Electric wire, electric wire inspection system and electric wire inspection method

Abstract

To provide an electric wire inspection system and an electric wire inspection method which can detect damage in each electric wire at low cost, even in a case where characteristics among the plurality of electric wires vary, and an electric wire which can be inspected by the electric wire inspection system and the electric wire inspection method.SOLUTION: An electric wire inspection system A has: a storage part A1 for storing response signals for electric wire groups C1 to C3 including a plurality of electric wires obtained by electric wire inspection, for each of the electric wire groups C1 to C3, at a first time point; an inspection part A2 for inspecting a target electric wire C2 selected from the electric wire groups C1 to C3, at a second time point later than the first time point; and an analysis part A3 for calling the response signal at the first time point for the target electric wire C2, from the storage part A1, comparing the called response signal with the response signal acquired by the inspection part A2 at a second time point, when a difference exists between the two response signals, and determining that damage exists in the target electric wire C2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electric wire inspection system, an electric wire inspection method, and an electric wire. [Background technology]

[0002] Electric wires are installed or laid in various electric and electronic devices, transportation equipment, buildings, public facilities, etc., and damage such as breakage, short circuit, and external injury may occur to the electric wires as a result of long-term use. For example, damage may occur to the insulating coating arranged around the electric wire due to contact or friction between the electric wire and surrounding objects. In order to prevent serious effects on the performance of the electric wire caused by the damage, it is desirable to detect the occurrence of damage early and sensitively. Methods for detecting damage to electric wires are disclosed in Patent Documents 1 to 24, etc.

[0003] As a method for detecting damage to an electric wire, for example, Patent Document 11 discloses a cable diagnosis device having a setting means for setting the propagation speed of a pulse electric signal for each of a plurality of sections in a cable route to be diagnosed, and an estimation means for estimating the position of a defective part in the cable route from the measurement results of the reflection characteristics of the pulse electric signal transmitted in the cable route and the propagation speed set for each section. Here, when setting the propagation speed for each section, data such as the number of cables in the cable route is read and set by CAD, and a table showing the relationship between the number of cables and the propagation speed is prepared in advance by experiments, etc., and the propagation speed corresponding to the number of cables in each section of the cable route is automatically set. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-157067 [Patent Document 2] Japanese Patent Application Publication No. 4-326072 [Patent Document 3] Japanese Patent Application Publication No. 6-194401 [Patent Document 4] Japanese Patent Application Publication No. 7-262837 [Patent Document 5] Japanese Patent Application Publication No. 7-282644 [Patent Document 6] Japanese Patent Application Publication No. 8-184626 [Patent Document 7] Japanese Patent Application Publication No. 11-332086 [Patent Document 8] JP 2001-14177 A [Patent Document 9] Special Publication No. 2006-518030 [Patent Document 10] JP 2007-305478 A [Patent Document 11] JP 2007-333468 A [Patent Document 12] JP 2001-141770 A [Patent Document 13] JP 2010-21049 A [Patent Document 14] JP 2011-217340 A [Patent Document 15] JP 2017-142961 A [Patent Document 16] JP 2019-128215 A [Patent Document 17] JP 2019-190875 A [Patent Document 18] JP 2020-15176 A [Patent Document 19] U.S. Pat. No. 4,988,949 [Patent Document 20] U.S. Patent No. 6,265,880 [Patent Document 21] US Patent Application Publication No. 2003 / 206111 [Patent Document 22] US Patent Application Publication No. 2007 / 021941 [Patent Document 23] US Patent Application Publication No. 2010 / 253364 [Patent Document 24] US Patent Application Publication No. 2011 / 309845 Summary of the Invention [Problem to be solved by the invention]

[0005] When inputting an inspection signal to a component of an electric wire, and judging whether or not damage has occurred and identifying the location of the damage based on the obtained response signal, it is necessary to compare the response signal with that when no damage exists and perform calculations taking into account the characteristics of the electric wire. In this case, basic information obtained based on previous tests and theories is used as the response signal to be compared and the electric wire characteristics to be used as the basis for calculations. When a large number of devices of the same type are manufactured, as typified by automobiles, and a large number of electric wires of the same type are also manufactured to be installed in the devices, it is common to apply common basic information to each individual electric wire of the same type as the basic information used to detect damage, such as the table showing the relationship between the number of cables and the propagation speed in the example of Patent Document 11 described above.

[0006] However, even for the same type of electric wire, there is variation in characteristics for each individual wire within the manufacturing tolerance, and there is a possibility that damage cannot be accurately detected by an inspection using common basic information. In particular, when the damage to the electric wire is an external injury limited to the surface portion, which causes only a small change in the response signal, or when the electric wire has a structure, such as a branch portion, that affects the response signal and the change in the response signal due to the damage is difficult to clearly recognize due to the signal originating from the structure, it becomes difficult to detect damage using basic information.

[0007] In addition to the method of using comparisons and calculations using basic information, another method of detecting damage to an electric wire is to keep a measuring device connected to the electric wire at all times and continuously detect the response signal. By continuously monitoring whether there is any change in the response signal over time, any damage to the electric wire can be immediately detected by the change in the response signal. Since the change in the response signal of each individual is monitored over time, even if there is variation in the characteristics of each individual electric wire, the occurrence of damage in each individual can be detected sensitively without being affected by this. However, in this case, it is necessary to provide a measuring device for each individual electric wire, which is not economically rational.

[0008] In view of the above, an object of the present invention is to provide an electric wire inspection system and an electric wire inspection method that can detect damage in a plurality of electric wires at low cost even when there is variation in characteristics between the electric wires, and an electric wire that can be inspected using such an electric wire inspection system and an electric wire inspection method. [Means for solving the problem]

[0009] An electric wire inspection system according to the present disclosure is an electric wire inspection system for inspecting a damage state of an electric wire, the electric wire having a core wire having a conductor and an insulating coating, and a damage detection unit configured with at least one of a constituent member of the core wire and a member other than the core wire arranged along the core wire, the damage detection unit inputting an electrical signal or an optical signal as an inspection signal and performing an electric wire inspection to obtain a response signal, the response signal changes depending on a damage state of the electric wire, the electric wire inspection system has: a memory unit that stores, for each individual electric wire, the response signal obtained by the electric wire inspection for a group of electric wires including a plurality of the electric wires at a first time point; an inspection unit that performs the electric wire inspection on a target electric wire selected from the group of electric wires at a second time point after the first time point; and an analysis unit that calls up the response signal at the first time point for the target electric wire from the memory unit and compares it with the response signal obtained by the inspection unit at the second time point and determines that damage is present in the target electric wire when there is a difference between the two response signals.

[0010] The electric wire inspection method according to the present disclosure includes the following steps: using the electric wire inspection system, at the first time point, an initial data acquisition step of performing the electric wire inspection on the electric wires that constitute the group of electric wires and acquiring the response signals; a data storage step of storing the response signals acquired in the initial data acquisition step in the memory unit for each individual electric wire; a measurement step of performing the electric wire inspection on the target electric wire by the inspection unit at the second time point; and an analysis step of retrieving the response signal acquired at the first time point for the target electric wire from the memory unit and comparing it with the response signal acquired in the measurement step at the second time point, and determining that damage has occurred in the target electric wire if there is a difference between the two response signals.

[0011] A first electric wire according to the present disclosure comprises a core wire having a conductor and an insulating coating covering the outer periphery of the conductor and exposed on the surface, and a conductive tape arranged on the outer periphery of the core wire, the conductive tape being wound spirally around the surface of the insulating coating along the axial direction of the core wire, and there are gaps between the spiral turns of the conductive tape that are not occupied by the conductive tape.

[0012] A second electric wire according to the present disclosure comprises a core wire having a conductor and an insulating coating that covers the outer periphery of the conductor and is exposed on the surface, and a laminated tape arranged on the outer periphery of the core wire, the laminated tape having a substrate configured as a tape-shaped insulator or semiconductor, and conductive coating layers formed on both sides of the substrate. Effect of the Invention

[0013] The electric wire inspection system and the electric wire inspection method according to the present disclosure are capable of detecting damage in a plurality of electric wires at low cost even when the characteristics of the electric wires vary among the electric wires. Also, the electric wire according to the present disclosure is an electric wire that can be inspected by the electric wire inspection system and the electric wire inspection method. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of an electric wire inspection system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a flow diagram illustrating a wire inspection method according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a diagram showing an example of an electric wire to be inspected. [Figure 4]Fig. 4 shows examples of response signals obtained by wire inspection of the wire in Fig. 3, where Fig. 4A shows a case where no damage occurs in individual 1, Fig. 4B shows a case where damage occurs in individual 1, and Fig. 4C shows a difference between a case where damage occurs in individual 1 and a case where no damage occurs in individual 1. Fig. 4D shows a comparison of response signals between individual 1 and individual 2 where no damage occurs, and Fig. 4E shows a difference in response signals between individual 1 and individual 2 where no damage occurs. [Diagram 5] FIG. 5 is a perspective view showing a configuration of a conductive tape-wrapped electric wire as the electric wire according to the first embodiment of the present disclosure. [Figure 6] 6A and 6B are cross-sectional views showing a cross section of the conductive tape-wrapped wire of FIG. 5 taken perpendicular to the axial direction, where FIG. 6A shows a case where the conductive tape is not damaged, and FIG. 6B shows a case where the conductive tape is damaged. [Figure 7] 7A and 7B are cross-sectional views showing cross sections perpendicular to the axial direction of an electric wire in which a conductive layer is formed around the entire circumference of a core wire. FIG. 7A shows a case in which the conductive layer is not damaged, while FIG. 7B shows a case in which the conductive layer is damaged. [Figure 8] FIG. 8 is a perspective view showing a state in which a scratch is formed on the outside of the bent portion of the conductive tape-wrapped electric wire of FIG. 5 . [Figure 9] FIG. 9 is a side view showing a core wire having a branch. [Figure 10] FIG. 10 is a schematic diagram for explaining the inspection of the conductive tape-wrapped electric wire. [Figure 11] Fig. 11A is a perspective view showing a configuration of a laminated tape-wrapped electric wire as an electric wire according to a second embodiment of the present disclosure, and Fig. 11B is a cross-sectional view illustrating the laminated structure of the laminated tape. [Figure 12] FIG. 12 is a diagram showing an example of the measurement result of the characteristic impedance when a simulated injury is formed on a linear conductive tape-wrapped electric wire. [Figure 13] FIG. 13 is a diagram showing the measurement results of the characteristic impedance when the position at which an external injury is formed on a straight conductive tape-wrapped electric wire is changed. [Figure 14]14A to 14C are diagrams showing the measurement results of the characteristic impedance measured on a conductive tape-wrapped electric wire having a branch, in which FIG. 14A shows the measurement result when there is no external damage, FIG. 14B shows the measurement result when there is an external damage, and FIG. 14C shows the differential signal. [Figure 15] 15A to 15C are diagrams showing the measurement results of the characteristic impedance of a linear laminated tape-wrapped electric wire, in which Fig. 15A shows the measurement result when there is no external damage, Fig. 15B shows the measurement result when the laminated tape is broken, and Fig. 15C shows the differential signal. [Figure 16] 16A to 16C are diagrams showing the measurement results of the characteristic impedance of a linear laminated tape-wrapped electric wire, in which Fig. 16A shows the measurement result in an undamaged state, Fig. 16B shows the measurement result in a state in which the two conductive layers of the laminated tape are short-circuited, and Fig. 16C shows the differential signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Description of the embodiments of the present disclosure] First, an embodiment of the present disclosure will be described. The electric wire inspection system of the present disclosure is an electric wire inspection system for inspecting a damage state of an electric wire, the electric wire having a core wire having a conductor and an insulating coating, and a damage detection unit configured with at least one of a constituent member of the core wire and a member other than the core wire arranged along the core wire, the damage detection unit inputting an electric signal or an optical signal as an inspection signal and performing an electric wire inspection to obtain a response signal, the response signal changes depending on a damage state of the electric wire, the electric wire inspection system has: a memory unit that stores the response signal obtained by the electric wire inspection for an electric wire group including a plurality of the electric wires at a first time point for each individual electric wire; an inspection unit that performs the electric wire inspection for a target electric wire selected from the group of electric wires at a second time point after the first time point; and an analysis unit that calls up the response signal at the first time point for the target electric wire from the memory unit and compares it with the response signal obtained by the inspection unit at the second time point and determines that damage is present in the target electric wire when there is a difference between the two response signals.

