JP2007316045A - Pressure detection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure detection element that achieves high detection accuracy by reducing the temperature dependence of a response current generated when external pressure is exerted. <P>SOLUTION: A reduction in response voltage at low temperature is made by a flexible mode principally involving a deformation of a flexible pressure-sensitive body. Specifically, in the exterior of a flexible pressure-sensitive body 11 and an electrode 12, a protection layer 13 is formed wherein a cavity is provided inside. The cavity makes it easy for the protection layer 13 to bend downward when external pressure Po is applied. This causes the flexible pressure-sensitive body 11 to greatly bend downward. For this reason, when the external pressure Po is applied, a wider region is distorted by promotion of the flexible mode as compared with a compressed mode. This suppresses a reduction in response voltage especially at low temperature, thereby reducing the temperature dependence of the response voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure detecting element that detects pressure from the outside using a flexible pressure sensitive body.

  Conventionally, there is such a pressure detection element as shown in FIG. As shown in the cross-sectional view of FIG. 14, the electrode 2 is formed on the upper and lower sides of the flexible pressure-sensitive body 1, and the protective layer 3 covers the surface. In FIG. 14, the direction of remanent polarization in the flexible pressure-sensitive body 1 is not shown. Usually, in order to form a polarization by applying a high voltage between the electrodes 2, the direction is perpendicular to the surface of the electrode 2. Residual polarization is formed.

  As the flexible pressure-sensitive body 1, a composite in which a piezoelectric ceramic powder such as lead titanate or lead zirconate titanate is added to synthetic rubber or synthetic resin is used. The electrode 2 is configured by bonding a metal foil such as copper, aluminum, or gold to the flexible pressure-sensitive body 1 with an adhesive or the like, or depositing the above metal.

  When dynamic pressure is applied to the pressure detection element from the outside, the flexible pressure-sensitive body 1 is strained with acceleration, and at the same time, a voltage is generated due to the piezoelectric effect. This voltage is transmitted via the two electrodes 2. The dynamic pressure is detected by measuring the response voltage.

  Moreover, there existed a cable-shaped thing as shown in FIG. 15 as a conventionally known pressure detection element (for example, refer patent document 1). 15A shows a cross section in the longitudinal direction of the cable, and FIG. 15B shows a cross section taken along the line AA in FIG. Specifically, the inner electrode 4 is formed at the center, the flexible pressure-sensitive body 1 is formed around the inner electrode 4, and the outer electrode 5 and the protective layer 3 are sequentially formed on the outer side. In FIG. 15, the direction of remanent polarization in the flexible pressure-sensitive body 1 is not shown, but normally, in order to form a polarization by applying a high voltage between the internal electrode 4 and the external electrode 5, the internal electrode 4 Thus, residual polarization is formed radially from the external electrode 5 to the external electrode 5.

  For the flexible pressure-sensitive body 1 in FIG. 15, a composite similar to the layered flexible pressure-sensitive body is used. For the internal electrode 4, a linear conductive material in which a conductor such as metal is linear is used. Further, the external electrode 5 is formed by applying a conductive paint such as a silver-based rubber paint on the surface of the flexible pressure-sensitive body 1. The pressure is detected by measuring a response voltage generated due to the strain accompanied by the acceleration due to the application of the dynamic pressure, similarly to the pressure detecting element using the sheet-like flexible pressure sensitive body.

  Here, the definition regarding the dynamic pressure used above and also a static pressure is demonstrated. The dynamic pressure is a pressure that is not balanced with a stress corresponding to the dynamic pressure, and as a result, an acceleration is generated in an object to which the dynamic pressure is applied.

  On the other hand, the static pressure is a pressure that is completely balanced with the stress corresponding to the static pressure, and as a result, no acceleration is generated in the object to which the static pressure is applied. For this reason, a static pressure is not detected by the conventional technique which measures a voltage change using said flexible pressure sensitive body.

Unless otherwise specified, the pressure used below means the above-described dynamic pressure that can be detected by a pressure detection element using a flexible pressure sensitive body.
JP-A-62-230071

  However, the conventional pressure detecting element has a temperature characteristic in a response voltage generated by an external pressure, and particularly when the pressure is detected at a low temperature, the accuracy at a low temperature is deteriorated. Had.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a pressure detection element with high detection accuracy by reducing the temperature dependence of a response voltage generated by pressure application from the outside.

  In order to solve the above-described conventional problems, the pressure detection element of the present invention has a configuration in which a portion formed only of air is provided inside the protective layer that protects the flexible pressure-sensitive body and the electrode. . By having a protective layer formed of only air and having a flexible portion, the flexible pressure-sensitive body is greatly bent due to deformation of the flexible protective layer when pressure is applied from the outside.

  As described above, the deformation in the bending mode increases, so that even when the flexible pressure-sensitive body is cured at a low temperature, the portion where the distortion occurs is increased, thereby increasing the response voltage and suppressing the decrease in the response voltage. Is.

  Moreover, the pressure detection element of this invention has a structure where the elastic modulus of the perpendicular direction of the protective layer which protects a flexible pressure sensitive body and an electrode is larger than the elastic modulus of a horizontal direction.

  Since the elastic modulus in the vertical direction is larger than the elastic modulus in the horizontal direction, when pressure is applied from the vertical direction, deformation in the compression mode is unlikely to occur, and conversely, deformation in the bending mode is likely to occur. At a low temperature, the flexible pressure-sensitive body becomes hard and distortion in deformation in the compression mode is suppressed. However, a decrease in response voltage is suppressed by distortion due to deformation in the bending mode.

  The pressure detection element of the present invention enables accurate pressure detection even in an environment with a large temperature change.

  A pressure detection element according to a first aspect of the invention protects a flexible pressure-sensitive body having remanent polarization, a plurality of electrodes configured to sandwich the flexible pressure-sensitive body, and the flexible pressure-sensitive body and the electrodes. And a protective layer that includes a portion formed only of air inside the protective layer.

