JP2008151638A - Cable pressure sensor - Google Patents

Abstract

An object of the present invention is to prevent environmental pollution caused by piezoelectric particles containing lead used in a conventional pressure sensor, and to prevent a decrease in sensor sensitivity due to electrode instability.
A formula that does not include an organic polymer 10 and lead around the core electrode 7 is _{(Bi 0.5} Na _0.5) composite oxide and the chemical formula represented by TiO 3 · BaTiO ₃ is CaTiO _3, BaZrO ₃ , a flexible pressure-sensitive body 8 composed of ceramic piezoelectric particles 11 made of a solid solution with at least one of the complex oxides represented by ₃ , and an organic polymer 12 and a conductive material around the flexible pressure-sensitive body 8. By providing the flexible outer electrode 9 composed of the conductive particles 13, environmental pollution can be prevented, and an electrode having stable electric resistance and flexibility can be obtained. Sensor sensitivity can be realized stably.
[Selection] Figure 1

Description

  The present invention relates to a structure of a flexible cable-shaped pressure sensor using a ceramic piezoelectric particle containing no organic polymer and lead as a pressure sensitive body.

Conventionally, this type of cable-type pressure sensor is as shown in FIG. 7 (see, for example, Patent Document 1). As shown in FIG. 7, a flexible pressure-sensitive body 4 is disposed around a core electrode 3 composed of a linear conductive material 1 and a conductive rubber 2, and a skin electrode layer 5 and a heat-shrinkable tube 6 are disposed around the flexible pressure-sensitive body 4. It is constructed by coating sequentially. As the flexible pressure-sensitive body 4, a composite in which ceramic piezoelectric powder of lead titanate and lead zirconate titanate is added to synthetic rubber or synthetic resin is used, and the outer skin electrode layer 5 is composed of the flexible pressure-sensitive body 4. The surface is coated with a conductive paint such as silver rubber paint. When pressure is applied to a part or the entire surface of the cable-shaped pressure sensor, the pressure sensor in that part is distorted. As a result, a voltage is induced between the core electrode 3 and the skin electrode layer 5, and this induced voltage is used. The pressure is detected.
JP 62-230071 A

  However, the conventional cable-shaped pressure sensor includes a piezoelectric material made of an oxide containing lead in the flexible pressure-sensitive body 4. This cable-type pressure sensor is assumed to be removed from the product when it is disposed of, and then cut and discarded. The discarded cable-type pressure sensor is exposed to the environment such as acid rain. In such a case, there is a concern that lead is eluted from the piezoelectric material made of oxide containing lead constituting the flexible pressure-sensitive body 4 and causes environmental pollution.

  In addition, since the outer electrode layer 5 is formed by applying a conductive paint such as a silver-based rubber paint, there is a possibility that there is a part where the electric resistance increases due to the non-uniform film thickness. It had the subject that a characteristic worsened.

  Further, since the heat shrinkable tube 6 coated around the outer electrode layer 5 is cured by heat shrinkage, when pressure is applied to the heat shrinkable tube 6, the amount of distortion in the portion is reduced, so that the core electrode 3 and There was a problem that the voltage induced between the skin electrode layers 5 was reduced, and the sensitivity as a sensor was lowered.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a cable-like pressure sensor that is free from environmental pollution and has high sensitivity.

In order to solve the above-described conventional problems, the cable-shaped pressure sensor of the present invention is formed of a flexible pressure-sensitive body that is provided around a core electrode and a flexible outer electrode that is provided on the surface of the flexible pressure-sensitive body. The pressure-sensitive body is composed of at least an organic polymer, a composite oxide represented by the chemical formula (Bi _0.5 Na _0.5 ) TiO ₃ .BaTiO ₃ , and a composite oxide represented by the chemical formulas CaTiO ₃ and BaZrO ₃ . It is composed of ceramic piezoelectric particles made of at least one solid solution, and the flexible outer electrode is made of organic polymer and conductive particles.

