JPH07202283A - Piezoelectric sensor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a piezoelectric sensor which can surely detect acceleration or impact by a simple structure. CONSTITUTION:A base member 1 has a recessed part 11 and an element attaching part 12. The recessed part 11 is provided on one surface of the base member 1. Providing W in a width direction and L in a length direction on the one surface, the element attaching part 12 is provided to at least one end side of the length direction of the recessed part 11. At least one end part of a piezoelectric element 2 is fixed to the element attaching part 12 and is arranged on the recessed part 11 along the length direction L having an interval between the recessed part 11 and a bottom surface 111.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric sensor and its manufacturing method.

[0002]

2. Description of the Related Art Piezoelectric sensors of this kind are used for detecting acceleration and shock in, for example, hard disk drive devices, airbag systems, electronically controlled suspension systems and the like. As prior art documents, Japanese Patent Laid-Open Nos. 64-72012 and 2-93370 are known. Along with a high degree of reliability, it is extremely important that the number of parts is small and the size is small. As prior art documents, Japanese Patent Laid-Open Nos. 64-72012 and 2-93370 are known.

[0003]

Since this type of piezoelectric sensor is used in the above-mentioned applications, it is extremely important that it is small in size, excellent in impact resistance, and highly reliable.
However, the conventional piezoelectric sensor is disclosed in, for example, Japanese Patent Laid-Open No. 2-93.
As disclosed in Japanese Unexamined Patent Publication No. 370, etc., it has a complicated assembly structure and a large number of parts, and thus does not always satisfy the above-mentioned requirements.

An object of the present invention is to provide a piezoelectric sensor having a simple structure and capable of reliably detecting acceleration or impact.

Another object of the present invention is to provide a piezoelectric sensor which can be firmly and stably attached to a circuit board or other external device by surface mounting.

Still another object of the present invention is to provide a piezoelectric sensor having improved impact resistance.

Still another object of the present invention is to provide a miniaturized piezoelectric sensor.

Still another object of the present invention is to provide a piezoelectric sensor which can easily realize a robust structure excellent in impact resistance.

Still another object of the present invention is to provide a piezoelectric sensor capable of canceling noise caused by temperature and the like.

Still another object of the present invention is to provide a piezoelectric sensor which can easily, surely perform mounting, positioning and fixing of a piezoelectric element.

Still another object of the present invention is to provide a piezoelectric sensor capable of sensing both vertical acceleration and horizontal acceleration.

Still another object of the present invention is effective as means for facilitating manufacturing and assembling.

Yet another object of the present invention is to provide a method for manufacturing a piezoelectric sensor simply and reliably.

Still another object of the present invention is to provide a method for manufacturing a piezoelectric sensor while avoiding a short circuit between electrodes of a piezoelectric element.

[0015]

To solve the above problems, a piezoelectric sensor according to the present invention includes a base member and a piezoelectric element, and the base member has a recess and an element mounting portion. The recess is provided on one surface of the base member, and the element mounting portion has at least one end side in the length direction of the recess when the width direction and the length direction are imaginary on the one surface. The piezoelectric element has at least one end fixed to the element mounting portion, is arranged on the recess along the length direction, and has a space from the bottom surface of the recess.

In a preferred embodiment, the base member is
The piezoelectric element has at least two terminal conductors, the first terminal conductor is provided on one end side in the length direction of the base member, and the second terminal conductor is provided on the other end side in the length direction. May be electrically connected to the terminal conductor.

In such a structure, the lead conductor of the first terminal conductor is guided to one side of the element attachment portion, and the lead conductor of the second terminal conductor is attached to the element attachment portion. It is preferable that the electrodes of the piezoelectric element are connected to and fixed to each of the lead conductors.

More preferably, the concave portion is provided so as to be biased on either side in the width direction so that a narrow width region is formed on one side in the width direction of the base member and a wide width region is formed on the other side. The lead conductor of the second terminal conductor extends from the other end side in the length direction to the one end side in the length direction through the wide region, and the piezoelectric element has its electrode. Are connected and fixed to each of the lead conductors.