  Since there is a part formed only by air, when pressure is applied from the outside, the flexible pressure-sensitive body is easily deflected, so that a decrease in the generated voltage at a low temperature is suppressed and the environmental temperature changes. Accurate pressure detection is possible.

  According to a second invention, in the first invention, a portion formed only of air is constituted by bubbles.

  Since the air portion is formed as an aggregate of bubbles, the whole becomes uniform, and when pressure is applied to the pressure detection element from the outside, even if the direction of pressure application is different, the flexible pressure sensitive body The change in pressure applied to the is small, and more stable pressure detection is possible.

  According to a third invention, in the first or second invention, a portion formed only from air is formed to be lower in the lower portion than in the upper portion of the flexible pressure sensitive body.

  When the pressure is applied from the outside to the lower part, the part formed only from air increases in the lower part of the flexible pressure sensitive body, and the deflection to the lower part of the flexible pressure sensitive body increases. A decrease in the generated voltage at a low temperature is further suppressed, and a highly accurate pressure detection is possible even when the environmental temperature changes.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a flexibility increasing layer is provided below the protective layer.

  By having the flexibility increasing layer at the lower part of the protective layer, when pressure is applied from the outside to the lower part, the deflection to the lower part of the flexible pressure-sensitive body increases, and the generated voltage decreases at a lower temperature. Even if the environmental temperature changes, it is possible to detect the pressure with high accuracy.

  According to a fifth aspect of the present invention, there is provided a flexible pressure-sensitive body having remanent polarization, a plurality of electrodes configured to sandwich the flexible pressure-sensitive body, and a protective layer that protects the flexible pressure-sensitive body and the electrodes. The elastic modulus in the vertical direction of the protective layer is larger than the elastic modulus in the horizontal direction.

  When the elastic modulus in the vertical direction is larger than the elastic modulus in the horizontal direction, when pressure is applied from the outside to the bottom in the vertical direction, deformation in the compression direction in the vertical direction is suppressed, and deformation in the bending mode is suppressed. Therefore, a decrease in response voltage at a low temperature is further suppressed, and highly accurate pressure detection is possible even when the environmental temperature changes.

  In a sixth aspect based on the fifth aspect, the thickness of the side portion of the protective layer is made larger than the thickness of the upper and lower portions.

  By simply changing the shape of the side of the protective layer to be thicker than the thickness of the upper and lower parts, the elastic modulus can be easily controlled, more easily suppressing deformation in the compression mode and promoting deformation in the bending mode, Accurate pressure detection is possible even when the ambient temperature changes.

  According to a seventh invention, in the fifth or sixth invention, the elastic modulus of the material forming the side portion of the protective layer is larger than the elastic modulus of the material forming the upper portion and the lower portion. By increasing the elastic modulus of the material that forms the side of the protective layer, deformation in the compression mode in the vertical direction is suppressed, and the bending mode is the main feature, so highly accurate pressure detection is possible even when the ambient temperature changes. Possible. In addition, since a material having a high elastic modulus is used for the side portion, the thickness of the side portion for obtaining a necessary elastic modulus can be adjusted, and the effect of increasing the degree of freedom in dimensional design can be obtained.

  In an eighth invention according to any one of the fifth to seventh inventions, a compression suppressing layer is provided on a side portion of the protective layer.

  By having a compression suppression layer on the side of the protective layer, deformation of the compression mode in the vertical direction can be more effectively suppressed, and deformation of the bending mode can be mainly performed. Even with this, highly accurate pressure detection is possible. In addition, since the compression suppression layer is formed in the final step after forming the protective layer and the suppression of deformation in the compression mode can be adjusted, an effect of increasing the degree of freedom in design can be obtained.

  According to a ninth invention, in any one of the first to eighth inventions, the protective layer includes a bending width expanding material.

When the protective layer includes the bending width expanding material, when the pressure is applied from the outside, the entire protective layer is pulled by the bending width expanding material, so that the bending width is widened and the deformation of the bending mode is further promoted. The Thus, the response voltage drop at a low temperature is further suppressed, and the pressure can be detected with high accuracy even when the environmental temperature changes.

  According to a tenth aspect of the present invention, in any one of the first to ninth aspects of the invention, a bending width expanding layer is included in an upper part or a lower part of the protective layer.

  Since the protective layer includes the bending width expanding layer, the area where the flexible pressure sensing element bends becomes wider when pressure is applied from the outside, and the decrease in response voltage at low temperatures is further suppressed. The pressure can be detected with high accuracy even if the environmental temperature changes. In the final step after forming the protective layer, the bending width expanding layer is formed and adjustment of the promotion of deformation in the bending mode is possible, so that an effect of increasing the degree of freedom in design can be obtained.

  In an eleventh aspect of the invention according to the tenth aspect of the invention, a bending width expanding layer is included only in the lower portion of the protective layer.

  By including the bend width expanding layer only in the upper part of the protective layer, the bend to the lower part is increased, and the effect of further suppressing the decrease in the response voltage at a low temperature is obtained.

  In a twelfth aspect of the invention according to any one of the first to tenth aspects of the invention, a maximum portion of elastic modulus is provided in the longitudinal direction of the protective layer. By having the maximum elastic modulus in the longitudinal direction of the protective layer, compression is suppressed at the maximum elastic modulus, the bending mode becomes dominant as a whole, and the effect of suppressing the response voltage drop at low temperatures is obtained.

  In a thirteenth aspect, in the twelfth aspect, a maximum part of the elastic modulus is formed by forming a compression suppression layer in a part of the protective layer in the longitudinal direction. By doing so, an effect of easily forming the maximum portion of the elastic modulus can be obtained.

