Piezoelectric coaxial sensor and method for manufacturing a piezoelectric coaxial sensor

Abstract

A piezoelectric coaxial sensor (1) is provided with a sensor portion (S) having a linear center conductor (11), a polyvinylidene fluoride-containing polymer piezoelectric body layer (12) covering the outer peripheral surface of the center conductor (11), and a first outer conductor (13) surrounding the outer peripheral surface of the polymer piezoelectric body layer (12), and at least one sheath layer having a tape-like film wound around the outer peripheral surface of the sensor portion (S), the film of the sheath layer exposed to the outside being adhered to a member contacted by an adhesive layer composed of a thermoplastic resin having a melting point of 120°C or lower.

Description

Technical Field

[0001] This invention relates to a piezoelectric coaxial sensor for suppressing the deterioration of output characteristics and a method for manufacturing the piezoelectric coaxial sensor. Background Technology

[0002] A piezoelectric coaxial sensor is known to have a piezoelectric element disposed between the center conductor and the outer conductor of a coaxial cable. The piezoelectric coaxial sensor detects the voltage of the piezoelectric element generated when a force is applied from the outer peripheral surface of the sensor via the center conductor and the outer conductor, thereby detecting the force. This property is used to detect deformation of the object being measured, the force applied to the object, vibration, etc., where the piezoelectric coaxial sensor is disposed. For the piezoelectric element of such a piezoelectric coaxial sensor, it is known to use a piezoelectric element made of a polymer piezoelectric material composed of polyvinylidene fluoride (PVDF).

[0003] Patent Document 1 describes such a piezoelectric coaxial sensor. This piezoelectric coaxial sensor comprises a central conductor, a PVDF-based polymer piezoelectric layer covering the outer periphery of the central conductor, an outer conductor surrounding the outer periphery of the polymer piezoelectric layer, and a sheath layer, i.e., an insulating layer, covering the outer periphery of the outer conductor. This sheath layer is formed by extrusion molding.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-183570

[0005] However, the piezoelectric coaxial sensor described in Patent Document 1 exhibits a tendency for low output. This is believed to be due to the reduction in PVDF polarization during the extrusion molding process to form the sheath layer. Therefore, there is a desire to form the sheath layer by tape winding. In the case of tape winding, at least the tape constituting the exposed sheath needs to be fixed by adhesive. When using adhesive tape, due to manufacturing issues, there is a desire to use an adhesive made of thermoplastic resin; however, if such an adhesive is used, there are concerns about the deterioration of output characteristics due to the reduction in PVDF polarization upon heating. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a piezoelectric coaxial sensor that suppresses the deterioration of output characteristics and a method for manufacturing the piezoelectric coaxial sensor.

[0007] To address the aforementioned issues, the piezoelectric coaxial sensor of the present invention is characterized by comprising a sensor portion and at least one sheath layer. The sensor portion has a linear central conductor, a polymeric piezoelectric layer comprising polyvinylidene fluoride covering the outer peripheral surface of the central conductor, and a first external conductor surrounding the outer peripheral surface of the polymeric piezoelectric layer. The sheath layer has a strip-shaped film wound around the outer peripheral surface of the sensor portion. The film of the sheath layer exposed to the outside is bonded to a component in contact with the adhesive layer by an adhesive layer made of a thermoplastic resin with a melting point of 120°C or less.

[0008] Furthermore, to address the aforementioned issues, the manufacturing method of the piezoelectric coaxial sensor of the present invention is characterized by comprising a preparation step and a sheath layer forming step. The preparation step is a step of preparing a sensor portion having a linear central conductor, a polymer piezoelectric layer comprising polyvinylidene fluoride covering the outer peripheral surface of the central conductor, and a first external conductor surrounding the outer peripheral surface of the polymer piezoelectric layer. The sheath layer forming step is a step of forming at least one sheath layer having a strip-shaped film wound around the outer peripheral surface of the sensor portion. The sheath layer forming step includes forming an upper... The exposed sheath forming process of the sheath layer in the described sheath layer includes a winding process and an adhesive process. The winding process is a process in which the film of the exposed sheath layer is wrapped around the outer peripheral surface of the sensor part by an adhesive layer made of a thermoplastic resin with a melting point of 120°C or less. The adhesive process is a process in which the sensor part with the film of the exposed sheath layer wrapped around it is heated to 120°C or less, thereby bonding the film to the component by the adhesive layer.

[0009] The inventors used an adhesive layer made of thermoplastic resin as a binder to fix the film to the sensor portion at various temperatures. As a result, it was discovered that when the polymer piezoelectric layer of the piezoelectric coaxial sensor contains PVDF, heating below 120 degrees Celsius suppresses the deterioration of output characteristics. This is believed to be because heating under such conditions suppresses the reduction of PVDF polarization. Therefore, in the piezoelectric coaxial sensor of the present invention, an externally exposed sheath layer can be formed by heating below 120 degrees Celsius, thereby suppressing the reduction of PVDF polarization. Thus, the piezoelectric coaxial sensor can suppress the deterioration of output characteristics. Furthermore, the manufacturing method of the piezoelectric coaxial sensor of the present invention, by forming an externally exposed sheath layer by heating below 120 degrees Celsius, enables the manufacture of a piezoelectric coaxial sensor that suppresses the reduction of PVDF polarization and thus suppresses the deterioration of output characteristics.

[0010] Alternatively, the aforementioned thermoplastic resin may contain an ethylene vinyl acetate copolymer.

[0011] In this case, it can become an adhesive layer with a melting point below 120 degrees Celsius.

[0012] Furthermore, preferably, the piezoelectric coaxial sensor described above includes a first sheath layer, a second outer conductor, and a second sheath layer. The first sheath layer includes one or more sheath layers and covers the outer peripheral surface of the sensor portion. The second outer conductor surrounds the outer peripheral surface of the first sheath layer. The second sheath layer includes one or more sheath layers and covers the outer peripheral surface of the second outer conductor. The outermost sheath layer of the second sheath layer is the sheath layer exposed to the outside.

[0013] Furthermore, preferably, the manufacturing method of the piezoelectric coaxial sensor described above includes a first sheath layer forming step, a second outer conductor forming step, and a second sheath layer forming step. The first sheath layer forming step is a step of forming a first sheath layer that includes one or more of the aforementioned sheath layers and covers the outer peripheral surface of the sensor portion. The second outer conductor forming step is a step of forming a second outer conductor that surrounds the outer peripheral surface of the first sheath layer. The second sheath layer forming step is a step of forming a second sheath layer that includes one or more of the aforementioned sheath layers and covers the outer peripheral surface of the second outer conductor. The outermost sheath layer of the second sheath layer is the sheath layer exposed to the outside.

[0014] In this piezoelectric coaxial sensor and its manufacturing method, the second outer conductor functions as a shielding layer, suppressing the influence of external electromagnetic fields and the like from reaching the center conductor and the first outer conductor. Therefore, noise superimposed on the center conductor and the first outer conductor due to external electromagnetic fields can be suppressed. Consequently, the piezoelectric coaxial sensor exhibits excellent noise immunity characteristics. Furthermore, noise immunity is a characteristic that suppresses external noise; in cases of high noise immunity, the signal-to-noise ratio (S / N) is high. Additionally, the second sheath layer insulates the outer peripheral surface of the second outer conductor, which functions as a shielding layer, from the outside. Therefore, noise superimposed on the center conductor and the first outer conductor via the second outer conductor can be further suppressed.

[0015] Furthermore, it is preferable that, in the case where the piezoelectric coaxial sensor has a first sheath layer, a second outer conductor, and a second sheath layer as described above, the first sheath layer has an inner first sheath layer and an outer first sheath layer, the inner first sheath layer covers the outer peripheral surface of the sensor portion and the film of the inner first sheath layer is not adhered to the sensor portion, the outer first sheath layer covers the outer peripheral surface of the inner first sheath layer and the film of the outer first sheath layer is adhered to the inner first sheath layer by the adhesive layer.

