JPH09236504A - Piezoelectric pressure-sensitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric pressure-sensitive sensor suitable for an automobile air bag activation system by tightly sealing a piezoelectric element part and a shield part by means of a cover part. SOLUTION: A shield part 50 acts as an electric shield for a piezoelectric element part 30. The shield part 50 has a resin plate and a shield conductive layer formed on the resin plate by printing, and is fixedly bonded to the piezoelectric element part 30 via an adhesive. A cover part 70 is constituted of a resin cover member and an adhesive layer, and fixedly bonded to the outside of the shield part 50. The resin cover member of the cover part 70 is formed larger in length and breadth than the piezoelectric element part 30 and shield part, 50, so that the piezoelectric element part 30 and shield part 50 are sealed both at upper and lower faces and side faces thereof. A piezoelectric pressure- sensitive sensor 10 is placed within a seat together with a substrate or a panel. When a man sits on the seat, the piezoelectric pressure-sensitive sensor 10 bends. A voltage generated at this time is detected by an external circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric pressure-sensitive sensor that detects the pressing force of an object.

[0002]

2. Description of the Related Art In recent years, many automobiles in the automobile industry have a tendency to equip an airbag device as a safety device. Especially recently, not only the front side of the driver's seat but also the front side of the passenger seat
Alternatively, it is desired to attach an airbag to the side as well.

In the case where a plurality of airbag devices are equipped, it is not preferable for safety that the airbags at unnecessary positions operate when an accident occurs. Therefore, for example, it is desired to configure a system that detects whether or not a passenger is present in the passenger seat and activates the airbag device on the passenger seat side only when the passenger is present. , A sensor to detect the presence of a person is needed. This type of sensor is required to have good sensitivity for reliable detection and sufficient sealing characteristics (waterproof and oilproof characteristics) for use as an automobile part. It is an object of the present invention to provide a sensor suitable for such an airbag operating system, and more particularly to provide a piezoelectric pressure sensitive sensor which is embedded in a seat and senses a pressing force generated when a person sits on the seat. And

[0004]

A piezoelectric pressure-sensitive sensor of the present invention comprises a piezoelectric resin film having a substantially rectangular band shape, a shield conductive layer which is electrically insulated along the front and back surfaces of the piezoelectric resin film, and From a plurality of connecting portions that are electrically connected to each of the piezoelectric resin film and the shield conductive layer, and a pair of resin plates that are larger in length and width than the piezoelectric resin film and the shield conductive layer And a cover member configured to hermetically seal the piezoelectric resin film and the shield conductive layer from all directions via an adhesive while extending the connection portion to the outside.

The piezoelectric pressure-sensitive sensor of the present invention includes a strip-shaped piezoelectric resin film. Electrodes are printed on both sides of the piezoelectric resin film. Each electrode is connected to a connection portion for electrical connection with an external device at one end side in the length direction of the piezoelectric resin film. Thus, an electric signal generated when pressure is applied to the piezoelectric resin film can be sent to the external device via the connecting portion. Shielding means are preferably provided on the outside of both electrodes. The shield means also has a connecting portion for establishing electrical connection with an external device. The piezoelectric pressure-sensitive sensor further has cover means composed of a thin plate-shaped resin cover member and an adhesive layer, which seals the whole except a connecting portion of the piezoelectric resin film and the shield means. The plate-shaped resin cover member is made of a material such as polyester, nylon, polypropylene or Teflon polyimide. The thickness of the cover means is preferably about 10 μm to 100 μm. The plate-shaped resin cover enhances the rigidity of the piezoelectric pressure-sensitive sensor and improves the sensitivity of the sensor.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piezoelectric pressure-sensitive sensor which is a preferred embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view of a piezoelectric pressure sensitive sensor. FIG.
FIG. 3 shows an enlarged plan view of an end portion of the piezoelectric pressure-sensitive sensor, and FIG. 3 shows a schematic view of a partial cross section taken along a line 5-5.