  A fourteenth aspect of the invention is a method of applying a pressure from the outside to be detected to the maximum part of the elastic modulus in the longitudinal direction of the protective layer. By applying the pressure to be detected to the portion having a high elastic modulus, the compression mode is suppressed, and the bending mode becomes dominant due to the bending of the other portions, and the effect of suppressing the response voltage drop at a low temperature is obtained. Further, when the pressure to be detected is large, there is an effect of suppressing plastic deformation and damage to the sensor.

(Embodiment 1)
Prior to the description of a specific embodiment, the experimental results that led to the present invention will be described with reference to FIG.

  FIG. 1 (a) is a cross-sectional view showing a state in which a rigid body is placed under the pressure detection element and pressure is applied with an indenter from above, and FIG. 1 (b) is a sponge placed under the pressure detection element, It is sectional drawing which showed a mode that a pressure was applied with an indenter from the upper part. FIG. 1 (c) qualitatively shows the temperature dependence of the response voltage V corresponding to (a) and (b), and describes the main deformation modes at that time.

  In FIG. 1A, since the pressure detection element 14 is placed on a rigid body, the pressure detection element 14 hardly bends, and because of the indenter, the compression mode deformation occurs and the flexible pressure-sensitive body 11 is distorted. Occurs. On the other hand, in FIG. 1B, since the sponge is placed under the pressure detecting element 14, the flexible pressure sensitive body 11 sinks greatly in the sponge, and the compression mode distortion generated in the center portion. In addition, distortion due to bending deformation occurs in a wider range.

The response voltage V corresponding to FIG. 1A greatly decreases at a low temperature as shown in the compression mode of FIG. This is presumably because the flexible pressure-sensitive body 11 becomes hard at low temperatures, and distortion due to deformation in the compression mode hardly occurs in the flexible pressure-sensitive body 11. On the other hand, the inventors found that in the case of FIG. 1B, the decrease in the response voltage V is suppressed as shown in the compression + deflection mode of FIG. This is because, when the flexible pressure-sensitive body 11 becomes hard at low temperatures, the distortion of the deformation in the compression mode is suppressed, but on the contrary, the distortion of the deformation in the bending mode becomes a distorted region as the flexible pressure-sensitive body 11 becomes hard. This is thought to be due to the increase in response voltage.

  Therefore, by suppressing the deformation in the compression mode and promoting the deformation in the bending mode, it is possible to suppress a decrease in the response voltage due to the curing of the flexible pressure sensitive body 11 at a low temperature. This is the gist of the present invention.

  In the following, a specific configuration of the present invention will be guided in accordance with the above-mentioned gist. The description will be divided into (1) a configuration that promotes deformation in the bending mode and (2) a configuration that suppresses deformation in the compression mode. In this embodiment, (1) a configuration that promotes deformation in the bending mode will be described. I do.

  FIG. 2 is a diagram for explaining the promotion of deformation in the bending mode by the cross sections of the flexible pressure-sensitive body 11 and the electrode 12. In FIG. 2A, the amount of bending is indicated by a bending width L1 and a downward bending depth L2. There are two possible patterns for promoting deformation in the bending mode. One is a pattern in which the deflection width L1 extends to L1 + α as represented by the change from FIG. The other is a pattern in which the downward deflection depth L2 increases to L2 + β as represented by the change from FIG.

  In the present embodiment, a configuration for realizing the latter pattern of the two patterns will be described with reference to FIGS.

  First, an example of the configuration of the present embodiment will be described with reference to FIG. 3A and 3B are cross-sectional views of the linear pressure detection element 14 having a layered structure according to the present embodiment. FIG. 3A is a longitudinal cross-sectional view, and FIG. 3B is a cross-sectional view of FIG. The cross section in the BB line position is represented.

  A cavity is formed in the protective layer 13 as a portion formed only of air. Since the cavity is formed, the protective layer 13 is easily deformed, and when an external pressure Po is applied, as shown in FIG. The bending L2 increases in the direction opposite to the application direction), and the deformation in the bending mode is promoted. Thus, even when the flexible pressure-sensitive body 11 is cured at a low temperature, the rate of deformation in the bending mode increases, so that an effect of suppressing a decrease in response voltage is obtained.

  Since such a pressure detection element can detect a pressure with high accuracy even when the environmental temperature to be used changes, it is preferably used particularly for an application used in an outdoor environment or an environment close to the outdoor environment. For example, it is particularly suitable for security purposes, such as installation outside a house such as a balcony or fence to detect intruders. Also, it can be used for detecting the trapping of people or objects in the door of an automobile, or for detecting the contact with the door handle to unlock the door just by touching the door handle. Is suitable.

  In addition, although it demonstrates regarding the another structure of this Embodiment below, about the same structure, there exists the same effect, The same code | symbol was attached | subjected and description was abbreviate | omitted. Therefore, only different parts will be described.

FIG. 4 illustrates another flexible pressure-sensitive body of the present embodiment, and represents a cross-sectional view of a linear pressure detection element 14 having a layered structure. Specifically, FIG. 4A shows a cross section in the longitudinal direction, and FIG. 4B shows a cross section taken along the line CC in FIG. 4A. Bubbles are formed in the protective layer 13 as a portion formed only from air. Due to the formation of bubbles, FIG.
As in the case of FIG. 2, the deformation of the protective layer 13 is facilitated, and when an external pressure Po is applied, as shown in FIG. 2 (c), the lower portion (opposite to the external pressure Po application direction). The deflection L2 increases to the side portion), the deformation in the bending mode is promoted, and the effect of suppressing the decrease in the response voltage at a low temperature is obtained. In the present specification, the lower part and the upper part define the direction in which external pressure is applied as the upper part and the opposite direction as the lower part.

  By forming a large number of fine bubbles in place of the cavities, the flexure generated in the flexible pressure-sensitive body 11 becomes more uniform, and even with respect to the angle or place shift where the external pressure Po is applied, An effect of obtaining a more stable response voltage can be obtained.

