JP7508056B1 - Valve Indicator - Google Patents

Abstract

We provide a valve indicator that can accurately detect the opening and closing of a valve without requiring any special operations and without the risk of deformation or damage. The valve indicator comprises a core wire in which at least one layer of metal foil is spirally wound around a resin wire, an organic piezoelectric layer that covers the core wire, and a conductor layer that covers the organic piezoelectric layer, with the metal foil and the conductor layer each functioning as an electrode with the organic piezoelectric layer interposed between them.

Description

The present invention relates to a valve indicator, and more specifically, to a valve indicator consisting of a piezoelectric element.

Piezoelectric elements are elements that use piezoelectric materials and are used in a variety of applications, for example as sensors by utilizing the positive piezoelectric effect of the piezoelectric material (converting an external force applied to the piezoelectric material into a voltage) and as actuators by utilizing the inverse piezoelectric effect of the piezoelectric material (converting a voltage applied to the piezoelectric material into a force).

For example, Patent Document 1 discloses a piezoelectric switch that includes "a plate-shaped piezoelectric element having a plate-shaped piezoelectric body polarized in the thickness direction and a pair of electrodes provided on both main surfaces of the piezoelectric body, and a pair of conductive members fixed to both main surfaces of the piezoelectric element and having elasticity, the piezoelectric element being compressed in a direction parallel to both main surfaces of the piezoelectric element by the pair of conductive members fixed to both main surfaces of the piezoelectric element, and generating electricity by the distortion of the piezoelectric body when an external force is applied, an external force transmission section that transmits the external force to the piezoelectric element and the conductive member of the piezoelectric device and bends them, and a signal generation circuit that extracts the voltage generated by the piezoelectric element that vibrates upon the transmission of the external force from the pair of conductive members and converts it into an electrical signal." However, the piezoelectric switch disclosed in Patent Document 1 has the disadvantage that the surface of the piezoelectric element is easily cracked because the piezoelectric element is compressed in a direction parallel to both main surfaces of the piezoelectric element by the pair of conductive members fixed to both main surfaces of the piezoelectric element, and the piezoelectric body is distorted when an external force is applied.

Patent Document 2 also discloses a piezoelectric switch that includes a piezoelectric element including a reference electrode set to a constant potential, a detection electrode connected to a voltage detection circuit that detects a voltage relative to the constant potential, and a piezoelectric body sandwiched between the reference electrode and the detection electrode, and detects an input operation in which an input operation body presses the piezoelectric element because the voltage detection circuit detects a voltage equal to or greater than a predetermined first threshold value, and further includes a transmitting means for transmitting an AC detection signal in which a part of current flows in the floating capacitance of the input operation body, and a signal detecting means for detecting a reception level of the AC detection signal appearing in the detection electrode, and detects the input operation body approaching the detection electrode from the reception level of the AC detection signal that changes according to the floating capacitance of the input operation body approaching the detection electrode. However, the piezoelectric switch disclosed in Patent Document 2 has the inconvenience that the input operation body must perform an input operation.

Patent No. 3866258 JP 2018-163531 A

The present invention has been made in consideration of the above problems, and aims to provide a valve indicator that does not require special operations, is free from the risk of deformation or damage, and can accurately detect the opening and closing of a valve.

In order to solve the above problems, the valve indicator of the present invention includes 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 layer covering the organic piezoelectric layer, the metal foil and the conductor layer each functioning as an electrode with the organic piezoelectric layer interposed between them, and is characterized in that the opening and closing of the valve is detected by the voltage value generated between the electrodes on both sides of the piezoelectric element due to a change in contact pressure on the piezoelectric element.

In one aspect of the present invention, two or more layers of metal foil may be spirally wrapped around the resin wire.

In one aspect of the present invention, the at least one layer of metal foil may be spirally gap-wound around the resin wire. In this aspect, the ratio of the gap to the spiral pitch of the metal foil may be 0.4 to 50%.

In one aspect of the present invention, the resin wire may be made of at least one material selected from the group consisting of aromatic polyamide, aliphatic polyamide, polyester, polyvinyl alcohol, polyacrylonitrile, polyarylate, polyolefin, polyurethane, and carbon fiber.

In one aspect of the invention, the metal foil may have a thickness of 6 to 100 μm and/or a width of 0.02 to 2 mm.

In one aspect of the present invention, the core wire may have an outer dimension of 0.05 to 1.5 mm.

In one aspect of the present invention, the organic piezoelectric layer may have a thickness of 1 to 200 μm.

In one embodiment of the present invention, the organic piezoelectric layer may contain at least one selected from the group consisting of a copolymer of vinylidene fluoride and trifluoroethylene, and a copolymer of vinylidene fluoride and tetrafluoroethylene.

In one aspect of the present invention, the piezoelectric element may further include an insulating layer covering the conductive layer.

The valve indicator of the present invention includes an organic piezoelectric layer covering a core wire in which at least one layer of metal foil is wound in a spiral shape around a resin wire, and a conductor layer covering the organic piezoelectric layer, and the metal foil and conductor layer are piezoelectric elements that function as electrodes with the organic piezoelectric layer interposed between them, so that the valve indicator can have an elongated linear shape as a whole. The valve indicator of the present invention uses a core wire in which at least one layer of metal foil is wound in a spiral shape around a resin wire, so that even if it is bent with a small radius of curvature, distortion is unlikely to remain in the core wire, and therefore the valve indicator has excellent flexibility, and even if it is repeatedly bent, the core wire is unlikely to break and electrical continuity is unlikely to be cut off, so that the valve indicator has excellent bending resistance.

FIG. 1 is a schematic diagram showing a piezoelectric element in one embodiment of the present invention, in which FIG. 1(a) shows a partially cut-away side view of the piezoelectric element, FIG. 1(b) shows a cross-sectional view taken along line A-A in FIG. 1(a), and FIG. 1(c) shows a modified example of FIG. 1(b). FIG. 2 is a schematic diagram showing a core wire that can be used in a piezoelectric element in one embodiment of the present invention, where FIG. 2(a) shows a side view of the core wire, FIG. 2(b) shows a cross-sectional view along line B-B in FIG. 2(a), and FIG. 2(c) shows a modified example of FIG. 2(b). FIG. 3 is an overall schematic diagram of a first embodiment of a valve opening/closing detection system capable of detecting the opening and closing of a valve by a valve indicator made of a piezoelectric element. FIG. 4 is a schematic configuration diagram including a vertical cross section of a flow control valve that can be used in the first embodiment of the valve opening/closing detection system shown in FIG. FIG. 5 is an overall schematic diagram of a second embodiment of a valve opening/closing detection system capable of detecting the opening and closing of a valve by a valve indicator made of a piezoelectric element. FIG. 6 is an overall schematic diagram of a third embodiment of a valve opening/closing detection system capable of detecting the opening and closing of a valve by a valve indicator made of a piezoelectric element. FIG. 7 is an overall schematic diagram of a fourth embodiment of a valve opening/closing detection system capable of detecting the opening and closing of a valve by a valve indicator made of a piezoelectric element. FIG. 8 is an overall schematic diagram of a fifth embodiment of a valve opening/closing detection system capable of detecting the opening and closing of a valve by a valve indicator made of a piezoelectric element.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the attached drawings, electrode terminals are shown diagrammatically as black circles.