As a result, the ceramic piezoelectric particles constituting the flexible pressure-sensitive body do not contain lead, so that elution of lead can be prevented even when exposed to an environment such as acid rain, and the above-described ceramic piezoelectric containing no lead. The body particles have a remarkably lower relative dielectric constant than the piezoelectric particles containing lead, and in particular, the composite oxide whose chemical formula is represented by (Bi _0.5 Na _0.5 ) TiO ₃ .BaTiO ₃ and the chemical formula is CaTiO. _3. Piezoelectric particles made of a solid solution with at least one of complex oxides represented by BaZrO ₃ have a low coercive electric field, so that the polarization treatment voltage for expressing piezoelectric characteristics can be lowered. Further, by configuring the flexible outer electrode with an organic polymer and conductive particles, it is possible to prevent a low electrical resistance as the outer electrode and a decrease in flexibility of the entire cable-shaped pressure sensor. Furthermore, since the same organic polymer is used for the flexible pressure-sensitive body 8 and the flexible outer electrode 9, the adhesion can be improved and the durability can be improved.

In the cable-shaped pressure sensor of the present invention, since the ceramic piezoelectric particles constituting the flexible pressure-sensitive body do not contain lead, even if the cable-shaped pressure sensor is disposed of and exposed to an environment such as acid rain, lead elution is not caused. In addition, environmental pollution can be prevented. Further, the ceramic piezoelectric particles applied to the present invention have a lower dielectric constant than the conventional lead-containing piezoelectric particles, and the chemical formula is represented by (Bi _0.5 Na _0.5 ) TiO ₃ · BaTiO ₃ . The piezoelectric particles made of a solid solution of the composite oxide and at least one of the composite oxides represented by the chemical formulas of CaTiO ₃ and BaZrO ₃ have a low coercive electric field, so that the polarization treatment voltage for expressing the piezoelectric characteristics is lowered. Thus, the safety during the polarization process can be improved. Further, by using a composite of an organic polymer and conductive particles as the outer electrode, both low electrical resistance and flexibility can be achieved, so that sensitivity as a pressure sensor can be improved.

1st invention is formed from the core electrode as an inner side electrode, the flexible pressure-sensitive body surrounding the core electrode, and the flexible outer electrode circumferentially arranged on the surface of the flexible pressure-sensitive body, The flexible pressure-sensitive body is composed of at least an organic polymer, a composite oxide represented by a chemical formula of (Bi _0.5 Na _0.5 ) TiO ₃ .BaTiO ₃ , and a composite oxide represented by a chemical formula of CaTiO ₃ or BaZrO _3. Ceramic piezoelectric particles comprising a solid solution with at least one kind of material, and comprising a flexible outer electrode made of an organic polymer and conductive particles, whereby ceramic piezoelectric particles contained in the flexible pressure sensitive body Since lead does not contain lead, lead is not eluted even when exposed to an environment such as acid rain, and environmental pollution can be prevented. Further, the above-mentioned ceramic piezoelectric particles not containing lead have a lower dielectric constant than the piezoelectric particles containing lead, and the composite oxidation represented by the chemical formula (Bi _0.5 Na _0.5 ) TiO ₃ · BaTiO _3. Since the piezoelectric particles made of a solid solution with a compound and a compound oxide having a chemical formula represented by CaTiO ₃ or BaZrO ₃ have a low coercive electric field, the polarization treatment voltage for expressing the piezoelectric characteristics can be lowered, and the polarization can be reduced. Work safety can be improved. In addition, since the flexible outer electrode is composed of an organic polymer and conductive particles, an electrode having a stable low electric resistance and flexibility can be realized, and a pressure sensor with excellent sensitivity can be obtained. In addition, since the same organic polymer is used for the flexible pressure-sensitive body 8 and the flexible outer electrode 9, adhesion can be improved and durability can be improved.

  In the second invention, in particular, the organic polymer of the first invention is composed of at least one of a thermoplastic resin, a thermoplastic elastomer, and a vulcanized rubber, thereby lowering the mechanical impedance of the entire cable-shaped pressure sensor. Therefore, when pressure is applied to the pressure sensor, it can be easily deformed, and the induced voltage can be detected under a low applied pressure.

  In the third aspect of the invention, the sensor sensitivity can be enhanced because the content of the ceramic piezoelectric particles can be increased by configuring the thermoplastic elastomer of the second aspect of the invention with chlorinated polyethylene.

In the fourth invention, the conductive particles of the first to third inventions are at least C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, Ni—Cr. By comprising by 1 type, the outstanding electroconductivity can be expressed and the performance as an electrode can be improved.

