JPH0743377A - Accelerometer - Google Patents

Abstract

PURPOSE:To provide an accelerometer for measuring the acceleration highly accurately at all times with no influence of temperature strain or aging. CONSTITUTION:The accelerometer comprises a movable part 123A supported at a fixed part 123B by means of a flexible member, a base for supporting the fixed part 123B, forcers 127, 109-1, 109-2 for imparting force proportional to the input acceleration to the movable part 123A so that the displacement at the movable part 123A will be zero at all times, and a displacement detector at the movable part 123A, wherein the movable part 123A and the fixed part 123B are integrally formed of one insulating material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accelerometer for detecting the acceleration of a moving body and a vibrating body such as a ship, an aircraft and an automobile, and more particularly to a servo accelerometer having a feedback loop.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show examples of conventional accelerometers. The accelerometer includes a cylindrical case 10, a first base or frame 12A mounted on the bottom surface 10a of the concave portion of the case 10, and a second base mounted to face the first frame 12A. With a base or frame 12B. A rod-shaped pendulum 30 is arranged between the two frames 12A and 12B, and a flexible joint 20 is attached to a lower end portion of the pendulum 30. Flexible joint 2
0 is attached to the attachment portion 12a of the first frame 12A by a suitable fastener such as a screw via the pressing plate 18, whereby the pendulum 30 is cantilevered.

The accelerometer further includes a pair of cylindrical torquer coils 34A and 34B mounted on the pendulum 30.
A pair of disk-shaped permanent magnets 36A, 36B and a pair of cylindrical pole pieces 38A, 38B, which are mounted on the respective frames 12A, 12B and are separated from the Toruca coils 34A, 34B, and a pendulum 30. One light-emitting element 40A and two light-receiving elements 4 separated from the tip of the
0B, 40B, and a pair of stoppers 42A, 42B arranged on the upper side thereof.

A reference surface 10c is provided on the flange portion 10b of the case 10, and a hole 10d is formed as shown in FIG.
Are formed. The accelerometer is mounted on the hull by mounting such reference surface 10c on the corresponding reference surface of the hull and inserting a suitable fastener, such as a screw, into hole 10d.

A cylindrical terminal case 44 is attached to the flange portion 10b of the case 10, and external terminals 50A and 50B are attached to the terminal case 44.

The cylindrical Toruca coils 34A and 34B are mounted on the pendulum 30 so that the central axes thereof are aligned with the central axis XX of the accelerometer, and the cylindrical pole piece 38 is provided.
A and 38B are arranged inside.

The first frame 12A is disposed in the first frame 12A so that the end face 12b of the first frame 12A contacts the bottom surface 10a of the case 10, and is fixed by a suitable mounting means such as a screw 48 or the like. A lid 52 that also serves as a characteristic nameplate is attached to the outside of the case 10, while the opening portion 44a formed in the terminal case 44 is closed by a lid 54.

In this way, the inside of the accelerometer has a hermetically sealed structure. Therefore, after assembling the components inside the accelerometer, electrical connection is made through the opening 44a, and the inside is evacuated or inert gas is supplied. Filling and closing such an opening 44a with the lid 54, the quality of the components can be maintained for a long time and the life of the accelerometer can be extended.

The pendulum 30, the Toluca coils 34A and 34B attached to the pendulum 30, and the flexible joint 20 are cantilevered by the mounting portion 12a of the first frame 12A, and the flexible joint 20 has an appropriate flexible portion 20a. Is formed so that the pendulum 30 can rotate about the axis of rotation O-O passing through the flexure 20a. For example, as shown in FIG. 5, the bending portion 20a may be formed by forming a rectangular hole 201 in the bending joint 20 and forming thin portions on the two support columns on both sides thereof.

The first frame 12A is made of electromagnetic soft iron, and includes the first pole piece 38A to the first permanent magnet 36.
Acting as a yoke (return path) to form a magnetic circuit through A to the first frame 12A, these cooperate with the first torquer coil 34A to provide the first torquer. The second frame 12B is made of electromagnetic soft iron and functions as a yoke (return path) to form a magnetic circuit from the second pole piece 38B to the second frame 12B via the second permanent magnet 36B. Cooperates with the second Toruca coil 34B to provide a second Toruca.