[0016] In the above-mentioned electric wire inspection system, at a first time point, a response signal obtained by an electric wire inspection for an electric wire group including a plurality of electric wires is stored in a storage unit for each individual electric wire, and at a second time point, a response signal obtained by performing an electric wire inspection for a specific target electric wire in the inspection unit is compared in an analysis unit with a response signal at the first time point corresponding to the target electric wire retrieved from the storage unit. Thus, if damage occurs in the target electric wire between the first time point and the second time point, the damage can be detected by detecting a change in the response signal. Since the response signal at the first time point is stored in the storage unit for each individual electric wire, and the response signal at the first time point is retrieved from the storage unit for the target electric wire that was actually inspected at the second time point, even if there is a variation in the response signal for each individual electric wire constituting the electric wire group, the damage detection for each individual electric wire can be performed based on a comparison of the response signal at the first time point and the response signal at the second time point without being affected by the variation. By storing the response signal of each electric wire in the storage unit, it is not necessary to constantly connect a measuring device to each individual electric wire and continue to monitor the response signal. Therefore, damage detection based on changes in the response signals of individual electric wires can be performed at low cost.

[0017] Here, the storage unit may be provided at a location remote from the inspection unit and the analysis unit. By providing the storage unit as an information management server or the like at a location remote from the inspection unit and the analysis unit, the response signals at the first time point for a large number of electric wires can be stored in association with individual electric wires and managed in a centralized manner. Even when inspections are individually performed on a large number of electric wires using inspection units and analysis units provided at various locations, the response signals at the first time point for each individual electric wire can be provided from the storage unit to the analysis unit at each location and used to detect damage.

[0018] The analysis unit may obtain a difference between the response signal at the first time point and the response signal at the second time point, and determine whether or not there is a difference between the two response signals based on the difference. By obtaining the difference between the two response signals, if damage occurs in the target electric wire between the first time point and the second time point, causing a change in the response signal, the change can be detected sensitively. By using the difference, even if the electric wire includes elements that give the response signal a structure such as a branch or a corrugation, the contribution of those elements can be canceled out and the contribution of the damage can be emphasized in the response signal.

[0019] The damage detection unit has two conductive members electrically insulated from each other, and in the electric wire inspection, an electric signal containing an AC component is used as the inspection signal, and the characteristic impedance between the two conductive members is measured as the response signal by a time domain reflection method or a frequency domain reflection method. The analysis unit may correspond a region in which a difference occurs in the response signal between the response signal at the first time point and the response signal at the second time point to a position along the axial direction of the electric wire, and determine that damage has occurred at that position. By measuring the characteristic impedance between the two conductive members included in the electric wire, when damage occurs in the electric wire, a change due to the damage can be detected sensitively. By measuring the characteristic impedance by a time domain reflection method or a frequency domain reflection method, the position where the damage has occurred along the axial direction of the electric wire can be easily and highly accurately specified from information on the region in which the characteristic impedance has changed on the response signal through appropriate calculations, etc. Measurement by the reflection method can be performed simply by connecting a measuring device to one end of the electric wire, so that damage can be easily detected on the spot even in cases where the electric wire cannot be easily removed.

[0020] In this case, the inspection signal is a signal in which components over a continuous frequency range are superimposed with independent intensities for each frequency, and the frequency range includes excluded frequencies in which some frequency components are missing or have discontinuously smaller intensities than the surrounding frequencies, and the electric wire inspection may measure the characteristic impedance between the two conductive members as the response signal by a time domain reflectometry. In this case, damage can be detected by utilizing the advantages of using an inspection signal in which different frequency components are superimposed, such as the ability to directly convert information on the time at which a change in the characteristic impedance is observed into information on the position at which damage is formed on the electric wire, in addition to the advantages of the time domain reflectometry, such as the ability to directly convert information on the time at which a change in the characteristic impedance is observed into information on the position at which damage is formed on the electric wire, and the ability to reduce the influence of external noise and measure the characteristic impedance. In particular, by having some frequency components missing or low intensities in the continuous frequency range of the inspection signal, the influence of noise in the frequency components can be effectively reduced.

[0021] Furthermore, in the inspection signal, the excluded frequency may include a frequency of an electromagnetic wave originating from a source outside the target electric wire and propagating around the target electric wire. In this case, when the target electric wire is used in an environment where other communication devices or communication electric wires are present nearby, such as inside an automobile, the frequency used for communication with the nearby devices or wires may be set as an excluded frequency to set the waveform of the inspection signal, thereby making it possible to measure the characteristic impedance using the inspection signal and detect damage based on the measurement result while reducing the influence of noise associated with communication in the nearby devices or wires.

[0022] The group of electric wires may include a plurality of electric wires of the same type. If the electric wires are of the same type, even if there is no significant difference between individual response signals when an electric wire inspection is performed, there is variation within the range of manufacturing tolerance. Therefore, by identifying the individual and storing the response signals obtained for each individual at a first point in time in a storage unit, it becomes possible to perform sensitive and highly accurate damage detection based on a comparison of the response signals for a specific individual subjected to an electric wire inspection at a second point in time.

[0023] The electric wires constituting the electric wire group may have a branch part in the middle. When an electric wire has a branch part, the branch part often causes a large change in the behavior of the inspection signal and the response signal, and the change in the response signal due to damage is likely to be hidden. However, by calling up the response signal acquired at a first time point for the target electric wire and comparing it with the response signal acquired at a second time point, it becomes easier to accurately detect damage even if there is a contribution of a signal component originating from the branch part or the like.

[0024] The electric wire to be inspected has a conductive tape wound in a spiral shape around the outer periphery of the core wire, and has gaps between the turns of the conductive tape that are not occupied by the conductive tape, and the damage detection unit is composed of the conductor of the core wire and the conductive tape, and in the electric wire inspection, an electric signal containing an AC component is used as the inspection signal, and the characteristic impedance between the conductor and the conductive tape is measured as the response signal. In this case, when an external injury occurs to the electric wire and damage is also formed in the conductive tape, the characteristic impedance between the conductive tape and the conductor constituting the core wire changes. Since the conductive tape is wound in a spiral shape leaving gaps between the turns, even if damage occurs only in a partial area along the circumferential direction of the electric wire, the electrostatic capacitance between the conductive tape and the conductor constituting the core wire changes significantly. As a result, a large change can occur in the characteristic impedance between the conductive tape and the conductor of the core wire. Therefore, by measuring the characteristic impedance between the conductive tape and the conductor of the core wire, it is possible to sensitively detect the formation of damage in the electric wire.

[0025] In this case, the core wire may have a single-wire structure including only one insulated wire with the insulating coating provided around the conductor. In the case of a core wire with a single-wire structure, unlike a shielded cable or a pair cable, the core wire does not have a plurality of conductive members capable of measuring the characteristic impedance inside, and the characteristic impedance inside the core wire cannot be measured and used for damage detection. However, even if the core wire has a single-wire structure, damage detection based on the characteristic impedance can be performed by wrapping a conductive tape around the core wire. In this case, the conductor of the core wire itself is used as the damage detection unit, so that a simple configuration of just wrapping a conductive tape around the core wire is sufficient as a member dedicated to damage detection.

[0026] Alternatively, the electric wire to be inspected has a laminated tape arranged around the outer periphery of the core wire, the laminated tape being a base material configured as a tape-shaped insulator or semiconductor with conductive coating layers formed on both sides thereof, the damage detection unit being composed of the two coating layers of the laminated tape, and the electric wire inspection may use an electric signal containing an AC component as the inspection signal and measure the characteristic impedance between the two coating layers as the response signal. In this case, when an external injury occurs to the electric wire and damage such as breakage of the coating layer or short circuit between the coating layers is formed in the laminated tape, the characteristic impedance between the two coating layers changes. Therefore, by measuring the change in the characteristic impedance between the two coating layers, it is possible to sensitively detect the occurrence of damage to the electric wire. Since the measurement is performed between the two coating layers provided on the laminated tape, it is possible to impart a damage detection function to various types of electric wires simply by wrapping the laminated tape around them.

[0027] In this case, it is preferable that the core wires are bundled together to form a wire harness, and the laminated tape is spirally wound around the outer periphery of the entire wire harness. In this way, the formation of damage to the outer periphery of the entire wire harness can be sensitively detected using the laminated tape, regardless of the configuration of the wire harness, such as its shape or thickness.

[0028] The electrical characteristics of the substrate may be changed depending on the external environment. In this case, the characteristic impedance between the two coating layers may change due to the change in the electrical characteristics of the substrate caused by the change in the external environment such as the external temperature or humidity. This makes it possible to detect not only physical damage but also the effect of the change in the external environment such as the temperature or humidity on the electric wire.

[0029] The electric wire inspection method of the present disclosure includes the following steps: using the electric wire inspection system, an initial data acquisition step of performing the electric wire inspection on the electric wires that constitute the group of electric wires at the first time point and acquiring the response signals; a data storage step of storing the response signals acquired in the initial data acquisition step in the memory unit for each individual electric wire; a measurement step of performing the electric wire inspection on the target electric wire by the inspection unit at the second time point; and an analysis step of retrieving the response signal acquired at the first time point for the target electric wire from the memory unit and comparing it with the response signal acquired in the measurement step at the second time point, and determining that damage has occurred in the target electric wire if there is a difference between the two response signals.

[0030] In the above-mentioned electric wire inspection method, in the initial data acquisition step and the data storage step, each electric wire constituting the electric wire group is identified, and a response signal obtained by the electric wire inspection is stored in the storage unit. Then, in the inspection step, an electric wire inspection is performed on a specific target electric wire, and in the analysis step, the response signal corresponding to the target electric wire is called from the storage unit and the response signal at the first time point and the second time point are compared. Therefore, if damage occurs in the target electric wire between the first time point and the second time point, the damage can be detected by detecting a change in the response signal. Even if there is a variation in the response signal for each individual electric wire constituting the electric wire group, the damage in each individual can be detected based on a comparison of the response signal at the first time point and the second time point without being affected by the variation, and the damage can be detected sensitively and with high accuracy. Since there is no need to constantly connect a measuring device to each individual electric wire and continuously monitor the response signal, this is an inspection method that can detect damage based on a change in the response signal for each individual at low cost.

[0031] The first electric wire of the present disclosure comprises a core wire having a conductor and an insulating coating that covers the outer periphery of the conductor and is exposed on the surface, and a conductive tape arranged on the outer periphery of the core wire, the conductive tape being wound spirally around the surface of the insulating coating along the axial direction of the core wire, and there are gaps between the spiral turns of the conductive tape that are not occupied by the conductive tape.

[0032] The first electric wire has a conductive tape wound around the outer periphery of the core wire, and when the conductive tape is damaged, the characteristic impedance between the conductive tape and the conductor constituting the core wire changes. As a member for detecting external damage, a conductive material is not continuously coated around the entire circumference of the core wire, but the conductive tape is wound in a spiral shape with gaps between the turns. Therefore, even if damage occurs only in a partial area along the circumferential direction of the electric wire, the capacitance between the conductive tape and the conductor constituting the core wire changes significantly. As a result, a large change can occur in the characteristic impedance between the conductive tape and the conductor of the core wire. Therefore, by measuring the characteristic impedance between the conductive tape and the conductor of the core wire, it is possible to sensitively detect the formation of external damage in the electric wire.

[0033] A second electric wire of the present disclosure comprises a core wire having a conductor and an insulating coating that covers the outer periphery of the conductor and is exposed on the surface, and a laminated tape arranged on the outer periphery of the core wire, the laminated tape having a substrate configured as a tape-shaped insulator or semiconductor, and conductive coating layers formed on both sides of the substrate.

[0034] In the second electric wire, when damage is formed in the laminated tape, the characteristic impedance between the two coating layers changes. Therefore, by measuring the change in the characteristic impedance between the two coating layers, it is possible to sensitively detect the formation of damage in the electric wire. Since the measurement is completed between the two coating layers provided on the laminated tape, rather than using the constituent members of the core wire, such as the conductor, for damage detection, it is possible to impart a damage detection function to electric wires in various forms, such as a wire harness in which multiple electric wires are bundled, by simply wrapping the laminated tape around the wire. If a material whose electrical properties change with changes in the external environment is used as the base material, not only physical damage but also the effects of environmental changes such as temperature and humidity on the electric wire can be detected as a change in the characteristic impedance between the two coating layers.

[0035] [Details of the embodiment of the present disclosure] Hereinafter, the electric wire inspection system, the electric wire inspection method, and the electric wire according to the embodiment of the present disclosure will be described in detail with reference to the drawings. The electric wire inspection system according to the embodiment of the present disclosure is a system capable of inspecting the damage state of an electric wire, and the electric wire inspection method according to the embodiment of the present disclosure can be executed using the electric wire inspection system. In addition, an example of an electric wire to which the electric wire inspection system and the electric wire inspection method can be suitably applied is the electric wire according to the embodiment of the present disclosure. In this specification, the terms indicating the shape or arrangement of the components of the electric wire, such as vertical, orthogonal, linear, spiral, etc., include not only a geometrically strict concept but also an error range that is permissible for the electric wire.

