JPH06213920A - Piezoelectric vibration sensor device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a piezoelectric vibration sensor device capable of reducing pyroelectric noise. A package includes a storage body and a storage cover that covers an upper opening of the storage body. The storage body and the storage cover are made of a conductive material, and the recess provided in the storage body has the above-mentioned structure. A piezoelectric vibration sensor is housed, the piezoelectric vibration sensor is attached to a signal processing circuit board provided with a small hole, the signal processing circuit board is supported by an opening peripheral portion of the housing, and the signal processing circuit board is also provided. It is characterized in that a storage cover for covering the storage is integrated with the storage. [Effect] It is possible to reduce pyroelectric noise and improve reliability of measured values.

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 device in which a piezoelectric vibration sensor is housed in a package, and in particular, it is possible to reduce noise due to the pyroelectric effect (hereinafter abbreviated as pyroelectric noise). Type vibration sensor device.

[0002]

2. Description of the Related Art Conventionally, various types of piezoelectric vibration sensors have been developed which are constructed by using a piezoelectric body. For example, the structure of the sensor includes a compression type, a stepped type, a beam type, a film type and the like. In addition, there are materials that use a ceramic material, a plastic material, or a mixture thereof as the material of the piezoelectric body. Then, in order to improve the mass productivity of such a piezoelectric vibration sensor, as a mass production method, an adhesive is applied to both surfaces of the piezoelectric body to fix each electrode, and depending on the intended use, the electrode and the piezoelectric body may be adhered. A piezoelectric vibration sensor excellent in mass productivity is being developed, such as after the support plate is unfastened and then cut into chips by a cutting means such as a dicing saw to mass-produce a large number of detection units. However, in the above-mentioned piezoelectric type sensor, pyroelectric noise is generally a serious problem. Pyroelectric noise is an output generated in the piezoelectric body when the temperature of the detecting portion changes abruptly. In general, pyroelectric noise contains a lot of low-frequency components, and thus becomes a particularly large barrier when measuring low-frequency vibrations. Therefore, conventionally, in order to reduce the pyroelectric noise, the following piezoelectric type vibration sensor device in which the piezoelectric type vibration sensor is housed in a hollow package has been proposed.

As an example of a conventional piezoelectric vibration sensor device,
There is one as shown in FIG. In the figure, reference numeral 1 is a piezoelectric vibration sensor, and the piezoelectric vibration sensor 1 is in the shape of a cylinder, and is composed of a pedestal 2, a detection unit 3, and a load body 4. The detection unit 3 is formed by sandwiching both sides of the film-shaped piezoelectric body 5 with electrodes (not shown), and further sandwiching both sides with the support plates 6 and fixing them. The piezoelectric vibration sensor 1 is housed and fixed in a hollow cylindrical hollow package 7 made of a material such as plastic.

The hollow package 7 is integrally provided with an annular sensor mounting portion 8 projecting inward of the hollow package 7 slightly below the center in the longitudinal direction thereof. A disc-shaped mounting portion 9 is integrally mounted on the base of the hollow package 7, and the mounting portion 9 fixes the piezoelectric vibration sensor device to the object to be measured.
Further, only the peripheral portion of the pedestal 2 of the piezoelectric vibration sensor 1 is mounted on the sensor mounting portion 8 of the hollow package 7 so as to be laid over and fixed by an appropriate fixing means such as screwing. As a result, the piezoelectric vibration sensor 1 is accommodated and fixed in the hollow package 7 in a floating state, and a space is formed on the lower surface side of the pedestal 2.

On the lower surface of the base 2 of the piezoelectric vibration sensor 1, a signal processing circuit board 17 having an electric circuit including an impedance conversion circuit and an amplification circuit for processing an electric output from the detection section 3 is mounted. Is attached. Further, on the surface of the signal processing circuit board 17 on which the electric circuit is mounted, a temperature assurance element (not shown) for mounting the electric output from the detection unit 3 is mounted. When the plug 13 connected to the connection cable 12 is inserted into the receptacle 11 of the connector attached to the lower portion of the hollow package 7, the piezoelectric vibration sensor 1 is supplied with power by the power supply lines 14 and 15, and the power supply line 14, The signal is output to the outside by 15.

In such a piezoelectric vibration sensor 1, the axis perpendicular to the film-shaped piezoelectric body 5 and passing through the center of the load body 4 is the vibration sensing axis G. In such a piezoelectric sensor 1, by attaching the mounting portion 9 of the hollow package 7 to the object to be measured, it is possible to detect a vibration change in the direction of the sensing axis G of the object to be measured.

[0007]

[Problems to be Solved by the Invention]

However, PZT is added to the piezoelectric body of the above device.
When a material having extremely high piezoelectricity such as (lead zirconate titanate) was used, the erasing of pyroelectric noise was insufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric vibration sensor device capable of sufficiently reducing pyroelectric noise while preventing resonance.

