JPH07198742A - Accelerometer and assembling method thereof - Google Patents

Abstract

PURPOSE: To provide a new precise accelerometer in a very simple structure, in which no undesired torque or moment of force entirely occurs. CONSTITUTION: A bolt 11 is passed through holes formed in a center column 2, a piezoelectric plate 3, a mass 4 so that the bolt 11 can not mechanically and electrically be put in contact with the center column 2 to mount the piezoelectric plate 3 and the mass 4 pairing each other to the center column 2. The bolt 11 can be matched into the holes while being assisted in matching into the holes and kept in no contact with the center column 2. The bolt 11 is provided through the hole at a right angle for multi-axial measurement and the mounting angle of an accelerometer mainbody is changed for all-directional measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to accelerometers using piezoelectric materials, and more particularly to shear-type piezoelectric sensors responsive to acceleration and vibration.

[0002]

2. Description of the Prior Art Accelerometers that apply the shearing principle have some special advantages over standard compression type accelerometers, which have much less strain sensitivity to mounting conditions.

A typical model of an accelerometer, which is widely known on the market, is described in Swiss Pat. No. 547,489 and is shown in the prior art in FIGS. 1 and 2. The shear type piezoelectric plate 3 is screwed to the central support 2 with two mass bodies 4 interposed below the bolt head.

In addition to the need for an insulating washer 10 and electrode 9 to separate the signal from this structure, prior art devices had other drawbacks. It is not possible to transfer a well-defined shear force to the surface of the piezoelectric plate. This is because the bolt transmits the force to the hole of the piezoelectric plate. Furthermore, the mass absorbs the bending forces transmitted by the bolts screwed into the central column.
Therefore, the sensitivity of prior art accelerometers will be highly dependent on the assembly procedure as well as the torque value applied to the bolt.

[0005]

According to the invention, all of these uncertainties are eliminated. This is achieved by providing a novel means for applying only shear forces to the piezoelectric plate along the main measuring direction Z, regardless of the torque value of the pre-stressed bolt. Furthermore, no insulating washers or electrodes are needed to obtain the measurement signal from the piezoelectric plate.

The present invention therefore has a very simple design and is a novel type of shear acceleration which can be manufactured very accurately and with reproducible specifications without any unwanted torque or force moment effects. Provide a total. This design and simplicity of manufacture allows the present invention to be manufactured in a very competitive price range.

Another object of the present invention is to symmetrically distribute the clamping force over the entire surface of the piezoelectric plate, and
Of particular importance is the fact that the clamping force vector (V) is perfectly perpendicular to the piezoelectric plate and is also parallel to the axial direction of the through bolt structure. These measures have allowed an intimate contact of the shear force transfer surfaces, resulting in a prominent frequency response being predictable.

Yet another object of the present invention is to allow inclusion of one or more mass body screwed structures to obtain a two or three axis accelerometer with the same design principles.

[0009]

These and other features include a piezoelectric plate and a mass, each having a hole aligned with a hole formed in a central post of an accelerometer body, through the holes. It is achieved by fixing with extended bolts so that the mass and the piezoelectric plate are clamped to the central column without contacting the central column. This insulates the bolt mechanically and electrically from the central column. The holes are aided in alignment by the common external dimensions of at least two sides, and the bolts are aligned with the holes. The bolt is mechanically and electrically isolated from the central strut by an annular space, or the annular space is loaded with an electrically insulative, non-force transmitting sleeve. Biaxial detection is performed using a piezoelectric plate. One bolt secures both piezoelectric plate pairs to the central post.

The combination of these two is used for three-axis detection. In this, a pair of opposing piezoelectric plates separated by a central post is fixed by one bolt in the first hole. Two opposing pairs separated by a central strut are secured by bolts in a second hole that is perpendicular to the first hole. Each of the two pairs of piezoelectric plates on a common bolt has a thickness along the hole axis that is half the thickness of one pair of piezoelectric plates along the hole. One pair of bolts of the piezoelectric device is a shear type piezoelectric plate, and two pairs along one bolt are one pair of shear type piezoelectric plate and one pair of compression type piezoelectric plate, or two pairs. It is a shear type piezoelectric plate. The structure of this accelerometer provides force detection along the X, Y and Z axes. Linear or angular acceleration is detected by selecting the polarities of the pair of piezoelectric plates.

