JP2000249573A - Magnetic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance S/N ratio of detection output through simple arrangement by setting the magnetic detecting position of an electromagnetic conversion element at a position where a high output can be obtained with low distortion of detection signal. SOLUTION: A bias magnet 12 is disposed in front of a mover 11 while spaced apart therefrom by a specified interval. An electromagnetic conversion element MR 13 is disposed in the bias field of the bias magnet 12 in order to convert the bias field variable according to the movement of the mover 11 into an electric signal. The bias magnet 12 has magnet parts 12a, 12b arranged on the opposite sides of a spacer 12c in the moving direction of the mover 11. Corresponding parts of the magnet parts 12a, 12b in same direction are magnetized with opposite polarities. The MR element 13 is shifted slightly from the center of the spacer 12c. The MR element 13 is shifted to approach one side of the magnet parts 12a, 12b and the center thereof is located in the low distortion region of the magnet parts 12a, 12b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetism detecting device which detects a change in a bias magnetic field by a magneto-electric conversion element and outputs it.

[0002]

2. Description of the Related Art Various types of magnetic detectors have been widely used in motor control devices and the like. For example,
As shown in FIG. 6, in a magnetic detection device using a magnetoresistive element (MR element) 1 whose resistance value changes according to a magnetic field, a pair of magnet parts 2 a and 2
b are arranged so as to sandwich the magnetic detection position P at which the magnetic field is to be detected, and the pair of magnet portions 2a,
The change in the bias magnetic field formed at the magnetic detection position P by 2b is detected by the magnetoresistive element (MR element) 1 arranged at the magnetic detection position P and is output as a predetermined electric signal.

At this time, the above-mentioned magnetoresistive element (MR element)
1 is a pair of magnet parts 2a, 2 constituting the bias magnet 2.
The bias magnet 2 is disposed at a portion between the b, that is, the center position of the bias magnet 2, and the center position is set as the magnetic detection position P.

[0004]

However, in the conventional magnetic detecting device in which the magneto-electric conversion element 1 is arranged at the center position of the bias magnet 2, distortion in a detection signal becomes large, and furthermore, a weak output is obtained. It has been found that the so-called S / N ratio is not good and a highly accurate output signal cannot be obtained.

It is an object of the present invention to provide a magnetic detecting device capable of obtaining a good detection signal with a simple and inexpensive configuration.

[0006]

According to the present invention, there is provided a bias magnet arranged near a magnetic detection position where a magnetic field is to be detected to form a predetermined bias magnetic field at the magnetic detection position. A magneto-electric conversion element including a sensor unit that converts a change in a bias magnetic field at a magnetic detection position into an electric signal and outputs the electric signal, wherein the bias magnet is disposed so as to sandwich the magnetic detection position. In the magnetic detection device including (1), the sensor unit of the magnetoelectric conversion element is arranged so as to be biased so as to be located on one side of the pair of magnet units.

According to the present invention having such a configuration,
The magnetic detection position of the magneto-electric conversion element is set at a position where the distortion rate of the detection signal is small and a relatively high output can be obtained. By simply changing the position of the magneto-electric conversion element, the S / N ratio of the detection output can be reduced. Dramatically improved.

That is, as shown in FIG. 2, the sensor portion 13c of the magneto-electric conversion element 13 is displaced from the center position of the bias magnet 12, and as shown in FIG. Displacement amount γ of the sensor unit 13c
(Horizontal axis: mm) and the sensor unit 1 of the magnetoelectric conversion element 13
3c, the output value at the center position of the bias magnet 12 was the most irrespective of the detection gap δ between the bias magnet 12 and the magnetoelectric conversion element 13. Small, bias magnet 12
It has been found that the maximum output is obtained in the region on the front side of each of the magnet portions 12a and 12b, which is the end side.

Next, as shown in FIG. 5, the displacement γ (horizontal axis: mm) of the sensor unit 13c of the magneto-electric conversion element 13 from the center position of the bias magnet 12 is compared with the magneto-electric conversion. The distortion rate κd (vertical axis:%) in the output signal of the sensor unit 13c of the element 13 was examined (detection gap δ = 100 μm, bias gap δ _b = 2.4 m).
m), the distortion rate at the center position of the bias magnet 12 is extremely high, and drops sharply on both sides of the center position.
It can be seen that the number has rapidly increased again in the front side areas of a and 12b.

