JPH10332733A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized acceleration sensor which can accurately detect only acceleration in the measurement direction. SOLUTION: In a frame 1, a guide pole 2 is provided having a sliding face 10 along the direction of the acceleration to be measured, and a moving body 3 is provided which moves along the sliding face 10 of this guide pole 2. A permanent magnet 4 is mounted on this moving body 3. A holding spring 5 is provided between the moving body 3 and the frame 1, and the moving body 3 is held at the reference position of the sliding face 1, and a magnetic sensor 6 is provided on the frame 1 opposing the permanent magnet 4. When acceleration is applied, the moving body 3 is moved in the axial direction along the sliding face of the guide pole. By this movement in the axial direction, the position of the permanent magnet 4 is changed, the change in a leakage magnetic field generated by the change is detected by the magnetic sensor 6, and the acceleration applied to the above permanent magnet is calculated from the detected value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor, such as a magnetoresistive element and a Hall element, which faces a permanent magnet.
The present invention relates to an acceleration sensor that detects an acceleration by a change in a magnetic sensor output according to a mutual displacement amount due to the acceleration.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor for detecting acceleration by using a magnetic sensor is disclosed in, for example, Japanese Patent Publication No. 7-7012, in which a tip portion or both ends of a cantilever made of a material which is bent by acceleration. A permanent magnet is attached to the center of the beam, and a magnetoresistive element opposed to the permanent magnet is provided on both sides of the permanent magnet at symmetrical positions, and the acceleration is calculated by adding the outputs of both magnetic sensors. I have. That is, as shown in FIG. 12, a permanent magnet 32 is attached to the tip of a flexible beam 31 that is fixed to one side and bent by acceleration,
The magnetic sensors 33 and 34 such as magnetoresistive elements are arranged at symmetrical positions so as to face the permanent magnet 32, and the flexible beam 31 bends due to the acceleration, and the permanent magnet 32 having the mass m moves and moves with respect to the magnetic sensors 33 and 34. When the displacement x occurs,
The acceleration G is detected by G = kx / m (k is a proportional constant). The magnetic sensor 3
3 and 34 are provided at symmetrical positions, and both detection signals are added to the adder 35 with opposite polarities to obtain a double output. Further, as shown in FIG. 13, both ends of the flexible beam 31 are supported, and permanent magnets 32, 32 are provided on both surfaces of the central portion, and the magnetic sensors 33, 34 are fixed to the fixed portions so as to face the permanent magnets 32, 32, respectively. In addition, there has been proposed a configuration in which both outputs are added with opposite polarities.

[0003]

However, in such a conventional structure, the permanent magnet 32 provided at the tip of the cantilevered flexible beam 31 has an arc shape centered on the root of the flexible beam 31. Since the movement of the permanent magnet 32 with respect to the magnetic sensors 33 and 34 does not move linearly with respect to the acceleration to be measured because the movement of the permanent magnet 32 with respect to the magnetic sensors 33 and 34 is included, acceleration components other than the measurement direction are included and measurement accuracy is reduced. Influence, as the displacement of the flexible beam 31 increases as in the case where a large acceleration is applied, the influence increases. In addition, when the flexible beam 31 is a doubly supported beam having a plate shape and supported at both ends, and a permanent magnet 32 is attached to a central portion, the permanent magnet can be displaced only in a single direction. However, since both ends of the flexible beam 31 are supported, the flexure against acceleration is small, and it is necessary to lengthen the flexible beam to increase the measurement sensitivity. Not
When stress is applied in the longitudinal direction of the flexible beam due to thermal expansion or the like, there is a disadvantage that the proportionality constant changes and an error occurs in the detected value.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a small acceleration sensor capable of accurately detecting only acceleration in a measurement direction.