The first and second right-angled holes are formed in one central post along which there is a vertical spacing. Alternatively, they are formed into a pair of central columns that are perpendicular to each other.
This right angled central post is generally L-shaped or T-shaped.

In order to adjust the sensitive axis of the piezo plate, the housing contains two right-angled mounting holes in a plane perpendicular to the central column. One of the mounting holes is formed in the same plane as the hole for receiving the mounting bolt for mounting the pair of piezoelectric plates on the central column. The piezoelectric plate mounted on the central column in this embodiment has an axis parallel to the sensitive direction or perpendicular to the sensitive direction.

The outer dimensions of the central post, the piezoelectric plate and at least three sides of the mass are made the same to assist in hole alignment. An aligning tool having an internal dimension similar to this external dimension aligns the holes, and the bolt is tightened in this state.

Objects and features of the present invention will become apparent to those skilled in the art by reference to the following description and drawings which disclose embodiments of the invention.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT For simplicity of explanation, the mounting base 8 of the accelerometer is assumed to be perpendicular to the Z axis.

It is assumed that it is well known that shear-type accelerometers use piezoelectric plates that are sensitive only to shear forces. The shear force vector of the piezo plate must be matched according to the desired sensitive axis and also according to the manufacturer's technical status.

Piezoelectric crystal materials used for such purposes are well known. Two groups can be used: (a) industrial ceramics, or (b) quartz, natural crystals such as tourmaline.

A wide variety of materials can be used as piezoelectric plates in industrial ceramics, such as barium titanate (barium titanate), red metaniobate (lead metaniobate), red zirconate (lead zirconate) and other combinations.

However, natural crystals generate electrical signals of small amplitude and have very good temperature and aging stability. Therefore, in precision instrument applications, natural crystals, primarily quartz, are commonly used. However, the invention is independent of the piezoelectric material used.

The prior art accelerometer of FIG. 1 is described in detail in Swiss Patent No. 547 489. It comprises an accelerometer body 1, which is constructed with a central support 2, which is fixed to a mounting base 8.
The piezoelectric plates 3 are symmetrically arranged on both sides of the central column 2. These are prestressed by the individual bolts 5 via the mass 4. The sensitive axis of the piezoelectric plate 3 must be precisely aligned with the direction of the Z axis. Therefore,
The bolt 5 must be finely torqued to the required value to produce the required prestress.
The use of two bolts does not guarantee that each piezoelectric plate is in the same prestressed state.

In FIG. 2, the same prior art accelerometer has been magnified, touched the piezoelectric plate and also insulated washer 1.
The electrode 9 is electrically insulated from the mass 4 and the bolt 5 by 0. The signal line 6 connects the electrode 9 to the connector in FIG. Since the other side of the piezoelectric plate like the bolt 5 is electrically connected to the central support column 2,
The bolt 5 must be electrically isolated from the electrode 9.
In this structure, Z detected by being applied to the piezoelectric plate 3
The forces along the axis are the shear forces along the Z axis and the forces generated by the moment M shown in FIGS. The moment M is generated by a cantilevered steel material around the fixed point where the bolt 5 is fixed to the central column 2.

An accelerometer according to the present invention is shown in FIGS. The innovative difference from the prior art of FIG. 1 will soon become apparent. This structure of the piezoelectric plate 3, which is symmetrical with respect to the central column 2, is similar. The main difference, however, is that one through bolt 11 extends from one mass 4 through the piezoelectric plate 3 and the central column 2 without touching them and is screwed into the mass 4 on the other side. That is. The annular space 12 between the hole and the through bolt 11 avoids mechanical and electrical contact between the through bolt 11 and the piezoelectric plate 3 and the central post 2. Such a contact isolation connection connects the two masses 4 to the solid unit, which exerts only a shearing force on the piezoelectric plate 3. The bending moment M as shown in FIGS. 1 and 2 does not occur. This is because the through bolt 11 does not fix the pivotal movement around it. Therefore, all forces parallel to the Z-axis remain parallel to that Z-axis and the through bolt 1
Not converted to motion by 1. All the compressive forces guided by the mass 4 and the through bolt 11 are only parallel to the axis of the through bolt and the hole, even if there is a force parallel to the Z axis.