  In the fifth aspect of the invention, in particular, the flexible outer electrode of any one of the first to fourth aspects of the invention is covered with a conductive braid so that the flexible outer electrode is grounded and can be used as a core electrode. An induced voltage generated between the flexible outer electrodes can be detected, and electrical noise from the external space can be blocked.

  In the sixth invention, in particular, the conductive braid of the fifth invention is at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr. By configuring, the mechanical strength of the conductive braid can be increased, so the durability as a pressure sensor can be improved.

  In the seventh aspect of the invention, in particular, the flexible outer electrode or the conductive braid of any one of the first to sixth aspects of the invention is covered with an insulating elastic body, so that the flexible pressure sensitive body and the flexible body are flexible. The adhesion of the outer electrode is improved, the generation of an air layer can be prevented, and the decrease in flexibility of the entire pressure sensor can be suppressed, so when pressure is applied to the pressure sensor, Can be suppressed, and sensor sensitivity can be prevented from decreasing.

  In the eighth invention, in particular, the insulating elastic body of the seventh invention is composed mainly of an organic polymer, so that the penetration of water vapor into the pressure sensor can be suppressed, and elasticity and flexibility are achieved. It is possible to achieve excellent moisture resistance while maintaining the above.

  According to the ninth aspect of the invention, in particular, the insulating elastic body of the seventh or eighth aspect is composed of at least one of a thermoplastic resin, a thermoplastic elastomer, and a vulcanized rubber, so that the elasticity and flexibility of the entire pressure sensor are achieved. As a result, the sensor sensitivity can be prevented from decreasing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a main part of a cable-shaped pressure sensor according to the first embodiment of the present invention.

  In FIG. 1, the cable-shaped pressure sensor has a flexible pressure-sensitive body 8 formed around a core electrode 7, and a flexible outer electrode 9 is formed on the surface of the flexible pressure-sensitive body 8. FIG. 2 is a partial cross-sectional view showing the internal structure of the flexible pressure-sensitive body 8. The flexible pressure-sensitive body 8 is an organic polymer 10 and a ceramic piezoelectric body that does not contain lead dispersed in the organic polymer 10. It consists of particles 11. FIG. 3 is a partial cross-sectional view showing the configuration of the flexible outer electrode 9. The flexible outer electrode 9 includes an organic polymer 12 and conductive particles 13 dispersed in the organic polymer 12. It is configured.

As the core electrode 7, a core electrode having the structure shown in the conventional example, a core electrode made of one or a plurality of fine metal wires, a core electrode in which a metal such as copper is wound around a converging line of many polyester fibers, and the like are used. As the organic polymer 10 constituting the flexible pressure-sensitive body 8, a thermoplastic resin, a thermoplastic elastomer, or a vulcanized rubber is used. As the ceramic piezoelectric particles 11 not containing lead, the composite oxide represented by the chemical formula (Bi _0.5 Na _0.5 ) TiO ₃ .BaTiO ₃ and the composite oxide represented by the chemical formulas CaTiO ₃ and BaZrO ₃ are used. Ceramic piezoelectric particles made of a solid solution with at least one kind of material are used. The organic polymer 12 constituting the flexible outer electrode 9 is made of the same material as the organic polymer 10 described above, and the conductive particles 13 are made of C, Pt, Au, Pd, Ag, Cu, Al, At least one of Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr is used.

  About the cable-shaped pressure sensor comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  After the cable-shaped pressure sensor has the above-described configuration, it is polarized by applying a high DC voltage between the core electrode 7 and the flexible outer electrode 9 to impart piezoelectricity. By applying piezoelectricity to the flexible pressure-sensitive body 8, when a time-varying pressure is applied to a part or the entire surface of the cable-shaped pressure sensor, the core electrode 7 and the flexible outer electrode 9 are not connected. An oscillating voltage is induced in accordance with the acceleration generated in the cable-shaped pressure sensor in that portion. The pressure can be detected using this induced voltage. This cable-like pressure sensor is attached to, for example, an automobile door or window, and is used as a pressure detection device.

When a product equipped with the cable-shaped pressure sensor of the present embodiment is used, it is considered that the cable-shaped pressure sensor is removed from the product, cut into pieces, and then discarded. The cable-shaped pressure sensor that has been disposed of may be exposed to a severe environment such as acid rain, and the component material of the cable-shaped pressure sensor may be eluted by acid rain. The ceramic piezoelectric particles 11 include a composite oxide whose chemical formula does not contain lead is represented by (Bi _0.5 Na _0.5 ) TiO ₃ · BaTiO ₃ , and a composite oxide whose chemical formula is represented by CaTiO ₃ and BaZrO ₃ . Since piezoelectric particles made of a solid solution with at least one of the above are used, there is no elution of lead and the environment is not polluted.