[0016] Furthermore, preferably, in the case where the manufacturing method of the piezoelectric coaxial sensor as described above includes a first sheath layer forming step, a second outer conductor forming step, and a second sheath layer forming step, the first sheath layer forming step includes an inner first sheath layer forming step for forming an inner first sheath layer and an outer first sheath layer forming step for forming an outer first sheath layer. The inner first sheath layer covers the outer peripheral surface of the sensor portion, and the film of the inner first sheath layer is not adhered to the sensor portion. The outer first sheath layer covers the outer peripheral surface of the inner first sheath layer, and the film of the outer first sheath layer is adhered to the inner first sheath layer by the adhesive layer. The first sheath layer, the outer first sheath layer forming process includes an outer first sheath layer winding process and an outer first sheath layer bonding process. The outer first sheath layer winding process is a process in which the film that will become the outer first sheath layer is wound around the outer peripheral surface of the inner first sheath layer via the adhesive layer. The outer first sheath layer bonding process is a process in which the inner first sheath layer and the sensor part, which have the film that will become the outer first sheath layer wound in the outer first sheath layer winding process, are heated at a temperature below 120°C, thereby bonding the film that will become the outer first sheath layer to the inner first sheath layer via the adhesive layer.

[0017] According to this piezoelectric coaxial sensor and its manufacturing method, the inner first sheath layer is not bonded to the sensor portion, thereby facilitating the removal of the sensor portion. Furthermore, the outer first sheath layer is bonded to the inner first sheath layer, thus preventing the first sheath layer from detaching even if the piezoelectric coaxial sensor buckles. Additionally, according to this piezoelectric coaxial sensor, the first sheath layer can be formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization and preventing the deterioration of output characteristics. Furthermore, according to this manufacturing method of the piezoelectric coaxial sensor, the first sheath layer is formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization.

[0018] Furthermore, it is preferable that, in the case where the piezoelectric coaxial sensor has a first sheath layer, a second outer conductor, and a second sheath layer as described above, the second sheath layer has an inner second sheath layer and an outer second sheath layer, the inner second sheath layer covers the outer peripheral surface of the second outer conductor and the film of the inner second sheath layer is not adhered to the second outer conductor, the outer second sheath layer is the outermost sheath layer of the second sheath layer, and covers the outer peripheral surface of the inner second sheath layer and the film of the outer second sheath layer is adhered to the inner second sheath layer by the adhesive layer.

[0019] Furthermore, it is preferable that, in the case where the manufacturing method of the piezoelectric coaxial sensor as described above includes a first sheath layer forming step, a second outer conductor forming step, and a second sheath layer forming step, the second sheath layer forming step includes an inner second sheath layer forming step for forming an inner second sheath layer and an outer second sheath layer forming step for forming an outer second sheath layer. The inner second sheath layer covers the outer peripheral surface of the second outer conductor and the film of the inner second sheath layer is not adhered to the second outer conductor. The outer second sheath layer is the outermost sheath layer of the second sheath layer and covers the outer peripheral surface of the inner second sheath layer. The film of the outer second sheath layer is adhered to the inner second sheath layer by the adhesive layer. The outer second sheath layer forming step is the exposed sheath forming step.

[0020] According to this piezoelectric coaxial sensor and its manufacturing method, the inner second sheath layer is not bonded to the second outer conductor, thereby facilitating the lead-out of the second outer conductor. Furthermore, the outer second sheath layer is bonded to the inner second sheath layer, thus preventing the second sheath layer from unraveling even in the event of buckling of the piezoelectric coaxial sensor. Additionally, according to this piezoelectric coaxial sensor, the second sheath layer can be formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization and preventing the deterioration of output characteristics. Furthermore, according to this manufacturing method of the piezoelectric coaxial sensor, the second sheath layer is formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization.

[0021] As described above, according to the present invention, a piezoelectric coaxial sensor that suppresses the deterioration of output characteristics and a method for manufacturing the piezoelectric coaxial sensor can be provided. Attached Figure Description

[0022] Figure 1 This is a diagram illustrating the piezoelectric coaxial sensor according to an embodiment of the present invention.

[0023] Figure 2 It means Figure 1 A diagram showing the construction of a piezoelectric coaxial sensor in a cross-section perpendicular to its length.

[0024] Figure 3 It means manufacturing Figure 1 The flowchart of the process for making a piezoelectric coaxial sensor.

[0025] Figure 4 It is a diagram showing the state after the preparation process.

[0026] Figure 5 This diagram shows the state of the formation process of the inner first sheath layer.

[0027] Figure 6This diagram shows the state of the outer first sheath layer winding process.

[0028] Figure 7 This diagram shows the state of the bonding process for the outer first sheath layer.

[0029] Figure 8 This is a diagram showing the state after the second outer conductor is formed.

[0030] Figure 9 This diagram shows the state of the process of forming the inner second sheath layer.

[0031] Figure 10 This diagram shows the state of the outer second sheath layer winding process.

[0032] Figure 11 This is a graph showing the relationship between the set temperature of the heating furnace and the measured voltage generated by the piezoelectric coaxial sensor. Detailed Implementation

[0033] The following is related to the appendix. Figure 1 The following examples illustrate methods for implementing the piezoelectric coaxial sensor according to the present invention. The embodiments illustrated below are for the purpose of facilitating understanding of the invention and are not intended to limit the interpretation of the invention. The invention can be modified and improved according to the following embodiments without departing from its spirit. Furthermore, in this specification, the dimensions of the components are exaggerated for ease of understanding.

[0034] Figure 1 This is a diagram illustrating the piezoelectric coaxial sensor according to this embodiment. (See diagram for example.) Figure 1 As shown, the piezoelectric coaxial sensor 1 of this embodiment includes a central conductor 11, a polymer piezoelectric layer 12, a first outer conductor 13, a first sheath layer 14, a second outer conductor 15, and a second sheath layer 16.

[0035] The center conductor 11 is a linear conductor composed of strands of multiple conductive wires. The center conductor 11 is not particularly limited to any conductor; for example, conductors made of copper, aluminum, or tin-plated soft copper alloys can be used. Furthermore, in... Figure 1 The example shown is of a center conductor 11 consisting of strands of multiple conductive wires as described above, but the center conductor 11 may also be a linear conductor consisting of a single conductive wire.

[0036] The polymer piezoelectric layer 12 is a layer covering the outer peripheral surface of the central conductor 11. In this embodiment, the polymer piezoelectric layer 12 is in contact with the outer peripheral surface of the central conductor 11. The polymer piezoelectric layer 12 exhibits piezoelectricity and is composed of a polymer containing PVDF. The polymer piezoelectric layer 12 is formed into a generally circular cross-sectional shape by extrusion molding or the like. Alternatively, the polymer piezoelectric layer 12 can also be formed by winding a strip-shaped film made of a polymer piezoelectric material containing PVDF around the central conductor 11. In this case, the film can be wound in a helical manner or in a longitudinal manner.

[0037] The first outer conductor 13 is a conductor surrounding the outer peripheral surface of the polymer piezoelectric layer 12. In this embodiment, the first outer conductor 13 is in contact with the outer peripheral surface of the polymer piezoelectric layer 12. The first outer conductor 13 is a structure formed by multiple wires wound in the same direction in a spiral shape. Such a first outer conductor 13 is not particularly limited as long as it is made of a conductor, for example, it can be made of the same conductor as the central conductor 11. Furthermore, in Figure 1 The image shows an example of multiple wires wound in a spiral shape as the first outer conductor 13, but the first outer conductor 13 can also be a mesh made of multiple wires.

[0038] The sensor section S is constructed using a central conductor 11, a polymer piezoelectric layer 12, and a first outer conductor 13, all formed by the above structure. Furthermore, as described above, the polymer piezoelectric layer 12 is in contact with the outer peripheral surface of the central conductor 11, and the first outer conductor 13 is in contact with the outer peripheral surface of the polymer piezoelectric layer 12. Therefore, in the sensor section S, when an external force applied to the piezoelectric coaxial sensor 1 is transmitted to the polymer piezoelectric layer 12, and an induced charge is generated in the polymer piezoelectric layer 12, a voltage is generated between the central conductor 11 and the first outer conductor 13 based on the induced charge generated in the polymer piezoelectric layer 12. Therefore, by inducing and measuring the voltage between the central conductor 11 and the first outer conductor 13 on the outside of the piezoelectric coaxial sensor 1, the force applied to the piezoelectric coaxial sensor 1 can be measured.

