JPH0727784A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor provided with a detection element composed of piezoelectric ceramic sheets which are bonded firmly without using an adhesive. CONSTITUTION:An acceleration sensor is provided with a bimorph-type detection element 1 formed in such a way that one pair of polarized piezoelectric ceramic sheets 4 in which electrodes 2, 3 are formed on main faces are opposedly bonded. In the acceleration sensor, the bimorph-type detection element 2 is manufactured in such a way that one pair of piezoelectric ceramic green sheets 5 in which electrode patterns 6, 7 are printed on main surfaces are overlapped, the green sheets are pressurized along their thickness direction and baked, and a polarization treatment is executed to each sheet of the ceramic laminated body which is obtained by baking.

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 the structure of a bimorph type detection element included in the acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, some acceleration sensors are constructed by incorporating a piezoelectric element, and a piezoelectric element of this type is a bimorph type which is called a double-supported beam structure as shown in FIG. Detection element (hereinafter referred to as detection element)
It is common to use 10. That is, the detection element 10 is formed by strip-shaped, and a pair of piezoelectric ceramic plates 13 each having a signal extraction electrode 11 and an intermediate electrode 12 formed on each of the main surfaces thereof are face-bonded to each other. The piezoelectric ceramic plate 13 is the intermediate electrode 12.
The main surfaces formed with are bonded together by an adhesive agent 14 to be integrated. It should be noted that each of the piezoelectric ceramic plates 13 has a desired direction such as a direction (indicated by arrows X and Y in the drawing) opposite to the other side along the thickness direction at the time before bonding. Is polarized according to the direction of.

Further, both end edges along the longitudinal direction of the detection element 10 thus manufactured are fixedly supported by a pair of holding parts 15 having a "U" shape in a side view. Each of the signal extraction electrodes 11 formed on each piezoelectric ceramic plate 13 is connected to each of the external extraction electrodes 16 and 17 formed on each different end face of the sandwiching component 15, and the sensor is connected through these electrodes. It is connected to a wiring pattern (not shown) on the substrate. The sandwiching component 15 has the above-described shape in order to secure a bending margin of the detection element 10 itself which is deformed by the inertial force caused by the action of the acceleration G.

[0004]

By the way, when manufacturing the detecting element 10 having the above-mentioned conventional structure, as shown in FIG. 4, the signal extracting electrode 11 and the intermediate electrode 12 are formed on the main surface.
A pair of ceramic parent boards 18 each having an electrode layer (not shown) formed thereon and a pair of parent board 19 for holding parts in which a groove having a predetermined width is formed at each predetermined position on the inner surface side. After being prepared, the ceramic parent boards 18 are bonded to each other with an adhesive (not shown), and the parent board 19 for holding parts is abutted from the outside of each ceramic parent board 18 to integrally bond them. Will be cut along each of the cutting lines S set as intersecting shapes.

However, when the ceramic parent substrates 18 are adhered to each other by an adhesive agent, the adhesive agent having a uniform thickness does not always adhere to the entire surface between the ceramic parent substrates 18 without leakage. Therefore, a portion where no adhesive is attached or a portion where the thickness of the adhesive is thick are locally dispersed. Therefore, in the detection element 10 manufactured by cutting after the parent substrate 19 for sandwiching components is bonded, the pair of piezoelectric ceramic plates 13 forming the same are not bonded at all with the adhesive 14. As a result, the bonding state is insufficient, and as a result, the detection accuracy of the accelerations of the detection elements 10 that are the products do not match and vary.

In order to avoid such an inconvenience, the adhesive is hardened by applying a sufficiently large pressure along the thickness direction of the ceramic parent substrates 18 when the adhesive is used for bonding. However, in this case, each ceramic mother board 1
Since the thickness of No. 8 is as thin as about 100 to 150 μm, there is an inconvenience of being damaged. Therefore, it has been proposed to increase the thickness of these ceramic parent substrates 18 from the beginning, or to attach them after interposing a metal plate between them, but these measures were taken. In some cases, the detection element 10 completed as a product
In this case, the output sensitivity may be lowered.

The present invention was devised in view of such inconvenience, and provides an acceleration sensor having a detection element composed of a pair of piezoelectric ceramic plates that are firmly face-to-face joined without using an adhesive. It is an object.

[0008]

An acceleration sensor according to the present invention comprises a detection element comprising a pair of piezoelectric ceramic plates, each having a main surface on which electrodes are formed and polarized, and which are face-to-face bonded to each other. This detection element is constructed by stacking a pair of piezoelectric ceramic green sheets (hereinafter referred to as “green sheets”) on the main surface of which electrode patterns are printed, and
After firing these under pressure along the thickness direction,
Each of the ceramic laminates obtained by firing is subjected to a polarization treatment to be produced.

[0009]

According to the above-mentioned means, the ceramic parent substrates constituting the detection element are firmly face-to-face joined by firing a pair of green sheets, and as a result, they are purposely face-to-face with an adhesive. There will be no need to join.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view showing a detection element used in constructing the acceleration sensor according to this embodiment, and FIG. 2 is an exploded perspective view showing a part of a manufacturing procedure thereof. Reference numeral 1 indicates a detection element having a double-supported beam structure. In FIG. 1, parts and portions which are the same as those in FIG. 3 showing the conventional example are denoted by the same reference numerals.

