JPH06230025A - Piezoelectric vibration sensor - Google Patents

Abstract

PURPOSE:To reduce the dispersion of sensitivity between sensors, improve the mass production adaptability of the detecting part, and improve temperature characteristic in piezoelectric output. CONSTITUTION:In this piezoelectric vibration sensor 1 in which a pedestal 2 rigidly fitted to an object to be measured, a detecting part 3 fixedly secured on the measuring face perpendicular to the detecting axis G of the pedestal 2, and a load body 4 consisting of a rigid body acting as an inertia mass part fixedly secured on the detecting part 3 are provided, and the detecting part 3 is constituted by fixedly securing a first electrode 5a and a second electrode 5b on both faces of a piezoelectric body layer 6 through adhesive layers 6a, 6b, it is featured that sheet-like adhesive material containing denaturated acryl- series resin as a main component is used for the adhesive layers 6a, 6b constituting the detecting part 3. Consequently, the temperature characteristic can be remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibration sensor using an inorganic piezoelectric material, and more particularly to a piezoelectric vibration sensor with improved temperature characteristics and production efficiency.

[0002]

2. Description of the Related Art A conventional piezoelectric vibration sensor using an inorganic piezoelectric material has advantages such as high accuracy and a wide usable temperature range. However, in this piezoelectric vibration sensor, lead zirconate titanate (PZT), lead titanate (PT), barium titanate (BAT), and other powders are pressed and solidified and baked into a plate or disk. The detection part was produced using the individual fired bodies. A piezoelectric vibration sensor using such an inorganic piezoelectric material has a compression type or a shear type as a sensor method. An inefficient method of making was taken.

Therefore, in order to improve the inefficient productivity of the above-mentioned piezoelectric type vibration sensor detection section, the inventors of the present invention apply an adhesive to both surfaces of the piezoelectric body as a mass production method, and Propose a method to mass-produce the sensing parts in a batch by fixing the electrodes of the above, and depending on the intended use, after interposing a supporting plate between the electrodes and the piezoelectric body, cutting this into chips with a cutting means such as a dicing saw. did.

As shown in FIG. 3 (a), the piezoelectric vibration sensor manufactured by the above method has a pedestal 21 rigidly attached to the object to be measured and a detection axis G "of the pedestal 21. A detection unit 22 fixed to a measurement surface perpendicular to
A load body 23 made of a rigid body that is fixed on the detection unit 22 and acts as an inertial mass unit is provided.
As shown in (b), the adhesive layers 30 are formed on both sides of the piezoelectric body 24.
plate electrodes 25a and 25b formed through a and 30b
In some cases, the plate electrodes 25a and 25b are provided with support plates 26a and 26b made of a plate-shaped rigid body on the surface thereof, and the planar shape of the piezoelectric body 24 is parallel to the measurement surface. The load axis 23 is point-symmetric with respect to the detection axis G ″, and the plane shape of the surface of the load body 23 in contact with the detection part 22 is point-symmetric with respect to the detection axis G ″. When a section is taken along a myriad of planes passing through the axis G ″ and perpendicular to the measurement surface, all the sections are line-symmetrical with the detection axis G ″ as the axis of symmetry. Therefore,
The piezoelectric vibration sensor 20 as described above is lightweight and compact,
It has excellent shock resistance and the output can be easily adjusted.
And the production efficiency was good.

[0005]

However, in the piezoelectric vibration sensor 20 as described above, the adhesive layers 30a and 30b formed between the piezoelectric body 24 of the detection portion 22 and the plate electrodes 25a and 25b, respectively. Is formed by a coating operation, and there is a problem in that variations in the film thickness cause variations in sensitivity among the sensors. Further, the piezoelectric vibration sensor 20 as described above
In the case where an inorganic piezoelectric material is used for the piezoelectric material layer 24 of the detection unit 22, the piezoelectric material 24 and the plate electrodes 25a, 2
There is a problem in that the temperature characteristics of the adhesive layers 30a and 30b formed between 5b influence the temperature characteristics of the piezoelectric body 24, leading to a decrease in the temperature characteristics in voltage output.

