JPH09113533A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor, which can prevent the generation of leakage of the adhesive agent to be used in fixing a piezoelectric element to a support and in which an upper and a lower positions of the piezoelectric element are constant so as to obtain the stabilized characteristic. SOLUTION: A support 2 is a resin molding, of which outline is formed into the nearly rectangular parallelopiped, and a space 10, of which upper surface is opened, is formed in the interior of the support 2, and output terminals 6a, 6b, of which tips face to the inside of the space 10, are inserted in both side surfaces for holding by insert molding. One side surface crossing both the side surfaces, in which the output terminals are inserted, is formed with a horizontal hole 11, which has a rectangular cross section and which is inclined in relation to an axis in the vertical direction, for passing. One end of the piezoelectric element 1 having the nearly rectangular cross section is passed through the horizontal hole 11 in an inclined state, and this one end is made to face the inside of the space 10 so as to electrically connect both the side surfaces of the piezoelectric element 1 and the corresponding output terminals 6a, 6b in the space 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial detection cantilever type acceleration sensor using a piezoelectric element.

[0002]

2. Description of the Related Art FIGS. 11 and 12 show the structure of a conventional biaxial piezoelectric acceleration sensor. In the illustrated conventional example, a support body for supporting and fixing a piezoelectric element 1 is a primary molded body. The upper surface of 2'is open and the output terminals 6a, 6
b is inserted into the inner space 10 'by insert molding. Then, a groove 11 'having an open upper end is penetrated through one side surface orthogonal to both side surfaces through which the output terminals 6a, 6b are penetrated, and the tip portion of the piezoelectric element 1 is inserted into the space 10' through this groove 11 '. I am facing.

Ribs 17a and 17b provided with taper for inclining and supporting the piezoelectric element 1 are provided on both sides in the cavity 10 ', and one end of the piezoelectric element 1 inserted in the cavity 10' is provided. Downward side surface and the corresponding output terminal 6a
The silver paste 20 in the recess formed between the upper surface of the tip of the
a'is injected and applied to electrically connect the two, and silver paste 20b 'is applied and applied between the upward side surface of one end of the piezoelectric element 1 and the corresponding upper surface of the output terminal 6b. Are electrically connected, and an adhesive 21 ′ is applied and injected so as to cover the piezoelectric element 1 and the silver pastes 20a ′ and 20b ′, and the piezoelectric element 1 is fixed.

[0004]

By the way, in the conventional example of the above structure, when the ribs 17a and 17b are formed due to the restriction of the die structure such as the slide core removal, the positions of the ribs 17a and 17b need to be shifted, and the upper surface of the ribs 17a and 17b must be displaced. Since the piezoelectric element 1 is inserted into the space 10 ′ through the groove 11 ′ of the opening, a large amount of the adhesive 21 ′ leaks to the upper portion of the piezoelectric element 1, and the fixing position of the piezoelectric element 1 varies, which causes a voltage difference. There is a problem that the sensitivity varies among products. Further, there arises a problem that the upper and lower positions of the piezoelectric element 1 vary, the piezoelectric element 1 tilts upward and downward, and this also causes variation in voltage sensitivity.
There is a problem that the piezoelectric element 1 comes into contact with the metal case when it is housed in the metal case for shielding.

Further, since the positions of the upper surfaces of the output terminals 6a and 6b are set to the same height, the silver pastes 20a 'and 20b' are formed.
12, the bonding area of the silver paste 20a ′ on the downward side surface of the piezoelectric element 1 is narrowed, and the peeling strength against heat and external force is reduced. There is a problem that the distance between the upper surface and the upper surface of the tip portion of the output terminal 6a becomes small and the silver paste 20a ′ that has spread to the upper surface of the piezoelectric element 1 causes a short circuit between the upper and lower electrodes of the piezoelectric element 1. It was

The present invention has been made in view of the above problems, and it is an object of the invention of claim 1 that an adhesive used for fixing a piezoelectric element with a support leaks out onto the piezoelectric element. Another object of the present invention is to provide an acceleration sensor which can prevent the above-mentioned phenomenon and can obtain stable characteristics without the upper and lower positions of the piezoelectric element being varied. In addition to the object of the invention of claim 1, an object of the invention of claim 2 is to provide an acceleration sensor capable of easily fixing a piezoelectric element.

