Cable inspection method and cable inspection device

Abstract

To provide a cable inspection technique that enables relatively easy inspection of a sheath that covers the surroundings of an electric wire.SOLUTION: A cable inspection device 200 for inspecting a cable having at least one electric wire 20 and a sheath 30 covering the surroundings of the electric wire 20, includes: a characteristic detection unit 210 that is installed in a cooling tank 140 in which cooling water for cooling the sheath 30 formed in the surroundings of the electric wire 20 by an extruder 130 is stored, and continuously detects electrical characteristics of the cable 10 passing through the cooling water; and a determination unit 230 that determines the presence or absence of a defect in the sheath as an inspection of the cable 10 based on the electrical characteristics of the cable detected by the characteristic detection unit 210.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cable inspection method and a cable inspection device for inspecting a cable, particularly for inspecting a sheath. [Background technology]

[0002] Conventionally, one of the inspections of a cable having a sheath that covers the electric wire is to inspect the sheath (see Patent Document 1). Patent Document 1 describes the use of a spark tester to inspect defects in the electric wire coating (corresponding to the sheath). The spark tester uses sparks to inspect the electric wire coating for defects, and can output a defect detection signal if, for example, a pinhole or a scar is present in the electric wire coating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-187905 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, for example, when the sheath is thin or when the surface material of the electric wire inside the sheath is an insulator, there is a risk that defects such as minute through holes (pinholes) that occur in the sheath cannot be detected by the inspection using a spark tester. For this reason, even when an inspection is performed using a spark tester, it is necessary to also perform visual inspection by an operator, which takes time to inspect the cable. Furthermore, even when an operator performs visual inspection, there is a risk that defects in the sheath such as pinholes will be overlooked.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a cable inspection technique that can easily inspect the sheath that covers the electric wire. [Means for solving the problem]

[0006] One aspect of the present disclosure is a cable inspection method for inspecting a cable having at least one electric wire and a sheath covering the electric wire, the cable inspection method including a characteristic detection step of continuously detecting electrical characteristics of the cable passing through cooling water when the sheath formed around the electric wire by extrusion molding is cooled with the cooling water, and a determination step of determining whether or not there is a defect in the sheath based on the electrical characteristics of the cable detected in the characteristic detection step.

[0007] Another aspect of the present disclosure is a cable inspection device that inspects a cable having at least one electric wire and a sheath covering the electric wire, the cable inspection device being installed in a cooling tank that stores cooling water for cooling the sheath formed around the electric wire by an extruder, and including: a characteristic detection unit that continuously detects electrical characteristics of the cable passing through the cooling water; and a determination unit that determines whether or not there is a defect in the sheath as an inspection of the cable based on the electrical characteristics of the cable detected by the characteristic detection unit. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a cable inspection technique that can easily inspect the sheath of a cable. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an example of a cable to be inspected by a cable inspection apparatus according to an embodiment; [Diagram 2] 1 is a diagram showing an overall configuration of a cable manufacturing apparatus including a cable inspection apparatus according to an embodiment; [Diagram 3] 1 is a diagram showing an example of a detection result of electrical characteristics of a cable by a cable inspection device according to an embodiment. FIG. [Figure 4] 11 is a cross-sectional view showing another example of a cable to be inspected by the cable inspection apparatus according to the embodiment. FIG. [Diagram 5]11 is a cross-sectional view showing another example of a cable to be inspected by the cable inspection apparatus according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used to designate members having the same functions, and in principle, repeated description will not be given.

[0011] (Cable configuration) Fig. 1 is a cross-sectional view showing an example of a cable to be inspected by a cable inspection device of an embodiment. As shown in Fig. 1, the cable 10 to be inspected has at least one electric wire 20 (two in this example) and a sheath 30 that covers the two electric wires 20. As an example, the outer diameter of each electric wire 20 is about 1.0 mm, and the outer diameter of the sheath 30, i.e., the outer diameter of the cable 10, is about 2.2 mm.

[0012] Each of these electric wires 20 is a so-called insulated electric wire, and is composed of a core wire 21, which is a conductor, and an insulating layer 22 covering the outer periphery of the core wire 21. The core wire 21 may be any commonly used metal wire, such as a copper wire, a copper alloy wire, an aluminum wire, a gold wire, or a silver wire. The core wire 21 may also be a metal wire with a metal plating such as nickel applied around it. Furthermore, the core wire 21 may be a twisted conductor in which metal wires are twisted together. The material of the insulating layer 22 may be any commonly used insulating material, such as polyvinyl chloride, fluororesin, cross-linked polyethylene, natural rubber, synthetic rubber, etc.

