JPH071211B2 - Piezoelectric pressure distribution sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric pressure distribution sensor that detects contact pressure distribution by arranging a plurality of piezoelectric elements in a matrix.
In particular, it relates to one provided with an electromagnetic wave shield structure.

[Conventional technology]

FIG. 2 shows a schematic configuration of a conventional piezoelectric pressure distribution sensor in a partially cutaway side sectional view.

In the piezoelectric pressure distribution sensor, a plurality of piezoelectric elements 2 are arranged in a matrix on a base member 1 made of an insulating material to form a piezoelectric element group. Further, a conductive frame 3 protruding upward so as to surround the piezoelectric element group is attached to the peripheral portion of the base member 1. Frame 3
A flexible pressure sheet 4 is disposed in the upper opening of the. The pressure sheet 4 is made of a flexible material so as to press the upper end surface of each piezoelectric element 2 of the piezoelectric element group, and the peripheral edge portion thereof is fixed to the frame 3.

In the above structure, by measuring the potential difference between the electrodes (not shown) provided at the upper ends of the plurality of piezoelectric elements 2 arranged on the base member 1, each piezoelectric element is pressed through the pressure sheet 4. It is possible to calculate the pressure applied to the element 2 and to know the pressure distribution based on the calculated pressure.

[Technical problem to be solved by the invention]

In the above-mentioned pressure distribution sensor, the periphery is covered with the conductive frame 3, but the electromagnetic waves above the plurality of piezoelectric elements 2 forming the piezoelectric element group are not sufficiently shielded. Therefore, the measurement accuracy may be deteriorated due to the influence of the surrounding electromagnetic noise.

Therefore, it is an object of the present invention to provide a piezoelectric pressure distribution sensor that has a structure capable of effectively preventing the influence of electromagnetic wave induction noise, and can thereby accurately measure the pressure distribution. .

[Means for solving technical problems]

In the piezoelectric pressure distribution sensor of the present invention, a plurality of piezoelectric elements are arranged in a matrix on the base member to form a piezoelectric element group. A pressure sheet made of a flexible material is arranged above the piezoelectric element group. The piezoelectric element group and the pressure sheet are housed in a case including a base member and a case lid. The case lid is formed with an opening that exposes a sheet region of the pressure sheet that faces the upper end surface of the piezoelectric element group and the front and back sides.

At least one surface of each of the base member and the case lid is configured to have a conductive surface, and a ground electrode is formed on at least the entire back surface portion of the lower surface of the pressure sheet exposed to the opening. Has been done.
The ground electrode is electrically connected to the conductive surface of the case lid. .

[Action]

Since a ground electrode is formed on at least the entire area of the back surface of the lower surface of the pressure sheet exposed to the opening of the case lid, the ground electrode is electrically connected to the conductive surface of the case lid. , The internal piezoelectric element group, other electronic components, and the wiring pattern are reliably electromagnetically shielded. Therefore, it is possible to effectively suppress the influence of the electromagnetic induction noise on the measurement.

[Explanation of Examples]

FIG. 3 is a schematic perspective view of an embodiment of the present invention. The piezoelectric pressure distribution sensor 10 according to the present embodiment is configured inside a case lid 11 made of a conductive material such as stainless steel. The case lid 11 may be made of an insulating material instead of a conductive material. In that case, a conductive film is formed on the entire inner surface or outer surface so that at least one surface has a conductive surface. Need to be configured.

A rectangular opening 11a is formed in the case lid 11. As will be described later, the portion exposed in the opening 11a is brought into contact with the object to be measured, and its pressure distribution is detected.

The internal structure of the above embodiment will be described with reference to the exploded perspective view of FIG. 4 and the sectional view of FIG.

The case of the sensor of this embodiment includes the case lid 11 described above,
And the base member 12. Base member 12
Is made of a metal material such as stainless steel. This base member
Similarly to the case lid 11, the 12 may be made of an insulating material. However, when it is made of an insulating material, it is necessary to form a conductive film on the inner surface or the outer surface of the base member 12 so that one surface becomes a conductive surface.

On the base member 12, the positioning pin 12 protruding upward
a and 12b are formed. The positioning pins 12a and 12b are provided to perform positioning of each member, which will be described later, mounted on the base member 12.

