JP2001074767A - Accelerometer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superior accelerometer whose structure is comparatively simple, which is low-cost and whose performance is high. SOLUTION: An acceleration detecting part 31 is provided in such a way that it is provided with a first plane 33a on which a first electrode 35a for detection is formed, that it is provided with a second plane 33b on which a second electrode 35b, for detection, having a prescribed area is formed and that it is composed of a piezoelectric element material such as a sheetlike piezoelectric ceramic or the like which is polarized in a direction which is substantially parallel to the first and second planes 33a, 33b. A plumb hob part 41 is provided with an electrode 45a, for continuity, wherein a bottom face 34a whose shape and area are nearly equal to those of the first plane 33a in the acceleration detecting part 31 is provided and a prescribed mass is provided. The electrode 45a, for continuity, in the plumb hob part 41 is bonded to the first electrode 35a, for detection, in the acceleration detecting part 31 by using a conductive adhesive or the like so as to be connected electrically to each other, and it converts a vibration into an electric signal so as to be output.

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 in 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. While being electrically connected, 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, and electrically connected to and fixed to the support plate 11 by resistance welding, etc. Converter 10, printed circuit boards 13 and 1
And a case 18 for accommodating the same 7.

[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. 12, in a conventional acceleration sensor 1, a pair of piezoelectric elements 3 of a vibration transducer 10 are electrically connected in parallel to each other via electrodes 5a and 5b. I have. The electrode 5a is electrically connected to an external oscillator 19, and the external oscillator 19
The diaphragm 7 is vibrated by applying a predetermined voltage from. This 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.

FIG. 13 shows an example of a frequency characteristic at a constant acceleration with respect to the vibration of the acceleration sensor. As shown in the figure, the Q has a high Q near the resonance point f ₀ , but is flat in the middle and low frequency regions. Show characteristics. In general,
Depending on the purpose of use of the acceleration sensor, the flat part or the resonance point f
Select and use the vibration output near ₀ .

[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 diaphragm 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 are combined to form an integrated product, so that the sensitivity and characteristics are likely to vary, and
There has been a problem that temperature characteristics are likely to deteriorate.

Further, in the conventional acceleration sensor 1, since the polarization direction in the piezoelectric element 3 is perpendicular to the element plane, pyroelectricity is generated on the plane on which the electrodes 5a and 5b are provided. In order to cancel this pyroelectric effect,
The electrodes 5a are arranged such that the polarization direction in the piezoelectric element 3 is reversed.
And 5b are electrically connected in series or in parallel, respectively, but still cannot completely cancel the pyroelectric effect. Particularly, when an acceleration sensor is used at an extremely low frequency, the operating point of the electric circuit is adversely affected. There was a problem of giving.

Further, in the conventional acceleration sensor 1,
Since a plurality of piezoelectric elements are required in order to suppress the adverse effect of the pyroelectric effect, there is a problem that the structure is complicated, the production is troublesome, and the cost is increased.

Therefore, the present invention has been made in view of the above 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, there is provided an acceleration sensor comprising:
It has a first plane on which a detection electrode is formed, and a second plane on a side opposite to the first plane, on which a second detection electrode is formed, and substantially corresponds to the first and second planes. An acceleration detecting section made of a plate-shaped piezoelectric element material polarized in a parallel direction; and a first plane on which a conduction electrode having a shape and an area substantially equal to the surface of the first detection electrode are formed. A bottom surface having substantially the same shape and area, and a weight portion having a predetermined mass, and a bottom surface of the weight portion and the first plane are arranged so as to face each other,
The conduction electrode is electrically connected to the first detection electrode, and detects a potential difference between the first and second detection electrodes.

According to this configuration, since the first and second detection electrodes of the acceleration detection section are arranged at positions parallel to the polarization direction of the piezoelectric element material of the acceleration detection section, the first and second detection electrodes are disposed on the surface of the front end in the polarization direction. The influence of the generated pyroelectricity on the electrodes can be reduced, and a stable, high-performance acceleration sensor can be obtained. In addition, since the structure is simple, mass productivity is high and the manufacturing cost can be kept low.

