JP2001083175A - Acceleration sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an acceleration sensor that has relatively simple structure, is inexpensive, and has high performance. SOLUTION: Two piezoelectric element materials 51a and 51b with specific length are glued each other so that the polarization directions are opposite, a piezoelectric element block body 51 with a first outer surface 55 in parallel with the polarization direction and a second outer surface 57 in parallel with the first outer surface 55 is formed, the piezoelectric element block body 51 is cut along the longitudinal direction in parallel with the first outer surface 55, a first inner surface 56 in parallel with the first outer surface 55 and a second inner surface 58 are formed, first and second electrodes 59 and 60 being separated along the longitudinal direction nearly at the center are provided on the first outer surface 55 and a third electrode is provided on the first inner surface 56, the area between the first inner surface 56 and the second inner surface 58 is buried with an adhesive 64, the piezoelectric element block body 51 is cut by a surface that is vertical to the longitudinal direction, and a waste part 65 is excluded, and a plurality of vibration conversion parts are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and more particularly to an acceleration sensor used for a vehicle or the like and having a piezoelectric element for converting vibration received by the vehicle into an electric signal.

[0002]

2. Description of the Related Art Conventionally, practically used acceleration sensors are known which detect acceleration by various methods such as an electromagnetic type, a piezoelectric type and a semiconductor type. The piezoelectric acceleration sensor includes a piezoelectric element that converts vibration into an electric signal. For example, there is a piezoelectric acceleration sensor as shown in FIG. This conventional piezoelectric acceleration sensor 1 includes a vibration transducer 1
0, a support plate 11 integrally supporting the vibration transducer 10 and the vibration transducer 10, a printed circuit board 13 electrically connected to the vibration transducer 10, and a printed circuit board 13 and connection pins 14. The printed circuit board 17 on which the electric components 15 such as an electric impedance converter, an amplifier, and a correction circuit are mounted is electrically connected to the support plate 11, and is electrically connected and held by resistance welding or the like. Vessel 10, printed circuit boards 13 and 17
And a case 18 for accommodating the same.

[0003] The support plate 11 and the case 18 are generally connected to the ground of an electric circuit and are configured as a shield.

A vibration transducer 10 of a conventional piezoelectric acceleration sensor 1 includes a pair of disk-shaped piezoelectric elements 3 having a center hole 3a.
And a disk-shaped metal diaphragm 7 having both surfaces 7a and 7b to which the piezoelectric element 3 is adhered by a conductive adhesive or the like.

Each of the piezoelectric elements 3 has a large-diameter disk-shaped wiring electrode 5a having a center hole on at least one surface.
And the small-diameter electrode 5b are formed so as to be coaxial and double, and the electrodes 5a and 5b are electrically connected to the printed circuit board 13 by wires 6 by wire bonding or the like.

Each piezoelectric element 3 is made of ceramics or the like,
As shown in FIG. 12, the polarization is performed in directions indicated by arrows D1 and D2 substantially perpendicular to the surface of the piezoelectric element 3, respectively.

As shown in the equivalent connection diagram of FIG.
In the conventional acceleration sensor 1, the pair of piezoelectric elements 3 of the vibration transducer 10 are electrically connected to each other in parallel via electrodes 5a and 5b. The electrode 5a is electrically connected to an external oscillator 19, and the external oscillator 1
By applying a predetermined voltage from 9, the diaphragm 7 is vibrated. The electrode 5a is an electrode for a self-diagnosis function described later. On the other hand, the potential generated in the piezoelectric element 3 in response to the vibration of the diaphragm 7 is taken out through the electrode 5b. In this way, the acceleration applied to the acceleration sensor 1 is extracted as an electric signal via the electrode 5b according to the vibration of the diaphragm 7 and detected.

A predetermined voltage is externally applied to one of the electrodes 5a to vibrate the vibrating body 7, and the potential generated by the vibration is taken out from the other electrode 5b. The self-diagnosis function of the quality of the product can be realized.

[0009] Figure 13 is an example of a frequency characteristic in a constant acceleration for vibration of the acceleration sensor, as shown in figure, in the vicinity of the resonance point f _0, it has a high Q value, a frequency lower than the resonance point f ₀ The region shows flat characteristics. In general, the intended use of the acceleration sensor is used to select the oscillation output of the near _zero flats or resonance point f.

