JP2024091012A - Pressure sensitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensitive sensor having low risk of short circuit generation and easy to suppress generation of malfunction.

SOLUTION: A pressure sensitive sensor comprises a cylindrical elastic insulator 11 having a hollow part 17 and extending in a longitudinal direction, a plurality of electrode wires 21, 21 arranged along an inner circumferential surface of the hollow part 17 of the elastic insulator 11 and arranged at an interval to each other. The elastic insulator 11 includes at least a first layer 12 containing an olefinic thermoplastic elastomer. At least either of a coat 23 of the elastic insulator 11 and coats of the electrode wires 21, 21 includes a second layer 13 which is a part adjacent to the first layer. The second layer 13 contains a styrene thermoplastic elastomer and an olefinic crystalline resin.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a pressure sensor.

A pressure sensor has been proposed that includes a hollow insulator formed into a hollow tube and multiple electrode wires held inside the hollow insulator (see, for example, Patent Documents 1 and 2). The pressure sensor functions as a switch when external pressure causes the electrode wires, which are held apart, to come into contact with each other.

In the pressure sensor disclosed in Patent Document 1, the electrode wire contains a conductive resin composition that includes a styrene-based thermoplastic elastomer and carbon. The hollow inner layer of the insulator contains a styrene-based thermoplastic elastomer, and the outer layer of the insulator contains a thermoplastic urethane.

In the pressure sensor disclosed in Patent Document 2, the outer insulator layer contains a thermoplastic urethane and an acid-modified polymer modified with an unsaturated carboxylic acid or the like to improve adhesion between the inner and outer insulator layers.

Patent No. 6380684 Patent No. 6972942

The insulator used in the pressure sensor described above is highly moisture permeable, so depending on the usage environment, water vapor may enter the inside of the pressure sensor. The water vapor that enters the inside condenses due to temperature changes, etc., and causes a short circuit between the electrode wires and between the electrodes of the terminals. If a short circuit occurs, there is a risk that the switching function of the pressure sensor will be impaired.

Patent Document 2 also discloses a pressure sensor having a hollow insulator formed using an olefin-based thermoplastic elastomer. The olefin-based thermoplastic elastomer is a material with lower moisture permeability than the above-mentioned styrene-based thermoplastic elastomer. This pressure sensor is less susceptible to water vapor penetration than the above-mentioned pressure sensor containing a styrene-based thermoplastic elastomer.

On the other hand, the outer layer adjacent to the hollow insulator formed using an olefin-based thermoplastic elastomer contains thermoplastic polyurethane and acid-modified polymer. The adhesion between this hollow insulator and the outer layer is not strong, and there is a possibility that they may peel off. If peeling occurs, there is a risk that malfunctions will occur in the pressure sensor.

The present invention has been made to solve the above problems, and aims to provide a pressure sensor that is easy to prevent short circuits and malfunctions.

In order to achieve the above object, the present invention provides the following means.
A pressure-sensitive sensor according to one embodiment of the present invention comprises a cylindrical elastic insulator having a hollow portion extending along the longitudinal direction, and a plurality of electrode wires arranged along the inner surface of the hollow portion in the elastic insulator and spaced apart from each other, wherein the elastic insulator has at least a first layer containing an olefin-based thermoplastic elastomer, and at least one of the elastic insulator and the coating of the electrode wire has a second layer adjacent to the first layer, and the second layer contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin.

According to the pressure sensor of the present invention, at least a first layer containing an olefin-based thermoplastic elastomer as a component is provided in the elastic insulator. Olefin-based thermoplastic elastomer has lower moisture permeability than styrene-based thermoplastic elastomer, and water vapor is less likely to penetrate into the inside than the first layer. Because water vapor is less likely to penetrate into the inside of the pressure sensor, condensation is less likely to occur inside the pressure sensor.

The second layer, which is adjacent to the first layer, contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin. The olefin-based crystalline resin has adhesive properties with the olefin-based thermoplastic elastomer of the first layer. Compared to when the second layer is formed only from a styrene-based thermoplastic elastomer, the adhesive properties between the first layer and the second layer are higher.

The pressure sensor of the present invention has an elastic insulator that is provided with at least a first layer that contains an olefin-based thermoplastic elastomer as a component, and a second layer that is adjacent to the first layer that contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin, which has the effect of suppressing the occurrence of short circuits and making it easier to suppress the occurrence of malfunctions.

1 is a perspective view illustrating a configuration of a pressure-sensitive sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating the configuration of the pressure-sensitive sensor of FIG. 1 . FIG. 11 is a cross-sectional view illustrating the configuration of another embodiment of the pressure-sensitive sensor. FIG. 13 is a cross-sectional view illustrating the configuration of still another embodiment of the pressure-sensitive sensor. 2 is a cross-sectional view illustrating a state in which an external pressure is applied to the pressure-sensitive sensor of FIG. 1 . FIG. 1 is a schematic diagram illustrating a moisture permeability test device for evaluating a pressure-sensitive sensor. 1 is a table illustrating evaluation results obtained using a moisture permeability test device.

A pressure sensor 10 according to one embodiment of the present invention will be described with reference to Figs. 1 to 7. The pressure sensor 10 of this embodiment is a sensor provided in an automatic door opening/closing device that electrically moves a door panel of a vehicle or the like. Specifically, it is a sensor that detects whether a foreign object or a human body is caught or comes into contact with the opening/closing portion between the periphery of the vehicle's entrance/exit and the door panel.

