JP7385403B2 - sensor system - Google Patents

Description

The present invention relates to a sensor system including a sensor element.

Conventionally, a sensor system including a sensor element having a piezoelectric sensor function is known. Such a sensor system typically uses a piezoelectric element as a sensor element, and more specifically, uses the positive piezoelectric effect of a piezoelectric material to apply an electric current to the sensor element (more specifically, the piezoelectric material). is configured to detect external force applied to the sensor.

A piezoelectric element used as a sensor element in such a sensor system may have a generally elongated linear shape, which may be referred to as cable-like or wire-like. For example, as disclosed in Patent Document 1, a core wire in which at least one layer of metal foil is spirally wound around a resin wire, an organic piezoelectric layer covering the core wire, and a conductor covering the organic piezoelectric layer A piezoelectric element includes a metal foil and a conductive layer, each of which functions as an electrode with an organic piezoelectric layer interposed therebetween.

Patent No. 6501958 Japanese Patent Application Publication No. 2017-120237 JP2018-87726A

A sensor system including a conventional piezoelectric element as a sensor element as described above applies a voltage to a piezoelectric layer based on a potential difference (voltage) between a metal foil in which an organic piezoelectric layer is interposed and a conductive layer. The sensor is configured to detect an external force. In such a piezoelectric element, when an external force is applied, the potential difference changes sharply and then attenuates, so the application of an external force can be detected by the change in potential difference (differential signal). If the applied external force does not change, the potential difference will not change, so it is not possible to determine whether there is a continuous external force. For example, when determining whether a person is present in a certain place, if the person is constantly present in the place, the external force due to the person's weight does not change, so it cannot be detected as a change in potential difference. The only way to detect it is by using vital signs (pulse and breathing) that can cause changes in external force and, in turn, changes in potential difference. However, when detecting by vital signs, the vital signals have a low frequency (for example, pulse is about 1 kHz, breathing is about 0.3 Hz), so changes in potential difference (differential signal ), which requires waveform analysis, making immediate judgment difficult.

Therefore, if it is possible to add a capacitive sensor function to a sensor system that includes a sensor element that has a piezoelectric sensor function, it will be possible to easily and immediately check whether an object such as a person is present. This is more convenient because it allows judgment to be made.

Sensor systems including a sensor element having a piezoelectric sensor function, to which a capacitive sensor function is added, are disclosed in Patent Documents 2 and 3. However, in the sensor systems disclosed in Patent Documents 2 and 3, in addition to a sensor element having a piezoelectric sensor function, another conductor (patent document) is used to measure capacitance between the sensor element and the sensor element. In Document 2, it is "another conductive fiber", and in Patent Document 3, it is an "electrode body"). Such conventional sensor systems have the disadvantage that they must be configured by combining a sensor element and another conductor, making the system configuration complex. Until now, no sensor system has been known that achieves both a piezoelectric sensor function and a capacitive sensor function without using a conductor separate from the sensor element having the piezoelectric sensor function.

An object of the present invention is to provide a novel sensor system having both piezoelectric sensor function and capacitive sensor function.

In a sensor system including a sensor element, the present inventors provide both a piezoelectric sensor function and a capacitive sensor function by effectively utilizing the conductor of the sensor element that has a piezoelectric sensor function. As a result of intensive research and verification, the present invention was completed.

According to one gist of the invention:
A flexible sensor element including a core wire having a conductive surface, a piezoelectric layer covering the core wire, and a conductive layer covering the piezoelectric layer;
a piezoelectric detection unit that detects an external force applied to the piezoelectric layer based on a potential difference between the conductor and the conductor layer;
A sensor system is provided, including a capacitance detection section that detects the presence of an object based on capacitance in either the conductor or the conductor layer.

According to the present invention, a sensor system uses a flexible sensor element including a core wire having a conductive surface, a piezoelectric layer covering the core wire, and a conductive layer covering the piezoelectric layer, A piezoelectric sensor function is realized based on the potential difference between the conductor and the conductor layer, and a capacitive sensor function is realized based on the capacitance in either the conductor or the conductor layer. This provides a novel sensor system having both a piezoelectric sensor function and a capacitive sensor function.

