Electrical wire inspection system, electrical wire inspection method, and method for using an electrical wire

Abstract

Provided are an electric cable inspection system and an electric cable inspection method capable of sensitively detecting damage to an electric cable, and an electric cable capable of being subjected to inspections performed thereby.　An electric cable inspection system A comprises an inspecting unit A1, a storage unit A2, and an analyzing unit A3, wherein: the inspecting unit performs an electric cable inspection in which a characteristic impedance between two electrically conductive members of the electric cable is acquired as a response signal by means of time domain reflection or frequency domain reflection; the storage unit stores the response signal obtained at a first time point; and the analyzing unit calls the response signal at the first time point from the storage unit, compares the same with the response signal obtained at a second time point after the first time point, and if there is a difference between the two response signals, associates a region of the response signal in which the difference arises with a position in an axial direction of the electric cable.

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 resulting response signal, it is necessary to compare the response signal with that when there is no damage and to perform calculations that take 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 used as the basis for the calculations.

[0006] However, damage to electric wires may not be accurately detected by inspections using basic information based on prior tests or theories. For example, factors other than the occurrence of damage, such as variations within manufacturing tolerances in the structure and characteristics of the electric wire, may affect the behavior of the response signal. In such cases, it may be difficult to detect changes in the response signal due to damage, distinguishing them from the effects of factors other than the damage. In particular, when damage to the electric wire is an external injury limited to the surface, which only causes a small change in the response signal, or when the electric wire has a structure, such as a branch, that affects the response signal and the change in the response signal due to the damage is difficult to clearly recognize due to signals originating from the structure, detection of damage using basic information becomes difficult.

[0007] 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 sensitively detect damage in an electric wire, 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]

[0008] The 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 having two conductive members that are electrically insulated from each other and are composed of 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 electric wire inspection system having an inspection unit, a memory unit, and an analysis unit, the inspection unit inputting an electric signal including an AC component as an inspection signal, and calculating a characteristic impedance between the two conductive members as a response signal, An electric wire inspection obtained by a time domain reflectometry or a frequency domain reflectometry is performed at a first time point and a second time point that is later than the first time point, the memory unit stores the response signal obtained by the electric wire inspection by the inspection unit at the first time point, the analysis unit calls up the response signal at the first time point from the memory unit and compares it with the response signal obtained by the electric wire inspection by the inspection unit at the second time point, and if a difference exists between the two response signals, the area where the difference occurs on the response signal corresponds to a position along the axial direction of the electric wire.

[0009] The electric wire inspection method according to the present disclosure uses the electric wire inspection system to carry out the following steps: an initial data acquisition step of performing the electric wire inspection on the electric wire by the inspection unit 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 in the memory unit; a measurement step of performing the electric wire inspection on the electric wire by the inspection unit at the second time point; and an analysis step of calling up the response signal acquired at the first time point from the memory unit and comparing it with the response signal acquired in the measurement step at the second time point, and, if a difference exists between the two response signals, associating an area on the response signal where the difference occurs with a position along the axial direction of the electric wire, by the analysis unit.

[0010] The 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 a conductive tape serving as a detection tape body arranged around the outer periphery of the core wire, the conductive tape being a substrate constituted as a tape-shaped insulator or semiconductor having a conductive layer made of a conductive material formed on one side thereof, and is wound around the outer periphery of the core wire in a spiral shape without any gaps, and in the spiral shape, the conductive layer between adjacent turns is not in contact with each other.

[0011] A second 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 a laminated tape serving as a detection tape body arranged around the outer periphery of the core wire, the laminated tape having a substrate constituted as a tape-shaped insulator or semiconductor and conductive coating layers formed on both sides of the substrate, and is wound around the outer periphery of the core wire in a spiral shape without any gaps, and in the spiral shape, the coating layers between adjacent turns are not in contact with each other. Effect of the Invention

[0012] The electric wire inspection system and the electric wire inspection method according to the present disclosure are capable of sensitively detecting damage in an electric wire. Also, the electric wire according to the present disclosure is an electric wire that can be inspected by such an electric wire inspection system and an electric wire inspection method. [Brief description of the drawings]

[0013] [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]4A to 4C are diagrams showing examples of response signals obtained by the electric wire inspection of the electric wire in Fig. 3, in which Fig. 4A shows a case where no damage occurs in electric wire 1, Fig. 4B shows a case where damage occurs in electric wire 1, and Fig. 4C shows a difference between a case where damage occurs in electric wire 1 and a case where no damage occurs in electric wire 1. Fig. 4D shows a comparison of the response signals of electric wire 1 and electric wire 2 where no damage occurs, and Fig. 4E shows a difference in the response signals of electric wire 1 and electric wire 2 where no damage occurs. [Diagram 5] FIG. 5 is a perspective view showing a configuration of a first example of a conductive tape-wrapped electric wire, which is 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] 11A and 11B are diagrams showing a second example of a conductive tape-wrapped electric wire, where Fig. 11A is a perspective view and Fig. 11B is a cross-sectional view showing a cross section cut perpendicular to the axial direction. [Figure 12] FIG. 12 is a cross-sectional view taken perpendicular to the axial direction of an example of a conductive tape-wrapped electric wire whose core is made of a composite electric wire. [Figure 13] Fig. 13A 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. 13B is a cross-sectional view illustrating a laminated structure of the laminated tape. [Figure 14] FIG. 14 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 15] FIG. 15 is a diagram showing the measurement results of the characteristic impedance when the position at which a lesion is formed on a straight conductive tape-wrapped electric wire is changed. [Figure 16] 16A to 16C are diagrams showing the measurement results of the characteristic impedance of a conductive tape-wrapped electric wire having a branch, in which FIG. 16A shows the measurement results when there is no external damage, FIG. 16B shows the measurement results when there is an external damage, and FIG. 16C shows the differential signal. [Figure 17] 17A to 17C are diagrams showing the measurement results of the characteristic impedance of a linear laminated tape-wrapped electric wire, in which Fig. 17A shows the measurement result when there is no external damage, Fig. 17B shows the measurement result when the laminated tape is broken, and Fig. 17C shows the differential signal. [Figure 18] 18A to 18C are diagrams showing the measurement results of the characteristic impedance of a linear laminated tape-wrapped electric wire, in which Fig. 18A shows the measurement result in an undamaged state, Fig. 18B shows the measurement result in a state in which the two conductive layers of the laminated tape are short-circuited, and Fig. 18C shows the differential signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [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 having two conductive members that are electrically insulated from each other and are composed of 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 electric wire inspection system having an inspection unit, a memory unit, and an analysis unit, the inspection unit inputting an electric signal including an AC component as an inspection signal, and calculating a characteristic impedance between the two conductive members as a response signal over time. An electric wire inspection obtained by area reflectometry or frequency domain reflectometry is performed at a first time point and a second time point that is later than the first time point, the memory unit stores the response signal obtained by the electric wire inspection by the inspection unit at the first time point, and the analysis unit calls up the response signal at the first time point from the memory unit and compares it with the response signal obtained by the electric wire inspection by the inspection unit at the second time point, and if a difference exists between the two response signals, the area in which the difference occurs on the response signal corresponds to a position along the axial direction of the electric wire.