  As the protective layer 13 containing air bubbles, foams such as thermoplastic elastomer and vulcanized rubber can be suitably used. It is preferable that the bubbles of the foam are continuous because the elastic modulus is low and the foam is easily deformed with respect to the external pressure Po.

  FIG. 5 illustrates a flexible pressure-sensitive body having another configuration according to the present embodiment, and represents a cross-sectional view of a linear pressure detection element 14 having a layered structure. Specifically, FIG. 5A shows a cross section in the longitudinal direction, and FIG. 5B shows a cross section taken along the line DD in FIG. 5A. As in FIG. 4, bubbles are formed in the protective layer 13 as a portion formed only of air, but the difference is in the lower part of the protective layer 13 (on the side opposite to the side to which the external pressure Po is applied). That is, bubbles are formed only in (part).

  Since the bubbles are formed only in the lower part, the deflection width L1 shown in FIG. 2B can be increased. This is because, when air bubbles are formed in the entire protective layer 13, the protective layer 13 is soft, so that the upper protective layer 13 to which the pressure Po from the outside is applied is selectively distorted, and the feeling of flexibility in contact with the upper protective layer 13 A force is selectively applied to a specific portion of the pressure body 11, but when the upper protective layer 13 is relatively hard without bubbles, the wider protective layer 13 is distorted, and a corresponding wide area is possible. This is because a force is applied to the flexible pressure-sensitive body 11 and the flexible pressure-sensitive body 11 bends with a wide width.

  FIG. 6 illustrates the configuration of another flexible pressure-sensitive body of the present embodiment, and represents a cross-sectional view of the cable-shaped pressure detection element 14. Specifically, FIG. 6A shows a cross section in the longitudinal direction, and FIG. 6B shows a cross section at the position of line EE in FIG. 6A. As in FIG. 4, bubbles are formed in the protective layer 13 as a portion formed only of air, but the difference is that the electrode is different from the internal electrode 15 positioned at the center of the flexible pressure-sensitive body 11 and the flexible layer. This is a point having a cable-like structure formed as an external electrode 16 provided around the pressure sensitive body 11.

  Since it can be manufactured in a continuous extrusion process by having a cable-like configuration, an effect of facilitating manufacture can be obtained. Further, since the cable has a centrally symmetric structure, the remanent polarization is formed radially from the center. For this reason, isotropic detection is possible with respect to pressure application from any direction. Therefore, even when the pressure response means rotates or twists during installation, the response voltage hardly changes. As a result, the degree of freedom of arrangement is increased, and the effect of enabling the determination of the presence or absence of stable pressure application and the stable location coordinate determination can be obtained.

  FIG. 7 illustrates another flexible pressure-sensitive body of the present embodiment, and represents a cross-sectional view of a cable-like pressure detection element 14. Specifically, FIG. 7A shows a cross section in the longitudinal direction, and FIG. 7B shows a cross section at the position of line FF in FIG. 7A. Similar to FIG. 6, it has a cable-like structure. A lower portion (a portion on the side opposite to the side to which the external pressure Po is applied) in the protective layer 13 is formed with a flexibility increasing layer 18.

The flexibility increasing layer 18 is formed of a material having a lower elastic modulus among thermoplastic elastomers and cross-linked rubbers like the protective layer 13, and is subjected to bending when an external pressure Po is applied. It has the effect of flexing the sexual pressure sensitive body 11 downward. In many cases, in order to increase flexibility, a structure or foam having a cavity is more preferably used. When the protective layer 13 is a foam, a lower density foam is suitably used as the flexibility increasing layer 17.

  It is preferable to form the flexibility increasing layer 17 in the final step after forming the certain protective layer 13, because the degree of deformation in the bending mode can be adjusted according to the purpose of use, and the degree of design freedom is increased.

  The pressure detecting element of the present embodiment has been described by taking the form having a layered structure and the form having a cable-like structure as an example, but what is effective in one form is also effective in the other form, particularly illustrated. It is not limited to the form.

  However, many of them including the following embodiments are described with respect to a cable-shaped pressure detection element. This is because the following effects can be obtained as already described.

  If it is a cable shape, since a pressure detection element can be manufactured in a continuous extrusion process, the effect that manufacture becomes easier is acquired. Further, since it is in the form of a coaxial cable, an outer electrode is formed around the core electrode and the flexible pressure sensitive body to have a centrally symmetric structure, and the residual polarization is formed radially from the center. For this reason, isotropic detection is possible with respect to pressure application from any direction. Therefore, even when the pressure response means rotates or twists during installation, the response voltage hardly changes. As a result, there is an effect that the degree of freedom of arrangement is increased and stable pressure detection is possible.

  Hereinafter, materials used in the flexible pressure-sensitive body of the present embodiment will be described.

  The flexible pressure sensitive body 11 is configured by dispersing piezoelectric ceramic powder in synthetic rubber or synthetic resin. As the synthetic rubber and synthetic resin, thermoplastic elastomers such as vinyl chloride and chlorinated polyethylene, and vulcanized rubbers such as EPDM are used. Piezoelectric ceramics include compounds having a perovskite structure such as lead titanate, lead zirconate, lead zirconate titanate, barium titanate, bismuth / sodium titanate, bismuth / sodium titanate-barium titanate, and alkali niobate. Ceramic materials that exhibit piezoelectricity such as a compound having a bismuth layer structure and a compound having a tungsten bronze structure are used.

  The protective layer 13 is made of synthetic rubber or synthetic resin used for the flexible pressure-sensitive body 11, and at least one of a thermoplastic elastomer and a vulcanized rubber is used. Moreover, what made these materials foam is used in order to enlarge the bending depth.