1 is a schematic diagram showing a sensor system in one embodiment of the present invention, in which (a) shows a partially cutaway side view of a sensor element, and (b) shows a cross-sectional view taken along line XX in (a). FIG. 2C is a diagram illustrating an example of the configuration of a sensor system (however, only electrode extension portions A and B are shown as sensor elements). FIG. 1C is a diagram corresponding to FIG. 1C, and is a diagram illustrating another configuration example of the sensor system in one embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sensor device in which a textile product is combined with a sensor element that can be used in a sensor system according to an embodiment of the present invention, in which (a) to (c) show schematic top views of various examples of the sensor device. 2 is a graph showing changes over time in capacitance and potential difference when a human performs a motion of "riding" on a sensor element, measured by the sensor system according to the embodiment of the present invention. 3 is a graph showing changes over time in capacitance and potential difference when a human performs an action of "getting down" from a sensor element, as measured by the sensor system according to the embodiment of the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Referring to FIG. 1, a sensor system 30 of the present embodiment schematically includes a sensor element 20, a piezoelectric detection section 21, and a capacitance detection section 23. Note that the electrode extension parts A and B of the sensor element 20 shown in FIGS. 1(a) and 1(b) are connected to A and B shown in FIG. 1(c).

As shown in FIGS. 1A and 1B, the sensor element 20 that can be used in this embodiment includes a core wire 5 having a surface of a conductor 3, a piezoelectric layer 7 covering the core wire 5, and a piezoelectric layer 7 that covers the core wire 5. A conductor layer 9 covering layer 7 is included, and optionally an insulator layer 11 covering conductor layer 9 is further included. In the sensor element 20, the conductor (inner conductor layer) 3 and the conductor layer (outer conductor layer) 9 each function as an electrode with the piezoelectric layer 7 interposed therebetween (see FIG. 1(b) )reference). The sensor element 20 has an elongated linear shape as a whole, which may be referred to as a cable shape or a wire shape, and is configured to have flexibility as a whole. In the sensor element 20, the core wire 5, the piezoelectric layer 7, the conductor layer 9, and if present, the insulator layer 11 may be arranged substantially coaxially, but the present invention is not limited to such a configuration.

The core wire 5 may have the surface of the conductor 3, and even if the entire core wire 5 is made of the conductor 3, all or part of the surface of the core wire 5 (from one end of the core wire 5 to the other There is no particular limitation as long as it extends continuously over the end, but even if the conductor 3 consists of at least 60% (preferably at least 80%) of the conductor 3 and the inside of the core wire 5 consists of other materials. good. Preferred examples of the conductor 3 include copper and copper-containing alloys (eg, copper-tin alloy, copper-silver alloy, etc.), and may or may not be plated with tin or the like. These materials exhibit high electrical conductivity, and since copper exhibits high ductility, they have excellent mechanical strength and can further enhance the flexibility and bending resistance of the sensor element 20.

For example, the core wire 5 may be configured by covering the resin wire 1 with the conductor 3. More specifically, the core wire 5 may be configured by winding at least one layer of metal foil (conductor) 3 around the resin wire 1 in a spiral shape (preferably at a constant spiral pitch), and may be configured by winding the resin wire 1 in a spiral manner (preferably at a constant spiral pitch). However, it does not need to be wrapped in an overlapping manner, and may be wound in a gap. By having such a configuration, when the core wire 5 is pulled, the tensile stress mainly acts on the resin wire 1 and the entire core wire 5 can be elongated, preferably exhibiting a tensile elongation of 3% or more, and a relatively small Even when bent at the radius of curvature, no distortion remains in the core wire 5, and it exhibits excellent flexibility. Moreover, since the core wire 5 has such a configuration, conduction is hard to be broken even if it is repeatedly bent, and exhibits excellent bending resistance.

The resin wire 1 may be a generally linear member made of a resin material. Examples of such resin materials include aromatic polyamides (aramids, such as para-aramids, meta-aramids, etc.), aliphatic polyamides (nylons), polyesters, polyvinyl alcohol, polyacrylonitrile, polyarylates, polyolefins, polyurethanes, and carbon fibers. (for example, carbon nanotubes (CNT), etc.).