[0015] In the above electric wire inspection system, a response signal obtained by an electric wire inspection at a first time point is stored in a storage unit, and a response signal obtained by performing an electric wire inspection at a second time point is compared with the response signal at the first time point retrieved from the storage unit. When damage (or a sign of damage; the same applies below) occurs in an electric wire, a change occurs in the characteristic impedance between two conductive members included in the electric wire. Therefore, if damage occurs in the 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 obtained at the first time point and the response signal obtained at the second time point are directly compared for the same electric wire, if a change occurs in the response signal due to the occurrence of damage in the electric wire, the change can be detected sensitively and the occurrence of damage can be detected. Since the response signal of a certain electric wire is observed over time, even if signal components due to the structure or characteristics of the electric wire appear in the response signal, the change in the response signal due to damage can be detected by distinguishing it from those signal components.

[0016] Furthermore, in the above-mentioned electric wire inspection system, the characteristic impedance between two conductive members is measured by a time domain reflection method or a frequency domain reflection method, thereby inspecting the electric wire. By adopting the time domain reflection method or the frequency domain reflection method, the area where the characteristic impedance has changed in the response signal can be associated with a position along the axial direction of the electric wire through appropriate calculations, etc., based on information on the area where the characteristic impedance has changed. Furthermore, the position can be associated with a position where damage has occurred in the electric wire. Therefore, the position where the damage has occurred along the axial direction of the electric wire can be easily and highly accurately identified. 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.

[0017] Here, 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 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.

[0018] 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.

[0019] In the inspection signal, the excluded frequency may include a frequency of an electromagnetic wave originating from a source outside the electric wire and propagating around the electric wire. In this case, when the electric wire to be inspected 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 may be set as the 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 with the nearby devices.

[0020] The electric wire to be inspected may have a branch part in the middle. When the electric wire has a branch part, a large structural component is often generated in the inspection signal and the response signal due to the branch part, and the change in the response signal due to damage is likely to be buried. However, by calling up the response signal acquired at a first time point for the electric wire to be inspected 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, etc.

[0021] The electric wire to be inspected may have a conductive tape wound in a spiral shape around the outer periphery of the core wire, and the damage detection unit may be configured with the conductor of the core wire and the conductive tape as the two conductive members. 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. Therefore, by measuring the characteristic impedance between the conductive tape and the conductor of the core wire, it is possible to sensitively detect the occurrence of an external injury to the electric wire or the presence of a sign of an external injury being formed.

[0022] In this case, the conductive tape is a substrate formed as a tape-shaped insulator or semiconductor, on one side of which a conductive layer made of a conductive material is formed, and is wound in a spiral shape without gaps around the outer periphery of the core wire, and in the spiral shape, the conductive layer between adjacent turns does not contact each other. By wrapping the conductive tape around the outer periphery of the core wire without gaps, even if a damage is formed in either the circumferential or axial position of the electric wire, the damage can be detected regardless of the position of the damage.

[0023] The core wire is in the form of a composite electric wire including a plurality of insulated electric wires each having the insulating coating provided on the outer periphery of the conductor, and the conductive tape is preferably wound in a spiral shape around the outer periphery of the composite electric wire as a whole. In this way, the formation of damage to the outer periphery of the composite electric wire as a whole can be sensitively detected using the conductive tape, regardless of the configuration of the composite electric wire, such as the shape, thickness, or type of insulated electric wires contained therein.

[0024] Alternatively, the electric wire to be inspected may have 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 of the base material, and the damage detection unit may be configured with the two coating layers of the laminated tape as the two conductive members. 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 occurs 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.

[0025] In this case, the core wire is in the state of a composite electric wire including a plurality of insulated electric wires each having the insulating coating provided on the outer periphery of the conductor, and the laminated tape is preferably wound in a spiral shape around the outer periphery of the composite electric wire as a whole. In this way, the formation of damage to the outer periphery of the composite electric wire as a whole can be sensitively detected using the laminated tape, regardless of the configuration of the composite electric wire, such as the shape, thickness, or type of insulated electric wires included therein.

[0026] The laminated tape is preferably wound tightly around the outer periphery of the core wire in a spiral shape, and the covering layer is preferably not in contact between turns in the spiral shape. Since the laminated tape is wound tightly around the outer periphery of the core wire, even if a damage is formed in either the circumferential or axial position of the wire, the damage can be detected regardless of the position of the damage.

[0027] 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.

[0028] The electric wire inspection method of the present disclosure uses the electric wire inspection system to carry out the following steps: an initial data acquisition step of performing the electric wire inspection on the electric wire by the inspection unit 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 in the memory unit; a measurement step of performing the electric wire inspection on the electric wire by the inspection unit at the second time point; and an analysis step of calling up the response signal acquired at the first time point from the memory unit and comparing it with the response signal acquired in the measurement step at the second time point, and, if a difference exists between the two response signals, associating an area on the response signal where the difference occurs with a position along the axial direction of the electric wire, by the analysis unit.

[0029] In the above-mentioned electric wire inspection method, in the initial data acquisition step and the data storage step, a response signal obtained by an electric wire inspection of the electric wire to be inspected at a first time point is stored in the storage unit. Then, in the inspection step, an electric wire inspection is performed at a second time point after the first time point, and in the analysis step, the response signal at the first time point is called from the storage unit and the response signal at the first time point is compared with the response signal at the second time point. If damage occurs in the electric wire between the first time point and the second time point, a change in characteristic impedance occurs, and the damage can be detected by detecting the change in the response signal. At this time, even if signal components due to the structure or characteristics of the electric wire appear in the response signal, the damage in the electric wire can be detected based on a comparison of the response signal at the first time point and the second time point without being influenced by the signal components, and as a result, the damage can be detected sensitively and with high accuracy. Furthermore, by adopting a time domain reflectometry or a frequency domain reflectometry and associating the position where the change in characteristic impedance occurs with the position along the axial direction of the electric wire, the position where the damage occurs along the axial direction of the electric wire can be easily and with high accuracy.