[0010]

However, in the conventional acceleration sensor 1 as described above, the structure is complicated and the bonding of the piezoelectric element 3 to the vibration plate 7 is required.
There was a problem that the cost was increased.

Further, the vibration converter 10 includes a metal vibrating body 7.
And the piezoelectric element 3, there is a problem that the sensitivity and characteristics tend to vary, and the temperature characteristics tend to deteriorate.

Further, in the conventional acceleration sensor 1, since the direction of polarization in the piezoelectric element 3 is perpendicular to the plane on which the electrodes 5a and 5b are provided, a pyroelectric voltage is generated on the electrodes. In order to cancel the pyroelectric effect due to the pyroelectric voltage, the electrodes 5a and 5b are electrically connected in series or parallel, respectively, so that the polarization directions in the piezoelectric element 3 are reversed. Cannot be canceled, and in particular, when the acceleration sensor is used in a low frequency region, there is a problem that the operating point of the electric circuit is adversely affected.

Further, in the conventional acceleration sensor 1, a plurality of piezoelectric elements are required to suppress the above-mentioned adverse effect of the pyroelectric effect. Therefore, the structure is complicated, the production is troublesome, and the cost is high. There was a problem of becoming.

The present invention has been made in view of the above-described problems, and has as its object to provide an excellent acceleration sensor having a relatively simple structure, low cost, and high performance. .

[0015]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, a method of manufacturing an acceleration sensor has a rectangular parallelepiped shape including an adhesive surface having a predetermined length. Preparing two piezoelectric element materials polarized in a direction perpendicular to the bonding surface, and bonding the two piezoelectric element materials to each other with an adhesive on the bonding surface such that the polarization directions are opposite to each other; A piezoelectric element having a first outer surface substantially perpendicular to the surface and having a predetermined length, and a second outer surface substantially parallel to the first outer surface and located on the opposite side of the first outer surface. A first bonding step of forming a block body, and a cut in the piezoelectric element block body along a length direction substantially parallel to the first outer surface, and a first inner portion substantially parallel to the first outer surface. A first inner surface substantially parallel to the first inner surface; a second inner surface substantially parallel to the first inner surface; The notch formed by the support portion supporting the second inner surface, the first inner surface, the second inner surface, and the support portion is formed between the first inner surface and the first outer surface. A cutting step for reducing the thickness of the first outer surface so that the thickness of the first outer surface is smaller than the thickness between the second inner surface and the second outer surface; Forming the third electrode on the first inner surface, forming the third electrode on the first inner surface, and filling the cutout between the first inner surface and the second inner surface with an adhesive. A bonding step, and a cutting step of cutting the piezoelectric element block along a plane perpendicular to the length direction of the bonding surface to form a plurality of vibration conversion units and a disposal unit including a support unit. And

In the electrode forming step, the first electrode and the second electrode are provided with one electrode on the first outer surface.
The groove may be formed by making a cut along the length direction substantially at the center of the outer surface.

[0017] The adhesive used in the second bonding step may be conductive.

The waste part formed in the cutting step is necessary in the manufacturing process, but is not used as a product.

The piezoelectric element material has a property of converting vibration into an electric signal, and is made of a piezoelectric ceramic element material or a single-crystal piezoelectric element material such as quartz.

According to this manufacturing method, since the first and second electrodes for extracting the electric signal generated by the vibration are parallel to the polarization direction of the piezoelectric element material, the influence of the pyroelectric effect due to the pyroelectric voltage is greatly reduced. It is possible to obtain a stable and high-performance acceleration sensor.

Further, since the two piezoelectric element materials are bonded so that the polarization directions are opposite to each other, by canceling out the pyroelectric effect, it is possible to further suppress the adverse effect due to the pyroelectric effect. Output sensitivity can be increased.

Further, since the structure is simple, the production is easy, the mass productivity is high, and the production cost can be kept low.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an acceleration sensor according to any one of the first to third aspects, wherein the first and second piezoelectric element blocks are formed of a first and a second element. It has two side surfaces that are substantially perpendicular to the outer surface and extend in the longitudinal direction.
A fourth electrode and a fifth electrode are provided on each of two side surfaces between the inner surface and the second outer surface.