The cause of the phenomenon in which the temperature characteristics of the adhesive layers 30a and 30b affect the temperature characteristics of the piezoelectric body 24 and causes the temperature characteristics to decrease in voltage output as described above is explained as follows. For example, if the total capacitance formed by the three layers of the piezoelectric body 24 in each chip manufactured by the above-described method and the adhesive layers 30a and 30b formed by the adhesive applied to both surfaces thereof is C, this total capacitance C is the electric capacity C _p of the piezoelectric body 24, and the adhesive layer 30.
It is represented by the following formula from the electric capacities C _a of a and 30 b. C = 1 / {(1 / C _p ) + (2 / C _a )} = C _p C _a / (C
_a + 2C _p )

Therefore, it is clear from the above equation that C _p
When the value of is larger than the value of C _a , the total capacitance C is easily influenced by the value of C _a . Therefore, in such a case, the temperature characteristics of the chip strongly reflect the temperature characteristics of C _a . That is, when the output is taken out as the voltage output V, V =
It is Q / C, and the temperature characteristic of C is directly reflected in the output. However, when the piezoelectric element is formed of an organic piezoelectric body, wherein C _p is not so large in comparison with the C _a. Therefore, in the piezoelectric type vibration sensor using the organic piezoelectric material, there is often no problem even if the mass production method of the detection unit as described above is used.

Therefore, the present invention has been made in view of the above circumstances, and aims to reduce the variation in the sensitivity between sensors, improve the mass productivity of the detection unit, and improve the temperature characteristics in voltage output. An object of the present invention is to provide a piezoelectric vibration sensor.

[0009]

In order to solve the above-mentioned problems, a piezoelectric vibration sensor according to a first aspect of the present invention has a pedestal rigidly attached to an object to be measured and a measurement surface perpendicular to the detection axis of the pedestal. And a load member made of a rigid body that acts as an inertial mass unit fixed on the detection unit, and the detection unit is a first electrode via an adhesive layer on both front and back surfaces of the piezoelectric layer, A piezoelectric vibration sensor having a second electrode fixed thereto is characterized in that a sheet-shaped adhesive material containing a modified acrylic resin as a main component is used for an adhesive layer constituting the detection section.

In order to solve the above-mentioned problems, the piezoelectric vibration sensor according to a second aspect of the present invention is an epoxy-based vibration sensor in which the adhesive layer in the piezoelectric vibration sensor according to the first aspect contains a butadiene component in an amount of 30% to 70%. A sheet-shaped adhesive material made of resin is used.

[0011]

According to the piezoelectric vibration sensor of the present invention, in the piezoelectric layer that constitutes the detection portion and the first and second electrodes that are adhered to both surfaces of the piezoelectric layer through the adhesive layer, the adhesive layer is sheet-shaped. By avoiding the variation in the film thickness of the adhesive layer by using the adhesive material of, by making the film thickness of the adhesive layer uniform,
It is possible to reduce variations in sensitivity between sensors. Further, by using an adhesive material made of a modified acrylic resin or an adhesive material made of an epoxy resin containing a butadiene component in a proportion of 30% to 70% as the adhesive material forming the adhesive layer, The difference between the capacitance and the capacitance of the piezoelectric body is reduced to a negligible level,
It is possible to prevent the temperature characteristic of the adhesive layer from affecting the temperature characteristic of the piezoelectric layer. Therefore, the piezoelectric vibration sensor of the present invention, regardless of the constituent material of the piezoelectric layer,
The temperature characteristics can be remarkably improved. Also,
When an adhesive material made of an epoxy-based resin containing 30% or more of a butadiene component is used for the adhesive layer, the butadiene component has a property of imparting elasticity to the adhesive layer, so that the impact resistance of the sensor is improved. It is possible to improve.