[0039] Figure 2 It means Figure 1 This is a diagram showing the structure of a piezoelectric coaxial sensor 1 in a cross-section perpendicular to its length. The first sheath layer 14 is a layer that covers the outer peripheral surface of the first outer conductor 13. Therefore, the first sheath layer 14 covers the outer peripheral surface of the sensor portion S. Figure 1 , Figure 2 As shown, in this embodiment, the first sheath layer 14 has two sheath layers: an inner first sheath layer 14a and an outer first sheath layer 14b.

[0040] The inner first sheath layer 14a is formed by a strip-shaped film 14at made of resin, which is wound in a spiral shape on the outer peripheral surface of the first outer conductor 13. No adhesive layer is provided on either side of the film 14at, and the inner first sheath layer 14a is not adhered to the first outer conductor 13. The material of the film 14at is not particularly limited, but insulating resins such as polyethylene terephthalate, polyethylene naphthalate, polyimide, polyvinyl chloride, polypropylene, polyetheretherketone, polyetherimide, and polyphenylene sulfide can be used as examples. Alternatively, an adhesive layer may be provided on one side of the film 14at, but in this case, from the viewpoint that the inner first sheath layer 14a and the first outer conductor 13 can be easily peeled off when the first outer conductor 13 is led out, it is preferable that the adhesive layer is provided on the side of the film 14at that becomes the outer side of the inner first sheath layer 14a.

[0041] like Figure 2 As shown, the outermost first sheath layer 14b is the outermost sheath layer of the first sheath layer 14, and is composed of a strip-shaped film 14bt made of resin and an adhesive layer 14ba disposed on one side of the film 14bt. For the film 14bt, the adhesive layer 14ba faces the inner first sheath layer 14a and is wound in a spiral shape on the outer peripheral surface of the inner first sheath layer 14a. Therefore, the adhesive layer 14ba contacts the inner first sheath layer 14a, and the film 14bt is bonded to the inner first sheath layer 14a through the adhesive layer 14ba. Furthermore, in Figure 1 In the example, the film 14bt of the outer first sheath layer 14b and the film 14at of the inner first sheath layer 14a are wound in the same direction, but they can also be wound in opposite directions. Additionally, at least one of the films 14at and 14bt can be wound longitudinally. The material of the film 14bt is not particularly limited, but the same material as the film 14at can be used, for example. The adhesive used in the adhesive layer 14ba is composed of a thermoplastic resin with a melting point below 120°C. For example, ethylene vinyl acetate copolymer (EVA) can be used as such a resin. By including EVA, the melting point of the thermoplastic resin can be made below 120°C.

[0042] Furthermore, when the adhesive layer is provided on the surface of the membrane 14at that is the outer side of the inner first sheath layer 14a, as described above, the adhesive layer is exposed on the outer peripheral surface of the inner first sheath layer 14a. Therefore, it is possible to not provide an adhesive layer on any side of the membrane 14bt, or to provide an adhesive layer 14ba on the surface of the membrane 14bt on the side of the inner first sheath layer 14a, as described above. Even if no adhesive layer is provided on any side of the membrane 14at as described above, the adhesive layer 14ba may not be provided. However, from the viewpoint of suppressing the membrane 14bt from unraveling under repeated bending of the piezoelectric coaxial sensor 1, it is preferable to provide the adhesive layer 14ba as described above.

[0043] Alternatively, either the inner first sheath layer 14a or the outer first sheath layer 14b can be omitted, and the first sheath layer 14 can be composed of the other one of the inner first sheath layer 14a and the outer first sheath layer 14b. However, from the viewpoint that the first sheath layer 14 and the first outer conductor 13 can be easily peeled off, and that the first sheath layer 14 can be prevented from detaching, it is preferable that the first sheath layer 14 is composed of a non-adhesive inner first sheath layer 14a and an outer first sheath layer 14b having an adhesive layer 14ba, as described above.

[0044] The second outer conductor 15 is a conductor that surrounds the outer peripheral surface of the first sheath layer 14. The second outer conductor 15 is a structure formed by multiple wires wound in a spiral shape in the same direction. Such a second outer conductor 15 is not particularly limited in that it is made of any conductor, for example, it can be made of the same conductor as the first outer conductor 13. Furthermore, in Figure 1 The image shows an example of multiple wires wound in a spiral shape as the second outer conductor 15, but the second outer conductor 15 can also be a mesh made of multiple wires.

[0045] The second sheath layer 16 is a layer that covers the outer peripheral surface of the second outer conductor 15. In this embodiment, the second sheath layer 16 has two sheath layers: an inner second sheath layer 16a and an outer second sheath layer 16b.

[0046] The inner second sheath layer 16a is formed by a strip-shaped film 16at made of resin, which is wound in a spiral shape on the outer peripheral surface of the second outer conductor 15. No adhesive layer is provided on either side of the film 16at, and the inner second sheath layer 16a is not adhered to the second outer conductor 15. The material of the film 16at is not particularly limited, but for example, the same material as the film 14at can be used. Alternatively, an adhesive layer may be provided on one side of the film 16at; however, from the viewpoint that the inner second sheath layer 16a and the second outer conductor 15 can be easily peeled off when the second outer conductor 15 is led out, it is preferable that the adhesive layer is provided on the side of the film 16at that becomes the outer side of the inner second sheath layer 16a.

[0047] like Figure 1 , Figure 2 As shown, the outermost second sheath layer 16b is the outermost sheath layer of the second sheath layer 16, and is the sheath layer exposed to the outside. The outer second sheath layer 16b is composed of a strip-shaped film 16bt made of resin and an adhesive layer 16ba disposed on one side of the film 16bt. For the film 16bt, the adhesive layer 16ba faces the inner second sheath layer 16a and is wound in a spiral shape on the outer peripheral surface of the inner second sheath layer 16a. Therefore, the adhesive layer 16ba contacts the inner second sheath layer 16a, and the film 16bt is adhered to the inner second sheath layer 16a through the adhesive layer 16ba. Furthermore, in Figure 1 In the example, the film 16bt of the outer second sheath layer 16b and the film 16at of the inner second sheath layer 16a are wound in the same direction, but they can also be wound in opposite directions. Additionally, at least one of the films 16at and 16bt can be wound longitudinally. The material of the film 16bt is not particularly limited, but the same material as the film 16at can be used, for example. The adhesive used in the adhesive layer 16ba is composed of a thermoplastic resin with a melting point below 120°C. Therefore, the adhesive used in the adhesive layer 16ba can be, for example, composed of the same thermoplastic resin as the thermoplastic resin used in the adhesive layer 14ba.

[0048] Furthermore, if the adhesive layer is provided on the outer side of the inner second sheath layer 16a of the membrane 16at as described above, the adhesive layer is exposed on the outer peripheral surface of the inner second sheath layer 16a. Thus, the adhesive layer may not be provided on any side of the membrane 16bt, or the adhesive layer 16ba may be provided on the side of the inner second sheath layer 16a of the membrane 16bt as described above.

[0049] Alternatively, the inner second sheath layer 16a can be omitted, and the second sheath layer 16 can be composed of the outer second sheath layer 16b. However, from the viewpoint that the second sheath layer 16 and the second outer conductor 15 can be easily peeled off and that the second sheath layer 16 can be prevented from detaching, it is preferable that the second sheath layer 16 is composed of a non-adhesive inner second sheath layer 16a and an outer second sheath layer 16b having an adhesive layer 16ba, as described above.

[0050] As described above, the piezoelectric coaxial sensor 1 of this embodiment includes a sensor part S and at least one sheath layer. The sensor part S has a linear central conductor 11, a PVDF-containing polymer piezoelectric layer 12 covering the outer peripheral surface of the central conductor 11, and a first external conductor 13 surrounding the outer peripheral surface of the polymer piezoelectric layer 12. The sheath layer has a strip-shaped film wound around the outer peripheral surface of the sensor part S. The film 16bt of the outer second sheath layer 16b exposed to the outside of the sheath layer is bonded to the inner second sheath layer 16a in contact with the adhesive layer 16ba by an adhesive layer 16ba made of a thermoplastic resin with a melting point of 120°C or less.