  As described above, the flexibility-enhancing layer 17 is made of the same material as the protective layer 13 and the flexible pressure-sensitive body 11 and has a low elastic modulus. Those are preferably used.

  As the electrode 12 and the external electrode 16, a wire material such as C, Pt, Au, Pd, Ag, Cu, Al, Ni, and stainless steel or a material obtained by rolling a wire material into a flat tape shape or the like is used. Alternatively, if the tape-like polymer film laminated with the metal wire or the tape-like wire is used, a more flexible external electrode can be obtained. Moreover, the electrode which covered the flexible pressure-sensitive body 11 by knitting a metal fine wire independently can also be used. Or what formed the said metal as a thin film by vapor deposition, sputtering, etc. is used.

  As the internal electrode 15, one or a plurality of fine metal wires used in the external electrode 16, a plurality of polyester fibers or the like wound with the metal wire, or the like is used.

  In addition, regarding the flexible pressure-sensitive body 11, the protective layer 13, the electrode 12, the internal electrode 15, and the external electrode 16, the same can be applied to the following embodiments.

  Next, a general example will be described particularly with respect to the manufacturing method of the cable-like pressure response means.

  First, a piezoelectric ceramic powder and a thermoplastic elastomer as a synthetic rubber or a synthetic resin are kneaded to form a composite. Next, by extruding this composite together with the internal electrode 15 using an extruder, a cable having the flexible pressure-sensitive body 11 made of the above composite formed around the internal electrode 15 is obtained. . Further, a polarization electrode covering the periphery of the cable is prepared, and by applying a voltage between this electrode and the internal electrode 15 in the cable, an electric field is formed radially from the internal electrode, and a ceramic piezoelectric body in a corresponding direction Form polarization inside. Further, after removing the electrode for polarization, the external electrode 12 is formed by winding a tape-shaped metal wire, a tape-shaped metal, or a tape laminated with a tape-shaped metal and a tape-shaped polymer around the cable. To do. Next, the pressure detecting element 14 is obtained by extruding a thermoplastic resin, a thermoplastic elastomer, rubber, etc. by an extruder with the cable having the external electrode 16 formed at the center to form a protective layer 13 for the cable. It is done. Polarization can also be performed by applying a voltage between the external electrode 16 and the internal electrode 15 after the external electrode 16 is formed.

  In addition, the piezoelectric ceramic in the flexible pressure-sensitive body of the pressure detection element of the present invention is preferably one that does not contain lead in consideration of disposal processing. For example, barium titanate, bismuth / sodium titanate, bismuth / sodium titanate-barium titanate, alkali niobate, etc. are preferably used. Furthermore, when used outdoors, such as for security purposes, or in environments using water such as toilets, baths, and kitchens, it is more preferable that the piezoelectric ceramic powder is subjected to a water repellent treatment to prevent moisture from entering. This is because the piezoelectric ceramic containing the above alkali metal easily absorbs moisture, and the performance easily fluctuates accordingly.

  Note that the materials and methods described in this embodiment can also be suitably applied to the following embodiments.

(Embodiment 2)
Next, a second embodiment will be described.

  In the present embodiment, the same configuration as that of the first embodiment has the same operational effects, and the same reference numerals are given and description thereof is omitted. Therefore, only different parts will be described.

  As already described, by suppressing the deformation in the compression mode and promoting the deformation in the bending mode, it is possible to suppress a decrease in the response voltage due to the curing of the flexible pressure-sensitive body 11 at a low temperature. It is.

  In the first embodiment, the configuration that mainly promotes the deformation in the bending mode (the configuration in which the bending depth corresponding to (c) in FIG. 2 increases) has been described. However, in the present embodiment, the deformation in the compression mode is mainly performed. The structure mainly composed of the deformation in the bending mode by suppressing is described with reference to FIGS.

As a specific configuration for suppressing the deformation in the compression mode, the elastic modulus of the protective layer is in the vertical direction (the direction in which the external force Po is applied) in the horizontal direction (the direction in which the external force Po is applied). There is a configuration that becomes larger than the vertical direction. By increasing the elastic modulus of the protective layer in the vertical direction, deformation of the compression mode corresponding to the vertical direction is suppressed. The vertical and horizontal directions used in the following description are defined by defining the direction parallel to the direction in which the external force Po is applied as the vertical direction and the orthogonal direction as the horizontal direction.

  In the present embodiment, this configuration will be described. The elastic modulus defined here will be described below.

  First, an example of a configuration having the above elastic modulus will be described with reference to FIG.

FIG. 8 is a cross-sectional view of the cable-shaped pressure detecting element 14, and FIG.

FIG. 8B shows a cross section taken along the line GG in FIG. A feature of this configuration is that the horizontal protective layer 13 is thicker than the vertical direction. Thereby, the elastic modulus of the protective layer 13 in the vertical direction becomes larger than the elastic modulus in the horizontal direction, and the compression in the vertical direction is suppressed. At this time, since the elastic modulus in the horizontal direction is small, the deformation in the bending mode corresponding to the deformation in the cable longitudinal direction in the horizontal direction is not suppressed. In this way, a configuration in which the deformation in the compression mode is suppressed and the deformation in the bending mode is mainly realized.

  The elastic modulus of the protective layer used here will be described with reference to FIG.

  FIG. 9 shows the measurement of the elastic modulus from the outside, except that the pressure detection element 14 corresponding to FIG. 8B is the protective layer 13 except for the internal electrode 15, the external electrode 16 and the flexible pressure sensitive body 11. This shows the distortion when the force FS is applied. 9A shows vertical distortion, and FIG. 9B shows horizontal distortion.

  Specifically, with respect to the vertical direction, as shown in FIG. 9A, when the vertical strain is xv with respect to the external force FS, the vertical elastic modulus is defined as F / xv. The Similarly, the elastic modulus in the horizontal direction is defined as F / xh where xh is the strain in the vertical direction.

