JPH06148225A - Piezoelectric vibration sensor - Google Patents

Abstract

PURPOSE:To provide a piezoelectric vibration sensor of constant quality by reducing the irregularity of output voltages. CONSTITUTION:Electrodes 27a, 27b are provided at both faces of a piezoelectric body 25 via adhesive layers 26a, 26b in a detecting part 23. The detecting part 23 is laminated on a stage 22, and a load body 24 is layered thereon, whereby a piezoelectric vibration sensor 21 is obtained. The adhesive layers 26a, 26b of the detecting part 23 of the sensor 21 are formed of an adhesive having the viscosity of not smaller than 5X10<4>cp and not larger than 12X10<4>cp before it is set.

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 a piezoelectric body, and reduces variations in output voltage between the piezoelectric vibration sensors.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional piezoelectric vibration sensor. Reference numeral 21 in the figure is a piezoelectric vibration sensor. The piezoelectric vibration sensor 21 is roughly composed of a pedestal 22, a detection unit 23, and a load body 24. The detection unit 23 includes electrodes 27a, made of a metal foil, on both surfaces of the piezoelectric body 25, with adhesive layers 26a, 26b made of a conductive adhesive interposed therebetween.
27b is fixed. The piezoelectric body 25 is made of a material having piezoelectricity. As the material having piezoelectricity, an inorganic piezoelectric substance such as lead zirconate titanate (PZT), lead titanate (PT), barium titanate, or the like,
Ferroelectric polymers such as polyvinylidene fluoride are used. In this piezoelectric vibration sensor 21, an axis orthogonal to the film surface of the piezoelectric body 25 and passing through the center of the load body 24 is a vibration sensing axis G. By mounting the pedestal 22 on the object to be measured, It is possible to detect a vibration change in the sense axis G direction of the object to be measured.

By the way, as an example of a method for producing the detecting portion 23 in the case where the piezoelectric body 25 is composed of the above-mentioned ferroelectric polymer, after a metal foil is attached to both sides of the ferroelectric polymer sheet ( Further, a support plate made of a material having sufficient rigidity may be attached to both surfaces thereof), and this is cut into chips by a cutting means such as a dicing saw, and a large number of the detection units 23 are manufactured at one time. . On the other hand, the detection unit 2 when the piezoelectric body 25 is made of the above-mentioned inorganic piezoelectric material
As an example of the method of manufacturing 3, the powder of the inorganic piezoelectric material is pressed and solidified and baked into a plate shape or a cylindrical shape, the baked body is used as the piezoelectric body 25, and then conductive bonding is performed on both surfaces of the piezoelectric body 25. The electrodes 27a and 27b were attached to each other by using an agent, and the detection units 23 were manufactured one by one.

However, when the same vibration is applied to the piezoelectric type vibration sensor using the piezoelectric body 25 made of the above-mentioned powder of the inorganic piezoelectric material, the output voltage varies among the piezoelectric type vibration sensors, and a constant quality is obtained. However, there is a drawback in that the piezoelectric type vibration sensor cannot be obtained.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a piezoelectric vibration sensor having a constant quality by reducing the variation in output voltage caused by the piezoelectric vibration sensor.

[0006]

[Means for Solving the Problems] In the piezoelectric vibration sensor, as a material forming an adhesive layer of a detecting portion,
This can be solved by using an adhesive having a viscosity before curing of 5 × 10 ⁴ cp or more and 12 × 10 ⁴ cp or less.

An example of the piezoelectric vibration sensor of the present invention will be described in detail below with reference to FIG. In the piezoelectric vibration sensor 21 of this example, the adhesive layer 26 a of the detection unit 23,
26b has a viscosity before curing of 5 × 10 ⁴ cp or more 12 × 1
It is composed of an adhesive having a size of 0 ⁴ cp or less.

When vibration in the direction of the sensing axis G is applied to the piezoelectric type vibration sensor 21, electric charges are generated in the piezoelectric body 25 of the detecting section 23. This charge is applied to the adhesive layers 26a, 26 on both surfaces of the piezoelectric body 25.
It is taken out as an output voltage from the electrodes 27a and 27b via b. The output voltage and the charge amount have a relationship as shown in the following general formula (I).

V = Q / C _total (I) V: output voltage Q: amount of charge C _total : capacitance of detection unit

The capacitance (C _total ) of the detection unit 23 of the above general formula (I) is represented by the following general formula (II).

