JPH1010146A - Acceleration sensor provided with movable member with thin-film magnet and magnetizing device for thin-film magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the strength of the leaking magnetic field from a thin- film magnet reaching a magnetic sensor and to improve the adjustment as an acceleration operating part. SOLUTION: An acceleration sensor 1 is constituted of a stage 21 having a pyramid-shaped recess 21a, whose bottom surface is directed upward in the vertical direction, and a fixing member 2 comprising an elastic body 22 embedded in the pyramid-shaped recess 21a and a semispherical recess 22a provided on the upper surface of the elastic body 22. In this case, a sphere 3, which is the movable member, is held on the semispherical recess 22a. A thin-film magnet is formed on the surface of the lower half part of the sphere 3. At least one of magnetic sensors 5a, 5b, 5c and 4d is provided on each side surface of the pyramid-shaped recess 21a, respectively. Therefore, the strength of the magnetic field from the thin-film magnet reaching the magnetic sensor becomes uniform, and the accelerations in many directions can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration using a magnetic sensor such as a magnetoresistive element, and more particularly to an acceleration sensor having a movable member with a thin film magnet which is small and can detect a wide range. The present invention relates to a sensor and a thin film magnet magnetizing device.

[0002]

2. Description of the Related Art Hitherto, various acceleration sensors have been proposed which detect acceleration using a magnetic sensor such as a magnetoresistive element. For example, as shown in FIG. 5, a permanent magnet 13 attached to the tip of a bendable beam 12 and magnetic sensors 14 provided at symmetrical positions on both sides of the permanent magnet 13 are provided. When the acceleration G is applied to the magnetic sensor 14, the displacement amount of the permanent magnet 13 having the mass m with respect to the magnetic sensor 14 is x, and the proportionality constant is k. , Acceleration G, G = k
What is obtained as x / m is disclosed (for example, Japanese Patent Publication No. 7-7012). In addition, as an application example of the acceleration sensor, a combination of a movable member having various shapes and a magnetic sensor using a bulk or thin film magnet has been proposed.
An acceleration sensor including a movable member having a thin film magnet capable of detecting a wide range is one of them. In the magnetization of the thin film magnet, conventionally, as shown in FIG. 6, a movable member composed of a sphere 5 is used, and a thin film magnet 6 is formed on a hemispherical surface of the sphere 5, and first and second magnetizations are performed. Each of the yokes 8 and 9 had a flat contact surface with the sphere 5, and was magnetized with the sphere 5 interposed between the two magnetized yokes 8 and 9.

[0003]

However, in the acceleration sensor of the prior art, since the permanent magnet 13 is attached to the tip of the beam 12, once the acceleration G is applied to the beam 12, the acceleration G is applied to the beam 12. When residual vibrations remain and new vibrations are applied one after another, there is a problem that an accurate acceleration cannot be detected. Further, since the permanent magnet 13 is used, the size of the sensor cannot be reduced, and a wide range cannot be detected. Also, since the direction in which the deflection of the beam 12 can be detected is one direction sandwiching the beam 12, only one acceleration can be detected by one acceleration sensor. On the other hand, in the magnetizing device of the thin film magnet of the movable member provided in the acceleration sensor, when the thin film magnet 6 formed on the hemispherical surface of the sphere 5 is magnetized by the magnetizing device as shown in FIG. Since the magnetic field has anisotropy in the thickness direction, the magnetized magnetic field leaking from the second magnetized yoke 9 by the electromagnet coils 10 and 11 passes through the thin film magnet 6 and becomes the first magnetized magnetic field. When exiting to step 8, the magnetization can be sufficiently magnetized in a portion where the direction of the magnetizing magnetic flux is substantially parallel to the thickness direction of the thin film magnet 6, but as shown in FIG. In the part that forms an angle with the direction, the magnetization cannot be sufficiently magnetized because the direction of the magnetic flux does not match the direction of the anisotropy of the thin film magnet 6. Therefore, the magnetized thin film magnet 6
Are not uniformly magnetized over the whole, so that the thin film magnet 6
Since the intensity of the leakage magnetic field varies depending on the location, it is difficult to adjust the acceleration calculation unit for detecting the acceleration, and it is not possible to detect the acceleration with high accuracy. Further, the acceleration sensor disclosed in Japanese Patent Publication No. 7-7012, which is the above-mentioned known technique, has a unique feature. However, a movable member and a thin-film magnet having a thin-film magnet, which is a feature of the acceleration sensor of the present invention, are provided. Is not disclosed at all. Therefore, the first object of the present invention is to provide an acceleration sensor having a movable member with a thin-film magnet that has a small residual vibration, has a wide detection range, and can accurately detect acceleration in multiple directions, as a first object. It is in. It is a second object of the present invention to provide a thin film magnet magnetizing device that can make the intensity of a leakage magnetic field from a thin film magnet reaching a magnetic sensor uniform and improve adjustment in an acceleration calculation unit.