[0010]

According to a first aspect of the present invention, there is provided a piezoelectric vibration sensor device in which, in order to solve the above-mentioned problems, a detection unit having electrodes fixed via adhesive layers provided on both surfaces of a piezoelectric body. In the piezoelectric vibration sensor device, wherein a piezoelectric vibration sensor having a load body attached thereto and a signal processing circuit board fixed to a detection portion of the piezoelectric vibration sensor are housed in a package, The package includes a storage body and a storage cover that covers the upper opening of the storage body,
The storage body and the storage cover are made of a conductive material,
The piezoelectric vibration sensor is housed in a recess provided in the housing, and the piezoelectric vibration sensor is attached to a signal processing circuit board having a small hole, and the signal processing circuit board is an opening of the housing. A storage cover that is supported at the peripheral edge and covers the signal processing circuit board is integrated with the storage body.

[0011]

In the piezoelectric vibration sensor device of the present invention having the above structure, the piezoelectric vibration sensor is housed in the recess of the housing made of a conductive material, and the piezoelectric vibration sensor is provided with a signal processing circuit having a small hole. The signal processing circuit board is attached to a substrate, and the signal processing circuit board is supported by the peripheral edge of the opening of the housing to make the recess of the housing almost sealed, and the housing cover and the housing for covering the signal processing circuit board are provided. By being integrated, even if the temperature around the device changes suddenly, the temperature change of the detection unit can be reduced, and the pyroelectric noise can be reduced. In addition, as described above, since the signal processing circuit board supported on the peripheral edge of the opening of the housing recess has small holes, the small holes act as air vent holes, and It is possible to avoid fluctuations in the internal pressure in the recess without being in a sealed state, to completely avoid erroneous measurements such as addition of sensor outputs due to the fluctuations in internal pressure, and to improve the reliability of measured values. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the piezoelectric vibration sensor device according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the piezoelectric vibration sensor device according to the present embodiment has piezoelectric recesses 22 formed in the housing 21a of a conductive package 21 including a housing 21a and a housing cover 21b. A sensor 23 is housed, and a signal processing circuit board 25 having a small hole 25a is further attached to the piezoelectric vibration sensor 23 and supported at an opening peripheral edge portion 24 of the housing 21a. Further, a storage cover 21 that covers the signal processing circuit board 25.
b is fitted at the upper opening of the housing 21a. The small hole 25a on the signal circuit board 25 is
The position and size of the small holes 25a are not limited as long as the rigidity of the signal processing circuit board 25 is not reduced. The storage cover 21b may be made of plastic or metal whose material is selected as long as its volume resistivity is 5 Ω · cm or less.

Further, a cable outlet 27 is provided on the upper portion of the housing cover 21b, a connector is attached to the cable outlet 27, and a power supply line 29 is drawn from a receptacle 28 of the connector.・
Is connected to the signal processing circuit board 25. Therefore, by inserting the plug 31 to which the connection cable 30 is connected to the receptacle 28, the piezoelectric vibration sensor 23 having the above-described configuration is supplied with power by the power supply lines 29, ... A signal is output to the outside by 29 ... In addition, in the present embodiment, the outlet 27 of the cable is the storage cover 21b.
However, it is not limited to the upper portion of the storage cover 21b, but may be provided on the side portion or the like depending on the intended use without affecting other functions.

In the piezoelectric vibration sensor 23, electrodes (not shown) are fixed on both surfaces of the piezoelectric body 32 via adhesive layers (not shown), and a support plate is formed on both surfaces of the electrodes via adhesive layers. And a load member 36 laminated on the detection unit 35.
The piezoelectric vibration sensor 23 is fixed by a signal processing circuit board 25 attached to the surface opposite to the load body 36 provided in the detection unit 35. On the surface of the signal circuit board 25 on which the electric circuit is mounted, there is provided a temperature compensating element 37 for ensuring the temperature of the output from the detecting section 35. Depending on the intended use, the piezoelectric vibration sensor 23 may not be provided with support plates on both the front and back surfaces of the detection unit 35 having the above-mentioned configuration.

A piezoelectric vibration sensor device 2 having the above structure.
In 0, the axis orthogonal to the surface where the electrode of the piezoelectric body 32 is formed and passing through the center of the load body 36 is the vibration sensing axis G ′. Therefore, in the piezoelectric vibration sensor device 20 as described above, by mounting the measured object on the bottom portion 38 of the housing body 21a of the package 21, it is possible to measure the vibration change of the measured object in the sensing axis G'direction. . Further, when the object to be measured is attached to the upper surface 39 of the storage cover body, it is necessary to provide the cable outlet 27 in a place other than the upper surface of the storage cover body 21b.