The above-mentioned distortion rate κd is defined by the following equation.

(Equation 1) Where V _1/2 is a １ ／ order component, V ₁ is a fundamental wave component,
V _n is the n-th harmonic (n = 2,3,4, ···) is a component.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a linear movement type magnetic detecting device will be described below in detail with reference to the drawings. As shown in FIGS. 1 and 2, the mover 11 as a detection target is formed of an elongated plate-like member extending substantially linearly, and is moved in the longitudinal direction (x direction) of the mover. It is configured to reciprocate. On the front surface (the right side surface in FIG. 1) of the mover 11, uneven tooth portions 11 are formed along the moving direction (x direction).
a are provided in parallel with each other, and a bias magnet 12 for forming a predetermined bias magnetic field with respect to the uneven shape of the teeth 11 a is provided at a predetermined distance (y from the front side of the movable element 11. Direction).

Further, in a bias magnetic field formed by the bias magnet 12, an MR as a magnetoelectric conversion element is provided.
An element 13 is disposed, and a change in the bias magnetic field that changes with the movement of the mover 11 is detected by the MR element 13.
To convert the signal into an electric signal and output the electric signal. The MR element 13 as this magnetoelectric conversion element
For the uneven tooth portion 11a on the front side of the mover 11,
The bias gap δ _b (y direction) is provided between the MR element 13 and the bias magnet 12 while being arranged so as to interpose a predetermined detection gap δ (y direction).

As the MR element 13 in the present embodiment, a stripe type element as shown in FIG. 3 is particularly employed. The stripe-type MR element 13 is provided with, for example, an exposed electrode portion 13b on a glass substrate 13a having a thickness of 0.4 mm.
b, a sensor portion (magnetically sensitive conductive path portion) 13c made of a strip-shaped permalloy material is formed so as to extend in a vertically long direction (z direction), and the sensor portion 1 is formed.
From the extended end (upper end in the figure) of 3c, a lead electrode portion 13d made of a wide permalloy material is connected to the sensor portion 13c.
And extend substantially in parallel. A leading end portion (a lower end portion in the drawing) of the extraction electrode portion 13d is formed on the exposed electrode portion 13e.

It should be noted that the MR element 13 as a magnetoelectric conversion element to which the present invention is applied is not limited to the above-described structure having the single sensor section 13c, and is not limited to the conventional one having a large number of sensor sections. The present invention can be similarly applied to a known stripe structure.

At this time, the sensor section 1 of the MR element 13
The geometric center portion 3c of FIG. 3c is set at a magnetic detection position where a magnetic field is to be detected.
It is arranged so as to have a predetermined positional relationship with the bias magnet 12 described above. Hereinafter, the bias magnet 12
Of the MR element 13 with respect to the bias magnet 12
It will be described together with the detailed structure of.

First, the bias magnet 12 is particularly shown in FIG.
As shown in FIG. 2, the magnet has a pair of magnet parts 12a and 12b. The pair of magnet portions 12a and 12b are arranged so as to sandwich a spacer 12c made of a non-magnetic material such as an aluminum material from both sides, and the pair of magnet portions 12a and 12b and the spacer 12c are arranged by the mover. 11 are arranged along the moving direction (x direction). Further, the magnet portions 12a and 12b are formed so as to have substantially the same width in the moving direction (x direction) of the mover 11, and these magnet portions 12a and 12b are formed.
In FIGS. 12A and 12B, portions corresponding to the same direction (x direction) are magnetized so as to have opposite polarities, so that the magnetic detection position P described above, that is, the sensor unit of the MR element 13 is used. A predetermined bias magnetic field is formed with respect to the geometric center of 13c.

At this time, the arrangement position of the MR element 13 is set slightly shifted in the x direction from the center position SL of the spacer 12c. That is, the MR element 13 includes a pair of magnet portions 12a of the bias magnet 12,
12b (in this embodiment, the magnet portion 12a
Side), and the MR element 13 is arranged in the front side region of the magnet part 12a on one side. More specifically, the magnetic detection position P, which is the center of the sensor of the MR element 13, is within the range of the bias magnetic field formed by the magnet portions 12a and 12b, and the low distortion rate shown in FIG. Are arranged in the area. In this low distortion region, a relatively high output voltage is obtained as shown in FIG.