According to this manufacturing method, since the electrically independent fourth and fifth electrodes are formed from the first to third electrodes, a capacitor formed between the fourth and fifth electrodes is used. The acceleration sensor can have a self-diagnosis function.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, the acceleration sensor has a predetermined thickness, a first outer surface substantially perpendicular to the thickness direction, and the first outer surface. A first inner surface substantially parallel to the surface, an adhesive surface substantially perpendicular to the first outer surface and the first inner surface, and substantially parallel to the first outer surface and the first inner surface. A first piezoelectric element comprising: two first piezoelectric element materials polarized in different directions; and an adhesive bonding the two first piezoelectric element materials to respective bonding surfaces such that the polarization directions are opposite to each other. Block body, predetermined thickness,
A second outer surface substantially perpendicular to the thickness direction;
A second inner surface substantially parallel to the outer surface, an adhesive surface substantially perpendicular to the second outer surface and the first inner surface, wherein the second outer surface and the second inner surface are substantially A second piezoelectric element including: two second piezoelectric element materials polarized in parallel directions; and an adhesive that bonds the two second piezoelectric element materials to respective bonding surfaces such that the polarization directions are opposite to each other. An element block body, first and second electrodes provided on the first outer surface and separated in the longitudinal direction at substantially the center thereof, and a third electrode provided on the first inner surface; A first inner surface of the first piezoelectric element block and a second inner surface;
Holding means for holding the piezoelectric element block body such that the second inner surface of the piezoelectric element block body is opposed to the piezoelectric element block body with a notch having a predetermined interval therebetween, wherein the predetermined position of the first piezoelectric element block body Is thinner than a predetermined thickness of the second piezoelectric element block.

The piezoelectric element material has a characteristic of converting vibration into an electric signal, and is made of a piezoelectric ceramic element material or a single-crystal piezoelectric element material such as quartz.

According to this configuration, since the first and second electrodes for extracting the electric signal generated by the vibration are parallel to the polarization direction of the piezoelectric element material, a pyroelectric voltage is generated on the first and second electrode surfaces. Instead, the effect of the pyroelectric effect due to the pyroelectric voltage can be significantly reduced.

Further, since the two first piezoelectric element materials are bonded so that the polarization directions are opposite to each other, the adverse effect due to the pyroelectric effect can be further suppressed by canceling the pyroelectric effect. Output sensitivity can be increased.

Further, since the structure is simple, manufacturing is easy, mass productivity is high, and manufacturing cost is low.

According to a sixth aspect of the present invention, in order to solve the above-mentioned problem, in the acceleration sensor according to the fifth aspect, the holding means includes a notch between the first inner surface and the second inner surface. The adhesive is provided so as to fill the portion.

[0031] The adhesive may be conductive.

According to this configuration, the output sensitivity can be increased by the effect of the weight of the second piezoelectric element block.

According to an eighth aspect of the present invention, in order to solve the above-mentioned problem, in the acceleration sensor according to the fifth aspect, the holding means is integrated with the first piezoelectric element block and the second piezoelectric element block. Characterized in that it is a holding portion formed on the substrate.

According to this configuration, the output sensitivity can be increased by the effect of the twist and the tuning fork.

According to a ninth aspect of the present invention, in order to solve the above-mentioned problem, in the acceleration sensor according to any one of the fifth to eighth aspects, the second piezoelectric element block is formed of a second outer surface and a second outer surface. A fourth electrode and a fourth electrode provided on the two side surfaces, the two side surfaces being substantially perpendicular to the inner surface and substantially perpendicular to the polarization direction of each second piezoelectric element material. It is characterized by having.