The piezoelectric element material has a property of converting vibration into an electric signal, and is made of piezoelectric ceramics or a single-crystal piezoelectric element material such as quartz. When using quartz or the like, if the first and second detection electrodes of the acceleration detection unit are arranged at positions parallel to the electric axis of the piezoelectric element material of the acceleration detection unit, the trouble of polarizing the piezoelectric element material can be eliminated. Can also
The manufacturing process can be simplified, and the degree of freedom of the configuration increases.

[0018] In the acceleration sensor according to claim 1,
The first detection electrode and the conduction electrode may be bonded by a conductive adhesive. Further, in the above-described acceleration sensor, the weight portion may have a substantially same linear expansion coefficient as the piezoelectric element material.

According to a fourth aspect of the present invention, there is provided a method for manufacturing an acceleration sensor, comprising the steps of:
A first preparation step of preparing a strip-shaped piezoelectric element material having a second plane opposite to the first plane and polarized in a direction substantially parallel to the first and second planes; And a first electrode for forming a first detection electrode on the first plane of the piezoelectric element material prepared in the first preparation step and a second detection electrode on the second plane A forming step, a second preparing step of preparing a weight having a shape and area substantially equal to the first plane, and a predetermined mass, and the second forming step formed in the first electrode forming step. A second electrode forming step of forming a conducting electrode having substantially the same shape and area as the surface of the detection electrode on the bottom surface of the weight prepared in the second preparing step; Conductive bonding between the first detection electrode and the first detection electrode Forming an acceleration detection element block by bonding together, and cutting the acceleration detection element block formed in the block forming step along a plane substantially orthogonal to the length direction to form a plurality of acceleration detection elements. Forming an acceleration detecting element.

According to this method, the first and second detection electrodes are arranged at positions parallel to the polarization direction of the piezoelectric element material, so that the electrodes are adversely affected by pyroelectricity generated on the front surface in the polarization direction. And a stable, high-performance acceleration sensor can be manufactured. Further, since the structure is simple, the work is easy, the mass productivity is high, and the manufacturing cost can be kept low.

The piezoelectric element material has a property of converting vibration into an electric signal, and is made of piezoelectric ceramics or a single-crystal piezoelectric element material such as quartz. In the case of using quartz or the like, if the first and second detection electrodes are arranged at positions parallel to the electric axis of the piezoelectric element material, the trouble of polarizing the piezoelectric element material can be omitted, and the manufacturing process can be simplified. As much as possible, the degree of freedom in configuration is expanded.

In the above-described method for manufacturing an acceleration sensor,
The first electrode forming step may include a step of forming the first and second detection electrodes by plating or vapor deposition. In the method for manufacturing an acceleration sensor described above,
The second electrode forming step may include a step of forming the conductive electrode by plating or vapor deposition. In the above-described method of manufacturing an acceleration sensor, the weight prepared in the second preparation step may have substantially the same linear expansion coefficient as the piezoelectric element material prepared in the first preparation step. good.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An acceleration sensor according to the present invention has a first plane on which a first detection electrode is formed, and a second plane on which a second detection electrode is formed on the side opposite to the first plane. And an acceleration detecting section made of a plate-shaped piezoelectric element material polarized in a direction substantially parallel to the first and second planes, and a shape substantially equal to the surface of the first detecting electrode. And a conductive electrode having an area is formed.
A bottom surface having substantially the same shape and area as the plane and a weight having a predetermined mass are provided. In this acceleration sensor, the bottom surface of the weight portion and the first plane are:
The conductive electrode is disposed so as to face the first electrode.
It is electrically connected to the detection electrode.

According to the acceleration sensor configured as described above, since the first and second detection electrodes of the acceleration detecting section are arranged at positions parallel to the polarization direction of the piezoelectric element material of the acceleration detecting section. It is possible to reduce the adverse effect of pyroelectricity generated on the surface of the tip in the polarization direction to the electrodes, and to obtain a stable and high-performance acceleration sensor. Also, since the structure is simple,
High mass productivity and low production cost.

The piezoelectric element material has a characteristic of converting vibration into an electric signal, and is made of piezoelectric ceramics. Alternatively, as another embodiment, the piezoelectric element material of the acceleration detecting section may be composed of a single-crystal piezoelectric element material such as quartz, and in this case, the piezoelectric element materials of the acceleration detecting section are the first and second piezoelectric elements. It has an electrical axis in a direction substantially parallel to the plane.