Fig. 1 is a perspective view illustrating the configuration of a pressure-sensitive sensor 10 according to the present embodiment. Fig. 2 is a cross-sectional view illustrating the configuration of the pressure-sensitive sensor 10.
1 and 2, the pressure-sensitive sensor 10 is provided with an elastic insulator 11 and a plurality of electrode wires 21. In this embodiment, the present invention will be described as being applied to an example in which two electrode wires 21, 21 are provided. Note that the number of electrode wires 21 is not limited to two, and may be any number as long as it is a plurality.

The elastic insulator 11 is a member that holds multiple electrode wires 21, 21 inside. The elastic insulator 11 is also a member formed in an elongated shape, and is formed in a cylindrical shape with a hollow portion 17, which will be described later.

The elastic insulator 11 has a hollow portion 17, which is a space that is continuously formed inside the elastic insulator 11 in the longitudinal direction. A plurality of electrode wires 21, 21 are arranged on the inner peripheral surface of the hollow portion 17.

When the pressure sensor 10 is not deformed by an external force, the hollow portion 17 preferably has a size and cross-sectional shape that allows the multiple electrode wires 21, 21 to be accommodated with a space between them. In other words, the hollow portion 17 preferably has a size and cross-sectional shape that allows the multiple electrode wires 21, 21 to be accommodated without contacting each other. The size and cross-sectional shape of the hollow portion 17 may be changed as appropriate depending on the number of electrode wires 21 provided in the pressure sensor 10.

In this embodiment, the elastic insulator 11 is provided with an outer layer (corresponding to a first layer) 12 and an inner layer (corresponding to a second layer) 13 .
The outer layer 12 forms an outer peripheral portion of the elastic insulator 11 and covers the periphery of the inner layer 13. The thickness of the outer layer 12 can be, for example, 0.3 mm. The outer layer 12 may be thicker than 0.3 mm.

The outer layer 12 of this embodiment is preferably formed using a composition containing an olefin-based thermoplastic elastomer. The outer layer 12 is preferably formed using a composition containing an olefin-based thermoplastic elastomer having an olefin-based resin in the continuous phase and a cross-linked rubber component in the dispersed phase. Furthermore, the outer layer 12 is more preferably formed using a composition containing an olefin-based thermoplastic elastomer having polypropylene in the continuous phase and cross-linked ethylene propylene diene rubber (EPDM) in the dispersed phase.

The composition constituting the outer layer 12 may contain other additives as necessary, such as processing aids, oils, flame retardants, flame retardant assistants, crosslinking assistants, UV absorbers, antioxidants, copper damage inhibitors, lubricants, fillers, compatibilizers, stabilizers, and colorants.

The olefin-based thermoplastic elastomer is a thermoplastic elastomer having a polyolefin resin as a hard segment.
The hard segment is made of a crystalline polyolefin, such as polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), etc.

Examples of soft segments of olefin-based thermoplastic elastomers include ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), acrylonitrile-butadiene copolymer (NBR), hydrogenated NBR, ethylene-octene copolymer (EOR), ethylene-butene-1 copolymer (EBR), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), and elastomers containing styrene components.

The inner layer 13 forms the central portion of the elastic insulator 11 and is adjacent to the outer layer 12. A hollow portion 17 is formed inside the inner layer 13. In this embodiment, the inner layer 13 is preferably formed using a composition containing a styrene-based thermoplastic elastomer and an olefin-based crystalline resin.

The composition constituting the inner layer 13 may contain other additives as necessary, such as processing aids, oils, flame retardants, flame retardant assistants, crosslinking assistants, UV absorbers, antioxidants, copper damage inhibitors, lubricants, fillers, compatibilizers, stabilizers, and colorants.

Styrenic thermoplastic elastomers are block or random copolymers that have polymer blocks of styrene monomers (e.g., polystyrene) as hard segments and polymer blocks of olefins as soft segments.

Specific examples of usable copolymers include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-isoprene-butadiene-styrene block copolymers (SIBS), and hydrogenated copolymers such as styrene-ethylene-butylene-styrene block copolymers (SEBS), styrene-ethylene-propylene-styrene block copolymers (SEPS), and styrene-ethylene-ethylene-propylene-styrene block copolymers (SEEPS). These may be used alone or in combination of two or more.

The fewer unsaturated bonds in the molecular chain of a styrene-based thermoplastic elastomer, the higher its heat resistance. From the viewpoint of improving the heat resistance of the elastic insulator 11, a styrene-based thermoplastic elastomer that does not contain double bonds in the molecular chain due to hydrogenation is preferred. Specifically, SEBS, SEPS, SEEPS, etc. are preferred.

Examples of olefin-based crystalline resins include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, polypropylene, ethylene-acrylate copolymer, ethylene-octene copolymer (EOR), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-butyl acrylate copolymer (EBA), ethylene-butene-1 copolymer (EBR), etc., which may be used alone or in combination of two or more.

The amount of olefin-based crystalline resin in the inner layer 13 is preferably 10 parts by mass or more and 70 parts by mass or less out of a total of 100 parts by mass of the styrene-based thermoplastic elastomer.

In this embodiment, the amount of olefin-based crystalline resin in the inner layer 13 is 20 parts by mass out of a total of 100 parts by mass with the styrene-based thermoplastic elastomer (80 parts by mass of styrene-based thermoplastic elastomer and 20 parts by mass of olefin-based crystalline resin, totaling 100 parts by mass).