An object of the invention of claim 3 is to provide an acceleration sensor in which the tilt angle of the piezoelectric element can be accurately obtained while being press-fitted and fixed. The object of the invention of claim 4 is to make the bonding area of the conductive adhesive for connecting the both side surfaces of the piezoelectric element and each output terminal substantially the same as that of the downward side surface side and the upward side surface side. Another object of the present invention is to provide an acceleration sensor in which variation in peel strength with respect to external force and external force is small, peel strength is increased, stable characteristics are obtained, and a short circuit between different poles on the upper portion of a piezoelectric element does not easily occur.

[0008]

In order to achieve the above object, according to the invention of claim 1, a support made of a synthetic resin molded product for supporting and fixing one end of a piezoelectric element having a rectangular cross section is formed into a substantially rectangular parallelepiped. The tip of the output terminal penetrating from both sides of the support is exposed in the space provided inside the support, and the one side of the support orthogonal to the both sides is penetrated from the outside to the space. Then, a lateral hole into which one end of the piezoelectric element is inserted is opened so that both side surfaces of the piezoelectric element are inclined, and one end of the piezoelectric element that is inserted through the lateral hole and faces the cavity is fixed by adhesion. It is characterized in that the corresponding ends of the output terminals are electrically connected to both side surfaces of the support, and the wall of the support body exists at the upper portion of the piezoelectric element inserted in the lateral hole. The adhesive injected into the void will spread to the top of the piezoelectric element. It is possible to prevent the writing of, can prevent the vertical movement of the piezoelectric element, as a result there is no variation in the position of the fixed end of the piezoelectric element, it is possible to stabilize the characteristics of the piezoelectric element.

According to a second aspect of the present invention, in the first aspect of the present invention, a rib is provided on the inner surface of the lateral hole, the rib being in pressure contact with the outer peripheral surface of the piezoelectric element. Can be press-fitted and inserted, so that the piezoelectric element can be easily fixed. In the invention of claim 3, claim 2
In the invention, since the ribs are provided on the inner surface other than the two inner surfaces of the lateral hole that sets the inclination angle of the piezoelectric element,
The tilt angle of the piezoelectric element can be accurately obtained.

According to a fourth aspect of the present invention, the tip of the output terminal corresponding to the downward side surface of the piezoelectric element is lower than the tip of the output terminal corresponding to the upward side surface of the output terminal. The front end of the piezoelectric element is bent, and both sides of the piezoelectric element and the corresponding output terminals are electrically connected with a conductive adhesive. The adhesive areas of the agents can be made substantially the same, and therefore, stable characteristics can be obtained with little variation in peel strength against external force or heat.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a schematic perspective view of the embodiment of the present invention with a part thereof omitted. In the present embodiment, one end portion of a piezoelectric element 1 composed of a bimorph type piezoelectric element in which two piezoelectric ceramic pieces are joined is shown. The piezoelectric element 1 is supported and fixed by a support 2 made of a synthetic resin molded product.
And the support 2 are housed in a metal case 3 for shielding, and the metal case 3 is housed in a case 4 made of heat-resistant liquid crystal resin by insert molding.
Ground terminals 5, 5 connected to the metal case 4 on both sides of
Is connected to the piezoelectric element 1 in the support 2, and the metal case 3
The positive and negative output terminals 6a and 6b insulated from each other are exposed, and the piezoelectric element 1 has a predetermined angle with respect to a vertical axis orthogonal to the bottom surface of the case 4 (bottom surface of the support body 2). The cantilever type of high sensitivity capable of detecting accelerations in two directions of an axis X parallel to the bottom surface of the case 4 and an axis Y perpendicular to the bottom surface of the case 4 by inclining only and supporting and fixing to the support 2. It constitutes an acceleration sensor.