According to this configuration, if the first and second detection electrodes of the acceleration detecting section are arranged at positions parallel to the electric axis of the piezoelectric element material of the acceleration detecting section, the time required to polarize the piezoelectric element material is reduced. This can be omitted, the manufacturing process can be simplified, and the degree of freedom of the configuration can be increased.

Further, a method of manufacturing an acceleration sensor according to the present invention has (a) a first plane and a second plane opposite to the first plane, and the first and second planes are substantially identical to each other. A first preparation step of preparing a strip-shaped piezoelectric element material polarized in a direction parallel to the first direction; and (b) on the first plane of the piezoelectric element material prepared in the first preparation step, A first electrode forming step of forming a first detection electrode and a second detection electrode on the second plane; (c)
A second preparation step of preparing a weight having a bottom surface having substantially the same shape and area as the first plane and a predetermined mass; and (d) the first electrode formed in the first electrode forming step. A second electrode forming step of forming a conductive electrode having a shape and an area substantially equal to the surface of the detection electrode on the bottom surface of the weight prepared in the second preparing step; (e) the conductive electrode A step of forming an acceleration detection element block by bonding the first detection electrode and the first detection electrode with a conductive adhesive; and (f) setting the acceleration detection element block formed in the block formation step to a length. Cut in a plane substantially perpendicular to the vertical direction,
Forming an acceleration detection element for forming a plurality of acceleration detection elements.

According to this method of manufacturing an acceleration sensor, the first and second detection electrodes of the acceleration detection section are arranged at positions parallel to the polarization direction of the piezoelectric element material of the acceleration detection section. It is possible to reduce the adverse effect of pyroelectricity generated on the surface of the electrode, and to manufacture a stable and high-performance acceleration sensor. Further, since the structure is simple, the work is easy, the mass productivity is high, and the manufacturing cost can be kept low.

[0029]

FIG. 1 is a perspective view of a first embodiment of a vibration converter of an acceleration sensor according to the present invention. As shown in the figure, the vibration converter 30 of the present embodiment includes an acceleration detector 3
1 and a weight 41. The weight part 41 is
The acceleration detection unit 31 is disposed above the acceleration detection unit 31 and serves as a weight for the acceleration detection unit 31 to efficiently detect the acceleration applied to the acceleration sensor according to the present invention. In all the drawings, similar components are denoted by the same reference symbols and symbols.

The acceleration detector 31 has a predetermined thickness and a first
A plane 33a and a second plane 33 opposite to the first plane 33a
and a piezoelectric element 33 made of a plate-shaped piezoelectric element material having b. The piezoelectric element material has a characteristic of converting vibration into an electric signal. The acceleration detection unit 31 further includes a first detection electrode 35a having a predetermined area formed on the first plane 33a of the piezoelectric element 33 and a predetermined area formed on the second plane 33b of the piezoelectric element 33. Second detection electrode 35b having
And In this embodiment, the first and second planes 33
The shapes of a and 33b are rectangular, but are not limited thereto, and may be any shape.

In this embodiment, the first and second detection electrodes 35a and 35b are formed by plating or vapor deposition. The first detection electrode 35a is a piezoelectric element 33
Is formed over one surface of the first plane 33a. On the other hand, as shown in the bottom view of the vibration transducer 30 in FIG. 2, the second detection electrode 35b is located slightly inside by a width d from both ends 33c and 33d of the second plane 33b of the piezoelectric element 33. It is formed as follows. The reason why the second detection electrode 35b is formed inside the end of the second plane 33b of the piezoelectric element 33 is that the second detection electrode 35b will be described later when a vibration converter 30 described later is mounted on a printed circuit board or the like. This is for preventing a short circuit, a leak, and the like between the conductive wire led from the first detection electrode 35a. Therefore, in another embodiment, if the second detection electrode 35b and the conducting wire are configured to be insulated by an insulating member or the like, the second detection electrode 35b is provided at both ends of the second plane 33b of the piezoelectric element 33. 33c
And up to 33d.