With reference to FIG. 1, the piezoelectric element 20 of this embodiment has a core wire 5 in which at least one layer of metal foil 3 is spirally wound around a resin wire 1, an organic piezoelectric layer 7 covering the core wire 5, a conductor layer 9 covering the organic piezoelectric layer 7, and, in some cases, an insulator layer 11 covering the conductor layer 9. In the piezoelectric element 20, the metal foil 3 and the conductor layer 9 each function as an electrode with the organic piezoelectric layer 7 interposed therebetween (see FIG. 1(b)). Such a piezoelectric element 20 has an elongated linear shape as a whole, which may be called a cable-like or wire-like shape, and is configured to have flexibility as a whole piezoelectric element. In the piezoelectric element 20, the core wire 5, the organic piezoelectric layer 7, the conductor layer 9, and, if present, the insulator layer 11 may be arranged approximately coaxially, but the present invention is not limited to such a configuration.

The piezoelectric element 20 of this embodiment can be manufactured as follows.

As shown in FIG. 2, the core wire 5 usable in this embodiment may have a configuration in which at least one layer of metal foil 3 is wound in a spiral shape around the resin wire 1. By having such a configuration, when the core wire 5 is pulled, the tensile stress acts mainly on the resin wire 1, and the entire core wire 5 can be stretched, and preferably exhibits a tensile elongation of 3% or more. Even when bent with a relatively small radius of curvature (for example, when subjected to a flexibility test described later), no distortion remains in the core wire 5, and the core wire 5 exhibits excellent flexibility. In addition, by having such a configuration, the core wire 5 is unlikely to lose conductivity even when repeatedly bent (for example, it can maintain conductivity even when repeatedly bent 5,000 times or more in a bending resistance test described later), and exhibits excellent bending resistance. Therefore, the piezoelectric element 20 of this embodiment using such a core wire 5 can achieve the effect of excellent flexibility and bending resistance.

The resin wire 1 may be a generally linear member made of a resin material. Examples of such resin materials include at least one material selected from the group consisting of aromatic polyamides (aramids, such as para-aramids and meta-aramids), aliphatic polyamides (nylons), polyesters, polyvinyl alcohols, polyacrylonitriles, polyarylates, polyolefins, polyurethanes, and carbon fibers (such as carbon nanotubes (CNTs)).

The resin wire 1 may have any cross-sectional shape, such as a circle, an ellipse, a rectangle, a polygon, etc., may be either hollow or solid, and may be a single wire, a twisted wire, a braided wire, etc. The outer dimension D ₁ of the resin wire 1 (the maximum outer dimension of the cross section when the resin wire 1 has a noncircular cross section, and the outer diameter when the resin wire 1 has a circular cross section; the same applies below) is not particularly limited, and may be appropriately selected in consideration of the outer dimension desired for the core wire 5 and the thickness of the metal foil 3 wrapped around the resin wire 1 (the total thickness of the metal foil in the case of two or more layers of metal foil). The outer dimension D ₁ of the resin wire 1 may be, for example, 0.05 to 2 mm, particularly 1 mm or less, more particularly 0.5 mm or less.

The metal foil 3 may be a foil-like (or layer-like) member made of a metal material. Any suitable metal material that exhibits high conductivity suitable for functioning as an electrode (and therefore contributes to the piezoelectric element as a whole exhibiting a low resistance value) may be used as the metal material, and a single metal material may be used, or multiple metal materials may be used (for example, a base material of a certain metal material may be plated with another metal material). Preferred examples of such metal materials include copper and copper-containing alloys (for example, copper-tin alloys, copper-silver alloys, etc.), which may or may not be plated with tin, for example. These materials exhibit high conductivity, and because copper exhibits high ductility, they have excellent mechanical strength, which can further increase the flexibility and bending resistance of the piezoelectric element 20.

The metal foil 3 may be a single layer of metal foil or two or more layers of metal foil superimposed (i.e., a laminate of two or more layers of metal foil). In the latter case, two or more layers of metal foil are spirally wound around the resin wire 1. For example, as shown in FIG. 2(c), metal foil 3a and metal foil 3b may be superimposed and spirally wound around the resin wire 1. The two adjacent layers of metal foil may at least partially overlap (see FIG. 2(c)), for example, by 20% or more, particularly 40% or more, of the width of the metal foil.

When a laminate of two or more metal foil layers is used as the metal foil 3, even if one of the two or more metal foil layers breaks due to repeated bending, for example, it is possible to avoid interruption of electrical continuity in the entire metal foil laminate, and therefore it is possible to more effectively prevent failure of the piezoelectric element 20. The number of layers of the metal foil may be, for example, 2 to 4 layers, particularly 3 layers or less, and more particularly 2 layers.

The thickness and width of the metal foil 3 can be appropriately selected in consideration of the desired outer dimensions, flexibility, and bending resistance of the core wire 5. The ratio of the thickness of the metal foil 3 to the outer dimension D ₁ of the resin wire 1 can be, for example, 0.4 to 100%, and the thickness of the metal foil 3 can be, for example, 6 to 100 μm, particularly 30 μm or less, more particularly 15 μm or less. The width of the metal foil 3 can be, for example, 0.02 to 2 mm, particularly 1 mm or less, more particularly 0.5 mm or less. The thickness of the metal foil 3 refers to the thickness of one layer of metal foil when one layer is used, and refers to the total thickness of two or more layers of metal foil when two or more layers of metal foil are used in a superimposed manner. The width of the metal foil 3 refers to the dimension in a direction perpendicular to the center line along the longitudinal direction of the metal foil 3 that can be spirally wrapped around the resin wire 1 (or the shortest distance between both sides along the longitudinal direction of the metal foil 3). When two or more layers of metal foil are used in a superimposed manner, the thickness and width of each metal foil may be the same or different from each other, but typically will be the same.

In the core wire 5, at least one layer of metal foil 3 is wound around the resin wire 1 in a spiral shape, preferably with a constant spiral pitch P, and is not overlapped. The dimension of the spiral pitch P is not particularly limited as long as it is larger than the width of the metal foil 3. In a state where no stress is applied to the core wire 5 (or the piezoelectric element 20), the ratio of the spiral pitch P to the outer dimension D1 of the resin wire ₁ can be, for example, 2 to 4700%, particularly 100 to 500%, and within this range, the flexibility and bending resistance of the core wire 5 and therefore the piezoelectric element 20 can be further improved. The spiral pitch P can be, for example, 0.03 mm to 2.35 mm, particularly 0.05 to 0.6 mm.

