JPH02218932A - Piezoelectric type pressure distribution sensor - Google Patents

Abstract

PURPOSE:To correctly detect pressure distribution due to contact of an object to be brought into contact by a method wherein the thickness of a height adjusting member provided corresponding to each piezoelectric element part is adjusted by machine-work. CONSTITUTION:A flexible substrate 23 formed with an electrode pattern 23b on the lower surface is mounted over piezoelectric elements 18, 20. This pattern 23b is electrically connected with electrodes 18a, 20a on the uppermost surfaces of the elements 18, 20 with conductive adhesive. On the lowermost surfaces of the elements 18, 20, a wiring pattern 15d on a flexible substrate 15 mounted on a base member 12 and electrodes 18b, 20b on the lowermost surfaces of the elements 18, 20 are fixed together with the conductive adhesive. Further above the elements 18, 20 height adjusting members 24, 26 are fixed on the outer surface wherein the surface and the rear face are opposed via the substrate 23. By grinding the members 24, 26 after the respective members have been assembled, the height of the surfaces to be brought in contact with an object to be measured is made equal so as to correctly detect pressure distribution due to the contact of the object to be measured.

Description

[Detailed Description of the Invention] [Industrial Application 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, the present invention relates to a structure that eliminates variations in thickness in a portion where a plurality of piezoelectric elements are provided.

[Conventional technology]

JP-A-62-297735 discloses a sensor that detects contact pressure distribution by arranging a plurality of piezoelectric elements in a matrix.

Here, the pressure applied to each piezoelectric element is calculated by measuring the potential difference between the electrodes provided at both the upper and lower ends of multiple piezoelectric elements arranged on the base member, and the pressure distribution is calculated based on this. It is considered possible to know.

The structure of the above-mentioned prior art will be explained with reference to FIG.

A wiring pattern 2 is formed on the base member 1. Piezoelectric elements 3 are placed on predetermined positions of the wiring pattern 2, respectively.

A pair of electrodes (not shown) are provided on both upper and lower end surfaces of the piezoelectric element 3.
is formed, and the lower electrode is electrically connected to the wiring pattern 2.

On the other hand, above the piezoelectric element 3, a flexible pressure sheet 4 is arranged. A wiring pattern 5 is also formed on the lower surface of the pressure sheet 4, and at a predetermined position of the wiring pattern 5,
An electrode formed on the upper end surface of the piezoelectric element 3 is bonded with a conductive adhesive.

In the above structure, when an object comes into contact with the outer surface of the pressure sheet 4, pressure is applied to each piezoelectric element 3 according to the pressure distribution based on the contact pressure of the object. Therefore, by detecting the electric charge generated in each piezoelectric element 3 due to the piezoelectric effect using a detection device (not shown), it is possible to detect the pressure distribution based on the abutted object.

[Technical Problem to be Solved by the Invention] In the conventional piezoelectric pressure distribution sensor, a plurality of piezoelectric elements 3 are required to accurately detect the pressure distribution based on the abutted object.
It is required that the height of the part where the is provided is uniform. However, in the conventional structure, due to variations in the thickness of the pressure sheet 4 and the base member 1, variations in the height of the piezoelectric elements 3, variations in the thickness of the adhesive layer, etc., the sensor at the part where each piezoelectric element 3 is provided. There was no choice but to cause variations in the thickness.

In the piezoelectric pressure distribution sensor, the piezoelectric element 3 is less distorted by the applied force, and therefore can constitute a highly sensitive sensor with very small distortion as a whole. in spite of,
In the structure of the prior art, it was not possible to suppress variations in the thickness of the portion where each piezoelectric element was provided, so it was difficult to take advantage of the excellent characteristics of the piezoelectric element.

Therefore, an object of the present invention is to make it possible to make the thickness of the sensor uniform in the part where a plurality of piezoelectric elements are provided, that is, to make it possible to make the height of the part that comes into contact with the object to be measured uniform. Therefore, it is an object of the present invention to provide a piezoelectric pressure distribution sensor that can detect pressure distribution with high sensitivity and accuracy.

[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 a base member to form a piezoelectric element group. A pressure sheet is arranged so as to come into contact with the end surface of the plurality of piezoelectric elements opposite to the base member. A plurality of height adjustment members are respectively attached to the outer surface portions of the pressure sheet which face each other with the pressure sheet interposed between the end surface of each piezoelectric element opposite to the base member. This height adjustment member is constructed from a material whose thickness can be reduced by machining.

[Effect]

Since the plurality of height adjustment members are made of a material whose thickness can be reduced by machining, the thickness of the height adjustment member provided corresponding to each piezoelectric element portion can be adjusted by machining. This makes it possible to equalize the height of the surface in contact with the object to be measured in the portion where each piezoelectric element is provided.