According to FIGS. 1 and 3, a piezoelectric pressure sensitive sensor 1
Reference numeral 0 indicates the piezoelectric element portion 30 and the shield portion (shield means) 5
0, and a cover portion (cover means) 70. As shown in FIG. 3, the piezoelectric element portion 30 has a piezoelectric resin film 31 made of a material such as PVDF (polyvinylidene fluoride), and electrodes 32 and 33 formed on both sides of the piezoelectric resin film 31. The electrodes 32 and 33 are formed by printing on the piezoelectric resin film 31. The electrodes 32 and 33 include extensions 32a and 33a extending to the position of a terminal (connection portion) 90 for connecting to an external device as shown in FIG. Extensions 32a, 33a and terminal 9
The connection method with 0 will be described later.

The shield portion 50 is a piezoelectric element portion 3 as shown in FIG.
It is located outside 0 and acts as an electrical shield for the piezoelectric element portion 30. The shield part 50 is formed by printing resin plates 51, 52 made of polyester or the like and the resin plates 51, 52 thereon. The piezoelectric element unit 30 has shield conductive layers 53 and 54, and acrylic adhesives 34 and 35 as shown in FIG.
Adhesively fixed. The resin plates 51 and 52 may have the same plate thickness or different plate thicknesses, but different plate thicknesses are preferable in terms of pressure-sensitive characteristics. The shield conductive layers 53 and 54 are electrodes 32,
Placed along 33 to cover them. Similarly to the electrodes 32 and 33, the shield conductive layers 53 and 54 also include extensions 53a and 54a extending to the positions of the terminals (connection portions) 90. A method of connecting the extension portions 53a and 54a to the terminal 90 will be described later. Further, although not shown in detail, the upper and lower shield conductive layers 53 and 54 are fitted in eyelet fittings 80 fitted in through holes arranged near the ends on the opposite side to the terminals 90.
Are electrically connected to each other (see FIG. 1).

The cover portion 70 is composed of a resin cover member 71 and an adhesive layer 72 for adhering the resin cover member 71, and is adhered and fixed to the outside of the shield portion 50. The resin cover member 71 is a thin plate member, and is made of a material such as polyester such as PET or PBT, nylon, polypropylene, Teflon, or polyimide. The adhesive layer 72 is selected to be suitable for adhering the material of the resin cover member 71 described above, and for example, an adhesive of polyethylene type and acid copolymer is used. The thickness of the cover portion 70 including the resin cover member 71 and the adhesive layer 72 is 10 μm to 100 μm.

The resin cover member 71 of the cover portion 70 is shown in FIG.
Further, as understood from FIG. 3, the length and width of the piezoelectric element portion 30 and the shield portion 50 are larger than those of the piezoelectric element portion 30 and the shield portion 50.
Therefore, when the material 71 of the cover portion 70 is adhered from the vertical direction in FIG. 3, the upper and lower resin cover members 71 are adhered to each other via the adhesive at the edge, whereby the piezoelectric element portion 3 is formed.
0 and the shield part 50 are sealed not only on the upper and lower surfaces but also on the side surfaces.

At the end, as shown in FIG. 2, the extension 32a,
33a, 53a, 54a are arranged so as to extend substantially in parallel. However, as can be seen from FIG. 3, the electrodes 32,
33 and the shield conductive layers 53 and 54 are formed by extension. Each of the extensions 32a, 33a, 53a, 54a is placed at different positions in the height direction. Therefore, terminal 9
The terminal 90 is piercingly connected in the thickness direction from the height position 7 in FIG. 3 before the cover portion 70 is attached so that the 0 and the extension portions 32a, 33a, 53a, 54a are electrically contacted. As can be seen from FIG. 2, the plurality of terminals 9
Each 0 is independently connected to each of the extensions 32a, 33a, 53a, 54a. Although not shown, this allows the terminal 9
The 0 tine portions 91 are arranged in parallel in the height direction. The extending portion 92 of the tine portion 91 is sealed when the cover portion 70 is bonded.