Here, as shown in the figure, the direction along the central axis of the pendulum 30 in the stationary state is the Z axis, and the direction along the central axis XX of the accelerometer, that is, the disk-shaped permanent magnet 36A. , 36B and cylindrical pole pieces 38A, 38
The direction passing through the center of B and perpendicular to the Z-axis is the X-axis, and the direction orthogonal to both the X-axis and the Z-axis is the Y-axis.

When acceleration is applied along the central axis line XX of the accelerometer, the pendulum 30 rotates about the rotational axis line OO passing through the bending portion 20a, and its tip portion is slightly displaced. As a result, the amount of light emitted by the light emitting element 40A and received by the two light receiving elements 40B, 40B changes, and a minute displacement of the tip of the pendulum 30 is detected.

The signals indicating the minute displacements detected by the displacement detecting device in this manner are the torquer coils 34A, 34A.
The current is fed back to B and the currents flowing through the torquer coils 34A and 34B are controlled so that the minute displacement becomes zero.
Since such a current, that is, the constraint current is proportional to the input acceleration, the input acceleration can be measured by measuring the constraint current.

Stoppers 42A and 42B which are spaced from the pendulum 30 and arranged on both sides thereof function to limit the range of motion of the tip of the pendulum 30 in the direction of the axis XX, thereby supporting the pendulum 30. Flexible joint 20
It is possible to prevent excessive stress from being generated.

[0015]

In such a conventional accelerometer, the flexible joint 20 of the pendulum 30 is attached to the attachment portion 12a of the first frame 12A via the pressing plate 18 by a screw or the like, and the pendulum 30 is attached. Cylindrical torquer coils 34A, 34B are mounted on the disk, and the disk-shaped permanent magnets 36A, 36B and the cylindrical pole pieces 38A, 38 are spaced apart from the torquer coils 34A, 34B.
Since B is arranged, it is necessary to manufacture many parts with high accuracy and assemble them accurately, which results in a long manufacturing time and a high manufacturing cost.

Further, in the accelerometer, the pendulum 30 is formed as a separate material or a separate article with respect to the first frame 12A, and there is a drawback that an error occurs after assembly due to the influence of temperature distortion and aging.

In the accelerometer, it is necessary to zero-adjust the displacement detection device or the like in order to detect the displacement of the pendulum 30 during use, and there is a drawback that the adjustment process takes time.

In view of the above point, the present invention has an object to provide an accelerometer capable of always measuring acceleration with high accuracy without being affected by temperature distortion and aging.

[0019]

According to the present invention, as shown in FIG. 1, for example, flexible members 132-1, 132-2,
The movable part 123A supported by the fixed part 123B by 132-3 and 132-4, the base supporting the fixed part 123B, and the movable part 123A proportional to the input acceleration so that the displacement of the movable part 123A is always zero. In the accelerometer having a forcer that applies the generated force and a displacement detection device that detects the displacement of the movable portion 123A, the movable portion 123A and the fixed portion 1
23B and flexible members 132-1, 132-2, 132-
3, 132-4 are formed as an integrated body made of one insulating material, and the forcer generates a magnetic flux orthogonal to the first coil 127 and the first coil 127 mounted on the movable portion 123A. Magnets 109-1 and 109 mounted on the table
-2, and when the movable portion 123A is displaced with respect to the fixed portion 123B, a current proportional to that is generated by the first coil 127.
Then, the movable portion 123A is returned so that the displacement becomes zero, and the displacement detection device is separated from the first coil 127 and the first coil 127 and the second coil 117-1 is mounted on the base. 117-2 and the oscillator 141 which superimposes and supplies the high frequency current to the first coil 127,
When the movable portion 123A is displaced with respect to the fixed portion 123B, a current proportional to the displacement of the movable portion 123A flows through the first coil 127, whereby the displacement of the movable portion 123A is detected.

According to the present invention, for example, as shown in FIG. 1, in the accelerometer, the first coil 127 attached to the movable portion 123A is formed by the lithography technique.

According to the present invention, for example, as shown in FIG. 1, in the accelerometer, the magnets 109-1 and 109-2 are made of a high magnetic permeability material.

According to the present invention, for example, as shown in FIG. 1, in the accelerometer, the movable portion 123A is the magnet 109-.
Recesses 137-1, 137-2 on the opposite side of 1, 109-2
And the base has projections 139-1, 139-2 corresponding to and located therein the recesses 137-1, 137-2, thereby generated by the magnets 109-1, 109-2. The magnetic resistance of the magnetic circuit is reduced.