  In order to change the elastic modulus of the protective layer defined in FIG. 9, in addition to changing the thickness of the protective layer, the elastic modulus of the constituent material of the protective layer may be changed. This case will be described with reference to FIG.

  10A and 10B are cross-sectional views of the cable-shaped pressure detection element 14, FIG. 10A shows a cross section in the longitudinal direction, and FIG. 10B shows a cross section at the position of line HH in FIG. Yes. The difference from FIG. 8 is that the protective layer 13 is composed of two parts, a protective layer 13a and a protective layer 13b, and the elastic modulus of the protective layer 13b is larger than that of the protective layer 13a.

  Since the elastic modulus as a material of the protective layer 13b is larger than that of the protective layer 13a, even in the elastic modulus defined in FIG. 9, the vertical elastic modulus is larger than the horizontal elastic modulus. Thus, a configuration in which the deformation in the compression mode is suppressed and the deformation in the bending mode is enhanced is realized.

  This elastic modulus is an elastic modulus as a material, and what has been described in FIG. 9 is an elastic modulus as a protective layer including a shape.

  In order to change the elastic modulus of the protective layer defined in FIG. 9, in addition to changing the thickness, a layer that suppresses deformation in the compression mode can be provided in a part of the protective layer. This case will be described with reference to FIG.

11A and 11B are cross-sectional views of the cable-shaped pressure detection element 14, FIG. 11A shows a cross section in the longitudinal direction, and FIG. Yes. The difference from FIG. 8 is that a compression suppression layer 18 is provided on the side surface of the protective layer 13.

  In addition, the material which comprises the compression suppression layer 18 of this Embodiment has a higher elastic modulus as a material than what is used for the flexible pressure sensitive body 11. FIG. Specifically, among thermoplastic elastomers and cross-linked rubbers, those having a higher elastic modulus as the material than those used for the flexible pressure-sensitive body 11 are preferably used, and also bend in the vertical direction. A general resin or metal can be used as long as it has elasticity.

  By using such a material, the elastic modulus defined in FIG. 9 including the protective layer 13 and the compression suppressing layer 18 can be adjusted higher in the vertical direction than in the horizontal direction. .

  As a result, a configuration in which the deformation in the compression mode is suppressed and the deformation in the bending mode is enhanced is realized.

  Further, according to this configuration, after forming the certain protective layer 13, by forming the compression suppression layer 18 in the final step, the degree of deformation in the bending mode can be adjusted according to the purpose of use, The effect that the freedom degree of design becomes high is acquired.

  Further, by increasing the elastic modulus as the material of the compression protective layer 18, it is possible to adjust the thickness of the pressure detecting element, and the degree of freedom of the element size is increased, and the arrangement can be easily performed. can get.

(Embodiment 3)
In the present embodiment, the same configuration as in the first embodiment has the same operational effects, and the same reference numerals are given and the description thereof is omitted. Therefore, only different parts will be described.

  As described above, the present invention includes (1) a configuration that promotes deformation in the bending mode, and (2) a configuration that suppresses deformation in the compression mode, and suppresses deformation in the compression mode to promote the bending mode. By doing so, it is the gist of the present invention to suppress a decrease in the response voltage due to the curing of the flexible pressure-sensitive body 11 at a low temperature and enable highly accurate pressure detection even when the environmental temperature changes.

  The first embodiment has already described mainly (1) a configuration that promotes deformation in the bending mode (a configuration in which the bending depth corresponding to (c) in FIG. 2 increases). In the second embodiment, mainly (2 ) The configuration for suppressing the deformation of the compression mode has been described.

  In the present embodiment, (1) among the configurations for promoting the deformation in the bending mode, a configuration using a bending width expanding material and a bending width expanding layer in order to increase the bending width corresponding to (b) of FIG. Will be described with reference to FIGS.

  First, one configuration of this embodiment will be described with reference to FIG. 12A and 12B are cross-sectional views of the cable-shaped pressure detecting element 14, in which FIG. 12A shows a cross section in the longitudinal direction, and FIG. 12B shows a cross section at the position of line JJ in FIG. ing. Although it has a cable-like structure as in FIG. 6, bubbles as shown in FIG. 6 are not formed in the protective layer 13. Furthermore, the most important difference is that a bending width expanding material 19 is formed in the protective layer 13.

  Since the bending width expanding material 19 fixed in the protective layer 13 is formed, the entire protective layer 13 is pulled by the bending width expanding material 19 when an external pressure Po is applied. As shown in FIG. 2B, the effect of increasing the bending width is obtained.

  Thus, by promoting deformation in the bending mode, even when the flexible pressure sensitive body 11 is cured at a low temperature, a decrease in response voltage is suppressed, and a highly accurate pressure detection is possible even when the environmental temperature changes. The effect becomes.

  Next, a different configuration of the present embodiment will be described with reference to FIG. FIG. 13 shows the structure of the bending width expanding material 19 formed in the protective layer 13.

  As already described, the bending width expanding member 19 is to be firmly fixed without slipping in the protective layer 13 because it pulls the protective layer 13 to bend a wide range of the protective layer 13. is important.

  Therefore, as shown in FIG. 13, it is preferable that the bending width expanding material 19 has a structure with large unevenness. Specifically, those having many convex portions as shown in FIG. 13A and those having many concave portions as shown in FIG. 13B are preferable. Further, a linear projection is formed by winding a linear object around the main shaft as shown in FIG. 13C, and a twisted line structure is formed by winding a plurality of lines as shown in FIG. 13D. A structure in which a large number of striped convex portions are formed on the surface is preferable.

  The material is not particularly limited as long as it has a property of bending as a wire, and can be formed of metal, resin, carbon, or the like.