In the corner portion of the base member 12, rectangular protruding portions 12c to 12f protruding upward are formed. Screw holes 13 are formed on the side surfaces of the protrusions 12c to 12f. The screw holes 13 are provided for accommodating the respective members on the base member 12 and fixing the case lid 11 to the base member 12 with the screws 14 in a state in which the case lid 11 is covered.

A flexible substrate 15 is placed directly above the base member 12. The flexible board 15 includes positioning pins 12a,
Positioning holes 15a and 15b that are inserted into 12b are formed.

Although not shown accurately in FIG. 4, a predetermined wiring pattern 16 (see FIG. 1) is formed on the upper surface of the flexible substrate 15, and a chip-type capacitor is provided in a portion indicated by an imaginary line A. The FET is mounted on the portion indicated by the phantom line B. Further, piezoelectric elements to be described later are placed in the four rectangular areas indicated by the imaginary line C. Then, the electrode formed on the lower end surface of the piezoelectric element and the wiring pattern 16 on the flexible substrate 15 are electrically connected.

On the other hand, as shown in FIG. 1, a ground electrode 17 is formed on the entire lower surface of the flexible substrate 15, and the ground electrode 17 is electrically connected to the connection electrode 19 on the upper surface side of the flexible substrate 15 by a through hole 18. Connected to each other.

Returning to FIG. 4, reference numeral 20 denotes a cable, which is a flexible substrate.
It is connected to the input / output pad provided on 15.

A resin frame 21 having a rectangular planar shape is provided on the flexible substrate 15.
Is placed. The resin frame 21 is formed with four through holes 21a to 21d for accommodating piezoelectric elements and through holes 21e and 21f through which the positioning pins 12a and 12b penetrate. The resin frame 21 is provided to house each of the four piezoelectric elements 22 to 25. The thickness of the resin frame 21 is smaller than the thickness of the piezoelectric elements 22 to 25.

The piezoelectric elements 22 to 25 are made of a piezoelectric material that generates an electric charge by a piezoelectric effect when pressure is applied in the vertical direction, and each has a structure in which electrodes are provided on the upper and lower end surfaces. As the piezoelectric material, a material having relatively high rigidity such as piezoelectric ceramics or piezoelectric single crystal is used.

An elastic sheet 26 having an opening 26a is placed on the resin frame 21. The opening 26a is formed in such a size that the upper end surfaces of the piezoelectric elements 22 to 25 are exposed. The elastic sheet 26 is made of an elastic material such as synthetic rubber.

On the elastic sheet 26, a second flexible substrate 27 that functions as a pressure sheet for bringing the piezoelectric element into contact with the object to be measured.
Is placed. Inside the flexible substrate 27, a rectangular through hole 27a is formed. The through hole 27a is formed in a shape and a size into which the fitting protrusion 21g formed on the upper surface of the resin frame 21 can be inserted. The through hole 27a and the fitting protrusion 21g
Thus, the positioning of the flexible substrate 27 is completed.

Referring also to FIG. 1, a ground electrode 27b is formed on the entire lower surface of the second flexible substrate 27. The ground electrode 27b is the electrode 22a, 24a on the upper end surface of the piezoelectric element 22, 24.
And electrically connected by a conductive adhesive (not shown). The electrodes on the upper end surfaces of the piezoelectric elements 23 and 25, which are not shown in FIG. 1, are similarly electrically connected to the ground electrode 27b.

On the other hand, on the upper surface of the flexible substrate 27, as shown in FIG. 4, an electrode pattern 27c on a rectangular frame is formed. As is apparent from FIG. 1, the electrode pattern 27c is formed in a shape that is in contact with the inner surface of the case lid 11 outside the peripheral edge of the opening 11a.

A through hole 28 is also formed in the second flexible substrate 27, and the ground electrode 27 is formed by the through hole 28.
b and the electrode pattern 27c on the upper surface are electrically connected. Therefore, the ground electrode 27 on the lower surface of the flexible substrate 27
b is electrically connected to the case lid 11 through the through hole 28 and the electrode pattern 27c.

Above the flexible substrate 27, first to fourth height adjusting members 29 to 32 made of a material such as stainless steel whose thickness can be reduced by machining are connected to the connecting member 33.
The height adjusting plates 34 connected to each other are fixed.