As described above, in the piezoelectric vibration sensor device 20 of this embodiment, the piezoelectric vibration sensor 23 is housed in the recess 21 of the housing 21a made of a conductive material, and the piezoelectric vibration sensor 23 is made into a small hole. 25a is attached to the signal processing circuit board 25, and the signal processing circuit board 25 is supported by the opening peripheral edge portion 24 of the housing body 21a to make the recess 21 of the housing body 21a almost sealed, and By integrating the housing cover 21b that covers the signal processing circuit board 25 and the housing body 21a, even if the temperature around the apparatus changes suddenly, the temperature change of the detection unit 35 can be reduced. It is possible to reduce electric noise.
Further, as described above, since the signal processing circuit board 25 supported by the opening peripheral portion 24 of the recess 21 of the housing 21a is provided with the small hole 25a, the small hole 25a functions as an air vent hole. The recess 21 of the storage body 21a.
Is not hermetically closed, and fluctuations in the internal pressure in the recess 21 can be avoided, erroneous measurements such as addition of sensor outputs due to the fluctuations in internal pressure can be completely avoided, and the reliability of measured values can be improved.

In addition, the piezoelectric vibration sensor device 20 of the present embodiment having the above-described structure has a lower center of gravity than the conventional piezoelectric vibration sensor device 10 shown in FIG. It is possible to improve and reduce crosstalk.

Therefore, an example of manufacturing the piezoelectric vibration sensor device of the present embodiment having the above-mentioned structure will be described below. (Production Example) In this production example, 5 mm square, 0.5 mm
Piezoelectric plate 3 made of thick PZT (lead zirconate titanate)
Adhesive made of epoxy resin is applied to both sides of 2,
A copper foil of the same size as the piezoelectric plate 32 and having a thickness of 30 μm is provided through this, and an adhesive made of epoxy resin is applied to the surfaces of both electrodes using the copper foil as an electrode. The detection plates 35 of the piezoelectric vibration sensor 23 are configured by adhering the support plates 33 and 34 made of a 15 mm square glass epoxy plate.

An adhesive made of the same material as the above-mentioned adhesive is applied to both surfaces of the detection unit 35, and one surface of the detection unit 35 is adjusted so that the detection unit 35 is located at the center.
A signal processing circuit board 25 made of a ceramic board having a thickness of 8 mm and a size of 15 mm is fixed. Then, the impedance conversion circuit and the electrodes are connected to the surface of the signal processing circuit board opposite to the surface on which the detection unit 35 is attached. Further, a brass load body 36 having a weight of 1 g is attached to the other surface of the detection portion 35. And
The piezoelectric vibration sensor 23 including the detection unit 35 and the load body 36 having the above-described configuration includes the recess 22 of the stainless steel housing 21a having an outer diameter of 25 mm and a height of 10 mm and having a recess 22 having an outer diameter of 8 mm and a depth of 8 mm. The signal processing circuit board 25, which is fixed in the housing 2 and fixes the detection unit 35,
It is installed so as to be supported by the opening peripheral portion 24 of 1a. Then, a storage cover 21b made of stainless steel is provided so as to cover the signal processing board 25, and the storage cover 21b is fitted and integrated with the upper opening of the storage 21a.

The upper portion of the storage cover 21b is
A cable outlet 27 is provided, a connector is attached to the cable outlet 27, and a power supply line 29 ... Pulled out from a receptacle 28 of the connector.
Is connected to the signal processing circuit board 25. Therefore, by inserting the plug 31 to which the connection cable 30 is connected to the receptacle 28, the piezoelectric vibration sensor 23 having the above-described configuration is supplied with power by the power supply line 29. The signal is output to the outside by.

A piezoelectric vibration sensor device 2 having the above structure
In 0, the axis perpendicular to the surface of the piezoelectric body 32 on which the electrodes are provided and passing through the center of the load body 36 is the vibration sensing axis G ′. Therefore, in the piezoelectric vibration sensor device 20 of the above-described manufacturing example, the vibration change of the measured object can be detected by attaching the measured object to the bottom portion 38 of the housing 21a.

The piezoelectric vibration sensor device 20 of the above-described manufacturing example and the small hole 25a in the circuit processing board 25 of the above-described manufacturing example.
Without providing, the output was compared and measured using the piezoelectric vibration sensor device of the comparative example which is the same as the above-described manufacturing example under the other conditions. (Test Example) Small hole 25a of the circuit processing board 25 of the above-described manufacturing example
The size was 0.5 mm. Then, the piezoelectric type vibration sensor device of the above-mentioned manufacturing example and comparative example is mounted on a hot plate at 80 ° C.
The output of the piezoelectric vibration sensor device of the above-mentioned manufacturing example and comparative example after being placed on a cold plate at 10 ° C. after being placed for 0 second was measured. The results are shown in Table 1. The output values shown in Table 1 are values obtained by dividing the peak value of the output observed in the heating / cooling process by the sensitivity.

