JPH0835980A - Piezoelectric acceleration sensor - Google Patents

Abstract

PURPOSE:To improve reliability by preventing the peeling of a conductive bonding agent, which connects an output terminal and a piezoelectric element, caused by molding pressure at the time of resin molding. CONSTITUTION:A shield case 6 is inserted so that a piezoelectric element 1 is coupled into a supporting body 2, which supports one end part of the piezoelectric element 1. One end of an output terminal 4 is exposed in the vicinity of the bottom surface of a recess part 5 of the supporting body 2. Inlet ports 6b, through which a bonding agent flows in, are provided at both side surfaces of the shield case 6. After the shield case 6 is coupled with the supporting body 2, the bonding agent is made to flow through the inlet ports 6b. The bonding agent becomes an enclosure 10 for easing molding pressure so as to fill the gap between the shield case 6 and the supporting body 2. Thus, the molding pressure acting when resin molding is performed is eased by the enclusure 10, and the peeling of a conductive bonding agent 30 connecting the output terminal 4 and the piezoelectric element 1 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric acceleration sensor for detecting acceleration of shock or vibration.

[0002]

2. Description of the Related Art Conventionally, various types of piezoelectric acceleration sensors have been used for detecting shock or vibration acceleration. The applicant of the present invention has already used piezoelectric acceleration sensors as shown in FIGS. Proposing a sensor (Japanese Patent Application No. 6-1708)
(See No. 6). In this piezoelectric acceleration sensor, a pair of thin plate-shaped output terminals 4 are integrally fixed by insert molding to a support body 2 formed of a synthetic resin in a substantially U shape.
A recess 5 communicating with the insertion portion 3 of the support 2 is provided, and one end of each of the output terminals 4 and 4 is exposed near the bottom surface in the recess 5. A conductive adhesive 30 such as silver paste is provided near the bottom surface of the recess 5 where the electrodes 1a, 1a of the piezoelectric element 1 having one end inserted in the insertion portion 3 of the support 2 and the output terminals 4, 4 are adjacent to each other. Filling is performed, and the piezoelectric element 1 and the output terminal 4 are adhered to each other with the conductive adhesive 30, and conduction is obtained between the electrode 1a of the piezoelectric element 1 and the output terminal 4 via the conductive adhesive 30.

A metallic shield case 6 formed in a cylindrical shape with a bottom is fitted on the support 2 so that the piezoelectric element 1 is housed therein. Since the piezoelectric element 1 has a high impedance and is easily affected by noise, the shield case 6 shields the piezoelectric element 1 from external noise. The ground terminals 7 formed by bending a thin plate member into a substantially L shape are connected to both side surfaces of the outer wall of the shield case 6, respectively. Since the support 2 is made of synthetic resin, the shield case 6
The insulation between the piezoelectric element 1 and the output terminal 4 can be maintained.

Further, the other end of the output terminal 4 not connected to the electrode 1a of the piezoelectric element 1 and one end of the ground terminal 7 not connected to the shield case 6 are projected to the outside, and the shield case 6 and the support 2 are resin-molded. A piezoelectric acceleration sensor is formed.

[0005]

By the way, as shown in FIG. 8, since there is a gap between the support 2 and the shield case 6 fitted to the support 2, these are resin-molded. The support 2 and the shield case 6 are compressed inward by the molding pressure that acts at the time. On the other hand, a stress that fills the gap, that is, a force that pushes the shield case 6 outward is applied to the support 2. As a result, the support 2 has a substantially U shape,
There is a problem that stress acts on the rear end portion (the portion surrounded by the dotted line in FIG. 8), and as a result, the conductive adhesive 30 connecting the output terminal 4 and the piezoelectric element 1 peels off.

The present invention is intended to solve the above problems, and improves the reliability by preventing peeling of the conductive adhesive that connects the output terminal and the piezoelectric element due to molding pressure during resin molding. An object is to provide a piezoelectric acceleration sensor.

[0007]

In order to achieve the above object, the invention of claim 1 is a piezoelectric element, a support having an insertion portion for inserting and supporting one end of the piezoelectric element, and an inside of the insertion portion of the support. A pair of output terminals whose one ends are exposed so as to face each other and whose one ends are connected to electrodes on both side surfaces of the piezoelectric element, and a metal shield which is fitted to the support so as to house the piezoelectric element. The support is provided with a recess that communicates with the insertion portion, the case includes a case, one end of each of the pair of output terminals is exposed near the bottom of the recess, and the recess is filled with a conductive adhesive. While connecting the electrodes of the piezoelectric element and the output terminal, the other end of the output terminal and the other end of the ground terminal whose one end is connected to the metal shield case are projected outwardly. The resin model A piezoelectric acceleration sensor formed by field, the inclusions of molding pressure moderately sum into the gap between the support and the shield case is interposed, characterized by comprising.