Since the through bolt does not contact the central column 2, the through bolt is electrically insulated from the central column 2 and therefore the insulating washer 5 is not needed. Moreover, the separate electrode 9 is not necessary. This is because the mass body 4 can act as an electrode. The through bolt 11 connects the two mass bodies 4 and thereby guides the measurement signal from the piezoelectric plate 3 directly to the signal line 6. This reduces the series resistance and contact resistance.

Therefore, the accelerometer of the present invention accurately responds to the input force in the Z direction and has no influence on any other force or moment. Therefore, its accuracy is far superior to the design in the technical state.

The present invention is not only mechanically perfect but
The structure is simplified so that the insulating washer 10 and the electrode 9 as shown in FIG. The signal line 6 can be directed directly to one of the mass bodies 4.

FIG. 4 is a modification of the embodiment of FIG. Here, the non-contacting annular space 12 is filled with a radially elastic electrically insulating sleeve 13. this is,
A pipe made of polytetrafluoroethylene having a flexible groove, which does not transmit a radial force from the through bolt 11 to the hole portion and also electrically insulates the through bolt 11 from the central column 2 and the piezoelectric plate 3 or It can be a casting of a silicone rubber sleeve or a similar device.

A simple aligning tool 14 is used as shown in FIG. 5 to align the through bolt 11 with the hole in the central strut 2 and hold the non-contact annular space 12 during assembly of the device. The piezo plate 3, the mass 4 and the central column 2 have very similar geometric dimensions on at least two sides and the tool 14 is placed on the assembly group during tightening of the through bolt 11. While this geometric dimension helps align holes,
The contact between the through bolt 11 and the holes in the mass provides the alignment of the through bolt with the aligned holes. This simple means allows for perfect centering of the various parts and retention of the non-contact annular space 12. Other devices and visual alignment can be achieved using similar dimensions.

Inner insulating sleeve 1 as shown in FIG.
No. 3 requires no matching concrete. However, the accelerometer contains another part. Although not required for the assembly of FIG. 4, the alignment tool 14 eliminates Z-axis alignment errors between the mass 4 and the piezoelectric plate 3.

As shown in FIG. 6, an electrode 17 is provided between two compression type piezoelectric plates 15, and an electrode 18 is provided between two shearing type piezoelectric plates 16. The electrode 19 for the z signal is connected to one mass body 4. The piezo plates 15 and 16 are half the thickness of the normal shear type piezo plate 3 of the main Z axis. Since the mass bodies 4 of the piezoelectric plates 15 and 16 are not electrically connected to the central support column 2 by the through bolts 11, they are externally connected to the central support column 11 by electrodes not shown. Thus, the central post forms the common electrode for all three piezoelectric plate pairs.

This complex structure does not require any insulating washers as shown in FIG. 2, but separate electrodes are needed for the y and x signals.

As shown in FIGS. 3-6, the poles of the piezoelectric plate are connected in a support or additional structure. 3 to 4, the piezoelectric plate 3 connected to the central supporting column 2 is positive, and in FIG. 6, the negative surface is connected to the central supporting column 2. The arrows not only indicate the poles, but also the piezoelectric plate type and axis. In FIG. 6, the piezoelectric plates 3 and 16 are of the shear type, and the piezoelectric plate 15 is of the compression type.
The connections and polarities shown in FIGS. 3-6 for the shear-type piezoelectric plate 3 provide linear acceleration measurements along the Z-axis, and as described in US Pat. No. 4,996,878, Y. Cancels the angular acceleration around the axis. Piezoelectric plate 3
The piezoelectric plate 3 measures the angular acceleration about the Y-axis and cancels the linear acceleration along the Z-axis by inverting one of the poles. This selection can be made without the use of a separate electrode 9 and insulating washer 10.