Here, the relationship between the piezoelectric element 1 and the support 2 which is a main constituent element will be further described. FIG. 1 shows a conceptual relationship between the piezoelectric element 1 and the support 2 of this embodiment. The support 2 is a resin molded product whose outer shape is a substantially rectangular parallelepiped,
A void 10 having an open upper surface is formed inside, and the void 10
The output terminals 6a and 6b, the ends of which are exposed to the inside, are penetrated through both sides by insert molding. Further, a lateral hole 11 having a rectangular cross section and inclined with respect to an axis in the vertical direction in the drawing is formed through one side surface orthogonal to the both side surfaces, and the piezoelectric element 1 having a rectangular cross section is formed through the lateral hole 11. One end of the piezoelectric element 1 is inserted in a tilted state so that the one end faces the inside of the void 10, and in the void 10 both side surfaces of the piezoelectric element 1 and the corresponding output terminals 6a, 6b are electrically connected. It is also fixed by adhesion.

3 to 6 are a top view, a front view, a sectional view and a side view, respectively, of a support body 2 formed by inserting the output terminals 6a and 6b, and the support body 2 is as shown in FIG. The output terminals 6a and 6b and the ground terminals 5 and 5 are previously formed by punching out the metal hoop material 7, and after this formation, insert molding is performed between the opposed tip portions of the output terminals 6a and 6b.

When one side surface of the support body 2 in which the lateral hole 11 is opened is defined as a front side, a projecting portion 12 is integrally formed in the center of both side surfaces from a slightly rearward side to a rearward side, and the side surface of the projecting portion 12 outputs. The terminals 6a and 6b are projected. The protruding portion 12 is a notch groove (not shown) provided in the rear portion of the metal case 3.
The output terminals 6a and 6b are projected to the outside without contacting the metal case 3, and the metal case 3 is positioned.

At the rear end of the support body 2, a rear end portion 2a projecting in the outer peripheral direction from the support body 2 is formed.
Function as a stopper. As shown in FIG. 8, the lateral hole 11 has a rectangular cross-sectional shape, and has two downward facing side surfaces and a lower surface of the piezoelectric element 1 into which two upward facing inclined surfaces a and b are inserted. Contact each other to form a surface that determines the inclination angle (for example, 25 °) of the piezoelectric element 1, and the other two downward-facing inclined surfaces c and d have a cross-section that is in pressure contact with the upper side surface of the piezoelectric element 1 and the upper surface. Circular ribs 13a and 13b are formed in the insertion direction, and the piezoelectric element 1 can be press-fitted into the lateral hole 11 without rattling due to the ribs 13a and 13b.

At the bottom of the cavity 10, a surface 1 for supporting the lower surface of the piezoelectric element 1 inserted in an inclined state and the downwardly inclined surface.
0a and 10b are continuously formed on the surfaces a and b, and a groove 14a is formed in the center of the surface 10a that supports the lower surface of the piezoelectric element 1 so as to cross the width direction of the surface 10a.
The groove 14a is connected to a groove 14b formed in the vertical direction along one side surface of the space 10. The hole 16 is a holding pin removal hole at the time of insertion. Output terminals 6a, 6
Although the height positions of the b projecting from both side surfaces of the support body 1 are the same, the tip of the output terminal 6a corresponding to the side surface of the piezoelectric element 1 which is the downward inclined surface in the space 10 is connected to the output terminal 6b.
The tip of the output terminal 6a is bent and formed so as to be located below the tip of the output terminal 6a, and the output terminals 6a and 6b are exposed in the space 10. Recesses 15 are formed on the upper surfaces of the tips of the output terminals 6a and 6b facing the space 10. FIG. 9 is a perspective view of the tip of the output terminal 6a provided with the recess 15.