The piezoelectric element is preferably a bimorph piezoelectric body. A desirable structure for supporting the piezoelectric element is that the element mounting portion is composed of a concave groove, and the concave groove has a bottom surface slightly higher than the bottom surface of the recess and lower than the one surface of the base member. The piezoelectric element has a structure in which electrodes are provided on both sides in the thickness direction, and one end portion is arranged and fixed in the groove so that the thickness direction coincides with the width direction. is there. Further, as another example, the piezoelectric element may be inclined in the width direction of the base member.

As yet another example, it is also effective that the recess has a wide portion on the other end side in the length direction.

The manufacturing method according to the present invention, which is suitable for manufacturing the piezoelectric sensor, has a thickness in the recess of the base member in consideration of the distance between the piezoelectric element and the bottom surface of the recess. After arranging the film-like spacing regulating member, the piezoelectric element is incorporated into the base member, and then the spacing regulating member is removed.

More preferably, in the step of incorporating the piezoelectric element into the base member, after fixing the piezoelectric element to the base member with an insulating adhesive, the electrode of the piezoelectric element is attached with a conductive adhesive. Is connected to the lead conductor.

[0023]

A piezoelectric sensor according to the present invention includes a base member and a piezoelectric element, the base member has a recess and an element mounting portion, and the recess is provided on one surface of the base member. The element mounting portion is provided on at least one end side in the length direction of the recess when the width direction and the length direction are hypothesized on one surface, and at least one end portion of the piezoelectric element is fixed to the element mounting portion. , Located on the recess along the length and has a gap between the bottom of the recess,
When subjected to acceleration or impact, the piezoelectric element responds to the recess without any interference from the base member, and the acceleration or impact applied by the response is detected. Since the piezoelectric sensor according to the present invention only needs to have a piezoelectric element and a base member supporting the piezoelectric element as basic elements, a piezoelectric sensor that can reliably detect acceleration or impact can be obtained with a simple structure.

The base member has at least two terminal conductors, the first terminal conductor is provided at one end side in the length direction of the base member, and the second terminal conductor is provided at the other end side in the length direction. In the embodiment in which the piezoelectric element is electrically connected to the terminal conductor, when mounting on a circuit board or other external device, the first terminal conductor and the second terminal conductor at both ends in the length direction are used to It can be mounted and a strong and stable mounting structure can be realized.

The lead conductor of the first terminal conductor is guided to one side of the element mounting portion, the lead conductor of the second terminal conductor is guided to the other side of the element mounting portion, and the electrode of the piezoelectric element is In the structure in which the piezoelectric element is connected and fixed to each of the lead conductors, the piezoelectric element can be surely connected and fixed to the base member via the lead conductors arranged on both sides. Therefore, impact resistance is improved.

Furthermore, the recess has a narrow region on one side in the width direction of the base member and a wide region on the other side.
The lead conductor of the second terminal conductor is provided so as to be biased to one of both sides in the width direction, and extends from the other end side in the length direction to the one end side in the length direction through the wide width region. In the structure in which the electrode of is connected and fixed to each of the lead conductors, without increasing the plane area of the first base member,
Alternatively, the area necessary for forming the lead conductor of the second terminal conductor can be secured and the lead conductor having a sufficient width can be formed while reducing the size. Therefore, the base member can be downsized. The miniaturization of the base member directly contributes to miniaturization of the whole.

When the piezoelectric element is made of a piezoelectric material, a robust structure having excellent impact resistance can be easily realized. When a bimorph piezoelectric body is used, noise caused by temperature or the like can be canceled by selecting the polarization directions of the two piezoelectric bodies.