The two electrode wires 21, 21 are arranged at a distance from each other on the inner circumferential surface of the hollow portion 17. For example, they are arranged at positions facing each other with the center of the pressure sensor 10 in between. The two electrode wires 21, 21 are also arranged to extend in a spiral shape in the longitudinal direction along the inner circumferential surface of the hollow portion 17. The two electrode wires 21, 21 may also be arranged to extend in a straight line in the longitudinal direction along the inner circumferential surface of the hollow portion 17.

The ends of the two electrode wires 21, 21 are connected to each other via a resistor 31. The resistor 31 has an arbitrary resistance value. In this embodiment, the resistor 31 has a resistance value of 1 kΩ.

The electrode wire 21 is provided with a conductor 22 and a coating 23 .
The conductor 22 may be a metal wire used in the pressure-sensitive sensor 10. For example, a copper wire, a soft copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like may be used as the conductor 22. In order to improve heat resistance, a metal wire having an outer periphery plated with a metal such as tin, nickel, silver, or gold may be used as the conductor 22.

Furthermore, a bunched stranded conductor made of twisted metal wires may be used as the conductor 22. The outer diameter of the conductor 22 may be changed as appropriate depending on the electrical characteristics required for the electrode wire 21, and there are no particular limitations on the thickness of the outer diameter.

The coating 23 is a member that covers the outer circumference of the conductor 22. The coating 23 is formed using a material that is both conductive and flexible. The thickness of the coating 23 can be changed as appropriate depending on the conductivity and flexibility required for the electrode wire 21.

The coating 23 of this embodiment is formed using a composition containing a styrene-based thermoplastic elastomer and a conductive agent. The composition of the coating 23 may further contain an olefin-based crystalline resin. When an olefin-based crystalline resin is further contained, the amount of the olefin-based crystalline resin in the coating 23 is preferably 10 parts by mass or more and 70 parts by mass or less out of a total of 100 parts by mass including the styrene-based thermoplastic elastomer. The composition of the coating 23 may further contain a rubber component.

The composition of coating 23 may contain other additives as necessary, such as processing aids, oils, flame retardants, flame retardant assistants, crosslinking assistants, UV absorbers, antioxidants, copper inhibitors, lubricants, fillers, compatibilizers, stabilizers, and colorants.

It is preferable that the styrene-based thermoplastic elastomer contained in the composition of the coating 23 is the same elastomer as the styrene-based thermoplastic elastomer contained in the composition of the inner layer 13. By using a similar elastomer, it becomes easier to ensure adhesion between the inner layer 13 and the coating 23. Specifically, it becomes easier to ensure adhesion that prevents the coating 23 from peeling off from the inner layer 13 even if the process of deforming the pressure sensor 10 and restoring it to its original state is repeated.

The conductive agent is a conductive agent that imparts electrical conductivity to the styrene-based thermoplastic elastomer. Carbon black can be used as the conductive agent. Examples of carbon black that can be used include furnace black, ketjen black, acetylene black, channel black, thermal black, and lamp black.

The carbon black may be used alone as the conductive agent, or two or more kinds may be used in combination.
When used as a conductive agent, it is preferable to use Ketjen black. Compared to other conductive agents, Ketjen black can obtain excellent conductivity with a small amount of compounding. By reducing the amount of conductive agent compounded in the coating 23 and ensuring conductivity, it is easy to maintain the flexibility of the electrode wire 21. The particle size of the carbon black is not particularly limited.

The amount of conductive agent is preferably 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the total of the styrene-based thermoplastic elastomer and the olefin-based crystalline resin in the coating 23. By making the amount of conductive agent 10 parts by mass or more, the desired conductivity can be obtained in the coating 23. By making the amount of conductive agent 100 parts by mass or less, the composition of the coating 23 is less likely to harden due to the incorporation of the conductive agent. In addition, it becomes easier to ensure the processability of the composition of the coating 23, and it becomes easier to maintain the flexibility and abrasion resistance of the coating 23. The amount of conductive agent can be appropriately changed depending on the conductivity required for the coating 23.

Next, the detection of external pressure by the pressure sensor 10 having the above configuration will be described. In other words, the switching function of the pressure sensor 10 will be described.
When the pressure sensor 10 is in use, a current is supplied from a power supply unit (not shown) that is connected to two electrode wires 21 that are drawn out from the end opposite the end where the resistor 31 is disposed.

When no external pressure is applied to the pressure sensor 10, a current is supplied from the power supply unit to one of the electrode wires 21. The current flowing through one of the electrode wires 21 flows through the resistor 31 to the other electrode wire 21. In this case, the resistance value measured in the pressure sensor 10 is the resistance value of the resistor 31.

The pressure sensor 10 may have an elastic insulator 11 composed of an outer layer 12 and an inner layer 13 as shown in FIG. 2, or may be a pressure sensor 10A having an elastic insulator 11A composed of a single layer (corresponding to the first layer) 12A as shown in FIG. 3.

The pressure-sensitive sensor 10A includes an elastic insulator 11A and a plurality of electrode wires 21A.
The elastic insulator 11A is a member that holds a plurality of electrode wires 21A, 21A therein, similar to the elastic insulator 11. The elastic insulator 11A is also a member formed in an elongated shape, and is a member formed in a cylindrical shape with a hollow portion 17 provided therein.

The elastic insulator 11A is entirely composed of a single layer 12A. A hollow portion 17 is formed inside the single layer 12A. The single layer 12A is preferably formed using a composition containing an olefin-based thermoplastic elastomer, similar to the outer layer 12. The single layer 12A is preferably formed using a composition containing an olefin-based thermoplastic elastomer having an olefin-based resin in the continuous phase and a cross-linked rubber component in the dispersed layer. Furthermore, the single layer 12A is more preferably formed using a composition containing an olefin-based thermoplastic elastomer having polypropylene in the continuous phase and cross-linked ethylene propylene diene rubber (EPDM) in the dispersed layer.