[0004]

For this purpose, a sliding surface having the axis of the direction of the measured acceleration as an axis is provided on the casing, and a permanent magnet is attached to a movable body moving along the sliding surface. A magnetic sensor mounted on the casing facing the magnet; and a holding spring for holding the movable body at a reference position on the sliding surface, wherein the movable body is moved along the sliding surface against the holding spring by acceleration. By sliding the permanent magnet and the magnetic sensor, the facing position between the permanent magnet and the magnetic sensor is linearly displaced, and a change in the output of the magnetic sensor according to the amount of displacement is detected to calculate the acceleration. Note that the sliding surface is an outer peripheral surface of a guide column provided with the direction of acceleration measured in the casing as an axis,
It is constituted by an inner peripheral surface of a guide cylinder surrounding a movable body formed in a casing, and a linear bearing can be provided on this sliding surface.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A container frame having a sliding surface along the direction of the acceleration to be measured, a movable body having a permanent magnet attached and moving along the sliding surface, and a container facing the permanent magnet. A magnetic sensor attached to the frame is provided, the movable body is held at a reference position on the sliding surface by a holding spring, and when the movable body is moved along the sliding surface against the holding spring by acceleration, The facing position between the permanent magnet and the magnetic sensor changes linearly in the direction to be measured, an output corresponding to the displacement is obtained from the magnetic sensor, and the acceleration is calculated based on the output change. In addition, the sliding surface of the container frame and the movable body
A guide column is provided in the direction of the acceleration to be measured in the casing, and is inserted into the hole of the movable body and slid, or the acceleration of the guide tube provided in the casing or the inner peripheral surface of the casing itself is measured. The outer peripheral surface of the movable body is slidably fitted to the sliding surface. Alternatively, the movable body and the holding spring may be fixed, and the inner or outer circumference of the holding spring may be slidably fitted to the sliding surface of the casing.

[0006] Further, holding springs inserted between the movable body and the frame are provided on both end faces of the movable body fitted to the guide pillar or the guide cylinder, and both holding springs are opposed to the movable body. The movable body is held at a position where the movable body is balanced by acting in the direction, and one of them is compressed and the other is expanded according to the direction of acceleration to move the movable body based on this balanced position, and the displacement is detected by the magnetic sensor. If you calculate the acceleration,
The acceleration sensor can be installed at an angle or in a horizontal direction. In addition, permanent magnets are provided at both ends of the movable body so as to face the magnetic sensor, or permanent magnets are provided on the side face so that two magnetic sensors face each other. Can be eliminated, and a linear bearing can be provided on the sliding portion to smoothly move the movable body. In addition, by providing the buffering means on the surface of the magnetic sensor facing the permanent magnet, strong impact with the permanent magnet is eliminated, damage to the magnetic sensor is prevented, and a long-life acceleration sensor is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 is a side sectional view showing a first embodiment, 1 is a container frame, 2 is a guide post, which is provided in the container frame 1 in the direction of the acceleration for measuring the axis (the direction of the arrow in the figure). A sliding surface 10 is formed on the outer peripheral surface. Reference numeral 3 denotes a movable body slidably inserted through the guide column 2, and a permanent magnet 4 is attached to an upper end surface thereof.
A holding spring 5 that supports the movable body 3 around the guide column 2 is provided on the lower end surface. As the permanent magnet 4, any disc-shaped, ring-shaped or thin-film magnet such as a ferrite magnet or a rare earth magnet can be used. Numeral 6 denotes a magnetic sensor facing the permanent magnet 4 attached to the movable body 3, which is fixed to the upper inner surface of the casing 1 around the guide column 2, and uses a magnetoresistive element, a Hall element, a flux gate, or the like. Have been. Numeral 7 denotes an arithmetic unit for calculating acceleration from the output of the magnetic sensor. At least the sliding surfaces of the guide column 2 and the movable body 3 are made of a low-friction, low-wear solid lubricant. Therefore, when the acceleration G is applied from above, the movable body 3 moves upward along the sliding surface 10 of the guide column 2 by inertia according to the magnitude of the acceleration, and extends the holding spring 5 to move the permanent magnet 4. The distance between the magnetic sensor 6 and the magnetic sensor 6 is reduced. For this reason, the output of the magnetic sensor 6 due to the leakage magnetic field of the permanent magnet 4 increases, and this output change is input to the calculator 7 to determine the magnitude of the acceleration G as G = kx / m (k is a proportional constant including a spring constant). ). When acceleration is applied from below, the movable body 3 compresses the holding spring 5 while the sliding surface 10
Along with the magnetic sensor 6, the distance between the permanent magnet 4 and the magnetic sensor 6 increases, and the output of the magnetic sensor decreases, and the calculator 7 calculates the acceleration based on this output change. In the above operation, since the movable body 3 slides and moves along the sliding surface 10 of the guide column 2 only in the acceleration measurement direction, no acceleration component other than the measurement direction is detected, and the mass of the movable body and Since the spring constant of the holding spring can be appropriately selected, a small and accurate acceleration sensor can be obtained.