The outer dimensions of the core wire 5 (the outer diameter if it has a circular cross section, the maximum outer dimension of the cross section if it has a non-circular cross section, and the same applies hereinafter) are not particularly limited, and may vary depending on the specifications required for the sensor element 20. It can be. The core wire 5 can be made extremely thin, and its external dimensions can be, for example, from 0.05 to 1.5 mm, in particular 1.0 mm or less, more particularly 0.5 mm or less, even more particularly 0.3 mm or less. It can be.

The piezoelectric layer 7 is provided between the conductor 3 and the conductor layer 9 so that they do not come into contact with each other. The piezoelectric layer 7 may be made of a flexible piezoelectric material, for example, an organic piezoelectric material, a composite of an organic piezoelectric material and an inorganic piezoelectric material, or an organic material (excluding the organic piezoelectric material) and an inorganic piezoelectric material. It can be composed of a complex with.

The organic piezoelectric material may be either a polymer or a low-molecular material, such as polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer (copolymer of vinylidene fluoride and trifluoroethylene (P( VDF/TrFE)), vinylidene fluoride and tetrafluoroethylene copolymers (P(VDF/TeFE))), polyvinylidene cyanide, vinylidene cyanide copolymers, odd nylons (nylon 9, nylon 11), aromatic nylon, polylactic acid, polyhydroxycarboxylic acid, cellulose derivatives, polyurea, etc. may be used. Among these, the piezoelectric layer 7 preferably contains at least one selected from the group consisting of P(VDF/TrFE) and P(VDF/TeFE).

A composite of an organic piezoelectric material and an inorganic piezoelectric material is a composite of an organic piezoelectric material and an inorganic piezoelectric material so that the composite as a whole exhibits flexibility. ) and/or stacked. The content of the inorganic piezoelectric material in the composite may be selected as appropriate, but in order to improve flexibility, it should be, for example, 30% by mass or less, preferably 20% by mass or less of the composite (piezoelectric layer). Ru. As the organic piezoelectric material, materials similar to those described above may be used. Inorganic piezoelectric materials include, for example, lead-based ceramic piezoelectric materials (lead zirconate titanate, lead titanate, etc.) in which some of the lead is replaced with rare earth elements, such as lead lanthanum zirconate titanate. ), lead-free ceramic piezoelectric materials (alkali niobate-based, bismuth titanate-based, barium titanate-based, etc.), zinc oxide piezoelectric materials (ZnO), etc. may be used. ) may exist.

A composite of an organic material (excluding an organic piezoelectric material) and an inorganic piezoelectric material is a composite of an organic material and an inorganic piezoelectric material so that the composite as a whole exhibits flexibility. dispersed in an organic material) and/or layered. The content of the inorganic piezoelectric material in the composite may be selected as appropriate, but in order to improve flexibility while ensuring piezoelectric performance, for example, the content of the inorganic piezoelectric material in the composite (piezoelectric layer) should be 70% by mass or more and 90% by mass. % or less. The organic material does not exhibit piezoelectricity; for example, heat-resistant resins with a melting point of 200°C or higher include tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc. Polymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyimide (PI), polyamideimide (PAI), polyphenylene sulfide resin (PPS), polyetheretherketone resin (PEEK), liquid crystal polymer (LCP) and silicone resin. The same inorganic piezoelectric materials as those described above may be used.

The piezoelectric layer 7 may be formed directly on the core wire 5 by a solvent coating method or a melt extrusion method, or by wrapping or braiding a piezoelectric material in the form of a film or fiber. It may be formed to cover the core wire 5.

The thickness of the piezoelectric layer 7 is not particularly limited, and can be appropriately selected in consideration of the piezoelectric properties, flexibility, bending resistance, etc. desired for the sensor element 20. The thickness of the piezoelectric layer 7 may be, for example, 1 to 200 μm, particularly 100 μm or less, more particularly 50 μm or less.