[0030] The first electric wire of the present disclosure comprises a core wire having a conductor and an insulating coating covering the outer periphery of the conductor, and a conductive tape serving as a detection tape body arranged around the outer periphery of the core wire, the conductive tape being a conductive layer made of a conductive material formed on one side of a substrate constituted as a tape-shaped insulator or semiconductor, and being wound around the outer periphery of the core wire in a spiral shape without any gaps, and in the spiral shape, the conductive layer between adjacent turns is not in contact with each other.

[0031] In the first electric wire, a conductive tape is wound around the outer periphery of the core wire, and when damage occurs to the conductive tape, the characteristic impedance between the conductive tape and the conductor constituting the core wire changes. Therefore, by measuring the characteristic impedance between the conductive tape and the conductor of the core wire, it is possible to sensitively detect the occurrence of damage to the electric wire. Since the conductive tape is wound around the outer periphery of the core wire without any gaps, it is possible to detect the damage regardless of the position in the circumferential direction or axial direction of the electric wire. In addition, since the conductive tape has a spiral shape, the conductive layers are not in contact with each other between adjacent turns, and therefore the occurrence of damage is sensitively reflected and detected as a change in the characteristic impedance.

[0032] A second electric wire of the present disclosure comprises a core wire having a conductor and an insulating coating covering the outer periphery of the conductor, and a laminated tape serving as a detection tape body arranged around the outer periphery of the core wire, the laminated tape having a substrate constituted as a tape-shaped insulator or semiconductor and conductive coating layers formed on both sides of the substrate, and is wound around the outer periphery of the core wire in a spiral shape without any gaps, and in the spiral shape, the coating layers between adjacent turns do not come into contact with each other.

[0033] 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 composite electric wire (wire harness) including a plurality of insulated electric wires, by simply winding the laminated tape. 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 influence 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. Since the laminated tape is wound around the outer circumference of the core wire without any gaps and the coating layers between adjacent turns are not in contact with each other, when an external damage occurs, it can be detected sensitively regardless of the position where the external damage is formed.

[0034] In the first electric wire and the second electric wire, the core wire is preferably configured as a composite electric wire in which insulated electric wires having the insulating coating provided on the outer periphery of the conductor are twisted together, and the detection tape body is preferably wound in a spiral shape around the outer periphery of the composite electric wire as a whole. In this way, the formation of damage to the outer periphery of the composite electric wire as a whole can be sensitively detected by the detection tape body, i.e., the conductive tape or laminated tape.

[0035] Here, the electric wire is configured as a composite electric wire for electric brakes with a damage detection function, the insulated electric wire includes at least one of a power line and a communication line of an electric brake device of an automobile, and the detection tape body is electrically connected to a measuring unit attached to the electric brake device. In the power line or communication line of an electric brake device of an automobile, the impact that can occur when damage occurs is large, and it is significant to use the electric wire of the present disclosure as a composite electric wire for electric brakes with a damage detection function to sensitively detect the occurrence of damage or its signs. In addition, by electrically connecting the detection tape body serving as the damage detection unit to a measuring unit attached to the electric brake device, it is possible to constantly or frequently monitor whether the electric wire has been damaged or whether there are signs of damage, and when damage or its signs occur, it is possible to detect them early and take measures.

[0036] [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 electric wire for damage (or a sign of damage; the same applies unless otherwise specified in this specification), and the electric wire inspection method according to the embodiment of the present disclosure can be executed using the electric wire inspection system. Moreover, 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.

[0037] <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 covering 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 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.

[0038] The damage detection unit is composed of two conductive members that are electrically insulated from each other. The two conductive members are composed of at least one of a component of the core wire and a member other than the core wire that is arranged along the core wire. Depending on which member constitutes the damage detection unit, it can be classified into the following three forms.

[0039] (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, but in this configuration, the components of the core wire also play the role of a damage detection unit in addition to their original role. For example, two conductive members such as conductors that make up the core wire can be used as damage detection units. Specific examples 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 described in detail later, and a configuration in which the center conductor and shield conductor in a coaxial shielded cable are used as damage detection units.

[0040] (ii) A form in which the damage detection unit is composed only of components other than the core wire In this case, the constituent members of the core wire are not used as the damage detection section. Instead, a member specialized for damage detection is provided in addition to the core wire, and constitutes the electric wire together with the core wire. For example, a tape body or a linear body containing a conductive member may be arranged around the outer periphery of the core wire and used as the damage detection section. A specific example is a laminated tape-wrapped electric wire 3, which will be described later as a second electric wire of an embodiment of the present disclosure, in which 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.

[0041] (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 provided in addition to 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 1,1', which will be described later as a first electric wire of an embodiment of the present disclosure, that is, 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.

[0042] 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, etc., can be detected. Examples of the characteristic to be measured as a response signal using an electric signal as an input signal include characteristic impedance, or other characteristics having a correlation with the characteristic impedance, such as a reflection coefficient, a conductance, and a capacitance. These characteristics may be measured by a transmission method or a reflection method. In the following, a form in which an electric signal containing an AC component is input as an inspection signal and the characteristic impedance between two conductive members constituting the damage detection unit is obtained as a response signal will be 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.

[0043] 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.

[0044] 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 can sensitively detect the occurrence of damage or signs of damage in an electric wire, and it is preferable to inspect electric wires that would be significantly affected if damaged, such as electric wires installed in automobiles. The following description will be given assuming an electric wire installed in an automobile.

[0045] <Electric wire inspection system> Next, a wire inspection system according to an embodiment of the present disclosure will be described.