Further, in the past, since the film thickness of the adhesive layer was proportional to its electric capacity, the increase of the film thickness of the adhesive layer became a factor to widen the difference from the electric capacity of the piezoelectric body.
In the present invention, the same effect as described above can be obtained regardless of the film thickness of the adhesive layer. That is, the adhesive layer of the piezoelectric vibration sensor according to the present invention is made of a modified acrylic resin as an adhesive material or an epoxy resin as an adhesive material containing a butadiene component in an amount of 30% to 70%. This is because the adhesive layer has an effect as a resistance component in this piezoelectric vibration sensor, and an effect as a capacitance component as in the past is significantly reduced.

Further, the above effect is very large when an inorganic piezoelectric material is used as the piezoelectric material. Since the inorganic piezoelectric material generally has a large electric capacity,
A factor that causes a large difference from the electric capacity of the substance forming the adhesive layer, the temperature characteristic of the adhesive layer largely influences the temperature characteristic of the piezoelectric layer, and causes the temperature characteristic of the piezoelectric vibration sensor to deteriorate. It was. But,
As in the present invention, by forming the adhesive layer from an adhesive material made of a modified acrylic resin or an adhesive material made of an epoxy resin containing a butadiene component in a proportion of 30% to 70%, the adhesive layer and the piezoelectric body are formed. The difference in the electric capacities of the layers is reduced to a negligible level, and it is possible to significantly improve the temperature characteristics.

Further, in the piezoelectric vibration sensor of the present invention, the conventional mass production method can be applied as it is to the production form of the detecting portion, and the liquid adhesive is not used when forming the adhesive layer, and the sheet is used. Since the adhesive material in the shape of a strip is used, it is possible to improve the workability and improve the production efficiency.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows a piezoelectric vibration sensor 1 according to this embodiment. The piezoelectric vibration sensor 1 according to the present embodiment has a pedestal 2 that is rigidly attached to an object to be measured, a detection unit 3 that is fixed to a measurement surface of the pedestal 2 that is perpendicular to a detection axis G, and a detection unit 3 above the detection unit 3. And a load body 4 made of a rigid body that is fixed to and acts as an inertial weight part. The material of the pedestal 2 may be any material having sufficient rigidity such as fiber reinforced resin and metal. As the material of the load body 4, it is desirable to use a material having a relatively large specific gravity such as brass and other metals.

As shown in FIG. 1 (b), the detecting portion 3 has sheet-like adhesive layers 6a and 6b attached to both sides of a piezoelectric layer 6 made of an inorganic piezoelectric material, and the respective adhesive layers 6a and 6a. 6
The first electrode 5a and the second electrode 5 which are fixedly attached via b
b.

PZT, PT, BAT or the like is used as the inorganic piezoelectric material used as the material of the piezoelectric layer 6, and a modified acrylic resin or a butadiene component is used as the adhesive material for forming the adhesive layers 6a and 6b. 30% to 70%
The epoxy resin contained in the ratio of is used. Further, as the material forming the first electrode 5a and the second electrode 5b, copper foil, tin foil or the like is used. Depending on the intended use, support plates made of plate-shaped rigid bodies may be provided on both the front and back surfaces of the detection unit 3 having the above-mentioned configuration.