[0036] <Wire to be inspected> First, an electric wire to be inspected in the electric wire inspection system and the electric wire inspection method according to the embodiment of the present disclosure will be described. The electric wire to be inspected includes a conductor and a core wire having an insulating coating that covers the outer periphery of the conductor, as in the case of a normal electric wire, and further includes a damage detection unit. The damage detection unit can perform an electric wire inspection in which an electric signal or an optical signal is input as an inspection signal and a response signal is obtained. During the electric wire inspection, the response signal obtained by the damage detection unit changes depending on the damage state of the electric wire, that is, depending on the presence or absence of damage to the electric wire, and more preferably depending on the degree and position of the damage.

[0037] The damage detection unit is composed of at least one of a component of the core wire and a component other than the core wire arranged along the core wire. Depending on which component constitutes the damage detection unit, it can be classified into the following three forms.

[0038] (i) A form in which the damage detection unit is composed only of the constituent members of the core wire Each component of the core wire plays the original role of an electric wire, such as power supply, signal transmission, and noise shielding. In this embodiment, the component of the core wire also plays the role of a damage detection unit in addition to the original role. For example, a conductive member such as a conductor that constitutes the core wire functions as a damage detection unit. The number of conductive members that function as a damage detection unit is not limited, and for example, an electric wire inspection may be performed by passing an electric signal from one end to the other end of one conductive member, or by evaluating the electrical characteristics between two conductive members that are insulated from each other. Specific examples of a configuration that uses two conductive members include a configuration in which two conductors included in the core wire are used as damage detection units, such as a twisted pair wire (electric wire C) that will be exemplified in the detailed description below, and a configuration in which the center conductor and the shield conductor in a coaxial shielded cable are used as damage detection units.

[0039] (ii) A form in which the damage detection unit is composed only of components other than the core wire In this case, the component of the core wire is not used as a damage detection unit. Instead, a component specialized for damage detection is arranged on the outside of the core wire and constitutes the electric wire together with the core wire. For example, a tape body, a wire body, etc. including a conductive member may be arranged on the outer periphery of the core wire and used as a damage detection unit. In this case, the electric wire inspection may be performed by passing an electric signal from one end to the other end of one conductive member arranged on the outer side of the core wire, or by arranging a component having two mutually insulated conductive members on the outer side of the core wire and evaluating the electrical characteristics between the two conductive members. As a specific example of an embodiment in which a damage detection component having two conductive members is arranged on the outer periphery of the core wire, a laminated tape-wrapped electric wire 3 described later as a second electric wire of the embodiment of the present disclosure is used, that is, a laminated tape having two conductive coating layers is wound around the outer periphery of the core wire and the electrical characteristics between the two conductive coating layers are evaluated. Furthermore, when this form (ii) is adopted, an optical signal rather than an electrical signal can be used as the inspection signal. For example, an optical fiber can be run parallel to the core wire, and an electric wire inspection can be performed by transmitting an optical signal through the optical fiber.

[0040] (iii) A configuration in which the damage detection unit is composed of a component of the core wire and a component other than the core wire In this case, the components of the core wire and the components arranged on the outside of the core wire cooperate to function as the damage detection unit. For example, the damage detection unit may be configured by a conductive member constituting the core wire, such as a conductor, and another conductive member arranged on the outer periphery of the core wire. A specific example may be a configuration using a conductive tape-wrapped electric wire 1, which will be described later as a first electric wire of an embodiment of the present disclosure, in other words, a configuration in which a conductive tape is wound around the outer periphery of the core wire and the electrical characteristics between the conductive tape and the conductor of the core wire are evaluated.

[0041] In any of the above forms (i) to (iii), the characteristic to be measured in the electric wire inspection may be selected according to the specific configuration of the damage detection unit so that damage formed in the electric wire, that is, a break, a short circuit, an external injury, or the like, can be detected. When an electric signal is used as the input signal, the characteristic to be measured, that is, the characteristic to be measured as the response signal, may be, for example, characteristic impedance or other characteristics having a correlation with the characteristic impedance, such as a reflection coefficient, a conductance, or a capacitance. These characteristics may be measured by a transmission method or a reflection method. In the following description, the case where the characteristic impedance is measured will be mainly described, but even if not specified, a characteristic having a correlation with the characteristic impedance may be used as a measurement target in the electric wire inspection instead of the characteristic impedance. When an optical signal is used as the input signal, various characteristics related to the transmission and reflection of the optical signal may be measured as the response signal.

[0042] In the following explanation of the electric wire inspection system and electric wire inspection method, a twisted pair wire, which corresponds to the above type (i), will be used as an example of an electric wire to be inspected. In a twisted pair wire, two insulated electric wires are twisted together to form a core wire. The following will deal with a type in which an electric signal containing an AC component is input as an inspection signal to the conductors that make up the two insulated electric wires, and the characteristic impedance between the two conductors is detected as a response signal by a reflection method. When damage occurs in a twisted pair wire, such as a short circuit between the two conductors, a change occurs in the characteristic impedance between the two conductors.

[0043] The purpose and location of the electric wire to be inspected by the inspection system and inspection method according to the embodiment of the present disclosure are not particularly limited, and examples thereof include electric wires installed inside various electric / electronic devices and transport equipment such as automobiles and aircraft, electric wires installed in structures such as houses and buildings, and electric wires constituting public facilities such as power transmission lines. However, the inspection system and inspection method described below are highly effective in a form in which the same type of electric wire is used in large numbers in a wide area, and it is preferable that the inspection system and inspection method are installed in mass-produced devices such as electric / electronic devices and transport equipment. The following description will be given assuming an electric wire installed inside an automobile.

[0044] <Electric wire inspection system> Next, a wire inspection system according to an embodiment of the present disclosure will be described.

[0045] FIG. 1 shows an outline of the electric wire inspection system A. The electric wire inspection system A includes a memory unit A1, an inspection unit A2, and an analysis unit A3. The memory unit A1 is a device capable of storing data, and is configured as an information management server or the like. The memory unit A1 may be configured as a cloud server. The inspection unit A2 is configured as a measuring device capable of performing electric wire inspection for individual electric wires, that is, inputting an inspection signal to the electric wire and acquiring a response signal. The analysis unit A3 is a device that performs wired or wireless communication with the memory unit A1 (shown by a dashed line in the figure), calls up data from the memory unit A1, and compares the called up data with data acquired by the inspection unit A2. Examples of the analysis unit A3 include a CPU that is provided integrally with the inspection unit A2, or a computer that is provided near the inspection unit A2 and can input data from the inspection unit A2 via wire or wireless.

[0046] The memory unit A1 is preferably provided at a location remote from the inspection unit A2 and the analysis unit A3. For example, the memory unit A1 may be provided on a server or cloud managed by a manufacturer of electric wires or automobiles, and the inspection unit A2 and the analysis unit A3 may be provided at an inspection company such as a car dealer or an automobile inspection factory. A large number of the inspection units A2 and the analysis units A3 may be provided in a large number of stores, factories, etc. located in a wide area. Each analysis unit A3 may be configured to communicate with the common memory unit A1 via the Internet, etc.

[0047] The storage unit A1 can store the response signals acquired by the electric wire inspection for a large number of electric wires for each individual electric wire. The storage unit A1 stores the response signals acquired for a large number of electric wires at a first time point. Here, the first time point refers to, for example, an initial state before the electric wire is manufactured and put to use. In the initial state, a manufacturer of an electric wire or an automobile performs an electric wire inspection, that is, input of an inspection signal and acquisition of a response signal, for each individual electric wire using a measuring device similar to the inspection unit A2, and stores the acquired response signal in the storage unit A1. At this time, the response signal obtained for an electric wire group including a large number of electric wires is stored for each individual electric wire. In other words, each of the response signals obtained for each individual electric wire constituting the electric wire group is linked to the individual electric wire by a serial number or the like and stored individually. FIG. 1 shows a state in which the response signals of the electric wires C1 to C3 are stored individually (three waveforms displayed to the right of the storage unit A1 in FIG. 1). In the example shown here, the response signal is assumed to be the characteristic impedance measured for each wire configured as a twisted pair.

[0048] The group of electric wires whose response signals are stored in the memory unit A1 preferably includes a plurality of electric wires of the same type. The same type of electric wire is an electric wire manufactured according to the same design and having the same structure. For example, an electric wire installed in many vehicles as an electric wire arranged in the same location of the same vehicle model is included in the group of electric wires. A plurality of electric wires of the same type may have variations in structure and / or characteristics within the range of manufacturing tolerance. Due to these variations, there may be differences in the response signals of each individual wire even if they are of the same type (see FIG. 4D). Since the memory unit A1 stores the response signal for each individual electric wire, even if there is a difference in the response signal due to these variations, the response signal for each individual wire is stored as it is, including the difference.

[0049] The inspection unit A2 performs an electric wire inspection on a specific target electric wire selected from the group of electric wires at a second time point that is later than the first time point. For example, the second time point is an inspection time that is performed as a periodic vehicle inspection after starting to use an automobile equipped with the electric wire. At this time, a measuring device constituting the inspection unit A2 is connected to the electric wire, and an inspection signal is input and a response signal is acquired. In the illustrated example, the inspection unit A2 is assumed to perform a form in which the characteristic impedance of the electric wire C2 configured as a twisted pair wire is measured by a time domain reflectometry as an electric wire inspection.

[0050] The analysis unit A3 can read the response signal acquired by the inspection unit A2 from the storage unit A1. The analysis unit A3 also communicates with the storage unit A1 and can call up a response signal corresponding to a specific individual electric wire from among the many response signals stored in the storage unit A1. During inspection, the analysis unit A3 calls up an initial state response signal from the storage unit A1 for the individual inspected by the inspection unit A2. In the illustrated embodiment, the analysis unit A3 calls up the response signal of the inspected electric wire C2 from the response signals in the initial states of the electric wires C1 to C3 stored in the storage unit A1.

[0051] Furthermore, the analysis unit A3 compares the response signal (C2a) at the time of inspection acquired by the inspection unit A2 with the response signal (C2b) at the initial state retrieved from the storage unit A1 for the target electric wire C2. Then, it is determined whether or not there is a difference between the two response signals C2a and C2b. If there is a difference equal to or greater than a predetermined level, it is determined that damage that did not exist in the initial state exists in the target electric wire C2. When comparing the response signals, the analysis unit A3 may obtain a difference between the response signal C2a at the time of inspection and the response signal C2b at the initial state, and determine whether or not there is a difference in the response signals based on the difference. In other words, it may determine that damage exists when the difference indicates an intensity equal to or greater than a predetermined threshold in the positive or negative direction. Furthermore, it is more preferable that the analysis unit A3 can perform a more detailed analysis of the comparison result of the response signals and specify the type of damage and / or the position where the damage is formed, if possible depending on the type of electric wire or electric wire inspection. The analysis using the difference and the method of specifying the position of the damage will be described later with specific examples.

[0052] <Wire inspection method> Next, a brief description will be given of an electric wire inspection method according to an embodiment of the present disclosure, which utilizes the above-described electric wire inspection system A. Fig. 2 shows a flow diagram of this electric wire inspection method.

[0053] In this electric wire inspection method, at a first point in time, an initial data acquisition step S1 and a data storage step S2 are performed. At a second point in time, a measurement step S3 and an analysis step S4 are performed. The first point in time refers to an initial state in which a vehicle equipped with an electric wire is not in use, and the initial data acquisition step S1 and the data storage step S2 are performed by a manufacturer of the electric wire or the vehicle. On the other hand, the second point in time refers to the time of inspection after the electric wire has started to be used, and the measurement step S3 and the analysis step S4 are performed by an inspection company at a car dealer, a vehicle inspection factory, or the like.

[0054] In the initial data acquisition process S1, a wire inspection is performed using a measuring device similar to that of the inspection unit A2. That is, an inspection signal is input to the wires and a response signal is obtained. The wire inspection is performed for each of the multiple wires that make up the wire group. In the example shown in FIG. 1, the characteristic impedance between the conductors of each of the wires (wires C1 to C3) configured as a twisted pair wire is measured.

[0055] Then, in a data storage step S2, the response signal (the characteristic impedance measurement result) acquired in the initial data acquisition step S1 is stored in the memory unit A1 for each individual electric wire. That is, the response signal is stored in the memory unit A1 while being linked to each individual electric wire by a serial number or the like. It is preferable that the group of electric wires whose response signals are stored in the memory unit A1 includes a plurality of electric wires of the same type.