[0051] In the piezoelectric coaxial sensor 1 with this structure, the outer second sheath layer 16b exposed to the outside can be formed by heating to below 120°C. Therefore, the reduction in PVDF polarization can be suppressed. Thus, the piezoelectric coaxial sensor 1 of this embodiment can suppress the deterioration of output characteristics.

[0052] In addition, the thermoplastic resin constituting the adhesive layer 16ba includes an ethylene vinyl acetate copolymer, thereby enabling the adhesive layer 16ba to have a melting point below 120°C.

[0053] Furthermore, the piezoelectric coaxial sensor 1 of this embodiment includes a first sheath layer 14, a second outer conductor 15, and a second sheath layer 16. The first sheath layer 14 includes one or more sheath layers and covers the outer peripheral surface of the sensor portion S. The second outer conductor 15 surrounds the outer peripheral surface of the first sheath layer 14. The second sheath layer 16 includes one or more sheath layers and covers the outer peripheral surface of the second outer conductor 15. The outermost sheath layer of the second sheath layer 16, i.e., the outer second sheath layer 16b, is exposed to the outside. In this piezoelectric coaxial sensor 1, the second outer conductor 15 functions as a shielding layer, suppressing the influence of external electromagnetic fields, etc., from reaching the center conductor 11 and the first outer conductor 13. Therefore, noise superimposed on the center conductor 11 and the first outer conductor 13 due to external electromagnetic fields, etc., can be suppressed. Therefore, the piezoelectric coaxial sensor 1 can have excellent noise immunity characteristics. In addition, the second sheath layer 16 can insulate the outer peripheral surface of the second outer conductor 15, which functions as a shielding layer, from the outside. Therefore, the second outer conductor 15 can be reliably grounded, thereby acting as a shielding layer to further suppress noise superimposed on the center conductor 11 and the first outer conductor 13.

[0054] Furthermore, in the piezoelectric coaxial sensor 1 of this embodiment, the first sheath layer 14 has an inner first sheath layer 14a and an outer first sheath layer 14b. The inner first sheath layer 14a covers the outer peripheral surface of the sensor portion S, and the membrane 14at is not adhered to the sensor portion S. The outer first sheath layer 14b covers the outer peripheral surface of the inner first sheath layer 14a, and the membrane 14bt is adhered to the inner first sheath layer 14a by the adhesive layer 14ba. According to this piezoelectric coaxial sensor 1, the inner first sheath layer 14a is not adhered to the sensor portion S, thereby facilitating the extraction of the sensor portion S. Therefore, the first external conductor 13 can be easily connected to other components. In addition, the outer first sheath layer 14b is adhered to the inner first sheath layer 14a, thereby preventing the first sheath layer 14 from unraveling even if the piezoelectric coaxial sensor 1 is bent. Furthermore, according to such a piezoelectric coaxial sensor 1, the first sheath layer 14 can be formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization and thus suppressing the deterioration of output characteristics.

[0055] Furthermore, in the piezoelectric coaxial sensor 1 of this embodiment, the second sheath layer 16 has an inner second sheath layer 16a and an outer second sheath layer 16b. The inner second sheath layer 16a covers the outer peripheral surface of the second outer conductor 15, and the film 16at is not adhered to the second outer conductor 15. The outer second sheath layer 16b is the outermost sheath layer of the second sheath layer 16, and covers the outer peripheral surface of the inner second sheath layer 16a, with the film 16bt adhered to the inner second sheath layer 16a by the adhesive layer 16ba. According to this piezoelectric coaxial sensor 1, the inner second sheath layer 16a is not adhered to the second outer conductor 15, thereby facilitating the lead-out of the second outer conductor 15. Therefore, the second outer conductor 15 can be easily connected to other components such as a ground wire. In addition, the outer second sheath layer 16b is adhered to the inner second sheath layer 16a, thereby preventing the second sheath layer 16 from unraveling even if the piezoelectric coaxial sensor 1 is bent. Furthermore, according to such a piezoelectric coaxial sensor 1, a second sheath layer 16 can be formed by heating to below 120°C, thereby suppressing the reduction of PVDF polarization and thus suppressing the deterioration of output characteristics.

[0056] The manufacturing method of the piezoelectric coaxial sensor 1 will be described next.

[0057] Figure 3 It means manufacturing Figure 1 The flowchart shows the process of manufacturing piezoelectric coaxial sensor 1. Figure 3 As shown, the manufacturing method of the piezoelectric coaxial sensor 1 in this embodiment includes a preparation step P1, a first sheath layer forming step P2, a second outer conductor forming step P3, and a second sheath layer forming step P4.

[0058] <Preparation Process P1>

[0059] This process is for preparing the sensor unit S. As described above, the sensor unit S has a central conductor 11, a polymer piezoelectric layer 12, and a first outer conductor 13. Therefore, the linear central conductor 11 is prepared first. Then, a polymer piezoelectric layer 12 containing PVDF is formed on the outer peripheral surface of the central conductor 11. If... Figure 1 , Figure 2 The polymer piezoelectric layer 12 shown is formed by extrusion molding. Furthermore, unlike... Figure 1 , Figure 2 Instead, in the case where a polymer piezoelectric layer 12 is formed by winding a strip-shaped film made of a PVDF-containing polymer piezoelectric material around a central conductor 11, the film is wound around the central conductor 11 in a helical or longitudinal manner. Next, a first outer conductor 13 is formed on the outer peripheral surface of the polymer piezoelectric layer 12 already formed around the central conductor 11. If... Figure 1 The first external conductor 13 shown is formed by winding multiple wires in a spiral shape around the outer peripheral surface of the polymer piezoelectric layer 12. Alternatively, if the first external conductor 13 is a mesh of multiple wires, the multiple wires are woven into a mesh shape on the outer peripheral surface of the polymer piezoelectric layer 12. In this way, a preparation is made... Figure 4 The sensor unit S is shown.

[0060] Furthermore, the sensor unit S can also be prepared using methods other than those described above. For example, the sensor unit S can also be prepared by purchasing it from an external supplier.

[0061] <First sheath layer formation process P2>

[0062] This process is the process of forming the first sheath layer 14. For example... Figure 3 As shown, this process includes an inner first sheath layer forming process P2a and an outer first sheath layer forming process P2b.

[0063] Process P2a: Formation of the first inner sheath layer

[0064] This process is the process of forming the inner first sheath layer 14a, which covers the outer peripheral surface of the sensor part S and the film 14at is not adhered to the sensor part S. Figure 5 This is a diagram showing the status of this process. For example... Figure 5 As shown, in this process, a film 14at without an adhesive layer on both sides is prepared, and the film 14at is wound spirally onto the outer peripheral surface of the sensor part S. Furthermore, in a manner different from... Figure 5Instead, if the membrane 14at is wound in a longitudinal winding manner, the membrane 14at is wound longitudinally onto the outer peripheral surface of the sensor section S. In this way, the inner first sheath layer 14a is formed.

[0065] Furthermore, when an adhesive layer is provided on the surface of the membrane 14at as described above, the membrane 14at is wound around the outer peripheral surface of the sensor section S with the surface of the membrane 14at where the adhesive layer is provided facing outwards. In this case, the membrane 14at is the part that the adhesive layer contacts.

[0066] Outer First Sheath Layer Formation Process P2b

[0067] This process is the process of forming the outer first sheath layer 14b, which is formed by covering the outer peripheral surface of the inner first sheath layer 14a with a film 14bt and bonding it to the inner first sheath layer 14a through an adhesive layer 14ba. This process includes an outer first sheath layer winding process P2bw and an outer first sheath layer bonding process P2ba.