An accelerometer for measuring acceleration along the Z and X axes using only shear type piezoelectric plates is shown in FIG. As shown in FIG. 6, a pair of double piezoelectric plates 16 with intermediate signal electrodes are provided on each side of the central post 2 for the Z and X axes. Electrode 18 for the x signal and electrode 19 for the z signal are connected to an amplifier or other display or signal processing device. The through bolt 11 does not make contact with the central column 2 and attaches the two mass bodies 4 and the two pairs of piezoelectric plates 16 to the central column 2.

A further variation of FIG. 6 to detect acceleration in all three axes (ie, X, Y and Z) is shown in FIG. The central strut 20 is shown generally as a T and includes a central bar 21 and a lateral bar 22. Piezoelectric plates 16 forming a pair are arranged on both sides of the central bar 21 with an intermediate signal electrode and a vibrating mass 14. One of the shear type piezoelectric plates detects the acceleration in the Z-axis,
The other of the shear type piezoelectric plates 16 detects acceleration in the Y-axis. The two mass bodies 4 and the two pairs of piezoelectric plates 1
6 are clamped together by through bolts 11. The through bolt does not contact the central bar 21 and does not contact any of the pair of piezoelectric plates 16.

A third piezoelectric plate pair 16 having an intermediate signal electrode is attached to the horizontal bar 22 with a through bolt 11. The through bolt 11 does not contact with the horizontal bar 22 either in the contact diagram or in the piezoelectric plate 16. This pair of piezoelectric plates is also of the shear type.

In contrast to the accelerometer of FIG. 6 in which the piezoelectric crystal in compression mode detects acceleration in the Y-axis direction, FIG.
A shear-type piezoelectric crystal is used for the acceleration of the axis. Therefore, the effect of temperature is the same for all measuring elements. Also, shear-type piezoelectric measuring members are less sensitive to temperature than compression-type measuring members. Producing a shear-only measuring element, such as quartz, is much easier than producing a combined shear-formal and compression-type measuring element.

Although the center post 20 is shown to be generally T-shaped, it may be L-shaped. The important thing is the central column 2
0 forms two bars which are perpendicular to each other and extend parallel to the axis, here the Z-axis. Therefore, the two bars of the through bolt 11 are at a right angle.

FIG. 9 shows the housing cover 24 of the accelerometer of FIG. The flat top surface of the T-shaped central post 20 provides a suitable location for the electronic components including the illustrated semiconductor amplifier 23.

One of the prior art, standard accelerometer housings, includes a plug 27 of electronic signal cables. Holes 25 are provided to receive screws or other fasteners to secure the housing to the mounting surface.

The shear type piezoelectric plate has one direction of maximum sensitivity. In order to allow the sensitive directions to be precisely aligned and one piezoelectric plate to be used to detect either one of the two axes or directions, the housing 1 is shown in FIGS.
As shown in FIG. 14, a pair of orthogonal holes 25A and 25B are provided. The acceleration body 1 supports a central column 2, and the piezoelectric plate 3 and the vibrating mass body 4 are arranged along an axis perpendicular to the central column. Housing 24 is also shown. The axial sensitivity of the shear-type piezoelectric crystal 3 is shown in FIGS. 12 to 14 as being parallel to the axis of the hole 25A and perpendicular to the axis of the hole 25B. Therefore, hole 2
The fixture 26 in 5A mounts the piezoelectric plate 3 on a mounting surface and is adapted to respond to accelerations normal to this mounting surface.

The angular position of the central support column 2 is any of 360 ° around the axis 25A, but this sensitivity axis is always perpendicular to the mounting surface, and the acceleration along the Z axis is shown in FIGS. 11 to 13. To detect. The accelerometer body 1 is rotated 90 ° so that the detection axis of the piezoelectric plate is parallel to the mounting surface. A screw 26 passing through the hole 25B mounts the piezoelectric crystal on the mounting surface with its sensitive axis parallel to the mounting surface. By rotating the piezoelectric crystal 3 around the axis 25B, the acceleration can be detected in a plane parallel to the mounting surface. Using the coordinates in the previous figures, the piezoelectric plate 3 can detect the acceleration in X or Y simply by positioning it appropriately about axis 25B. Assuming that the piezoelectric plate detects acceleration along the X axis as shown in FIG. 14, rotating 90 ° about axis 25B will detect acceleration along the Y axis. Therefore, FIG.
As shown in FIG. 14, by forming two holes in the central column at right angles to each other, one shear type piezoelectric plate can detect the acceleration in any of the three axes by proper mounting.