The composition constituting the single layer 12A may contain other additives as necessary, such as processing aids, oils, flame retardants, flame retardant assistants, crosslinking assistants, UV absorbers, antioxidants, copper damage inhibitors, lubricants, fillers, compatibilizers, stabilizers, and colorants.

The two electrode wires 21A, 21A are arranged at a distance from each other on the inner circumferential surface of the hollow portion 17, similar to the electrode wire 21. The electrode wire 21A is provided with a conductor 22 and a coating (second layer) 23A.

The coating 23A is a member that covers the outer circumference of the conductor 22. The coating 23A is formed using a material that is both conductive and flexible. The thickness of the coating 23A can be changed as appropriate depending on the conductivity and flexibility required for the electrode wire 21A.

The coating 23A is formed using a composition containing a styrene-based thermoplastic elastomer, an olefin-based crystalline resin, and a conductive agent. The composition of the coatings 23 and 23A may further contain a rubber component.

The styrene-based thermoplastic elastomer contained in the composition of coating 23A is preferably an elastomer similar to the styrene-based thermoplastic elastomer contained in the composition of coating 23. The olefin-based crystalline resin contained in the composition of coating 23A is preferably a crystalline resin similar to the olefin-based crystalline resin contained in the composition of single layer 12A. The conductive agent contained in the composition of coating 23A is preferably a conductive agent similar to the conductive agent contained in the composition of coating 23.

The composition of coating 23A may contain other additives as necessary, such as processing aids, oils, flame retardants, flame retardant assistants, crosslinking assistants, UV absorbers, antioxidants, copper inhibitors, lubricants, fillers, compatibilizers, stabilizers, and colorants.

Furthermore, the pressure-sensitive sensor 10 may be a pressure-sensitive sensor 10B having an elastic insulator 11B further provided with an outermost layer 14B, as shown in FIG.
The pressure-sensitive sensor 10B is provided with an elastic insulator 11B and a plurality of electrode wires 21. The elastic insulator 11B is composed of an outer layer 12, an inner layer 13, and an outermost layer 14B.

The outermost layer 14B forms the outer peripheral portion of the elastic insulator 11B and covers the periphery of the outer layer 12. The outermost layer 14B may be formed using a composition containing thermoplastic polyurethane, a composition containing thermoplastic polyurethane and an acid-modified polymer, or the like.

Thermoplastic polyurethane is obtained by reacting a diol component, a diisocyanate component, and, if necessary, a chain extender. The outermost layer 14B contributes to the mechanical properties and flexibility of the outermost layer 14B. As components of thermoplastic polyurethane, polyester-based polyurethanes (adipate-based, caprolactone-based, polycarbonate-based, etc.) and polyether-based polyurethanes can be used. From the viewpoint of resistance to moisture and heat, polyether-based polyurethanes are preferred.

As the diol component constituting the thermoplastic polyurethane, for example, aliphatic diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; alicyclic diols such as cyclohexanedimethanol and cyclohexanediol, etc., can be used. These may be used alone or in combination of two or more.

Examples of diisocyanate components constituting thermoplastic polyurethane include fatty acids such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexylmethane diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, isopropylidenebis(4-cyclohexylisocyanate), methylcyclohexane diisocyanate, and isophorone diisocyanate. Aliphatic or alicyclic diisocyanates, 2,4- or 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 3-methyldiphenylmethane-4,4'-diisocyanate, m- or p-phenylene diisocyanate, chlorophenylene-2,4-diisocyanate, naphthalene-1,5-diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, and other aromatic diisocyanates can be used. These may be used alone or in combination of two or more.

The acid-modified polymer is a polymer modified with an unsaturated carboxylic acid or its derivative, which enhances the adhesion of the outermost layer 14B to the outer layer 12.

Polymers that can be used to form the acid-modified polymer include crystalline resins such as polypropylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, polybutene, poly-4-methyl-pentene-1, ethylene-butene-hexene terpolymer, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-glycidyl methacrylate copolymer; rubbers such as ethylene-propylene-diene copolymer, ethylene-propylene copolymer, ethylene-butene-1-diene copolymer, ethylene-octene-1-diene copolymer, acrylonitrile butadiene rubber, and acrylic rubber; and thermoplastic elastomers such as polyolefins, styrenes, polyesters, and polyamides.

As unsaturated carboxylic acids, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. can be used, and as derivatives of unsaturated carboxylic acids, metal salts, amides, esters, anhydrides, etc. of the above unsaturated carboxylic acids can be used, and among these, maleic anhydride is preferred.

FIG. 5 is a cross-sectional view illustrating a state in which an external pressure F is applied to the pressure-sensitive sensor 10. As shown in FIG.
Next, a description will be given of detection of the external pressure F by the pressure sensor 10. Note that since the detection of the external pressure F by the pressure sensor 10A and the pressure sensor 10B is similar, a description thereof will be omitted.

When an external pressure F is applied to the pressure sensor 10, as shown in FIG. 5, the elastic insulator 11 elastically deforms at the location where the external pressure F is applied. As the elastic insulator 11 deforms, the electrode wires 21, 21 arranged in the hollow portion 17 also bend, and the electrode wires 21, 21 come into contact with each other.