According to this configuration, since the electrically independent fourth and fifth electrodes are formed from the first to third electrodes, a capacitor formed between the fourth and fifth electrodes can be used. The acceleration sensor can have a self-diagnosis function.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An acceleration sensor according to the present invention has a predetermined thickness, a first outer surface substantially perpendicular to the thickness direction, and a first inner surface substantially parallel to the first outer surface. Two first piezoelectric elements having a first surface and an adhesive surface substantially perpendicular to the first outer surface and the first inner surface, and polarized in a direction substantially parallel to the first outer surface and the first inner surface. A first piezoelectric element block body including an element material and an adhesive for bonding the two first piezoelectric element materials at respective bonding surfaces such that the polarization directions are opposite to each other; A second substantially perpendicular to the thickness direction;
An outer surface, a second inner surface substantially parallel to the second outer surface, and an adhesive surface substantially perpendicular to the second outer surface and the first inner surface; (2) Two second piezoelectric element materials polarized in a direction substantially parallel to the inner surface, and an adhesive for bonding the two second piezoelectric element materials at respective bonding surfaces such that the polarization directions are opposite to each other. And a second piezoelectric element block including: a first and second electrode provided on the first outer surface, substantially at the center thereof and separated along the length direction, and provided on the first inner surface. The third electrode, the first internal surface of the first piezoelectric element block, and the second internal surface of the second piezoelectric element block are held so as to face each other with a cut portion having a predetermined interval therebetween. Holding means, wherein a predetermined thickness of the first piezoelectric element block is a predetermined thickness of the second piezoelectric element block. Thinner characterized than is.

The piezoelectric element material has a property of converting vibration into an electric signal, and is made of a piezoelectric ceramic element material or a single-crystal piezoelectric element material such as quartz.

Further, in the method of manufacturing an acceleration sensor according to the present invention, two piezoelectric element materials having a rectangular parallelepiped shape including a bonding surface having a predetermined length and polarized in a direction perpendicular to the bonding surface are prepared. A step, a first outer surface having a predetermined length substantially perpendicular to the bonding surface, wherein the two piezoelectric element materials are bonded to each other with an adhesive on the bonding surface such that the polarization directions are opposite to each other; A first bonding step of forming a piezoelectric element block having a second external surface substantially parallel to the first external surface and opposite to the first external surface; A cut is made along the length substantially parallel to the first outer surface, a first inner surface substantially parallel to the first outer surface, and a second inner surface substantially parallel to the first inner surface. A support for supporting the first inner surface and the second inner surface; a first inner surface; (2) The notch formed by the inner surface and the support portion is formed such that the thickness between the first inner surface and the first outer surface is greater than the thickness between the second inner surface and the second outer surface. A cutting step of shaving to be thin; a first and a second electrode separated along a length direction substantially at the center of the first outer surface; and a third and a third electrode formed on the first inner surface. An electrode forming step of providing electrodes; a second bonding step of filling a cut portion between the first inner surface and the second inner surface with an adhesive; and a piezoelectric element block perpendicular to the length direction of the bonding surface. A cutting step of forming a plurality of vibration conversion units by cutting the surface and a disposal unit including a support unit;

Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following examples.

[0041]

FIG. 1 is a perspective view of a first embodiment of a vibration converter of an acceleration sensor according to the present invention. In the figure,
The vibration conversion unit 30 includes two first piezoelectric element materials 31a and 3
1b is bonded at its bonding surface 32 by an adhesive.
Piezoelectric element block body 31 and two second piezoelectric element materials 33
a and 33b are constituted by a second piezoelectric element block 33 bonded at its bonding surface 34 by an adhesive. The adhesive used here may be conductive. The first piezoelectric element block body 31 has a predetermined thickness, a first outer surface 35 substantially perpendicular to the thickness direction, and a first inner surface 36 substantially parallel to the first outer surface 35. Have. The second piezoelectric element block 33 has a predetermined thickness, a second outer surface 37 substantially perpendicular to the thickness direction,
A second inner surface 38 substantially parallel to the second outer surface 37. The thickness of the first piezoelectric element block body 31 is
The thickness is smaller than the thickness of the second piezoelectric element block 33.

The first piezoelectric element block 31 and the second piezoelectric element block 33 are formed of a piezoelectric element such as ceramics or a single crystal piezoelectric element such as quartz. As shown by arrows D3 to D6 in FIG. 1, the first piezoelectric element block 31 and the second piezoelectric element block 33 formed of a piezoelectric element material such as ceramics have a first outer surface 35 and a first inner surface. 36, the second outer surface 37 and the second inner surface 38 are polarized in a direction substantially parallel to them. Two first piezoelectric element materials 31a forming the first piezoelectric element block 31 and the second piezoelectric element block 33
And 31b and two second piezoelectric element materials 33a and 33b
Are polarized in different directions. Each 2
If the two piezoelectric elements have different polarization directions,
The polarities may be reversed in the directions shown in the figure. When the first piezoelectric element block 31 and the second piezoelectric element block 33 are made of a single-crystal piezoelectric element material such as quartz, the first outer surface 35 and the first inner surface 36, the second outer surface 37, and the second 2 has an electrical axis in a direction substantially parallel to the inner surface 38.