[0004]

Means for Solving the Problems To solve the above problems, the present invention has the following configuration. A fixed member, a movable member held by the fixed member, a permanent magnet provided on at least a part of the movable member, and a change in a leakage magnetic field caused by displacement of the movable member which is disposed to face the permanent magnet and is detected. An acceleration calculator that calculates an acceleration applied to the permanent magnet from an output change of the magnetic sensor, wherein the fixing member has a pyramid with a bottom surface directed upward in the vertical direction. A pedestal having a concave shape, an elastic body embedded in the pyramid-shaped concave portion, and a hemispherical concave portion provided on an upper surface of the elastic body, wherein the movable member is formed of a sphere held by the hemispherical concave portion. The permanent magnet is a thin-film magnet formed on at least the lower half surface of the sphere. Further, in the acceleration sensor having the movable member with the thin film magnet according to claim 1, at least one magnetic sensor is provided on each side surface of the pyramidal concave portion. Further, in the acceleration sensor provided with the movable member with a thin film magnet according to claim 1 or 2, the magnetic sensor comprises a magnetoresistive element. Claim 1
In the acceleration sensor provided with the movable member with a thin-film magnet described in 2 or 3, the magnetic sensor comprises a Hall element. Further, in the acceleration sensor provided with the movable member with the thin film magnet according to claim 1 or 2, the magnetic sensor is made of a flux gate. Further, the present invention is based on the following method. A movable member having a non-magnetized thin film magnet formed at least in part thereof, and a pair of magnetizing devices each including an electromagnet coil and a magnetizing yoke provided to face each other with both ends of the movable member interposed therebetween; A magnetizing device for magnetizing the thin film magnet by a magnetic field leaking from the magnetized yoke by supplying a current to the electromagnet coil, wherein the magnetized yokes provided at both ends of the movable member are provided. The shape of the end surface of the magnetized yoke facing the film forming surface side of at least one of the movable members has a shape so as to cover the surface of the movable member on which the thin film magnet is formed, and the magnetized yoke and the The movable member is provided closely. Further, in the thin film magnet magnetizing device according to claim 6, the movable member is a sphere.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the structure of the acceleration sensor according to the present embodiment. FIG. 2 is a side sectional view seen from the y direction in FIG. FIG. 3 is a side sectional view showing a magnetizing apparatus for a thin film magnet according to the present embodiment. FIG. 4 is a side view showing a magnetized state of the thin film magnet after the magnetization. First, the structure of the acceleration sensor will be described with reference to FIGS. In the acceleration sensor 1, reference numeral 2 denotes a fixed member, and 21 of the fixed members 2 is a gantry, the bottom surface of which is a square pyramid having an inclination angle of 45 ° in the center, with the bottom surface facing upward in the vertical direction and the vertex facing downward. Pyramidal recess 21
a is provided. Reference numeral 22 denotes an elastic body embedded in the pyramidal recess 21a of the gantry 21. A hemispherical recess 22a is provided at the center of the upper surface. Reference numeral 3 denotes a sphere having magnetism embedded and fixed in the hemispherical concave portion 22a, and a thin film magnet 4 is formed on the surface of the lower half. Numerals 5 (5a, 5b, 5c, 5d) denote magnetic sensors composed of magnetoresistive elements fixed to each side surface of the pyramidal recess 21a, and 6 denotes an acceleration calculator for calculating acceleration from the output of each magnetic sensor 5. In this case, the shortest distance from each of the magnetic sensors 5a, 5b, 5c, and 5d to the surface of the sphere 3 is set to be the same in the initial state.