Even when the electrode wires 21, 21 are in contact with each other, a current flows from one electrode wire 21 to the other electrode wire 21. Therefore, the resistance value measured by the pressure sensor 10 varies from the resistance value of resistor 31.

For example, when the power supply unit supplies current at a constant voltage, the value of the current supplied to the pressure sensor 10 changes. By detecting this change in the current value, it is possible to detect that an external pressure F has been applied to the pressure sensor 10.

Next, a method for manufacturing the pressure-sensitive sensor 10 having the above configuration will be described. Note that the manufacturing methods for the pressure-sensitive sensors 10A and 10B are similar, so the description will be omitted.

First, an electrode wire 21 is prepared, in which a coating 23 is provided on the outer periphery of a conductor 22. The electrode wire 21 is produced by extruding a composition onto the outer periphery of the conductor 22 to form the coating 23. The composition that forms the coating 23 contains the above-mentioned styrene-based thermoplastic elastomer and conductive agent.

Next, the core is formed. A long central spacer (not shown) is placed in the center of the core. In addition, two electrode wires 21 and four long peripheral spacers (not shown) are placed around the central spacer. The peripheral spacer is placed between the two electrode wires 21, and the two electrode wires 21 are placed so that they do not come into contact with each other.

The two electrode wires 21 and the four surrounding spacers arranged around the central spacer are twisted together. The two electrode wires 21 are arranged to extend in a spiral shape along the longitudinal direction of the central spacer and are arranged opposite each other.

Next, the inner layer 13 of the elastic insulator 11 is formed on the outer periphery of the core. The inner layer 13 is formed by extruding a composition on the outer periphery of the core. The inner layer 13 has a generally cylindrical shape that covers the core. The composition of the inner layer 13 contains the above-mentioned styrene-based thermoplastic elastomer and olefin-based crystalline resin.

Furthermore, an outer layer 12 is formed on the outer periphery of the inner layer 13 of the elastic insulator 11. The outer layer 12 is formed by extruding a composition on the outer periphery of the inner layer 13. The outer layer 12 has a substantially cylindrical shape that covers the inner layer 13. The composition of the outer layer 12 contains the above-mentioned olefin-based thermoplastic elastomer.

Then, a hollow portion 17 is formed. The hollow portion 17 is a space formed by removing one central spacer and four peripheral spacers from the elastic insulator 11. Two electrode wires 21, 21 remain in the elastic insulator 11.

The two electrode wires 21, 21 are arranged along the inner circumferential surface of the hollow portion 17 and are spirally wound in the longitudinal direction. The two electrode wires 21, 21 are also arranged at a distance from each other so as not to come into contact with each other, and are arranged opposite each other.

FIG. 6 is a schematic diagram illustrating a moisture permeability test device 100 for evaluating the pressure-sensitive sensor 10. As shown in FIG.
Next, evaluation of the pressure-sensitive sensor 10 and the pressure-sensitive sensor 10A having the above configuration will be described. First, a moisture permeability test of the pressure-sensitive sensor 10 will be described with reference to Fig. 6. The moisture permeability test device 100 has a high-temperature and high-humidity chamber 110, a power source 120, a power line 130, and a connection part 140.

The high-temperature, high-humidity tank 110 is a container in which the pressure sensor 10 is placed and has the function of maintaining the interior at a predetermined temperature and humidity. The high-temperature, high-humidity tank 110 is provided with an opening 111 through which the pressure sensor 10 passes.

The power supply 120 is a device that supplies power to the pressure sensor 10. The power supply 120 is disposed outside the high-temperature, high-humidity chamber 110. The power supply 120 is, for example, a constant-voltage power supply that applies a predetermined voltage to the pressure sensor 10. The power supply 120 is also a power supply that has the function of detecting the value of the current supplied to the pressure sensor 10.

The power supply line 130 and the connection part 140 are arranged outside the high-temperature and high-humidity chamber 110 and are components used to supply power from the power supply 120 to the pressure sensor 10. The power supply line 130 is a wiring that connects the power supply 120 and the connection part 140. Publicly known wiring can be used as the power supply line 130.

The connection part 140 is a device to which the end of the pressure sensor 10 is attached. The power line 130 is also connected to the connection part 140. The connection part 140 may be a known configuration or a combination of known configurations.

Next, the conditions for the moisture permeability test will be described.
The inside of the high-temperature and high-humidity chamber 110 is adjusted to, for example, a temperature of 80° C. and a relative humidity of 90%. For testing, a pressure-sensitive sensor 10 having a length of 1 m or more and 2 m or less is used. Here, the test was performed using a pressure-sensitive sensor 10 having a length of 1.5 m.

The central portion of the pressure sensor 10 is placed inside the high-temperature, high-humidity tank 110. The end of the pressure sensor 10 connected to the connection portion 140 and the other end are placed outside the high-temperature, high-humidity tank 110 through the opening 111. In other words, the pressure sensor 10 is placed so that a temperature difference occurs between the central portion and both ends. Here, the central portion 1m is placed inside the high-temperature, high-humidity tank 110.

In the moisture permeability test, the resistance value of the pressure sensor 10 is recorded. If the fluctuation range of the resistance value is within a specified range during the specified test period, it is judged as passing, and if it exceeds the specified range, it is judged as failing. Here, the specified test period is 1000 hours, and the specified range of the fluctuation range is ±5%.

Fig. 7 is a table for explaining the evaluation results obtained by the moisture permeability test device 100. In Fig. 7, the evaluation results of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown.
Example 1 is a pressure-sensitive sensor 10 having a structure shown in Fig. 2. That is, Example 1 is a pressure-sensitive sensor 10 provided with an elastic insulator 11 having an outer layer 12 and an inner layer 13.