When fixing the piezoelectric element 1 to the support 2, the ribs 13a and 13b are formed in the lateral hole 11 at one end before the output terminals 6a and 6b and the ground terminals 5 and 5 are separated from the metal hoop material. Using, the one end of the piezoelectric element 1 is press-fitted and inserted, and the one end is exposed in the space 10. Next, as shown in FIG. 10, a silver paste 20a, which is a conductive adhesive, is inserted into the recess 9 formed by the upper portion of the downward side surface of the piezoelectric element 1 and the tip of the output terminal 6a from the upper opening of the void 10. By injection coating, the output terminal 6a and the downward side surface of the piezoelectric element 1 are electrically connected by the silver paste 20a, and the upward side surface of the piezoelectric element 1 and the recess 10 are formed from the upper surface of the tip of the output terminal 6b. The silver paste 20b is injected and applied to the recess 8 formed by the wall rising from the upper end of the surface 10a to electrically connect the upward side surface of the piezoelectric element 1 and the output terminal 6b with the silver paste 20b. At this time, the height position of the output terminal 6a is set lower than the height position of the output terminal 6b, so that the adhesion area between the output terminal 6a and the downward side surface of the piezoelectric element 1 is made smaller than that of the output terminal 6b and the piezoelectric element 1. The area is almost the same as the area of adhesion to the side surface facing upward, and stable characteristics can be obtained with little variation in peel strength of the silver paste against external force or heat. Further, since the silver pastes 20a and 20b enter the concave portions 15 of the output terminals 6a and 6b, the peeling strength is further increased.

After the silver pastes 20a and 20b are applied and applied, for example, an epoxy resin adhesive 21 is injected from the top opening. At this time, the adhesive 21 wraps around the lower surface of the piezoelectric element 1 via the groove 14b and the groove 14a. Therefore, even if the silver pastes 20a, 20b wrap around by the capillary phenomenon, the paste 20a, 20b is not grooved. 14 and the adhesive 21 inside thereof are used to divide and prevent connection.

After that, the adhesive 21 and the silver paste 20a,
When the binder of 20b is cured, the piezoelectric element 1 is electrically connected to the output terminals 6a and 6b, and the space 10
It will be fixed inside. The piezoelectric element 1 is attached to the support 2
Since the wall of the support body 2 is present also on the upper portion of the piezoelectric element 1 by being press-fitted and inserted into the lateral hole 11 of this, the wall prevents the adhesive 21 from wrapping around the upper portion of the piezoelectric element 1,
Prevents variation in the position of the fixed end. At the same time, the wall suppresses the inclination of the piezoelectric element 1 in the direction of gravity and eliminates the variation in the voltage sensitivity of the piezoelectric element 1.

After fixing one end of the piezoelectric element 1 to the support 2 in this manner, the metal case 3 is covered to house the piezoelectric element 1 in the metal case 3 and the ground terminals 5 are provided on both side surfaces of the metal case 3. 1, the end bent pieces 5 are brought into contact with each other and fixed by welding, and then the case 4 is molded by insert molding. After this molding, the output terminals 6a and 6b and the ground terminals 5 and 5 are separated from the metal hoop material 7, and the case shown in FIG. The acceleration sensor shown in is completed. When the case 4 is molded, the support body 2 which is the primary molding body has no groove or the like opened in the peripheral wall, so that it is strong against external force and the range of molding conditions for the secondary molding can be widened.

Since the acceleration sensor of the present embodiment obtained as described above has a cantilever structure, it has a higher sensitivity than the acceleration sensor having a double-beam structure, and the metal case 3 is strong against external noise. Further, since the output terminals 6a, 6b and the ground terminals 5, 5 are made of metal plate terminals, the reliability of the soldering portion is high, and the metal hoop material 7 is assembled as described above, and the inspection is performed by the metal hoop. Material 7
Can be done on Further, the process and equipment of the conventional example can be used almost as they are, and the process used in the present embodiment can be used as a manufacturing process of the acceleration sensor for one-axis detection.

[0022]

According to the invention of claim 1, a support body for supporting and fixing one end portion of a piezoelectric element having a rectangular cross section is formed in a substantially rectangular parallelepiped shape, and the support body is provided in an inner space of the support body on both sides of the support body. The tip of the piezoelectric element is made to pass through from the side and the one end of the piezoelectric element is made so that both side surfaces of the piezoelectric element are inclined so that one side surface of the support orthogonal to the both side surfaces penetrates the space from the outside. A lateral hole to be inserted is opened, and one end of the piezoelectric element which is inserted through the lateral hole and faces the inside of the cavity is adhered and fixed, and the tips of the output terminals respectively corresponding to both side surfaces of the piezoelectric element are electrically connected. Since the connection is made, the wall of the support body exists at the upper portion of the piezoelectric element inserted in the lateral hole, and this wall can prevent the adhesive injected into the cavity from wrapping around to the upper portion of the piezoelectric element. It is possible to move the piezoelectric element vertically. As a result, there is no variation in the position of the fixed end of the piezoelectric element, and the characteristics of the piezoelectric element can be stabilized. Therefore, there is an effect that an acceleration sensor with stable characteristics can be obtained. Since it is a structure that penetrates the side surface of the support, the strength of the support against external force can be increased compared to the case where an open groove is provided, and the range of molding conditions during secondary molding can be widened,
Further, the conventional processes and equipment can be used almost as they are.