In the case where the piezoelectric element is made of a piezoelectric material, the element mounting portion is composed of a concave groove, and the concave groove has a bottom surface slightly higher than the bottom surface of the recess and lower than the one surface of the base member. , The piezoelectric body has electrodes on both sides in the thickness direction, one end is arranged in the groove so that the thickness direction matches the width direction, and when the structure is fixed, Just place the piezoelectric element in the element mounting part,
A step between the bottom surface of the element mounting portion and the bottom surface of the concave portion is used to secure a necessary space between the piezoelectric element and the bottom surface of the concave portion, and the bottom surface of the element mounting portion and one surface of the base member. The piezoelectric element can be positioned or fixed by utilizing the level difference. Therefore, the mounting, positioning and fixing of the piezoelectric element on the base member can be performed easily and reliably.

Furthermore, when the piezoelectric body is attached to the base member while being inclined in the width direction, a piezoelectric sensor capable of sensing both acceleration acting vertically to the bottom surface of the base member and acceleration acting horizontally is provided. can get.

The structure in which the concave portion has a wide portion on the other end side in the length direction is effective as a means for facilitating the manufacturing and assembling.

In manufacturing the above-mentioned piezoelectric sensor,
The manufacturing method according to the present invention, in the recess of the base member, after arranging the film-shaped spacing regulating member having a thickness in consideration of the distance between the piezoelectric element and the bottom surface of the recess, the piezoelectric element is incorporated into the base member, Next, the interval regulating member is pulled out. As a result, the piezoelectric sensor according to the present invention can be manufactured easily and reliably.

The step of incorporating the piezoelectric element into the base member is
When the step of connecting the electrodes of the piezoelectric element to the lead conductor using the conductive adhesive after fixing the piezoelectric element to the base member with the insulating adhesive is used, the flow of the conductive adhesive is Is cut off at the part. Therefore, a short circuit between electrodes can be avoided.

[0033]

FIG. 1 is a perspective view of a piezoelectric sensor according to the present invention, FIG. 2 is a plan view of the piezoelectric sensor shown in FIG. 1 with a lid removed, and FIG. 3 is a sectional view taken along line A3-A3 of FIG. 4 is a sectional view taken along line A4-A4 in FIG. 2, and FIG. 5 is a sectional view taken along line A5-A5 in FIG. The piezoelectric sensor according to the present invention includes a base member 1 and a piezoelectric element 2. Reference numeral 3 is a lid.

The base member 1 has a concave portion 11 and an element mounting portion 12. The concave portion 11 is provided on one surface of the base member 1, and the element mounting portion 12 is formed on the one surface in the width direction W. When the length direction L is assumed, the recess 11 is provided at least on one end side in the length direction L. At least one end of the piezoelectric element 2 is fixed to the element mounting portion 12 and is arranged on the recess 11 along the length direction L.
There is a gap g between the first and the bottom surface 111.

With this structure, when an acceleration or a shock is applied, the piezoelectric element 2 responds to the recess 11 without any interference from the base member 1, and the acceleration or the shock applied by the response is generated. Detected. As described above, since the piezoelectric element 2 and the base member 1 supporting the piezoelectric element 2 may be provided as the basic elements, a piezoelectric sensor capable of reliably detecting acceleration or impact can be obtained with a simple structure.

The base member 1 has at least two terminal conductors 13 and 14. The first terminal conductor 13 is provided on one end side in the length direction L of the base member 1, and the second terminal conductor 1
4 is provided on the other end side in the length direction L. Piezoelectric element 2
Is electrically connected to the terminal conductors 13 and 14. With such a structure, when mounting on a circuit board or other external device, it is surface-mounted using the first terminal conductor 13 and the second terminal conductor 14 at both ends in the length direction L, and is strong and stable. The mounting structure can be realized.