Further, at least a composite oxide represented by a chemical formula (Bi _0.5 Na _0.5 ) TiO ₃ · BaTiO ₃ and a composite oxide represented by a chemical formula CaTiO ₃ and BaZrO ₃ are used as the ceramic piezoelectric particles 11. Piezoelectric particles made of a solid solution with one type have a significantly lower relative dielectric constant and lower coercive electric field than conventional lead-containing piezoelectric particles, so that the polarization treatment voltage for expressing the piezoelectric characteristics can be lowered. Safety during work can be improved.

  In addition, by using at least one of a thermoplastic resin, a thermoplastic elastomer, and a rubber after vulcanization as the organic polymer 10, the mechanical impedance of the flexible pressure-sensitive body 8 itself can be lowered, so that pressure is applied to the pressure sensor. Therefore, the induced voltage can be easily deformed and the induced voltage can be detected under a low applied pressure. In particular, by configuring the thermoplastic elastomer with chlorinated polyethylene, the content of the ceramic piezoelectric particles 11 can be increased, so that the sensor sensitivity can be further increased.

  Further, by forming the flexible outer electrode 9 from the organic polymer 12 and the conductive particles 13, it is possible to realize an electrode having a constant and low electric resistance and excellent flexibility, so that the sensitivity is high. While being able to obtain a pressure sensor, the same organic polymers 10 and 12 are used for the flexible pressure-sensitive body 8 and the flexible outer electrode 9, so that adhesion can be improved and durability can be improved. Can do.

  Further, by using at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr as the conductive particles, excellent conductivity can be obtained. And the performance as an electrode can be further improved.

(Embodiment 2)
FIG. 4 is a cross-sectional view of a main part of the cable-shaped pressure sensor according to the second embodiment of the present invention. In FIG. 4, the difference from the first embodiment is that a conductive braid 14 is provided around the flexible outer electrode 9. The same members as those in the first embodiment are denoted by the same reference numerals.

As shown in FIG. 4, the flexible outer electrode 9 is formed on the surface of the flexible pressure-sensitive body 8 and then covered with a conductive braid 14 so as to be in contact with the flexible outer electrode 9. As a material of the conductive braid 14, at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr is used.

  In the absence of the conductive braid 14, it is easy to pick up external noise when detecting the induced voltage generated between the core electrode 7 and the flexible outer electrode 9. Accordingly, the outer periphery of the flexible outer electrode 9 is covered with the conductive braid 14 having a conductivity higher than that of the flexible outer electrode 9, and the flexible outer electrode 9 and the conductive braid 14 are short-circuited. By holding the braid 14 at the ground potential, a shield function can be added, so that electrical noise from the external space can be completely blocked.

  As the material of the conductive braid 14, it is particularly excellent when it is composed of at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr. The shield effect can be realized and the mechanical strength of the conductive braid 14 can be increased, so that the tensile strength of the pressure sensor can be increased and the durability can be improved.

(Embodiment 3)
FIG. 5 is a cross-sectional view of a main part of a cable-shaped pressure sensor according to the third embodiment of the present invention. In FIG. 5, the difference from the first embodiment is that the periphery of the flexible outer electrode 9 is covered with an insulating elastic body 15. The same members as those in the first embodiment are denoted by the same reference numerals.

  The insulating elastic body 15 is composed of an organic polymer as a main component composed of at least one of a thermoplastic resin, a thermoplastic elastomer, and a vulcanized rubber.

  By covering the periphery of the flexible outer electrode 9 with the insulating elastic body 15, the adhesion between the flexible pressure-sensitive body 8 and the flexible outer electrode 9 becomes strong, and an air layer is not generated. Sensitivity can be further improved. Further, since the insulating elastic body 15 has excellent flexibility, it is possible to suppress a decrease in flexibility of the entire pressure sensor. Therefore, when pressure is applied to the pressure sensor, it is possible to suppress a decrease in the amount of distortion at that portion, and thus it is possible to prevent a decrease in sensor sensitivity.