FIG. 2 is a side sectional view showing a second embodiment.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and the guide post 2 is shortened and provided fixed at one end in the casing 1.
Of the movable body 3 is slidably fitted into the guide post 2 so that the bottom of the concave hole 8 and the guide post 2 The tip is provided with a gap so that it does not contact when acceleration is applied. In this embodiment, a large permanent magnet can be attached to the upper surface of the movable body 3 in the same manner as the embodiment of FIG. 1, and the output of the magnetic sensor can be increased.

FIG. 3 shows a third embodiment, in which a guide tube 9 is provided in the casing 1, and the axis of the guide tube 9 is adjusted to the direction of the acceleration to be measured. Has formed.
A movable body 3 that slides along the sliding surface 10 is provided, a permanent magnet 4 is attached to an upper end surface of the movable body 3, and a holding spring 5 is provided between the lower end surface and the casing. 6 is the permanent magnet 4
A magnetic sensor 7 is attached to the inner surface of the casing in the guide tube 9 so as to face the. When acceleration is applied to the acceleration sensor, the movable body 3 extends or compresses the holding spring 5 according to the magnitude of the acceleration, and moves in the axial direction along the sliding surface 10 with the inner circumference of the guide cylinder 9. The distance between the permanent magnet 4 and the magnetic sensor 6 changes, and the leakage magnetic field of the permanent magnet 4 applied to the magnetic sensor 6 changes.
The output of the magnetic sensor 6 increases, and from this output change, the acceleration in only the axial direction of the guide cylinder 9 is detected from the calculator 7. In this embodiment, since the guide column 2 does not penetrate the portion where the permanent magnet 4 and the magnetic sensor 6 are mounted, a large permanent magnet can be mounted, or a sufficient mounting surface can be provided even if the movable body 3 is made small. Obtainable. In addition,
The guide cylinder 9 is not limited to a cylindrical one such as a cylindrical one, and a plurality of pillars are arranged at a cylindrical position, and sliding surfaces 10 are formed on inner surfaces of each other to allow the movable body to contact and slide. Alternatively, the inner peripheral surface of the container frame 1 itself may be used as the sliding surface 10.

FIG. 4 is a side sectional view showing a fourth embodiment.
A sliding surface 10 is formed below the casing 1 with a guide cylinder 11, and the movable body 3 having a smaller diameter than the holding spring 5 is connected via a connecting plate 12 to the holding spring 5 inserted into the guide cylinder 11. The outer periphery of the holding spring 5 slides along a sliding surface 10 formed on the inner peripheral surface of the guide cylinder 11. 4
Is a permanent magnet, 6 is a magnetic sensor, and 7 is a calculator. As described above, the outer peripheral surface of the holding spring 5 of the movable body 3 is configured to be slid in contact with the guide cylinder 11 provided with the sliding surface 10 in the measuring direction provided on the casing 1. There is an advantage that the contact surface of the movable portion that comes into contact with the sliding surface 10 can be reduced, and the frictional resistance is reduced. Note that a guide column may be provided instead of the guide cylinder 11 so as to be slid in contact with the inner peripheral surface of the holding spring.

FIG. 5 is a side sectional view showing a fifth embodiment, in which holding springs are provided at both ends of a movable body. 1 is a casing, 2 is a guide column provided in the direction of the acceleration measured in the casing 1, provided in the casing 1 in accordance with the direction of the acceleration for measuring the axis, and has a sliding surface 10 on the outer peripheral surface. Has formed. Reference numeral 3 denotes a movable body slidably inserted into the guide column 2, and permanent magnets 41 and 42 are attached to both end surfaces. Reference numerals 51 and 52 denote holding springs which surround the guide column 2 and support the movable body 3, and it is desirable to use springs having the same spring constant. 61 and 62 are magnetic sensors facing the permanent magnets 41 and 42, and 7 is a calculator. In this embodiment, when no acceleration is applied, the movable springs 3 are held at positions where the holding springs 51 and 52 are in equilibrium. When acceleration is applied, the movable body 3 holds one of the movable bodies 3 in accordance with the direction of the acceleration. The spring is compressed and the other holding spring is extended to move along the sliding surface 10 of the guide column 2, the output of each of the magnetic sensors 61 and 62 fluctuates, and the arithmetic unit 7 detects the output of each of the magnetic sensors 61 and 62. By calculating and detecting the direction and magnitude of the acceleration in the axial direction, and adding both output signals, the effects of temperature drift and magnetic noise can be eliminated. Note that, depending on the specifications of the acceleration sensor, the permanent magnet and the magnetic sensor on one side of the movable body can be omitted.