[0013] The sheath 30 is provided to protect the electric wires 20, and is made of an electrically insulating resin material such as polyethylene, polyvinyl chloride, etc. In the cable 10 shown in Fig. 1, no filler is filled between each electric wire 20 and the sheath 30, and the portion of the sheath 30 other than the electric wires 20 is left as a space.

[0014] Further, although the cable 10 is illustrated as including a plurality of electric wires 20, the cable 10 may include a single electric wire 20.

[0015] (Overall configuration of cable manufacturing equipment) Fig. 2 is a schematic diagram showing the overall configuration of a cable manufacturing apparatus including a cable inspection apparatus according to one embodiment. The cable manufacturing apparatus 100 shown in Fig. 2 is an apparatus for manufacturing the cable 10 shown in Fig. 1, and includes a let-off machine 110, a let-off accumulator 120, an extruder 130, a cooling tank 140, a take-up machine 150, a winding accumulator 160, and a winding machine 170, and further includes a cable inspection apparatus 200. Note that the configuration of the cable manufacturing apparatus 100 is an existing one except for the cable inspection apparatus 200, and therefore these existing configurations will be briefly described.

[0016] The feed machine 110 supports a holding member 111 such as a bobbin around which each electric wire 20 is wound, and feeds each electric wire 20 from the holding member 111. The feed accumulator 120 stores a predetermined length of each electric wire 20 fed by the feed machine 110. The feed accumulator 120 is configured to be able to appropriately change the length of the stored electric wire 20.

[0017] The extruder 130 forms a sheath 30 (see FIG. 1) around the two electric wires 20 that are supplied by extrusion molding. More specifically, in the extruder 130, when the two electric wires 20 pass through a crosshead, a sheath raw material, which is a resin material, is discharged in a molten state onto the outer periphery of the two electric wires 20, and the discharged sheath raw material is formed with a substantially uniform thickness around the two electric wires 20. That is, the sheath 30 is formed around the two electric wires 20.

[0018] Cooling water is stored in the cooling tank 140 for cooling the sheath 30 formed by extrusion around the electric wire 20. The cable 10 passes through this cooling water at a predetermined speed, whereby the sheath 30 extruded by the extruder 130 is cooled and hardened.

[0019] The take-up machine 150 is disposed downstream of the cooling tank 140, and takes up the cable 10 that has passed through the cooling tank 140 during the production of the cable 10. That is, the take-up machine 150 pulls the cable 10 that has passed through the cooling tank 140 to the downstream side of the cooling tank 140. As a result, the cable 10 is sent to the winding machine 170 via the winding accumulator 160.

[0020] The winding accumulator 160 stores a predetermined length of the cable 10 sent from the take-up machine 150. The winding accumulator 160 is configured to be able to change the length of the stored cable 10 as appropriate. The winding machine 170 supports a holding member 171 such as a bobbin for winding up the cable 10, and winds the cable 10 around the holding member 171. Note that, although not shown, various inspection devices for inspecting the cable 10 may be disposed between the winding accumulator 160 and the winding machine 170. Examples of the inspection devices include a spark tester and an unevenness detector.

[0021] The cable 10 shown in Fig. 1 is manufactured by the cable manufacturing apparatus 100 configured as described above. In other words, the cable 10 is manufactured in the following procedure. First, the two electric wires 20 are each unwound from the holding member 111, and each of the unwound electric wires 20 is supplied to the extruder 130 at a predetermined linear speed via the feed accumulator 120. The extruder 130 ejects sheath raw material, and the sheath 30 is extruded around the two electric wires 20. Then, the cable 10 passes through cooling water stored in a cooling tank 140, whereby the sheath 30 formed around the electric wires 20 is cooled and solidified.

[0022] Through such a procedure, a cable 10 is continuously manufactured, which includes two electric wires 20 and a sheath 30 covering the two electric wires 20. Then, the manufactured cable 10 is passed through a take-up machine 150 and a winding accumulator 160, and is finally wound around a holding member 171 supported by a winding machine 170 and collected.

[0023] (Cable inspection equipment) In addition to the above configuration, the cable manufacturing apparatus 100 according to one embodiment further includes a cable inspection apparatus 200. The cable inspection apparatus 200 continuously detects the electrical characteristics of the cable 10 in cooling water and determines the presence or absence of defects in the sheath 30 that covers the electric wires 20, specifically, the presence or absence of minute through holes (pinholes) penetrating the sheath 30, based on the detection results.