In the core wire 5, it is preferable that at least one layer of metal foil 3 is wound around the resin wire 1 in a spiral gap. "Gap winding" is also called interval winding, and means that when the metal foil 3 is wound around the resin wire 1 in a spiral shape, a gap G (see FIG. 2(a)) is provided in the metal foil 3 and the metal foil 3 is wound around the resin wire 1 as shown in FIGS. 1 and 2. The gap G corresponds to the exposed portion of the resin wire 1, and the size of the gap G can be measured based on the exposed portion of the resin wire 1 (especially when two or more layers of metal foil are used in a superimposed manner and are misaligned with each other). In a state where no stress is applied to the core wire 5 (or the piezoelectric element 20), the ratio of the gap G to the spiral pitch P can be, for example, 0.4 to 50%, particularly 5 to 40%, and in this range, the flexibility and bending resistance of the core wire 5 and therefore the piezoelectric element 20 can be further increased. The gap G can be, for example, 0.01 to 0.35 mm, particularly 0.1 mm or less.

The outer dimension D ₂ of the core wire 5 (the maximum outer dimension of the cross section when it has a non-circular cross section as shown in FIG. 2(b) and the outer diameter when it has a circular cross section, the same applies below) is not particularly limited and can vary depending on the specifications required for the piezoelectric element 20. The core wire 5 can be made extremely thin, and the outer diameter dimension D ₂ can be, for example, 0.05 to 1.5 mm, particularly 1.0 mm or less, more particularly 0.5 mm or less, and even more particularly 0.3 mm or less.

Referring again to FIG. 1, the core wire 5 is coated with an organic piezoelectric layer 7. The organic piezoelectric layer 7 is provided between the metal foil 3 and the conductor layer 9 of the core wire 5 so that they do not come into contact with each other, and is preferably provided in close contact with the metal foil 3.

The organic piezoelectric layer 7 may be made of any material known as an organic piezoelectric. The organic piezoelectric has higher impact resistance and bending resistance than inorganic piezoelectrics such as piezoelectric ceramics such as lead zirconate titanate (PZT). The material forming the organic piezoelectric layer 7 may be, for example, polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers (including copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)), and copolymers of vinylidene fluoride and tetrafluoroethylene (P(VDF/TeFE))). Of these, it is preferable that the organic piezoelectric layer 7 contains at least one selected from the group consisting of P(VDF/TrFE) and P(VDF/TeFE).

The thickness of the organic piezoelectric layer 7 is not particularly limited and can be appropriately selected in consideration of the piezoelectric characteristics (positive piezoelectric effect and/or reverse piezoelectric effect), flexibility, bending resistance, etc. desired for the piezoelectric element 20. The thickness of the organic piezoelectric layer 7 can be, for example, 1 to 200 μm, particularly 100 μm or less, more particularly 50 μm or less.

Depending on the actual material used, the material constituting the organic piezoelectric layer 7 may be subjected to any suitable process required to exhibit piezoelectricity, such as stretching and/or polarization, before coating the core wire 5, during the coating formation, or thereafter.

For example, when PVDF (polyvinylidene fluoride) is used as the material for the organic piezoelectric layer 7, the organic piezoelectric layer 7 can be formed as follows. PVDF can have three types of crystal structures, α, β, and γ, and is usually the most energetically stable α type. However, PVDF containing a large amount of α type crystal structures can be converted to PVDF containing a large amount of β type crystal structures by, for example, uniaxial stretching. PVDF containing a large amount of β type crystal structures exhibits ferroelectricity, and by subjecting it to a polarization treatment, the dipoles are aligned and it exhibits piezoelectricity. Therefore, a PVDF film obtained by uniaxially stretching a PVDF film is wound (preferably overlapped) around the core wire 5 without any gaps, and then subjected to a polarization treatment such as corona discharge, thereby obtaining a PVDF layer exhibiting piezoelectricity, and as a result, the core wire 5 can be covered with an organic piezoelectric layer (more specifically, a PVDF layer) 7.

For example, when a vinylidene fluoride copolymer is used as the material for the organic piezoelectric layer 7, the organic piezoelectric layer 7 can be formed as follows. Vinylidene fluoride copolymers, particularly P(VDF/TrFE) and P(VDF/TeFE), can contain more β-type crystal structures than PVDF. Therefore, such vinylidene fluoride copolymers can easily produce a winding 7 in which the core wire 5 is covered with an organic piezoelectric layer 7 by simply applying a polarization treatment without stretching. Specifically, the organic piezoelectric layer 7 can be formed by the following solvent coating method or melt extrusion method.

In the solvent coating method, a resin liquid is first prepared by dissolving or dispersing a vinylidene fluoride copolymer in a solvent, and the resin liquid is applied (e.g., coated) to the surface of the core wire 5, and then heated to substantially remove the solvent to obtain a vinylidene fluoride copolymer layer. The vinylidene fluoride copolymer layer exhibiting piezoelectricity is then obtained by subjecting the layer to a polarization treatment such as corona discharge, and as a result, the core wire 5 can be coated with an organic piezoelectric layer (more specifically, a vinylidene fluoride copolymer layer) 7. Examples of the solvent that can be used include ketone-based solvents (e.g., methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone), ester-based solvents (e.g., ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate), ether-based solvents (e.g., tetrahydrofuran, methyltetrahydrofuran, dioxane), amide-based solvents (e.g., dimethylformamide (DMF), dimethylacetamide), and pyrrolidone-based solvents (e.g., N-methylpyrrolidone). The heating temperature may vary depending on the solvent used, but may be, for example, 80 to 180°C.

In the melt extrusion method, for example, a vinylidene fluoride copolymer in pellet form is first heated and melted to obtain a molten resin. The heating temperature may be equal to or higher than the melting point of the vinylidene fluoride copolymer used, and may be, for example, 120 to 250°C. This molten resin is applied to the surface of the core wire 5 (for example, extrusion coating around it) to obtain a vinylidene fluoride copolymer layer, which is then subjected to a polarization treatment such as corona discharge to obtain a vinylidene fluoride copolymer layer exhibiting piezoelectricity. As a result, the core wire 5 can be coated with an organic piezoelectric layer (more specifically, a vinylidene fluoride copolymer layer) 7.

The organic piezoelectric layer 7 using PVDF and/or vinylidene fluoride copolymer is preferable because it exhibits high heat resistance, for example, at 85°C or higher. The molecular weight of PVDF and vinylidene fluoride copolymer is not particularly limited. The vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and one or more fluorine-based monomers copolymerizable with vinylidene fluoride (hereinafter, simply referred to as other fluorine-based monomers). The other fluorine-based monomers may be one or both of trifluoroethylene and tetrafluoroethylene. In the vinylidene fluoride copolymer, the unit derived from vinylidene fluoride may be 50 mol% or more, preferably 60 mol% or more, and the molar ratio of the unit derived from the other fluorine-based monomer and the unit derived from vinylidene fluoride may be appropriately selected.