The conductor layer 9 is provided so as to at least partially cover the piezoelectric layer 7 , and is preferably provided in close contact with the piezoelectric layer 7 .

The conductor layer 9 may be a flexible member as long as at least the surface in contact with the piezoelectric layer 7 is made of a material exhibiting conductivity. For the conductor layer 9, a conductor layer known as a shield may be used, and for example, a braided shield and a horizontally wound shield of metal wires can be used. Further, the conductor layer 9 may be at least one layer of metal foil spirally wound around the piezoelectric layer 7. In this case, the conductor layer 9 may be configured by winding at least one layer of metal foil around the piezoelectric layer 7 in a spiral shape (preferably at a constant spiral pitch), and even if the conductor layer 9 is wound in an overlapping manner, It may be unwound or gap-wound. Preferred examples of metal materials constituting metal wires and metal foils include copper and copper-containing alloys (e.g. copper-tin alloys, copper-silver alloys, etc.), even if they are plated with tin, silver, etc. , it is not necessary to have it. These materials exhibit high electrical conductivity, and since copper exhibits high ductility, they have excellent mechanical strength and can further enhance the flexibility and bending resistance of the sensor element 20.

The thickness of the conductor layer 9 is not particularly limited, and can be appropriately selected in consideration of the flexibility, bending resistance, etc. desired for the sensor element 20. The thickness of the conductor layer 9 may be, for example, from 5 to 500 μm, in particular up to 200 μm, more particularly up to 100 μm.

The outer dimensions of the conductor layer 9 may correspond to the outer dimensions of the sensor element 20 when the sensor element 20 does not have the insulator layer 11, and may be, for example, 0.05 to 2.2 mm, although not particularly limited, In particular it may be less than or equal to 1.5 mm, more particularly less than or equal to 1 mm.

Further, although not essential to this embodiment, the conductor layer 9 may be covered with an insulator layer 11. Insulator layer 11 may be provided to protect sensor element 20 electrically and/or physically. Such an insulator layer 11 can also be understood as a sheath.

The insulator layer 11 may be a flexible member as long as it is made of a material that exhibits insulation at least on its surface. The insulator layer 11 is made of, for example, an insulating wire (for example, a wire made of an insulating organic material such as polyamide, polyester, acrylic, polyolefin, rubber, silicone, urethane, polyarylate, aromatic polyamide, aliphatic polyamide, etc.). It may be a braided cord. The insulating layer 11 is made of an insulating material such as polyvinyl chloride, ethylene-vinyl acetate copolymer (EVA), polyolefin, polyester, polyamide, fluororesin (tetrafluoroethylene-perfluorocarbon resin) around the conductor layer 9. Extrusion coating of insulating organic materials such as alkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), PVDF, etc.), rubber, etc. It may also be formed by The insulating layer 11 may also be formed by covering the core wire 5 (by wrapping, tape wrapping, etc.) with an insulating material (for example, the above-mentioned insulating organic material) in the form of a film or tape. good.

The thickness of the insulator layer 11 is not particularly limited, and can be appropriately selected in consideration of the flexibility, bending resistance, etc. desired for the sensor element 20. The thickness of the insulator layer 11 may be, for example, from 10 to 1000 μm, in particular up to 700 μm, more especially up to 400 μm.

The outer dimensions of the insulator layer 11 may correspond to the outer dimensions of the sensor element 20 when the sensor element 20 has the insulator layer 11, and may be, for example, 0.07 to 4.2 mm, although not particularly limited, and in particular It may be less than or equal to 1.5 mm, more particularly less than or equal to 1 mm.

The sensor element 20 in this embodiment has excellent flexibility and bending resistance. In particular, the sensor element 20 is configured such that the core wire 5 is composed of a resin wire 1 covered with a conductor 3, the piezoelectric layer 7 is composed of an organic piezoelectric material, and the outer diameter of the sensor element 20 is 1 mm or less. is preferable, and as a result, it is possible to achieve superior flexibility and bending resistance while exhibiting piezoelectric performance. In the sensor element 20 of this embodiment, electrodes are drawn out from the conductor 3 and the conductor layer 9 by exposing the conductor 3 and the conductor layer 9 by any appropriate method (in FIG. (shown as drawers A and B).