[0046] FIG. 1 shows an outline of the electric wire inspection system A. The electric wire inspection system A includes an inspection unit A1, a storage unit A2, and an analysis unit A3. The inspection unit A1 is configured as a measuring device capable of performing an electric wire inspection for an individual electric wire C', that is, inputting an inspection signal to the electric wire C' and acquiring a response signal. In the embodiment described here, the inspection unit A1 is configured as a measuring device capable of inputting an electric signal including an AC component as an inspection signal to two conductive members constituting a damage detection unit of the electric wire C' and acquiring a characteristic impedance as a response signal by a reflection method. More specifically, the inspection unit A1 acquires the characteristic impedance by a time domain reflection method or a frequency domain reflection method, and these methods will be described in detail later.

[0047] The storage unit A2 is a device capable of storing data, and suitable examples thereof include an internal storage device integral with the inspection unit A1, and a memory device such as an external storage device connectable to the inspection unit A1. Alternatively, the storage unit A2 can be constructed as an information management server capable of communicating with the inspection unit A1 and / or the analysis unit A3 by wired or wireless communication, such as a cloud server.

[0048] The analysis unit A3 is a device that can call up data from the memory unit A2 and compare the called up data with data acquired by the inspection unit A1. Examples of the analysis unit A3 include a CPU that is integrated with the inspection unit A1, or a computer that is provided near the inspection unit A1 and can input data from the inspection unit A1 and the memory unit A2 via wired or wireless communication.

[0049] It is preferable that the inspection unit A1, the storage unit A2, and the analysis unit A3 are all provided near the electric wire C' to be measured. In particular, it is preferable that the inspection unit A1 is kept connected to the conductive member constituting the damage detection unit in the electric wire C', and is always in a state in which the electric wire inspection can be performed by inputting the inspection signal and obtaining the response signal. It is preferable that the storage unit A2 and the analysis unit A3 are provided as built-in devices or auxiliary devices of the inspection unit A1, and the input of the response signal from the inspection unit A1 to the storage unit A2 and the analysis unit A3, the storage of the data in the storage unit A2 that receives the input, and the analysis of the data in the analysis unit A3 are always in a state in which they can be performed. For example, the inspection unit A1 may be always connected to the damage detection unit of the electric wire C' arranged in the automobile, and the storage unit A2 may be configured as an internal storage device of the inspection unit A1, and the analysis unit A3 may be configured as a CPU attached to the inspection unit A1. As a further specific example, the electric wire inspection system A may be configured as an inspection system for a composite electric wire for an electric brake with a damage detection function. In this case, the core of the electric wire C' constitutes a power line or a communication line of the electric brake device of the automobile, and the damage detection unit is electrically connected to a measurement unit attached to the electric brake device. As the measurement unit, it is preferable to use a measurement device that integrally comprises the functions of the inspection unit A1, the memory unit A2, and the analysis unit A3.

[0050] In the electric wire inspection system A according to the present embodiment, first, at a first time point, the inspection unit A1 performs an electric wire inspection on the electric wire C'. In the illustrated example, it is assumed that the inspection unit A1 performs a wire inspection by measuring the characteristic impedance by a time domain reflectometry on the electric wire C' configured as a twisted pair wire. Then, the storage unit A2 stores a response signal acquired by the inspection unit A1 at the first time point. Here, the first time point refers to, for example, an initial state before the electric wire C' is manufactured and put to use.

[0051] The inspection unit A1 performs another wire inspection on the electric wire C' that was inspected at the first time point at a second time point after the first time point. For example, the second time point is the time when any one of the electric wire inspections performed continuously and constantly after the start of use of the automobile equipped with the electric wire C' or the electric wire inspections performed periodically at a predetermined interval is performed. The electric wire inspection is performed in the same manner as the inspection performed at the first time point described above.

[0052] The analysis unit A3 can read the response signal acquired by the inspection unit A1 from the inspection unit A1. The analysis unit A3 can also communicate with the storage unit A2 and call up the response signal stored in the storage unit A2. When the inspection unit A1 performs an electric wire inspection at a second time point, the analysis unit A3 reads the response signal c2 obtained by the electric wire inspection and calls up the response signal c1 obtained by the electric wire inspection at the first time point from the storage unit A2.

[0053] Furthermore, the analysis unit A3 compares the response signal c2 at the second time point acquired by the inspection unit A1 with the response signal c1 at the first time point retrieved from the storage unit A2 for the electric wire C' to be inspected. Then, it is determined whether or not there is a difference between the two response signals c1, c2. Then, if there is a difference equal to or greater than a predetermined level, it is determined that damage that did not exist at the first time point exists in the electric wire C' at the second time point. When comparing the response signals, the analysis unit A3 may obtain a difference between the response signal c2 at the second time point and the response signal c1 at the first time point, and determine whether or not there is a difference in the response signals based on the difference. In other words, it may be determined that damage exists when the difference indicates an intensity equal to or greater than a predetermined threshold value in the positive or negative direction. Furthermore, in this embodiment, in response to the inspection unit A1 measuring the characteristic impedance by the time domain reflectometry or the frequency domain reflectometry, the analysis unit A3 may analyze the comparison result of the response signals in more detail to identify the position where the damage has been formed. It may also be possible to identify the type of damage further by a more detailed analysis. The analysis using the difference and the method for identifying the location of damage will be explained later with concrete examples.

[0054] <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.

[0055] 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, for example, an initial state in which a vehicle equipped with the electric wire C' is not in use. On the other hand, the second point in time refers to, for example, the time of inspection after the use of a vehicle equipped with the electric wire C' has begun.

[0056] In the initial data acquisition process S1, at a first point in time, the inspection unit A1 performs an electric wire inspection. That is, an inspection signal is input to the electric wire C' and a response signal c1 is acquired. In the example shown in FIG. 1, the characteristic impedance between the conductors of the electric wire C' configured as a twisted pair wire is measured. Then, in the data storage process S2, the response signal c1 (measurement result of the characteristic impedance) acquired in the initial data acquisition process S1 is stored in the storage unit A2.

[0057] After that, a predetermined period of time elapses, and a second time point arrives as the time to inspect the electric wire C'. Then, the measurement step S3 is performed. That is, the inspection unit A1 performs an electric wire inspection on the electric wire C' to be inspected, and obtains a response signal c2. In the example shown in FIG. 1, in the measurement step S3, similar to the initial data acquisition step S1, the characteristic impedance of the electric wire C' configured as a twisted pair wire is measured, and the measurement result is obtained as the response signal c2.