[0068] (Outer first sheath layer winding process P2bw)

[0069] This process involves wrapping the membrane 14bt, which will become the outer first sheath layer 14b, around the outer peripheral surface of the inner first sheath layer 14a. Figure 6 This is a diagram showing the status of this process. For example... Figure 6 As shown, in this process, a film 14bt with an adhesive layer 14ba is prepared, and the film 14bt is wound spirally onto the outer peripheral surface of the inner first sheath layer 14a in such a way that the adhesive layer 14ba contacts the inner first sheath layer 14a. Furthermore, in a manner different from... Figure 6 Instead, when the membrane 14bt is wound longitudinally, the adhesive layer 14ba and the inner first sheath layer 14a are in contact, and the membrane 14bt is wound longitudinally onto the outer peripheral surface of the inner first sheath layer 14a. This results in the adhesive layer 14ba being in contact with the inner first sheath layer 14a, and the membrane 14bt being wound onto the outer peripheral surface of the inner first sheath layer 14a. Furthermore, through this process, the membrane 14bt surrounds the outer peripheral surface of the sensor section S via the inner first sheath layer 14a.

[0070] Furthermore, when an adhesive layer is provided on the surface of the membrane 14at as described above, and the membrane 14at is wrapped around the outer peripheral surface of the sensor section S with the surface of the membrane 14at with the adhesive layer on the outside as the outside, the membrane 14bt without the adhesive layer 14ba can also be wrapped around the outer peripheral surface of the inner first sheath layer 14a via the adhesive layer on the membrane 14at, or the membrane 14bt with the adhesive layer 14ba can be wrapped around the outer peripheral surface of the inner first sheath layer 14a as described above.

[0071] In this way, the film 14bt, which becomes the outer first sheath layer 14b, is wrapped around the outer peripheral surface of the inner first sheath layer 14a via an adhesive layer.

[0072] Furthermore, as described above, in the first sheath layer forming process P2, an adhesive layer may not be provided on either the surface of film 14at or film 14bt.

[0073] (Outer first sheath layer bonding process P2ba)

[0074] This process involves bonding the membrane 14bt of the outer first sheath layer 14b to the inner first sheath layer 14a using the adhesive layer 14ba. In this process, the inner first sheath layer 14a with the membrane 14bt wrapped around it and the sensor part S are heated to below 120°C, thereby bonding the membrane 14bt to the inner first sheath layer 14a using the adhesive layer 14ba. Figure 7 This is a diagram showing the state of this process. In this process of this embodiment, the membrane 14bt is wound as described above, and the heated body 1a, which is composed of the membrane 14bt, the inner first sheath layer 14a, and the sensor part S, is passed through the heating furnace H to heat the heated body 1a.

[0075] The heated object 1a is wound onto a reel R1 before passing through the heating furnace H. The heated object 1a, fed from the reel R1, is redirected by guide roller G1 and passes through the heating furnace H. The temperature inside the heating furnace H is adjusted to be above the melting point of the adhesive layer 14ba and below 120°C. If the adhesive layer 14ba contains EVA as described above, the temperature inside the heating furnace H is adjusted, for example, to be above 100°C and below 120°C. Furthermore, the melting point of EVA is 110°C. The length of the heating furnace H is, for example, set to be above 1m and below 2m. Additionally, the speed at which the heated object 1a moves is, for example, set to be above 1m / min and below 5m / min. The temperature inside the heating furnace H, the length of the heating furnace H, and the speed at which the heated object 1a moves are not particularly limited, as long as the adhesive layer 14ba is heated to above its melting point and below 120°C inside the heating furnace H. The heated object 1a, having passed through the heating furnace H, is redirected by guide roller G2 and wound onto a reel R2. In addition, the cooling zone extends from the heating furnace H to the guide roller G2. The length of the cooling zone is not particularly limited as long as the adhesive layer 14ba can solidify, for example, it can be set to 3m or more.

[0076] In this way, the film 14bt of the outer first sheath layer 14b is bonded to the inner first sheath layer 14a through the adhesive layer 14ba, forming the first sheath layer 14.

[0077] Furthermore, when an adhesive layer is provided on the surface of membrane 14at as described above, and no adhesive layer 14ba is provided on membrane 14bt, the membrane 14bt of the outer first sheath layer 14b is bonded to the inner first sheath layer 14a by the adhesive layer provided on membrane 14at. Alternatively, when an adhesive layer is provided on the surface of membrane 14at, and an adhesive layer 14ba is also provided on membrane 14bt, the membrane 14bt of the outer first sheath layer 14b is bonded to the inner first sheath layer 14a by both the adhesive layer provided on membrane 14at and the adhesive layer 14ba provided on membrane 14bt.

[0078] <Second External Conductor Formation Process P3>

[0079] This process is the process of forming the second outer conductor 15 that surrounds the outer peripheral surface of the first sheath layer 14. If... Figure 1 The second outer conductor 15 shown is, in this process, formed by winding multiple wires into a spiral shape on the outer peripheral surface of the first sheath layer 14. Alternatively, if the second outer conductor 15 is a braided mesh of multiple wires, the multiple wires are braided into the outer peripheral surface of the first sheath layer 14 to form a mesh. In this way, it becomes as shown... Figure 8 The state shown represents the formation of the second outer conductor 15.

[0080] <Second sheath layer formation process P4>

[0081] This process is the process of forming the second sheath layer 16. For example... Figure 3 As shown, this process includes an inner second sheath layer forming process P4a and an outer second sheath layer forming process P4b.

[0082] Process P4a: Formation of the inner second sheath layer

[0083] This process is the process of forming the inner second sheath layer 16a, which covers the outer peripheral surface of the second outer conductor 15 and the film 16at is not adhered to the second outer conductor 15. Figure 9 This is a diagram showing the status of this process. For example... Figure 9 As shown, in this process, a film 16at without an adhesive layer on both sides is prepared, and the film 16at is wound spirally around the outer peripheral surface of the second outer conductor 15. Furthermore, in a manner different from... Figure 9 Instead, if the membrane 16at is wound in a longitudinal winding manner, the membrane 16at is wound in a longitudinal winding manner around the outer peripheral surface of the second outer conductor 15. In this way, the inner second sheath layer 16a is formed.

[0084] Furthermore, if an adhesive layer is provided on the membrane 16at of the inner second sheath layer 16a as described above, the membrane 16at is wound around the outer peripheral surface of the second outer conductor 15 with the adhesive layer facing outward. In this case, the membrane 16at is the part contacted by the adhesive layer.

[0085] Outer Second Sheath Layer Formation Process P4b

[0086] This process involves covering the outer peripheral surface of the inner second sheath layer 16a with the membrane 16bt and bonding it to the inner second sheath layer 16a via an adhesive layer, thereby forming the outer second sheath layer 16b. As described above, the outer second sheath layer 16b is an exposed sheath layer, therefore this process can be understood as an exposed sheath formation process. This process includes the outer second sheath layer winding process P4bw and the outer second sheath layer bonding process P4ba.

[0087] (Outer second sheath layer winding process P4bw)

[0088] This process involves wrapping the film 16bt, which has an adhesive layer 16ba, around the outer periphery of the inner second sheath layer 16a. Figure 10 This is a diagram showing the status of this process. For example... Figure 10 As shown, in this process, a film 16bt with an adhesive layer 16ba is prepared, and the film 16bt is wound spirally onto the outer peripheral surface of the inner second sheath layer 16a in such a way that the adhesive layer 16ba contacts the inner second sheath layer 16a. Furthermore, in a manner different from... Figure 10Instead, when the membrane 16bt is wound longitudinally, the membrane 16bt is wound longitudinally onto the outer peripheral surface of the inner second sheath layer 16a, with the adhesive layer 16ba in contact with the inner second sheath layer 16a. This results in the adhesive layer 16ba being in contact with the inner second sheath layer 16a, and the membrane 16bt being wound onto the outer peripheral surface of the inner second sheath layer 16a. Furthermore, through this process, the membrane 16bt surrounds the outer peripheral surface of the sensor section S via the inner second sheath layer 16a, the second outer conductor 15, and the first sheath layer 14.

[0089] Furthermore, when an adhesive layer is provided on the surface of the membrane 16at as described above, and the membrane 16at is wrapped around the outer peripheral surface of the second outer conductor 15 with the surface of the membrane 16at where the adhesive layer is provided being the outer side, the membrane 16bt without the adhesive layer 16ba can also be wrapped around the outer peripheral surface of the inner second sheath layer 16a via the adhesive layer on the membrane 16at, or the membrane 16bt with the adhesive layer 16ba can be wrapped around the outer peripheral surface of the inner second sheath layer 16a as described above.