As described above, in the present embodiment, the MR element 13
Is set at a position where the distortion rate of the detection signal is low and a relatively high output is obtained, so that the magnetic detection position P can be simply changed by changing the position of the MR element 13.
The S / N ratio of the detection output is dramatically improved.

For example, if the required distortion rate κd is 15
%, The amount of displacement of the sensor section 13c of the MR element 13 may be set so as to obtain a distortion rate in a region below the 15% distortion boundary drawn in FIG. It will be. That is, as is apparent from FIG.
In this embodiment, the position of the MR element 13 that satisfies the distortion rate of 15% or less is closer to the center of the magnet parts 12a and 12b from the end side area near the spacer 12c in the front side area of each of the magnet parts 12a and 12b. Area (displacement: +
0.15 mm or more and +0.6 mm or less or -0.8 mm or more and -0.2 mm or less).

When the MR element 13 is displaced as described above, the output voltage of the MR element 13 fluctuates from FIG. 4 described above. For example, by employing an amplifier circuit, The output voltage from the MR element 13 may be adjusted to a desired voltage.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, in the above embodiment, the present invention is applied to a linear movement type magnetic detection device, but the present invention can be similarly applied to a rotation type magnetic detection device. Further, the magnetoelectric conversion element is not limited to the MR element 13 as in the above-described embodiment,
The present invention can be similarly applied to various other various magnetoelectric conversion elements.

[0023]

As described above, according to the present invention, the magnetic detection position in the magnetoelectric conversion element such as the MR element is set to a position where the distortion rate of the detection signal is low and a relatively high output is obtained. Since the S / N ratio of the detection output is improved with a simple configuration simply by changing the position of the element, the detection accuracy of the magnetic detection device is dramatically improved while maintaining good productivity. Can be.

[Brief description of the drawings]

FIG. 1 is an external perspective explanatory view illustrating a schematic configuration of a magnetic detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory plan view of the magnetic detection device shown in FIG. 1;

FIG. 3 is an explanatory front view showing a structure of an MR element used in the magnetic detection device shown in FIG. 1;

FIG. 4 is a diagram showing an output voltage characteristic with respect to a position of an MR element used in the magnetic detection device.

FIG. 5 is a diagram showing a distortion rate characteristic of an output voltage waveform with respect to a position of an MR element used in a magnetic detection device.

FIG. 6 is an explanatory plan view showing a schematic configuration of a conventional magnetic detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Movable element 11a Irregular tooth part 12 Bias magnet 12a, 12b Magnet part 12c Spacer 13 MR element (magnetoelectric conversion element) 13c Sensor part (magnetically sensitive conductive path part)

Claims (4)

[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 converts a change in the bias magnetic field at the magnetic detection position into an electric signal. A magneto-electric conversion element having a sensor part for outputting, wherein the bias magnet includes a pair of magnet parts arranged so as to sandwich the magnetic detection position, wherein the sensor part of the magneto-electric conversion element The magnetic detection device is arranged so as to be biased so as to be located on one side of the pair of magnet portions. 2. A method according to claim 1, wherein the pair of magnet parts are arranged on both sides of a spacer made of a non-magnetic member, and the sensor part of the magnetoelectric conversion element is positioned on the one magnet part side from the center of the spacer. 2. The magnetic detecting device according to claim 1, wherein the magnetic detecting device is arranged so as to be deviated to the direction. 3. The magnetism detecting device according to claim 1, wherein said magnetoelectric conversion element is arranged in a front side region of said one magnet part. 4. A pair of magnet parts are arranged side by side in a moving direction of a mover having uneven teeth, and each magnet part has substantially the same width in the moving direction of the mover. 4. The magnetic detection device according to claim 3, wherein the sensor unit of the magnetoelectric conversion element is disposed within a range of a bias magnetic field formed by the two magnet units in a front-side region of the two magnet units. apparatus.