The invention of claim 2 is characterized in that, in the invention of claim 1, the inclusion for relaxing the molding pressure is made of an adhesive. The invention of claim 3 is the same as the invention of claim 2,
The shield case is characterized in that an inflow hole for inflowing an adhesive agent is provided in a gap between the support and the shield case.

According to a fourth aspect of the present invention, in the first aspect of the invention, the inclusion for relaxing the molding pressure is a rib protruding from the outer peripheral surface of the support.

[0010]

According to the structure of the invention of claim 1, a piezoelectric element, and a support having an insertion portion for inserting and supporting one end of the piezoelectric element,
A pair of output terminals, one ends of which are exposed so as to face each other in the insertion portion of the support body, and one end of which is connected to electrodes on both side surfaces of the piezoelectric element, and which are fitted to the support body so as to house the piezoelectric element. A metal shield case, and a recess that communicates with the insertion part is provided in the support, one end of each of the pair of output terminals is exposed near the bottom of the recess, and a conductive adhesive is applied inside the recess. Fill the agent to connect the electrode of the piezoelectric element and the output terminal, and project the other end of the output terminal and the other end of the ground terminal connected to the metal shield case to the outside. A piezoelectric acceleration sensor formed by resin-molding a shield case and a support body, in which a molding pressure relaxing inclusion is interposed in the gap between the support body and the shield case. The relaxation inclusions relax the molding pressure applied to the support and the shield case during resin molding, and the stress of the support due to the molding pressure is hardly generated, and the output terminal and the piezoelectric element are connected. It is possible to prevent the conductive adhesive from peeling off.

According to the second aspect of the invention, since the inclusion for relaxing the molding pressure is made of an adhesive, the shield case and the support can be bonded and fixed at the same time as the relaxation of the molding pressure. In the structure of the invention of claim 3, since the shield case is provided with the inflow hole for inflowing the adhesive into the gap between the support and the shield case, the molding pressure is applied after the shield case is fitted to the support. The adhesive, which is an intervening material for relaxing, can be made to flow in through the inflow hole of the shield case, and the step of interposing the intervening material can be simplified to improve the assembly workability.

In the structure of the fourth aspect of the present invention, since the inclusion for relaxing the molding pressure is formed by the rib projectingly provided on the outer peripheral surface of the support, the molding pressure is alleviated and at the same time, the rib is provided inside the shield case. The support is press-fitted so that the shield case and the support can be prevented from coming off.

[0013]

【Example】

(Embodiment 1) This embodiment will be described with reference to FIGS.
The basic structure of the piezoelectric acceleration sensor according to the present embodiment is almost the same as that of the conventional example, the common portions are denoted by the same reference numerals, and the description thereof will be omitted. Only explained.

As shown in FIG. 1, the support 2 is formed of synthetic resin into a substantially U shape, and a pair of thin plate-shaped output terminals 4 are integrally fixed by insert molding. In addition, a recess 5 communicating with the insertion portion 3 of the support body 2 into which one end of the piezoelectric element 1 is inserted is provided in the support body 2, and one end of each of the output terminals 4 and 4 is provided in the recess 5 near the bottom surface. Each is exposed. Here, in the recess 5, the electrodes 1a of the piezoelectric element 1,
1a and the output terminals 4 and 4 are adjacent to each other, and a conductive adhesive 30 such as silver paste is filled in the vicinity of the bottom surface of the recess 5 to connect the piezoelectric element 1 and the output terminal 4 with the conductive adhesive. At the same time, the electrode 1a of the piezoelectric element 1 and the output terminal 4 are electrically connected via the conductive adhesive 30.

Since the piezoelectric element 1 has a high impedance and is easily affected by noise, the metal shield case 6 shields the piezoelectric element 1 from external noise. That is, the shield case 6 is fitted on the support body 2 so that the piezoelectric element 1 is housed therein. FIG. 2 is a perspective view showing the shield case 6, and the shield case 6 is formed in a bottomed tubular shape with one opening. A notch 6a is formed on both side surfaces of the shield case 6 and extends from the open end. The notch 6a has a shape of a step 2a formed around the output terminal 4 protruding from the side surface of the support 2. It is shaped so as to follow the periphery. The step portion 2a ensures the insulation between the output terminal 4 and the shield case 6.