The detection element 1 included in the acceleration sensor according to the present embodiment is formed into a strip shape, and a thin film signal extraction electrode 2 and an intermediate electrode 3 are formed on each of the main surfaces, and a polarization treatment is performed. It is composed of a pair of piezoelectric ceramic plates 4 which are connected to each other, and these piezoelectric ceramic plates 4 are face-to-face bonded via the intermediate electrode 3. Both end edges along the longitudinal direction of the face-to-face bonded piezoelectric ceramic plates 4 are fixed and supported by a pair of sandwiching parts 15 having a "U" shape in a side view as in the conventional example. Each of the signal extraction electrodes 2 formed on the wiring 4 is passed through the external extraction electrodes 16 and 17 formed on each different end face of the sandwiching component 15 and then formed into a wiring pattern (neither is shown) on the sensor substrate. It is connected.

In FIG. 1, the polarization directions of the piezoelectric ceramic plates 4 are aligned in the directions (indicated by arrows X and Y in the figure) which are opposite to the other side along the respective thickness directions. However, the polarization processing is not limited to these directions, and it goes without saying that polarization processing is performed in accordance with a desired direction in consideration of the acting direction of the acceleration G. That is, the longitudinal region of each piezoelectric ceramic plate 4 is divided into, for example, three parts, and each of the central portion and the end portion of each piezoelectric ceramic plate 4 is divided as indicated by an arrow represented by a virtual line in FIG. May be polarized so that they are opposite to each other while the other side is also opposite. When such polarization treatment is performed, the detection element 1
Therefore, the detection sensitivity can be improved.

By the way, the detecting element 1 is manufactured according to the procedure as shown in FIG. That is,
First, a pair of green sheets 5 having a required thickness and size are prepared. On the main surface of each green sheet 5, the electrode patterns 6 and 7 to be the signal extraction electrodes 2 and the intermediate electrodes 3 in the product are respectively provided. It is formed by printing a conductive paste. At this time, as shown in FIG. 2, the electrode pattern 7 serving as the intermediate electrode 3 is printed only on the inward main surface of the green sheet 5 located on either side (lower side in FIG. 2). Just keep it.

Next, although not shown, the electrode pattern 7
After the pair of green sheets 5 are overlapped with each other so as to sandwich them, they are pressed along the thickness direction and then fired. Then, these green sheets 5 become a ceramic mother board which is a ceramic laminated body by being fired, and the pair of ceramic mother boards composed of the green sheets 5 which have been pressed and brought into close contact are firmly face-to-face joined. Will be there. Then, at this time, the electrode patterns 6 and 7 formed on the main surfaces of the green sheets 5 become the electrode layers forming the signal extraction electrode 2 and the intermediate electrode 3 by baking accompanying the firing, and the ceramic parent substrates are separated from each other. Face-to-face bonding is performed via an electrode layer which becomes the intermediate electrode 3.

Further, with respect to each of the ceramic parent substrates as the ceramic laminated body thus obtained,
For example, the polarization process is performed in a desired direction as shown in FIG. Then, as shown in FIG. 4, each of the sandwiching component parent substrates 19 prepared separately in advance, that is, each of the sandwiching component parent substrates 19 in which a groove having a predetermined width is formed at each predetermined position on the inner surface side. 1 is applied from the outside of each of the face-to-face joined ceramic mother substrates to be joined integrally, and then the whole of them is cut along each of the cutting lines S set as intersecting shapes, whereby the detection element having the structure shown in FIG. 1 has been created.

In the embodiment described above,
It is supposed that a large number of ceramic laminated bodies are collectively manufactured by stacking and firing the green sheets 5 having a size suitable for manufacturing a large number of detecting elements 1. There is no limitation, and it is also possible to fabricate a single ceramic laminate by stacking green sheets 5 each having a size suitable for a single detection element 1 in advance, applying pressure, and then firing. is there. In addition, in the present embodiment, the both end edges along the longitudinal direction of the detection element 1 are held by the sandwiching component 15 having the “U” shape. However, for example, only one end edge along the longitudinal direction of the detection element 1 is held. Needless to say, the detection element 1 having a cantilever structure can also be configured by holding it by the sandwiching component 15.

[0018]

As described above, the detection element provided in the acceleration sensor according to the present invention is obtained by stacking green sheets, pressing them along the thickness direction, firing them, and then firing them. Each of the obtained ceramic parent substrates is subjected to polarization treatment and then cut, and the pair of piezoelectric ceramic plates constituting the detection element are firmly face-to-face joined by firing through the intermediate electrode. Therefore, unlike the conventional example, there is no need to purposely bond the piezoelectric ceramic plates to each other by using an adhesive agent, and it is impossible to cause a disadvantage associated with the use of the adhesive agent. As a result, the acceleration detection precisions of the detection elements, which are products, are extremely well matched, and there is an excellent effect that there is no fear of causing a reduction in output sensitivity.

[Brief description of drawings]

FIG. 1 is an external perspective view showing a detection element of an acceleration sensor according to an embodiment.

FIG. 2 is an exploded perspective view showing a part of the manufacturing procedure of the detection element according to the present embodiment.

FIG. 3 is an external perspective view showing a detection element according to a conventional example.

FIG. 4 is an exploded perspective view showing a procedure for manufacturing a detection element according to a conventional example.

[Explanation of symbols]

1 detection element (bimorph type detection element) 2 signal extraction electrode 3 intermediate electrode 4 piezoelectric ceramic plate 5 green sheet (piezoelectric ceramic green sheet) 6 electrode pattern 7 electrode pattern

Claims (1)

[Claims] 1. An acceleration sensor comprising a bimorph type detection element (1) comprising a pair of piezoelectric ceramic plates (4) having electrodes (2, 3) formed on a main surface and polarized, which are face-to-face bonded. Therefore, the bimorph type detection element (1) has a main surface on which a pair of piezoelectric ceramic green sheets (5) on which electrode patterns (6, 7) are printed are superposed, and these are applied along the thickness direction. An acceleration sensor manufactured by subjecting each of the ceramic laminates obtained by firing to pressure and firing, and then subjecting each to a polarization treatment.