JPH071212B2 - 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, the present invention relates to a structure provided with a structure that eliminates variation in thickness in a portion provided with a plurality of piezoelectric elements.

[Conventional technology]

Japanese Patent Laid-Open No. 62-297735 discloses a sensor in which a plurality of piezoelectric elements are arranged in a matrix to detect a contact pressure distribution.

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

The structure of the above prior art will be described with reference to FIG.
A wiring pattern 2 is formed on the base member 1.
Piezoelectric elements 3 are mounted on predetermined positions of the wiring pattern 2, respectively. On the upper and lower end surfaces of the piezoelectric element 3,
A pair of electrodes (not shown) are formed, and the lower electrodes are electrically connected to the wiring pattern 2.

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

In the above structure, when an object contacts 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, the pressure distribution based on the contacted object can be detected by detecting the electric charge generated in each piezoelectric element 3 by the piezoelectric effect by using the detection device (not shown).

[Technical problem to be solved by the invention]

In the conventional piezoelectric pressure distribution sensor, it is required that the heights of the portions where the plurality of piezoelectric elements 3 are provided are uniform as a prerequisite for accurately detecting the pressure distribution based on the contacted object. .

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 element 3, variations in the thickness of the adhesive layer, and the like, in the portion where each piezoelectric element 3 is provided. There was no choice but to vary the thickness of the sensor.

The piezoelectric type pressure distribution sensor has a small distortion of the piezoelectric element 3 with respect to the applied pressure, and therefore can constitute a highly sensitive sensor having a very small distortion as a whole. In spite of the,
In the conventional structure, it is difficult to suppress the variation in the thickness of the portion where each piezoelectric element is provided, so it is difficult to take advantage of such 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 in a portion where a plurality of piezoelectric elements are provided highly uniform, and therefore to detect the pressure distribution with high sensitivity and with high accuracy. It is to provide a piezoelectric pressure distribution sensor to be obtained.

[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 is arranged so as to contact the end faces of the plurality of piezoelectric elements opposite to the base member. A plurality of height adjusting members are attached to the outer surface portions of the pressure sheet that face the front and back sides of the end surface of each piezoelectric element opposite to the base member with the pressure sheet interposed therebetween. The height adjusting member is made of a material whose thickness can be reduced by machining.

In the base member bottom surface area where the height adjusting member is provided, a height adjusting reference surface area is formed so as to project downward from the remaining portion of the base member bottom surface through a step.

[Operation] Since the plurality of height adjusting members are made of a material whose thickness can be reduced by machining, it is possible to adjust the thickness of the height adjusting members provided corresponding to each piezoelectric element portion. This makes it possible to make the height of the surface in contact with the object to be measured uniform.

Further, when adjusting the thickness of the height adjusting member, since the height adjusting reference surface region of the base member is formed,
Even if the base member is warped during machining or due to heat applied, since the warp in the reference surface region is relatively small compared to the warp amount of the entire base member, each piezoelectric element is provided. The sensor thickness in the existing portion can be made uniform with high accuracy.

[Explanation of Examples]

FIG. 3 shows a pressure distribution sensor to which a structure for making the sensor thickness uniform in the portion where the above-mentioned piezoelectric element is provided is added, though it is not publicly known. Here, a shield case 11 made of a conductive material such as stainless steel,
A case is composed of the base member 12 made of a rigid material such as stainless steel.

A substrate 13 having conductive patterns 13a and 13b formed on both surfaces thereof is arranged on the base member 12. A plurality of piezoelectric elements 14 and 15 are arranged on the substrate 13. Electrodes 14a, 14b, 15a, 15b are formed on the upper and lower end surfaces of the piezoelectric elements 14, 15, respectively. The piezoelectric elements 14 and 15 are housed in the frame body 16 and are restricted to the positions shown by the filled elastic resin 17.

A pressure sheet 18 is arranged above the piezoelectric elements 14 and 15. Height adjusting members 19 and 20 are fixed to the upper surface of the pressure sheet 18 at positions facing the piezoelectric elements 14 and 15, respectively.

The height adjusting members 19 and 20 are made of a material such as stainless steel whose thickness can be reduced by machining.

Therefore, in the configuration of FIG. 3, after the components are assembled in the case in the illustrated state, the bottom surface of the base member 12 is used as a reference surface to raise the piezoelectric elements 14 and 15 above. By machining the height adjusting members 19 and 20, it is possible to make the heights of the surfaces of the portions where the piezoelectric elements 14 and 15 are provided in contact with the contacted object uniform.