On the first outer surface 35 of the first piezoelectric element block 31, along the bonding surface 32 of the two first piezoelectric element materials 31a and 31b, the first electrode 3 separated substantially at the center thereof.
9 and a second electrode 40 are provided, and a third electrode 41 is provided entirely on the first inner surface 36. In this embodiment, the first to third electrodes 39 to 41 are formed by plating or vapor deposition. In the present embodiment, the first and second electrodes 39
And the first piezoelectric element block 3
The two first piezoelectric element materials 3 are provided substantially at the center of the first outer surface 35.
Although the groove 42 is formed along the bonding surface 32 of 1a and 31b, the groove may not be provided as long as the first and second electrodes 39 and 40 are separated.

The electrode 43 is also formed on the entire surface of the second inner surface 38 of the second piezoelectric element block 33 in this embodiment. The electrode 43 is provided in a manufacturing process of an acceleration sensor described later, and is not actually required.

The first piezoelectric element block 31 and the second piezoelectric element block 33 are bonded with an adhesive 44 such that the first inner surface 36 and the second inner surface 38 face each other. The third electrode 41 may be formed by bonding the first piezoelectric element block 31 and the second piezoelectric element block 33 with a conductive adhesive, in addition to the above-described plating or the like.

Capacitors are formed between the first and third electrodes 39 and 41 and between the second and third electrodes 40 and 41, respectively. First and second electrodes 39 provided on the first piezoelectric element block body 31
And 40 are connected to an output terminal (not shown), and the acceleration applied to the first piezoelectric element block 31 is extracted as electric signals from the first and second electrodes 39 and 40.
The first piezoelectric element block 31 functions as a detection unit for detecting acceleration, but the electric signal is detected from a plane parallel to the polarization direction of the piezoelectric element material forming the first piezoelectric element block 31. An accurate value hardly affected by the pyroelectric effect can be detected.

The second piezoelectric element block 33 is thicker than the first piezoelectric element block 31 and is disposed on the first piezoelectric element block 31.
1 serves as a weight for efficiently detecting acceleration. Assuming that the mass of the weight is m and the acceleration applied to the acceleration sensor is G, a force of F = mG acts on the acceleration sensor. Therefore, in order to increase the acceleration detection sensitivity of the acceleration sensor, the second piezoelectric element block 3 acting as a weight is required.
3 may be increased. Here, the second piezoelectric element block 33 is formed of a piezoelectric element material such as ceramics, but the piezoelectric element material such as ceramics is effective because of its high density.

The acceleration is detected by utilizing the force of the weight and detecting the electromotive force caused by the sliding effect of the first piezoelectric element block 31. Here, between the first and third electrodes 39 and 41 and the second and third electrodes 39 and 41 via the third electrode 41.
Two capacitors formed between the electrodes 40 and 41 are connected in series.

In this embodiment, as shown by D3 to D6 in FIG. 1, two first piezoelectric element members 31a and 31b constituting the first piezoelectric element block 31 and the second piezoelectric element block 33 are provided. Although the polarization directions of the two second piezoelectric element materials 33a and 33b are polarized in different directions, the polarization directions of the two piezoelectric element materials may be the same as each other. Here, an electric signal is also taken out from the third electrode 41. In that case, the first and third electrodes 3
That is, two capacitors formed between 9 and 41 and between the second and third electrodes 40 and 41 are connected in parallel.

The two first piezoelectric element materials 3 forming the first piezoelectric element block 31 and the second piezoelectric element block 33
1a and 31b and two second piezoelectric element materials 33a and 3
When the bonding surfaces 32 and 34 of 3b are bonded with a conductive adhesive, respectively, the bonding surfaces 32 and 34 are provided with electrodes 47 and 48, respectively. For example, an electric signal from the third electrode may be extracted via the electrode 47 provided on the bonding surface 32. Also, the first
When the third electrode of the piezoelectric element block is formed of a conductive adhesive, the third electrode is formed via the electrode 48 provided on the bonding surface 34.
An electrical signal from the electrode may be extracted. Further, after bonding the respective piezoelectric element materials, the electrodes 47 and 48 can be used to polarize the piezoelectric element block.