FIG. 6 shows a sixth embodiment in which a linear sliding bearing is provided on the sliding surface between the guide column and the movable body so that the movable body 3 slides smoothly, and a permanent magnet is attached to the side surface of the movable body. This is an example. 1 is a frame, 2 is a guide column provided in the direction of the acceleration measured in the frame 1, 3 is a movable body, which is fitted to the guide column 2 via a linear sliding bearing 13; Move axially along. 4 is a permanent magnet attached to the side surface of the movable body 3, 51 and 52 are holding springs inserted between both ends of the movable body 3 and the inner surface of the casing 1, and 61 and 62 are magnets provided on the inner peripheral face of the casing 1. A sensor is provided at a position facing the permanent magnet 4 and distributed in the movement direction. 7 is an arithmetic unit. The movable body 3 in this embodiment operates in the same manner as the embodiment in FIG. 5, but the frictional resistance of the sliding surface 10 is reduced by the linear sliding bearing 13, and the movement of the movable body 3 is performed smoothly. Such a linear sliding bearing can be used in any of the above-described embodiments.

FIG. 7 shows a seventh embodiment in which a linear rolling bearing 14 is provided on the sliding surface between the guide column 2 and the movable body 3 in the embodiment of FIG. 5, so that the movable body 3 slides smoothly. Thus, the accuracy of acceleration detection is improved, and the operation is the same as in the embodiment of FIG. In addition, 1 is a casing, 41 and 42 are permanent magnets attached to both end faces of the movable body 3, 51 and 52 are provided between both end faces of the movable body 3 and the inner face of the casing 1 surrounding the guide column 2, Holding springs 61 and 62 for supporting the movable body 3 are magnetic sensors facing the permanent magnets 41 and 42.

FIG. 8 shows an eighth embodiment, in which a linear rolling bearing 14 is provided on the guide column 2 in place of the linear sliding bearing in the embodiment of FIG. 6 so that the movable body 3 can slide smoothly. , And operates similarly to the embodiment of FIG. In addition, 1 is a frame, 4 is a permanent magnet attached to the side of the movable body 3, 51,
52 is a holding spring that surrounds the guide column 2 and supports the movable body 3;
Reference numerals 61 and 62 denote magnetic sensors provided at positions allocated to the permanent magnet 4 in the moving direction. Note that such a linear rolling bearing is not limited to the embodiment shown in FIGS. 7 and 8, and can be used for the sliding surface of another embodiment.

FIG. 9 shows a ninth embodiment. In this embodiment, a linear rolling bearing 14 is provided on the inner peripheral surface of a guide cylinder 15 provided on the casing 1.
The movable member 3 is inserted through the fixed portion of the linear rolling bearing 14 provided on the guide cylinder 15 and the spring receivers 1 at both ends of the movable member 3.
The movable body 3 is held at an equilibrium position of the holding spring by interposing holding springs 51 and 52 between the movable spring 3 and the movable spring 3. 41, 42
Are permanent magnets attached to both end surfaces of the movable body 3, 61 and 62
Is a magnetic sensor provided on the casing 1 so as to face the permanent magnet. When no acceleration is applied, the holding spring 5
1 and 52 hold the movable body 3 at a balanced position. When acceleration is applied, the movable body 3 compresses one of the holding springs and expands the other holding spring according to the direction of the acceleration to guide the guide pillar 2. Moves along the linear rolling bearing 14, one of the permanent magnets 41 and 42 moves away from the facing magnetic sensor, and the other approaches the other magnetic sensor. As a result, the outputs of the magnetic sensors 61 and 62 fluctuate with each other, and the direction and magnitude of the moving axial acceleration are calculated and detected based on both detection signals. The permanent magnet and the magnetic sensor may be provided on only one side, and the linear rolling bearing 14 may be a linear sliding bearing.