However, the material constituting the organic piezoelectric layer 7 is not limited to the materials detailed above, and may further contain any other suitable components (e.g. additives such as piezoelectric ceramics) in, for example, relatively small amounts, or other known organic materials exhibiting piezoelectricity may be used.

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

The conductive layer 9 may be a flexible member made of a material whose surface in contact with the organic piezoelectric layer 7 is conductive. The conductive layer 9 may be a conductive layer known as a shield, for example, a braided shield of metal wires and a horizontally wound shield. The conductive layer 9 may also be at least one layer of metal foil wound in a spiral shape around the organic piezoelectric layer 7. In this case, at least one layer of metal foil 9' is wound in a spiral shape around the organic piezoelectric layer 7, preferably with a constant spiral pitch P, and may or may not be overlapped, and may further be gap wound, for example, as shown in FIG. 1(c). When two or more layers of metal foil are used in a superimposed manner, the two adjacent layers of metal foil may at least partially overlap each other, for example, by 20% or more, particularly 40% or more of the width of the metal foil. Preferred examples of the metal material constituting the metal wire or metal foil include copper and copper-containing alloys (for example, copper-tin alloys, copper-silver alloys, etc.), which may or may not have plating, for example, tin. These materials have high electrical conductivity, and because copper has high ductility, they have excellent mechanical strength, which can further increase the flexibility and bending resistance of the piezoelectric element 20 .

The thickness of the conductive layer 9 is not particularly limited and may be appropriately selected taking into consideration the flexibility and bending resistance desired for the piezoelectric element 20. The thickness of the conductive layer 9 may be, for example, 5 to 500 μm, particularly 200 μm or less, more particularly 100 μm or less.

The outer dimensions of the conductive layer 9 may correspond to the outer dimensions of the piezoelectric element 20 when the piezoelectric element 20 does not have the insulating layer 11, and may be, for example, 0.05 to 2.2 mm, particularly 1.5 mm or less, and more particularly 1 mm or less, without being particularly limited thereto.

Furthermore, although not essential to this embodiment, the conductive layer 9 may be covered with an insulating layer 11. The insulating layer 11 may be provided to electrically and/or physically protect the piezoelectric element 20. Such an insulating layer 11 may also be understood as a sheath (or jacket).

The insulator layer 11 may be a flexible member made of a material that exhibits insulating properties at least on the surface. The insulator layer 11 may be, for example, a braid of insulating wires (wires made of insulating materials such as nylon, polyester, acrylic, polyolefin, rubber, silicone, urethane, polyarylate, aromatic polyamide, aliphatic polyamide, etc.). The insulator layer 11 may also be formed by extrusion coating the periphery of the conductor layer 9 with an insulating material (for example, polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer (EVA), polyolefin, fluororesin (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), PVDF, etc.), rubber, etc.).

The thickness of the insulator layer 11 is not particularly limited and may be appropriately selected taking into consideration the flexibility and bending resistance desired for the piezoelectric element 20. The thickness of the insulator layer 11 may be, for example, 10 to 1000 μm, particularly 700 μm or less, more particularly 400 μm or less.

The outer dimensions of the insulator layer 11 may correspond to the outer dimensions of the piezoelectric element 20 when the piezoelectric element 20 has the insulator layer 11, and may be, for example, 0.07 to 4.2 mm, particularly 1.5 mm or less, and more particularly 1 mm or less, without being particularly limited thereto.

An air layer may be present at least partially between the conductor layer 9 and the insulator layer 11. In this case, the insulator layer 11 can be easily removed with a wire stripper or the like to expose the conductor layer 9 and to extract the electrode terminal.

In this manner, the piezoelectric element 20 of this embodiment can be obtained. The piezoelectric element 20 of this embodiment has excellent flexibility and bending resistance. The metal foil 3 and the conductive layer 9 function as electrodes (electrode terminals are shown diagrammatically as black circles in the attached drawings). The conductive layer 9 may be a ground, in which case it may also function as a shield.

The above describes in detail one embodiment of the piezoelectric element of the present invention, but various modifications of this embodiment are possible.

Example 1
A piezoelectric element having the configuration described in detail with reference to FIGS. 1 and 2 in the first embodiment was fabricated as follows.

A stranded wire with a diameter of about 0.15 mm, consisting of 50 strands of para-aramid fiber with a diameter of about 15 μm, was used as the resin wire 1, and a laminate of two layers of tin-plated copper-tin alloy foil as the metal foil 3, each foil having a width of about 0.17 mm and a total thickness of about 0.012 mm, was gap-wound around this resin wire 1 to prepare the core wire 5. The outer diameter of the core wire 5 was about 0.17 mm, the pitch P was about 0.27 mm, and the gap G was about 0.08 mm (G/P = about 30%).

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

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

Next, the organic piezoelectric layer 7 was covered with a single layer of tin-plated tin-copper alloy foil wound in a spiral shape (without gaps) as a conductor layer 9. The thickness of the conductor layer 9 was approximately 0.012 mm.

The conductive layer 9 was then extrusion-coated with low-density polyethylene to form the insulating layer 11. The thickness of the insulating layer 11 was approximately 200 μm. The outer diameter of the insulating layer 11 (i.e., the outer diameter of the piezoelectric element 20) was approximately 0.67 mm.

The piezoelectric element 20 of this embodiment was manufactured in the manner described above.

Example 2
A stranded wire having a diameter of about 0.14 mm, which was made by stranding 50 strands of para-aramid fiber having a diameter of about 14 μm, was used as the resin wire 1, and a laminate of two layers of foil made of a copper-silver alloy, each foil having a width of about 0.17 mm and a total thickness of the laminate of about 0.012 mm, was gap-wound around this resin wire 1 to prepare a core wire 5. The outer diameter of the core wire 5 was about 0.16 mm, the pitch P was about 0.34 mm, and the gap G was about 0.04 mm (G/P=about 12%).

A piezoelectric element was prepared in the same manner as in Example 1, except that the core wire prepared above was used.

Example 3
A stranded wire with a diameter of about 0.15 mm, consisting of 50 strands of polyester wires with a diameter of about 15 μm, was used as the resin wire 1, and a single layer of metal foil 3 made of a copper-tin alloy with a width of about 0.27 mm and a thickness of about 0.019 mm was gap-wound around the resin wire 1 to prepare a core wire 5. The outer diameter of the core wire 5 was about 0.19 mm, the pitch P was about 0.23 mm, and the gap G was about 0.02 mm (G/P=about 9%).

A piezoelectric element was prepared in the same manner as in Example 1, except that the core wire prepared above was used.