[0058] When the measurement step S3 is completed, the analysis step S4 is performed. In the analysis step S4, the analysis unit A3 calls and reads the response signal c1 at the first time point stored in the storage unit A2. In the analysis step S4, the analysis unit A3 further compares the response signal c2 at the second time point acquired by the inspection unit A1 with the response signal c1 at the first time point called from the storage unit A2. Then, after appropriately calculating the difference between the two response signals c1 and c2, it is determined whether or not there is a difference between the two response signals c1 and c2. If there is a difference between the two response signals c1 and c2 that is equal to or greater than a predetermined level, that is, equal to or greater than an error or a negligible level, it is determined that damage that did not exist at the first time point has occurred in the electric wire C' by the second time point. On the other hand, if there is no difference between the two response signals c1 and c2 that is equal to or greater than a predetermined level, it is determined that no problematic damage has occurred in the electric wire C'. In addition, the analysis unit A3 performs a more detailed analysis of the comparison result between the response signals c1 and c2 to identify the location of the damage and, if possible depending on the type of wire, to identify the type of damage.

[0059] In the above description, the response signal is stored in the storage unit A2 as a first time point when the automobile equipped with the electric wire C' is not in use, and the electric wire inspection is performed as a second time point when the automobile equipped with the electric wire C' is started to be used. However, it is preferable to perform the electric wire inspection multiple times after the automobile equipped with the electric wire C' is started to be used. Furthermore, it is preferable to keep the inspection unit A1 connected to the electric wire C' to be inspected, input the inspection signal and obtain the response signal continuously, and perform the electric wire inspection repeatedly at all times, or to automatically perform the electric wire inspection at predetermined time intervals or each time the device equipped with the electric wire C' performs a predetermined operation (for example, when the electric wire C' constitutes an electric brake device of an automobile, each time the brake is operated). In these cases, the time point when each of the multiple electric wire inspections is performed is the second time point.

[0060] In this way, when the electric wire inspection is repeated multiple times, the response signal at the first time point stored in the memory unit A2 and used in the analysis step may remain unchanged, for example, as the response signal in the initial state before the electric wire C' is put to use, or may be updated as the electric wire inspection is repeated. In other words, when the electric wire inspection is constantly repeated or is performed many times at predetermined time intervals or each time the device performs a predetermined operation, the response signal (c n-1 The response signal (c) is newly stored in the memory unit A2 as a response signal at the first time point, and a newly acquired response signal (c n ) is the response signal at the second time point, and both response signals (c n-1 and c n ) can be compared. Next, the newly acquired response signal (c n ) is newly stored in the memory unit A2 as a response signal at the first time point, and the response signal (c n+1 ) is the response signal at the second time point, and both response signals (c n and c n+1 ) may be analyzed. By repeating this process many times, if a change occurs in the response signal over time, the change can be detected sensitively. The number of response signals stored in the memory unit A2 as data at the first time point is not limited to one, and may be multiple. In other words, not only the response signal obtained in one electric wire inspection, but also the response signals obtained in multiple electric wire inspections can be stored in the memory unit A2. Among the response signals of the multiple electric wire inspections, one response signal selected according to, for example, the time interval from the electric wire inspection at the second time point may be used as the response signal at the first time point in the analysis process, or the multiple response signals may be averaged and used as the response signal at the first time point in the analysis process.

[0061] In the electric wire inspection system and the electric wire inspection method according to the present embodiment, it is assumed that an electric characteristic such as characteristic impedance is measured in the time domain or the frequency domain using an electric signal including an AC component. Therefore, when damage exists in the electric wire, in addition to detecting the presence of the damage, the position where the damage occurs along the axial direction of the electric wire can be determined. This is because, when a difference exists between a first time point and a second time point in a response signal measured in the time domain or the frequency domain, the region on the response signal where the difference occurs can be associated with a position along the axial direction of the electric wire. In other words, when a difference exists between two response signals, it is possible to determine that the electric wire is damaged, and further, by associating the region on the response signal where the difference occurs with a position along the axial direction of the electric wire, it is possible to determine that the damage occurs at that position. In the case of 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 frequency domain measurement, the inspection signal obtained with respect to the frequency axis is subjected to an inverse Fourier transform, so that frequency information can be converted to a position on the electric wire.

[0062] 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 measuring instruments to both ends of the wire, as long as a 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 a measuring device can be connected to only one end of the wire. Therefore, it is suitable for a form in which a measuring device is always connected to the wire to be inspected, and wire inspection is performed continuously or frequently. Later, 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.

[0063] <Response signal variation and changes due to damage> Next, we will explain the variation in response signals for each electric wire and the change in response signals due to damage. As an example, we will explain the case where the characteristic impedance of electric wire C, which is configured as a twisted pair wire with branches at two locations (points Cp5 and Cp6) as shown in Figure 3, is measured by the time domain reflectometry, using 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.

[0064] Fig. 4A shows the characteristic impedance measured by a measuring device (inspection unit) A1 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.

[0065] 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.

[0066] Next, we show the results of measuring the impedance of the electric wire (electric wire 1) that was the subject of measurement in Figure 4A and the same type of electric wire, that is, another electric wire (electric wire 2) that was manufactured in the same way based on the same design, in an undamaged state. Figure 4D shows the measurement results of the characteristic impedance of electric wire 1 and electric wire 2 together. Comparing the waveforms of electric wires 1 and 2, the trends of 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.

[0067] Figure 4E shows the difference between the waveforms of wire 1 and wire 2 in Figure 4D. A large wavy structure can be seen in the difference signal in Figure 4E. Within this wavy structure, a negative peak structure can be seen near a distance of 2 m, which is similar to the negative peak structure observed near a distance of 1.5 m in Figure 4C. In other words, it can be said that the difference between the measurement results obtained for two undamaged wires of the same type shows a peak structure of similar shape and intensity to the difference obtained for the same wire with and without damage.

[0068] This means that when damage to an electric wire is to be detected based on the measurement result of the characteristic impedance, the damage cannot be detected correctly unless the measurement results are compared for the electric wire to be inspected when no damage is formed and when damage is formed. In the electric wire inspection system and the electric wire inspection method according to the embodiment of the present disclosure described above, the response signal c1 obtained for the electric wire C' to be inspected at a first point in time is stored in the storage unit A2, and at a second point in time, the electric wire inspection is performed on the electric wire C' to be inspected to obtain the response signal c2, which is compared with the response signal c1 of the electric wire C' at the first point in time retrieved from the storage unit A2. In this way, instead of using a standard response signal provided by, for example, an electric wire or automobile manufacturer (a response signal acquired representatively of a standard sample electric wire) as a response signal to be considered as normal and to be compared, the response signal itself that was actually acquired at a previous first point in time for the actual electric wire to be inspected is used. Even if signal behavior resulting from the structure or characteristics of the electric wire appears in the response signal, such as the variation in response signals between electric wires shown in Figure 4D, it is possible to sensitively detect the presence or absence of damage in the electric wire to be inspected itself and further identify the location where the damage has occurred, without being influenced by such signal behavior.