By the way, the conventional piezoelectric vibration sensor 21 using the piezoelectric body 25 made of powder of the inorganic piezoelectric material has a problem that the output voltage varies among the piezoelectric vibration sensors 21. As a result of intensive studies, the present inventors have found the cause. That is, since the surface of the piezoelectric body 25 made of a powder of an inorganic piezoelectric material is porous, when a normal adhesive is applied to the piezoelectric body 25 as a material forming the adhesive layers 26a and 26b, the adhesive has a viscosity. Is 45
Since it is as low as about 00 cp, it penetrates inside the piezoelectric body 25,
The substantial thickness of the adhesive layers 26a and 26b is reduced, and the capacitance (C _a ) of the piezoelectric body 25 is equivalently reduced. The degree to which the capacitance (C _a ) decreases greatly varies depending on the piezoelectric body 25, and thus the capacitance (C _total ) between the detection units 23 varies, and as a result, the output voltage varies depending on the piezoelectric vibration sensor 21. Will occur.

In order to prevent the adhesive from penetrating into the piezoelectric body 25, the present inventor uses an adhesive having a high viscosity before curing as a material forming the adhesive layers 26a and 27b of the detecting portion 23. Have been found to be suitable.

The adhesive used as the material for forming the adhesive layers 26a and 26b of the present invention has a viscosity before curing of 5 × 10 5.
It is preferably ⁴ cp or more and 12 × 10 ⁴ cp or less.
If the viscosity before curing is less than 5 × 10 ⁴ cp, the piezoelectric body 2
When it is applied to both sides of No. 5, it easily penetrates into the piezoelectric body 25, the substantial thickness of the adhesive layers 26a and 26b is reduced, and the capacitance (C _a ) of the piezoelectric body 25 is equivalently reduced. The output voltage varies between the piezoelectric vibration sensors 21 using the piezoelectric body 25. The viscosity before curing is 12 × 10 ⁴
If it exceeds cp, the flow becomes too bad when applied to the piezoelectric body 25, and the adhesive layer 26a formed by curing this adhesive agent,
There is unevenness in the thickness of 26b.

The type of adhesive used as the material for forming the adhesive layers 26a and 26b is not particularly limited as long as it has conductivity. Also, the method for adjusting the viscosity is not particularly limited.

In the piezoelectric vibration sensor 21 of this example, the adhesive layers 26a and 26b of the detecting portion 23 have a viscosity of 5 × 1 before curing.
Since the adhesive is made of 0 ⁴ cp or more and 12 × 10 ⁴ cp or less, the adhesive for forming the adhesive layers 26a and 26b is used as the piezoelectric body 2 when the detection unit 23 is manufactured.
Even if it is applied to 5, the adhesive is suppressed from penetrating into the piezoelectric body 25, so that the capacitance (C _a ) of the piezoelectric body 25 is suppressed.
There hardly decreases, the capacitance of the piezoelectric body 25 (C _a) is substantially constant, the electrostatic capacitance between the detection unit ₂₃ (C _t otal)
Is extremely small, and as a result, the occurrence of variations in the output voltage due to the piezoelectric vibration sensor 21 is reduced. Therefore, it is possible to provide the piezoelectric vibration sensor 21 having a constant quality.

In the piezoelectric vibration sensor 21 of this example, the case where the piezoelectric body 25 is made of powder of an inorganic piezoelectric material which is porous has been described, but the piezoelectric body 25 does not become porous. It may be composed of a ferroelectric polymer such as vinylidene chloride.

[0017]

EXAMPLES Specific examples will be shown below. (Example 1) First, a piezoelectric body 2 made of lead zirconate titanate (PZT) in a square shape having a thickness of 0.5 mm and a side of 10 mm.
An epoxy adhesive having a viscosity before curing of 5 × 10 ⁴ cp was used as a material for forming the adhesive layers 26a and 26b on both sides of 5, and a square copper foil electrode 27a having a thickness of 30 μm and a side of 10 mm was used. 27b was attached and the sensor part 23 was produced. Then, the sensor portion 23 was fixed to the upper surface of the aluminum block pedestal 22 using an epoxy adhesive. Then, on the upper surface of the electrode 27a of the sensor unit 23, the mass 1
A square-shaped brass load body 24 having a thickness of 1.2 mm and a side of 10 mm was fixed using an epoxy adhesive to manufacture a piezoelectric vibration sensor. This was used as the piezoelectric vibration sensor of Example 1. The piezoelectric vibration sensor of the first embodiment is 50
The electrodes 27a and 27b of the detection unit 23 were connected to an impedance conversion circuit in order to individually produce the electric output from the piezoelectric body 25. Then, after attaching the piezoelectric vibration sensor of Example 1 in the vibrating machine, 80H _z,
The variation in output voltage when 1 G vibration was applied was examined.
The results are shown in Table 1 below.