(Comparative Example 1)
A piezoelectric element was fabricated in the same manner as in Example 1, except that a nylon thread with a silver-plated surface (outer diameter: approximately 0.11 mm, manufactured by Mitsufuji Corporation, product name: AGposs (registered trademark) silver-plated fiber (filament), 70d/34f, where d is denier and f is the number of filaments) was used as the core wire.

(Comparative Example 2)
A piezoelectric element was fabricated in the same manner as in Example 1, except that a nylon thread with a silver-plated surface (outer diameter: approximately 0.16 mm, manufactured by Mitsufuji Corporation, product name: AGposs (registered trademark) silver-plated fiber (filament), 100d/34f) was used as the core wire.

(Comparative Example 3)
A piezoelectric element was produced in the same manner as in Example 1, except that a single high-tensile piano wire with a brass-plated surface (outer diameter: approximately 0.05 mm, manufactured by Nippon Steel & Sumikin SG Wire Corporation, product name: SPWH) was used as the core wire.

(Comparative Example 4)
A piezoelectric element was fabricated in the same manner as in Example 1, except that a twisted wire (outer diameter: approximately 0.075 mm) made by twisting together seven strands of a copper-tin alloy with a silver-plated surface was used as the core wire.

(Comparative Example 5)
A piezoelectric element was produced in the same manner as in Example 1, except that a single wire (outer diameter: about 0.06 mm) of SUS316 (JIS G4309) was used as the core wire.

(Measurement and Evaluation)
The piezoelectric elements produced in Examples 1 to 3 and Comparative Examples 1 to 5 were evaluated by measuring the resistance and tensile elongation and also by subjecting them to a flexibility test and a bending resistance test, as described below. The results are shown in Table 1.

Resistance measurement The metal foil (Example) or metal portion (Comparative Example) of the core wire and the conductive layer are exposed from the piezoelectric element to form electrodes, and a voltage is applied between these electrodes using a tester (Digital Multimeter CDM-11D, manufactured by Custom Co., Ltd.) to measure the resistance. For practical use as a piezoelectric element, the resistance is preferably low, specifically, 50 Ω/m or less is preferable, and 20 Ω/m or less is more preferable.

Tensile elongation measurement: Using a tensile tester (Shimadzu Corporation, model number: AGS-H), in accordance with JIS Z2241, a piezoelectric element cut to a length of about 100 mm is gripped at both longitudinal ends with grippers and pulled at 10 mm/min to measure the length of the piezoelectric element at break, and the ratio (%) of the elongation of the piezoelectric element at break to the length of the piezoelectric element before the test is determined (tensile elongation is synonymous with breaking elongation). In order to contribute to the flexibility of the piezoelectric element, the greater the tensile elongation, the more preferable, and specifically, 3% or more is preferable.

Flexibility test: A long piezoelectric element is bent in a cross shape into a ring with an inner diameter of 10 mm, and both ends of the piezoelectric element in the longitudinal direction are pulled in opposite directions so that the ring shrinks while maintaining the crossing as much as possible so that the ring does not come undone. After that, the piezoelectric element (more specifically, the core wire) is visually observed to determine whether or not there is residual distortion. For a piezoelectric element to be practically usable, it is preferable that there is no residual distortion.

- Bending resistance test Using a durability tester (manufactured by Yuasa System Co., Ltd., model number: DMLHB-P150), the piezoelectric element was repeatedly bent at ±90° with a load of 100 g and a speed of 60 rpm, and the number of times until the electrical continuity between the electrodes of the piezoelectric element was broken was measured. For a piezoelectric element to be practically usable, it is preferable that the element can maintain electrical continuity even after being repeatedly bent 5,000 times or more, and more preferably, can maintain electrical continuity even after being repeatedly bent 10,000 times or more.

As can be seen from Table 1, the piezoelectric elements of Examples 1 to 3 showed low resistance values of 50 Ω/m or less, tensile elongation of 3% or more, and excellent flexibility with no residual distortion even when subjected to a flexibility test. This is believed to be because the bending stress mainly acted on the resin wire of the core wire and did not directly act on the metal foil, so that even if deformation occurred, the resin wire was elastically deformed and the element was able to return to its original state. In addition, the piezoelectric elements of Examples 1 to 3 were able to maintain conduction even after being repeatedly bent 5,000 times or more in the bending resistance test, demonstrating excellent bending resistance. In particular, the piezoelectric elements of Examples 1 and 2 were able to maintain conduction even after being repeatedly bent 15,000 times or more in the bending resistance test, demonstrating extremely excellent bending resistance. This is believed to be because a laminate of two or more layers of metal foil was used for the core wire, so that even if one of the two layers of metal foil broke due to repeated bending, it was possible to avoid disconnection of conduction in the entire metal foil laminate. On the other hand, the piezoelectric elements of Comparative Examples 1 and 2 had high resistance values and were not suitable for practical use. The piezoelectric elements of Comparative Examples 3 to 5 had a tensile elongation of less than 3%, and residual distortion was observed in the core wire in the flexibility test. It is believed that residual distortion was observed because bending stress acted directly on the metal part of the core wire, causing plastic deformation of the metal, which made it impossible to return to its original state. Furthermore, in the bending resistance test, the piezoelectric elements of Comparative Examples 3 to 5 lost electrical continuity after being repeatedly bent less than 5,000 times. It is believed that this was observed because bending stress acted directly on the metal part of the core wire, which easily broke due to the accumulation of plastic deformation of the metal.

The following describes an embodiment of a valve opening/closing detection system that can detect the opening and closing of a valve using a valve indicator consisting of a piezoelectric element configured as described above.

First embodiment
As shown in the overall schematic diagram of Fig. 3, the valve opening/closing detection system 21 of the first embodiment includes a flow path 22 through which a fluid flows, a pressure sensor 23 for detecting the pressure of the fluid flowing in the flow path 22, a temperature sensor 24 for detecting the temperature of the fluid flowing in the flow path 22, a flow meter 25 for measuring the flow rate of the fluid flowing in the flow path 22, a flow control valve 26 for controlling the flow rate of the fluid flowing in the flow path 22, a valve indicator 27 made of a piezoelectric element capable of detecting the opening/closing of the flow control valve 26, and a controller 28 having the function of controlling, monitoring, and calculating the operation of the pressure sensor 23, the temperature sensor 24, the flow meter 25, and the flow control valve 26. 29 denotes a silicon wafer used in the manufacture of semiconductors. The flow control valve 26 is connected to the controller 28 by a wire 26a, and the valve indicator 27 is connected to the controller 28 by a wire 27a. The pure water or chemical liquid for etching process flowing through the flow path 22 of the valve open/close detection system 21 shown in FIG. 3 is controlled to an appropriate flow rate by the flow control valve 26 and then sprayed onto the silicon wafer 29 .