Here, when the shield case 6 is fitted on the support body 2, the inner peripheral surface of the shield case 6 and the support body 2 are covered.
There is a slight gap between the outer peripheral surface and the outer peripheral surface. Therefore, as described in the prior art, a stress that fills the above-mentioned gap is generated in the support body 2 by the molding pressure applied when the shield case 6 and the support body 2 are integrally resin-molded. In addition, coupled with the fact that the support body 2 is substantially U-shaped, the above-mentioned stress acts on the end portion side of the support body 6, and the stress adheres the output terminal 4 and the electrode 1a of the piezoelectric element 1 to each other. The agent 30 peels off and the output terminal 4 and the piezoelectric element 1 become non-conductive.

Therefore, a circular inflow hole 6b facing the side surface of the support body 2 when the shield case 6 is fitted on the support body 2 is provided in the vicinity of the notches 6a formed on both side surfaces of the shield case 6. While the shield case 6 is fitted on the support body 2, an adhesive 10 is introduced into the shield case 6 through the inflow hole 6b to form the inclusion 10 for relaxing the molding pressure, which is interposed in the gap by the adhesive. are doing.

According to the above construction, since the molding pressure relaxing inclusion 10 made of an adhesive is interposed in the gap formed between the inner peripheral surface of the shield case 6 and the outer peripheral surface of the support 2, the support 2 is formed. The molding pressure applied when the resin and the shield case 6 are integrally resin-molded can be relieved by the inclusions 10, and the conductive adhesive 30 that bonds the output terminal 4 and the piezoelectric element 1 peels off. Support 2
It is possible to prevent the occurrence of conduction failure due to the peeling of the conductive adhesive 30. Further, since the support 2 and the shield case 6 are fixed by the adhesive,
The shield case 6 can be prevented from coming off the support body 2 at the same time. Further, in this embodiment, since the adhesive which becomes the inclusion 10 is made to flow from the inflow hole 6b formed in the shield case 6, the adhesive is shielded after the shield case 6 is fitted on the support body 2. There is an advantage that it can be introduced from the inflow hole 6b of the case 6, and the process of interposing the inclusion 10 can be simplified to improve the assembly workability.

(Embodiment 2) This embodiment will be described with reference to FIGS. As with the piezoelectric acceleration sensor of the first embodiment, the basic structure of the piezoelectric acceleration sensor of the present embodiment is almost the same as that of the conventional example. Therefore, the common portions are denoted by the same reference numerals and the description thereof will be omitted. Only the characteristic parts of this embodiment will be described.

In the piezoelectric type acceleration sensor of this embodiment, a molding pressure relaxing inclusion for filling a gap between the inner peripheral surface of the shield case 6 and the outer peripheral surface of the support body 2 is formed on the outer peripheral surface of the support body 2. It is characterized in that it is the rib 11 of the ridge. The ribs 11 are provided on both side surfaces of the support body 2 from which the output terminals 4 project, and on both sides of the support body 2 in the vicinity of both ends with the piezoelectric element 1 sandwiched between the surfaces of the support body 2 that are open. The ribs 11 projecting from each other have their longitudinal directions substantially orthogonal to each other. Then, the shield case 6 is attached to the support 2
If it is fitted to the shield case 6, the shield case 6 is pushed out by these ribs 11 and the support 2 is pressed into the shield case 6.

According to the above-mentioned structure, the ribs 11 serve as intervening materials for relaxing the molding pressure filling the gap between the inner peripheral surface of the shield case 6 and the outer peripheral surface of the support body 2, and thus the support body 2 and the shield case. The rib 11 can relieve the molding pressure applied when resin-molding 6 and 6 integrally. Moreover, since the support body 2 is pressed into the shield case 6 by these ribs 11, the support body 2 and the shield case 6 are firmly fixed without using an adhesive or the like.
It is possible to prevent it from coming off.

By the way, in the structures of the above-described first and second embodiments, an external force having a relatively large moment may be applied to the output terminal 4 protruding from the supporting portion 2 when the piezoelectric acceleration sensor is assembled. In such a case, since the output terminal 4 is planar with respect to the direction of the external force of the moment, that is, the external force of the moment acts in the thickness direction of the output terminal 4, the output terminal 4 and the piezoelectric element 1 are separated from each other. The adhered conductive adhesive 30 may peel off.

Therefore, in order to prevent the above-mentioned problems, a rectangular recess 4a is provided in a portion of the output terminal 4 which is bonded to the piezoelectric element 1 by the conductive adhesive 30. That is, since the conductive adhesive 30 filled in the recess 5 of the support body 2 is also filled in the recess 4a, the conductive adhesive 30 filled in the recess 4a against the external force of the moment as described above. The agent 30 and the recess 4a are engaged with each other,
By the so-called anchor effect, the force acting on the output terminal 4 in the peeling direction of the conductive adhesive 30 is reduced, and the conductive adhesive 30 that bonds the output terminal 4 and the piezoelectric element 1 peels as described above. It is possible to avoid such a problem as to occur. If the tip portion of the output terminal 4 is formed in a substantially U-shape as shown in FIG. 5, the force acting on the output terminal 4 in the peeling direction of the conductive adhesive 30 can be further reduced.