In this embodiment, the piezoelectric element 33 of the acceleration detecting section 31 is made of piezoelectric ceramics, and is indicated by an arrow D3 in FIG.
As shown by the first plane 33a and the second plane 33b
Polarized in a direction substantially parallel to. The polarization direction may be parallel to the first and second planes 33a and 33b, and the direction is not particularly limited.

In another embodiment, the piezoelectric element 33 of the acceleration detecting section 31 may be a single-crystal piezoelectric element such as quartz, and the electric axis of the single-crystal piezoelectric element is the first axis of the piezoelectric element 33. And a direction substantially parallel to the second planes 33a and 33b. In this case, the piezoelectric element 33
This eliminates the need for polarization, which further simplifies the manufacturing process and increases the degree of freedom in configuration.

The weight portion 41 has a bottom surface 43a having substantially the same shape and area as the first plane 33a of the acceleration detecting portion 31, and a weight 43 having a predetermined mass. In this embodiment, the weight 43 is a rectangular parallelepiped, but is not limited to this. The weight 43 is made of a metal body or a piezoelectric element material, and preferably has substantially the same linear expansion coefficient as the piezoelectric element material of the piezoelectric element 33. Assuming that the mass of the weight 43 is m and the acceleration applied to the acceleration sensor is G, a force of F = mG acts on the acceleration sensor. Therefore, to increase the acceleration detection sensitivity of the acceleration sensor, the mass m of the weight 43 may be increased.

The weight portion 41 is formed integrally with a first conducting electrode 45a formed so as to cover the entire bottom surface 43a of the weight 43 and two opposing ends of the first conducting electrode 45a. And a second conduction electrode 45b formed to extend over both side surfaces and the top surface of the second conduction electrode 43.
First and second conduction electrodes 45a and 45 of weight 41
5b is formed by plating or vapor deposition. The first conduction electrode 45a thus formed has substantially the same shape and area as the first detection electrode 35a of the acceleration detector 31. On the other hand, the second conduction electrode 45b does not need to be formed so as to particularly extend on the surface of the weight portion 41, as long as an electric signal can be extracted from the first conduction electrode 45a. That is, the first conduction electrode 45b is replaced with the first conduction electrode 45b.
It may be electrically connected directly to the terminal on the circuit board by soldering or wire bonding from the conduction electrode 45a. In another embodiment, the second conduction electrode 45b may be formed so as to cover the entire periphery of the weight 41. Also in this case, it is necessary to form the first detection electrode 35a so as not to be short-circuited with the conductor led from the second conduction electrode 45b.

The first plane 33a of the piezoelectric element 33 of the acceleration detector 31 and the bottom surface 43a of the weight 41 are arranged so as to face each other.
a and the first conducting electrode 45a of the weight portion 41 are bonded by a conductive adhesive or the like.

In the acceleration sensor configured as described above,
The acceleration detector 31 detects the force F due to the weight 43 of the weight 41.
, The electromotive force due to the sliding effect of the piezoelectric element 33 is detected via the first detection electrode 35a and the second detection electrode 35b. The first detection electrode 35a of the acceleration detector 31 is electrically connected to the second conduction electrode 45b of the weight 41 via the first conduction electrode 45a of the weight 41. As described above, the vibration converter 30 of the acceleration sensor according to the present embodiment extracts the electric signal generated by the acceleration applied to the acceleration sensor via the second conduction electrode 45b of the weight 41.

As described above, in the acceleration sensor of this embodiment,
Since the first and second detection electrodes 35a and 35b for detecting an electric signal are formed on a plane parallel to the polarization direction D3 of the piezoelectric element 33, the first and second detection electrodes 35a and 35b are generated on the surface of the polarization direction D3 in the direction of the arrow. An electric signal can be detected almost without being affected by pyroelectricity, and a stable and high-performance acceleration sensor can be obtained.

FIG. 3 shows a printed circuit board 51 on which a circuit pattern is formed by using the vibration transducer 30 of the acceleration sensor of this embodiment.
This is an example of the case where the above is implemented. According to the figure, for example, an adhesive layer 5 using both a conductive adhesive and an epoxy resin adhesive is used.
2, the second detection electrode 35b of the acceleration detection unit 31 of the vibration converter 30 is conductively fixed to the circuit pattern of the printed board 51 via the second detection electrode of the acceleration detection unit 31 of the vibration converter 30. 35b is electrically connected to the terminal 53 of the circuit pattern formed on the printed board 51. Further, the second conducting electrode 45b of the weight portion 41 of the vibration transducer 30 is electrically connected to the terminal 55 of the circuit pattern formed on the printed board 51 by using the conductive adhesive 56 as shown in FIG. Connected to. As another embodiment, electrical connection may be made by soldering or wire bonding.