In the sensor system 30 of this embodiment, the conductor 3 (electrode extension part A) and the conductor layer 9 (electrode extension part B) are electrically connected to the piezoelectric detection part 21, and the conductor layer 9 (electrode extension part B) is configured by being electrically connected to the capacitance detection section 23.

The piezoelectric detection unit 21 detects an external force applied to the piezoelectric layer 7 based on the potential difference (voltage) between the conductor 3 and the conductor layer 9. The piezoelectric detection unit 21 includes any suitable analysis means (for example, an amplifier, a differential filter, etc.) for analyzing the electric signal obtained by measuring the potential difference, a data storage and/or calculation means, an analysis result output means, etc. can be provided.

When an external force is applied to the sensor element 20 , the external force is applied to the piezoelectric layer 7 , causing a change in the potential difference (voltage) between the conductor 3 and the conductor layer 9 , and causing a change in the potential difference (voltage) between the conductor 3 and the conductor layer 9 . By analyzing this change, it is possible to detect that an external force has been applied. Conversely, when the external force that has been continuously applied to the sensor element 20 is removed, the external force that has been continuously applied to the piezoelectric layer 7 is removed, and the potential difference between the conductor 3 and the conductor layer 9 is reduced. By causing a change in voltage (voltage) opposite to the above and analyzing the change using the piezoelectric detection unit 21, it is possible to detect (discriminate) that the external force has been removed.

The capacitance detection unit 23 detects the presence of an object based on the capacitance in the conductor layer 9. The capacitance detection unit 23 is preferably grounded (GND) in order to be able to measure the capacitance in the conductor layer 9 well. The capacitance detection unit 23 includes any appropriate analysis means (for example, a resistor, etc.) for analyzing the electrical signal obtained by measuring capacitance, data storage and/or calculation means, and output of analysis results. Means etc. may be provided.

When an object exists near the sensor element 20, the electrical environment of the conductor layer 9 differs due to the presence of the object compared to a case where the object does not exist, and the level of capacitance in the conductor layer 9 ( Analyzing the capacitance with the capacitance detection unit 23, which is preferably grounded (GND), that is, detecting that a difference has occurred (e.g. , by setting the case where no object exists as a reference state, storing data on the capacitance level in the reference state, and comparing and calculating the data with the data on the capacitance level in the measurement state. It is possible to detect (determine) whether an object exists or not. The capacitance in the conductor layer 9 depends on the electrical environment around the conductor layer 9 and does not attenuate like the potential difference between the conductor 3 and the conductor layer 9, so the presence of an object is immediately detected. Can be detected.

The object may be any suitable object as long as it can provide a difference in the level of capacitance, for example a human being.

Therefore, according to the sensor system 30 of this embodiment, the piezoelectric sensor function is realized based on the potential difference between the conductor 3 and the conductor layer 9, and the piezoelectric sensor function is realized based on the capacitance in the conductor layer 9. , a capacitive sensor function is realized and is understood as a dual (or combined) sensor system with two different functions. In such a sensor system 30, there is no need to use a conductor separately from the sensor element 20, and the presence of an object can be detected easily and instantly with a simple system configuration.

The sensor system of this embodiment can be used for a wide variety of purposes. For example, it can be used for seats (including chairs, seats, toilet seats, etc.), beds (including nursing care beds), large touch panels, etc., and uses piezoelectric sensor functions to detect human sitting, body movements, vital signs, touch operations, etc. Moreover, the presence or absence of a human being can be instantly detected by the capacitive sensor function even when a human being is constantly present.

Further, although not essential to the present embodiment, the capacitance detection unit 23 may be configured to be able to detect the proximity of an object based on the capacitance in the conductor layer 9. When an object approaches the sensor element 20 , the electrical environment of the conductor layer 9 changes due to the proximity of the object, causing a change in capacitance in the conductor layer 9 , causing a change in the capacitance detection section 23 . By analyzing this change, it is possible to detect that an object is approaching. Conversely, when an object that was near the sensor element 20 moves away, the electrical environment of the conductive layer 9 changes due to the separation of the object, resulting in a change in capacitance in the conductive layer 9. By analyzing this change with the capacitance detection unit 23, it is possible to detect that the object has moved away.

