JPH06201505A - Piezoelectric vibration sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] Piezoelectric vibration that has a simple manufacturing process, is low in cost, and is capable of reducing a decrease in directivity due to a displacement of a position where a load body is fixed to a detection unit. To get a sensor. A detector 21 formed by sandwiching both surfaces of a piezoelectric body 31 with a load body side electrode 35a and a pedestal side electrode 35b and further sandwiching both surfaces with a load body side support plate 37a and a pedestal side support plate 7b is mounted on a pedestal 27. In the piezoelectric vibration sensor in which the load body 29 is laminated on the detection unit 21, and the load body 29 is further laminated on the detection unit 21, the load unit of the detection unit 21 is formed with the convex portion 41, and the load body side support plate 37a is formed with the convex portion 41. A piezoelectric vibration sensor having a recess 43 to be fitted therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric type vibration sensor using a piezoelectric body, which has a simple manufacturing process, is low in cost, and is caused by a deviation of a fixing position of a load body to a detecting portion. The present invention relates to a piezoelectric vibration sensor capable of reducing a decrease in directivity.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional piezoelectric vibration sensor. This piezoelectric vibration sensor has a detection unit 21.
And a pedestal 27 having sufficient rigidity for stacking the detection unit 21, and a load body 29 stacked on the detection unit 21.
It is composed of and.

The sensing section 21 has a load body side electrode 35a and a pedestal side electrode 35b made of metal foil fixed to both surfaces of the piezoelectric body 31, and further has a load body side support plate 37a and a pedestal side support plate 37a having sufficient rigidity on both sides. 37b is fixed. The piezoelectric body 31 is made of a material having piezoelectricity. As the material having piezoelectricity, an inorganic piezoelectric material such as lead zirconate titanate (PZT), lead titanate (PT), barium titanate, or a ferroelectric polymer such as polyvinylidene fluoride is used. With such a piezoelectric vibration sensor, it is possible to detect vibration in the direction of the axis G that is orthogonal to the film surface of the piezoelectric body 31 and passes through the center of the load body 29.

By the way, as an example of a method of manufacturing the detection part 21 in the case where the piezoelectric body 31 is made of the above-mentioned inorganic piezoelectric material, powder of the inorganic piezoelectric material is compacted and baked into a plate shape or a cylindrical shape, This fired body is used as the piezoelectric body 31, and then the load body side electrode 35a and the pedestal side electrode 35b are attached to both surfaces of the piezoelectric body 31 with a conductive adhesive, and the both sides are further loaded with an epoxy adhesive. Body side support plate 37a,
The pedestal-side support plates 37b were attached to each other to manufacture the detection units 21 one by one. On the other hand, as an example of a method of manufacturing the detection unit 21 in the case where the piezoelectric body 31 is composed of the above-mentioned ferroelectric polymer, a metal foil is attached to both sides of the ferroelectric polymer sheet, and further, both sides are sufficiently bonded. After bonding materials having various rigidity, this is cut into a chip shape by a cutting means such as a dicing saw, and a large amount of the detection units 21 are collectively manufactured. Then, in order to manufacture a piezoelectric vibration sensor using the detection unit 21 manufactured as described above, after fixing the detection unit 21 on the pedestal 27, the load body 29 is further mounted on the detection unit 21. It was stuck. When the detection unit 21 and the load body 29 are fixed to each other, the axis G which is the center of symmetry of the detection unit 21 and the axis G which is the center of symmetry of the load body 29 are attached.
They were laminated so that they coincided with each other, and they were fixed.

However, in such a piezoelectric type vibration sensor, good characteristics are exhibited if stress is uniformly applied to the entire surface of the piezoelectric body 31, but if the fixing position of the load body 29 to the detecting portion 21 is displaced, the piezoelectric body 31 is piezoelectric. The stress applied to the body 31 becomes non-uniform, resulting in poor directivity. In the case of the compression type piezoelectric vibration sensor, even if vibration is applied in a direction orthogonal to the axis G direction for detecting vibration, if the position where the load body 29 is fixed to the detection portion 21 is accurate, compression and tension are applied. The electric charges due to both stresses are canceled on the same surface, and no output occurs. However, if the fixing position of the load body 29 to the detection unit 21 is deviated, the fulcrum disappears at the center, so that the electric charge is not completely canceled, and as a result, an output is generated in an axial direction other than the axial G direction. Therefore, there is a problem that the directivity is lowered.