As described above, in the piezoelectric vibration sensor 1 according to this embodiment, the adhesive layers 6a and 6b formed on both sides of the piezoelectric layer 6 are made of a sheet-like modified acrylic resin or butadiene. 30% to 70% of ingredients
It is characterized in that an adhesive material made of an epoxy-based resin contained in the above ratio is used. By using a sheet-shaped adhesive material for the adhesive layers 6a and 6b, the adhesive layer 6
The adhesive layers 6a and 6b are avoided by avoiding variations in the film thickness of a and 6b.
By making the film thickness of the sensor uniform, it is possible to reduce variations in sensitivity between sensors. Then, the adhesive layer 6
By using a modified acrylic resin or an epoxy resin containing a butadiene component in a proportion of 30% to 70% as a material forming a and 6b, the total electric capacitance C of the detection unit 3 can be increased by the adhesive layer 6a. , 6b, the influence of the electric capacitance C _a can be avoided. That is, by forming the adhesive layers 6a and 6b from an adhesive material made of a modified acrylic resin or an epoxy resin containing a butadiene component in a proportion of 30% to 70%, the capacitance component is converted into a resistance component. Thus, the total capacitance C of the piezoelectric vibration sensor 1 in this embodiment is made equal to the capacitance C _p of the piezoelectric layer 6 itself. Therefore,
The piezoelectric type vibration sensor 1 in this embodiment can reflect only the temperature characteristic of the piezoelectric layer 6 itself in its temperature characteristic. Therefore, the above-described piezoelectric vibration sensor 1 of the present embodiment can improve its temperature characteristics. Further, in the piezoelectric vibration sensor 1 of the present embodiment, when the epoxy resin containing 30% or more of a butadiene component is used as the sheet-shaped adhesive material forming the adhesive layers 6a and 6b, the butadiene component is ,
Since the adhesive layers 6a and 6b have the property of imparting elasticity, it is possible to provide a piezoelectric vibration sensor having good impact resistance.

Further, in the piezoelectric type vibration sensor 1 of the present embodiment having the above-mentioned structure, as a method of manufacturing the detecting portion 3,
The mass production method described in the above can be applied as it is, and since the sheet-shaped adhesive material is used when forming the adhesive layers 6a and 6b, the workability is improved and the production efficiency is improved. Is possible.

Below, specific examples 1 to 4 of the piezoelectric vibration sensor 1 of the present embodiment described above were produced. Regarding these specific examples 1 to 4 and comparative examples 1 to 5 shown below, variations in sensitivity and sensitivity The temperature drift was measured. In addition, the impact resistance of the piezoelectric vibration sensor of Specific Examples 2 to 4 containing a butadiene resin in the adhesive layer component and the piezoelectric vibration sensor of Comparative Example 2 were also measured. (Specific Example) As shown in FIG. 2, in the piezoelectric vibration sensor 10 of this specific example, a chip 18 having the following structure is
cm square, fixed to a pedestal 12 made of aluminum block having a thickness of 5 mm, 6 mm square on the detection part 13 of the chip 18,
A brass load body 4 having a thickness of 2 mm and a weight of about 0.6 g is bonded. The chip is composed of a detection unit 13 and support plates 17a and 17b sandwiching the detection unit 13, and the detection unit 13 has a sheet-like shape on both sides of a film conductor 16 made of PZT of 15 mm square and 0.5 mm thickness. Adhesive layers 16a, 1
6b is attached, and via the adhesive layers 16a and 16b,
The first electrode 15a and the second electrode 15b made of copper foil having a foil thickness of 30 μm are fixed to each other. The detection unit 13 is sandwiched by a support plate made of a glass epoxy plate (t = 1.5 mm) via the adhesive layers 13a, 13b having the same structure as the adhesive layers 16a, 16b.

In the specific example having the above-mentioned structure, the adhesive layers 16a, 16b, 13a, 13b using the modified acrylic resin are the specific examples 1, and the epoxy resin containing 30% of the butadiene component is used. Example 2 is a case where an epoxy resin containing 50% butadiene component is used as Example 3 and a case where an epoxy resin containing 60% butadiene component is used is Example 4 is shown. It was created.

Then, as a comparative example, the adhesive layer 16a, 16b, 13a, 13b of the above-mentioned specific example is formed by applying a liquid modified acrylic resin, and a comparative example 1, a liquid epoxy resin is applied. Comparative Example 2, a sheet-like sheet made of an epoxy resin containing 20% butadiene component in Comparative Example 2, formed by applying a liquid epoxy resin containing 50% butadiene component. Comparative example 4 was formed from an adhesive material, and comparative example 5 was formed from a sheet-shaped adhesive material made of an epoxy resin containing 80% of a butadiene component.
As a result, each piezoelectric vibration sensor was created.