[0069] In particular, when an electric wire has elements that are discontinuous with the surroundings, such as a branch, as in the electric wire C shown in FIG. 3, the electric signal is reflected at the location where the elements are formed, and large signal components originating from the elements appear in the response signal, often exhibiting behavior similar to that of a damaged location. In such a case, if the damage is minor, structures such as peaks originating from the damage in the response signal may be buried in structures originating from discontinuous elements such as branches, making them difficult to distinguish. In such cases, it is particularly effective in detecting damage to store a response signal at a first time point for the electric wire to be inspected and compare it with a response signal at a second time point. Furthermore, by using a differential detection method that calculates the difference between the response signal at the first time point and the response signal at the second time point, 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 on the response signal due to the damage is emphasized.

[0070] <Examples of wire configuration> Hereinafter, specific examples of electric wires having a detection tape body that can be suitably applied as an object of inspection by the electric wire inspection system and the electric wire inspection method described above will be given. Here, two types of electric wires, namely, the conductive tape-wrapped electric wires 1, 1' as the electric wire according to the first embodiment of the present disclosure, and the laminated tape-wrapped electric wire 3 as the electric wire according to the second embodiment of the present disclosure, will be described in detail. The conductive tape-wrapped electric wires 1, 1' include a conductive tape as the detection tape body, and the laminated tape-wrapped electric wire 3 includes a laminated tape as the detection tape body. It should be noted that damage detection can be performed on these electric wires by methods other than using the electric wire inspection system and the electric wire inspection method disclosed herein. For example, instead of comparing the response signals at the first and second time points, an analysis can be performed such that an area where the characteristic impedance value changes discontinuously from the value in the surrounding area in the response signal acquired at a certain time point is detected and associated with damage.

[0071] [1] Conductive tape-wrapped wire First, conductive tape-wrapped electric wires 1, 1' will be described as an electric wire according to a first embodiment. First, the configuration and the method of wire inspection of the conductive tape-wrapped electric wire 1 according to the first example will be described in detail, and then the conductive tape-wrapped electric wire 1' according to a second example will be described, focusing on the differences from the first example.

[0072] (Configuration of the Conductive Tape-Wrapped Electric Wire According to the First Example) Fig. 5 shows a perspective view of a conductive tape-wrapped electric wire 1 as a first example of the electric wire according to the 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.

[0073] 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 and / or transmitting signals between both terminals. 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.

[0074] 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 preferably 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 having the insulating coating 12 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.

[0075] The structure of the core wire 10 is not limited to the single-wire structure described above, and may be any structure having a conductor 11 and an insulating coating 12 that covers the outer periphery of the conductor 11 and is preferably 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 an insulating coating 12, a pair cable in which a parallel pair wire in which a pair of insulated electric wires are arranged in parallel or a twisted pair wire twisted together is covered with an insulating coating 12 as an outer sheath, and a composite electric wire (wire harness) including a plurality of insulated electric wires. An example of a composite electric wire including a plurality of coated electric wires is a composite stranded electric wire in which a plurality of insulated electric wires such as a power line or a communication line are twisted together (see FIG. 12). However, as will be described in detail later, it is preferable that the core wire 10 has a form in which the characteristic impedance cannot be measured between the constituent members of the 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 that the significance of detecting the damage D by installing the conductive tape 20 is relatively high. On the other hand, a form in which the core wire 10 includes a plurality of insulated electric wires is preferable in that the damage D can be detected for the entire assembly of the insulated electric wires. The 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) in the middle as shown in FIG. 9.

[0076] 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 in a state of contacting the surface of the insulating coating 12 of the core wire 10. In the electric wire 1 according to this first example, 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 exposed without being covered by the conductive tape 20. Regarding the shape of the conductive tape 20, the tape body is distinguished from a linear body such as a metal wire, and refers to a sheet-like member whose thickness is smaller than its width. In addition, the conductive tape 20 is maintained in a state where the turns of the spiral shape are not in direct contact with each other due to the gaps 25, and are not in contact with each other via other conductive members. Therefore, no other conductive members, such as a metal braid, are provided around the outer periphery of the conductive tape 20.

[0077] The conductive tape 20 may be in the form of a conductive foil (all conductive tape) made of a conductive material such as a metal material, or may be a substrate formed as a tape-shaped insulator or semiconductor, on whose surface a conductive layer made of a conductive material such as a metal material is formed. The conductive layer may be formed only on one surface of the substrate (single-sided conductive tape), or may be formed on both surfaces of the substrate (double-sided conductive tape). When using a single-sided conductive tape, the conductive layer may be wound around the core wire 10 so that it faces either the inside or the outside. When the conductive layer faces the surface opposite to the surface that contacts the core wire 10 (the surface that is the outside of the electric wire 1), it is excellent in terms of high sensitivity for damage detection, while when the conductive layer faces the surface that contacts the core wire (the surface that is the inside of the electric wire 1), it is excellent in terms of ease of ensuring conduction with members arranged inside the conductive tape, such as a drain wire. When using a double-sided conductive tape, unlike the laminated tape 40 described later, the two conductive layers may be either mutually insulated or mutually conductive.

[0078] In all cases of the fully conductive tape, the single-sided conductive tape, and the double-sided conductive tape, the type of conductive 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 the oxidation of the metal material becomes serious, it may become impossible to accurately detect external damage, which utilizes the conductivity of the conductive tape 20 as part of its principle, so it is preferable not to use iron or iron alloy as the metal material constituting the conductive tape 20. The type of the substrate constituting the single-sided conductive tape and the double-sided conductive tape is also not particularly limited, but a tape body made of an insulator such as an organic polymer material can be preferably used. 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 to cause damage D1 that is deep and large enough to cause breakage or, even if it does not cause breakage, to cause a change in the capacitance between the conductive tape 20 and the conductor 11 due to the expected damage D to the electric wire 1. On the other hand, it is preferable that the conductive tape 20 has a sufficient thickness to exhibit 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, it is preferable to wind the conductive tape 20 at a sufficiently coarse pitch, i.e., at a sufficiently large pitch, and with the width of the gap 25 being 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, it is preferable to form the pitch of the spiral shape 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, particularly in cases where the layer is so thin that it is easily damaged by contact with or friction against another object.