In order to prevent such a problem, it is necessary to fix the load body 29 at an accurate position when laminating the load body 29 on the detecting portion 21 during manufacturing of the piezoelectric vibration sensor. It is considered that the load body 29 is laminated at an accurate position on the detection unit 21 using a precision robot or the like, but if an adhesive that does not cure immediately is used, the process proceeds to the next step. There is a risk that the position may be displaced between them, and a jig or the like that constantly presses is required, which complicates the manufacturing process and increases costs.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to simplify the manufacturing process, to reduce the cost, and to reduce the decrease in the directivity due to the deviation of the fixing position of the load body to the detecting portion. To obtain a piezoelectric vibration sensor capable of

[0008]

In the piezoelectric vibration sensor of the present invention, a convex portion is formed on one of the support plate and the load body of the detecting portion, and a concave portion that fits into this convex portion is formed on the other. It is characterized by

[0009]

FIG. 1 shows a first embodiment of the piezoelectric vibration sensor of the present invention. The piezoelectric type vibration sensor of this embodiment differs from the conventional piezoelectric type vibration sensor shown in FIG. 3 in that the load body 29 is provided with a convex portion 41 and the load body side support plate 37a is fitted into the convex portion 41. This is the point that the recess 43 is provided. The same components as those of the conventional example are designated by the same reference numerals to simplify the description.

The convex portion 41 may be formed by partially forming a convex shape when the load body 29 is manufactured, or may be formed separately from the load body 29 and fixed to the load body 29. However, in the case of the latter, it is necessary that the load body 29 and the convex portion 41 are firmly fixed to each other and can be regarded as a rigid body as a whole, and each of them is subjected to vibration and causes another displacement. must not.

The material of the convex portion 41 may be the same as or different from that of the load body 29 as long as it is a rigid body that functions as an inertial mass portion.
If the material is different from 9, the loader 2
It should not cause a displacement other than 9.

As for the shape of the convex portion 41, the convex portion 4
When the load body 29 provided with 1 is cross-sectioned in a myriad of planes orthogonal to the axis G, it is necessary to satisfy the condition of being line-symmetrical with the sensing axis G as the axis of symmetry for all cross sections, for example, a cone. Examples include a shape, a truncated cone shape, a columnar shape, and an annular shape.

The position where such a convex portion 41 is provided is
The axis that passes through the center of the convex portion 41 is provided at a position that coincides with the axis G that is the center of symmetry of the load body 29.

The recess 43 is provided in the load body side support plate 37a, and is formed by forming a part of the load body side support plate 27a into a concave shape or after forming the load body side support plate 27a. May be formed by cutting out in a concave shape.

The shape of the concave portion 43 is the same as that of the convex portion 4 described above.
When the load body side support plate 37a provided with the concave portion 43 is sectioned in a myriad of planes orthogonal to the axis G, all the sections are line-symmetrical with the sensing axis G as the axis of symmetry. It is necessary to satisfy certain conditions such as, for example, an inverted conical shape (shape in which the bottom surface of a cone is an opening surface), an inverted truncated cone shape (shape in which a bottom surface of a truncated cone is an opening surface), a cylindrical shape, a circle. Examples include a ring shape.

The position where such a recess 43 is provided is
The axis passing through the center of the recess 43 is provided at a position that coincides with the axis G that is the center of symmetry of the load body side support plate 37a.