Then, the above specific examples 1 to 4 and comparative examples 1 to 5
50 piezoelectric vibration sensors are prepared for each, and these are connected to an impedance conversion circuit to detect variations in sensitivity,
The change in sensitivity with temperature was measured. In addition, the above specific example 2
About 5 and comparative example 2, impact resistance was also measured. The results are shown in Table 1. Regarding the variation in sensitivity, the variation width in which the sensitivities of all the sensors are included is described with reference to the average value of the sensitivities of the 50 sensors in each of the specific examples 1 to 4 and the comparative examples 1 to 5. Regarding the temperature drift of the sensitivity, -3 of the 50 sensors of each of the specific examples 1 to 4 and the comparative examples 1 to 5 based on the sensitivity of 25 ° C is used.
The range of change in sensitivity from 0 ° C to 100 ° C is described. Regarding the impact resistance, the ratio of the broken sensors when 50 sensors of each of the above specific examples 1 to 4 and comparative examples 1 to 5 were dropped together with the aluminum block from the height of 1 m onto the concrete was shown.

[0024]

[Table 1]

As is clear from Table 1, in the piezoelectric vibration sensors of Examples 1 to 4 of the present invention, it was recognized that the variation in sensitivity between the sensors was remarkably reduced. And
As for the temperature drift of sensitivity, it was confirmed that the temperature drift was significantly reduced as compared with Comparative Examples 1 to 5. When Comparative Examples 1 to 5 are examined from Table 1 below, as in Comparative Example 1, when a liquid modified acrylic resin is used for the adhesive layers 16a, 16b, 13a, 13b, or as in Comparative Example 2, The adhesive layers 16a, 16b, 13a, 13
When a liquid epoxy resin is used for b, it is clear that the variation of the sensitivity and the temperature change of the sensitivity are large. As in Comparative Example 3, the adhesive layers 16a, 16b,
When a liquid epoxy resin containing 50% of a butadiene component is used for 13a and 13b, it is possible to reduce the temperature drift of the sensitivity and improve the impact resistance, but use a liquid adhesive material. As a result, it can be seen that the variation in sensitivity cannot be reduced because of the presence. As in Comparative Example 4, the adhesive layers 16a, 16b, 13a and 13b were replaced with 20
When the sheet-shaped epoxy resin containing the butadiene component of 30% is used, the sheet-shaped adhesive material is used, so that it is possible to reduce the variation in sensitivity. It is understood that the temperature drift of the sensitivity and the impact resistance cannot be improved because of the following. The adhesive layer 1 as in Comparative Example 5
When 6a, 16b, 13a, and 13b are made of a sheet-shaped epoxy resin containing 80% of a butadiene component, since a sheet-shaped adhesive material is used, it is possible to reduce variations in sensitivity. In addition, since the adhesive layer material contains 30% or more of a butadiene component, it is possible to improve impact resistance. But,
It can be seen that the temperature drift of sensitivity cannot be reduced because the butadiene component contained in the adhesive material forming the adhesive layer exceeds 70%.

[0026]

As described above, according to the piezoelectric type vibration sensor of the present invention, the piezoelectric layer constituting the detecting portion and the first and second electrodes which are adhered to both surfaces of the piezoelectric layer via the adhesive layers. In the above, by using a sheet-shaped adhesive material for the adhesive layer, it is possible to avoid the variation in the film thickness of the adhesive layer and to make the film thickness of the adhesive layer uniform, thereby reducing the variation in the sensitivity between the sensors. It is possible. Further, by using an adhesive material made of a modified acrylic resin or an adhesive material made of an epoxy resin containing a butadiene component in a proportion of 30% to 70% as the adhesive material forming the adhesive layer, The difference between the electric capacity and the electric capacity of the piezoelectric body can be reduced to a negligible degree, and the temperature characteristic of the adhesive layer can be prevented from affecting the temperature characteristic of the piezoelectric layer. Therefore, the piezoelectric vibration sensor of the present invention can significantly improve the temperature characteristics regardless of the constituent material of the piezoelectric layer. Further, when an adhesive material made of an epoxy resin containing 30% or more of a butadiene component is used for the adhesive layer, the butadiene component has a property of imparting elasticity to the adhesive layer, so that the impact resistance of the sensor is high. It is possible to improve the sex.