In the structure shown in FIG. 3, the bottom surface of the base member 12 is ground over the entire area, and is used as a reference surface for achieving accuracy in thickness adjustment by machining of the height adjusting members 19 and 20.

However, during processing of the height adjusting members 19 and 20, or when warping occurs in the base member 12 due to heat or the like, the reference surface becomes unstable, and processing accuracy of the height adjusting members 19 and 20,
As a result, there is a problem in that the accuracy of the sensor thickness cannot be ensured.

A piezoelectric pressure distribution sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a schematic perspective view of one embodiment of the present invention. The piezoelectric type pressure distribution sensor 30 is constructed by using a shield case 31 made of a conductive material such as stainless steel. A rectangular opening 31a is formed in the shield case 31. As will be described later, the exposed portion of the opening 31a is brought into contact with the object to be measured, and the pressure distribution thereof 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 formed in a case composed of a base member 32 made of a rigid material such as stainless steel and the shield case 31 described above.

The feature of this embodiment is that the bottom surface of the base member 32 has a step 32
The height adjusting reference area 32b is formed so as to protrude downward from the remaining bottom surface area via a. The height adjusting reference surface area 32b is formed in an area where a height adjusting member (described later) arranged above is provided. The function and effect of the height adjusting reference plane area 32b will be described later with reference to FIG.

On the upper surface side of the base member 32, rectangular protrusions 32c to 32f are formed at corners. Screw holes 33 are formed on the side surfaces of the protrusions 32c to 32f. The screw hole 33 is provided to fix the shield case 31 to the base member 32 with the screw 34 in a state where the members are housed on the base member 32 and the shield case 31 is covered.

A flexible substrate 35 is placed directly above the base member 32. Although not shown accurately in FIG. 5, predetermined conductive patterns are formed on the upper surface and the lower surface of the flexible substrate 35, and the chip type capacitor 35a is arranged in the portion indicated by the imaginary line A. , F in the part indicated by imaginary line B
ET35b is installed.

Further, piezoelectric elements, which will be described later, are placed in the four rectangular regions indicated by the imaginary line C. Then, the electrodes formed on the end faces of the piezoelectric elements and the wiring patterns on the flexible substrate 35 are electrically connected.

Reference numeral 36 denotes a cable, which is electrically connected to the input / output pad provided on the flexible substrate 35.

On the flexible board 35, a resin frame 37 having a rectangular plan shape is used.
Is placed. In this resin frame 37, four piezoelectric elements 38-
41 are stored respectively. Although not shown in FIG. 5, an elastic resin is injected and solidified in the resin frame 37 to alleviate the transmission of strain between the piezoelectric elements 38 to 41.

Each of the piezoelectric elements 38 to 41 has a structure in which electrodes are provided on the upper and lower end surfaces, and is made of a piezoelectric ceramic or a piezoelectric single crystal that generates an electric charge by a piezoelectric effect when pressure is applied in the vertical direction.

An elastic sheet 42 having an opening 42a is placed on the resin frame 37. The opening 42a is formed in such a size that it is exposed on the other upper surface of the piezoelectric elements 38 to 41. The elastic sheet 42 is made of an elastic material such as synthetic rubber.

On the elastic sheet 42, the second flexible substrate 43 as a pressure sheet is placed. Second flexible board 43
A predetermined wiring pattern is formed on the lower surface of the electrodes, and the electrodes on the upper end surfaces of the piezoelectric elements 38 to 41 are electrically connected to the wiring pattern using a conductive adhesive or the like.

First to fourth height adjusting members 44 to 47 made of a material such as stainless steel whose thickness can be reduced by machining are fixed to the upper surface of the second flexible substrate 43.

The first to fourth height adjusting members 44 to 47 are arranged at the portions facing the upper and lower surfaces of the piezoelectric elements 38 to 41 with the flexible substrate 43 interposed therebetween. The reference surface region 32b of the base member 32 described above is formed below the portion where the height adjusting members 44 to 47 are provided.

1 and 3 by mounting the above-mentioned constituent members on the base member 32 and covering the shield case 31 with the necessary portions fixed, and fixing the shield case 31 to the base member 32 with the screws 34. The piezoelectric type pressure distribution sensor shown in can be obtained.

Next, the height adjustment, that is, the adjustment of the sensor thickness in the piezoelectric type pressure distribution sensor of this embodiment will be described.

Referring to FIG. 1, above the piezoelectric elements 38, 40, height adjusting members 44, 46 are fixed to the outer surface portions facing the front and back via a second flexible substrate 43 as a pressure sheet. There is.