Moreover, in the first terminal conductor 13, the lead conductor 131 is guided to one side of the element mounting portion 12,
The lead conductor 141 of the second terminal conductor 14 is guided to the other side of the element mounting portion 12. Piezoelectric element 2 has its electrode 2
1 and 21 are connected and fixed to the lead conductors 131 and 141, respectively. With such a structure, the piezoelectric element 2
Can be reliably connected and fixed to the base member 1 via the lead conductors 131 and 141 arranged on both sides. Therefore, impact resistance is improved.

Further, the recess 11 is formed in the width direction W of the base member 1.
A narrow region 15 is formed on one side and a wide region 16 is formed on the other side.
Is provided so as to be biased to either one of both sides in the width direction W. Lead conductor 141 of second terminal conductor 14
Extends from the other end in the length direction L to the one end in the length direction L through the wide region 16. The piezoelectric element 2 has its electrode 2
1 and 21 are connected and fixed to the lead conductors 131 and 141, respectively. Electrodes 21, 22 and lead conductor 131,
141 is a bonding agent 41, 4 such as a conductive adhesive or solder.
It is joined by two.

With this structure, the area required for forming the lead conductor 141 of the second terminal conductor 14 is secured without increasing the plane area of the base member 1 or reducing the plane area, and the base member 1 has a sufficient width. The lead conductor 141 can be formed. Therefore, the base member 1 can be downsized. The miniaturization of the base member 1 directly contributes to miniaturization of the whole.

The advantage of using the piezoelectric element 2 as a detecting element is that a robust structure having excellent impact resistance can be easily realized. A preferable example of the piezoelectric element 2 is a bimorph piezoelectric body. The figure shows a bimorph piezoelectric body, which has a pair of piezoelectric elements 20, 20. A pair of piezoelectric elements 20,
The piezoelectric element 20 has electrodes 21 and 22 on both surfaces thereof. The electrode 22 of one piezoelectric element 20 and the other piezoelectric element 2 are provided.
The zero electrode 22 is superposed and joined so as to make surface contact with each other. The pair of piezoelectric elements 20, 20 are
In order to cancel noise due to temperature fluctuations, the polarization directions are overlapped with each other. In another example, the pair of piezoelectric elements 20 and 20 may be coupled so as to have the same polarization direction. In this case, the commonly connected electrodes are connected to ground, for example. A configuration is also often adopted in which a diaphragm made of a metal elastic plate having conductivity is interposed between commonly connected electrodes and the diaphragm is connected to the ground. Piezoelectric sensors using a bimorph piezoelectric material are known from Japanese Patent Laid-Open Nos. 64-72012 and 2-93370.

Element mounting portion 1 for mounting the piezoelectric element 2
2 is preferably a groove. The element mounting portion 12 formed of a groove is offset so that its bottom surface is slightly higher than the bottom surface 111 of the recess 11 and lower than one surface of the base member 1. The width of the element mounting portion 12 is set to a dimension corresponding to the width of the piezoelectric element 2. With the above structure, the piezoelectric element 2 is simply arranged on the element mounting portion 12 so that the bottom surface of the element mounting portion 12 and the bottom surface 11 of the recess 11 are formed.
The gap between the piezoelectric element 2 and the bottom surface 111 of the recess 11 is ensured by utilizing the step between the element attachment portion 12 and the one surface of the base member 1. The piezoelectric element 2 can be positioned or fixed by utilizing it.
Therefore, the piezoelectric element 2 can be attached, positioned and fixed to the base member 1 easily and reliably.

It is also effective to mount the piezoelectric element 2 at an angle in the width direction W of the base member 1. In this case, it is possible to obtain a piezoelectric sensor capable of sensing both the acceleration acting vertically to the bottom surface of the base member 1 and the acceleration acting horizontally. It is desirable that the piezoelectric element 2 and the element mounting portion 12 are bonded to each other using, for example, an insulating adhesive 5.
By doing so, impact resistance can be further improved.

Also, in the preferred embodiment, the recess 11 is
A wide portion 112 is provided on the other end side in the length direction L. The wide portion 112 is effective as a means for facilitating manufacturing and assembling, as described below.