The pressure-sensitive sensor 10 of the first embodiment is fabricated as described below.
First, the electrode wire 21 is prepared. Specifically, a conductor 22 is prepared, which is a stranded wire in which seven copper wires are twisted together and has an outer diameter of 0.127 mm. A composition containing a styrene-based thermoplastic elastomer, a polyolefin, and a conductive agent is extruded onto the outer periphery of the conductor 22 to form a coating 23. The outer diameter of the electrode wire 21 with the coating 23 formed thereon is 0.8 mm.

The composition used to form the coating 23 contains 50 parts by weight of a styrene-based elastomer (Septon 4055; SEEPS, manufactured by Kuraray, styrene content 30% by weight), 50 parts by weight of polypropylene (Novatec FY6C, manufactured by Japan Polypropylene), 100 parts by weight of oil (Lucant HC-40, manufactured by Mitsui Chemicals), and 50 parts by weight of carbon black (Ketjenblack EC600JD, manufactured by Lion).

Next, a core including electrode wires 21 is produced. One spacer wire having the same outer diameter as the electrode wire 21 is placed in the center of the core. Two electrode wires 21 and four spacer wires having the same outer diameter as the electrode wire 21 are twisted around the spacer wire placed in the center to produce the core. Two spacer wires are placed between the two electrode wires 21.

Then, the elastic insulator 11 is formed around the core. Specifically, the composition constituting the inner layer 13 and the composition constituting the outer layer 12 are simultaneously extruded around the outer periphery of the core to form the elastic insulator 11.

The composition constituting the inner layer 13 is a composition containing a styrene-based thermoplastic elastomer and a polyolefin, with the polyolefin being 10 to 70 parts by mass out of a total of 100 parts by mass. Specifically, a composition containing 80 parts by mass of a styrene-based elastomer (Septon 4055 by Kuraray; SEEPS, styrene content 30% by mass), 20 parts by mass of polypropylene (Novatec FY6C by Japan Polypropylene), 90 parts by mass of oil (Lucant HC-40 by Mitsui Chemicals), and 90 parts by mass of calcium carbonate (Softon 1200 by Bihoku Funka Kogyo).

The composition that constitutes the outer layer 12 is a composition that contains an olefin-based thermoplastic elastomer. Specifically, an olefin-based thermoplastic elastomer (VP-A90ET from Aronkasei Co., Ltd.) was used. VP-A90ET has a continuous layer of polypropylene (PP) and a dispersed layer of cross-linked ethylene propylene diene rubber (EPDM).

The inner layer 13 is formed to have an outer diameter of 4 mm, and the outer layer 12 is formed to have a thickness of 0.3 mm. Once the elastic insulator 11 is formed, the spacer wire of the core is pulled out to form the pressure sensor 10 of Example 1.

Example 2 is a pressure-sensitive sensor 10A having the structure shown in Figure 3. In other words, Example 2 is a pressure-sensitive sensor 10A provided with an elastic insulator 11A having a single layer 12A.

The pressure-sensitive sensor 10A of the second embodiment is fabricated as described below.
First, the electrode wire 21A is prepared. Specifically, a conductor 22 is prepared in the same manner as the electrode wire 21. A composition containing a styrene-based thermoplastic elastomer, a polyolefin, and a conductive agent is extruded onto the outer periphery of the conductor 22 to form a coating 23A. The outer diameter of the electrode wire 21A with the coating 23A formed thereon is 0.8 mm.

The composition used to form the coating 23A contains 50 parts by mass of a styrene-based elastomer (Septon 4055; SEEPS, manufactured by Kuraray, styrene content 30% by mass), 50 parts by mass of polypropylene (Novatec FY6C, manufactured by Japan Polypropylene), 100 parts by mass of oil (Lucant HC-40, manufactured by Mitsui Chemicals), and 50 parts by mass of carbon black (Ketjenblack EC600JD, manufactured by Lion).

Next, a core including the electrode wire 21A is fabricated. The method of fabricating this core is similar to the method of fabricating the core in the pressure-sensitive sensor 10, and therefore a description thereof will be omitted.
Once the core is fabricated, elastic insulator 11A is formed around the core. Specifically, the composition that makes up single layer 12A is extruded around the periphery of the core to form elastic insulator 11A.

The composition that constitutes the single layer 12A is a composition that contains an olefin-based thermoplastic elastomer. Specifically, an olefin-based thermoplastic elastomer (VP-A90ET from Aronkasei Co., Ltd.) is used. VP-A90ET has a continuous layer of polypropylene (PP) and a dispersed layer of cross-linked ethylene propylene diene rubber (EPDM).

The single layer 12A is formed to have an outer diameter of 4.6 mm. Once the elastic insulator 11A is formed, the spacer wire of the core is pulled out to form the pressure sensor 10A of Example 1 and Example 2.

Comparative example 1 is a pressure sensor provided with an elastic insulator having an outer layer formed from a thermoplastic urethane and an inner layer formed from a styrene-based thermoplastic elastomer.

The pressure sensor of Comparative Example 1 is fabricated as described below.
First, an electrode wire is fabricated in the same manner as in the pressure-sensitive sensor 10 of Example 1. Then, a core including the electrode wire is fabricated. The material and fabrication method of the conductor of the electrode wire are the same as those of the pressure-sensitive sensor 10 of Example 1, and the description thereof is omitted. A composition including a styrene-based thermoplastic elastomer and a conductive agent is extruded around the outer periphery of the conductor to form a coating. The outer diameter of the coated electrode wire is 0.8 mm.