[0056] After that, the automobile equipped with the electric wire is put into use, and the time for inspection arrives due to periodic vehicle inspection, etc. Then, the inspection company performs the measurement process S3. That is, the inspection unit A2 is connected to the target electric wire (electric wire C2) arranged inside the automobile, an electric wire inspection is performed, and a response signal is obtained. In the example shown in FIG. 1, the measurement process S3 involves measuring the characteristic impedance of the twisted pair wire, and obtaining the measurement result as a response signal.

[0057] When the measurement step S3 is completed, the analysis step S4 is carried out. In the analysis step S4, the inspection company appropriately inputs the serial number of the target electric wire, etc., to the analysis unit A3, and the analysis unit A3 acquires individual identification information of the target electric wire (C2) inspected by the inspection unit A2. Thereafter, the analysis unit A3 communicates with the storage unit A1 via the Internet, etc. Then, based on the individual identification information, the analysis unit A3 calls and reads the initial state response signal for the target electric wire (C2) from the response signals of the many electric wires (C1 to C3) stored in the storage unit A1.

[0058] In the analysis step S4, the analysis unit A3 further compares the response signal (C2a) at the time of inspection acquired by the inspection unit A2 with the response signal (C2b) in the initial state retrieved from the storage unit A1. Then, the analysis unit A3 appropriately obtains the difference between the two response signals and judges whether or not there is a difference between the two response signals. If there is a difference between the two response signals that is equal to or greater than a predetermined level, that is, equal to or greater than an error or negligible level, it is judged that damage that did not exist in the initial state has occurred in the target electric wire. On the other hand, if there is no difference between the two response signals that is equal to or greater than a predetermined level, it is judged that no problematic damage has occurred in the target electric wire. Furthermore, if possible depending on the type of electric wire or electric wire inspection, the analysis unit A3 further analyzes the comparison result of the response signals in detail and identifies the type of damage and / or the position where the damage has been formed.

[0059] <Response signal variation and changes due to damage> Next, we will explain the variation in response signals for each individual electric wire and the change in response signal due to damage. As an example, as shown in Figure 3, we will explain the case where the characteristic impedance of an electric wire C configured as a twisted pair wire with branches at two locations (points Cp5 and Cp6) is measured by the time domain reflectometry, while showing an example of actual measurement results. Note that the measurement example shown here was measured by the multicarrier time domain reflectometry (MCTDR) method, which will be explained later, among the time domain reflectometry methods.

[0060] Fig. 4A shows the characteristic impedance measured by a measuring device (inspection unit) A2 connected to the base end Cp1 of the electric wire C in an undamaged state. In Fig. 4A and Figs. 4B to 4E described later, the horizontal axis represents the time axis converted into the distance (unit: m) from the base end Cp1, and the vertical axis represents the characteristic impedance. The characteristic impedance on the vertical axis is shown as the amount of change with the value at the minimum distance set to zero. The measurement result in Fig. 4A shows that the electric wire C is significantly wavy, even though it is undamaged. This wavy structure is mainly due to reflections at the two branch points Cp5 and Cp6.

[0061] FIG. 4B shows the measurement results of the characteristic impedance when a short circuit is formed between two conductors at one end Cp2 of the electric wire C as a damage model. A change in the waveform can be seen when compared with the measurement results of FIG. 4A. This change is due to the formation of a short circuit at the end Cp2. FIG. 4C shows the difference waveform obtained by subtracting the waveform before the damage formation in FIG. 4A from the waveform after the damage formation in FIG. 4B. In this difference waveform, a large negative peak structure can be seen near a distance of 1.5 m. This peak structure can be associated with a change due to the formation of the damage. In fact, the end Cp2 where the short circuit is formed as the damage is 1.5 m away from the base end Cp1, which corresponds to the position where the peak is observed in the difference.

[0062] Next, we show the results of measuring the characteristic impedance of the wire (referred to as individual 1) that was the subject of measurement in Figure 4A, and the same type of wire, that is, another wire (referred to as individual 2) that was manufactured in the same way based on the same design, in an undamaged state. Figure 4D shows the characteristic impedance measurement results for individual 1 and individual 2. Comparing the waveforms of the two individuals, the trends in the increase and decrease in signal strength in the waviness are similar, but the details of the signal waveforms, such as the position and size of the peaks and valleys, are different between the two.

[0063] Figure 4E shows the difference between the waveforms of individual 1 and individual 2 in Figure 4D. A large wavy structure is seen in the difference signal in Figure 4E. Within this wavy structure, a negative peak structure similar to that observed in Figure 4C is seen at a distance of about 2 m. In other words, it can be said that the difference between the measurement results obtained for two different individual wires of the same species without damage shows a peak structure of similar shape and intensity to the difference obtained for the same individual wire with and without damage.

[0064] This means that when trying to detect damage to an electric wire based on the measurement results of the characteristic impedance, damage cannot be detected correctly unless the measurement results are compared for the same individual when no damage has been formed and when damage has been formed. Even if the measurement results obtained for individual 2 when no damage has been formed are compared with the measurement results obtained for individual 1 when damage has been formed, it is difficult to detect damage in individual 1. However, even for electric wires of the same type, if the individual is identified and the measurement results are compared between the same individual when it is in its initial state and when it is inspected some time after the initial state, as shown in Figure 4C, it becomes possible to detect whether damage has been formed and the location where the damage has been formed.

[0065] In the electric wire inspection system and the electric wire inspection method according to the embodiment of the present disclosure described above, in the initial state, response signals obtained for a plurality of electric wires are stored in the storage unit A1 for each individual electric wire, and during inspection, for a specific target electric wire to be inspected, the response signal in the initial state corresponding to the target electric wire is called from the storage unit A1. Then, the called response signal in the initial state is compared with the response signal obtained during inspection for the target electric wire. In this way, the acquisition and storage of the response signal in the initial state is performed by identifying each individual electric wire, and the response signal in the initial state and the response signal during inspection are compared for the individual inspected during inspection. Even if there is a variation in the response signal between the individual as shown in FIG. 4D, it is possible to sensitively detect the presence or absence of damage for each individual and to specify the position where the damage is formed without being influenced by the variation. In particular, when there are a large number of electric wires of the same type, the initial state response signals for each individual wire in a group of electric wires that includes these electric wires can be stored, and when each of the large number of electric wires is to be inspected, the response signals corresponding to each individual wire can be called up and compared, making it possible to perform highly accurate damage inspection for each of the large number of electric wires.

[0066] When an electric wire has elements that are discontinuous with the surroundings, such as branches, as in the electric wire C shown in FIG. 3, the electric signal is reflected at the locations where these elements are formed, and the response signal often shows behavior similar to that of the damaged location. In such cases, the variation in the response signal for each individual is particularly likely to be large. Furthermore, when the damage is minor, structures such as peaks resulting from the damage may be buried in structures resulting from discontinuous elements such as branches in the response signal, making it difficult to distinguish them. In such cases, storing the response signal in the initial state for each individual and comparing it with the response signal at the time of inspection is particularly effective in detecting damage. Furthermore, by using a differential detection method that calculates the difference between the response signal in the initial state and the response signal at the time of inspection, the detection accuracy can be further improved. This is because the contribution of discontinuous elements such as branches to the response signal can be at least partially canceled by taking the difference, and as a result, the structure in the response signal due to the damage is emphasized.

[0067] As another method for detecting the occurrence of damage from the change in the response signal of each individual electric wire while eliminating the variation in characteristics between the individual electric wires, a method of constantly connecting a measuring device to each electric wire, continuously inputting an inspection signal and acquiring a response signal, and continuously monitoring the change in the response signal can be considered. However, in this case, it is necessary to install a measuring device for each individual electric wire, that is, for each vehicle on which an electric wire is mounted, which requires a large cost. In contrast, if the electric wire inspection system and electric wire inspection method according to the present embodiment are used, each inspection company only needs to own one measuring device as the inspection unit A2, except for the manufacturer's use for acquiring initial data in the initial state. Then, each time an electric wire inspection is performed, a measuring device is connected to each electric wire to acquire a response signal, and when the electric wire inspection is completed, the measuring device is removed. In this way, it is possible to perform high-precision inspection of each individual electric wire while suppressing the cost required for inspecting the electric wire for damage, eliminating the influence of the variation in characteristics.

[0068] Furthermore, in the electric wire inspection system and the electric wire inspection method according to the present embodiment, information on response signals in the initial state regarding a large number of electric wires is accumulated in a common storage unit A1 consisting of an information management server of a manufacturer or the like. Then, a large number of inspection companies distributed over a wide area can access the common storage unit A1 via the Internet or the like through their respective analysis units A3, and call up the initial state response signal for the electric wire that each of them is inspecting from the initial state response signals of the large number of electric wires accumulated in the storage unit A1. A large-scale manufacturer acquires response signals when manufacturing or incorporating electric wires, identifies information on a large number of electric wires, manages it centrally, and makes it available to a large number of inspection companies distributed over a wide area, thereby efficiently carrying out each process of accumulating, managing, and using information on the characteristics of the electric wires.

[0069] In the electric wire inspection system and the electric wire inspection method according to the present embodiment, the types of the inspection signal and the response signal when inspecting the electric wire may be appropriately set according to the specific configuration of the damage detection unit provided on the electric wire. However, it is preferable to use an electric signal including an AC component as the inspection signal and measure the electrical characteristics such as the characteristic impedance in the time domain or the frequency domain. Then, when damage exists in the electric wire, in addition to detecting the presence of the damage, it is possible to determine the position where the damage occurs along the axial direction of the electric wire. In the response signal measured in the time domain or the frequency domain, the region on the response signal where there is a difference between the initial state and the time of inspection is associated with a position along the axial direction of the electric wire, and it is possible to determine that the damage occurs at that position. In the case of the time domain measurement, the time axis can be converted to a position on the electric wire based on the propagation speed of the inspection signal. On the other hand, in the case of the frequency domain measurement, the inspection signal obtained on the frequency axis is subjected to an inverse Fourier transform, so that the frequency information can be converted to a position on the electric wire.

[0070] When performing measurements in the time domain or frequency domain, the position of damage can be identified whether the measurements are performed by the transmission method or the reflection method, but it is particularly preferable to perform the measurements by the reflection method. When performing measurements by the reflection method, it is possible to perform wire inspection without connecting a measuring device to both ends of the wire, as long as the measuring device can be connected to only one end. Therefore, even if the wire is arranged in a location that is not easily accessible inside a vehicle or the like, or if the wire has a complicated path, it is possible to perform wire inspection without removing the wire or removing obstacles, as long as the measuring device can be connected to only one end of the wire. Next, in the description of a conductive tape-wrapped wire as the wire according to the first embodiment of the present disclosure, the measurement of characteristic impedance using the time domain reflection method and the frequency domain reflection method is also described in detail.

[0071] <Examples of wire configuration> Specific examples of electric wires that can be suitably applied as targets for inspection by the electric wire inspection system and the electric wire inspection method described above are given below. Here, two types of electric wires, a conductive tape-wrapped electric wire 1 as an electric wire according to the first embodiment of the present disclosure and a laminated tape-wrapped electric wire 3 as an electric wire according to the second embodiment of the present disclosure, are described in detail. Note that damage detection can be performed on these two types of electric wires 1 and 3 by methods other than using the electric wire inspection system and the electric wire inspection method of the present disclosure. For example, damage detection in a form in which electric wire inspection is performed continuously while a measuring device is always connected can also be applied. Therefore, matters related to other inspection methods will be described below as necessary.

[0072] [1] Conductive tape-wrapped wire First, a conductive tape-wrapped electric wire 1 will be described as an electric wire according to a first embodiment.

[0073] (Construction of conductive tape-wrapped wire) Fig. 5 shows a perspective view of a conductive tape-wrapped electric wire 1 as an electric wire according to a first embodiment of the present disclosure. Fig. 6A shows an example of a cross section of the conductive tape-wrapped electric wire 1 cut perpendicularly to the axial direction.

[0074] The conductive tape-wrapped electric wire (hereinafter sometimes simply referred to as electric wire) 1 has a core wire 10 and a conductive tape 20 arranged around the outer periphery of the core wire 10. The core wire 10 is the main body of the electric wire 1, and is responsible for applying current and voltage between both terminals and transmitting signals. At the same time, the core wire 10 and the conductive tape 20 function as a damage detection unit of the type (iii) described above, and detects a damage D formed on the surface of the electric wire 1 when the conductive tape 20 is damaged.

[0075] The core wire 10 has a conductor 11 made of a long conductive material, and an insulating coating 12 made of an insulating material that covers the periphery of the conductor 11. The insulating coating 12 is exposed on the surface of the core wire 10 as a whole, and forms the outer periphery of the core wire 10. In the illustrated embodiment, the core wire 10 has a single-wire structure including only one insulated wire in which the insulating coating 12 is provided on the periphery of the conductor 11. A conductive tape 20 is disposed in direct contact with the outer periphery of the insulating coating 12 that directly covers the periphery of the conductor 11.