[Explanation of Examples]

FIG. 3 is a schematic perspective view of one embodiment of the present invention. The piezoelectric pressure distribution sensor 10 of this embodiment is constructed using a shield case made of a conductive material such as stainless steel. A rectangular opening 11a is formed in the shield case 11. As will be described later, the portion exposed within the opening 11a is configured to come into contact with the object to be measured, and its pressure distribution is detected.

The internal structure of the above embodiment will be described in detail with reference to the exploded perspective view of FIG.

A pressure distribution sensor is constructed within a case composed of a base member 12 made of a rigid material such as stainless steel, and the shield case 11 described above.

On the base member 12, positioning bins 12a and 12b that protrude upward are provided.
a and 12b are provided to position each member, which will be described later, placed on the base member 12.

A rectangular protrusion 12 cm 12 f that protrudes upward is formed at a portion of the corner of the base member 12 . Projection part 1
A screw hole 13 is formed in the side surface of 2 cm 121. The screw hole 13 is inserted into the shield case 11 when each member is stored on the base member 12 and covered with the shield case 11.
is provided for fixing to the base member 12 with screws 14.

A flexible substrate 15 is directly above the base member 12.
Ri is placed. The flexible substrate 15 has positioning holes 15a and 15 inserted into the positioning bins 12a and 12b.
b is formed. Further, although not shown accurately in FIG. 4, a predetermined wiring pattern is formed on the upper and lower surfaces of the flexible substrate 15, and a chip-type capacitor is placed in the portion indicated by the imaginary line A. , an FET is mounted in the part indicated by the imaginary line B. Furthermore, piezoelectric elements, which will be described later, are placed in four rectangular areas indicated by imaginary lines C. The electrode formed on the end face of the piezoelectric element and the wiring pattern on the flexible substrate 15 are configured to be electrically connected.

Reference numeral 16 indicates a cable, which is connected to an input/output pad provided on the flexible substrate 15.

A resin frame 17 having a rectangular planar shape is placed on the flexible substrate 15 . The resin frame 17 includes four piezoelectric element storage through holes 17a to 17d, a positioning bin L2a,
Through-holes 17e and 17f are formed through which the parts 12b are inserted. This resin frame 17 is provided to accommodate each of the four piezoelectric elements 18 to 21. However, the thickness of the resin frame 17 is made thinner than the thickness of the piezoelectric elements 18-21.

The piezoelectric elements 18 to 21 each have a structure in which electrodes are provided on the upper and lower end surfaces, and are made of piezoelectric ceramics or piezoelectric single crystals that generate electric charges due to the piezoelectric effect when pressure is applied in the vertical direction. . Note that as the piezoelectric ceramic or piezoelectric single crystal, one having relatively high rigidity is used.

An elastic sheet 22 having an opening 22a is placed on the resin frame 17. The opening 22a is formed in a size that exposes the upper end surfaces of the piezoelectric elements 18 to 21. The elastic sheet 22 is made of an elastic material such as synthetic rubber, for example.

A second flexible substrate 23 serving as a pressure sheet is placed on the elastic sheet 22. Flexible board 23
A rectangular through hole 23a is formed in the center. The through hole 23a is formed by a fitting protrusion 1 formed on the upper surface of the resin frame 17.
The shape and size are such that 7g can be pushed through. The flexible base Fi,'' 23 is positioned by the through hole 23a and the fitting protrusion 17g.

A predetermined wiring pattern is formed on the lower surface of the flexible substrate 23, and the piezoelectric element 1 is connected using a conductive adhesive or the like.
Electrodes 8 to 21 on the upper end surfaces and the wiring pattern are electrically connected.

On the upper surface of the second flexible substrate 23, first to fourth height adjustment members 24 to 27 made of a material whose thickness can be reduced by machining, such as stainless steel, are connected to each other by a connecting portion 28. The connected height adjustment plate 30 is fixed.

The first to fourth height adjustment members 24 to 27 have a rectangular planar shape, and are placed on the upper end surfaces of the piezoelectric elements 18 to 21, with the flexible substrate 23 interposed therebetween, on opposing sides. The height adjusting members 24 to 27 do not necessarily need to be connected to each other by the connecting member 2 as shown in the figure, and may be provided independently.

Place each of the above-mentioned components on the base member 12! The piezoelectric pressure distribution sensor 10 shown in FIG. 3 is obtained by placing the shield case 11 on the base member 12 with the necessary parts fixed, and fixing the shield case 11 to the base member 12 with the screws 14.

Next, the characteristic structure of this embodiment will be explained with reference to the enlarged sectional view of FIG.