Next, the vibration conversion unit 3 thus configured
A method for manufacturing an acceleration sensor having 0 is described.

As shown in FIG. 2, first, a predetermined length L
Having a rectangular parallelepiped shape including an adhesive surface 52 having
Two piezoelectric element materials 51a and 51b polarized in a direction perpendicular to are prepared, and the piezoelectric element materials 51a and 51b are
A piezoelectric element block having a first outer surface 55 and a second outer surface 57 is bonded by an adhesive on the bonding surface 52 so that the polarization directions are opposite to each other as shown in D7 and D8 in FIG. The body 51 is formed. The adhesive used here may be conductive.

After the two piezoelectric element members 51a and 51b are fixed on the bonding surface 52 with a conductive adhesive,
2 by a known method using the electrode formed in FIG.
As shown in 7 and D8, they may be polarized so that they are in opposite directions.

The bonded piezoelectric element block body 51 is
As shown in (1), a portion shown by a broken line is cut along the length direction in parallel with the first outer surface 55, and the first outer surface 55 is cut.
A first inner surface 56 and a second inner surface 58 substantially parallel to the outer surface 55 and the second outer surface 57 are formed. At this time,
A part of the piezoelectric element block body 51 is left so that the piezoelectric element block body 51 has a support portion 69 that supports the first internal surface 56 and the second internal surface 58 so as to face each other across a cut portion having a predetermined interval. Make a cut. The thickness between the second outer surface 57 and the second inner surface 58 is the thickness between the second inner surface 58 and the first inner surface 56, and the thickness between the first outer surface 55 and the first inner surface 56. It is formed thicker than the space between them.

Next, as shown in FIG. 4, electrodes are provided on the first outer surface 55, the first inner surface 56, and the second inner surface 58 by plating. In this plating process, electrodes are formed on surfaces other than the first outer surface 55, the first inner surface 56, and the second inner surface 58, but unnecessary electrodes are removed by polishing or the like.

The first inner surface 56 and the second inner surface 58
An adhesive 64 or the like is injected into the cut portion between the holes to fill the cut portion. This adhesive may be a conductive adhesive.

As shown in FIG. 5, a groove 62 is formed in the electrode provided on the first outer surface 55 so as to extend along the bonding surface of the piezoelectric element block body. Is divided into two in the length direction, and the first electrode 59 and the second electrode 60
To form Although the groove 62 is formed here,
The first electrode 59 and the second electrode 60 may be individually formed by plating or the like.

The piezoelectric element block 51 on which the electrodes are formed as described above is cut along a plane perpendicular to the length direction of the bonding surface 52 as shown by a broken line in FIG. . Here, the part 65 including the support part 69, which is located on the leftmost side in FIG.

Although the method of manufacturing the vibration conversion section has been described with reference to FIGS. 2 to 6, as shown in FIG.
It may be manufactured using the piezoelectric element materials for the rows or more. In this case, mass productivity can be further improved.

Further, at the time of the plating process, two side surfaces which are perpendicular to the first and second outer surfaces 55 and 57 and extend in the longitudinal direction are respectively provided on the side closer to the second outer surface 57 along the longitudinal direction. If the metal is formed by the above process, a vibration conversion unit having the fourth and fifth electrodes 45 and 46 is manufactured as shown in FIG. The fourth and fifth electrodes 45 and 46 are electrically independent of the other electrodes.

Output terminals are installed on the fourth and fifth electrodes 45 and 46, and a voltage applied from an external oscillator (not shown) is input to apply vibration to the vibration conversion unit, and a potential generated by the vibration is generated. To the first and second electrodes 39 and 40
, A self-diagnosis function can be given to the acceleration sensor.

The vibration conversion unit 30 includes the first and second electrodes 39
And 40 are electrically connected to a printed circuit board or the like via a not-shown output terminal by a conductive adhesive, soldering, wire bonding, or the like to take out an electric signal,
An acceleration sensor is configured as in the conventional example.

[0063]

FIG. 9 is a perspective view of a second embodiment of the vibration converter of the acceleration sensor according to the present invention. In the figure,
1 and 8 are denoted by the same reference numerals.

The difference between the vibration converting section 70 and the vibration converting section 30 is that the cut between the first piezoelectric element block 31 and the second piezoelectric element block 33 is formed in the first internal surface 36 and the second internal surface 38. It is not included in the whole. The vibration conversion section has a holding section 71 and has a U-shaped cross section.