[0076] The structure of the core wire 10 is not limited to the single-wire structure described above, and may be any structure having the conductor 11 and the insulating coating 12 that covers the outer periphery of the conductor 11 and is exposed on the surface. An existing electric wire can be used as the core wire 10 as it is. In the core wire 10, the insulating coating 12 may directly cover the outer periphery of the conductor 11, or may cover the outer periphery of the conductor 11 via another member. The number and arrangement of the conductors 11 are not particularly limited. Examples of the form of the core wire 10 other than the single-wire structure include a shielded cable in which a shield conductor is arranged on the outer periphery of an insulated electric wire and the outer periphery is covered with the insulating coating 12, a parallel pair wire in which a pair of insulated electric wires are arranged in parallel, and a pair cable in which the outer periphery of a twisted pair wire twisted together is covered with the insulating coating 12 as an outer sheath, and the like. However, as will be described in detail later, it is preferable that core wire 10 has a configuration that does not allow measurement of characteristic impedance between components of core wire 10 itself, as in the case of a single wire structure, and is susceptible to the influence of external noise, from the viewpoint of relatively increasing the significance of detecting damage D by installing conductive tape 20. Core wire 10 may be formed as a single straight line as shown in Figs. 5, 8 and 10, or may have branched portions (13A to 13C) midway as shown in Fig. 9.

[0077] The conductive tape 20 is configured as a tape body having electrical conductivity. The conductive tape 20 is wound around the core wire 10 in a spiral shape along the axial direction of the core wire 10 while in contact with the surface of the insulating coating 12 of the core wire 10. The conductive tape 20 is not wound tightly between adjacent turns in a close or overlapping state in the spiral shape, but is wound loosely between adjacent turns with gaps 25 left between the adjacent turns that are not occupied by the conductive tape 20. In the gaps 25 between the turns, the insulating coating 12 of the core wire 10 is not covered by the conductive tape 20 and is exposed on the surface of the electric wire 1 as a whole. Regarding the shape of the conductive tape 20, the tape body is distinguished from a filament such as a metal wire, and refers to a sheet-like member whose thickness is smaller than its width.

[0078] The conductive tape 20 may be made of any material as long as it is conductive, but it is preferable that the conductive tape 20 contains a metal material. In this case, the conductive tape 20 may be formed in the form of a metal foil made of a metal material throughout, or may be formed of a substrate having a layer of a metal material formed on the surface thereof. When a substrate is used, the substrate itself may be made of an insulating material such as an organic polymer material, as long as a layer of a metal material is formed on at least the surface of the substrate opposite to the surface that contacts the core wire 10. In either case, the type of metal material constituting the conductive tape 20 is not particularly limited, but examples thereof include copper or copper alloy, aluminum or aluminum alloy, etc., from the viewpoint of excellent conductivity and strength. However, if oxidation of the metal material becomes serious, there is a possibility that the detection of external damage, which utilizes the conductive property of the conductive tape 20 as part of the principle, may not be performed accurately, so it is preferable not to use iron or iron alloy as the metal material constituting the conductive tape 20. The conductive tape 20 may be fixed to the surface of the core wire 10 by adhesion or fusion.

[0079] The thickness of the conductive tape 20 is not particularly limited, but the thinner the conductive tape 20, the higher the sensitivity in detecting damage to the electric wire 1. Specifically, the conductive tape 20 should be thin enough that an expected damage D to the electric wire 1 will cause breakage, or if not breakage, will cause damage D1 deep enough and large enough to cause a change in the capacitance between the conductive tape 20 and the conductor 11. On the other hand, it is preferable that the conductive tape 20 has a sufficient thickness to provide a strength that does not interfere with winding in a spiral shape.

[0080] The pitch of the spiral shape formed by the conductive tape 20 on the outer periphery of the core wire 10 and the ratio of the width of the conductive tape 20 to the width of the gap 25 are not particularly limited. However, as shown in FIG. 6A, the conductive tape 20 needs to be wound at a sufficiently coarse pitch, that is, at a sufficiently large pitch and with the width of the gap 25 sufficiently large relative to the width of the conductive tape 20, so that in a cross section cut perpendicular to the axial direction of the electric wire 1, the conductive tape 20 does not cover the entire outer periphery of the core wire 10 but covers only a part of the outer periphery along the circumferential direction. More preferably, the ratio of the area exposed as the gap 25 without being covered by the conductive tape 20 to the circumferential length of the core wire 10 is 50% or more, and further 75% or more. On the other hand, the pitch of the spiral shape is preferably formed small enough that an expected external damage D in the electric wire 1 occupies one pitch or more along the axial direction of the electric wire 1, as shown in FIGS. 8 and 10. Then, even if damage D is formed at various positions in the axial and circumferential directions of the electric wire 1, the damage D is likely to overlap the portion where the conductive tape 20 is arranged. For example, as shown in FIG. 8, when the electric wire 1 is bent for routing, the pitch of the spiral may be set to be 1 / 3 or less of the allowable bending radius of the electric wire 1.

[0081] It is preferable that the conductive tape 20 is not covered on its outer periphery by any other member, but is exposed on the outer surface of the entire electric wire 1. This is because when the electric wire 1 comes into contact with or is rubbed against another object, damage D1 is likely to occur in the conductive tape 20, and the sensitivity in detecting external damage is high. However, the conductive tape 20 may be covered with a layer made of an organic polymer or the like, so long as the layer is thin enough to be easily damaged by contact with or friction against another object.

[0082] In the electric wire 1, the conductive tape 20 may be provided over the entire area or only in a part of the area along the axial direction of the core wire 10. The form of providing over the entire area is preferable because the damage D can be detected regardless of the location along the axial direction of the electric wire 1, and the form of providing over only a part of the area is preferable because the increase in the manufacturing cost and mass of the electric wire 1 due to the provision of the conductive tape 20 can be suppressed. When the conductive tape 20 is provided over only a part of the area, it is preferable to provide the conductive tape 20 including a part where the damage D is likely to occur due to contact or friction with other members, such as a part where the core wire 10 is bent. As shown in FIG. 9, even when the core wire 10 has the branched parts 13A to 13C in the middle, if there is a part where the damage D is likely to occur on the tip side of any of the branched parts 13A to 13C (the opposite side of the base end 1A where the measuring device 9 described later is connected), it is preferable to provide the conductive tape 20 including a part on the tip side of the branched part.

[0083] The electric wire 1 is not limited in its application, and may be used by being routed in any device such as a vehicle, or laid in any building. However, it is preferable to use the electric wire 1 in a floating state without electrically connecting the conductive tape 20 to earth potential (ground potential). By keeping the conductive tape 20 in a floating state, the electrical connection state between the conductor 11 and the earth potential, such as on / off control when a switch is provided between the core wire 10 and the earth potential, is less likely to affect the detection of the trauma D using the conductive tape 20.

[0084] (Method of Electric Wire Inspection) Next, a description will be given of the wire inspection performed on the conductive tape-wrapped wire 1. In the wire inspection, damage D1 occurring in the conductive tape 20 is directly detected, but the purpose of the wire inspection is to use the damage D1 in the conductive tape 20 as an indicator to detect the formation of damage D in the insulating coating 12 of the core wire 10, or to detect the onset of damage D in the insulating coating 12.

[0085] In the electric wire inspection, the characteristic impedance between the conductor 11 and the conductive tape 20 is measured. Then, the characteristic impedance obtained as a response signal is compared between the initial state and the time of inspection to determine whether or not a damage D has been formed on the electric wire 1 during the inspection. More preferably, the position where the damage D has been formed along the axial direction of the electric wire 1 is also specified.

[0086] 10, the electric wire inspection is performed by appropriately connecting a measuring device 9 (corresponding to the inspection unit A2) to the base end 1A of the electric wire 1, and measuring the characteristic impedance between the conductor 11 constituting the core wire 10 and the conductive tape 20. The characteristic impedance is preferably measured by the time domain reflectometry (TDR method) or the frequency domain reflectometry (FDR method).

[0087] Here, in relation to the electric wire inspection, the relationship between the characteristic impedance between the conductor 11 and the conductive tape 20 and the damage D of the electric wire 1 will be described. Figures 6A and 6B show a cross section of the electric wire 1. In Figure 6A, the damage D1 does not occur in the conductive tape 20, but in Figure 6B, damage D1 occurs in the conductive tape 20 at a position corresponding to the cross section due to the damage D occurring in the electric wire 1. The damage D1 formed in the conductive tape 20 does not necessarily have to reach the breakage of the conductive tape 20, and may simply be a scratch, but here, for ease of understanding, a state in which the conductive tape 20 is broken in a part of the cross section is shown.

[0088] The conductive tape 20 covering the outer periphery of the core wire 10 and the conductor 11 constituting the core wire 10 face each other with an insulating covering 12 made of an insulating material (dielectric) sandwiched therebetween, and a capacitance is defined between the conductive tape 20 and the conductor 11. The capacitance has a positive correlation with the area of ​​the conductive material facing each other with the dielectric sandwiched therebetween. Therefore, compared with the case where the conductive tape 20 does not have the damage D1 as shown in FIG. 6A, the capacitance is smaller when the conductive tape 20 has the damage D1 as shown in FIG. 6B. The characteristic impedance between the conductive tape 20 and the conductor 11 is significantly affected by the capacitance between the conductive tape 20 and the conductor 11. Therefore, when the capacitance between the conductive tape 20 and the conductor 11 changes due to the occurrence of the damage D1 in the conductive tape 20, the characteristic impedance between the conductive tape 20 and the conductor 11 changes as a result.

[0089] The electric wire 100 shown in FIG. 7A has a layer 120 of conductive material formed continuously around the entire circumference of the core wire 10. Even when the conductive layer 120 is formed around the entire circumference of the core wire 10 in this way, if damage D1 occurs in the conductive layer 120 as shown in FIG. 7B, theoretically, the magnitude of the capacitance between the conductive layer 120 and the conductor 11 of the core wire 10 may change, as in the case of FIG. 6B. If the damage D is formed around almost the entire circumference of the electric wire 100 and the damage D1 occurs in the conductive layer 120 around almost the entire circumferential area, the capacitance between the conductive layer 120 and the conductor 11 will change significantly, and the characteristic impedance between the conductive layer 120 and the conductor 11 will also change significantly. However, in reality, it is rare for damage to occur around almost the entire circumference of the electric wire. In many cases, the damage D caused by contact with or friction with an external object is formed, as shown in Figs. 8 and 10, occupying only a part of the region along the circumferential direction of the electric wire 1, but over a certain length along the axial direction of the electric wire 1. In the case where such damage D occupying only a part of the region along the circumferential direction of the electric wire 1 is formed, if the conductive layer 120 covers the entire circumference of the core wire 10 as shown in Fig. 7A, the proportion of the damage D1 in the entire conductive layer 120 becomes small, so the rate of change in capacitance (proportion of the amount of change relative to the initial state) associated with the occurrence of the damage D1 becomes small. As a result, the rate of change in the characteristic impedance associated with the formation of the damage D1 also becomes small. In this case, even if an attempt is made to detect the occurrence of the damage D1 by detecting the change in the characteristic impedance, it becomes difficult to detect the occurrence of the damage D1 with a high sensitivity.

[0090] On the other hand, in the case where the conductive tape 20 is wound roughly around the outer periphery of the core wire 10 with gaps 25 left between the turns as shown in FIG. 5, and the conductive tape 20 occupies only a part of the outer periphery of the core wire 10 in the cross section as shown in FIG. 6A, when the damage D1 is formed in the conductive tape 20, the ratio of the area occupied by the damage D1 to the area covered by the conductive tape 20 in the initial state becomes large as shown in FIG. 6B. Then, the capacitance between the conductive tape 20 and the conductor 11 changes with a large rate of change. As a result, the characteristic impedance between the conductive tape 20 and the conductor 11 also shows a large rate of change, and the formation of the damage D1 can be sensitively detected by detecting the change in the characteristic impedance. Even if the damage D is formed only in a part of the circumferential direction of the electric wire 1, if the damage D1 is formed in the conductive tape 20 by the damage D, it is sensitively reflected as a change in the characteristic impedance, and the formation of the damage D can be detected. In addition, even if the damage D1 is minor, the possibility of detection increases.