The coating composition used was one containing 50 parts by mass of styrene-based elastomer (Septon 4055; SEEPS, manufactured by Kuraray, styrene content 30% by mass), 100 parts by mass of oil (Lucant HC-40, manufactured by Mitsui Chemicals), and 50 parts by mass of carbon black (Ketjenblack EC600JD, manufactured by Lion).

Next, a core including the electrode wires is fabricated. The method of fabricating this core is the same as the method of fabricating the core in the pressure-sensitive sensor 10, and therefore a description thereof will be omitted.
Once the core is made, an elastic insulator is formed around the core by simultaneously extruding the composition that constitutes the inner layer and the composition that constitutes the outer layer around the core to form the elastic insulator.

The composition used for the inner layer was a composition containing a styrene-based thermoplastic elastomer. Specifically, the composition used contained 100 parts by mass of a styrene-based elastomer (Septon 4055 by Kuraray; SEEPS, styrene content 30% by mass), 100 parts by mass of oil (Lucant HC-40 by Mitsui Chemicals), and 50 parts by mass of carbon black (Ketjenblack EC600JD by Lion).

The composition used to make up the outer layer was an ether-based polyurethane composition. Specifically, a composition containing "Elastollan 1180A" manufactured by BASF Japan Ltd. was used.

The inner layer is formed to have an outer diameter of 4 mm, and the outer layer is formed to have a thickness of 0.3 mm. Once the elastic insulator is formed, the spacer wire in the core is pulled out to form the pressure sensor of Comparative Example 1.

Comparative example 2 is a pressure sensor provided with an elastic insulator having an outer layer formed from a thermoplastic urethane and an acid-modified polymer and an inner layer formed from a styrene-based thermoplastic elastomer.

The pressure sensor of Comparative Example 2 is fabricated as described below.
First, an electrode wire is produced in the same manner as the pressure-sensitive sensor 10 of Example 1. Then, a core including the electrode wire is produced. The material and production method of the conductor of the electrode wire are the same as those of the pressure-sensitive sensor 10 of Example 1, and the description thereof will be omitted. A composition including a styrene-based thermoplastic elastomer and a conductive agent is extruded on the outer circumference of the conductor to form a coating. The composition constituting the coating is the same as the composition constituting the coating of Comparative Example 1. The outer diameter of the electrode wire with the coating is 0.8 mm.

Next, a core including the electrode wires is fabricated. The method of fabricating this core is the same as the method of fabricating the core in the pressure-sensitive sensor 10, and therefore a description thereof will be omitted.
Once the core is made, an elastic insulator is formed around the core by simultaneously extruding the composition that constitutes the inner layer and the composition that constitutes the outer layer around the core to form the elastic insulator.

The composition constituting the inner layer was the same as the composition constituting the inner layer of Comparative Example 1.
The composition constituting the outer layer was a composition containing an ether-based polyurethane and maleic anhydride copolymerized ethylene ethyl acrylate. Specifically, a composition containing an ether-based polyurethane ("Elastollan 1180A" manufactured by BASF Japan Ltd.) and maleic anhydride copolymerized ethylene ethyl acrylate ("Bondine LX4110" manufactured by Arkema K.K.) was used.

The inner layer is formed to have an outer diameter of 4 mm, and the outer layer is formed to have a thickness of 0.3 mm. Once the elastic insulator is formed, the spacer wire in the core is pulled out to form the pressure sensor of Comparative Example 2.

As a result of evaluation using the moisture permeability test device 100, the resistance fluctuation range of the pressure sensor 10 of Example 1 was within the specified range of ±5% of 1 kΩ even after the specified test period of 1000 hours had elapsed. As a result, the pressure sensor 10 of Example 1 was judged to have passed.

The pressure sensor 10A of Example 2 had a resistance value fluctuation range of within ±5% of 1 kΩ, which is the specified range, even after the specified test period of 1000 hours had elapsed. As a result, the pressure sensor 10A of Example 2 was judged to have passed.

The pressure sensor of Comparative Example 1 showed a resistance fluctuation range of more than ±5% of the specified range of 1 kΩ before the specified test period of 1000 hours had elapsed. As a result, the pressure sensor of Comparative Example 1 was determined to have failed.

The pressure sensor of Comparative Example 2 showed a resistance fluctuation range of more than ±5% of the specified range of 1 kΩ before the specified test period of 1000 hours had elapsed. As a result, the pressure sensor of Comparative Example 2 was determined to have failed.

According to the pressure-sensitive sensor 10, 10B configured as described above, at least the outer layer 12 containing an olefin-based thermoplastic elastomer is provided on the elastic insulator 11, 11B. The olefin-based thermoplastic elastomer has a lower moisture permeability than the styrene-based thermoplastic elastomer, and water vapor is less likely to penetrate into the inside than the outer layer 12. Since water vapor is less likely to penetrate into the pressure-sensitive sensor 10, 10B, condensation is less likely to occur inside the pressure-sensitive sensor 10, 10B. This makes it easier to suppress the occurrence of short circuits in the electrode wires 21, 21.

In addition, according to the pressure sensor 10A, a single layer 12A containing an olefin-based thermoplastic elastomer as a component is provided in the elastic insulator 11A. The olefin-based thermoplastic elastomer has lower moisture permeability than the styrene-based thermoplastic elastomer, and water vapor is less likely to penetrate into the interior than the single layer 12A. Since water vapor is less likely to penetrate into the interior of the pressure sensor 10A, condensation is less likely to occur inside the pressure sensor 10A. This makes it easier to suppress the occurrence of short circuits in the electrode wires 21A, 21A.