FIG. 1 is an enlarged cross-sectional view showing a main part along line 1-1 in FIG. 3. FIG. In the assembled state, the piezoelectric element 1
A second flexible substrate 23 having an electrode pattern 23b formed on its lower surface is placed above 8.20.

This electrode pattern 23b is attached to the electrodes 18a and 20a on the upper end surface of the piezoelectric element 18.20 using a conductive adhesive (not shown).
electrically connected to.

On the lower end surface side of the piezoelectric element 18.20, the wiring pattern 15d on the first flexible substrate 15 placed on the base member 12 and the electrode 18b on the lower end surface of the piezoelectric element 18.20
, 20b are fixed with a conductive adhesive (not shown).

Above each piezoelectric element 18, 20, height adjusting members 24 and 26 are fixed to the opposing outer surface portions via a second flexible substrate 23 as a pressure sheet.

Therefore, in this embodiment, after assembling each member shown in FIG. 4 or before covering with the shield case 11, the height adjusting members 24, 25 are ground by machining, so that the piezoelectric element 18. The heights of the surfaces that come into contact with the object to be measured can be made equal in the portion where the device 20 is disposed. Piezoelectric element 19.21 not shown in FIG.
In the same way, the height adjusting members 25 and 27 can be ground to reduce the thickness of the part where the piezoelectric element is provided, so that the height of the surface that comes into contact with the object to be measured in the part where the piezoelectric element is provided can be reduced. can be made uniform.

Therefore, the base member 12, the first flexible substrate 15
Even if the thickness of each constituent member such as the second flexible substrate 23 is not uniform partially, by machining to reduce the thickness of the height adjustment members 24 to 27, a plurality of piezoelectric It is possible to make the height of the portion where the elements 18 to 21 are provided constant. Therefore, it becomes possible to accurately detect the pressure distribution based on the contact of the object to be contacted.

In the conventional piezoelectric pressure distribution sensor, control lines and reading lines are drawn out from a plurality of piezoelectric elements arranged in a matrix, and detection is performed by electrically switching them. However, in the above embodiment, two piezoelectric elements ×2 elements, which is a relatively small number of elements.

Therefore, as shown in FIG. 5, a detection circuit can be configured independently for each piezoelectric element 18-21. That is, as shown in FIG. 5, a capacitor C, a FET 31, an integrating circuit 32, and a peak hold circuit 33 are configured for one piezoelectric element 18, 19, 20, or 21, and a gate circuit 34 connects each piezoelectric element. By switching the corresponding detection sections, detection outputs can be taken out independently. Note that 35 indicates a peak hold/reset circuit.

However, the detection circuit shown in FIG. 5 is not essential to the present invention, and is configured so that control lines and read lines are drawn out from a plurality of piezoelectric elements and electrically switched for detection, as in the conventional example. You may.

〔Effect of the invention〕

As described above, in the present invention, a height adjusting member is formed corresponding to each piezoelectric element at a position opposite to the end face of the piezoelectric element opposite to the base member and the front and back sides with the pressure sheet interposed therebetween. Since the height adjusting member is made of a material whose thickness can be reduced by machining, the height adjusting member is machined to reduce the thickness of each piezoelectric element after the sensor is assembled or during the assembly process. The height of the surface that comes into contact with the object to be measured can be made uniform.

Therefore, even if the thickness of other members such as the base member and the pressure sheet is non-uniform, it is possible to accurately detect the pressure distribution caused by contact with the object to be contacted.

Therefore, it is possible to realize a highly accurate and highly sensitive pressure distribution sensor that takes advantage of the characteristics of the piezoelectric pressure sensor, which has small distortion with respect to applied force and can operate even with very small distortion.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of a main part of an embodiment of the present invention.
FIG. 2 is a partially cutaway enlarged sectional view for explaining a conventional example, FIG. 3 is a schematic perspective view of an embodiment of the present invention, and FIG. FIG. 3 is an exploded perspective view of the embodiment, and FIG. 5 is a circuit diagram for explaining an example of the detection circuit of the embodiment of FIG. In the figure, 10 is a piezoelectric pressure distribution sensor, 12 is a base member, 18 to 21 are piezoelectric elements, I8 a18b, 20
Reference numerals a and 20b indicate electrodes provided on the piezoelectric element, 23 indicates a second flexible substrate as a pressure sheet, and 24 to 27 indicate height adjustment members. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A base member; a piezoelectric element group having a plurality of piezoelectric elements arranged in a matrix on the base member; and an end face of the plurality of piezoelectric elements on the side opposite to the base member. a pressure sheet arranged as shown in FIG. A piezoelectric pressure distribution sensor, comprising: a pressure adjustment member.