In the embodiment of the invention already described, the pair of piezoelectric plates for a given measuring or sensitive axis always have the same axis and direction.

In shear-type devices, this pair measures acceleration along a common axis, but it is often important to measure along a given planar section. Figure 1
5 and FIG. 16 show a pair of shear type piezoelectric plates 3 whose sensitive principal axes are orthogonal to each other. As shown, these define a plane perpendicular to the axis of hole 25D of accelerometer body 1. By fixing the accelerometer body 1 with a fixture passing through the hole 25C, the piezoelectric plate 3 measures the force on a finite number of planes orthogonal to the mounting surface. As already mentioned, the housing 1 can be rotated about the axis 25C to define a particular plane, all of which are at right angles to the mounting surface.

Rotate the accelerometer body 1 by 90 ° to make a hole 25D.
By fixing the accelerometer body to the mounting surface using, the plane defined by the sensitive axis of the piezoelectric plate 3 is parallel to the mounting surface. Again, as in the previous embodiment, this plane can rotate about the axis 25D at any angle up to 360 °. One piezoelectric plate 3 has been described with respect to FIGS. 15 and 16, each shown by a pair of piezoelectric plates with electrodes arranged as previously described as piezoelectric pair 16.

The mounting holes 25 of each housing of FIGS. 11 to 16 are at right angles to each other in a plane perpendicular to the central column 2. One of the mounting holes 25 is in the same plane as the hole of the through bolt for mounting the piezoelectric plate 3 on the central column. In Figures 11 and 14, and Figures 15 and 16, this is axes 25B and 25D, respectively.

Although the present invention has been shown as a symmetric device, it can also be used in asymmetric structures and incorporate the principles of the present invention. For example, one of the piezoelectric plates 3 may be replaced by an insulating washer to provide electrical insulation between the mass 4 and the through bolt 11 and the central post 2. If desired, in order to maintain the mechanical symmetry of the device, the mass 4 can be increased to compensate for any differential loss between the piezoelectric plate 3 and the insulating washer.

The present invention thus provides a highly accurate and simple design accelerometer for multi-axis applications having the same standard signal amplitude on all axes.

Accordingly, the present invention enhances the performance of shear-type accelerometers with dramatically higher accuracy and even higher reproducibility of results. This is because unwanted parameters that affect the results are eliminated. At the same time, it will enable high performance at low cost. This concept can be applied to modern methods that enable effective assembly of single-axis or multi-axis accelerometers.

While the present invention has been described and illustrated in detail, it should be clearly understood that these are merely illustrations and examples and are not intended to be limiting. The spirit and scope of the present invention is limited only by the claims that follow.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a prior art accelerometer.

2 is an exploded view of the accelerometer of FIG. 1 showing electrodes and insulating disks.

FIG. 3 is a cross-sectional view of an accelerometer incorporating the principles of the present invention.

FIG. 4 is a cross-sectional view of an accelerometer incorporating the principles of the present invention.

FIG. 5 is a perspective view of an alignment tool incorporating the principles of the present invention.

FIG. 6 is a top view of a multi-axis accelerometer incorporating the principles of the present invention.

FIG. 7 is a perspective view of a biaxial accelerometer using a shear type piezoelectric plate incorporating the principle of the present invention.

FIG. 8 is a perspective view of a triaxial accelerometer incorporating the principles of the present invention.

9 is a side view of the accelerometer of FIG. 8 with a cover.

FIG. 10 is a perspective view of a prior art accelerometer housing.

FIG. 11 is a partial cutaway plan view of an axis adjustable accelerometer incorporating the principles of the present invention.