FIG. 10 is a tenth embodiment showing an example in which the magnetic sensor is provided with a buffer means. Reference numeral 1 denotes a casing provided with a guide cylinder 9. The movable body 3 is fitted with the outer peripheral surface of the guide cylinder 9 as a sliding surface 10, and a holding spring 5 supporting the movable body 3 is connected to the guide cylinder 9. It is arranged inside and held by the spring seat 17. Reference numeral 4 denotes a permanent magnet attached to the movable body 3, and reference numeral 6 denotes a magnetic sensor provided to face the permanent magnet 4. Numeral 20 denotes a buffering means for covering the surface of the magnetic sensor 6, which is composed of a coating layer 20a of a polymer coating material, for example, an epoxy resin. When the permanent magnet 4 moves together with the movable body 3 when the acceleration is applied and hits the magnetic sensor 6, a large shock is applied to the magnetic sensor 6 by the mass of the movable body 3, and the magnetic sensor may be damaged. For this reason, a buffer means 20 for covering the magnetic sensor 6 is provided to reduce the impact with the permanent magnet 4 and protect the magnetic sensor. According to the results of the experiment, in the acceleration sensor without the buffer means 20, when the acceleration twice the rated value was applied ten times, the output signal became abnormal. However, the buffer means 20 comprising the epoxy resin coating layer 20a was abnormal. Provided, a normal output signal could be obtained even if acceleration was detected under the same conditions. Note that the buffer means 2
If a material having excellent thermal conductivity, for example, a heat-dissipating silicon compound manufactured by Dow Corning, is used for the coating layer 20a constituting 0, there is also obtained an advantage that the drift of the output signal at high temperatures is reduced.

FIG. 11 shows an eleventh embodiment showing another embodiment of the buffer means 20, which is constructed in the same manner as the embodiment of FIG. 9, and is applied to an acceleration sensor in which the movable body 3 is provided with the linear rolling bearing 14. In the example, the same parts as those in FIG. 9 are denoted by the same reference numerals. The buffer means 20 in this embodiment is constituted by a non-magnetic thin plate 20b such as a SUS316 foil or a Mylar film, which is stretched between the permanent magnet 4 and the magnetic sensor 6 through a gap close to the magnetic sensor. I have. Therefore, when the movable body 3 moves due to acceleration, the permanent magnet 4
Before hitting the magnetic sensor 6, the magnetic sensor 6 is buffered by hitting the thin plate 20b of the buffer means 20 stretched through the gap with the magnetic sensor 6, and the magnetic sensor 6 can be protected. As a result of performing the detection 100 times by applying the double acceleration, no abnormality was detected in the detection of the acceleration. When the SUS316 foil was used, no abnormality occurred even when the acceleration 100 times was applied 1000 times.

[0018]

As described above, according to the present invention, a casing having a sliding surface in a direction for measuring acceleration, a movable body having a permanent magnet and moving along the sliding surface, and a movable body facing the permanent magnet are provided. A magnetic sensor attached to the casing, and a holding spring for holding the movable body at a reference position on the sliding surface, wherein the movable body moves from the reference position against the holding spring by acceleration. By displacing the position where the permanent magnet and the magnetic sensor face each other, the permanent magnet is moved in a linear direction along the sliding surface when acceleration is applied. The acceleration value other than the linear direction is not included in the detection value of the above, and it is possible to detect an accurate acceleration only in the measurement direction, to obtain a compact and high-performance acceleration sensor. Setting There can be effectively. In addition, since the movable body is moved linearly, displacement due to acceleration is smooth, and by providing a linear sliding bearing or a linear rolling bearing on the sliding surface, resistance during movement can be further reduced, and quick and accurate detection can be performed. It can be performed. Also,
Since the movable body is supported in the axial direction of the frame, two sets of magnetic sensors can be installed with permanent magnets on both ends of the movable body, or easily installed on the side surface, so that drift due to temperature and the effects of magnetic noise are easy. There is an advantage that the structure can be eliminated. In addition, by providing a buffer means in the magnetic sensor,
By preventing the permanent magnet that moves due to acceleration from directly hitting the magnetic sensor, the magnetic sensor is protected from impact, and stable detection can be performed without causing any abnormality in several other detections. The effect of increasing the life of the sensor is obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a second embodiment of the present invention.

FIG. 3 is a side sectional view showing a third embodiment of the present invention.

FIG. 4 is a side sectional view showing a fourth embodiment of the present invention.

FIG. 5 is a side sectional view showing a fifth embodiment of the present invention.

FIG. 6 is a side sectional view showing a sixth embodiment of the present invention.