Although the sensor system according to one embodiment of the present invention has been described above in detail, this embodiment can be modified in various ways.

For example, in the sensor system 30 described above, the conductor layer 9 (electrode extension part B) is electrically connected to the capacitance detection part 23, but as in the sensor system 30' shown in FIG. The body 3 (electrode extension part A) may be electrically connected to the capacitance detection part 23 to detect the presence of an object based on the capacitance in the conductor 3. In this case as well, the same explanation as for the sensor system 30 described above can be applied. However, the capacitance measurement sensitivity is considered to be higher in the sensor system 30 than in the sensor system 30'.

Further, for example, in the sensor systems 30 and 30' described above, the sensor element 20 is used as is, but in both the sensor systems 30 and 30', a sensor in which the sensor element 20 is combined with a fiber or a textile product is used. It may also be used in the form of a device. The sensor element 20 has an elongated linear shape as a whole and can have flexibility as a whole, so it can be used like a so-called "thread". Furthermore, since the electrode extension parts A and B can be taken from one end of the "thread" of the sensor element 20, the other end can be left free, giving an extremely high degree of freedom in usage.

More particularly, the sensor element 20 may be combined with fibers to constitute a textile product selected from the group consisting of strings, ropes, knits, woven fabrics and non-woven fabrics. The fibers combined with the sensor element 20 can be any suitable fibers, including natural fibers (e.g., vegetable fibers such as cotton, linen, animal fibers such as silk), man-made fibers (e.g., viscose rayon, cupro, etc.). synthetic fibers such as nylon, polyester, acrylic, vinylon, polyurethane, and semi-synthetic fibers such as acetate). By using the sensor element 20 like a "thread" and combining it with fibers, it is possible to process it into forms such as strings, ropes, knitted fabrics, woven fabrics, and non-woven fabrics. The string may be constructed, for example, by combining the "threads" of the sensor element 20 with fiber threads (eg, as a braid). The rope may be constructed by, for example, twisting or knitting a "thread" of the sensor element 20 or a "string" including the sensor element 20 with a fiber thread or string. The knitted fabric can be constructed by knitting the "threads" of the sensor element 20 and the fiber threads. The knitting method (knitted structure) is not particularly limited, and may be, for example, weft knitting such as plain knitting, rubber knitting, or purl knitting, or warp knitting such as double denby knitting. The woven fabric can be constructed by using the "thread" of the sensor element 20 as one or more of the warp and weft threads, and using fiber threads as the remaining threads, and weaving these. The weaving method (texture of the textile) is not particularly limited, but may be plain weave, twill weave, satin weave, layered weave, pile weave, or the like. The non-woven fabric may be constructed by using the "threads" of the sensor element 20 and the fiber threads and bonding them together. The bonding method is not particularly limited, but adhesives, molten fibers, or mechanical methods (eg, spunlace, needle punch, dispersion filtration, etc.) can be used. In such a textile product, at least one "thread" of the sensor element 20 may be present, and in some cases, two or more "threads" may be used.