In the piezoelectric vibration sensor of the first embodiment, the load body 29 is provided with the convex portion 41, and the load body side support plate 37a is provided with the concave portion 43 to be fitted into the convex portion 41. When the load body 29 is stacked on the detection unit 21, the protrusion 41 can be easily positioned by simply fitting the protrusion 41 into the recess 43, and if gravity is applied from above (gravity is exactly above). Even if the load body 29 does not hang up), the load body 29 does not shift during the next process.
Can be accurately fixed on the detection unit 21 so that the axis G which is the center of symmetry thereof and the axis G which is the center of symmetry of the detection unit 21 coincide with each other. Therefore, the detection unit 21 of the load body 29
Since the piezoelectric vibration sensor in which the directivity is less likely to be reduced due to the deviation of the fixed position on the top can be obtained, the quality is improved and the yield regarding the directivity is improved. Further, since it is not necessary to use a precise robot or a pressing jig, the manufacturing process can be simplified and the cost can be reduced.

In this first embodiment, the load 29
Although the example in which one convex portion 41 is provided in the above and one concave portion 43 is provided in the load body side support plate 37a has been described, a plurality of convex portions 41 and a plurality of concave portions 43 may be provided. When the load body 29 is provided with a plurality of convex portions 41, the position where the load body 29 provided with the convex portions 41 is crossed on a myriad of planes orthogonal to the axis G is such that the sensing axis G is the axis of symmetry for all cross sections. Any position may be used as long as it satisfies the condition of line symmetry. On the other hand, when the load body side support plate 37a is provided with a plurality of recesses 43, the position is such that when the load body side support plate 37a provided with the recesses 43 is sectioned on a myriad of planes orthogonal to the axis G, the sensing axis Any position may be used as long as it satisfies the condition of line symmetry with G as the axis of symmetry.

As the piezoelectric body 31 in this embodiment,
The same can be done with an inorganic piezoelectric material, a ferroelectric polymer, or a mixture thereof.

Next, a second embodiment of the piezoelectric vibration sensor of the present invention is shown in FIG. In the piezoelectric vibration sensor of the first embodiment shown in FIG. 1, the load body 29 is provided with the convex portion 41, and the load body side support plate 37a is provided with the concave portion 43 fitted into the convex portion 41. In this second embodiment, the load body side support plate 37a is provided with a convex portion 45, and the load body 29 is provided with a concave portion 47 that fits into the convex portion 45.

The convex portion 45 is formed by partially forming a convex shape when the load body side support plate 37a is manufactured, or is formed separately from the load body side support plate 37a and fixed to the load body side support plate 37. However, in the latter case, it is necessary that the load body side support plate 37a and the convex portion 45 are firmly fixed to each other and can be regarded as a rigid body as a whole. If the convex portion 45 is made of a rigid body,
The material may be the same as or different from that of the load body side support plate 37a.

As for the shape of the convex portion 45, the convex portion 4
When the load body side support plate 37a provided with No. 5 is cross-sectioned in a myriad of planes orthogonal to the axis G, it is necessary to satisfy the condition of being line-symmetrical with the sensing axis G as the axis of symmetry for all the cross sections. , A conical shape, a truncated cone shape, a columnar shape, an annular shape, and the like.

The position where such a convex portion 45 is provided is
An axis passing through this center is provided at a position that coincides with an axis G that is the center of symmetry of the load body side support plate 37a.

The concave portion 47 is provided in the load body 29. A part of the load body 29 is formed in a concave shape when the load body 29 is manufactured, or after the load body 29 is manufactured, a part thereof is cut out in a concave shape. It may be produced.

The shape of the concave portion 47 is the same as the convex portion 4
5 is a fitting shape, and when the load body 29 provided with the recess 47 is sectioned on a myriad of planes orthogonal to the axis G, all sections are line-symmetrical with the sensing axis G as the axis of symmetry. Must meet the conditions, eg
Examples thereof include an inverted conical shape (a shape in which a bottom surface of a cone is an opening surface), an inverted conical shape (a shape in which a bottom surface of a circular truncated cone is an opening surface), a cylindrical shape, and an annular shape.

The position where such a recess 47 is provided is
The axis passing through this center is provided at a position that coincides with the axis G that is the center of symmetry of the load 29.