Further, in the past, since the film thickness of the adhesive layer was proportional to its electric capacity, the increase of the film thickness of the adhesive layer became a factor to widen the difference from the electric capacity of the piezoelectric body.
In the present invention, the same effect as described above can be obtained regardless of the film thickness of the adhesive layer. That is, the adhesive layer of the piezoelectric vibration sensor according to the present invention is made of a modified acrylic resin as an adhesive material or an epoxy resin as an adhesive material containing a butadiene component in an amount of 30% to 70%. This is because the adhesive layer has an effect as a resistance component in this piezoelectric vibration sensor, and an effect as a capacitance component as in the past is significantly reduced.

The above-mentioned effects are very large when an inorganic piezoelectric material is used as the piezoelectric material. Since the inorganic piezoelectric material generally has a large electric capacity,
A factor that causes a large difference from the electric capacity of the substance forming the adhesive layer, the temperature characteristic of the adhesive layer largely influences the temperature characteristic of the piezoelectric layer, and causes the temperature characteristic of the piezoelectric vibration sensor to deteriorate. It was. But,
As in the present invention, by forming the adhesive layer from an adhesive material made of a modified acrylic resin or an adhesive material made of an epoxy resin containing a butadiene component in a proportion of 30% to 70%, the adhesive layer and the piezoelectric body are formed. The difference in the electric capacities of the layers is reduced to a negligible level, and it is possible to significantly improve the temperature characteristics.

Further, in the piezoelectric vibration sensor according to the present invention, the conventional mass production method can be applied as it is to the production form of the detecting portion, and the liquid adhesive is not used when forming the adhesive layer, and the sheet is used. Since the adhesive material in the shape of a strip is used, it is possible to improve the workability and improve the production efficiency.

[Brief description of drawings]

FIG. 1A is a perspective view of a piezoelectric vibration sensor according to an embodiment of the present invention. Figure 1 (b)
[FIG. 3] is an exploded perspective view of a detection portion of the piezoelectric vibration sensor according to the embodiment of the present invention.

FIG. 2A is a perspective view of a piezoelectric vibration sensor of a specific example of this embodiment. Figure 2 (b)
[FIG. 6] is an exploded perspective view of a detection portion of a piezoelectric vibration sensor of a specific example in this embodiment.

FIG. 3A is a perspective view of a conventional piezoelectric vibration sensor. FIG. 3B is an exploded perspective view of the detection unit of the conventional piezoelectric vibration sensor.

[Explanation of symbols]

1, 10, 20 ... Piezoelectric vibration sensor 6a, 6b, 13
a, 13b, 16a, 16b, 30a, 30b ... Adhesive layers 17a, 17b ... Support plates 2, 12, 21 ... Pedestal 3,
13, 22 ... Detection unit 4, 14, 23 ... Load body 5a,
15a, 25a ... 1st electrode 5b, 15b, 25b ... 2nd electrode 6, 16, 22 ... Piezoelectric layer G, G ', G "...
Detection axis

Claims (2)

[Claims] 1. A pedestal rigidly attached to an object to be measured,
The pedestal has a detection part fixed to a measurement surface perpendicular to the detection axis and a load body made of a rigid body fixed to the detection part and acting as an inertial mass part. In a piezoelectric vibration sensor in which a first electrode and a second electrode are fixed to each other via an adhesive layer on both sides, a sheet-shaped adhesive material containing a modified acrylic resin as a main component is used for the adhesive layer forming the detection section. Piezoelectric vibration sensor characterized by. 2. The piezoelectric vibration sensor according to claim 1, wherein a sheet-shaped adhesive material made of an epoxy resin containing a butadiene component in a proportion of 30% to 70% is used for the adhesive layer in the piezoelectric vibration sensor. Sensor.