[0082] In the electric wire 1, the structure in which the conductive tape 20 is roughly wound 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 in which the conductive tape 20 is provided over the entire area is preferable in that the damage D can be detected regardless of the location along the axial direction of the electric wire 1, and the form in which the conductive tape 20 is provided over only a part of the area is preferable in that 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 wind the conductive tape 20 around 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), the conductive tape 20 may be provided including the 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 at a first time point is compared with that at a second time point to determine whether or not a damage D has been formed on the electric wire 1 at the second time point. More preferably, the position at which the damage D has been formed along the axial direction of the electric wire 1 is also specified.

[0086] 10, in the electric wire inspection, a measuring device 9 (corresponding to the inspection unit A1) is appropriately connected to the base end 1A of the electric wire 1 to measure 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 that is continuous around the entire circumference of the core wire 10 and along the axial direction. 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 occupies a large area along the axial direction, and damage D1 occurs in the conductive layer 120 around almost the entire circumference and along the axial direction, 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 and is also long and continuous in the axial direction, the proportion of the damage D1 in the entire conductive layer 120 becomes small, so that the rate of change in capacitance (the rate 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 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, and each spiral turn of the conductive tape 20 is separated by a gap 25 along the axial direction of the core wire 10, when the damage D1 is formed in the conductive tape 20 as shown in FIG. 6B, the proportion of the area occupied by the damage D1 becomes large with respect to the area covered by the conductive tape 20 in the initial state. 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 partial region along the circumferential direction of the electric wire 1, if the damage D forms damage D1 in the conductive tape 20, this 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 is increased.

[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 characteristic impedance measurement result at a first time point and the characteristic impedance measurement result at a second time point after some time has passed from the first time point is calculated, and the area where the difference value changes discontinuously from the values ​​in the surrounding areas is detected as a 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 any type of electric wire, and may have the above-described single wire structure, or may be in the form of a composite electric wire (wire harness) including a plurality of insulated electric wires each having an insulating coating 12 provided on the outer periphery of a conductor 11. When the core wire 10 is in the form of a composite electric wire, the conductive tape 1 is wound around the entire outer periphery of the composite electric wire.

[0100] The embodiment in which the core wire 10 is in the state of a composite electric wire is preferable in that the formation of damage on the outer circumference of the composite electric wire as a whole can be detected sensitively and easily, regardless of the specific configuration of the composite electric wire, such as the shape and thickness of the composite electric wire, and the type of insulated electric wire contained therein. On the other hand, the embodiment in which the core wire 10 has a single-wire structure is characterized by the importance of the role of the conductive tape 20 in measuring the characteristic impedance. That is, when the core wire includes multiple conductive members, such as in the case of a shielded cable or a paired cable, it is possible to detect the external damage D by measuring the characteristic impedance between multiple conductive members constituting the core wire, such as between the center conductor and the shielding conductor, or between the paired wires, as described above as embodiment (i). However, in the case of a single-wire structure, the core wire 10 only has the conductor 11 as a conductive member, so that the external damage D can be detected using the characteristic impedance only by wrapping the conductive tape 20 around the outside. In addition, in the case of a single-wire structure, wrapping the conductive tape 20 around the core wire is excellent in the effect of reducing the influence of noise and enabling the external damage D to be detected with high sensitivity. That is, in the case of a shielded cable or a paired cable, a stable characteristic impedance is easily obtained because of the inherent structure for reducing the effects of noise, whereas in the case of a single-wire structure, the characteristic impedance between the conductor 11 and the earth potential is very unstable. However, 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, the characteristic impedance is stabilized. By detecting the external damage D in such a state where the characteristic impedance is stable, a change in the characteristic impedance value can be detected with high sensitivity and associated with the formation of the external damage D.

[0101] Furthermore, as described above, the conductive tape 20 is distinguished from a linear body, 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 linear body such as a metal wire is wound spirally around the outer periphery of the core wire 10 instead of the conductive tape 20, it may be possible to achieve detection of the damage D. However, when a linear body is used, the difference in capacitance between the portion where the conductive material is arranged and the portion where the conductive material 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 linear body such as a metal wire is used.

[0102] 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 DC current or 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 current or voltage to conductor 1.

[0103] (Conductive tape-wrapped electric wire according to the second example) Next, a conductive tape-wrapped electric wire 1' according to the second example will be briefly described. Here, a description of the configurations common to the conductive tape-wrapped electric wire 1 according to the first example and the effects thereof will be omitted, and a brief description will be given. Also, the conductive tape-wrapped electric wire 1' according to the second example can be subjected to the same wire inspection method as that of the conductive tape-wrapped electric wire 1 according to the first example.

[0104] 11A and 11B show a perspective view and a cross section cut perpendicular to the axial direction of the conductive tape-wrapped electric wire 1' according to the second example, respectively. In the conductive tape-wrapped electric wire 1 according to the first example, the conductive tape 20 is wound around the outer periphery of the core wire 10 with gaps 25 between the turns, whereas in the conductive tape-wrapped electric wire 1' according to the second example, the conductive tape 20' is wound around the outer periphery of the core wire 10 in a spiral shape with no gaps between the turns. The conductive tape 20' is a one-sided conductive tape in which the conductive layer 21 is formed only on one side of the substrate 22. In the spiral shape of the conductive tape 20', the conductive layer 21 is kept in a state where it does not contact with each other between adjacent turns. As described above, the conductive tape 20' may be arranged so that the conductive layer 21 faces either inward or outward with respect to the core wire 10, but in the illustrated embodiment, it is wound around the surface opposite to the surface in contact with the core wire 10, i.e., the conductive layer 21 faces outward.