[0023]

When the acceleration in the Z-axis direction is applied to the accelerometer, the movable portion 123A is displaced in the Z-axis direction, and the magnetic flux penetrating the first coil 127 and the second coils 117-1 and 117-2 changes. , A voltage proportional to the displacement is induced in the second coils 117-1 and 117-2. By feeding back this voltage to the first coil 127 via the demodulator 143 and the feedback amplifier 145, the movable portion 123A is pulled back in the Z-axis direction to move the movable portion 1A.
The displacement of 23A is always maintained at zero.

The current flowing through the first coil 127 is measured by the voltage of the reading resistor 147 connected in series with the first coil 127, and the acceleration acting on the accelerometer is obtained by the measurement.

[0025]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3, the same parts as those in FIGS. 4 to 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a sectional structure of an example of the accelerometer of the present invention. The accelerometer of this example has a base 101 and a case 103 mounted on the base 101, and a sealed chamber 105 is formed inside by the both.

Here, as shown in the figure, the direction along the central axis of the accelerometer is taken as the X axis, and the Y axis and the Z axis are taken in the plane passing through the main surface of the base 101. As shown, the Y-axis is perpendicular to the paper and the Z-axis is parallel to the paper.

In the closed chamber 105, the recess 1 of the base 101 is provided.
Mechanism unit 121 mounted on 01A and such mechanism unit 121
A magnet member 107, which is further separated from the coil substrate 111, and a control circuit substrate 113 supported by the base 101 by a supporting member 115 are arranged. The mechanical section 121 has a movable section 123A and a fixed section 123B,
The coil substrate 111 is supported by the fixed portion 123B.

The magnet member 107 is a U-shaped C-shaped portion 107A made of a high-permeability material, and permanent magnets 109-1 and 109-2 attached to both ends of the C-shaped portion 107A, respectively.
Have and.

The accelerometer of this example has a first coil 127 and second coils 117-1 and 117-2, and the first coil 127 is arranged on the upper surface of the movable portion 123A of the mechanism portion 121. The second coils 117-1 and 117-2 are arranged on the lower surface of the coil substrate 111 and are separated from each other. The first coil 127 is preferably manufactured by lithographic techniques.

The first coil 127 is arranged so as to surround the X axis, and the second coils 117-1 and 117-2 are arranged so as to surround the corresponding permanent magnets 109-1 and 109-2, respectively. . The second coils 117-1, 117-
Instead of 2, the coil 117-3 around which the C-shaped portion 107A of the magnet member 107 is wound may be arranged.

FIG. 2 shows details of the mechanical section 121. The mechanical portion 121 has a substantially rectangular movable portion 123A at the center and a fixed portion 123B around the movable portion 123A. The fixed portion 123B is the base 101.
The mechanical part 121 is supported by the base 101.

The mechanical part 121 of this example is manufactured from a single rectangular plate made of an insulating material, and has a movable part 123A and a fixed part 12.
3B is configured as an integral body without using connecting means such as welding. That is, the mechanism portion 121 is formed with a pair of thin holes 131-1 and 131-2 arranged in parallel to the Y axis and a pair of U-shaped elongated holes 131-3 and 131-4. Supporting members 132-1, 132-2, 132-3, 132-4 made of elongated members are formed between the holes. The mechanism unit 121 may be composed of, for example, a single crystal such as quartz.

Such holes 131-1, 131-2, 131
-3 and 131-4 form a movable portion 123A with respect to the fixed portion 123B.
Movable part 12 by 32-2, 132-3, 132-4
3A is supported by the fixed portion 123B.

First pair of support members 132-1 and 132-
2 and the second pair of support members 132-3 and 132-4 are arranged on both sides of the Y axis and parallel to the Y axis. Such support members 132-1, 132-2, 13
2-3 and 132-4 are formed in a thin plate shape having a small dimension in the Z-axis direction and a sufficiently large dimension in the thickness direction (X-axis direction). Therefore, the support member 132
-1, 132-2, 132-3, 132-4 have large rigidity against bending in the X-axis direction and bending in the Y-axis direction,
It has low rigidity against bending in the Z-axis direction. Thus, the support members 132-1, 132-2, 132-3, 1
32-4 is allowed to bend in the Z-axis direction, so that the movable portion 123A can be displaced in the Z-axis direction with respect to the fixed portion 123B.