The first to fourth height adjusting members 29 to 32 have a rectangular planar shape, and are mounted on the upper and lower surfaces of the piezoelectric elements 22 to 25, which are opposed to each other via the flexible substrate 27. Height adjustment member 29
The elements 32 to 32 do not necessarily need to be connected to each other by the connecting member 33 as illustrated, and may be provided independently. The height adjusting members 29 to 32 are
It is provided in order to make the height of the sensor in the portion where the piezoelectric elements 22 to 25 are provided uniform by reducing the thickness by machining.

The above-mentioned components are placed on the base member 12, the case lid 11 is covered with the necessary portions fixed, and the case lid 11 is fixed to the base member 12 with the screw 14. The pressure distribution sensor 10 can be obtained.

Next, the characteristic structure of the present embodiment will be described more specifically with reference to FIG. 1 showing an enlarged main part of a portion along the line II in FIG.

In the assembled state, above the piezoelectric elements 22 and 24, the second flexible substrate 2 having the ground electrode 27b formed on the lower surface is formed.
7 is placed. As described above, the ground electrode 27b is electrically connected to the case lid 11 via the through hole 28 and the electrode pattern 27c.

On the other hand, below the piezoelectric elements 22 to 25, the ground electrode 17 is formed on the entire lower surface of the first flexible substrate 15.
The piezoelectric pressure distribution sensor 10 of this embodiment is entirely surrounded by a case lid 11 and a base member 12 made of a conductive material, and is provided with a temporary electromagnetic shield structure. Further, the case lid 11 made of a conductive material is provided at the portion where the opening 11a is provided, that is, the portion that comes into contact with the measured object.
Is not present, but in the portion facing this opening 11a,
A ground electrode 27b is formed on the lower surface of the second flexible substrate 27, and the ground electrode 27b is electrically connected to the case lid 11 through the through hole 28 and the electrode pattern 27c. Therefore, the electromagnetic shield structure is provided also in the opening 11a. Therefore, open the measured object
When the pressure distribution is detected by abutting from the 11a side, the influence of electromagnetic induction noise from the outside can be effectively prevented.

Although the ground electrode 27b is formed on the entire lower surface of the second flexible substrate 27 in the above embodiment, the case lid 1
Since 1 is configured to have a conductive surface on at least one surface, the effect of the present invention can be obtained as long as the ground electrode 27b is formed only on at least the back surface of the portion exposed to the opening 11a. You can

〔The invention's effect〕

As described above, in the present invention, the base member and the case lid are made of a material having a conductive surface on at least one surface,
Since the ground electrode is formed on at least the entire area of the back surface of the lower surface of the pressure sheet facing the opening of the case lid, and the ground electrode is electrically connected to the conductive surface of the case lid, It is possible to reliably electromagnetically shield the housed piezoelectric element and other electronic components. Therefore, the pressure distribution based on the contact of the measured object can be accurately detected regardless of the presence of electromagnetic induction noise from the outside. Therefore, the accuracy and reliability of the piezoelectric pressure distribution sensor can be effectively improved.

[Brief description of drawings]

FIG. 1 is an enlarged view of the essential parts of an embodiment of the present invention,
FIG. 2 is an enlarged sectional view of a portion taken along line II in the figure, FIG. 2 is a partially cutaway side sectional view for explaining a conventional example, FIG. 3 is a schematic perspective view of an embodiment of the present invention, and FIG. It is an exploded perspective view of an example of a figure. In the figure, 10 is a piezoelectric pressure distribution sensor, 11 is a case lid, 11a is an opening, 12 is a base member, 22-25 are piezoelectric elements, 2
Reference numeral 7 is a second flexible substrate as a pressure sheet, 27b is a ground electrode, 27c is a frame-shaped electrode pattern, and 28 is a through hole.

Claims (1)

[Claims] 1. A base member, a piezoelectric element group composed of a plurality of piezoelectric elements arranged in a matrix on the base member, and a flexible member arranged above the plurality of piezoelectric element groups. A pressure sheet and a case that accommodates at least the piezoelectric element group and the pressure sheet in cooperation with the base member are configured, and at least the upper end surface of the piezoelectric element group of the pressure sheet faces the front and back sides. A piezoelectric pressure distribution sensor having a case lid having an opening exposing a sheet upper surface region, wherein at least one surface of each of the base member and the case lid is made of a material having a conductive surface, and the lower surface of the pressing sheet. A ground electrode is formed on at least the entire back surface of the region exposed to the opening, and the ground electrode is electrically connected to the conductive surface of the case lid. Characterized in that it is connected, piezoelectric pressure distribution sensor.