[0091] However, when the conductive tape 20 is wound roughly around the outer periphery of the core wire 10 and there are gaps 25 between the turns that are not covered by the conductive tape 20, as shown in Figs. 8 and 10, and thus the damage D is formed only in a part of the region along the circumferential direction of the electric wire 1, if the length of the damage D along the axial direction of the electric wire 1 is extremely short, the damage D is not applied to the portion where the conductive tape 20 is arranged, and the damage D1 is not formed in the conductive tape 20. However, when the damage D is formed on the electric wire 1 due to contact or friction with a surrounding object, the damage D is often formed over a certain length along the longitudinal direction of the electric wire 1. For example, as shown in Fig. 8, when the electric wire 1 is arranged in a vehicle or the like in a bent state, the outer part of the bend of the electric wire 1 may come into contact with a nearby object (such as the body of the vehicle) and the damage D may be formed. In this case, the damage D is often formed by contacting the object over a certain length in the region where the bend is formed. Therefore, if the spiral pitch is set so that the length of the expected trauma D is sufficiently long relative to the pitch of the spiral shape of the conductive tape 20, the trauma D will be applied to the location where the conductive tape 20 is placed at any point within the length range of the trauma D, causing damage D1 to the conductive tape 20. Then, a change in the characteristic impedance between the conductive tape 20 and the conductor 11 will appear via a change in capacitance, making it possible to detect the occurrence of damage D1.

[0092] In this way, by winding the conductive tape 20 in a rough spiral shape with gaps 25 between the turns around the outer periphery of the core wire 10, when an external damage D occurs in the electric wire 1, the occurrence of the external damage D can be detected sensitively by detecting a change in the characteristic impedance between the conductive tape 20 and the conductor 11. The occurrence of damage D1 in the conductive tape 20 wound around the outer periphery of the core wire 10 means that there is a high probability that the insulating coating 12 of the core wire 10 also has an external damage D, and by detecting the damage D1 formed in the conductive tape 20, it is possible to detect that the core wire 10, which is the main body of the electric wire 1, has an external damage D or is in a precursor stage about to develop a full-scale external damage D. As shown in FIG. 10, when the damage D1 in the conductive tape 20 in the straight electric wire 1 is formed as a break, the direction of change in the characteristic impedance basically becomes a direction in which the value increases with the formation of the damage D1. However, depending on the type and shape of the electric wire 1, the form and shape of the damage D1, and the like, the change in the characteristic impedance may occur in either the direction of increase or decrease.

[0093] As described above, by checking whether or not a change occurs in the characteristic impedance between the conductive tape 20 and the conductor 11 in the electric wire 1, it is possible to detect whether or not the electric wire 1 has a damage D. However, by measuring the characteristic impedance by the TDR method or the FDR method, it is possible to determine not only whether or not the damage D has been formed, but also the position where the damage D has been formed along the axial direction of the electric wire 1. As shown in FIG. 10, when the characteristic impedance between the conductive tape 20 and the conductor 11 is measured on the base end 1A side of the electric wire 1, the measurement result is a variation in the characteristic impedance as a function of time in the case of the TDR method. In the case of the FDR method, the variation in the characteristic impedance is obtained as a function of frequency. In either case, if damage D1 occurs in the conductive tape 20 in the middle of the axial direction of the electric wire 1, the inspection signal is reflected at the location of the damage D1. Then, the characteristic impedance changes discontinuously on the time axis or the frequency axis at a position corresponding to the damage D1. Therefore, in the measurement results obtained by the TDR method or the FDR method, a region where the characteristic impedance value changes discontinuously from the value in the surrounding region, or a region where the characteristic impedance value changes from the value at the time of the previous measurement, such as the initial state, can be detected as a change region R, and it can be determined that a damage D has been formed at a position on the electric wire 1 corresponding to the change region R. In this way, not only the presence or absence of the damage D on the electric wire 1, but also the position where the damage D has been formed can be specified.

[0094] Fig. 10 shows a schematic diagram of the relationship between the damage D formed on the electric wire 1 and the measurement results obtained when the TDR method is used. The upper part of the figure shows an electric wire 1 having a damage D, and the lower part shows an example of the measurement results obtained by the TDR method for the electric wire 1. In the measurement results, the solid line shows the case where the damage D is formed on the electric wire 1, and the dashed line shows the case where the damage D is not formed on the electric wire 1.

[0095] In the TDR method, the distance from the base end 1A and the value on the time axis are in a proportional relationship. In FIG. 10, the measurement results are plotted with time on the horizontal axis and the measured value of the characteristic impedance on the vertical axis. In the region on the electric wire 1 corresponding to the distance from the base end 1A to the point where the trauma D was formed, a peak P is observed that rises discontinuously from the surrounding region. Although there are also fine peak-like structures caused by noise and elements other than the trauma on the electric wire 1 in the surrounding region, if the core wire 10 is a simple straight line, the height of the peak P caused by the trauma D is often clearly larger than the peak-like structures unrelated to the trauma D. In addition, the measured value obtained in the region where the peak P caused by the trauma D occurs is increased compared to the value in the initial state where the trauma D is not formed, which is shown by the dotted line. In this way, if the region where the characteristic impedance changes discontinuously compared to the value in the surrounding region or the region where the characteristic impedance changes from the value in the initial state is detected as the change region R, the position of the change region R on the horizontal axis can be associated with the position of the trauma D from the base end 1A on the electric wire 1. That is, through the characteristic impedance measurement, not only the presence of the damage D can be detected, but also the position where the damage D was formed along the axial direction of the electric wire 1 can be specified. As shown in the following examples, the position of the damage D can be accurately specified within an error range of approximately 200 mm. Although the drawings are omitted, in the case of the FDR method, the horizontal axis is set to frequency, and a region where the characteristic impedance changes discontinuously compared with the value in the surrounding region, or a region where the value has changed from the initial state is detected as a change region R, so that the position where the damage D was formed along the axial direction of the electric wire 1 can be specified. In this case, the characteristic impedance is obtained as a function of frequency, and can be converted into information on the distance from the base end 1A of the electric wire 1 by performing an inverse Fourier transform.

[0096] When the TDR method is used, the inspection signal input to the base end 1A of the electric wire 1 is typically a pulse rectangular wave. However, as an advanced form of the TDR method, a form using an inspection signal in which components of different frequencies are superimposed at a predetermined intensity to form a predetermined waveform other than a rectangular wave can also be suitably used. Specifically, as the inspection signal, components over a continuous frequency range are superimposed at independent intensities for each frequency, but an electric signal in which some frequency components (exclusion frequencies) are missing or have discontinuously smaller in intensity compared to the surrounding frequencies within the continuous frequency range can be used. A form using an inspection signal having such an exclusion frequency is known as a multicarrier time domain reflectometry (MCTDR method), and is disclosed, for example, in the specification of U.S. Patent Application Publication No. 2011 / 035168. In the inspection signal, the influence of measurement noise can be reduced by setting the intensity of each frequency component and the exclusion frequency.

[0097] For example, when the electric wire 1 is arranged in an environment where other communication devices and communication electric wires are present nearby, such as inside an automobile, electromagnetic waves originating from a source outside the electric wire 1 are propagating around the electric wire 1. In this case, by setting an excluded frequency to include the frequencies of those electromagnetic waves and eliminating or reducing their contribution to the inspection signal, the components having those frequencies are less likely to affect the result of the characteristic impedance measurement. As a result, the electromagnetic waves propagating near the electric wire 1 are less likely to cause noise in the measurement result of the characteristic impedance of the electric wire 1, and it becomes possible to detect the damage D on the electric wire 1 sensitively and with high accuracy. It can be said that the MCTDR method is a measurement method that combines the advantages of the TDR method, such as the ability to directly associate the measurement result with the position where the damage D is formed, and the advantages of the FDR method, such as resistance to noise.

[0098] When detecting the damage D of the electric wire 1 by the TDR method including the MCTDR method or the FDR method, if the change in the characteristic impedance due to the damage D is significant, the damage D can be detected based on the measurement result itself of the characteristic impedance. In other words, the peak P corresponding to the damage D can be detected by looking at the measurement result itself and searching for an area where the value changes discontinuously compared with the surrounding area, or by comparing it with a previous measurement result such as an initial state and searching for a place where the value changes between the two. However, for example, when the damage D is minor, when the electric wire 1 is long, or when the electric wire 1 is branched as shown in the core wire 10' in FIG. 9, the peak P due to the damage D may be buried in a peak structure or noise due to factors other than the damage D, and the peak P may not be clearly recognized just by looking at the measurement result directly. In such a case, a differential detection method may be used. In other words, the difference between the measurement result of the characteristic impedance in the initial state and the measurement result of the characteristic impedance after a certain time has passed from the initial state is calculated, and the area where the difference value changes discontinuously from the values ​​in the surrounding areas is detected as the change area R, and the change area R is associated with the location where the trauma D is present.

[0099] As described above, in the conductive tape-wrapped electric wire 1, the core wire 10 may be made of any type of electric wire, but it is most preferable that the core wire 10 has a single-wire structure. In the case of a shielded cable or a paired cable, as described above as form (i), it is possible to detect the external damage D by measuring the characteristic impedance between the central conductor and the shielding conductor, or between the paired wires. However, in the case of a single-wire structure, the core wire 10 has only the conductor 11 as a conductive member, and therefore it is only by wrapping the conductive tape 20 around the outside that it becomes possible to detect the external damage D using the characteristic impedance. In addition, in the case of a single-wire structure, wrapping the conductive tape 20 around the core wire 10 reduces the influence of noise, and is therefore excellent in the effect of enabling the external damage D to be detected with high sensitivity. In other words, in the case of a shielded cable or a paired cable, a structure for reducing the influence of noise is included, so that a stable characteristic impedance is easily obtained, whereas in the case of a single-wire structure, the characteristic impedance between the conductor 11 and the earth potential becomes very unstable. However, the characteristic impedance is stabilized by using the single-wire structure as the core wire 10 and wrapping the conductive tape 20 around the outer circumference of the core wire 10. By detecting the damage D in such a state where the characteristic impedance is stabilized, it is possible to detect changes in the characteristic impedance value with high sensitivity and associate the changes with the formation of the damage D.

[0100] Furthermore, as described above, the conductive tape 20 is distinguished from a filament, and in the electric wire 1 according to the present embodiment, the conductive tape 20 configured as a tape body is used exclusively. However, even if a conductive filament such as a metal wire is wound in a rough spiral shape instead of the conductive tape 20, it may be possible to achieve detection of the damage D. However, when a filament is used, the difference in capacitance between the area where the conductive material is arranged and the area where it is not arranged on the outer periphery of the core wire 10 becomes too large, and the characteristic impedance becomes unstable. As a result, it becomes difficult to detect the damage D with high position resolution. For this reason, the conductive tape 20 configured as a tape body rather than a filament such as a metal wire is used.

[0101] When detecting the damage D by measuring the characteristic impedance while the electric wire 1 is still wired in an apparatus, it is preferable to measure the characteristic impedance by the inspection signal in a static state in which no voltage or current other than the inspection signal is applied to the electric wire 1 to be inspected, in order to increase the sensitivity and accuracy of the inspection. The electric wire inspection system and the electric wire inspection method described above are also based on the principle of performing the electric wire inspection in such a static state. However, the characteristic impedance can also be measured while a voltage or current other than the inspection signal is still applied to the electric wire 1. For example, the measurement device 9 can be always connected to the electric wire 1, and the characteristic impedance can be continuously measured and the damage D can be detected based on the measurement result while using the electric wire 1 in a state in which a current or voltage according to the original use of the core wire 10 is applied. Then, while using the electric wire 1, the formation of the damage D can be monitored in real time, and when the damage D is formed or when a symptom of the damage formation is reached, it can be detected immediately. For example, when core wire 10 has a single-wire structure, core wire 10 is often used to apply a DC current or a DC voltage. In this case, by inputting an inspection signal composed of AC components, it is possible to suitably measure the characteristic impedance even while continuing to apply a current or voltage to conductor 11.

[0102] [2] Laminated tape-wrapped electric wire Next, a laminated tape-wrapped electric wire 3 will be described as an electric wire according to a second embodiment. Here, the description of the configuration and inspection method common to the conductive tape-wrapped electric wire 1 and the effects thereof will be omitted and a brief description will be given.

[0103] (Structure of laminated tape-wrapped electric wire) FIG. 11A shows a schematic perspective view of the laminated tape-wrapped electric wire 3. In the laminated tape-wrapped electric wire 3, a laminated tape 40 is wound in a spiral shape around the outer periphery of a core wire 31. As with the conductive tape 20, the laminated tape 40 may be wound around the outer periphery of one core wire 31. However, as shown in FIG. 11A, the laminated tape 40 is preferably wound around the entire outer periphery of a wire harness 30 in which a plurality of core wires 31 are bundled. In this case, the state is a so-called laminated tape-wrapped wire harness, and in this specification, such a state is also included in the term laminated tape-wrapped electric wire 3. The laminated tape 40 may be directly wound around the outer periphery of a bundle of core wires 31 (electric wire bundle), or may be wrapped around the outer periphery of an exterior material such as a tube after the electric wire bundle is housed in the exterior material.