In the piezoelectric type vibration sensor of the second embodiment, the load body side support plate 37a is provided with the convex portion 45, and the load body 29 is provided with the concave portion 47 fitted into the convex portion 45. When the load body 29 is stacked on the detection section 21, the projection 45 can be easily positioned by simply fitting the projection 45 into the recess 47, and the same effect as that of the first embodiment can be obtained.
In the second embodiment, an example in which the load body side support plate 37a is provided with one convex portion 45 and the load body 29 is provided with one concave portion 47 has been described, but a plurality of convex portions 45 and concave portions 47 are provided. You may provide one by one. When a plurality of convex portions 45 are provided on the load body side support plate 37a, the position is
The load body side support plate 37a provided with the convex portion 45 is attached to the axis G.
It suffices if the position satisfies the condition that it is line-symmetrical with respect to the sensing axis G as the axis of symmetry with respect to all the cross-sections when the cross-section is taken along a myriad of planes orthogonal to On the other hand, when the load body 29 is provided with a plurality of recesses 47, the position of the load body 29 provided with the recesses 47 is a symmetry axis with respect to the sensing axis G for all sections when the load body 29 is sectioned in a number of planes orthogonal to the axis G. Any position may be used as long as it satisfies the condition of line symmetry.

Specific examples will be shown below. (Example 1) First, an epoxy adhesive with a practical curing time of 6 hours was used on both sides of a square lead zirconate titanate plate having a thickness of 0.5 mm and a side of 15 mm, and a thickness of 30 μm.
A square-shaped copper foil having a length of m and a side of 15 mm was attached. Further, a square glass epoxy plate having a thickness of 1.5 mm and a side of 15 mm was adhered to both surfaces thereof using the same epoxy adhesive as that used previously. The glass epoxy plate here has a depth of 0.2, which is partly formed in a concave shape in advance.
mm, the diameter of the opening was 0.2 mm, and the conical recess 43 was provided. Then, it cut | disconnected using the dicing saw and produced the square-shaped detection part 21 with a side of 5 mm. The load body side support plate 37a of the obtained detector 21 was provided with the recess 43 at a position where the axis passing through the center of the recess 43 coincides with the axis G which is the center of symmetry of the load body side support plate 37a.

Next, the pedestal side support plate 3 of the detection unit 21.
After applying the same epoxy adhesive as that used previously to 7b, this pedestal side support plate 37b was fixed on a square aluminum block pedestal 27 having a thickness of 5 mm and a side of 1 cm. Then, the same epoxy-based adhesive as that used previously is applied to the load-side support plate 37a of the detection unit 21, and a square load 29 having a mass of 1 g, a thickness of 2 mm, and a side of 6 mm is laminated on this. The adhesive was cured in a horizontal state to obtain a piezoelectric vibration sensor similar to that shown in FIG. As the load body 29 used here, one having a convex portion 41 formed into a convex shape when the load body 29 is manufactured and having a shape fitting into the concave portion 43 is used. The convex portion 41 was provided at a position where the axis passing through the center thereof coincides with the axis G which is the center of symmetry of the load body 29. Load body 29 and load body side support plate 3
An XY robot is used to fix the load 29 to the 7a.
Was placed on the load body side support plate 37a, the convex portion 41 and the concave portion 43 were fitted, and the load body 29 was pressed, and no particular pressure was applied. This was used as the piezoelectric vibration sensor of Example 1.

After 6 hours, the load body side electrode 35
a and the pedestal side electrode 35b are electrically connected to the impedance exchange circuit, and the piezoelectric type vibration sensor of the first embodiment is provided with the axis G.
The directivity was evaluated by taking the ratio of both when the vibration of 80 Hz and 1 G was applied in the direction of the axis and the direction of the other axis. The results are shown in Table 1 below.

(Embodiment 2) When an epoxy-based adhesive having a practical curing time of 6 hours is applied to the load body side support plate 37a of the detecting portion 21 and the load body 29 is laminated on this to cure the adhesive, A piezoelectric vibration sensor was obtained in the same manner as in Example 1 except that curing was performed by tilting at 5 °. This was used as the piezoelectric vibration sensor of Example 2. Then, in the same manner as in Example 1, the directivity of the piezoelectric vibration sensor of Example 2 was evaluated. The results are shown in Table 1 below.