  In particular, if a large number of flexure width expanding members 19 made of metal are formed in the protective layer 13, an effect of enhancing the shielding property and being strong against noise due to an external electric field can be obtained. Further, even if a planar bending width expanding material knitted with fine metal wires is formed in the protective layer, an excellent bending width increasing effect and shielding effect can be obtained.

  Further, a different configuration of the present embodiment will be described with reference to FIG. 14A and 14B are cross-sectional views of the cable-shaped pressure detecting element 14, in which FIG. 14A shows a cross-section in the longitudinal direction, and FIG. 14B shows a cross-section at the position KK in FIG. ing. Although it has a cable-like structure as in FIG. 12, the difference from FIG. 12 is that there is no bending width expanding material 19, instead, the upper part (the part on the side where external pressure Po is applied). This is the point that a bending width expanding layer 20 is formed on the protective layer 13.

  By forming the bending width expanding layer 20, when the external pressure Po is applied, the entire protective layer 13 is pulled by the bending width expanding layer 20 and tries to bend. As shown in (b), the effect of increasing the deflection width is obtained.

  Thus, by promoting deformation in the bending mode, even when the flexible pressure sensitive body 11 is cured at a low temperature, a decrease in response voltage is suppressed, and a highly accurate pressure detection is possible even when the environmental temperature changes. The effect becomes.

  It is preferable that the bending width expanding layer 20 is fixed to the protective layer 13 without slipping, like the bending width expanding material 19. Fixing can also be performed by bonding with an adhesive. At this time, the interface on the adhesion side of the protective layer 13 and the flexural width expanding layer 20 has an irregularity like the surface of the flexural width expanding material 19 in FIG. Moreover, fixation can also be performed by fusion | melting, when both the protective layer 13 and the bending width expansion layer 20 are formed with the thermoplastic resin.

  Moreover, as a material used for the bending width expansion layer 20, the material which is hard to expand and contract than the protective layer 13 and has a high elastic modulus in the cable longitudinal direction is used. A resin plate, a metal plate, or the like that is thin and bends well but hardly stretches or contracts is particularly preferably used.

(Embodiment 4)
In the present embodiment, the same configuration as in the first embodiment has the same operational effects, and the same reference numerals are given and the description thereof is omitted. Therefore, only different parts will be described.

  As described above, the present invention includes (1) a configuration that promotes deformation in the bending mode, and (2) a configuration that suppresses deformation in the compression mode, and suppresses deformation in the compression mode to promote the bending mode. By doing so, it is the gist of the present invention to suppress a decrease in the response voltage due to the curing of the flexible pressure-sensitive body 11 at a low temperature and enable highly accurate pressure detection even when the environmental temperature changes.

  In this embodiment, the elastic modulus of the protective layer has a maximum portion in the longitudinal direction in the configuration that suppresses the deformation in the compression mode (2) described in the second embodiment, and regarding this configuration, FIGS. Will be described.

  First, one configuration of the present embodiment will be described with reference to FIG. 15A and 15B are cross-sectional views of the cable-shaped pressure detecting element 14, in which FIG. 15A shows a cross-section in the longitudinal direction, and FIG. 15B shows a cross-section at the LL line position in FIG. ing. The most important feature is that the compression suppressing layer 18 is formed on a part of the protective layer in the longitudinal direction.

  By forming the compression suppressing layer 18 in a part of the protective layer, the elastic modulus in the vertical direction and the horizontal direction defined in FIG. 9 is increased. This increase in elastic modulus is caused by the formation of the compression suppressing layer 18. Limited to the longitudinal region. As a result, deformation of the portion where the compression suppression layer 18 is formed is selectively suppressed.

  Next, the usage method and operation of such a pressure detection element will be described with reference to FIG. FIG. 16 shows a state where the cable-shaped pressure detecting element 14 shown in FIG. 15 is fixed on an elastic body.

  A feature of the method of use is that the pressure Po from the outside is applied on the compression suppression layer 18. As already described, since the elastic modulus of the portion where the compression suppressing layer 18 is formed is increased, the deformation of this portion is suppressed. Furthermore, since most of the compression mode occurs at the portion where the external pressure Po is applied, the compression mode is effectively suppressed by forming the compression suppression layer 18, and the bending mode becomes the main deformation mode. Specifically, as shown in FIG. 16, the thickness d of the flexible pressure-sensitive body 15 + the internal electrode 15 corresponding to the portion where the protective layer 18 is formed is determined by applying an external pressure Po to be detected. Almost no change occurs, and the portion where the protective layer 18 is not formed is greatly bent downward.

  As described above, the deformation in the compression mode is suppressed, and the deformation in the bending mode is promoted. Therefore, even when the flexible pressure sensitive body 11 is cured at a low temperature, a decrease in the response voltage is suppressed, and the environmental temperature changes. However, the effect of enabling highly accurate pressure detection is obtained.

  In addition, when the pressure Po applied from the outside is large, the compression suppression layer 18 has an effect of suppressing the plastic deformation and damage of the pressure detecting element in order to suppress the internal deformation.

  In addition, as the material of the compression suppressing layer 18 used here, the same material as described in the second embodiment is used. Specifically, after forming up to the protective layer 13, it is simple and preferable to form the compression suppressing layer 18 by covering the protective layer with a metal tube, a resin heat-shrinkable tube, or the like.

In FIG. 15, the compression suppression layer 18 is formed on the entire circumference of the protective layer 13, but may be formed only on the side surface as shown in FIG. 11. In this case, it is preferable because the deformation in the bending mode at the compression suppression layer 18 is advanced.

  The elastic body used in FIG. 16 can be used as long as it has an elastic modulus smaller than that of the protective layer 13, but a resin foam or the like is preferably used because it has a low elastic modulus and promotes deformation in the bending mode. It is done.

  15 and 16, the cable-shaped pressure detection element has been described as an example, but the same effect can be obtained with a sheet-shaped pressure detection element.