In semiconductor manufacturing, extremely high cleanliness is required for fluids such as pure water for cleaning silicon wafers and chemicals for etching. Specifically, large-scale integration and fine processing in semiconductor manufacturing have progressed, and the International Technology Roadmap for Semiconductors (ITRS) has determined that the process will be 32 nm in 2015. The number represented by the process (32 nm) is defined as half the pitch (line width + line spacing) of the narrowest wiring on the bottom layer of the MPU. With the wiring width being determined in this way, the inclusion of dirt or fine debris (particles) in the fluid flow path during the semiconductor manufacturing process has a significant impact on product yield. Since particles must be less than one-quarter of the wiring pitch (8 nm for the 2015 process), materials that allow the fluid to flow while maintaining its cleanliness are of great importance.

Therefore, when fluids such as pure water for cleaning silicon wafers used in semiconductor manufacturing or chemicals for etching flow through the flow path 22, the flow path 22 as well as the pressure sensor 23, temperature sensor 24, flow meter 25, flow control valve 26 and valve indicator 27 must be made of chemical-resistant materials (materials that can withstand corrosion by corrosive chemicals) that can withstand the corrosion of the pure water and chemicals. For example, fluororesins such as PFA (perfluoroalkoxyalkane) and PTFE (polytetrafluoroethylene), which have excellent resistance to acids, alkalis and organic solvents, are preferred as chemical-resistant materials.

Figure 4 is a schematic diagram including a vertical cross section of a flow control valve that can be used in one embodiment of the valve opening/closing detection system shown in Figure 3. In Figure 4, 31 is a diaphragm, 32 is a valve block, 33 is a piezoelectric actuator, and 34 is an input/output end of the piezoelectric actuator 33. This input/output end 34 is connected to the diaphragm 31. When the diaphragm 31 expands and contracts due to a minute pressure received from the input/output end 34 of the piezoelectric actuator 33, the fluid that flows into one of the flow paths (indicated by an arrow to the right in Figure 4) formed in the upstream part 32a of the valve block 32 can be discharged from the flow path (indicated by an arrow to the right in Figure 4) formed in the upstream part 32a of the valve block 32 through the gap between the inner surface of the valve block 32 and the inner surface of the diaphragm 31, and from the flow path (indicated by an arrow to the right in Figure 4) formed in the downstream part 32b of the valve block 32.

In Figure 4, the peripheral portion of the diaphragm 31 and the upper end face of the valve block 32 are welded together (see the area surrounded by the small circle indicated by C in Figure 4), and there are no steps or gaps between the inner surfaces of the diaphragm 31 and the valve block 32 at the welded portion, and the inner surfaces of the diaphragm 31 and the valve block 32 are flush, so that no foreign matter is generated at the welded portion, and no foreign matter accumulates or remains at the welded portion, thereby maintaining a high level of cleanliness of the controlled fluid.

Next, the operation of the flow control valve shown in Figure 4 will be explained.

(1) Initial Purge Before flow rate control is started, all the flow paths including the flow path shown in FIG. 4 are cleaned by flowing pure water through them.
(2) Flow Control Fig. 4 shows flow control in the case of a normally closed type. An electrode (not shown) is connected to the piezoelectric actuator 33 shown in Fig. 4, and a voltage is applied to the electrode to generate an electric field inside the piezoelectric actuator 33, which causes the input/output end 34 of the piezoelectric actuator 33 to be slightly pulled toward the piezoelectric actuator 33, and a minute gap is generated between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream portion 32b of the valve block 32 via the input/output end 34, so that the fluid flows from the upstream portion 32a of the valve block 32 to the downstream portion 32b of the valve block 32. That is, in Fig. 4 showing the case of a normally closed type, the input/output end 34 is slightly pulled toward the piezoelectric actuator 33, which causes a minute gap to be generated between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream portion 32b of the valve block 32. In addition, a spring is inserted in the piezoelectric actuator 33 to expand the input/output end 34 outward from the piezoelectric actuator 33, so that in order to retract the input/output end 34 toward the piezoelectric actuator 33, it is necessary to overcome this spring force. Therefore, the flow rate of the fluid flowing through the minute gap can be adjusted by increasing or decreasing the electric field strength generated inside the piezoelectric actuator 33. If the electric field strength generated inside the piezoelectric actuator 33 becomes smaller than the spring force, the input/output end 34 tries to return to its original position, so that no minute gap is formed between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream portion 32b of the valve block 32, and the flow path of the fluid is closed, so that the fluid does not flow from the upstream portion 32a of the valve block 32 to the downstream portion 32b of the valve block 32.

In the case of the normally open type, the flow control can be performed as follows. In the case of the normally open type, in FIG. 4, there is a minute gap between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream part 32b of the valve block 32. Therefore, an electrode (not shown) is connected to the piezoelectric actuator 33 shown in FIG. 4, and a voltage is applied to the electrode to generate an electric field inside the piezoelectric actuator 33, which causes the input/output end 34 of the piezoelectric actuator 33 to expand, and the minute gap between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream part 32b of the valve block 32 is closed through the input/output end 34 (as shown in FIG. 4), so that no fluid flows from the upstream part 32a of the valve block 32 to the downstream part 32b of the valve block 32. In addition, a spring is inserted in the piezoelectric actuator 33 to pull the input/output end 34 back toward the piezoelectric actuator 33, so that in order for the input/output end 34 to expand, it is necessary to overcome this spring force. Therefore, when the electric field strength generated inside the piezoelectric actuator 33 becomes smaller than this spring force, the input/output end 34 tries to return to its original position, creating a minute gap between the diaphragm 31 and the protrusion 32c inside the valve block 32 and between the diaphragm 31 and the downstream portion 32b of the valve block 32, and the fluid flows from the upstream portion 32a of the valve block 32 to the downstream portion 32b of the valve block 32. Therefore, by increasing or decreasing the electric field strength generated inside the piezoelectric actuator 33, the flow rate of the fluid flowing through the minute gap can be adjusted.

In Figure 4, 35 is a protrusion that moves up and down due to the opening and closing of the flow control valve accompanying the expansion and contraction of diaphragm 31, as explained in paragraphs 0082 and 0083. When the flow control valve shown in Figure 4 is used as flow control valve 26 in Figure 3, when flow control valve 26 is closed, protrusion 35 does not contact valve indicator 27, and when flow control valve 26 is open, protrusion 35 contacts valve indicator 27. In this way, the opening and closing of the valve can be detected by the voltage value generated between the electrodes on both sides of the piezoelectric element due to changes in contact pressure on the piezoelectric element.

In order to detect the opening and closing of the valve based on the voltage value generated between the electrodes on both sides of the piezoelectric element, the controller 28 has a calculation function that sets a threshold value for the voltage value, and determines that the valve is open when the voltage value generated between the electrodes on both sides of the piezoelectric element exceeds the threshold value, and determines that the valve is closed when the voltage value generated between the electrodes on both sides of the piezoelectric element does not exceed the threshold value.