The base member 1 is made of electrically insulating ceramic or plastic. Ceramic materials that can be used include alumina, forsterite, steatite and the like. When using a plastic material,
It is desirable to use a material having high heat resistance.

First terminal conductor 13 and second terminal conductor 14
Is formed by printing, sputtering, vapor deposition, or a combination of these with plating. The first terminal conductor 13 and the second terminal conductor 14 are formed so as to reach from the one surface side of the base member 1 to the one surface side through the side surface, the back surface, and the other side surface.

The lid 3 has a piezoelectric element 2 on one surface side of the base member 1.
And the contact end surface is bonded to the base member 1 by adhesion or other means. It is desirable to seal the periphery of the joint surface with resin.

Next, a method of manufacturing the above-described piezoelectric sensor will be described with reference to FIGS.

First, as shown in FIGS. 6 and 7, the piezoelectric element and the bottom surface 11 of the recess 11 are provided in the recess 11 of the base member 1.
The film-shaped gap regulating member 6 having a thickness in consideration of the gap g between the film gap 1 and the gap 1 is arranged. The space regulating member 6 has a recess 11
Are arranged so as to cross in the width direction W. Interval restriction member 6
Is a wide portion 11 provided on the other end side in the length direction L.
It is desirable to arrange it at 2. In this step, the insulating adhesive 5 is applied to the element mounting portion 12 in advance.

Next, as shown in FIGS. 8 and 9, the piezoelectric element 2 is incorporated into the base member 1. At this time, the piezoelectric element 2
Since the lower surface of the above is received by the distance regulating member 6, a distance according to the thickness of the distance regulating member 6 is formed between the piezoelectric element 2 and the bottom surface 111 of the recess 11. The piezoelectric element 2 is fixed to the base member 1 by the insulating adhesive 5 applied to the element mounting portion 12. After this, the interval regulating member 6 is pulled out in the direction of arrow a. Since the interval regulating member 6 is arranged in the wide portion 112 provided on the other end side in the length direction L, it can be easily removed. As a result, a gap g required for operation is formed between the piezoelectric element 2 and the bottom surface 111 of the recess 11.

Next, as shown in FIGS. 10 and 11, the electrodes 2 of the piezoelectric element 2 are formed by using the conductive adhesives 41 and 42.
1, 22 are joined to the lead conductors 131, 142. Since the element mounting portion 12 is provided between the lead conductors 131 and 141, and the insulating adhesive 5 that fixes the piezoelectric element 2 is provided inside the element mounting portion 12, the conductive adhesives 41 and 42 are provided.
Is blocked by the insulating adhesive 5. For this reason,
A short circuit between electrodes can be avoided.

After that, the cover 3 (see FIG. 1) is covered on one surface of the base member 1 and bonded, and the periphery of the bonded surface is sealed with resin to complete the process.

[0052]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a piezoelectric sensor that can reliably detect acceleration or impact with a simple structure. (B) It is possible to provide a piezoelectric sensor that can be firmly and stably attached to a circuit board or other external device by surface mounting. (C) It is possible to provide a piezoelectric sensor having improved impact resistance. (D) It is possible to provide a miniaturized piezoelectric sensor. (E) It is possible to provide a piezoelectric sensor that can easily realize a robust structure having excellent impact resistance. (F) It is possible to provide a piezoelectric sensor that can cancel noise caused by temperature and the like. (G) Easy mounting, positioning and fixing of piezoelectric element,
In addition, it is possible to provide a piezoelectric sensor that can be reliably executed. (H) It is possible to provide a piezoelectric sensor capable of sensing both vertical acceleration and horizontal acceleration. (I) It is possible to provide a piezoelectric sensor that can be easily manufactured and assembled. (J) It is possible to provide a method for easily and reliably manufacturing a piezoelectric sensor. (K) It is possible to provide a method of manufacturing a piezoelectric sensor by avoiding a short circuit between electrodes of a piezoelectric element.