An elongated hole 131-arranged parallel to the Y axis
The protrusions 13 are formed on the inner sides of the holes 1 and 131-2, respectively.
3-1 and 133-2 are formed, and the protrusion 13 is formed.
3-1 and 133-2 function as stoppers that limit the displacement of the movable portion 123A in the Z-axis direction.

The movable portion 123A is formed in a substantially rectangular shape, and the first coil 127 is concentrically arranged in the rectangular shape. X at the center of the movable portion 123A and the first coil 127.
The axis passes. The lead wire connected to the first coil 127 extends from the movable portion 123A to the fixed portion 123B via the support members 132-3 and 132-4, and is connected to the terminals 135A and 135B arranged on the fixed portion 123B. Has been done.
As shown in FIG. 3, such terminals 135A and 135B are connected to the control circuit 140 of the control circuit board 113.

FIG. 2 shows the relative positional relationship between the first coil 127 and the magnet member 107.
As shown by the broken line, one permanent magnet 109-1 is aligned with one side of the first coil 127, and the other permanent magnet 109-2 is aligned with one side of the opposite side of the first coil 127. It is arranged.

On the lower surface of the movable part 123A of the mechanism part 121, as shown by the broken line in FIG.
1, 137-2 are formed, and correspondingly, two convex portions 139-1, 139-2 are formed on the bottom surface of the concave portion 101A of the base 101, as shown in FIG. The cross sections of the protrusions 139-1 and 139-2 perpendicular to the X axis may be formed larger than the cross sections of the permanent magnets 109-1 and 109-2 perpendicular to the X axis. The convex portion 1 of such a base 101
Reference numerals 39-1 and 139-2 denote concave portions 137- of the movable portion 123A.
1 and 137-2, respectively. Thus
A narrow and substantially uniform gap is formed between the lower surface of the movable portion 123A and the bottom surface of the recess 101A of the base 101.

Next, the operation of the accelerometer of the present invention will be described with reference to FIG. In the accelerometer of the present invention, the movable portion 123A is Z.
When the movable portion 123A is displaced in the axial direction, the movable portion 123A has a feedback loop for displacing the movable portion 123A in the opposite direction to the Z-axis direction to always keep the displacement of the movable portion 123A at zero.
It has a displacement detection function of detecting the displacement of 23A in the Z-axis direction.

FIG. 3 shows the control circuit 140 included in the control circuit board 113 and the first coil 127 and the second coils 117-1 and 117-2 connected to the control circuit 140.

The control circuit 140 outputs from the oscillator 141 which generates the reference AC voltage of the frequency f ₀ , and the demodulator 143 and the demodulator 143 which rectify the input AC current into the DC current by the reference AC voltage from the oscillator 141. It may be configured to have a feedback amplifier 145 for inputting a DC current and a reference AC voltage from the oscillator 141 and a read resistor 147.

As shown in FIG. 1, the magnet member 107.
A magnetic field is generated by the two permanent magnets 109-1 and 109-2 attached to the magnetic flux Φ ₀ , and the magnetic flux Φ ₀ is generated by the permanent magnet 109-1 on one side and the concave portion 137-1 of the movable portion 123A on the one side.
And the convex portion 139-1 on one side of the base 101, the inside of the base 101, and the convex portion 13 on the other side of the base 101.
9-2 and the other concave portion 137-2 of the movable portion 123A to reach the other permanent magnet 109-2.

As described above, the shape is formed on the lower surface of the movable portion 123A.
In the formed recesses 137-1 and 137-2 and the base 101
Due to the formed convex portions 139-1 and 139-2,
Bundle Φ ₀The magnetic resistance of the magnetic path through which the permanent magnet 109
-1, 109-2 makes the magnetic field generated by high efficiency
Can be used. Therefore, the permanent magnet 109-
1, 109-2 can be miniaturized.

Let i be the current flowing through the first coil 127.
Then, the first coil 127 generates a magnetic flux Φ. ₀By Flemin
According to Gug's left-hand rule, the force in the Z-axis direction must be received.
It Thus, the two permanent magnets 109-1, 109-2
And the first coil 127 constitute a forcer,
With such a forcer, the movable portion 123A is the first coil.
It receives a force in the Z-axis direction that is proportional to the current i of 127.

On the other hand, the oscillator 14 is connected to the first coil 127.
1 is applied via the feedback amplifier 145, whereby the X-axis direction (see FIGS. 2 and 3).
An alternating magnetic flux Φ _f is generated along the direction (perpendicular to the paper surface). By the alternating magnetic flux Φ _f , the second coil 117
AC voltage of frequency f is induced in -1, 117-2.