The inner layer 13, which is adjacent to the outer layer 12, contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin. The olefin-based crystalline resin has adhesive properties with the olefin-based thermoplastic elastomer of the outer layer 12. Compared to when the inner layer 13 is formed only from a styrene-based thermoplastic elastomer, the adhesive properties between the outer layer 12 and the inner layer 13 are higher. This makes it easier to suppress the occurrence of problems caused by peeling between the outer layer 12 and the inner layer 13.

In addition, the coating 23A, which is the portion adjacent to the single layer 12A, contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin. The olefin-based crystalline resin has adhesive properties with the olefin-based thermoplastic elastomer of the single layer 12A. Compared to when the coating 23A is formed only from a styrene-based thermoplastic elastomer, the adhesive properties between the single layer 12A and the coating 23A are higher. This makes it easier to suppress the occurrence of problems caused by peeling between the single layer 12A and the coating 23A.

By making the outer layer 12 the first layer in the claims of the pressure sensor 10, it becomes easier to reduce the moisture permeability of the outermost part of the pressure sensor 10. Therefore, water vapor is less likely to penetrate into the inside of the pressure sensor 10. In addition, by making the inner layer 13 the second layer in the claims, the elastic insulator 11 is less likely to peel off into the outer layer 12 and the inner layer 13.

As in the pressure-sensitive sensor 10A, by making the entire elastic insulator 11A the first layer in the scope of the claims and a single layer 12A, it becomes easier to ensure a layer thickness with low moisture permeability compared to when it is partially made into the first layer. This makes it even more difficult for water vapor to penetrate into the interior of the pressure-sensitive sensor 10A. Also, by making the coating 23A the second layer in the scope of the claims, the elastic insulator 11A and the electrode wire 21A are less likely to peel off.

By making the proportion of olefin-based crystalline resin in the inner layer 13 of the pressure-sensitive sensor 10 10 parts by mass or more, it becomes easier to ensure adhesion between the outer layer 12 and the inner layer 13. In other words, if it is less than 10 parts by mass, the outer layer 12 and the inner layer 13 are more likely to peel off from each other, which makes it more likely that defects will occur.

By setting the proportion of olefin-based crystalline resin in the inner layer 13 to 70 parts by mass or less, it becomes easier to ensure the flexibility of the inner layer 13. As a result, the pressure sensor 10 becomes more easily deformed, making it easier to install the pressure sensor 10 and ensuring the sensitivity of the pressure sensor. In other words, if it exceeds 70 parts by mass, the inner layer 13 becomes harder and it becomes more difficult to deform the pressure sensor 10. As a result, it becomes more difficult to install the pressure sensor 10 and the sensitivity of the pressure sensor 10 is more likely to decrease.

By making the proportion of olefin-based crystalline resin in the coating 23A of the pressure-sensitive sensor 10A 10 parts by mass or more, it becomes easier to ensure adhesion between the single layer 12A and the coating 23A. In other words, if it is less than 10 parts by mass, the first layer and the coating 23A are more likely to peel off, which makes it more likely that defects will occur.

In addition, by setting the proportion of olefin-based crystalline resin in the coating 23A to 70 parts by mass or less, it becomes easier to ensure the flexibility of the coating 23A. This makes it easier for the pressure sensor 10A to deform, making it easier to install the pressure sensor 10A, and making it easier to ensure the sensitivity of the pressure sensor 10A. In other words, if it exceeds 70 parts by mass, the coating 23A becomes hard and it becomes difficult to deform the pressure sensor 10A. This makes it difficult to install the pressure sensor 10A, and the sensitivity of the pressure sensor 10A is likely to decrease.

The technical scope of the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the present invention is not limited to the above-mentioned embodiments, and may be applied to an embodiment in which these embodiments are appropriately combined, and is not particularly limited.

10, 10A, 10B... pressure sensor, 11, 11A, 11B... elastic insulator, 12... outer layer (first layer), 12A... single layer (first layer), 13... inner layer (second layer), 17... hollow portion, 21, 21A... electrode wire, 23... coating, 23A... coating (second layer)

Claims (5)

a cylindrical elastic insulator having a hollow portion extending along a longitudinal direction;
a plurality of electrode wires arranged along an inner circumferential surface of the hollow portion of the elastic insulator and spaced apart from one another;
The elastic insulator is provided with at least a first layer including an olefin-based thermoplastic elastomer,
At least one of the elastic insulator and the coating of the electrode wire is provided with a second layer that is adjacent to the first layer,
The second layer of the pressure-sensitive sensor includes a styrene-based thermoplastic elastomer and an olefin-based crystalline resin. the elastic insulator has an outer layer forming an outer peripheral portion and an inner layer forming a hollow portion,
2. The pressure sensor of claim 1, wherein said outer layer is said first layer and said inner layer is said second layer. the elastic insulator is entirely the first layer;
2. The pressure sensor according to claim 1, wherein at least a portion of said coating adjacent to said first layer is said second layer. The pressure sensor according to any one of claims 1 to 3, wherein the amount of the olefin-based crystalline resin in the second layer is 10 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the total of the olefin-based crystalline resin and the styrene-based thermoplastic elastomer. The pressure-sensitive sensor according to claim 2, wherein the coating of the electrode wire contains a styrene-based thermoplastic elastomer and an olefin-based crystalline resin.

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