The vibration transducer 30 of the acceleration sensor configured as described above is fixed to a printed circuit board as one of electric circuit components with an adhesive or the like, similarly to the conventional acceleration sensor 1 shown in FIG. By electrically connecting the second detection electrode 35b of the acceleration detection section 31 and the second conduction electrode 45b of the weight section 41 to terminals on a printed circuit board, an acceleration sensor (not shown) is formed. .

Hereinafter, the steps of manufacturing the vibration transducer 30 of this embodiment will be described in detail with reference to FIGS.

First, a rectangular parallelepiped piezoelectric element member 61 made of a piezoelectric element such as a piezoelectric ceramic element or a single-crystal piezoelectric element such as quartz is prepared. As shown in FIG. 4, a plurality of piezoelectric element blocks 63 obtained by cutting the piezoelectric element member 61 into a strip having a predetermined thickness W1, a predetermined length L, and a predetermined height H are formed. prepare.

In this embodiment, each piezoelectric element block 63
Are polarized in a direction substantially parallel to both surfaces 63a and 63b and substantially perpendicular to the length direction of the piezoelectric element block 63, as shown by an arrow D3.
When the piezoelectric element block 63 is a single-crystal piezoelectric element material, its electric axis is substantially parallel to the two surfaces 63a and 63b and substantially perpendicular to the length direction of the piezoelectric element block 63. It is cut out in the direction.

Next, as shown in FIG. 5, on one flat surface 63a of each cut piezoelectric element block 63,
A first detection electrode layer 65a having a predetermined area;
A second detection electrode layer 65b having a predetermined area is formed on the other flat surface 63b opposite to 3a. The first detection electrode layer 65a and the second detection electrode layer 65b are formed by plating or vapor deposition. Here, the second detection electrode layer 65b is formed so as to be located slightly inside by a width d from both ends in the length direction of the piezoelectric element block 63.

Next, a rectangular parallelepiped weight member 71 made of metal or a piezoelectric element material is prepared. As shown in FIG.
The weight member 71 is cut out into a strip having a predetermined thickness W2 and a length L and a height H substantially the same as those of the piezoelectric element block 63 to prepare a plurality of weight blocks 73.

Next, as shown in FIG. 7, a first conductive electrode layer 75a formed so as to cover the entire bottom surface 73a of each weight block 73, and is electrically connected to the first conductive electrode 75a. The second conductive electrode 75b. In this embodiment, the outside of each weight block 73 is covered by plating or vapor deposition, and the first and second conducting electrode layers 75a and 75b are formed integrally.

Next, as shown in FIG. 8, the first conducting electrode 75a of the weight block 73 and the piezoelectric element block 6
The acceleration detection element block 81 is formed by bonding the third detection electrode 65a and the third detection electrode 65a with a conductive adhesive. The acceleration detecting element block 81 is further cut along a plurality of cut surfaces 83 substantially orthogonal to the length L direction, thereby forming the plurality of vibration transducers 30 of the present embodiment.

As described above, according to the acceleration sensor manufacturing method of the present embodiment, an excellent acceleration sensor having a simple structure and a simple manufacturing process, low manufacturing cost, high mass productivity, and high performance can be manufactured. .

[0049]

Second Embodiment FIGS. 9 and 10 show a second embodiment of the vibration transducer of the acceleration sensor according to the present invention. The vibration detector 30 according to the first embodiment has only the function of detecting acceleration, but the vibration detector 90 according to the second embodiment has the function.
Has a self-diagnosis function, and as shown in FIG. 9, is configured to divide each electrode portion to form a capacitor of an independent piezoelectric element. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

More specifically, the vibration transducer 90 of the second embodiment
Is composed of an acceleration detecting section 91 and a weight section 101. The weight unit 101 is disposed above the acceleration detection unit 91, and serves as a weight for the acceleration detection unit 91 to efficiently detect the acceleration applied to the acceleration sensor according to the present invention, as in the first embodiment. It is.