12 is a partial cutaway side view of the accelerometer of FIG.

FIG. 13 is a perspective view of the accelerometer of FIGS. 11 and 12.

FIG. 14 is a perspective view of the accelerometer in an orientation different from that of FIG.

FIG. 15 is a perspective view of another embodiment of the accelerometer of the present invention.

16 is a perspective view of the accelerometer in a different orientation than that of FIG.

[Explanation of symbols]

 1 Accelerometer main body 2 Central support 3 Piezoelectric plate 4 Mass body 5 Bolt 9 Electrode 10 Insulating washer 11 Through bolt 12 Annular space 13 Insulation sleeve 14 Tool 15,16 Piezoelectric plate 18,19 Electrode 20 Central support 21 Central bar 22 Horizontal bar 23 Amplifier 24 Cover 25, 25A, 25B, 25C, 25D Hole

Claims (28)

[Claims] 1. A body comprising a central post having a first hole, at least one first piezoelectric plate and at least one first mass each having a first hole, said main post contacting said central post Between the first bolt in the first hole for clamping the mass body and the piezoelectric plate to the central column without the first bolt, means for facilitating alignment of the first hole, and the first bolt and the central column. And a means for aligning the first bolt in the first hole so as to maintain a non-contact state, the accelerometer. 2. The accelerometer according to claim 1, wherein the bolt does not contact the piezoelectric plate. 3. The accelerometer according to claim 1, wherein the piezoelectric plate is a shear-type piezoelectric plate that detects a lateral force with respect to the hole. 4. The accelerometer according to claim 1, wherein the bolt has a diameter smaller than a diameter of the hole of the central support column so as to form a non-contact ring therebetween. Accelerometer characterized by. 5. The accelerometer of claim 1, including an electrically insulating, force non-transmitting sleeve that isolates the bolt from the hole in the central post. 6. The accelerometer according to claim 5, wherein the sleeve is one of a grooved polytetrafluoroethylene sleeve or a silicone rubber sleeve. 7. The accelerometer of claim 1, wherein the aiding means has the same profile on at least two sides to assist in aligning the central post, the piezoelectric plate, and the first hole. An accelerometer comprising the mass having dimensions. 8. The accelerometer of claim 7, including an alignment tool having the same internal dimension as the external dimension for aligning the first hole during tightening of the bolt. Characteristic accelerometer. 9. The accelerometer according to claim 1, wherein the center column has a second hole that is perpendicular to the first hole, and each has a second hole. At least one second piezoelectric plate and at least one second mass, and a second bolt in the second hole for clamping the second mass and the piezoelectric plate to the central post without contacting the central post; An accelerometer characterized by being out. 10. The accelerometer according to claim 9, wherein the center column extends parallel to the Z axis of the body, and the first hole extends parallel to the X axis of the body, and The second hole is parallel to the Y-axis of the main body, the first and second piezoelectric plates are shear-type piezoelectric plates, and the first piezoelectric plate is aligned with the Z-axis of the main body. An accelerometer, wherein the second piezoelectric plate detects a force along the X-axis of the main body. 11. The accelerometer according to claim 9, wherein the central column extends parallel to the Z axis of the body, and the first hole is parallel to the X axis of the body, , The second hole is parallel to the Y-axis of the main body, the second piezoelectric plate is a compression type piezoelectric plate, and the first piezoelectric plate applies a force along the Z-axis of the main body. And detecting the force of the second piezoelectric plate along the Y-axis of the main body. 12. The accelerometer according to claim 9, wherein the central column extends parallel to the Z axis of the body, and the first hole is parallel to the X axis of the body, and , The second hole being parallel to the Y axis of the body, and having a third hole, at least clamped to the central strut by one of the first or second bolts in the third hole. Including a third piezoelectric plate, the first piezoelectric plate detecting a force along the Z axis of the body, the second piezoelectric plate detecting a force along the X axis of the body, and An accelerometer, wherein the third piezoelectric plate detects a force along the Y-axis of the main body. 13. The accelerometer according to claim 12, wherein the first, second and third piezoelectric plates are shear type piezoelectric plates. 14. The accelerometer of claim 12, wherein the central post includes two bars that are orthogonal to each other and parallel to the Z axis, each bar of the first and second holes. An accelerometer characterized in that it includes one. 15. The accelerometer according to claim 9, wherein the first piezoelectric plate pair is separated by the central support column,