[0090] In this way, the film 16bt, which becomes the outer second sheath layer 16b, is wrapped around the outer peripheral surface of the inner second sheath layer 16a via an adhesive layer.

[0091] (Outer second sheath layer bonding process P4ba)

[0092] This process involves bonding the membrane 16bt of the outer second sheath layer 16b to the inner second sheath layer 16a using the adhesive layer 16ba. In this process, the inner second sheath layer 16a with the membrane 16bt wrapped around it, the second outer conductor 15, the first sheath layer 14, and the sensor part S are heated to below 120°C, thereby bonding the membrane 16bt to the inner second sheath layer 16a using the adhesive layer 16ba. This process in this embodiment is performed similarly. Figure 7 The outer first sheath layer bonding process P2ba is shown. In this case, the heated body 1a consists of an inner second sheath layer 16a with the membrane 16bt wrapped around it, a second outer conductor 15, a first sheath layer 14, and a sensor part S. The heated body 1a is heated in the heating furnace H, and then solidifies the bonding layer 16ba in the heating furnace H, thereby bonding the membrane 16bt to the inner second sheath layer 16a.

[0093] Furthermore, the temperature inside the heating furnace H, the length of the heating furnace H, and the speed at which the heated body 1a moves in this process are not particularly limited as long as the adhesive layer 16ba is heated to 120°C above its melting point inside the heating furnace H. They can also be different from the temperature inside the heating furnace H, the length of the heating furnace H, and the speed at which the heated body 1a moves in the bonding process P2ba of the outer first sheath layer.

[0094] In this way, the film 16bt of the outer second sheath layer 16b is bonded to the inner second sheath layer 16a through the adhesive layer 16ba, thus manufacturing... Figure 1 , Figure 2 The piezoelectric coaxial sensor 1 shown is shown.

[0095] Furthermore, when an adhesive layer is provided on the surface of membrane 16at as described above, and no adhesive layer 16ba is provided on membrane 16bt, the membrane 16bt of the outer second sheath layer 16b is bonded to the inner second sheath layer 16a by the adhesive layer provided on membrane 16at. Alternatively, when an adhesive layer is provided on the surface of membrane 16at, and an adhesive layer 16ba is also provided on membrane 16bt, the membrane 16bt of the outer second sheath layer 16b is bonded to the inner second sheath layer 16a by both the adhesive layer provided on membrane 16at and the adhesive layer 16ba provided on membrane 16bt.

[0096] This manufacturing method includes a sheath layer forming process for forming multiple sheath layers. Specifically, the sheath layer forming process for forming multiple sheath layers includes an inner first sheath layer forming process P2a, an outer first sheath layer forming process P2b, an inner second sheath layer forming process P4a, and an outer second sheath layer forming process P4b.

[0097] As explained above, the manufacturing method of the piezoelectric coaxial sensor 1 in this embodiment includes a preparation step P1 and a sheath layer forming step. The preparation step P1 is a step of preparing the sensor part S, and the sheath layer forming step is a step of forming at least one sheath layer. The sheath layer has a strip-shaped film wound around the outer peripheral surface of the sensor part S. The sheath layer forming step includes an exposed sheath forming step, namely, an outer second sheath layer forming step P4b, which forms an exposed sheath layer in the sheath layer. The outer second sheath layer forming process P4b includes an outer second sheath layer winding process P4bw and an outer second sheath layer bonding process P4ba. The outer second sheath layer winding process P4bw is a process of winding a film 16bt, on which an adhesive layer 16ba made of thermoplastic resin with a melting point of less than 120°C is provided, in a manner that surrounds the outer peripheral surface of the sensor part S. The outer second sheath layer bonding process P4ba is a process of heating the sensor part S on which the film 16bt is wound at less than 120°C, thereby bonding the film 16bt to the part that the adhesive layer 16ba contacts, namely the inner second sheath layer 16a, through the adhesive layer 16ba.

[0098] According to this method of manufacturing piezoelectric coaxial sensor 1, a sheath layer exposed to the outside is formed by heating to below 120°C, thereby enabling the manufacture of a piezoelectric coaxial sensor 1 that can suppress the reduction of PVDF polarization and suppress the deterioration of output characteristics.

[0099] Furthermore, in the manufacturing method of the piezoelectric coaxial sensor 1 in this embodiment, the thermoplastic resin of the adhesive layer 16ba contains ethylene vinyl acetate copolymer, thereby enabling it to become an adhesive layer with a melting point of 120 degrees or less.

[0100] Furthermore, the manufacturing method of the piezoelectric coaxial sensor 1 in this embodiment includes a first sheath layer forming step P2, a second outer conductor forming step P3, and a second sheath layer forming step P4. The first sheath layer forming step P2 is a step of forming a first sheath layer 14, which includes multiple sheath layers and covers the outer peripheral surface of the sensor portion S. The second outer conductor forming step P3 is a step of forming a second outer conductor 15 surrounding the outer peripheral surface of the first sheath layer 14. The second sheath layer forming step P4 is a step of forming a second sheath layer 16, which includes multiple sheath layers and covers the outer peripheral surface of the second outer conductor 15. The outermost sheath layer of the second sheath layer 16, i.e., the outer second sheath layer 16b, is exposed to the outside. In this manufacturing method of the piezoelectric coaxial sensor 1, a piezoelectric coaxial sensor 1 can be manufactured in which the second outer conductor 15 functions as a shielding layer and has excellent noise resistance characteristics, and the outer peripheral surface of the second outer conductor 15, which functions as a shielding layer, is insulated from the outside by the second sheath layer 16.

[0101] Furthermore, in the manufacturing method of the piezoelectric coaxial sensor 1 in this embodiment, the first sheath layer forming process P2 includes an inner first sheath layer forming process P2a for forming an inner first sheath layer 14a and an outer first sheath layer forming process P2b for forming an outer first sheath layer 14b. The inner first sheath layer 14a covers the outer peripheral surface of the sensor portion S and the film 14at is not adhered to the sensor portion S. The outer first sheath layer 14b covers the outer peripheral surface of the inner first sheath layer 14a and the film 14bt is adhered to the inner first sheath layer 14a by the adhesive layer 14ba. The outer first sheath layer forming process P2b... The process includes an outer first sheath layer winding process P2bw and an outer first sheath layer bonding process P2ba. The outer first sheath layer winding process P2bw is a process of winding the film 14bt with the adhesive layer 14ba on the outer peripheral surface of the inner first sheath layer 14a. The outer first sheath layer bonding process P2ba is a process of heating the inner first sheath layer 14a and the sensor part S, which have the film 14bt wound in the outer first sheath layer winding process P2bw, and heating them at a temperature below 120°C, thereby bonding the film 14bt of the outer first sheath layer 14b to the inner first sheath layer 14a through the adhesive layer 14ba. According to this method of manufacturing the piezoelectric coaxial sensor 1, a piezoelectric coaxial sensor 1 can be manufactured in which the inner first sheath layer 14a is not bonded to the sensor portion S, thereby facilitating the extraction of the sensor portion S; and the outer first sheath layer 14b is bonded to the inner first sheath layer 14a, thereby preventing the first sheath layer 14 from dislodging even if the piezoelectric coaxial sensor 1 is bent. Furthermore, according to the manufacturing method of the piezoelectric coaxial sensor 1 of this embodiment, the first sheath layer 14 is formed by heating at a temperature below 120°C, thereby suppressing the reduction of PVDF polarization.

[0102] Furthermore, in the manufacturing method of the piezoelectric coaxial sensor in this embodiment, the second sheath layer forming process P4 includes an inner second sheath layer forming process P4a for forming an inner second sheath layer 16a and an outer second sheath layer forming process P4b for forming an outer second sheath layer 16b. The inner second sheath layer 16a covers the outer peripheral surface of the second outer conductor 15 and the film 16at is not adhered to the second outer conductor 15. The outer second sheath layer 16b is the outermost sheath layer of the second sheath layer 16 and covers the outer peripheral surface of the inner second sheath layer 16a. The film 16bt is adhered to the inner second sheath layer 16a by the adhesive layer 16ba. According to this method of manufacturing the piezoelectric coaxial sensor 1, a piezoelectric coaxial sensor 1 can be manufactured in which the inner second sheath layer 16a is not bonded to the second outer conductor 15, thereby facilitating the lead-out of the second outer conductor 15; and the outer second sheath layer 16b is bonded to the inner second sheath layer 16a, thereby preventing the second sheath layer 16 from dislodging even if the piezoelectric coaxial sensor 1 is bent. Furthermore, as described above, according to the manufacturing method of the piezoelectric coaxial sensor 1 of this embodiment, the second sheath layer 16 is formed by heating at 120°C or below, thereby suppressing the reduction of PVDF polarization.