[0023]

[Table 1]

As shown in Table 1, the piezoelectric vibration sensor device of the comparative example has a configuration in which the signal processing circuit board of the piezoelectric vibration sensor device is not provided with the small hole penetrating the recess of the housing and the hollow part of the housing. The output value is larger than that in the manufacturing example in which the small hole 25a is provided. In the case of the comparative example, this is due to the signal processing circuit board 25,
Since the piezoelectric vibration sensor 23 housed in the concave portion 21 of a is sealed, the fluctuation of the internal pressure of the concave portion is detected by the piezoelectric vibration sensor 23 in addition to the pyroelectric output, and this is added to the measurement output. is there. Therefore, the device of this manufacturing example is
In addition to the reduction of pyroelectric noise described above, unnecessary output generated during heating / cooling can be avoided.

In the piezoelectric vibration sensor device of the above-described manufacturing example, the conductive layer 26 having the opening 26a which is electrically connected to the small hole 25a of the signal processing circuit board 25 is provided on the signal processing circuit board 25. Also in the piezoelectric vibration sensor device 30 of the applied example as shown in FIG. 2, as a result of performing the same test as the above-mentioned test example, the same effect as that of the above-mentioned manufacture example could be obtained. In addition, in the case of the piezoelectric vibration sensor device 30 having the configuration as shown in FIG. 2, in addition to the effect of reducing pyroelectric noise and the effect of avoiding unnecessary output during heating / cooling, as in the above-described manufacturing example. In addition, the detection unit 35 of the vibration sensor 23 includes a housing cover 21b made of a conductive layer 26 provided on the signal processing circuit board 25 and a conductive material.
Is equivalently double shielded, so S / N
The ratio can be improved and the noise resistance can be significantly improved.

[0026]

As described above, in the piezoelectric vibration sensor device of this embodiment, the piezoelectric vibration sensor is housed in the recess of the housing made of a conductive material, and the piezoelectric vibration sensor is provided with a small hole. The signal processing circuit board is attached to the signal processing circuit board, and the signal processing circuit board is supported by the peripheral edge portion of the opening of the housing to make the recess of the housing almost sealed, and the housing cover that covers the signal processing circuit board. By integrating the above and the storage body, even if the temperature around the apparatus changes suddenly, the temperature change of the detection unit can be reduced, and the pyroelectric noise can be reduced. . Also,
As described above, since the signal processing circuit board supported on the peripheral edge of the opening of the housing recess has the small holes, the small holes act as air vent holes, and the housing recess is in a closed state. It is possible to avoid fluctuation of internal pressure in the recess,
It is possible to completely avoid erroneous measurement such as addition of the sensor output due to the internal pressure fluctuation, and it is possible to improve the reliability of the measured value.

Further, the piezoelectric vibration sensor device of the present embodiment having the above-mentioned structure has a lower center of gravity as compared with the conventional piezoelectric vibration sensor device, so that impact resistance is improved and crosstalk is reduced. Can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a piezoelectric vibration sensor device according to a manufacturing example of the present embodiment.

FIG. 2 is a schematic configuration diagram of a piezoelectric vibration sensor device according to an application example of the present embodiment.

FIG. 3 is a schematic configuration diagram showing a conventional piezoelectric vibration sensor device.

[Explanation of symbols]

1, 23 ... Piezoelectric vibration sensor 2 ... Pedestal 3, 35 ... Detecting unit 4 ... Load body 5 ... Membrane piezoelectric body 6, 33, 34 ... Support plate 7, 21 ...
Package 10, 20, 30 ... Piezoelectric vibration sensor device 21a ... Storage body 21b ... Storage cover body 22 ... Recessed portion 24
... Opening peripheral edge portions 17 and 25 ... Signal processing circuit board 25a
... Small hole 26 ... Conductive layer 26a ... Opening 32 ... Piezoelectric body G, G '... Sensing axis

Claims (1)

[Claims] 1. A piezoelectric type vibration sensor in which a load body is attached to a detection section to which electrodes are fixed via adhesive layers provided on both sides of a piezoelectric body, and to the detection section of the piezoelectric type vibration sensor. In a piezoelectric vibration sensor device in which the signal processing circuit board thus formed is housed in a package, the package includes a housing and a housing cover that covers an upper opening of the housing. The cover is made of a conductive material, the piezoelectric vibration sensor is housed in the recess provided in the housing, the piezoelectric vibration sensor is attached to the signal processing circuit board provided with a small hole, A piezoelectric vibration sensor device, wherein the signal processing circuit board is supported by an opening peripheral portion of the housing, and a housing cover that covers the signal processing circuit board is integrated with the housing.