  In FIGS. 15 and 16, the compression suppression layer 18 is formed at one place, but may be formed at several places in the longitudinal direction. In that case, it is preferable that a certain amount of distance is secured in the longitudinal direction between the compression suppression layers so that deformation in the bending mode is likely to occur.

  As described above, since the pressure detection element of the present invention can detect pressure with high accuracy even when the environmental temperature to be used changes, it is particularly suitable for applications that are used outdoors or in environments close to the outdoors. It is done. For example, it is particularly suitable for security purposes, such as installation outside a house such as a balcony or fence to detect intruders. In addition, it is used to detect the trapping of people and objects in the doors of automobiles and buildings, and to detect contact with the door handles, which are installed on the door handles of automobiles and unlocked by simply touching the door handles. Suitable for etc.

(A) Cross-sectional view when the pressure detection element is placed in a rigid shape and pressure is applied from above with an indenter (b) Cross-sectional view when the element is placed on a sponge and pressure is applied from above with an indenter (c) Qualitative representation of the temperature characteristics of the response voltage corresponding to (a) and (b) of the pressure detection element (A) Cross-sectional view showing the deformation of the flexible pressure-sensitive body of the pressure detection element and the bending mode of the electrode (b) Cross-sectional view showing the promotion of the deformation of the bending mode in which the bending width of the flexible pressure-sensitive body widens (C) Sectional view showing the deformation promotion in the bending mode in which the bending depth of the flexible pressure-sensitive body becomes deep. (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the first embodiment of the present invention (b) Cross-sectional view taken along the line BB of the pressure detection element (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the first embodiment of the present invention (b) Cross-sectional view taken along the line CC of the pressure detection element (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to Embodiment 1 of the present invention (b) Cross-sectional view of the pressure detection element at the DD line position (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to Embodiment 1 of the present invention (b) Cross-sectional view of the pressure detection element at the EE line position (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to Embodiment 1 of the present invention (b) Cross-sectional view of the pressure detection element at the FF line position (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the second embodiment of the present invention (b) Cross-sectional view taken along the line GG of the pressure detection element (A) The figure explaining the elastic modulus of the perpendicular direction of the protective layer of the pressure detection element of Embodiment 2 of this invention (b) The figure explaining the elastic modulus of the horizontal direction of the pressure detection element (A) Longitudinal sectional view of the pressure detecting element according to Embodiment 2 of the present invention (b) Cross sectional view taken along the line HH of the same pressure detecting element (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the second embodiment of the present invention (b) Cross-sectional view taken along line II of the pressure detection element (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the third embodiment of the present invention (b) Cross-sectional view taken along the line JJ of the pressure detection element (A) About the bending width expansion material of Embodiment 3 of this invention, the schematic diagram (b) same as the schematic diagram showing the structure which has many convex parts, The schematic diagram (c) same as the structure which has many concave parts, Schematic diagram showing the structure in which linear convex portions are formed (d) Schematic diagram showing the structure in which a large number of striped convex portions are formed (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to Embodiment 3 of the present invention (b) Cross-sectional view of the pressure detection element taken along the line KK (A) Cross-sectional view in the longitudinal direction of the pressure detection element according to the fourth embodiment of the present invention (b) Cross-sectional view of the pressure detection element at the LL line position Sectional drawing which showed the usage method of the pressure detection element of Embodiment 4 of this invention Sectional view of a conventional layered pressure sensor (A) Longitudinal sectional view of a conventional cable-shaped pressure sensing element (b) Cross sectional view of the pressure sensing element taken along the line AA

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Flexible pressure sensitive body 12 Electrode 13 Protective layer 14 Pressure detection element 15 Internal electrode 16 External electrode 17 Flexibility increase layer 18 Compression suppression layer 19 Deflection width expansion material 20 Deflection width expansion layer

Claims (14)

A flexible pressure-sensitive body having remanent polarization; a plurality of electrodes configured to sandwich the flexible pressure-sensitive body; and a protective layer that protects the flexible pressure-sensitive body and the electrode. A pressure detecting element having a portion formed only of air inside. The pressure detection element according to claim 1, wherein the portion formed only from air is a bubble. The pressure detection element according to claim 1, wherein a portion formed only of air is larger in the lower portion than in the upper portion of the flexible pressure sensitive body. The pressure detection element according to any one of claims 1 to 3, further comprising a flexibility increasing layer under the protective layer. A protective layer comprising: a flexible pressure-sensitive body having remanent polarization; a plurality of electrodes configured to sandwich the flexible pressure-sensitive body; and a protective layer for protecting the flexible pressure-sensitive body and the electrode. A pressure detecting element in which the elastic modulus in the vertical direction is larger than the elastic modulus in the horizontal direction. The pressure detection element according to claim 5, wherein the thickness of the side portion of the protective layer is thicker than the thickness of the upper and lower portions. The pressure detection element according to claim 5 or 6, wherein an elastic modulus of a material forming the side portion of the protective layer is larger than an elastic modulus of a material forming the upper part and the lower part. The pressure detection element according to claim 5, further comprising a compression suppression layer on a side portion of the protective layer. The pressure detection element according to any one of claims 1 to 8, wherein the protective layer includes a bending width expanding material. The pressure detection element according to any one of claims 1 to 9, further comprising a bending width expansion layer on an upper portion or a lower portion of the protective layer. The pressure detection element according to claim 10, wherein a bending width expanding layer is included only in the upper part of the protective layer. The pressure detection element according to claim 1, wherein the pressure detection element has a maximum elastic modulus portion in a longitudinal direction of the protective layer. The pressure detection element according to claim 12, wherein the maximum portion of the elastic modulus is formed by forming a compression suppression layer on a part of the protective layer in the longitudinal direction. The method for using a pressure detection element according to claim 12 or 13, wherein an external pressure to be detected is applied to the maximum portion of the elastic modulus in the longitudinal direction of the protective layer.