The acceleration detecting section 91 includes a piezoelectric element 33 made of the same piezoelectric element material as the first embodiment.
Having.

As shown in the side view of the vibration transducer 90 in FIG. 10, the acceleration detecting section 91 further includes first and second planes 33a and 33b formed on the piezoelectric element 33, respectively. Detection electrodes 95a and 95b
And first and second input electrodes 97a and 97b similarly formed on the first and second planes 33a and 33b of the piezoelectric element 33, respectively. The first and second detection electrodes 95a and 95b and the first and second input electrodes 97a and 97b are formed so as to be arranged in parallel with each other in a direction parallel to the polarization direction D3 of the piezoelectric element 33. Further, similarly to the first embodiment, the second detection electrode 95b and the second input electrode 97b are located slightly inside by a width d from both ends 33c and 33d of the second plane 33b of the piezoelectric element 33. Are formed respectively.

The weight portion 101 is the same as the vibration transducer 30 of the first embodiment having a bottom surface 43a having substantially the same shape and area as the first flat surface 33a of the piezoelectric element 33 of the acceleration detecting portion 91 and a predetermined mass. It has a weight 43. Weight part 101
A first conduction electrode 105a having substantially the same shape and area as the first detection electrode 95a of the acceleration detection unit 31;
A second conduction electrode 105b formed integrally from two opposing ends of the first conduction electrode 105a and extending over both side surfaces and the upper surface of the weight 43;
Further, the weight portion 101 is formed integrally with a third conduction electrode 107a having substantially the same shape and area as the first input electrode 97a of the acceleration detection section 31 and two opposing ends of the third conduction electrode 107a. And the fourth conduction electrode 10 formed extending over both side surfaces and the upper surface of the weight 43.
7b. The first to fourth conduction electrodes 105a, 105b, 107a and 107b of the weight portion 101
It is formed by plating or vapor deposition. Second and fourth
The conduction electrodes 105b and 107b are not limited to the form of the present embodiment, and the first and third conduction electrodes 105a are similar to the second conduction electrode 45b of the first embodiment.
And 107a only need to be able to input and output electric signals.

According to the acceleration sensor configured as described above, the first and second detection electrodes 95a and 95b,
The two capacitors of the piezoelectric element constituted by the first and second input electrodes 97a and 97b can be formed independently. First and second input electrodes 97
a and 97b to apply a predetermined voltage to the acceleration detecting section 91 to vibrate the piezoelectric element 33, and to generate a potential generated by the vibration to the first and second detection electrodes 95a and 95b.
By extracting the sensor from b, the level calibration of the acceleration sensor and the self-diagnosis function of the quality of the sensor function can be realized.

In this embodiment, as in the first embodiment, the piezoelectric element material may be made of a single-crystal piezoelectric element material such as quartz.

As described above, according to the acceleration sensor of the second embodiment, it is possible to obtain a highly reliable acceleration sensor having a self-diagnosis function with a relatively simple configuration.

[0057]

According to the present invention, the first and second detection electrodes of the acceleration detecting section are arranged at positions parallel to the polarization direction of the piezoelectric element material of the acceleration detecting section. The adverse effect of pyroelectricity on the surface can be reduced from affecting the electrodes, and a stable and high-performance acceleration sensor can be obtained. In addition, since the structure is simple, mass productivity is high and the manufacturing cost can be kept low.

Further, if the first and second detection electrodes of the acceleration detecting section are arranged at positions parallel to the polarization direction of the piezoelectric element material such as the piezoelectric element ceramics of the acceleration detection section, the first and second detection electrodes are formed on the surface of the tip in the polarization direction. The influence of the pyroelectricity on the electrodes can be reduced, and a stable, high-performance acceleration sensor can be manufactured. Further, since the structure is simple, the work is easy, the mass productivity is high, and the manufacturing cost can be kept low.

[Brief description of the drawings]

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

FIG. 2 is a bottom view of the vibration transducer of the acceleration sensor shown in FIG.

FIG. 3 is a front view showing an example of mounting the vibration transducer of the acceleration sensor shown in FIG. 1 on a printed circuit board.