As explained in paragraphs 0082 and 0083, the operation of the open/close detection system shown in FIG. 3 when the flow control valve 26 is opened and closed will be described. In FIG. 4 showing flow control in the case of a normally closed type, if the electric field strength generated inside the piezo actuator 33 is smaller than the above-mentioned spring force without flowing fluid to the upstream part 32a of the valve block 32, the input/output end 34 will try to return to its original position, so that no minute gap is formed between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream part 32b of the valve block 32, the flow path of the fluid is closed, and the fluid does not flow from the upstream part 32a of the valve block 32 to the downstream part 32b of the valve block 32. At this time, the protrusion 35 of the flow control valve shown in FIG. 4 does not contact the valve indicator 27, and the voltage value calculated by the controller 28 is 0 mV, which is below the threshold value of 30 mV.

Next, when 300 ml/min of liquid was flowed into the upstream portion 32a of the valve block 32, the electric field strength generated inside the piezoelectric actuator 33 became greater than the spring force, slightly pulling the input/output end 34 of the piezoelectric actuator 33 toward the piezoelectric actuator 33, and a minute gap was generated between the diaphragm 31 and the protrusion 32c inside the valve block 32 and the downstream portion 32b of the valve block 32 via the input/output end 34, and the fluid flowed from the upstream portion 32a of the valve block 32 to the downstream portion 32b of the valve block 32. At this time, the protrusion 35 of the flow control valve shown in FIG. 4 contacted the valve indicator 27, and the voltage value calculated by the controller 28 was 170 mV, exceeding the threshold value of 30 mV.

Since the present invention aims to provide a valve indicator that can accurately detect the opening and closing of a valve without requiring special operations and without the risk of deformation or damage, it is preferable to form the piezoelectric element using an organic piezoelectric layer, and for example, a fluorine-based compound that is a ferroelectric polymer can be used. Indices that represent the characteristics of a piezoelectric material include the piezoelectric strain constant d, the voltage output constant g, and the piezoelectric stress constants e and h, and in particular, the voltage output constant g is obtained by dividing the "strength of the generated electric field" by the "applied stress", and it is advantageous to employ an organic piezoelectric layer with a high voltage output constant g in order to achieve the object of the present invention. For example, the _g31 voltage output constant of β-type polyvinylidene fluoride obtained by uniaxially stretching nonpolar α-type polyvinylidene fluoride and then performing a polarization treatment after the uniaxial stretching is 0.174 (V·m/N), the _g31 voltage output constant of a copolymer containing 55% vinylidene fluoride and the remainder trifluoroethylene is 0.160 (V·m/N), and the _g31 voltage output constant of a copolymer containing 75% vinylidene fluoride and the remainder trifluoroethylene is 0.110 (V·m/N), while the _g31 voltage output constant of quartz is 0.050 (V·m/N) and the _g31 voltage output constant of lead zirconate titanate is 0.010 (V·m/N), and the above-mentioned fluorine-based compounds are preferable as the organic piezoelectric layer forming material of the present invention. The subscript 31 of the voltage output constant g above means that "the stress is in one axis direction, and the normal direction of the electrode surface is in three axes directions."

When the valve opening/closing detection system 21 shown in Figure 3 is applied to a semiconductor manufacturing device to control the flow rate of pure water for cleaning silicon wafers or chemicals for etching, some of the chemicals sprayed onto silicon wafers 29 through flow path 22 may volatilize, causing flammable gas to be contained in the indoor atmosphere. If the amount of electrical energy required to detect the opening and closing of flow control valve 26 is large at that time, the flammable gas may ignite and, in the worst case, lead to an explosion. However, since the amount of energy of a piezoelectric element when exerting the positive piezoelectric effect (the function of converting an external force applied to a piezoelectric element into a voltage) is extremely small, such an explosion does not occur, as will be explained below.

Now, if the impedance R of the open/close detection sensor of the piezoelectric element is 1 MΩ to 1 GΩ, and the generated voltage V is 170 mV, the energy W (J/sec) when the piezoelectric element exerts the positive piezoelectric effect = (V x V) / R, and W = 2.89 x 10 ^-11 to 10 ^-8 (J/sec). If the larger amount of energy is converted to mJ, it becomes 2.89 x 10 ^-5 (mJ/sec). Assuming that the same voltage is generated for about 250 milliseconds, which is the detection time of the open/close detection sensor, 0.723 x 10 ^-5 (mJ) of energy will be generated. For example, if isopropyl alcohol is contained in the fluid flowing through the flow path 22 in Figure 3, the flash point of isopropyl alcohol is 11.7 ° C., and it is highly flammable and dangerous. However, since the minimum ignition energy is 0.51 mJ, even if a portion of the isopropyl alcohol volatilizes and is contained in the indoor atmosphere, the isopropyl alcohol will not ignite.

Second Embodiment
As shown in the overall schematic diagram of FIG. 5, the valve opening/closing detection system 41 of the second embodiment includes a flow path 42, a pressure sensor 43, a temperature sensor 44, a flow meter 45, a flow control valve 46, a valve indicator 47, a controller 48, and a silicon wafer 49, which function similarly to the valve opening/closing detection system 21 of the first embodiment shown in FIG. 3. The valve opening/closing detection system 41 of the second embodiment differs from the valve opening/closing detection system 21 of the first embodiment in that it includes an opening/closing valve 46a and a second valve indicator 47a downstream of the flow control valve 46. In this way, by providing a plurality of valves and valve indicators in series with the flow path 42, it is possible to detect flow control by the combination of the flow control valve 46 and the valve indicator 47 on the upstream side, and to detect the opening/closing of the valve by the combination of the opening/closing valve 46a and the second valve indicator 47a on the downstream side. Generally, a needle valve is often used as a flow control structure, and particles are likely to be generated because the tapered part of the needle valve comes into contact with the orifice part that forms the flow path in order to stop the flow of the fluid in the flow path. Therefore, an on-off valve with a structure that does not easily generate particles is disposed downstream. If an on-off valve is disposed upstream, particles in a fluid such as pure water or a chemical liquid flowing through the flow path when the on-off valve is fully closed tend to accumulate between the tapered portion of the needle valve and the piping that forms the flow path. Therefore, it is preferable to dispose a flow control valve upstream and an on-off valve downstream. Furthermore, if necessary, a combination of a second on-off valve and a third valve indicator, or a combination of a third on-off valve and a fourth valve indicator, can be provided downstream of the on-off valve 46a.