[0103] The above description uses an example embodiment, but the present invention is not limited to the above embodiment. For example, the second outer conductor 15 and the second sheath layer 16 are not essential structures. When the piezoelectric coaxial sensor 1 does not have the second outer conductor 15 and the second sheath layer 16, the outer first sheath layer 14b of the first sheath layer 14 is an exposed sheath layer. Therefore, in this case, for the outer first sheath layer 14b, the membrane 14bt is bonded to the component contacted by the adhesive layer 14ba through the adhesive layer 14ba. The membrane 14bt is heated to 120°C above the melting point of the adhesive layer 14ba and bonded to the component contacted by the adhesive layer 14ba through the adhesive layer 14ba. In the above example, this component is the inner first sheath layer 14a, but when the inner first sheath layer 14a is omitted, it is the sensor part S. In addition, when the piezoelectric coaxial sensor 1 does not have a second external conductor 15 and a second sheath layer 16, the outer first sheath layer forming process P2b becomes the exposed sheath forming process for forming a sheath layer exposed to the outside.

[0104] Furthermore, if the first sheath layer 14 does not have an inner first sheath layer 14a, the inner first sheath layer forming process P2a is omitted, and the film 14bt of the outer first sheath layer is bonded to the sensor part S by the adhesive layer 14ba. Also, if the first sheath layer 14 does not have an outer first sheath layer 14b, the outer first sheath layer forming process P2b is omitted. In this case, the second sheath layer 16 is a necessary structure.

[0105] Furthermore, if the second sheath layer 16 does not have an inner second sheath layer 16a, the inner second sheath layer forming process P4a is omitted, and the film 16bt of the outer second sheath layer is bonded to the second outer conductor 15 by the adhesive layer 16ba. Moreover, if the piezoelectric coaxial sensor 1 has a second sheath layer 16, the outer second sheath layer 16b is a necessary structure.

[0106] The present invention will be described in more detail below with examples and comparative examples, but the present invention is not limited thereto.

[0107] (Example 1)

[0108] Press and Figure 1 , Figure 2 The piezoelectric coaxial sensor 1 shown has a structure substantially the same as the piezoelectric coaxial sensor 1 shown, and a piezoelectric coaxial sensor with a length of 100 cm is manufactured. First, the sensor part S is prepared in substantially the same way as the preparation step P1 described above. As the center conductor 11, a stranded wire consisting of 7 soft copper wires with a diameter of approximately 0.05 mm and an outer diameter of approximately 0.15 mm is used. The polymer piezoelectric layer 12 and Figure 1 , Figure 2 The difference lies in the arrangement of the PVDF strip film, which is coiled into a spiral structure on the outer periphery of the central conductor 11. The film is wound in such a way that a portion of it overlaps to form two layers. The outer diameter of the polymer piezoelectric layer 12 is 0.3 mm. The first outer conductor 13 is a structure in which multiple tin-plated soft copper alloy wires with a diameter of 0.03 mm are coiled into a spiral structure on the outer periphery of the polymer piezoelectric layer 12. The outer diameter of the first outer conductor 13 is 0.36 mm. In this way, the sensor section S is prepared.

[0109] Next, similarly to the first sheath layer forming step P2 described above, the first sheath layer 14 is formed using an inner first sheath layer 14a and an outer first sheath layer 14b. First, in the inner first sheath layer forming step P2a, the inner first sheath layer 14a is formed. The inner first sheath layer 14a is formed by spirally winding a film 14at made of polyethylene terephthalate (PET) onto the outer peripheral surface of the first outer conductor 13. At this time, the film 14at is wound in such a way that a portion of the film 14at overlaps to form two layers. The outer diameter of the inner first sheath layer 14a is 0.38 mm. Next, similarly to the outer first sheath layer forming step P2b, the outer first sheath layer 14b is formed. Similar to the outer first sheath layer winding step P2bw, the outer first sheath layer 14b is formed by spirally winding a film 14bt made of PET with an adhesive layer 14b on one side onto the outer peripheral surface of the inner first sheath layer 14a. At this time, the film 14bt is wound in a manner that overlaps a portion of the film 14bt into two layers. The outer diameter of the outer first sheath layer 14b is 0.39 mm. Furthermore, the adhesive layer 14ba is made of a thermoplastic resin containing EVA. Subsequently, similar to the outer first sheath layer bonding process P2ba, the film 14bt of the outer first sheath layer 14bt is bonded to the inner first sheath layer 14a through the adhesive layer 14ba. At this time, the set temperature of the heating furnace H is 120°C, the length of the heating furnace is 1.1 m, and the linear velocity of the heated body 1a is 3 m / min.

[0110] Next, the second outer conductor 15 is formed through the second outer conductor forming process P3. The second outer conductor 15 is a structure in which multiple tin-plated soft copper alloy wires with a diameter of 0.03 mm are coiled in a spiral shape on the outer peripheral surface of the first sheath layer 14. The outer diameter of the second outer conductor 15 is 0.45 mm.

[0111] Next, similarly to the second sheath layer forming step P4 described above, the second sheath layer 16 is formed using an inner second sheath layer 16a and an outer second sheath layer 16b. First, in the inner second sheath layer forming step P4a, the inner second sheath layer 16a is formed. The inner second sheath layer 16a is formed by spirally winding a PET film 16at onto the outer peripheral surface of the second outer conductor 15. At this time, the film 16at is wound in such a way that a portion of the film 16at overlaps to form two layers. The outer diameter of the inner second sheath layer 16a is 0.47 mm. Next, similarly to the outer second sheath layer forming step P4b, the outer second sheath layer 16b is formed. Similar to the outer second sheath layer winding step P4bw, the outer second sheath layer 16b is formed by spirally winding a PET film 16bt, on one side of which has an adhesive layer 16ba, onto the outer peripheral surface of the inner second sheath layer 16a. At this point, the film 16bt is wound in a manner that overlaps a portion of the film 16bt into two layers. The outer diameter of the outer second sheath layer 16b is 0.54 mm. Furthermore, the adhesive layer 16ba is composed of a thermoplastic resin containing EVA. Subsequently, similar to the outer second sheath layer bonding process P4ba, the film 16bt of the outer second sheath layer 16bt is bonded to the inner second sheath layer 16a through the adhesive layer 16ba. At this time, the set temperature of the heating furnace H is 120°C, the length of the heating furnace is 1.1 m, and the linear velocity of the heated body 1a is 3 m / min.

[0112] (Comparative Example 1)

[0113] Except for the adhesive layers 14ba of the outer first sheath layer 14b and 16ba of the outer second sheath layer 16b, which are both made of acrylic thermoplastic resin, a piezoelectric coaxial sensor was manufactured in the same manner as in Example 1. The melting point of the thermoplastic resin is 130°C.

[0114] (Comparative Example 2)

[0115] Except for the adhesive layers 14ba of the outer first sheath layer 14b and 16ba of the outer second sheath layer 16b, which are made of polyester thermoplastic resin, and the setting temperature of the heating furnace H in the bonding processes P2ba and P4ba of the outer first sheath layer is set to 150°C, a piezoelectric coaxial sensor is manufactured in the same manner as in Example 1. The melting point of this thermoplastic resin is 140°C.

[0116] (Comparative Example 3)

[0117] Except for the adhesive layers 14ba of the outer first sheath layer 14b and 16ba of the outer second sheath layer 16b, which are made of polyamide thermoplastic resin, and the setting temperature of the heating furnace H in the bonding processes P2ba and P4ba of the outer first sheath layer is set to 160°C, a piezoelectric coaxial sensor is manufactured in the same manner as in Example 1. The melting point of this thermoplastic resin is 150°C.