When an acceleration is externally applied to the acceleration sensor having such a configuration, the sphere 3 is displaced by pressing the elastic body 22 in accordance with the magnitude of the acceleration. At this time, the sphere 3
The resistance of the magnetic sensor 5 is reduced by the leakage magnetic field generated by the thin film magnet 4 formed on the surface of the sphere 3 and the surface of the sphere 3.
The output from each of the magnetic sensors 5 changed according to the distance is input to the acceleration calculator 6, and the three-dimensional acceleration in each coordinate direction is calculated and output. For example, when the acceleration is applied in the x direction in FIG. 1, the acceleration in the x direction is detected by a change in the resistance balance between the magnetic sensors 5a and 5c. Similarly, in the y direction,
The acceleration can be detected by a change in the resistance balance between the magnetic sensors 5b and 5d. When acceleration is applied in the z direction, the acceleration in the z direction can be detected by a change in resistance of all the magnetic sensors 5a, 5b, 5c, and 5d. Thus, the acceleration in multiple directions can be accurately detected. Further, since the thin film magnet is provided on the movable member, the size of the sensor can be reduced, and the acceleration can be detected over a wide range. Further, by using a high-elasticity polymer material having high damping performance for the elastic body 22,
The residual vibration of the sphere 3 constrained by the elastic body 22 is extremely small as compared with the residual vibration of the beam as in the conventional example, and accurate acceleration can be detected. In the above embodiment, an example in which a magnetic resistance element is used for a magnetic sensor has been described. However, the same effect can be obtained by using a Hall element or a flux gate.

Next, a magnetizing device for a thin film magnet used in an acceleration sensor will be described with reference to FIGS. In the figure, reference numeral 7 denotes a magnetizing device, of which 8 and 9 are first and second magnetized yokes, and 8a is a first magnetized yoke 8
The spherical concave portions 10 and 11 provided on the end surfaces of the first and second electromagnet coils are first and second electromagnet coils. Reference numeral 3 denotes a sphere which is a movable member of the acceleration sensor, and reference numeral 4 denotes a thin film magnet formed on a hemisphere of the sphere 3. In such a configuration, first, the sphere 3 on which the unmagnetized thin film magnet 4 is formed is sandwiched between the first magnetized yoke 8 and the second magnetized yoke 9. At this time, the hemispherical surface of the sphere 3 on which the thin film magnet 4 is formed is placed so as to be almost in close contact with the spherical concave portion 8 a formed on the end face of the first magnetized yoke 8. Next, in this state, a current is supplied from a magnetizing power supply (not shown) to the first and second electromagnet coils 10 and 11 to magnetize the thin film magnet 4 formed on the hemisphere of the sphere 3. At this time, the magnetic flux emitted from the second magnetized yoke 9 passes through the inside of the thin film magnet 4 and escapes to the spherical concave portion 8a of the first magnetized yoke 8, but the magnetic flux that has entered the thin film magnet 4 at this time is In each part of the magnet 4, it passes so as to be substantially parallel to the thickness direction of the thin film magnet 4. Accordingly, since the magnetization of the thin film magnet 4 formed on the hemisphere of the sphere 3 is directed in the thickness direction, that is, in the radial direction of the sphere 3 at each portion, the thin film magnet 4 formed on the hemisphere of the sphere 3 is uniform throughout. Magnetized radially with strength. FIG. 4 shows the magnetized state of the thin film magnet 4 after magnetization, and the arrows in the figure show the direction and intensity of the magnetization. It was confirmed that the magnetized thin film magnet 4 was surely magnetized in each part with a uniform strength in the thickness direction. By using a sphere in which a thin film magnet is formed on a hemispherical surface uniformly magnetized in the thickness direction by the method of the present invention, by applying to the acceleration sensor described in the claims, a thin film magnet from the thin film magnet reaching the magnetic sensor is used. The strength of the leakage magnetic field becomes uniform, the adjustment in the acceleration calculation unit is easy, and a highly accurate acceleration sensor can be obtained.

