivity can be maximized and the magnetoresistive element can be arranged in the magnet, the sensor itself can be downsized.

Further, the difference in the size of the hollow-shaped opening region appears as the difference in the rate of change in resistance. That is, it can be seen from FIGS. 6 to 15 that the smaller the hollow opening area, the larger the rate of resistance change. FIG.
In (a) and (b), the region where the resistance change rate is 0.2% or more and no waveform crack occurs is shown by the difference in the air gap AG. (A) of this figure is obtained from the data of FIGS. 6 to 10, and (b) is obtained from the data of FIGS. 11 to 15. The shaded area in the figure is the area in which the sensitivity is 0.2% or more for all air gaps, and this can be said in both figures (a) and (b). That is, if the MM distance is set from 0 [mm] to around +0.3 [mm], the air gap is 1.1 [mm] to
A range of 3.1 [mm] is a region that can be reliably detected. Setting the magnetoresistive element in this region is a very effective means when air gap management is difficult. That is, as described above, in order to arrange the magnetoresistive element in the maximum resistance change rate region, it is necessary to arrange it so as to match the first peak. In addition, in order to arrange the magnetoresistive element at the peak position, it is necessary to manage the air gap as well. In such a case, as shown in FIG. 6, FIG. 7 or FIG. Depending on the mounting position of, the output may enter an unstable output area and the resistance change may not be detected stably. Therefore, if the magnetoresistive element is aligned with the area of the second peak and arranged in the above range, it is possible to surely obtain a stable output.

As described above in detail, in the magnetic detection device according to the present embodiment, the sensitivity of the magnetoresistive element is reduced as much as possible by disposing the distance between the magnetoresistive elements 7 and 8 and the bias magnet 3 at an appropriate position. Can be suppressed. Further, when the magnetoresistive elements 7 and 8 are installed so that the angle formed by the bias magnetic field is approximately 45 degrees, it is possible to surely eliminate the waveform crack of the output waveform.

The magnetoresistive element does not have to be arranged at an angle of about 45 degrees, and only one magnetoresistive element may exhibit resistance change. (Second Embodiment) Next, an example in which the magnetoresistive element can be easily arranged at the peak position as shown in FIGS. 6 to 15 is shown below.

FIG. 17 shows a schematic view of the magnetic rotation detecting apparatus of this embodiment, and FIG. 18 shows a view taken in the direction of arrow C in FIG. Further, FIG. 19 shows a view taken in the direction of arrow D in FIG. In this embodiment, a through hole 17 is provided in the bias magnet 16, a molding material 18 is inserted into the through hole 17, and at the time of inserting the molding material 18 into the through hole 17, the magnetoresistive element 19 serves as the bias magnet 16. The through hole 17 and the molding material 18 are provided with a tapered step so as to stop at a position protruding from the magnetized surface. That is, in the first embodiment, the molding material 2 is inserted into the through hole 4 and is placed at a predetermined position.
Although the magnet 3 and the magnet 3 are adhered to each other, the through hole 17 is used in this embodiment.
Positioning is performed by the steps of the molding material 18.

FIG. 20 shows a sectional view of the bias magnet 16, FIG. 21 shows a plan view of the molding material 18, and FIG.
A side view of the molding material 18 is shown in FIG. As shown in FIG. 20, a through hole 17 is formed in the bias magnet 16, and the through hole 17 has a thin leading end and a thick rear end. That is, the step 17a serving as a fitting portion in the through hole 17,
17b is provided. Also, as shown in FIGS.
The molding material 18 has a thin front end and a thick rear end. That is, the step 1 that becomes the fitting portion on the molding material 18
8a and 18b are provided. And the bias magnet 16
The molding material 18 is inserted into the through hole 17 and inserted, and the positioning is performed at the position where the stepped portion of the through hole 17 and the stepped portion 17a, b and 18a, b of the molding material 18 abut.

In this way, the molding material 18 is inserted into the through hole 17
When the magnetic resistance element 19 is inserted into the bias magnet 16
Through hole 1 so that it stops at the position protruding from the magnetized surface of
7 and the molding material 18 were stepped. Therefore, the positional relationship between the sensor element (magnetoresistive element 19) and the bias magnet 16 can be easily managed only by inserting the molding material 18 into the through hole 17. Also, the molding material 18 and the magnet 1
Since both 6 can be manufactured by molding, the positions of the sensor element (magnetoresistive element 19) and the bias magnet 16 can be easily controlled during mass production, and the sensor element (magnetoresistive element 1 can be stably operated.
The positional relationship between 9) and the bias magnet 16 can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a magnetic rotation detection device according to a first embodiment.

FIG. 2 is a plan view of a magnetic rotation detection device.

FIG. 3 is a view on arrow A in FIG.

FIG. 4 is a front view of a sensor element.

FIG. 5 is a diagram showing a magnetoresistive element of an experimental sample.

FIG. 6 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 7 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of change in resistance.

FIG. 8 is a diagram showing the relationship between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 9 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 10 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 11 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 12 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 13 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 14 is a diagram showing the relationship between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 15 is a relationship diagram between the arrangement of magnetoresistive elements and the rate of resistance change.

FIG. 16 (a) is a diagram showing the relationship between the air gap having a small hollow opening area and the arrangement of magnetoresistive elements. (B) It is a relational diagram of the air gap with a large hollow-shaped opening area, and arrangement | positioning of a magnetoresistive element.

FIG. 17 is a schematic configuration diagram of a magnetic rotation detection device according to a second embodiment.

FIG. 18 is a view on arrow C in FIG. 20.

FIG. 19 is a view on arrow D in FIG. 20.

FIG. 20 is a cross-sectional view of a bias magnet.

FIG. 21 is a plan view of a molding material.

FIG. 22 is a front view of a molding material.

FIG. 23 is a perspective view of a bias magnet.

[Explanation of symbols]

2 mold material 3 bias magnet 5 gear to be detected 7 having magnetic material 7, 8 magnetoresistive elements 3a, 3b surface position of bias magnet 3 with respect to magnetoresistive elements 7, 8

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

Claims (4)

[Claims] 1. A bias magnet that generates a bias magnetic field toward a detection target having a magnetic material; and a magnetoresistive element that causes a resistance change by the bias magnetic field according to the motion of the detection target. A magnetic detection device configured to detect a change in the state of the bias magnetic field by a change in the resistance value of a resistance element, wherein the bias magnet has a hollow shape, and the magnetic resistance element is arranged so as to penetrate the hollow portion, Further, the magnetic detection device is arranged such that a part or just the whole of the magnetoresistive element is projected from a hollow portion of the bias magnet to a surface of the bias magnet facing the object to be detected. 2. A bias magnet that generates a bias magnetic field toward a detection target having a magnetic material, and a magnetoresistive element that causes a resistance change by the bias magnetic field according to the motion of the detection target. A magnetic detection device configured to detect a change in the state of the bias magnetic field by a change in the resistance value of a resistance element, wherein the bias magnet has a hollow shape, and the magnetic resistance element is arranged so as to penetrate the hollow portion, Moreover, the magnetic detection device is arranged so that the entire magnetoresistive element is immersed in the hollow portion of the bias magnet from the surface of the bias magnet facing the detection target. 3. The magnetoresistive element has at least one pattern that is patterned so that an angle formed by the hollow portion of the bias magnet and the hollow direction is approximately 45 °. Item 1. The magnetic detection device according to Item 1 or 2. 4. A protective member for protecting the magnetoresistive element, and the protective member and the bias magnet having a hollow portion have fitting portions that are fitted to each other. 3. The magnetic detection device according to any one of 3.