(Embodiment 3) When an epoxy-based adhesive having a practical curing time of 6 hours is applied to the load body side support plate 37a of the detecting portion 21 and the load body 29 is laminated on this to cure the adhesive, A piezoelectric vibration sensor was obtained in the same manner as in Example 1 except that the resin was cured by tilting at 10 °. This was used as the piezoelectric vibration sensor of Example 3. Then, in the same manner as in Example 1, the directivity of the piezoelectric vibration sensor of Example 3 was evaluated. The results are shown in Table 1 below.

(Comparative Example 1) Example 1 except that the load body 29 is not provided with the convex portion 41 and the load body side support plate 37a is not provided with the concave portion 43.
A piezoelectric vibration sensor was obtained in the same manner as in. Comparative Example 1
Of the piezoelectric vibration sensor. Then, in the same manner as in Example 1, the directivity of the piezoelectric vibration sensor of Comparative Example 1 was evaluated. The results are shown in Table 1 below.

(Comparative Example 2) Example 2 except that the load body 29 is not provided with the convex portion 41 and the load body side support plate 37a is not provided with the concave portion 43.
A piezoelectric vibration sensor was obtained in the same manner as in. This is Comparative Example 2
Of the piezoelectric vibration sensor. Then, in the same manner as in Example 1, the directivity of the piezoelectric vibration sensor of Comparative Example 2 was evaluated. The results are shown in Table 1 below.

(Comparative Example 3) Example 3 is different except that the load body 29 is not provided with the convex portion 41 and the load body side support plate 37a is not provided with the concave portion 43.
A piezoelectric vibration sensor was obtained in the same manner as in. Comparative Example 3
Of the piezoelectric vibration sensor. Then, in the same manner as in Example 1, the directivity of the piezoelectric vibration sensor of Comparative Example 3 was evaluated. The results are shown in Table 1 below.

[0036]

[Table 1]

As is clear from the results shown in Table 1, the piezoelectric vibration sensors of Examples 1 to 3 have higher directivity than the piezoelectric vibration sensors of Comparative Examples 1 to 3. .

[0038]

As described above, in the piezoelectric type vibration sensor of the present invention, the convex portion is formed on one of the support plate of the detecting portion and the load body, and the concave portion which is fitted to the convex portion is formed on the other. Therefore, when stacking the load body on the detection portion, it is possible to easily position by simply fitting the convex portion into the concave portion, and if gravity is applied from above, proceed to the next step. Since the load body is not displaced in the meantime, the load body can be accurately fixed on the detection unit. Therefore, it is possible to obtain the piezoelectric vibration sensor in which the directivity is less reduced due to the deviation of the fixing position of the load body on the detection unit.
Improves quality and improves directivity yield. Further, since it is not necessary to use a precise robot or a pressing jig, the manufacturing process can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a piezoelectric vibration sensor of a first embodiment.

FIG. 2 is a vertical sectional view showing a piezoelectric vibration sensor of a second embodiment.

FIG. 3 is a vertical sectional view showing a conventional piezoelectric vibration sensor.

[Explanation of symbols]

21 ... Detecting unit, 27 ... Pedestal, 29 ... Load body, 31 ...
Piezoelectric body, 35a ... Load body side electrode, 35b ... Pedestal side electrode, 37a ... Load body side support plate, 37b ... Pedestal side support plate, G ... Shaft, 41 ... Convex portion , 43 ... concave portion, 45 ... convex portion, 47 ... concave portion

Claims (1)

[Claims] 1. A piezoelectric type in which a piezoelectric body is formed by sandwiching both sides of a piezoelectric body with electrodes, and further sandwiching both sides with a support plate to form a detection unit on a pedestal, and further stacking a load body on the detection unit. In the vibration sensor, the piezoelectric type vibration sensor is characterized in that a convex portion is formed on one of the support plate of the detection portion and the load body, and a concave portion that fits into the convex portion is formed on the other.