An adhesive or the like 44 may be embedded and fixed in the cut portion between the first inner surface and the second inner surface as shown in FIG. 9, as shown in FIG. Need not be fixed with an adhesive. If the first internal surface and the second internal surface are not fixed by an adhesive, the sensitivity may be degraded due to a decrease in the weight effect of the second piezoelectric element block. Since the element block has a U-shape supported by the holding portion 71, the sensitivity can be prevented from deteriorating due to the effect of the torsion and the tuning fork.

With such a configuration, since the fixing with the adhesive 44 becomes unnecessary, the production is further facilitated, and it is suitable for mass production.

Further, since the vibration conversion section 70 of this embodiment has the holding section 71, the structural strength at the time of processing is increased,
Manufacturing becomes easy.

The vibration conversion unit shown in FIGS.
And the fifth and fourth electrodes 45 and 46 have a self-diagnosis function. However, these fourth and fifth electrodes 45 and 46 may be provided as needed, and may not be provided. .

[0069]

According to the method of manufacturing the acceleration sensor according to the present invention, the first and second electrodes for extracting the electric signal generated by the vibration are parallel to the polarization direction of the piezoelectric element material. It is possible to obtain a stable and high-performance acceleration sensor that does not occur on the first and second electrode surfaces and greatly reduces the influence of the pyroelectric effect due to the pyroelectric voltage. Further, since the two piezoelectric element materials are bonded so that the polarization directions are opposite to each other, by canceling the pyroelectric effect, the adverse effect of the pyroelectric effect can be further suppressed, and the output sensitivity can be reduced. Can be enhanced.

Further, since the structure is simple, the production is easy, the mass productivity is high, and the production cost is kept low.

According to the acceleration sensor of the present invention, since the first and second electrodes for extracting the electric signal generated by the vibration are parallel to the polarization direction of the piezoelectric element material, the pyroelectric voltage is reduced to the first and the second. It does not occur on the electrode surface and the effect of the pyroelectric effect due to the pyroelectric voltage can be greatly reduced. In addition, since the two first piezoelectric element materials are bonded so that the polarization directions are opposite to each other, by canceling the pyroelectric effect, it is possible to further suppress the adverse effect due to the pyroelectric effect, Sensitivity can be increased.

Furthermore, since the structure is simple, the production is easy, the mass productivity is high, and the production cost is kept low.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of an acceleration sensor according to the present invention.

FIG. 2 is a perspective view of a piezoelectric element block formed in a first bonding step of manufacturing the acceleration sensor shown in FIG.

FIG. 3 is a perspective view of a piezoelectric element block used in a cutting step for manufacturing the acceleration sensor shown in FIG. 1;

FIG. 4 is a perspective view of a piezoelectric element block used in an electrode forming step for manufacturing the acceleration sensor shown in FIG.

5 is a perspective view of a piezoelectric element block used in an electrode forming step for manufacturing the acceleration sensor shown in FIG.

FIG. 6 is a perspective view of a piezoelectric element block used in a cutting step for manufacturing the acceleration sensor shown in FIG. 1;

7 is a perspective view of a piezoelectric element block used for manufacturing the acceleration sensor shown in FIG.

FIG. 8 is a perspective view of another embodiment of the acceleration sensor shown in FIG.

FIG. 9 is a perspective view of a second embodiment of the acceleration sensor according to the present invention.

FIG. 10 is a perspective view of another embodiment of the acceleration sensor shown in FIG.

FIG. 11 is an elevational sectional view of a conventional acceleration sensor.

FIG. 12 is an equivalent connection diagram of an exchange unit of the conventional acceleration sensor shown in FIG.

FIG. 13 is a diagram for explaining frequency characteristics of a general acceleration sensor.