[0024]

According to the first aspect of the present invention, the piezoelectric element, the support having the insertion part for inserting and supporting one end of the piezoelectric element, and the one end exposed so as to face each other in the insertion part of the support are provided. A pair of output terminals, one end of which is connected to the electrodes on both side surfaces of the piezoelectric element, and a metal shield case fitted to the support so as to house the piezoelectric element,
The support is provided with a recess communicating with the insertion portion, one end of each of the pair of output terminals is exposed near the bottom surface of the recess, and the recess is filled with a conductive adhesive to output the piezoelectric element electrode and output. The shield case and the support are resin-molded so that the other end of the output terminal and the other end of the ground terminal having one end connected to the metal shield case are connected to the terminal and project outwardly. Since the piezoelectric acceleration sensor is formed by interposing a molding pressure relaxing inclusion in the gap between the support and the shield case, the molding pressure relaxing inclusion is used to mold the resin during molding. The molding pressure applied to the support and the shield case is relaxed, the stress of the support is hardly generated by the molding pressure, and the conductive adhesive connecting the output terminal and the piezoelectric element is prevented from peeling off. There is an effect that can be stopped.

According to the invention of claim 2, since the inclusion for relaxing the molding pressure is made of an adhesive, there is an effect that the shielding case and the support can be bonded and fixed at the same time when the molding pressure is alleviated. According to the invention of claim 3, since the shield case is provided with the inflow hole for inflowing the adhesive into the gap between the support body and the shield case, after the shield case is fitted on the support body, the molding pressure is relaxed. The adhesive, which is the inclusion, can be introduced from the inflow hole of the shield case, and the process of interposing the inclusion can be simplified and the assembly workability can be improved.

According to the invention of claim 4, since the inclusion for relaxing the molding pressure comprises a rib protrudingly provided on the outer peripheral surface of the support, the molding pressure is alleviated, and the rib supports the support in the shield case. Has an effect that the shield case and the support can be prevented from coming off.

[Brief description of drawings]

FIG. 1 is a plan sectional view of a main part showing a first embodiment.

FIG. 2 is a perspective view showing the above shield case.

FIG. 3 is a perspective view showing a main part of the same.

FIG. 4 is a plan sectional view showing a main part of the same.

5A and 5B are diagrams showing a configuration of an output terminal in the above.

6A and 6B are views showing a conventional example, in which FIG. 6A is a partially cutaway plan view of the whole, FIG. 6B is a side sectional view taken along line AA of FIG. 6A, and FIG. is there.

FIG. 7 is a perspective view showing a main part of the above.

FIG. 8 is a plan sectional view showing a main part of the above.

[Explanation of symbols]

 1 Piezoelectric Element 1a Electrode 2 Support 4 Output Terminal 6 Shield Case 10 Inclusions for Relieving Molding Pressure 30 Conductive Adhesive

Claims (4)

[Claims] 1. A piezoelectric element, a support having an insertion portion for inserting and supporting one end of the piezoelectric element, and electrodes on both side surfaces of the piezoelectric element with one end exposed so as to face each other in the insertion portion of the support. A pair of output terminals whose one end is connected to, and a metal shield case fitted to the support so as to house the piezoelectric element, and a recess communicating with the insertion portion is provided in the support, One end of each of the pair of output terminals is exposed in the vicinity of the bottom surface in the recess, and a conductive adhesive is filled in the recess to connect the electrode of the piezoelectric element to the output terminal and the other end of the output terminal. And a shield case made of metal and one end of which is connected to the other end of a ground terminal, the shield case and the support body being resin-molded so that the piezoelectric acceleration sensor includes the support body and the shield case. A piezoelectric acceleration sensor, characterized in that an intervening material for relaxing the molding pressure is interposed in a gap between the piezoelectric acceleration sensor and the base. 2. The piezoelectric acceleration sensor according to claim 1, wherein the inclusion for relaxing the molding pressure is made of an adhesive. 3. The piezoelectric acceleration sensor according to claim 2, wherein the shield case is provided with an inflow hole for injecting the adhesive into a gap between the support and the shield case. 4. The piezoelectric acceleration sensor according to claim 1, wherein the inclusion for relaxing the molding pressure comprises a rib provided on the outer peripheral surface of the support.