Alternatively, the sensor element 20 may be bonded (or fixed) to a ribbon-like or sheet-like textile product. Here, textile products can be understood by referring to the explanations given above regarding knitted fabrics, woven fabrics and nonwoven fabrics (excluding the explanation regarding sensor elements). A ribbon-shaped textile product refers to a textile product that is thin and elongated, and a sheet-shaped textile product refers to a textile product that is thin and has a two-dimensional spread. Although there is no clear boundary between these, for example, When the aspect ratio is 1:4 or more, it is called "ribbon-like", and when the aspect ratio is less than 1:4, it is called "sheet-like". The joining (or fixing) of the sensor element 20 to the textile product can be carried out in any suitable manner, for example by gluing, sewing, knitting, etc. The bonding method is not particularly limited, but adhesives, molten fibers, etc. can be used. The sewing method may be to use the sensor element 20 like a "thread" and sew it through the textile product in the thickness direction, or if the textile product has a certain thickness, the fiber It may be sewn through the interior of the textile without being exposed on the front and/or back side of the product. The weaving method may use the sensor element 20 like a "thread" to weave into a textile (eg, by intersecting or interlacing with the fibers that make up the textile). The bonding form of the sensor element 20 can be appropriately selected as desired. For example, as shown in FIG. 3A, the sensor device 40 may be a sensor device 40 in which the sensor element 20 is linearly joined to a ribbon-shaped textile product 31. Alternatively, for example, as shown in FIG. 3(b), the sensor device 40' may be a sensor device 40' in which the sensor element 20 is joined to a ribbon-shaped textile product 31 in a wavy (or zigzag) manner. For example, as shown in FIG. 3(c), the sensor device 40'' may be a sensor device 40'' in which the sensor element 20 is spirally joined to a sheet-like textile product 33. As mentioned above, the "thread" of the sensor element 20 can have the electrode extension parts A and B taken from one end, and the other end can be left free, so a configuration like the sensor device 40'' can also be realized. It is possible. (In addition, in FIGS. 3(a) to 3(c), when the sensor element 20 is sewn onto a textile product, it is understood that the solid line indicating the sensor element 20 is shown through the textile product.)

In this way, the sensor device in which the sensor element 20 is combined with fibers or textile products has an elongated linear shape as a whole, and the sensor element as a whole can have flexibility. The entire sensor device including the textile product does not feel like a foreign body or feels strange. Therefore, even if, for example, a human comes into contact with the sensor device including the sensor element 20 (for example, when sitting on a seat or lying down on a bed), sensing can be achieved without feeling a foreign body sensation or discomfort.

A sensor system including a sensor element having the configuration detailed with reference to FIG. 1 was manufactured as follows.

As the resin wire 1, a stranded wire with a diameter of approximately 0.15 mm, which is constructed by twisting 50 strands of para-aramid fibers with a diameter of approximately 15 μm, is used. ) 3 is a laminate in which two foils made of tin-plated copper-tin alloy are laminated, each foil having a width of about 0.17 mm, and a total thickness of the laminate of about 0.012 mm. Core wire 5 was prepared by gap winding something. The outer diameter of the core wire 5 was approximately 0.17 mm, the pitch P was approximately 0.27 mm, and the gap G was approximately 0.08 mm (G/P = approximately 30%).

On the other hand, 33 g of vinylidene fluoride-tetrafluoroethylene copolymer was dissolved in 67 g of methyl ethyl ketone while heating it to 70°C, and the mixture was stirred for 30 minutes using an ultrasonic homogenizer "BRANSON Digital Sonifire" manufactured by Emerson Japan to prepare a resin liquid. did.

The above-prepared resin liquid was coated on the core wire 5 using a dip coating method, heated at 150°C for 2 minutes to vaporize and remove methyl ethyl ketone, and the surface of the core wire 5 was coated with vinylidene fluoride-tetrafluoroethylene. A copolymer layer was formed. This vinylidene fluoride-tetrafluoroethylene copolymer layer was polarized by corona discharging a DC voltage of 12 kV for 30 seconds using a DC high voltage stabilized power supply (manufactured by Element Co., Ltd.) using the core wire 5 as a ground electrode. A piezoelectric layer (organic piezoelectric layer) 7 was obtained. The thickness of the piezoelectric layer 7 was approximately 40 μm.

Next, the piezoelectric layer 7 was covered with a conductive layer 9 by winding a silver-plated copper wire helically (without gaps). The thickness of the conductor layer 9 was approximately 0.03 mm.

Then, the periphery of this conductive layer 9 was covered (tape-wrapped) with a polyester tape to form an insulating layer 11. The thickness of the insulator layer 11 was about 20 μm. The outer diameter of the insulator layer 11 (that is, the outer diameter of the piezoelectric element 20) was approximately 0.35 mm.

The sensor element 20 of this example was produced as described above.