FIG. 4 is a perspective view of a piezoelectric element member prepared in a manufacturing process of the vibration transducer shown in FIG.

5 is a perspective view of a piezoelectric element block formed in a manufacturing process of the vibration transducer shown in FIG.

6 is a perspective view of a weight member prepared in a manufacturing process of the vibration transducer shown in FIG.

FIG. 7 is a perspective view of a weight block formed in a manufacturing process of the vibration transducer shown in FIG.

FIG. 8 is a perspective view of an acceleration detecting element block formed in a manufacturing process of the vibration transducer shown in FIG.

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

FIG. 10 is a side view of the vibration transducer shown in FIG. 9;

FIG. 11 is a sectional elevation view of a conventional acceleration sensor.

FIG. 12 is an equivalent connection diagram of a vibration converter of a conventional acceleration sensor.

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

[Explanation of symbols]

 30, 90 Vibration transducer (acceleration detection element) 31, 91 Acceleration detection unit 33 Piezoelectric element 35a First detection electrode 35b Second detection electrode 41, 101 Weight unit 43 Weight 45a First conduction electrode (Conduction electrode) 45b Second conduction electrode 61 Piezoelectric element member 63 Piezoelectric element block 65a First detection electrode layer 65b Second detection electrode layer 71 Weight member 73 Weight block 75a First conduction electrode layer 75b Second conduction electrode layer 81 Acceleration Detection element block 95a First detection electrode 95b Second detection electrode 97a First input electrode 97b Second input electrode 105a First conduction electrode (conduction electrode) 105b Second conduction electrode 107a Third conduction electrode 107b 4th conduction electrode

Continuation of the front page (72) Inventor Yasuyuki Nakano 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (72) Inventor Tohru Fukuda 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture No. 1 Matsushita Communication Industrial Co., Ltd.

Claims (7)

[Claims] A first plane on which a first detection electrode is formed; and a second plane on a side opposite to the first plane, on which a second detection electrode is formed. An acceleration detecting section made of a plate-like piezoelectric element material polarized in a direction substantially parallel to the second plane, and a conduction electrode having a shape and area substantially equal to the surface of the first detection electrode are formed. In addition, a bottom surface having a shape and area substantially equal to the first plane and a weight having a predetermined mass are provided, and the bottom surface of the weight and the first plane are arranged so as to face each other. An acceleration sensor, wherein the conduction electrode is electrically connected to the first detection electrode, and detects a potential difference between the first and second detection electrodes. 2. The acceleration sensor according to claim 1, wherein the first detection electrode and the conduction electrode are bonded by a conductive adhesive. 3. The acceleration sensor according to claim 1, wherein the weight portion has a linear expansion coefficient substantially equal to that of the piezoelectric element material. 4. A strip-shaped piezoelectric element having a first plane and a second plane opposite to the first plane, and polarized in a direction substantially parallel to the first and second planes. A first preparation step of preparing an element material; a first detection electrode on the first plane of the piezoelectric element material prepared in the first preparation step; and a second detection electrode on the second plane. A first electrode forming step of forming an electrode; a second preparing step of preparing a weight having a shape and area substantially equal to the first plane and a predetermined mass; and A second electrode for forming a conducting electrode having a shape and an area substantially equal to the surface of the first detection electrode formed in the electrode forming step on the bottom surface of the weight prepared in the second preparing step Forming step, the conducting electrode, and the A detection electrode, and a block forming step of forming an acceleration detection element block by bonding with a conductive adhesive, and the acceleration detection element block formed in the block forming step being substantially orthogonal to the length direction. Forming a plurality of acceleration detecting elements by cutting at a plane. A method for manufacturing an acceleration sensor, comprising: 5. The method according to claim 4, wherein the step of forming the first electrode includes the step of forming the first and second detection electrodes by plating or vapor deposition. 6. The method according to claim 4, wherein the step of forming the second electrode includes the step of forming the conductive electrode by plating or vapor deposition. 7. The weight prepared in the second preparing step has a coefficient of linear expansion substantially equal to that of the piezoelectric element material prepared in the first preparing step. 7. A method for manufacturing the acceleration sensor according to any one of 4 to 6.