[0024] More specifically, when the sheath 30 formed around the electric wire 20 by extrusion molding is cooled with cooling water, the cable inspection device 200 executes a characteristic detection process of continuously detecting the electrical characteristics of the cable 10 passing through the cooling water, and a judgment process of judging whether or not there is a defect in the sheath 30 based on the electrical characteristics of the cable 10 detected in the characteristic detection process.

[0025] As an example, the cable inspection device 200 includes a characteristic detection unit 210 and a processing device 220. The characteristic detection unit 210 is configured with a device capable of continuously detecting the electrical characteristics of the cable 10 underwater. The characteristic detection unit (characteristic detector) 210 is installed in a cooling tank 140 in which cooling water for cooling the sheath 30 formed around the electric wire 20 by the extruder 130 is stored, and continuously detects the electrical characteristics of the cable 10 passing through the cooling water. In this example, the characteristic detection unit 210 detects the capacitance of the cable 10 as the electrical characteristic of the cable 10. The characteristic detection unit 210 may be configured to continuously detect the electrical capacitance of the cable 10, such as the electrostatic capacitance, and an existing detector may be used. In this example, a capacitance monitor (electrostatic capacitance detector) manufactured by Takikawa Engineering Co., Ltd. is adopted as the characteristic detection unit 210.

[0026] The processing device 220 is configured to include, for example, a CPU (Central Processing Unit), a memory, and the like, and performs various processes based on the detection results of the characteristic detection unit 210. Specifically, the processing device 220 includes at least a determination unit 230 and a storage unit 240.

[0027] As one of the above processes, the determination unit 230 determines whether or not there is a defect in the sheath 30, based on the capacitance of the cable 10 detected by the characteristic detection unit 210. In this example, the determination unit 230 determines whether or not there is a minute through hole (pinhole) penetrating the sheath 30, based on the detection result of the characteristic detection unit 210.

[0028] More specifically, when the capacitance of the cable 10 detected by the characteristic detection unit 210 exceeds a preset threshold, the determination unit 230 determines that a micro through hole has occurred in the sheath 30, that is, determines that "there is a pinhole in the sheath," and transmits an abnormality signal. On the other hand, when the capacitance of the cable 10 is equal to or less than the threshold, the determination unit 230 determines that no micro through hole has occurred in the sheath 30, that is, determines that "there is no pinhole in the sheath."

[0029] When the determination unit 230 transmits an abnormality signal, that is, when it is determined that "there is a pinhole in the sheath", the determination result (details of the abnormality) by the determination unit 230 is stored in the memory unit 240. In this example, the determination result by the determination unit 230 is stored in the memory unit 240 in association with the length of the cable 10 (hereinafter referred to as the cable length) manufactured by the cable manufacturing apparatus 100. In other words, the position where the pinhole occurs in the cable 10 (the position where the determination unit 230 determines that there is a pinhole) is stored in the memory unit 240 as the determination result by the determination unit 230.

[0030] The length of the cable 10 is counted, for example, by a counter 190 included in the cable manufacturing apparatus 100. When the determining unit 230 determines that “a pinhole is present in the sheath”, the processing device 220 obtains the length of the cable 10 at that time from the counter 190 and records the determination result of the determining unit 230 in the memory unit 240 in association with the obtained length of the cable 10.

[0031] The configuration of the processing device 220 other than the determination unit 230 and the storage unit 240 is not particularly limited. For example, the processing device 220 may include a display unit such as a display, and may display the detection result detected by the characteristic detection unit 210 on the display unit as one of the above processes.

[0032] (Determination process by the determination unit) Next, the determination process by the determination section will be described in more detail.

[0033] As described above, when cable 10 is manufactured by cable manufacturing apparatus 100, cable 10 passes through cooling tank 140 at a predetermined linear speed in order to cool extruded sheath 30. A characteristic detection unit 210 of cable inspection apparatus 200 is installed in cooling tank 140, and cable 10 passes through characteristic detection unit 210 at a predetermined linear speed. Then, characteristic detection unit 210 measures the capacitance of cable 10 passing therethrough.

[0034] Here, the inventors of the present invention have discovered the following: If a pinhole occurs in the sheath 30 when the sheath 30 is extruded by the extruder 130, the capacitance of the cable 10 detected by the characteristic detection unit 210 increases locally in the portion of the sheath 30 where the pinhole occurs due to the effect of cooling water entering the inside of the sheath 30 through the pinhole. In other words, if a defect occurs in the sheath 30, the electrical characteristics of the cable 10 detected by the characteristic detection unit 210 vary locally.