One end of the sensor element 20, which had a length of about 1 m, was processed with a wire stripper to expose the conductor 3 and the conductor layer 9, and the electrode was drawn out. Then, the conductor 3 (electrode extension part A) and the conductor layer 9 (electrode extension part B) are electrically connected to the piezoelectric detection part 21, and the conductor layer 9 (electrode extension part B) is used for capacitance detection. The sensor system 30 was configured by electrically connecting to the section 23. For the piezoelectric detection section 21, an analog amplifier circuit was used. For the capacitance detection section 23, a circuit equipped with a 2MΩ resistor was used.

The sensor element 20 is laid down on the floor, and a person performs an action of "getting on" it and then "getting off (leaving)" it, and the capacitance in the conductor layer 7 at that time is detected by the capacitance detection section. 23, and the potential difference between the conductor 3 of the core wire 3 and the conductor layer 9 was also measured over time. Figure 4 shows the results when a human performs the "get on" motion, and Figure 5 shows the results when the human performs the "get off" motion (the dotted lines in FIGS. 4 and 5 respectively indicate (Indicates when you got on and when you got off).

As understood from FIGS. 4 and 5, the potential difference changed sharply from the time the person got on and off the vehicle, and then attenuated (note that the potential difference is not shown in FIGS. 4 and 5). , it was confirmed that the value returned to the original value before the above operation with the passage of further time). On the other hand, the level of capacitance changes between the time a person gets on and the time a person gets off the vehicle, and thereafter substantially maintains the level after the change without attenuating. From these results, it is possible to detect the external force applied to the sensor element 20 and thus the piezoelectric layer 7 based on the potential difference, and to detect the presence of an object (a human being in this example) based on the capacitance. confirmed. In particular, the capacitance did not attenuate even after the human boarded the vehicle and dismounted, and substantially maintained the level after the change. It is understood that it is possible to immediately determine whether or not the object exists even if the object exists.

The sensor system of the present invention can be used in a wide variety of applications that require both piezoelectric sensor function and capacitive sensor function. The sensor system of the present invention can be used for, for example, seats (including chairs, seats, toilet seats, etc.), beds (including nursing care beds), large touch panels, etc., and uses piezoelectric sensor functions to monitor seating, body movements, and vital signs of humans. It can detect signs, touch operations, etc., and its capacitive sensor function can instantly detect the presence or absence of a human, even if a human is constantly present.

1 Resin wire 3 Conductor (inner conductor layer)
5 core wire 7 piezoelectric layer 9 conductor layer (outer conductor layer)
11 Insulator layer 20 Sensor element 21 Piezoelectric detection section 23 Capacitance detection section 30, 30' Sensor system 31, 33 Textile product 40, 40', 40'' Sensor device A, B Electrode extension GND Ground

Claims (6)

A sensor element including a core wire having a conductive surface, a piezoelectric layer covering the core wire, and a conductive layer covering the piezoelectric layer;
a piezoelectric detection unit that detects an external force applied to the piezoelectric layer based on a potential difference between the conductor and the conductor layer;
A capacitance detection unit that detects the presence of an object based on a change in capacitance in either the conductor or the conductor layer , wherein the change in capacitance is determined by the change in capacitance in either the conductor or the conductor layer. and a capacitance sensing unit whose change is caused by a change in the electrical environment of either one of the conductive layers;
, wherein the conductor layer has an external dimension of 2.2 mm or less. The sensor system according to claim 1, wherein the sensor element further includes an insulator layer covering the conductor layer. 3. Sensor system according to claim 1 or 2, wherein the sensor element is combined with a fiber or textile product. The sensor system according to any one of claims 1 to 3, wherein the sensor element is combined with fibers to constitute a textile product selected from the group consisting of strings, ropes, knitted fabrics, woven fabrics and non-woven fabrics. The sensor system according to any one of claims 1 to 3, wherein the sensor element is bonded to a ribbon-shaped or sheet-shaped textile product. 6. The sensor system according to claim 1, wherein the piezoelectric layer is composed of an organic piezoelectric material or a composite of an organic piezoelectric material and an inorganic piezoelectric material.