[0008]

As described above, according to the present invention, a three-dimensional displacement of a sphere having a thin film magnet constrained by an elastic body is detected as a change in the resistance balance of the magnetic sensor and applied to the sphere. Because the obtained acceleration is obtained, a three-dimensional acceleration can be obtained by one acceleration sensor, and a small thin film magnet movable member capable of accurately detecting multidirectional acceleration over a wide area with little residual vibration. There is an effect of obtaining an acceleration sensor provided. In addition, since the thin film magnet formed on the spherical hemisphere is uniformly magnetized in the thickness direction, the strength of the leakage magnetic field from the thin film magnet reaching the magnetic sensor becomes uniform, and the acceleration calculation unit There is an effect of obtaining a thin-film magnet magnetizing device that can improve the adjustment in the above.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a structure of an acceleration sensor according to an embodiment.

FIG. 2 is a side sectional view seen from a y direction in FIG.

FIG. 3 is a side sectional view showing a magnetizing device for a thin film magnet according to the present embodiment.

FIG. 4 is a side view showing a magnetized state of the thin film magnet after magnetization.

FIG. 5 is a side sectional view showing a structure of an acceleration sensor showing a conventional example.

FIG. 6 is a side sectional view showing a conventional thin film magnet magnetizing apparatus.

FIG. 7 is a side view showing a magnetized state of a conventional thin film magnet after magnetization.

[Explanation of symbols]

 1: acceleration sensor 2: fixed member 21: pedestal 21a: pyramid-shaped recess 22: elastic body 22a: hemispherical recess 3: sphere 4: thin film magnet 5 (5a, 5b, 5c, 5d): magnetic sensor 6: acceleration calculation unit 7: magnetizing device 8: first magnetizing yoke 8a: spherical concave portion 9: second magnetizing yoke 10: first electromagnet coil 11: second electromagnet coil

Claims (7)

[Claims] 1. A fixed member, a movable member held by the fixed member, a permanent magnet provided on at least a part of the movable member, and a leakage generated by displacement of the movable member which is arranged to face the permanent magnet and is opposed to the permanent magnet. An acceleration sensor comprising: a magnetic sensor that detects a change in a magnetic field; and an acceleration calculator that calculates an acceleration applied to the permanent magnet from a change in output of the magnetic sensor. A pedestal having a pyramid-shaped concave portion facing upward, an elastic body embedded in the pyramid-shaped concave portion, and a hemispherical concave portion provided on an upper surface of the elastic body, wherein the movable member is provided in the hemispherical concave portion. An acceleration sensor comprising a movable member with a thin film magnet, wherein the permanent magnet is a thin film magnet formed on at least a lower half surface of the sphere. . 2. The acceleration sensor according to claim 1, wherein at least one magnetic sensor is provided on each side surface of the pyramidal concave portion. 3. The acceleration sensor according to claim 1, wherein the magnetic sensor comprises a magnetoresistive element. 4. The acceleration sensor according to claim 1, wherein the magnetic sensor comprises a Hall element. 5. The acceleration sensor according to claim 1, wherein the magnetic sensor comprises a flux gate. 6. A pair of a movable member having an unmagnetized thin film magnet formed at least in a part thereof, an electromagnet coil and a magnetized yoke provided to face each other across both ends of the movable member. And a magnetizing device for magnetizing the thin-film magnet by a magnetic field leaking from the magnetizing yoke by supplying a current to the electromagnet coil, provided at both ends of the movable member. Of the magnetized yokes, the shape of the end surface of the magnetized yoke facing the film forming surface side of at least one of the movable members has a shape that covers the surface of the movable member on which the thin film magnet is formed, A magnetizing device for a thin film magnet, wherein a magnetizing yoke and the movable member are provided in close contact with each other. 7. The thin film magnet magnetizing device according to claim 6, wherein the movable member is a sphere.