Further, the piezoelectric pressure sensitive sensor 10 is shown in FIGS.
As described above, there are three through holes 60. The through hole 60 is for attaching the piezoelectric pressure sensitive sensor 10 to a substrate or a panel. A rivet metal fitting or other mounting member (not shown) is arranged in the through hole to support and fix the piezoelectric pressure sensitive sensor 10 at a desired position on the substrate or panel. The piezoelectric pressure sensitive sensor 10 is placed in a sheet with a substrate or panel.
When a person takes a seat, the piezoelectric pressure sensor 10
Causes bending, and the voltage generated at this time is detected by an external circuit.

Although the piezoelectric pressure-sensitive sensor which is a preferred embodiment of the present invention has been described above, this does not limit the present invention, and various modifications and changes can be made by those skilled in the art.

[0015]

EXAMPLE A piezoelectric pressure-sensitive sensor was constructed with the construction shown in FIGS. First, the length is about 170 mm and the width is about 20 m.
An electrode was printed with silver paste on both sides of a PVDF piezoelectric film having a thickness of m and a thickness of about 28 μm, and a shield means was adhesively fixed to the outer side of the electrode with an acrylic adhesive. As the shield means, a shield conductive layer printed with a silver paste on a PET film "Myler" which is a registered trademark of DuPont, USA was used. Further, a PET film having a thickness of about 12 μm was adhered to the outer side thereof to form a cover part. Specifically, PET
Anchor coat was applied to the inner surface of the film, and a polyethylene-based and acid-copolymer-based adhesive was laminated on the film by about 70 μm. As a result, the piezoelectric element portion and the shield means are hermetically sealed in all directions, with a length of about 190 mm and a width of about 60 m.
A rectangular piezoelectric piezoelectric pressure-sensitive sensor of m was obtained.

This piezoelectric pressure-sensitive sensor was arranged horizontally, and a sphere having a mass of 5.46 g was dropped from a position of 200 mm in height on this, and the voltage generated at that time was measured.
The average value of 0 samples was about 2.43V. When a sample having no cover portion was measured by the same method for comparison, the average value of 10 samples was about 0.83V.
Met. That is, it was confirmed that the piezoelectric pressure-sensitive sensor of this example has a better detection sensitivity by including the cover portion.

[0017]

The piezoelectric pressure-sensitive sensor of the present invention has good sealing characteristics (waterproofing and oilproofing characteristics) and has a relatively good sensitivity due to the appropriate rigidity imparted by the cover portion. It is suitable as a pressure-sensitive sensor mounted in the seat of an automobile for operation.

[Brief description of drawings]

FIG. 1 is a plan view of a piezoelectric pressure-sensitive sensor according to a preferred embodiment of the present invention.

FIG. 2 is an enlarged view of an end portion of the piezoelectric pressure sensitive sensor of FIG.

FIG. 3 is an exploded cross-sectional schematic view showing a cross section taken along the line 5-5 in FIG.

[Explanation of symbols]

 31 piezoelectric resin film 53, 54 shield member 71 cover member 72 adhesive 90 connection part

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[Procedure amendment]

[Submission date] September 20, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Deleted

Claims (1)

[Claims] 1. A substantially rectangular strip-shaped piezoelectric resin film, a shield conductive layer which is electrically insulated and placed along front and back surfaces of the piezoelectric resin film, and each of the piezoelectric resin film and the shield conductive layer. And a plurality of connecting portions that are electrically connected to each other, and a pair of resin plates that are formed to have a length and a width that are larger than the piezoelectric resin film and the shield conductive layer, and extend the connecting portions to the outside. At the same time, the piezoelectric pressure sensitive sensor is characterized by having a cover member that hermetically seals the piezoelectric resin film and the shield conductive layer from all directions via an adhesive.