[0104] 11B (a cross section perpendicular to the tape longitudinal direction), the laminated tape 40 is configured by forming conductive coating layers 42, 42 on both sides of a substrate 41 made of a tape-shaped insulator or semiconductor. The coating layers 42, 42 provided on both sides of the laminated tape 40 function as two conductive members in the damage detection section of the above-mentioned form (ii).

[0105] In the laminated tape 40, the material of the base material 41 is not particularly limited as long as it is an insulator or a semiconductor, but a flexible tape-shaped insulator is preferably used. Suitable examples of the material of the base material 41 include nonwoven fabric tape and polymer tape. From the viewpoint of securing a distance between the two coating layers 42, 42 and making it easier to detect damage due to impedance changes, it is preferable that the base material 41 has a certain thickness, and from that viewpoint, it is particularly preferable to form the base material 41 from a nonwoven fabric tape. Alternatively, a functional material can be used as the base material 41. The electrical characteristics of the functional material, such as the dielectric constant, change depending on the external environment, such as temperature and humidity. For example, if a sheet of a hygroscopic polymer is used as the base material 41, when the base material 41 comes into contact with water, the dielectric constant and conductivity of the relevant portion change, and the impedance changes.

[0106] The material constituting the coating layers 42, 42 is not particularly limited as long as it is a conductive material, but metals such as copper or a copper alloy, aluminum or an aluminum alloy, etc. can be suitably used. Methods for forming the coating layers 42, 42 on both sides of the substrate 41 include adhesion of a metal sheet, metal vapor deposition, plating, etc. The thickness of the coating layers 42, 42 is not particularly limited, but it is preferable that the thickness is thin enough that expected external damage to the laminated tape-wrapped electric wire 3 will cause breakage, short circuit, etc., and cause a sufficient change in characteristic impedance.

[0107] An adhesive tape 43 may be provided on one surface of the covering layer 42 as needed. The adhesive tape 43 may be used to fix the laminated tape 40 in a state where it is wrapped around the outer periphery of the wire harness 30. When the laminated tape 40 is directly wrapped around the outer periphery of the electric wire bundle constituting the wire harness 30, if the electric wire bundle is held down by the laminated tape 40 via the adhesive tape 43, the laminated tape 40 may serve both as a damage detection section and as a bundling material that prevents the electric wire bundle from coming apart.

[0108] 11A and 11B, the covering layers 42, 42 are not formed at both ends of the laminated tape 40 in the width direction, and the base material 41 is exposed at some locations. However, the base material 41 does not necessarily need to be exposed in this manner, and the covering layers 42, 42 may be provided over the entire surface of the base material 41. However, by leaving areas at both ends of the base material 41 in the width direction where the covering layers 42, 42 are not provided, it is possible to prevent the covering layers 42, 42 on both sides from coming into contact with each other at the edge of the laminated tape 40, causing an unintended short circuit. In addition, when the base material 41 is made of a functional material that changes its electrical properties depending on the external environment, exposing the base material 41 and keeping it in direct contact with the external environment makes it easier for the electrical properties to change, sensitively reflecting changes in the external environment.

[0109] In the electric wire with laminated tape 3, the laminated tape 40 is wound in a spiral shape around the outer periphery of the wire harness 30 configured as a bundle of electric wires. Unlike the conductive tape 20 in the above-mentioned conductive tape-wrapped electric wire 1, there is no need to provide gaps between the turns of the spiral structure. The laminated tape 40 may be wound without providing any gaps between the turns, or may be wound while providing gaps narrower than the expected length of damage. It is preferable that the layer of the laminated tape 40 is exposed on the outer surface of the laminated tape-wrapped electric wire 3 as a whole.

[0110] (Method of Electric Wire Inspection) In the laminated tape-wrapped electric wire 3, the two conductive coating layers 42, 42 of the laminated tape 40 are used as damage detection sections, and damage can be detected by measuring the characteristic impedance between the two coating layers 42, 42 in an electric wire inspection. In the electric wire inspection, damage that occurs in the coating layers 42, 42 of the laminated tape 40 is directly detected, but the purpose of the electric wire inspection is to use the damage in the coating layers 42, 42 as an indicator to detect the formation of external damage in the core wire 31 (or the wire harness 30) or the onset of a warning sign that external damage is about to occur.

[0111] When the laminated tape-wrapped electric wire 3 is not damaged, the two coating layers 42, 42 constituting the laminated tape 40 are insulated from each other by the substrate 41 and exist as a conductive continuum along the longitudinal direction of the laminated tape 40, and each has a conductance determined by the material and thickness of the substrate 41 and the coating layers 42, 42. When damage occurs to the laminated tape 40 and the conductance between the two coating layers 42, 42 changes, the change in the conductance component is observed as a change in the characteristic impedance between the two coating layers 42, 42. For example, when the laminated tape-wrapped electric wire 3 comes into contact with or undergoes friction with an external object, at least one of the two coating layers 42, 42 (usually the coating layer facing outward) breaks in the middle of the longitudinal direction of the laminated tape 40. Then, the conductance between the two coating layers 42, 42 decreases, and the characteristic impedance increases.

[0112] As damage to the laminated tape 40, in addition to breakage of the coating layers 42, 42, a short circuit between the two coating layers 42, 42 is assumed. For example, when a sharp conductor such as a metal piece is pierced from the outside into the laminated tape 40 and penetrates the laminated tape 40, the two coating layers 42, 42 are short-circuited through the conductor. Alternatively, a short circuit can occur when the laminated tape 40 is subjected to severe friction or pressure, causing breakage or damage up to the layer of the substrate 41, and the coating layers 42, 42 on both sides of the substrate 41 come into local contact with each other without the substrate 41 being interposed. When a short circuit occurs, the conductance between the two coating layers 42, 42 increases and the characteristic impedance decreases.

[0113] In this way, the characteristic impedance between the two conductive coating layers 42, 42 constituting the laminated tape 40 is measured as an electric wire inspection, and the characteristic impedance obtained as a response signal is compared between the initial state and the time of inspection, so that damage can be detected in the core wire 31 (or the wire harness 30) around which the laminated tape 40 is wound. In other words, if there is a difference between the characteristic impedance in the initial state and the time of inspection, it can be detected that the core wire 31 (or the wire harness 30) around which the laminated tape 40 is wound has been damaged or is in a precursor stage of damage about to be formed. Furthermore, if the laminated tape-wrapped electric wire 3 has a relatively simple structure, such as a straight line, the type of damage can also be estimated based on the direction of change in the characteristic impedance. If the characteristic impedance changes in an increasing direction, it can be estimated that damage that may cause breakage has occurred in the coating layers 42, 42 of the laminated tape 40, and if the characteristic impedance changes in a decreasing direction, it can be estimated that damage that may cause a short circuit has occurred between the coating layers 42, 42.

[0114] In the laminated tape-wrapped electric wire 3, similarly to the conductive tape-wrapped electric wire 1 described above, by appropriately using a differential detection method, it becomes possible to detect damage sensitively and with high accuracy even when the change in the response signal is small or when there is an element that changes the response signal other than damage, such as a branch. Furthermore, similarly to the conductive tape-wrapped electric wire 1, by using a TDR method including an MCTDR method or an FDR method, it is possible to determine not only the presence or absence of damage but also the location where the damage is detected.

[0115] In the laminated tape-wrapped electric wire 3, if the substrate 41 constituting the laminated tape 40 is made of a functional material and changes its electrical properties depending on the external environment, such as temperature and humidity, it is possible to detect not only physical damage that causes breakage or short circuit in the coating layers 42, 42, but also changes caused by the external environment, such as getting wet, as damage. This is because when the electrical properties of the substrate 41, such as the dielectric constant, change due to a change in the external environment, the characteristic impedance between the two coating layers 42, 42 also changes. Conversely, if it is desired to detect only physical damage without being affected by the external environment, a material whose electrical properties change little depending on the environment should be used for the substrate 41.

[0116] In addition, although the case where the substrate 41 is made of an insulator is mainly described here, the electric wire inspection can be performed in the same manner to detect damage when the substrate 41 is made of a semiconductor. Furthermore, in a configuration in which the substrate 41 is made of a semiconductor, when the measuring device is constantly connected to the two coating layers 42, 42 of the laminated tape 40 and monitoring is continued, the sensitivity of damage detection can be increased by utilizing the fact that the substrate 41 is a semiconductor. Specifically, the characteristic impedance between the two coating layers 42, 42 may be measured in a state in which a low voltage that does not cause a short circuit through the substrate 41 is applied between the two coating layers 42, 42. In this state, if the laminated tape 40 is subjected to pressure or the like and insulation breakdown occurs between the two coating layers 42, 42, a short circuit occurs between the two coating layers 42, 42, and this is detected as a change in the characteristic impedance. Therefore, even damage that does not lead to a short circuit due to physical contact between the two coating layers 42, 42 can be detected sensitively.

[0117] Unlike the conductive tape-wrapped electric wire 1 described above, the laminated tape-wrapped electric wire 3 does not use the constituent members of the core wire 31 as the damage detection part, but instead uses only the constituent members of the laminated tape 40 provided separately from the core wire 31 to form the damage detection part. The laminated tape 40 used here is more complicated in terms of tape structure than the conductive tape 20 described above, but by not using the constituent members of the core wire 31 as the damage detection part, the damage detection function can be imparted regardless of the type or shape of the core wire 31. In other words, as long as the laminated tape 40 can be wound around the outer periphery, damage detection parts can be formed for core wires of various structures and types, as well as wire harnesses. Furthermore, damage detection using the laminated tape 40 does not use the constituent members of the core wire and wire harness, so if the laminated tape 40 is wound around any long member other than an electric wire or wire harness, it can be used to detect damage to that member in the same manner as described above. EXAMPLES

[0118] Examples are shown below, but the present invention is not limited to these examples.

[0119] [1] Conductive tape-wrapped wire First, we confirmed whether damage to conductive tape-wrapped wires could be detected by measuring the characteristic impedance.

[0120] [1-1] Damage detection on straight electric wires First, we confirmed whether damage to a straight conductive tape-wrapped electric wire can be detected by measuring the characteristic impedance.

[0121] (Sample preparation) A single-wire electric wire with a total length of 10 m was prepared as the core wire. A conductive tape made of copper foil was wrapped roughly in a spiral around the outer circumference of the core wire to prepare the sample electric wire. The spiral pitch was 10 mm. The ratio of the width of the conductive tape to the width of the gap not occupied by the conductive tape was approximately 1:1.

[0122] A simulated injury was formed on the sample electric wire at a position at a predetermined distance from the base end. That is, the conductive tape was broken at one point at the predetermined position. The position where the simulated injury was formed was changed along the axial direction of the electric wire to prepare a plurality of sample electric wires.

[0123] (Injury detection) The characteristic impedance between the core conductor and the conductive tape was measured at the base end of the sample wire prepared above. The measurement was performed using the MCTDR method. During the measurement, the potential of the conductive tape was kept floating.

[0124] (result) As an example, Fig. 12 shows the measurement results of the characteristic impedance when a simulated injury was formed at a position 232 cm from the base end of a sample electric wire. In Fig. 12 and Figs. 13 to 14C shown later, the horizontal axis represents the time axis converted into distance from the base end, and the vertical axis represents the characteristic impedance. However, the values ​​on the horizontal axis do not represent absolute values ​​of distance, but are amounts proportional to distance. The characteristic impedance on the vertical axis is shown as the amount of variation, with the value at zero distance set to zero.

[0125] Looking at the measurement results in Figure 12, apart from the large fluctuations near the zero distance originating from the equipment connection, a clear peak structure is seen at a position corresponding to a distance of 254 cm, which rises discontinuously from the surrounding area. This peak structure can be associated with the change in characteristic impedance due to trauma. The position of the peak top is at a distance of 254 cm, which is within an error range of about 20 cm from the position of 232 cm where the trauma was actually formed. From these results, it is confirmed that by measuring the characteristic impedance between the conductive tape and the conductor that constitutes the core wire, it is possible to detect the formation of a trauma and further to identify the position of the trauma with high accuracy.

[0126] Furthermore, FIG. 13 shows a number of measurement results when the position at which the simulated trauma was formed was changed. The trauma was formed at the position (distance from the base end) described in the legend corresponding to the symbol in the graph. According to FIG. 13, the position of the peak top of the characteristic impedance moves to the long distance side as the trauma formation position moves away from the base end from a to k. All of the values ​​of the distance of the peak top coincide with the actual position of the trauma formation within an error range of approximately 20 cm. This confirms that the formation of a wound can be detected up to a position about 10 m away by using the characteristic impedance measurement, and the position of the wound formation can be identified with a resolution of about 20 cm. However, as the trauma formation position moves away from the base end from a to k, the peak height becomes smaller and the peak width becomes wider. In other words, the detection sensitivity and the resolution in identifying the position tend to decrease as the trauma formation position moves away from the base end.