[Explanation of symbols]

 30, 70 acceleration sensor (vibration converter) 31 first piezoelectric element block 32, 34, 52 bonding surface 33 second piezoelectric element block 35, 55 first outer surface 36, 56 first inner surface 37, 57 second Outer surface 38, 58 Second inner surface 39 First electrode 40 Second electrode 41 Third electrode 42, 62 Groove 44, 64 Adhesive 45 Fourth electrode 46 Fifth electrode 51 Piezoelectric element block

Claims (9)

[Claims] A step of preparing two piezoelectric element materials having a rectangular parallelepiped shape including an adhesive surface having a predetermined length and polarized in a direction perpendicular to the adhesive surface; A first outer surface substantially perpendicular to the adhesive surface and having the predetermined length, the first outer surface being bonded to the bonding surface with an adhesive such that the polarization directions are opposite to each other; A second external surface substantially parallel to the first external surface and opposite to the first external surface, a first bonding step of forming a piezoelectric element block body, and the first external surface on the piezoelectric element block body. Cutting along the length direction substantially parallel to the first inner surface substantially parallel to the first outer surface; and a second inner surface substantially parallel to the first inner surface. A supporting portion for supporting the first inner surface and the second inner surface; Surface, the second inner surface, and the cut portion formed by the support portion, the thickness between the first inner surface and the first outer surface is the second inner surface, A cutting step of cutting to a thickness smaller than a thickness between the first outer surface and the first outer surface, the first and the outer surfaces being separated along the length direction substantially at a center of the first outer surface. A second electrode;
An electrode forming step of providing a third electrode on an inner surface; a second bonding step of filling a cut portion between the first inner surface and the second inner surface with an adhesive; A method for manufacturing an acceleration sensor, comprising: a cutting step of forming a plurality of vibration conversion units by cutting the surface of the bonding surface perpendicular to the length direction to form a plurality of vibration conversion units and a disposal unit including the support unit. 2. In the electrode forming step, the first and second electrodes on the first external surface are provided at a substantially center of the first external surface after one electrode is provided on the first external surface. The method according to claim 1, wherein the groove is formed by making a cut along the length direction to form a groove. 3. The method according to claim 1, wherein the adhesive used in the second bonding step is conductive. 4. The piezoelectric element block body has two side surfaces substantially perpendicular to the first and second outer surfaces and extending in the length direction, and in the electrode forming step,
4. The acceleration sensor according to claim 1, wherein a fourth electrode and a fifth electrode are provided on each of the two side surfaces between the second inner surface and the second outer surface. 5. Method. 5. A predetermined thickness, a first outer surface substantially perpendicular to the thickness direction, a first inner surface substantially parallel to the first outer surface, the first outer surface and the first outer surface. Two first piezoelectric element materials having an adhesive surface substantially perpendicular to the first inner surface and polarized in a direction substantially parallel to the first outer surface and the first inner surface; A first piezoelectric element block body including: an adhesive for bonding two first piezoelectric element materials at the respective bonding surfaces so that the polarization directions are opposite to each other; a predetermined thickness, substantially in the thickness direction. A second outer surface substantially perpendicular to the second outer surface, a second inner surface substantially parallel to the second outer surface,
Two second polarizers having a second outer surface and an adhesive surface substantially perpendicular to the first inner surface, and polarized in a direction substantially parallel to the second outer surface and the second inner surface. A second piezoelectric element block body including: a piezoelectric element material; and an adhesive for bonding the two second piezoelectric element materials on the respective bonding surfaces so that the polarization directions are opposite to each other; First and second electrodes provided on the surface at substantially the center thereof and separated along the length direction; a third electrode provided on the first internal surface; and the first piezoelectric element block Holding means for holding the first internal surface of the body and the second internal surface of the second piezoelectric element block body so as to face each other across a cut portion having a predetermined interval. Wherein the predetermined thickness of the first piezoelectric element block is the second piezoelectric element block. An acceleration sensor having a thickness smaller than the predetermined thickness. 6. The apparatus according to claim 5, wherein the holding means is an adhesive provided so as to fill the cut portion between the first inner surface and the second inner surface. Acceleration sensor. 7. The acceleration sensor according to claim 6, wherein the adhesive is conductive. 8. The acceleration sensor according to claim 5, wherein the holding unit is a holding unit formed integrally with the first piezoelectric element block and the second piezoelectric element block. 9. The two piezoelectric element block bodies are substantially perpendicular to the second outer surface and the second inner surface and substantially perpendicular to a polarization direction of each of the second piezoelectric element materials. 9. The semiconductor device according to claim 5, further comprising: a fourth electrode having a side surface, and fourth and fifth electrodes provided on the two side surfaces.
The acceleration sensor according to any one of the above.