According to a second aspect of the present invention, in the first aspect of the present invention, since a rib that presses against the outer peripheral surface of the piezoelectric element is provided on the inner surface of the lateral hole, the rib presses and inserts the piezoelectric element into the lateral hole. Therefore, there is an effect that the piezoelectric element can be easily fixed. According to the invention of claim 3, in the invention of claim 2, since the ribs are provided on the inner surfaces other than the two inner surfaces of the lateral hole for setting the tilt angle of the piezoelectric element, the tilt angle of the piezoelectric element is accurately obtained. The effect is that you can.

According to a fourth aspect of the present invention, the tip of the output terminal corresponding to the downward side surface of the piezoelectric element is positioned so that the height position of the output terminal is lower than the tip of the output terminal corresponding to the upward side surface. Since the tip of the piezoelectric element is bent, and both sides of the piezoelectric element and the corresponding output terminals are electrically connected with a conductive adhesive, the adhesion of the conductive adhesive on both sides of the piezoelectric element The areas can be made substantially the same, and therefore, there is an effect that stable characteristics can be obtained with less variation in peel strength against external force or heat.

[Brief description of the drawings]

FIG. 1 is a schematic exploded perspective view of a main part of an embodiment of the present invention.

FIG. 2 is a schematic perspective view of the same, with a part thereof omitted.

FIG. 3 is an enlarged top view in which a part of the main part of the above can be omitted.

FIG. 4 is an enlarged front view in which a part of the above-mentioned main part can be omitted.

FIG. 5 is a front cross-sectional view in which a part of the above-mentioned main part can be omitted.

FIG. 6 is a side view in which a main part of the same is broken away.

FIG. 7 is a top view in which a part of the metal hoop material used in the above is omitted.

FIG. 8 is a structural explanatory view of a lateral hole of the above support.

FIG. 9 is an enlarged perspective view in which a part of the output terminal of the same can be omitted.

FIG. 10 is an assembly explanatory diagram of the above.

FIG. 11 is a top view of a conventional support body.

FIG. 12 is an assembly explanatory diagram of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Support 10 Vacancy 11 Horizontal hole 6a, 6b Output terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohisa Tanaka 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (4)

[Claims] 1. A support made of a synthetic resin molded product for supporting and fixing one end of a piezoelectric element having a rectangular cross section is formed into a substantially rectangular parallelepiped.
The tip of the output terminal penetrating from the side surfaces on both sides of the support is exposed in the space provided inside the support,
A lateral hole is inserted into one side surface of the support orthogonal to the both side surfaces so that one end of the piezoelectric element is inserted so that both side surfaces of the piezoelectric element are inclined from the outside so that both side surfaces of the piezoelectric element are inclined, and the lateral hole is inserted through the lateral hole. An acceleration sensor, wherein one end of the piezoelectric element exposed to the inside of the cavity is adhesively fixed, and the ends of the corresponding output terminals are electrically connected to both side surfaces of the piezoelectric element. 2. The acceleration sensor according to claim 1, wherein a rib that is in pressure contact with an outer peripheral surface of the piezoelectric element is provided on an inner surface of the lateral hole. 3. The acceleration sensor according to claim 2, wherein the rib is provided on an inner surface other than the two inner surfaces of the lateral hole that sets the inclination angle of the piezoelectric element. 4. The tip of the output terminal is bent so that the tip of the output terminal corresponding to the downward side surface of the piezoelectric element is lower than the tip of the output terminal corresponding to the upward side surface. 2. The acceleration sensor according to claim 1, wherein the acceleration sensor is formed in a curved shape and electrically connected between both side surfaces of the piezoelectric element and the corresponding output terminals with a conductive adhesive.