FIG. 7 is a side sectional view showing a seventh embodiment of the present invention, in which a part of a guide column is sectioned.

FIG. 8 is a side sectional view showing an eighth embodiment of the present invention, in which a part of a guide column is sectioned.

FIG. 9 is a side sectional view showing a ninth embodiment of the present invention.

FIG. 10 is a side sectional view showing a tenth embodiment of the present invention.

FIG. 11 is a side sectional view showing an eleventh embodiment of the present invention.
A part of the movable body is shown in cross section.

FIG. 12 is a side sectional view showing a conventional example.

FIG. 13 is a side sectional view showing another example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Package 2 Guide pillar 3 Movable body 4, 41, 42 Permanent magnet 5, 51, 52 Holding spring 6, 61, 62 Magnetic sensor 7 Computing unit 8 Concave hole 9 Guide cylinder 10 Sliding surface 11 Guide cylinder 12 Connection plate 13 Linear sliding bearing 14 Linear rolling bearing 15 Guide cylinder 16 Spring receiver 17 Spring seat 20 Buffer means 20a Coating layer 20b Thin plate 31 Flexible beam 32 Permanent magnet 33, 34 Magnetic sensor 35 Adder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Hiroshi Hamamatsu 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City, Fukuoka Prefecture Inside Yaskawa Electric Co., Ltd. (72) Inventor Akihiro Nomura 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City, Fukuoka Prefecture Yaskawa Electric Corporation

Claims (11)

[Claims] A permanent magnet that is displaced by acceleration and a magnetic sensor provided to face the permanent magnet; a change in a leakage magnetic field caused by the displacement of the permanent magnet is detected by a magnetic sensor; In an acceleration sensor for calculating an acceleration applied to a magnet, a casing having a sliding surface along a direction of the measured acceleration, a movable body including a permanent magnet and moving along the sliding surface, And a holding spring for holding the movable body at a reference position on the sliding surface, and sliding the movable body from the reference position against the spring by acceleration. An acceleration sensor that displaces a facing position between a permanent magnet and a magnetic sensor by moving along a moving surface. 2. A guide column having a sliding surface formed on the outer periphery of the container frame with the direction of acceleration to be measured as an axis, wherein a movable body is inserted through the guide column, and The acceleration sensor according to claim 1, wherein a movable body is moved along the sliding surface of the guide column. 3. A guide hole having a sliding surface formed on the outer periphery thereof with the direction of acceleration to be measured as an axis, and a concave hole for inserting the guide post into a movable body is provided inside the casing. The acceleration sensor according to claim 1, wherein the movable body is moved along the sliding surface on the inner peripheral surface of the concave hole according to the condition. 4. A guide cylinder having a sliding surface formed on the inner peripheral surface thereof with the direction of acceleration to be measured as an axis, and a movable body is inserted into the guide cylinder inside the casing. 2. The acceleration sensor according to claim 1, wherein the movable body is moved along the sliding surface of the guide cylinder in accordance with the following. 5. A guide cylinder having a sliding surface formed on an inner peripheral surface thereof with the direction of acceleration to be measured as an axis, and a holding spring attached to a movable body is provided in the guide cylinder. The acceleration sensor according to claim 1, wherein the acceleration sensor is inserted, and the holding spring expands and contracts along the sliding surface according to the acceleration. 6. The holding spring is inserted between the movable body and the frame on both sides of the movable body, one of which is compressed and the other is extended to move the movable body according to the direction of acceleration. 6. The acceleration sensor according to any one of 1 to 5. 7. The acceleration sensor according to claim 1, wherein a linear sliding bearing is provided between a sliding surface of the casing and a surface of the movable body that contacts the sliding surface. 8. The acceleration sensor according to claim 1, wherein a linear rolling bearing is provided between a sliding surface of the casing and a surface of the movable body that contacts the sliding surface. 9. The acceleration sensor according to claim 1, wherein a buffer is provided on a surface of the magnetic sensor facing the permanent magnet. 10. The acceleration sensor according to claim 9, wherein the buffer means is a coating layer of a polymer coating material covering a surface of the magnetic sensor. 11. The non-magnetic thin plate as set forth in claim 9, wherein the buffer means is a non-magnetic thin plate between the permanent magnet and the magnetic sensor, which is moved by the permanent magnet stretched through a gap between the permanent magnet and the magnetic sensor. Acceleration sensor.