[0035] The technology disclosed herein is a novel one based on such findings, and is characterized in that the presence or absence of a defect in the sheath 30 is determined based on the electrical characteristics of the cable 10 detected underwater.

[0036] 3, the capacitance C of the cable 10 detected by the characteristic detection unit 210 varies between a first value C1 and a second value C2 during the period from time T0 to time T1. That is, the capacitance C of the cable 10 is lower than a preset threshold value Cth.

[0037] The capacitance C of the cable 10 rapidly rises beyond the threshold value Cth to a third value C3 after time T1, and remains at the third value C3 until time T2. This third value C3 is higher than the threshold value Cth, and in this example, is the maximum value of the capacitance C that can be detected by the characteristic detection unit 210. In other words, the capacitance C of the cable 10 is actually equal to or greater than the third value C3 from time T1 to time T2.

[0038] The capacitance C of the cable 10 drops sharply to a value lower than the threshold Cth after time T2, and again fluctuates between the first value C1 and the second value C2 during the period from time T2 to time T3. That is, in this example, the capacitance C of the cable 10 is lower than the preset threshold Cth except for the period from time T1 to time T2.

[0039] 3, the determination unit 230 determines that "there is no pinhole in the sheath" for the period from time T0 to time T1, and determines that "there is a pinhole in the sheath" for the period from time T1 to time T2. The determination unit 230 also determines that "there is no pinhole in the sheath" for the period from time T2 to time T3.

[0040] The determination result of the determination unit 230 is stored in the memory unit 240 by the processing device 220, for example, in association with the positions (lengths) of the cable 10 corresponding to time T1 and time T2. The portion of the cable 10 where the defect occurred is then cut off based on the information stored in the memory unit 240. As an example, the cable 10 taken up around the holding member 171 by the winder 170 of the cable manufacturing apparatus 100 is rewound onto another holding member such as a bobbin in a subsequent process. The defective portion of the cable 10, i.e., the portion where a pinhole has occurred in the sheath 30, is cut off and discarded during this rewinding.

[0041] As described above, the electrical characteristics (e.g., capacitance) of the cable 10 are detected by the characteristic detection unit 210 installed in the cooling tank 140, and the cable 10 is inspected based on the detection results of this characteristic detection unit 210, making it possible to easily determine whether or not there is a defect in the sheath 30.

[0042] For example, when the sheath 30 is provided to cover the electric wire 20, which is an insulated electric wire, as in the cable 10 of this example, that is, when the sheath 30 is provided to cover the surface of an insulating layer made of an insulating material, it is difficult to determine the presence or absence of a defect in the sheath 30 using an inspection device such as a spark tester. In contrast, according to the technology disclosed herein, even when the sheath 30 is provided to cover the surface of the insulating layer, the presence or absence of a defect in the sheath 30 can be appropriately determined.

[0043] Furthermore, according to the technology of the present disclosure, it is possible to easily identify the location where a defect has occurred in the sheath 30. Therefore, the defective portion of the cable 10 can be appropriately cut off, and the quality of the cable 10 can be improved.

[0044] Although the cable inspection method and the cable inspection device according to one embodiment have been described above, the cable inspection method and the cable inspection device according to the present disclosure are not limited to the above-described embodiment. It goes without saying that the technology according to the present disclosure can be modified in various ways without departing from the gist of the technology.

[0045] For example, in the above embodiment, an example has been described in which characteristic detection unit 210 of cable inspection apparatus 200 is installed in cooling tank 140 of cable manufacturing apparatus 100, but characteristic detection unit 210 may be installed in a water tank provided separately from cooling tank 140. In other words, in the cable inspection method of the present disclosure, the electrical characteristics of cable 10 may be continuously detected when cable 10 passes through water stored in a water tank separate from cooling tank 140.

[0046] In addition, in the above-described embodiment, the cable inspection device 200 is configured to detect capacitance as an electrical characteristic of the cable 10, but the electrical characteristic of the cable 10 to be detected does not necessarily have to be capacitance and may be, for example, a voltage value, etc.