[0127] [1-2] Damage detection on branched electric cables Next, we confirmed whether damage to a branched electric wire can be detected by measuring the characteristic impedance.

[0128] (Sample preparation) As the core wire, an electric wire having a branch structure as shown in FIG. 9 was prepared. Here, the branch wires 15A to 15C branched from three branch portions 13A to 13C provided in the middle of the main wire 14, respectively. A conductive tape was wound roughly in a spiral shape around each of the main wire 14 and the branch wires 15A to 15C of this core wire 10' to prepare a sample electric wire. The conductive tapes wound around the main wire 14 and the branch wires 15A to 15C were kept in electrical contact with each other. The type of conductive tape used, the pitch of the spiral, and the ratio of the width of the conductive tape to the gap were the same as those in the above test [1-1]. A simulated injury was formed by breaking the conductive tape at a predetermined position of the main wire and each branch wire of this sample electric wire.

[0129] (Injury detection) As in the above test [1-1], the characteristic impedance was measured using the MCTDR method.

[0130] (result) Fig. 14A shows the measurement results when no injury was formed. On the other hand, Fig. 14B shows the measurement results when an injury was formed on the branch wire 15A extending from the branch 13A closest to the base end. The distance from the base end 1A to the injury site, across the branch 13A, was 4.0 m.

[0131] Comparing the state without a wound in Figure 14A with the state with a wound in Figure 14B, very similar patterns of measurement results were obtained in both cases. An upward peak not present in Figure 14A is seen near the wound site indicated by an asterisk in Figure 14B, and this peak can be associated with the change in characteristic impedance due to the wound. However, in addition to this peak, many other peak structures of the same or larger magnitude appear in both the upward and downward directions, making it difficult to clearly distinguish the peak corresponding to the wound from the other peak structures and identify the wound.

[0132] Figure 14C shows the difference between the measurement results in Figures 14A and 14B. This difference was obtained by subtracting the characteristic impedance value before the lesion in Figure 14A from the characteristic impedance value after the lesion in Figure 14B. The difference display in Figure 14C shows that the peak structure that was prominent in the short-distance region in the measurement results in Figures 14A and 14B has disappeared. On the other hand, an upward peak remains clearly at the lesion formation position indicated by an asterisk.

[0133] In this way, by taking the difference between the characteristic impedance measurement results before and after the formation of the trauma, the change in characteristic impedance resulting from the trauma can be clearly recognized and associated with the trauma. Although the results are not shown, even when a trauma is formed on the branch line 15B extending from the second branch 13B from the base end side, the trauma can be detected based on the change in characteristic impedance by using the difference in the same manner as above. From these results, it is confirmed that even when a branch exists in the core wire, the trauma can be detected by measuring the characteristic impedance between the conductor and the conductive tape constituting the core wire, and in particular, the trauma can be detected with high sensitivity by using the difference with the state where the trauma is not formed. Note that, beyond the third branch 13C from the base end, the distance from the base end is too large, making it difficult to clearly detect the change in characteristic impedance corresponding to the trauma, regardless of whether the trauma is formed on the main line side or the branch line side.

[0134] [2] Laminated tape-wrapped electric wire Finally, we confirmed whether damage detection was possible for laminated tape-wrapped electric wires.

[0135] (Sample preparation) For the laminated tape, insulating nonwoven fabric was cut into a tape shape and sandwiched between copper tape with a thickness of 0.1 mm and a width of 8 mm. The nonwoven fabric tape and the copper tape were bonded with an adhesive layer. This laminated tape was spirally wrapped around the outer circumference of a resin hose (outer diameter 10 mm; length 7 m) simulating a wire harness. The laminated tape was fixed to the resin hose with adhesive tape. When wrapping, the spiral pitch was about 25 mm. The ratio of the width of the laminated tape to the width of the gap not occupied by the laminated tape was approximately 1:1.

[0136] Two types of simulated trauma were created on the above specimen. For the first type of trauma, the outer copper tape layer of the two layers of copper tape that make up the laminated tape was broken at one location. The break was created 4.5 m from the base end of the specimen. For the second type of trauma, a metal pin was inserted through the laminated tape, creating an electrical short circuit between the two layers of copper tape. The short circuit was created 5 m from the base end of the specimen.

[0137] (Injury detection) At the base end of the sample prepared above, the reflection coefficient ρ was measured between the two layers of copper tape that make up the laminated tape. The measurement was performed using the MCTDR method. During the measurement, the potential of the two layers of copper tape was kept floating. The characteristic impedance between the two layers of copper tape was measured at an undamaged point, Z 0 , Z at the location where the damage has occurred L Then, the reflection coefficient ρ is expressed by the following equation (1). ρ = (Z L -Z 0 ) / (Z L +Z 0 ) (1) In other words, if the characteristic impedance at the damaged area increases, the reflection coefficient also increases, and if the characteristic impedance at the damaged area decreases, the reflection coefficient also decreases. Therefore, in this test, the reflection coefficient is measured as an alternative to the characteristic impedance.

[0138] (result) First, the results when a break is formed in the copper tape as an external injury are confirmed. FIG. 15A shows the measurement results of the reflection coefficient in the normal state before the break is formed, and FIG. 15B shows the state after the break is formed. In FIG. 15A to FIG. 15C, the horizontal axis represents the time axis converted into the distance from the base end (unit: m), and the vertical axis represents the reflection coefficient ρ. Looking at the measurement results after the break is formed in FIG. 15B, in addition to a large fluctuation originating from the equipment connection part near the distance of zero, a positive peak is generated near the distance of 4.5 m, which is not seen in the measurement results under normal conditions in FIG. 15A. FIG. 15C shows the difference obtained by subtracting the reflection coefficient value before the break from the reflection coefficient value after the break is formed, and the positive peak structure is even clearer in the difference.

[0139] Next, we will examine the results when a short circuit is formed in the copper tape as an external injury. Figure 16A shows the measurement results of the reflection coefficient in a normal state before the short circuit is formed, and Figure 16B shows the state after the short circuit is formed. In the measurement result after the short circuit is formed in Figure 16B, a negative peak is generated near a distance of 5 m that is not seen in the measurement result in the normal state in Figure 16A. Figure 16C shows the difference obtained by subtracting the reflection coefficient value before the short circuit is formed from the reflection coefficient value after the short circuit is formed, and in the difference, the negative peak structure is even clearer.

[0140] In this way, in the case of a specimen wrapped with laminated tape, whether a break is formed in the copper tape as external damage or a short circuit is formed, the reflection coefficient can be measured and compared with the measurement results under normal conditions, making it possible to detect such damage. The location of the damage can also be identified. Furthermore, the direction of the change in the reflection coefficient is opposite when a break is formed as damage and when a short circuit is formed, which shows that the type of damage can be estimated from the direction of the change. When a break occurs in the copper tape, Z in equation (1) L diverges to infinity, which explains the increase in the reflection coefficient ρ. On the other hand, when a short circuit occurs in the copper tape, Z L This explains the behavior of the reflection coefficient ρ decreasing.

[0141] Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. Furthermore, the conductive tape-wrapped electric wire and laminated tape-wrapped electric wire described above can be applied to cases other than those that are the subject of inspection by the electric wire inspection system and electric wire inspection method according to the embodiments of the present disclosure, and can achieve the object of detecting damage and identifying its position with a simple configuration. [Explanation of symbols]

[0142] 1 Conductive tape wrapped wire 1A Base end of wire 10,10' core wire 11 Conductor 12 Insulation coating 13A~13C Branching section 14 Main Line 15A~15C branch line 20 Conductive Tape 25 Gap 3. Laminated tape-wrapped wire 30 Wire Harness 31 Core Wire 40 Laminated Tape 41 Base material 42 Covering layer 43 Adhesive Tape 9. Measurement Equipment 100 wire 120 Conductive layer A Electrical Wire Inspection System A1 storage section A2 Inspection Department A3 Analysis Department C Electric wire Cp1~Cp6 Points on wire C C1~C3 electric wire C2a Response signal of wire C2 during inspection C2b Response signal from wire C2 in the initial state D Trauma D1 Damage to conductive tape P Peak R Change area S1~S4 Each step of the wire inspection method

Claims

1. A wire harness is formed by bundling a plurality of core wires each having a conductor and an insulating coating covering the outer periphery of the conductor and exposed on a surface thereof, The laminated tape is wound spirally around the outer periphery of the wire harness as a whole, The laminated tape has a base material formed as a tape-shaped insulator or semiconductor, and a conductive coating layer formed on each of both sides of the base material, The laminated tape is not covered on the outer periphery of the electric wire with any other member, or is covered with a layer composed of an organic polymer, and is exposed on the outer surface of the entire electric wire.

2. A core wire having a conductor and an insulating coating that covers the outer periphery of the conductor and is exposed on a surface thereof; A laminated tape disposed on an outer periphery of the core wire, The laminated tape has a base material formed as a tape-shaped insulator or semiconductor, and conductive coating layers formed on both sides of the base material, and has portions at both ends in a width direction where the coating layer is not formed and the base material is exposed, The laminated tape is not covered on the outer periphery of the electric wire with any other member, or is covered with a layer composed of an organic polymer, and is exposed on the outer surface of the entire electric wire.

3. A core wire having a conductor and an insulating coating that covers the outer periphery of the conductor and is exposed on a surface thereof; A laminated tape disposed on an outer periphery of the core wire, The laminated tape is configured as a tape-shaped insulator or semiconductor, and includes a base material whose electrical characteristics change depending on the external environment, and conductive coating layers formed on both sides of the base material, The laminated tape is not covered on the outer periphery of the electric wire with any other member, or is covered with a layer composed of an organic polymer, and is exposed on the outer surface of the entire electric wire.

4. The electric wire according to claim 1 , further comprising a branch portion midway.

5. 5. An electric wire inspection system for inspecting a damage state of the electric wire according to claim 1, a wire inspection in which an electric signal including an AC component is input as an inspection signal to the two coating layers constituting the laminated tape of the wire, and a characteristic impedance between the two coating layers is obtained as a response signal; The electric wire inspection system includes: a storage unit that stores, at a first point in time, the response signal obtained by the electric wire inspection for each individual electric wire group including a plurality of the electric wires; an inspection unit that performs the electric wire inspection on a target electric wire selected from the group of electric wires at a second time point that is later than the first time point; an analysis unit that retrieves the response signal at the first time point for the target electric wire from the memory unit, compares it with the response signal acquired by the inspection unit at the second time point, and determines that damage is present in the target electric wire if there is a difference between the two response signals.

6. The electric wire inspection system according to claim 5 , wherein the storage unit is provided at a location separate from the inspection unit and the analysis unit.

7. 7. The electric wire inspection system according to claim 5, wherein the analysis unit calculates a difference between the response signal at the first time point and the response signal at the second time point, and determines whether or not a difference exists between the two response signals based on the difference.

8. In the electric wire inspection, a characteristic impedance between two of the coating layers is measured as the response signal by a time domain reflectometry or a frequency domain reflectometry; 8. The electric wire inspection system according to claim 5, wherein the analysis unit corresponds an area in the response signal where a difference occurs between the response signal at the first time point and the response signal at the second time point to a position along the axial direction of the electric wire, and determines that damage has occurred at that position.

9. The inspection signal is a signal in which components over a continuous frequency range are superimposed with independent intensities for each frequency, and the frequency range includes excluded frequencies in which some frequency components are missing or whose intensities are discontinuously smaller than those of surrounding frequencies; 9. The electric wire inspection system according to claim 8, wherein in the electric wire inspection, a characteristic impedance between two of the coating layers is measured as the response signal by a time domain reflectometry.

10. 10. The electric wire inspection system according to claim 9, wherein in the inspection signal, the excluded frequency includes a frequency of an electromagnetic wave originating from a source external to the target electric wire and propagating around the target electric wire.

11. The electric wire inspection system according to claim 5 , wherein the group of electric wires includes a plurality of the electric wires of the same type.

12. Using the electric wire inspection system according to any one of claims 5 to 11, an initial data acquisition step of performing the electric wire inspection on the electric wires constituting the group of electric wires at the first time point and acquiring the response signal; a data storage step of storing the response signal acquired in the initial data acquisition step for each individual electric wire in the storage unit; a measuring step of performing the electric wire inspection on the target electric wire by the inspection unit at the second time point; an analysis step in which the analysis unit retrieves the response signal acquired at the first time point for the target electric wire from the memory unit, compares it with the response signal acquired in the measurement step at the second time point, and determines that damage has occurred to the target electric wire if there is a difference between the two response signals.

Images