  Further, it is desirable that the organic polymer of the insulating elastic body 15 is composed of any one of a thermoplastic elastomer and a vulcanized rubber in order to exhibit the above-described effects. In particular, these materials can suppress the penetration of water vapor into the sensor, can achieve excellent moisture resistance, and can suppress the decrease in elasticity and flexibility of the entire pressure sensor. Therefore, it is possible to prevent a decrease in sensor sensitivity.

  The insulating elastic body 15 may be made of an organic polymer mixed with a filler such as an insulating metal oxide in order to improve heat resistance.

(Embodiment 4)
FIG. 6 is a cross-sectional view of a main part of a cable-shaped pressure sensor according to the fourth embodiment of the present invention. In FIG. 6, the difference from the second embodiment and the third embodiment is that both the conductive braid 14 and the insulating elastic body 15 are provided. The same members as those in the first embodiment are denoted by the same reference numerals.

  A conductive braid 14 is provided around the flexible outer electrode 9, and an insulating elastic body 15 is formed around the conductive braid 14. With this configuration, the effects of both the second embodiment and the third embodiment can be realized.

  As described above, the cable-shaped pressure sensor according to the present invention prevents environmental pollution because the ceramic piezoelectric particles do not contain lead, and the flexible outer electrode has stable electric resistance and flexibility. Since excellent sensor sensitivity can be realized stably, it can be applied to a wide range of uses such as a pressure detection device for preventing an automobile door or window from being caught and for detecting the presence of a nursing bed.

Sectional drawing of the principal part of the cable-shaped pressure sensor in Embodiment 1 of this invention 1 is a partial cross-sectional view showing a configuration of a flexible pressure-sensitive body according to Embodiment 1 of the present invention. 1 is a partial cross-sectional view showing a configuration of a flexible outer electrode according to Embodiment 1 of the present invention. Sectional drawing of the principal part of the cable-shaped pressure sensor in Embodiment 2 of this invention Sectional drawing of the principal part of the cable-shaped pressure sensor in Embodiment 3 of this invention Sectional drawing of the principal part of the cable-shaped pressure sensor in Embodiment 4 of this invention Cross section of the main part of a conventional cable-type pressure sensor

Explanation of symbols

7 Core Electrode 8 Flexible Pressure Sensitive Body 9 Flexible Outer Electrode 10 Organic Polymer 11 Ceramic Piezoelectric Particle 12 Organic Polymer 13 Conductive Particle 14 Conductive Braid 15 Insulating Elastic Body

Claims (9)

Formed by a core electrode as an inner electrode, a flexible pressure-sensitive body provided around the core electrode, and a flexible outer electrode provided around the surface of the flexible pressure-sensitive body. The pressure body is at least an organic polymer, a composite oxide represented by a chemical formula of (Bi _0.5 Na _0.5 ) TiO ₃ .BaTiO ₃ , and a composite oxide represented by a chemical formula of CaTiO ₃ and BaZrO _3. A cable-shaped pressure sensor composed of ceramic piezoelectric particles made of one kind of solid solution, wherein the flexible outer electrode is made of at least an organic polymer and conductive particles. The cable-shaped pressure sensor according to claim 1, wherein the organic polymer is made of at least one of a thermoplastic resin, a thermoplastic elastomer, and a vulcanized rubber. The cable-shaped pressure sensor according to claim 2, wherein the thermoplastic elastomer is chlorinated polyethylene. The conductive particles are made of at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr. Cable-shaped pressure sensor as described. The cable-shaped pressure sensor according to any one of claims 1 to 4, wherein the periphery of the flexible outer electrode is covered with a conductive braid. 6. The cable-shaped pressure according to claim 5, wherein the conductive knitting element is made of at least one of C, Pt, Au, Pd, Ag, Cu, Al, Ni, Fe—Cr, Fe—Ni—Cr, and Ni—Cr. Sensor. The cable-shaped pressure sensor according to any one of claims 1 to 6, wherein the flexible outer electrode or the conductive braid is covered with an insulating elastic body. The cable-shaped pressure sensor according to claim 7, wherein the insulating elastic body is mainly composed of an organic polymer. The cable-shaped pressure sensor according to claim 7 or 8, wherein the organic polymer comprises at least one of a thermoplastic resin, a thermoplastic elastomer, and a vulcanized rubber.

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