[Brief description of drawings]

FIG. 1 is an external perspective view of a piezoelectric sensor according to the present invention.

FIG. 2 is a plan view of the piezoelectric sensor shown in FIG. 1 with a lid removed.

3 is a cross-sectional view taken along the line A3-A3 of FIG.

FIG. 4 is a cross-sectional view taken along the line A4-A4 of FIG.

5 is a cross-sectional view taken along the line A5-A5 of FIG.

FIG. 6 is a diagram showing a manufacturing process of the piezoelectric sensor according to the present invention.

7 is a cross-sectional view taken along the line A7-A7 in FIG.

FIG. 8 is a diagram showing a manufacturing process of the piezoelectric sensor according to the present invention.

9 is a cross-sectional view taken along the line A9-A9 in FIG.

FIG. 10 is a diagram showing a manufacturing process of the piezoelectric sensor according to the present invention.

11 is a cross-sectional view taken along the line A11-A11 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case member 2 Piezoelectric element 11 Recessed portion 12 Element mounting portion 13 First terminal electrode 14 Second terminal electrode 131 Lead electrode 141 Lead electrode

Claims (9)

[Claims] 1. A piezoelectric sensor including a base member and a piezoelectric element, wherein the base member has a recess and an element mounting portion, and the recess is provided on one surface of the base member. The element mounting portion is provided on at least one end side in the length direction of the recess when the width direction and the length direction are assumed on the one surface, and the piezoelectric element has at least one end portion. A piezoelectric sensor that is fixed to an element mounting portion, is arranged on a recess along the length direction, and has a space between the recess and the bottom surface of the recess. 2. The base member has at least two terminal conductors, the first terminal conductor is provided on one end side in the length direction of the base member, and the second terminal conductor is the other end in the length direction. 2. The piezoelectric element is provided on a side, and the piezoelectric element is electrically connected to the terminal conductor.
Piezoelectric sensor described in 3. The lead conductor of the first terminal conductor is guided to one side of the element attachment portion, and the lead conductor of the second terminal conductor is attached to the other side portion of the element attachment portion. 3. The piezoelectric sensor according to claim 2, wherein the piezoelectric element has its electrodes connected and fixed to each of the lead conductors. 4. The recess is provided so as to be biased to one of both sides in the width direction so that a narrow region is formed on one side in the width direction of the base member and a wide region is formed on the other side of the base member. The lead conductor of the second terminal conductor extends from the other end side in the length direction to the one end side in the length direction through the wide region, and the piezoelectric element has the electrode The piezoelectric sensor according to claim 3, which is connected and fixed to each of the lead conductors. 5. The element mounting portion is formed of a concave groove, the concave groove being slightly higher than the bottom surface of the concave portion, and
It has a bottom surface lower than the one surface of the base member, the piezoelectric element has electrodes on both surfaces in the thickness direction, and one end portion is the concave groove so that the thickness direction matches the width direction. The piezoelectric sensor according to claim 1, wherein the piezoelectric sensor is disposed inside and fixed. 6. The piezoelectric sensor according to claim 1, wherein the piezoelectric element is inclined in the width direction of the base member. 7. The piezoelectric sensor according to claim 1, wherein the recess has a wide portion on the other end side in the length direction. 8. A method for manufacturing the piezoelectric sensor according to claim 1, wherein the space between the piezoelectric element and the bottom surface of the recess is provided in the recess of the base member. A method for manufacturing a piezoelectric sensor, comprising: disposing a film-shaped space regulating member having a thickness considered, incorporating the piezoelectric element in the base member, and then removing the space regulating member. 9. The step of incorporating the piezoelectric element in the base member, wherein the piezoelectric element is fixed to the base member with an insulating adhesive, and then the electrode of the piezoelectric element is attached with a conductive adhesive. The method of manufacturing a piezoelectric sensor according to claim 8, further comprising a step of connecting to a lead conductor.