Therefore, by assembling the height adjusting members 44 and 46 by machining after assembling the members shown in FIG. 5 or before covering the shield case 31, the portions where the piezoelectric elements 38 and 40 are arranged. The heights of the surfaces in contact with the object to be measured can be made equal. Piezoelectric element not shown in FIG.
Even in the portions where 39 and 41 are provided, the heights can be similarly made uniform by grinding the height adjusting members 45 and 47.

By the way, in the structure of FIG. 3, there is a problem that the sensor thickness cannot be made uniform with high accuracy by the height adjusting member when the warp of the base member 12 occurs.
Since the base member 32 is provided with the reference surface region 32b, it is possible to eliminate such a variation in the sensor thickness due to the deformation of the base member.

That is, suppose now that the base member 32 is deformed from the state shown in FIG. 6 (a) as shown in FIG. 6 (b) due to the force applied during machining and the low heat of the surroundings. View. In this case, the reference surface area 32b provided on the bottom surface of the base member 32 is projected below the remaining bottom surface area 32c, and therefore, compared with the maximum warpage amount x of the entire bottom surface,
The warp amount y of the reference surface region 32b becomes much smaller. Therefore, even if the base member 32 is deformed as shown in FIG. 6B, the amount of warpage in the reference surface region is very small, so that the reference surface region 32b is used as a reference surface for height adjustment. It is possible to grind 44 to 47 with high accuracy and thereby to make the height of the surface of the portion where the piezoelectric element is provided in contact with the measured object highly uniform.

Therefore, the pressure distribution based on the contact of the contacted object can be accurately detected.

In the above embodiment, four independent height adjusting members 44 to 47 are shown as the height adjusting member, but the height adjusting members are integrated by connecting them with a thin connecting portion or the like. Good.

〔The invention's effect〕

In the present invention, a height adjusting member is formed corresponding to each piezoelectric element at a position facing the front surface and the back surface of the end surface of the piezoelectric element opposite to the base member via the pressure sheet. Since the adjustment member is made of a material whose thickness can be reduced by machining, the height adjustment member can be processed to contact the object to be measured in each piezoelectric element after the sensor is assembled or during the assembly process. The heights of the surfaces to be covered can be made uniform.

Moreover, according to the present invention, in the portion where the height adjusting member is provided, since the reference surface region that is projected downward through the step is formed on the bottom surface of the base member, the processing of the height adjusting member described above is performed. Even if the base member is warped or deformed at this time, the height adjusting member can be machined using the height adjusting reference surface area as a reference, so that the height of the surface to be contacted with the object to be measured is increased. The accuracy can be made uniform.

Therefore, the height of the sensor surface in contact with the object to be measured can be made uniform with high accuracy, so that the piezoelectric pressure distribution sensor capable of accurately detecting the pressure distribution can be obtained.

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 distribution sensor that has a small distortion with respect to the applied pressure and can operate even with a very small distortion.

[Brief description of drawings]

FIG. 1 is a sectional view of a piezoelectric pressure distribution sensor according to an embodiment of the present invention, FIG. 2 is a partially cutaway enlarged sectional view for explaining a conventional piezoelectric pressure distribution sensor, and FIG. 3 is a sectional view of the present invention. FIG. 4 is a schematic perspective view of an embodiment of the present invention, FIG. 5 is an exploded perspective view of the embodiment shown in FIG. 4, and FIG. 6 ( 8A and 8B are side views for explaining the function and effect of the reference surface area provided on the base member of FIG. In the figure, 30 is a piezoelectric pressure distribution sensor, 32 is a base member, 32a is a step, 32b is a reference surface area, 32c is the remaining area of the bottom surface, 38 to 41 are piezoelectric elements, and 43 is a second pressure sheet.
Flexible substrates, 44 to 47 are height adjusting members.

Claims (1)

[Claims] 1. A base member, a piezoelectric element group having a plurality of piezoelectric elements arranged in a matrix on the base member, and an end surface of the plurality of piezoelectric elements opposite to the base member. And a plurality of heights made of a material whose thickness can be reduced by machining, which are attached to the portions of the piezoelectric elements facing each other through the pressure sheet and the end surface of each piezoelectric element. An adjusting member, and a height adjusting reference surface area protruding downward through a step and a remaining portion of the base member bottom surface is formed in the base member bottom surface area on which the height adjusting member is provided. Piezoelectric pressure distribution sensor characterized in that