A first pair of masses separated by the first pair of piezoelectric plates, and a third piezoelectric member each having a third hole and clamped to the central column by the second bolt in the third hole. A pair of plates is included; the central post separates the second piezoelectric plate pair from the third piezoelectric plate pair, and the second mass pair is separated by the second and third piezoelectric plate pairs; Accelerometer characterized by. 16. An accelerometer according to claim 15, wherein
Said second and third piezoelectric plate pairs along respective holes,
An accelerometer having a thickness that is half the thickness of the first piezoelectric plate pair along the first hole. 17. The accelerometer of claim 1, wherein the center post is one contact for a first piezoelectric plate pair and one of the first mass pair is the first piezoelectric plate pair. An accelerometer, which is another contact for. 18. The accelerometer according to claim 17, wherein the first piezoelectric plate has a common pole that contacts the central column for detecting linear acceleration. Accelerometer. 19. The accelerometer according to claim 17, wherein the first piezoelectric plate has an opposite pole that contacts the central column for detecting angular acceleration. Total. 20. The accelerometer according to claim 1, wherein a first piezoelectric plate pair separates the first mass body from the central support column and a second mass body separates from the central support column. And a second pair of piezoelectric plates each having a second hole, wherein the first bolt in the second hole clamps the second mass and the piezoelectric plate to the central column. An accelerometer. 21. A body including a central post having a first hole, a piezoelectric plate pair and a mass body pair each having a hole, disposed within the hole and well isolated from the first hole. And even when there is a force transverse to the axis of the first hole, the evenly distributed clamping forces parallel to the axis of the first hole cause the mass and the piezoelectric plate to move to the central column. A symmetric accelerometer comprising: a bolt means for compressing into. 22. The accelerometer according to claim 21, wherein the piezoelectric plate is a shear-type piezoelectric plate having an axis line that intersects the axis line of the hole and is orthogonal to each other. Accelerometer. 23. The accelerometer of claim 21, wherein the body includes a pair of mounting holes that are at right angles to each other in a plane that is at a right angle to the central column, one of the mounting holes being the first hole. An accelerometer characterized by being in a common plane. 24. A shear-type accelerometer for detecting forces along X, Y and Z axes having a central post including first and second bars extending at right angles to each other and parallel to the Z axis. A housing, a first hole formed in the first bar extending parallel to the Y-axis, and a second hole formed in the second bar extending parallel to the X-axis, and X, Shear type piezoelectric plate pairs for detecting forces along the Y and Z axes, first, second and third piezoelectric plate pairs; first, second and third mass bodies; Third piezoelectric plate pair and respective mass bodies on the opposite side of the first bar with a first bolt in the first hole; and the second piezoelectric plate pair and the second mass body with the second bar. A second bolt in the second hole for attaching to Accelerometer that is characterized by 25. The accelerometer according to claim 24, comprising an electrode between each pair of piezoelectric plates. 26. A body comprising a central post having a first hole, at least one first piezoelectric plate and at least one first mass each having a first hole, and a first bolt. A method of assembling an accelerometer comprising: selecting the central support, the piezoelectric plate and the mass so as to have the same external dimensions on at least two sides, the piezoelectric plate being disposed adjacent to the central support. Then, the mass body is disposed adjacent to the piezoelectric plate, the first bolt is inserted into the first hole for alignment, and the first hole is aligned by using the same external dimension,
And a step of tightening the bolt while aligning the mass and the piezoelectric plate to clamp the central strut without contacting the central strut. 27. The method of claim 26, including the step of using an alignment tool having an inner diameter dimension similar to the same outer dimension to align the first hole. how to. 28. The accelerometer of claim 1, wherein the alignment means includes contact between the first bolt and the first hole of the first mass. An accelerometer.