The second coils 117-1 and 117-2 are arranged symmetrically with respect to the first coil 127. That is, the second coils 117-1 and 117-2 are arranged symmetrically with respect to the central axis line of the first coil 127, that is, the Y-axis, and each of the second coils 117-1 and 117-2 is the first coil.
The coils 127 are symmetrically arranged with respect to the respective sides 127-1 and 127-2.

The second coils 117-1 and 117-2 are differentially connected, so that the directions of the magnetic fields in the two coils are of opposite polarities. When the movable portion 123A is not biased in the Z-axis direction, the coupling area between the upper coil 117-1 and the first coil 127 of the second coil is smaller than the lower coil 117-2 and the first coil 127. The coupling area with 127 is equal to that of the second coil 117-
The output of the output terminal 149 of No. 1, 117-2 is zero.

When the acceleration in the Z-axis direction is input to the accelerometer, the movable portion 123A is displaced in the Z-axis direction, and the first coil 1
27 is displaced in the Z-axis direction relative to the second coils 117-1 and 117-2. Then, the coupling area between the upper coil 117-1 and the first coil 127 of the second coil is not the same as the coupling area between the lower coil 117-2 and the first coil 127. The coupling area of the coil 117-1 on the upper side of the second coil is increased, and the coil 117-1 on the lower side is increased.
The bond area of -2 is reduced.

Therefore, the second coils 117-1, 1
A voltage corresponding to the change in the coupling area is generated at the output terminal 149 of 17-2. Since the change in the coupling area is proportional to the displacement of the movable portion 123A in the Z-axis direction, the output voltage of the output terminal 149 represents the displacement of the movable portion 123A in the Z-axis direction.

The output terminals 149 of the second coils 117-1 and 117-2 are connected to the demodulator 143, and the AC voltage of the frequency f output from the output terminal 149 is supplied to the demodulator 143. . In the demodulator 143, the alternating voltage is generated by the oscillator 141.
It is synchronously rectified by the reference AC voltage signal from and converted into DC current. Such direct current is applied to the first coil 127 via the feedback amplifier 145.

In this way, the current i is applied to the first coil 127, so that the movable portion 123 is moved as described above.
A receives a force in the Z-axis direction proportional to the current i, and the movable portion 12
The displacement of 3A is returned to the original position so that it becomes zero.

Next, the acceleration detecting function of the accelerometer of this example will be described. The accelerometer of this example is configured as a feedback type accelerometer. When acceleration acts on the accelerometer and the movable portion 123A is displaced in the Z-axis direction, a current i proportional to the displacement is applied to the first coil 127. , Thereby causing the movable portion 123A to receive a force in the Z-axis direction, and the displacement of the movable portion 123A is always maintained at zero.

The output end 135B of the first coil 127 is grounded via the read resistor 147, and the output terminal 151 is connected between the output end 135B of the first coil 127 and the read resistor 147. .

The current applied to the first coil 127 is read by the output terminal 151. The current i applied to the first coil 127 is proportional to the acceleration of the movable portion 123A in the Z-axis direction, and the current i is read by the reading resistor 14A.
It is converted into a voltage signal by flowing through 7. Therefore, the acceleration in the Z-axis direction input to the accelerometer is obtained from the voltage signal read by the output terminal 151.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and it is apparent to those skilled in the art that various other configurations can be adopted without departing from the gist of the present invention. Easy to understand.

[0057]

According to the accelerometer of the present invention, the movable portion 12
Since the mechanical section 121 having 3A and the fixing section 123B is configured as an integrated body formed of one sheet of insulating material, it is possible to provide a highly accurate accelerometer that does not require position adjustment during assembly. There is an advantage that can be.

According to the accelerometer of the present invention, the movable part 123
Since the mechanism portion 121 having A and the fixing portion 123B is formed as an integrated body formed of a single insulating plate material, it is highly accurate and does not cause an error due to the influence of thermal strain, aging, or the like. There is an advantage that an accelerometer can be provided.

According to the accelerometer of the present invention, the movable part 123
Since the mechanism portion 121 having A and the fixing portion 123B is configured as an integrated body formed of one sheet of insulating material, it is possible to form the mechanism portion 121 by a single crystal material such as quartz. There is an advantage that it is possible to provide a high-precision accelerometer that is not affected by thermal distortion, aging, and the like.