[0118] The outer second sheath layer 16b of Example 1 is bonded with sufficient strength and cannot be easily peeled off.

[0119] In Comparative Example 1, the outer second sheath layer 16b was not bonded with sufficient strength, and it was easily peeled off. Furthermore, even when the set temperature of the heating furnace H in the outer first sheath layer bonding process P2ba and the outer second sheath layer bonding process P4ba of Comparative Example 1 was increased to 170°C, the same result was achieved.

[0120] In Comparative Example 2, the outer second sheath layer 16b was bonded with sufficient strength and could not be easily peeled off. Furthermore, when the temperature of the heating furnace H in the outer first sheath layer bonding process P2ba and the outer second sheath layer bonding process P4ba of Comparative Example 2 was set to 120°C, the films 14bt and 16bt were not bonded.

[0121] In Comparative Example 3, the outer second sheath layer 16b was bonded with sufficient strength and could not be easily peeled off. Furthermore, when the heating furnace H in the outer first sheath layer bonding process P2ba and the outer second sheath layer bonding process P4ba of Comparative Example 3 was set to 120°C, the films 14bt and 16bt were not bonded.

[0122] Next, an external force of 10N was applied from the side to the piezoelectric coaxial sensors of Examples 1 and Comparative Examples 1-3, extending 10 mm in length. The voltage generated between the central conductor 11 and the first outer conductor 13 was increased by 20 times and measured. As a result, the voltage generated by the piezoelectric coaxial sensors of Examples 1 and Comparative Examples 1-3 was 180 mV for Examples 1 and Comparative Example 1, 50 mV for Comparative Example 2, and 10 mV for Comparative Example 3.

[0123] Next, by changing the set temperature of the heating furnace H in the outer first sheath layer bonding process P2ba and the outer second sheath layer bonding process P4ba, a piezoelectric coaxial sensor with the same structure as in Example 1 was manufactured. Next, an external force of 10N was applied from the side along a 10mm length to each manufactured piezoelectric coaxial sensor, increasing the voltage between the central conductor 11 and the first outer conductor 13 by 20 times, and this was measured. Figure 11 The result is shown in the figure.

[0124] Figure 11 This is a graph showing the relationship between the measured voltage of the piezoelectric coaxial sensor and the set temperature of the heating furnace H being varied to 100℃, 110℃, 120℃, 130℃, and 140℃. (Example) Figure 11 As shown, if the set temperature of the heating furnace is below 120℃, then the voltage is sufficiently high.

[0125] As described above, the piezoelectric coaxial sensor manufacturing method according to the present invention can manufacture a piezoelectric coaxial sensor that suppresses the deterioration of output characteristics. The piezoelectric coaxial sensor of the present invention can be manufactured by heating at a temperature below 120°C, thereby becoming a piezoelectric coaxial sensor that suppresses the deterioration of output characteristics.

[0126] As described above, according to the present invention, a piezoelectric coaxial sensor that suppresses the deterioration of output characteristics and a method for manufacturing the piezoelectric coaxial sensor are provided, which are expected to be used in fields such as device measurement.

Claims

1. A piezoelectric coaxial sensor, characterized in that, have: The sensor unit has a linear central conductor, a polymer piezoelectric layer containing polyvinylidene fluoride covering the outer peripheral surface of the central conductor, and a first external conductor surrounding the outer peripheral surface of the polymer piezoelectric layer. The first sheath layer includes one or more sheath layers and covers the outer peripheral surface of the sensor portion, the sheath layer having a strip-shaped film wound around the outer peripheral surface of the sensor portion; The second outer conductor surrounds the outer peripheral surface of the first sheath layer; as well as The second sheath layer includes one or more of the sheath layers and covers the outer peripheral surface of the second outer conductor. The outermost sheath layer of the second sheath layer is the sheath layer exposed to the outside, and the film of the sheath layer is bonded to the component in contact with the adhesive layer by an adhesive layer made of a thermoplastic resin with a melting point below 120°C.

2. The piezoelectric coaxial sensor according to claim 1, characterized in that, The thermoplastic resin comprises an ethylene vinyl acetate copolymer.

3. The piezoelectric coaxial sensor according to claim 1 or 2, characterized in that, The first sheath layer has: an inner first sheath layer that covers the outer peripheral surface of the sensor portion, wherein the film of the inner first sheath layer is not adhered to the sensor portion; and an outer first sheath layer that covers the outer peripheral surface of the inner first sheath layer, wherein the film of the outer first sheath layer is adhered to the inner first sheath layer by the adhesive layer.

4. The piezoelectric coaxial sensor according to claim 1 or 2, characterized in that, The second sheath layer has: an inner second sheath layer that covers the outer peripheral surface of the second outer conductor, wherein the film of the inner second sheath layer is not adhered to the second outer conductor; and an outer second sheath layer that is the outermost sheath layer of the second sheath layer and covers the outer peripheral surface of the inner second sheath layer, wherein the film of the outer second sheath layer is adhered to the inner second sheath layer by the adhesive layer.

5. A method for manufacturing a piezoelectric coaxial sensor, characterized in that, have: The preparation process includes preparing a sensor unit, which has a linear central conductor, a polymer piezoelectric layer containing polyvinylidene fluoride covering the outer peripheral surface of the central conductor, and a first external conductor surrounding the outer peripheral surface of the polymer piezoelectric layer. The first sheath layer forming process forms a first sheath layer including one or more sheath layers and covering the outer peripheral surface of the sensor part, wherein the sheath layer has a strip-shaped film wound around the outer peripheral surface of the sensor part. The second outer conductor forming process forms a second outer conductor that surrounds the outer peripheral surface of the first sheath layer; as well as The second sheath layer forming process involves forming a second sheath layer that includes one or more of the aforementioned sheath layers and covers the outer peripheral surface of the second outer conductor. The outermost sheath layer of the second sheath layer is the sheath layer exposed to the outside. The second sheath layer forming process includes an exposed sheath forming process for forming the sheath layer that is exposed to the outside. The exposed sheath forming process includes: The winding process involves wrapping the film of the sheath layer, which will be exposed to the outside, around the outer peripheral surface of the sensor portion via an adhesive layer made of a thermoplastic resin with a melting point below 120°C, around the outer peripheral surface of the component in contact with the adhesive layer; and In the bonding process, the sensor portion, to which the sheath layer is wrapped and exposed to the outside is heated to below 120°C, thereby bonding the membrane to the component through the adhesive layer.

6. The method for manufacturing a piezoelectric coaxial sensor according to claim 5, characterized in that, The thermoplastic resin comprises an ethylene vinyl acetate copolymer.

7. The method for manufacturing a piezoelectric coaxial sensor according to claim 5 or 6, characterized in that, The first sheath layer forming process includes: an inner first sheath layer forming process, forming an inner first sheath layer that covers the outer peripheral surface of the sensor portion, wherein the film of the inner first sheath layer is not adhered to the sensor portion; and an outer first sheath layer forming process, forming an outer first sheath layer that covers the outer peripheral surface of the inner first sheath layer, wherein the film of the outer first sheath layer is adhered to the inner first sheath layer by the adhesive layer. The process for forming the outer first sheath layer includes: The outer first sheath layer winding process involves wrapping the film of the outer first sheath layer around the outer peripheral surface of the inner first sheath layer via the adhesive layer; and In the outer first sheath layer bonding process, the inner first sheath layer and the sensor part, which have been wound into the film that becomes the outer first sheath layer in the outer first sheath layer winding process, are heated to below 120°C, thereby bonding the film that will become the outer first sheath layer to the inner first sheath layer through the bonding layer.

8. The method for manufacturing a piezoelectric coaxial sensor according to claim 5 or 6, characterized in that, The second sheath layer forming process includes: an inner second sheath layer forming process, forming an inner second sheath layer that covers the outer peripheral surface of the second outer conductor, wherein the film of the inner second sheath layer is not adhered to the second outer conductor; and an outer second sheath layer forming process, forming an outer second sheath layer, which is the outermost sheath layer of the second sheath layer and covers the outer peripheral surface of the inner second sheath layer, wherein the film of the outer second sheath layer is adhered to the inner second sheath layer by the adhesive layer. The outer second sheath layer forming process is the exposed sheath forming process.

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