Example 2 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 8 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as the piezoelectric vibration sensor of Example 2. The same number of piezoelectric type vibration sensors as in Example 2 were prepared and the variation in output voltage when vibration was applied was examined in the same manner as in Example 1. The results are shown in Table 1 below.
Shown in.

Example 3 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 10 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as the piezoelectric vibration sensor of Example 3. The same number of piezoelectric type vibration sensors as in Example 3 were prepared and the variation in output voltage when vibration was applied was examined in the same manner as in Example 1. The results are shown in Table 1 below.

Example 4 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 12 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as the piezoelectric vibration sensor of Example 4. The same number of piezoelectric vibration sensors as in Example 4 were prepared and the variation in output voltage when vibration was applied was examined in the same manner as in Example 1. The results are shown in Table 1 below.

Comparative Example 1 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 2 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as the piezoelectric vibration sensor of Comparative Example 1. The same number of piezoelectric vibration sensors as in Comparative Example 1 were prepared as in Example 1, and variations in output voltage when vibration was applied were examined in the same manner as in Example 1. The results are shown in Table 1 below.
Shown in.

Comparative Example 2 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 4 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as a piezoelectric vibration sensor of Comparative Example 2. The same number of piezoelectric type vibration sensors as in Comparative Example 2 were prepared as in Example 1, and variations in output voltage when vibration was applied were examined in the same manner as in Example 1. The results are shown in Table 1 below.
Shown in.

Comparative Example 3 A piezoelectric vibration sensor was prepared in the same manner as in Example 1 except that an epoxy adhesive having a viscosity before curing of 13 × 10 ⁴ cp was used as a material for the adhesive layers 26a and 26b. It was made. This was used as a piezoelectric vibration sensor of Comparative Example 3. The same number of piezoelectric vibration sensors as in Comparative Example 3 were prepared as in Example 1, and the variation in output voltage when vibration was applied was examined in the same manner as in Example 1. The results are shown in Table 1 below.

[0024]

[Table 1]

In Table 1, the value of the variation of the output is the ratio of the piezoelectric type vibration sensor which produced an output voltage other than ± 10% of the set output.

As is clear from the results shown in Table 1, the piezoelectric vibration sensor of the comparative example has a large variation.
On the other hand, in the piezoelectric vibration sensor of the embodiment, it can be seen that the variation in the output voltage between the piezoelectric vibration sensors is small and that the piezoelectric vibration sensor of a constant quality is obtained.

[0027]

As described above, in the piezoelectric vibration sensor of the present invention, the viscosity of the adhesive layer of the detecting portion before curing is 5 × 10 5.
^Since the adhesive is composed of ⁴ cp or more and 12 × 10 ⁴ cp or less, even if the adhesive for forming the adhesive layer is applied to the piezoelectric body at the time of producing the detection portion, There therefore is inhibited from penetrating into the piezoelectric body hardly decreases the capacitance of the piezoelectric body (C _a) is, the electrostatic capacitance of the piezoelectric body (C _a) is substantially constant, static between the detection unit Capacitance (C
The variation of _total ) is extremely small, and as a result, variation in output voltage due to the piezoelectric vibration sensor is reduced. Therefore, it is possible to provide a piezoelectric vibration sensor of constant quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional piezoelectric vibration sensor.

[Explanation of symbols]

21 ... Piezoelectric vibration sensor, 22 ... Pedestal, 23 ... Detection part, 24 ... Load body, 25 ... Piezoelectric body, 26a ... Adhesive layer, 26b ... Adhesive layer, 27a ... Electrode, 27b ... Electrode

Claims (2)

[Claims] 1. A piezoelectric vibration sensor comprising a pedestal, a detection section having electrodes provided on both sides of a piezoelectric body via an adhesive layer, and a load body further laminated on the pedestal. A piezoelectric vibration sensor, characterized by comprising an adhesive having a viscosity before curing of 5 × 10 ⁴ cp or more and 12 × 10 ⁴ cp or less. 2. The piezoelectric vibration sensor according to claim 1, wherein the piezoelectric body is porous.