Third embodiment
As shown in the overall schematic diagram of Fig. 6, a valve opening/closing detection system 51 of the third embodiment includes a flow path 52, a pressure sensor 53, a temperature sensor 54, a flow meter 55, a flow control valve 56, a valve indicator 57, a controller 58, and a silicon wafer 59, which function similarly to the valve opening/closing detection system 21 of the first embodiment shown in Fig. 3. The valve opening/closing detection system 51 of the third embodiment differs from the valve opening/closing detection system 21 of the first embodiment in that a first bypass flow path 52a is provided to bypass the flow path 52, and a second flow control valve 56a and a second valve indicator 57a are provided in the first bypass flow path 52a. In this way, by providing a flow control valve and a valve indicator in a direction parallel to the flow path 52, it is possible to detect the opening and closing of flow control valves with different set flow rates by the combination of the flow control valve 56 and the valve indicator 57 provided in the flow path 52 and the combination of the second flow control valve 56a and the second valve indicator 57a provided in the first bypass flow path 52a. Furthermore, if necessary, in addition to the first bypass flow path 52a, a second bypass flow path may be provided to bypass the flow path 52, and/or a third bypass flow path may be provided, so that each bypass flow path is provided with a combination of a flow control valve and a valve indicator.

(Fourth embodiment)
As shown in the overall schematic diagram of Fig. 7, a valve opening and closing detection system 61 of the fourth embodiment includes a flow path 62, a pressure sensor 63, a temperature sensor 64, a flow meter 65, a flow control valve 66, a valve indicator 67, a controller 68, and a silicon wafer 69, which function similarly to the valve opening and closing detection system 21 of the first embodiment shown in Fig. 3. The valve opening and closing detection system 61 of the fourth embodiment differs from the valve opening and closing detection system 21 of the first embodiment in that it includes a second flow control valve 66a and a second valve indicator 67a downstream of the flow control valve 66, a first bypass flow path 62a is provided to bypass the flow path 62, and a third flow control valve 66b and a third valve indicator 67b are provided in the first bypass flow path 62a. In this way, by providing a plurality of flow control valves and valve indicators in series and parallel directions to flow path 62, it is possible to detect the opening and closing of the flow control valve in the main flow path by the combination of the upstream flow control valve 66 and valve indicator 67, and to detect the opening and closing of flow control valves with different set flow rates by the combination of the second flow control valve 66a and second valve indicator 67a on the downstream side and the combination of the third flow control valve 66b and third valve indicator 67b provided in the first bypass flow path 62a.

Fifth Embodiment
As shown in the overall schematic diagram of Fig. 8, a valve opening and closing detection system 71 of the fifth embodiment includes a flow path 72, a pressure sensor 73, a temperature sensor 74, a flow meter 75, a controller 78, and a silicon wafer 79, which function similarly to the valve opening and closing detection system 21 of the first embodiment shown in Fig. 3. The valve opening and closing detection system 71 of the fifth embodiment differs from the valve opening and closing detection system 21 of the first embodiment in that a flow control valve 76 and a valve indicator 77 are provided in the flow path 72, a first bypass flow path 72a is provided to bypass the flow path 72, a second flow control valve 76a and a second valve indicator 77a are provided in the first bypass flow path 72a, and an opening and closing valve 76b and a third valve indicator 77b are provided downstream of the flow control valve 76. In this way, by providing a plurality of valves and valve indicators in series and parallel directions to the flow path 72, the combination of the upstream flow control valve 76 and valve indicator 77 and the combination of the second flow control valve 76a and second valve indicator 77a provided in the first bypass flow path 72a can detect the opening and closing of flow control valves with different set flow rates, and the combination of the downstream opening and closing valve 76b and third valve indicator 77b can detect the opening and closing of the valves.

The valve indicator of the present invention can be used in a variety of industrial applications as an instrument for detecting the opening and closing of valves that control the flow rate of various liquids and gases.

1 Resin wire 3, 3a, 3b Metal foil 5 Core wire 7 Organic piezoelectric layer 9 Conductor layer 11 Insulator layer 20 Piezoelectric element 21 Valve opening/closing detection system 22, 42, 52, 62, 72 Flow path 23, 43, 53, 63, 73 Pressure sensor 24, 44, 54, 64, 74 Temperature sensor 25, 45, 55, 65, 75 Flow meter 26, 46, 56, 66, 76 Flow control valve 27, 47, 57, 67, 77 Valve indicator 28, 48, 58, 68, 78 Controller 29, 49, 59, 69, 79 Silicon wafer 31 Diaphragm 32 Valve block 32a Upstream portion 32b Downstream portion 33 Piezo actuator 34 Input/output end 35 of piezoelectric actuator 33 Protrusion 46a, 76b Opening and closing valves 56a, 66a 76a Second flow control valves 47a, 57a, 67a, 77a Second valve indicators 52a, 62a, 72a First bypass flow path 66b Third flow control valves 67b, 77b Third valve indicators _D1 , _D2 Outer dimension P Spiral pitch G Gap

Claims (4)

a valve opening/closing detection system including 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 layer covering the organic piezoelectric layer, the metal foil and the conductor layer being piezoelectric elements each functioning as an electrode with the organic piezoelectric layer interposed therebetween, and a valve indicator for detecting the opening and closing of a valve based on a voltage value generated between electrodes on both sides of the piezoelectric element due to a change in contact pressure on the piezoelectric element, the valve opening/closing detection system including a pressure sensor, a temperature sensor, a flow meter, and a flow control valve equipped with the valve indicator from the upstream side to the downstream side of a flow path through which a fluid flows, a controller for controlling, monitoring and calculating the operation of the pressure sensor, the temperature sensor, the flow meter and the flow control valve, and an opening/closing valve and the valve indicator for detecting the opening and closing of the valve are provided in the flow path downstream of the flow control valve. 2. The valve opening/closing detection system according to claim 1, characterized in that, instead of an opening/closing valve and a valve indicator provided downstream of the flow control valve, a bypass flow path is provided from the flow path downstream of the flow meter to bypass the flow control valve and reach the flow path downstream of the flow control valve, and a second flow control valve and the valve indicator that detects the opening and closing of the valve are provided in the bypass flow path. 2. The valve opening/closing detection system according to claim 1, further comprising: a second flow control valve and the valve indicator for detecting the opening/closing of the valve are provided in the flow path downstream of the flow control valve, instead of an opening/closing valve and a valve indicator provided downstream of the flow control valve; and a bypass flow path is provided from the flow path downstream of the flow control valve to bypass the second flow control valve and reach the flow path downstream of the second flow control valve, and a third flow control valve and the valve indicator for detecting the opening/closing of the valve are provided in the bypass flow path. 2. The valve opening/closing detection system according to claim 1, further comprising, in addition to an opening/closing valve and a valve indicator provided in the flow path downstream of the flow control valve, a bypass flow path is provided from the flow path downstream of the flow meter to bypass the flow control valve and reach the flow path upstream of the opening/closing valve, and a second flow control valve and the valve indicator that detects the opening and closing of the valve are provided in the bypass flow path.

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