[0047] The configuration of the cable 10 to be inspected is merely an example and is not limited to the above. For example, the cable 10 (10A) shown in Fig. 4 has a plurality of electric wires 20A (for example, four electric wires) and a covering layer 26 covering the circumference of the plurality of electric wires 20A. The covering layer 26 includes a first tape layer 261 made of a pressure winding tape, an inner sheath 262 made of a resin material, a second tape layer 263 made of a laminate of aluminum or the like, a shield layer 264 made of a braided shield in which a plurality of wires are braided, and an outer sheath 265 made of a resin material. Although not shown in the figure, an inclusion is filled between the electric wires 20A in the first tape layer 261.

[0048] According to the technology of the present disclosure, the cable 10A having such a configuration can be appropriately inspected. For example, when the inner sheath 262 is formed by extrusion molding, by detecting the electrical characteristics of the cable 10A in cooling water as described above, it is possible to easily determine the presence or absence of a defect in the inner sheath 262 based on the detection result.

[0049] The thickness of the inner sheath 262 is, for example, about 0.3 mm, which is very thin. For this reason, it is difficult to determine the presence or absence of defects in the inner sheath 262 using an inspection device such as a spark tester. In contrast, the technology disclosed herein can appropriately determine the presence or absence of defects even in the thin inner sheath 262. Furthermore, the technology disclosed herein can of course determine the presence or absence of defects in the outer sheath 265.

[0050] Furthermore, for example, as shown in FIG. 5, the cable 10 (10B) may be one in which a plurality of cables are arranged in a row and integrated. The cable 10B shown in FIG. 5 has first to fourth cable bodies 11 to 14, each having two electric wires 20 and a sheath 30 covering the electric wires 20, arranged in a row and integrated. The cable manufacturing apparatus 100 may be configured to simultaneously form such first to fourth cable bodies 11 to 14 and integrate the first to fourth cable bodies 11 to 14 to manufacture the cable 10B. According to the technique of the present disclosure, even when the cable 10B having the first to fourth cable bodies 11 to 14 integrated is to be inspected, defects in the sheath 30 can be easily detected. [Explanation of symbols]

[0051] 10, 10A, 10B…cable 11…First cable body 12…Second cable body 13…Third cable body 14…4th cable body 20,20A…Electric wire 21…Core wire 22...Insulating layer 26…Covering layer 261…1st tape layer 262…Inner sheath 263…Second tape layer 264…Shield layer 265…Outer sheath 30…Sheath 100…Cable manufacturing equipment 110...Delivery machine 111...holding member 120…Output accumulator 130…Extruder 140…Cooling tank 150…Removal machine 160…Winding accumulator 170... Winding machine 171... Retaining member 190…Counter 200…Cable inspection equipment 210...characteristic detection unit (characteristic detector) 220... Processing equipment 230...Judgment section 240...Storage section

Claims

1. A cable inspection method for inspecting a cable having at least one electric wire and a sheath surrounding the electric wire, comprising: a characteristic detection step of continuously detecting electrical characteristics of the cable passing through cooling water when the sheath formed around the electric wire by extrusion molding is cooled with the cooling water; and a determination step of determining whether or not the sheath has a defect based on the electrical characteristics of the cable detected in the characteristic detection step. Cable inspection methods.

2. 2. The cable inspection method according to claim 1, In the determination step, when the electrical characteristics of the cable detected in the characteristic detection step exceed a preset threshold value, it is determined that a micro through hole has occurred in the sheath as a defect of the sheath. Cable inspection methods.

3. 2. The cable inspection method according to claim 1, In the characteristic detection step, a capacitance of the cable is detected as an electrical characteristic of the cable. Cable inspection methods.

4. 2. The cable inspection method according to claim 1, The electric wire has a core wire made of a conductor and an insulating layer covering the outer periphery of the core wire. Cable inspection methods.

5. A cable inspection device for inspecting a cable having at least one electric wire and a sheath surrounding the electric wire, comprising: a characteristic detection unit that is installed in a cooling tank that stores cooling water for cooling the sheath formed around the electric wire by an extruder, and that continuously detects the electrical characteristics of the cable passing through the cooling water; and a determination unit that determines whether or not there is a defect in the sheath as an inspection of the cable based on the electrical characteristics of the cable detected by the characteristic detection unit. Cable inspection equipment.

6. 6. The cable inspection device according to claim 5, The determination unit determines that a micro through hole has occurred in the sheath as a defect in the sheath when the electrical characteristic of the cable detected by the characteristic detection unit exceeds a preset threshold value. Cable inspection equipment.

7. 6. The cable inspection device according to claim 5, The characteristic detection unit detects a capacitance of the cable as an electrical characteristic of the cable. Cable inspection equipment.

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