According to the accelerometer of the present invention, the movable part 123
A, the fixed portion 123B, and the first attached to the movable portion 123A
Since it is possible to manufacture the mechanism section 121 having the coil 127 and the high accuracy and in a large amount by the lithography method, there is an advantage that a highly accurate and inexpensive accelerometer can be provided.

According to the accelerometer of the present invention, the high frequency voltage from the oscillator 141 is applied to the first coil 127, and the second coil
Since the coils 117-1 and 117-2 are differentially connected to each other and the output voltage thereof is fed back to the first coil 127, a mechanical section including the movable section 123A and the fixed section 123B. Since a displacement detector for accurately detecting the displacement of the movable portion 123A can be obtained without changing the structure of the 121, there is an advantage that the yield of the lithography process can be compensated.

According to the accelerometer of the present invention, the mechanical section 121
The recesses 137-1 and 137-2 are provided in the base 10
1 is provided with convex portions 139-1 and 139-2, the air gap included in the magnetic circuit is minimized, thereby reducing the magnetic resistance, and the small permanent magnets 109-1 and 109-2 increase the magnetic flux Φ ₀ density. Is obtained, and there is an advantage that a forcer having a high efficiency current-force conversion performance can be configured.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an accelerometer of the present invention.

FIG. 2 is a diagram showing a mechanical portion of the accelerometer of the present invention.

FIG. 3 is an explanatory diagram illustrating an operation of the accelerometer of the present invention.

FIG. 4 is a diagram showing a cross-sectional configuration of a conventional accelerometer.

FIG. 5 is a diagram showing a planar configuration of a conventional accelerometer.

[Explanation of symbols]

10 Case 10a Bottom face 10b Flange part 10c Reference surface 12A, 12B Frame 12a Attachment part 18 Holding plate 20 Flexible joint 20a First flexible part 30 Pendulum 34A, 34B Toruca coil 34e, 34d hole 36A, 36B Permanent magnet 38A, 38A 40P pole piece Light emitting element 40B Light receiving element 42A, 42B Stopper 44 Terminal case 44a Opening 48 Screw 50A, 50B External terminal 52, 54 Lid 60A, 60B Stopper 101 Base 101A Recess 103 Case 105 Closed chamber 107 Magnet member 107A C-shaped section 109-1, 109-2 Permanent magnet 111 Coil board 113 Control circuit board 115 Support member 117-1, 117-2 Stopper 121 Mechanism part 123A Movable part 123B Fixed part 127 First carp 127-1, 127-2 One side of coil 131-1, 131-2, 131-3, 131-4 Hole 132-1, 132-2, 132-3, 132-4 Support member 133-1, 133- 2 Stoppers 135A, 135B Output terminals 137-1, 137-2 Recesses 139-1, 139-2 Convex parts 140 Control circuit 141 Oscillator 143 Demodulator 145 Feedback amplifier 147 Read resistor 149 Output terminal 151 Acceleration output terminal

Claims (4)

[Claims] 1. A movable part supported by a fixed part by a flexible member, a base supporting the fixed part, and a displacement proportional to the input acceleration of the movable part so that the displacement of the movable part is always zero. In an accelerometer having a forcer for applying a force and a displacement detection device for detecting the displacement of the movable part, the movable part, the fixed part, and the flexible member are integrated into one piece made of an insulating material. The forcer includes a first coil attached to the movable portion and a magnet attached to the base to generate a magnetic flux orthogonal to the first coil, and the movable portion is attached to the fixed portion. When it is displaced, a current proportional to that is caused to flow in the first coil, whereby the movable part is returned so that the displacement becomes zero, and the displacement detecting device is separated from the first coil and the first coil. Placed on the base A second coil and an oscillator for supplying a high-frequency current to the first coil in a superimposed manner, and when the movable part is displaced with respect to the fixed part, a current proportional to the displacement flows to the first coil. An accelerometer characterized in that the displacement of the movable part is detected thereby. 2. The accelerometer according to claim 1, wherein the first coil attached to the movable portion is formed by a lithography technique. 3. The accelerometer according to claim 1, wherein the magnet is made of a material having a high magnetic permeability. 4. The accelerometer according to claim 1, wherein the movable portion has a concave portion on the side opposite to the magnet, and the base has a convex portion corresponding to the concave portion and arranged therein. An accelerometer characterized in that the magnetic resistance of the magnetic circuit generated by the magnet is thereby reduced.