[0105] In the conductive tape-wrapped electric wire, the conductive tape 20' may be wound so that there is no overlap between the spiral turns, as long as the conductive tape 20' is wound without gaps, or may be wound so that a part of the width of the conductive tape 20' overlaps between adjacent turns as shown in FIG. 11B. From the viewpoint of reliably winding the conductive tape 20' without gaps, the latter form in which there is an overlap between the turns is preferable. However, in either case, it is necessary to maintain the conductive layers 21 in a state where they do not come into contact with each other between the turns. By using a single-sided conductive tape as the conductive tape 20', it is possible to easily maintain a state in which the conductive layers 21 do not come into contact with each other even if the conductive tape 20' is overlapped between the turns, as long as the conductive tape 20' is not twisted or folded.

[0106] As described above with reference to Figures 7A and 7B, if the conductive layer 120 is provided around the outer periphery of the core wire 10, and is long and continuous in the axial direction, even if a scratch is formed on a part of the outer periphery of the wire, the scratch will only occupy a small part of the area of ​​the large, integral, continuous layer 120 of the conductive material. Therefore, the rate of change in capacitance due to the scratch is small, and as a result, the rate of change in characteristic impedance due to the scratch is also small. However, in the conductive tape-wrapped electric wire 1' according to the second example described here, although the conductive layer 21 covers the outer periphery of the core wire 10 around the entire periphery and without gaps in the axial direction, the conductive layers 21 are kept in a state of not contacting each other between the spiral turns, so that the continuity of the conductive layer 21 along the axial direction of the core wire 10 is interrupted between the turns.

[0107] Therefore, when a scratch is formed only in a part of the outer circumference of the electric wire 1' and the conductive layer 21 is damaged, if the scratch occupies a certain area within one turn of the conductive layer 21, the rate of change in capacitance becomes large, and accordingly, the characteristic impedance also changes to a certain extent. Therefore, even in the conductive tape-wrapped electric wire 1' according to the second example, the scratch can be detected sensitively by the change in characteristic impedance. Moreover, by measuring the characteristic impedance by the TDR method or the FDR method, not only the presence or absence of the scratch can be determined, but also the position where the scratch is formed can be specified along the axial direction of the electric wire 1'. Furthermore, since the conductive tape 20' is densely wrapped around the outer circumference of the core wire 10 without any gaps, the scratch can be detected by the change in characteristic impedance with stable sensitivity regardless of the position where the scratch is formed along the circumferential and axial directions of the electric wire 1', and high spatial uniformity can be obtained in the scratch detection. In particular, even when it is assumed that a wound occupying only a short length area is formed as the wound, the wound can be detected with high accuracy regardless of the position where the wound is formed.

[0108] In this way, the conductive tape-wrapped electric wire 1 according to the first example in which the conductive tape 20 is wound roughly, and the tape-wrapped electric wire 1' according to the second example in which the conductive tape 20' made of a single-sided conductive tape is wound without gaps can both sensitively detect the formation of a wound injury through changes in characteristic impedance, and furthermore, the position of the wound injury can be specified by applying the TDR method or the FDR method. However, the electric wire 1 according to the first example has gaps 25 between the turns of the conductive tape 20, so that it is more excellent in the sensitivity of detecting the injury and the accuracy of specifying the position of the injury. On the other hand, the electric wire 1' according to the second example has the conductive tape 20 wound around the outer periphery of the core wire 10 without gaps, so that it is particularly excellent in the spatial uniformity of the injury detection. A specific winding form of the conductive tape may be set so that the advantages of each form can be effectively utilized. For example, the more suitable electric wire for the application may be selected from the two types of electric wires 1, 1' having different winding methods of the conductive tape, depending on the expected size and formation location of the injury, the required detection sensitivity, and the like.

[0109] (Example of attaching conductive tape to composite wire) As described above, in the conductive tape-wrapped electric wire 1, 1', the core wire around which the conductive tapes 20, 20' are wound may have a single wire structure or may be in the form of a composite electric wire (wire harness) including a plurality of insulated electric wires. A simple example of a composite electric wire will be given below. FIG. 12 shows, in a cross-sectional view, a conductive tape-wrapped electric wire 1" in a form in which a conductive tape 20' is wound around the outer periphery of a core wire 10" made of a composite electric wire, similarly to the conductive tape-wrapped electric wire 1' according to the second example described above. Here, it is assumed that the conductive tape-wrapped electric wire 1" is configured as a composite electric wire for an electric brake with a damage detection function, and a measuring device 9 is constantly connected to the electric wire 1" to continuously monitor the condition of the core wire 10" made of the composite electric wire.

[0110] In the conductive tape-wrapped electric wire 1' shown in FIG. 12, the insulated electric wires constituting the core wire 10" include at least one of a power supply line and a communication line. More specifically, the core wire 10" may be configured as a composite twisted electric wire including a power supply line and a communication line for an electric brake device of an automobile. In the illustrated embodiment, the core wire 10" has four insulated electric wires 1a to 1d. Of the four, two are power supply lines 1a, 1b. The other two are communication lines 1c, 1d, which are twisted together to form a twisted pair. The twisted pair wire consisting of the two power supply lines 1a, 1b and the pair of communication lines 1c, 1d is twisted together as a whole. In addition, the core wire 10" may include a disconnection detection line 1e in an area surrounded by the four insulated electric wires 1a to 1d, and may also include a drain wire 1f at the outermost portion. The break detection wire 1e is an insulated wire that includes a conductor that is less flex-resistant than the conductors of the insulated wires 1a to 1d and is more likely to break when bent, and breakage of the break detection wire 1e makes it possible to detect signs of breakage in the insulated wires 1a to 1d. The drain wire 1f is configured as a conductor wire that is not covered with an insulator, and comes into contact with the conductive tape 20' wrapped around the outer periphery of the core wire 10" at any position along the axial direction to ensure conductivity.

[0111] A conductive tape 20' is wound around the outer periphery of the core wire 10". In the illustrated embodiment, a single-sided conductive tape having a conductive layer 21 and a substrate 22 is wound around the entire periphery of the core wire 10" without any gaps and such that the conductive layer 21 does not come into contact between turns. The conductive layer 21 faces the surface that comes into contact with the core wire 10" (the inner side of the electric wire 1"). However, as in the conductive tape-wrapped electric wire 1 according to the first example described above, any of the entire conductive tape, the single-sided conductive tape, and the double-sided conductive tape may be wound with gaps between pitches. Optionally, a pressure winding layer 1g in which an insulating tape is wound may be formed around the outer periphery of the conductive tape 20'. A sheath 1h is formed as an extrusion molded body of insulating resin around the outer periphery of the pressure winding layer 1g. In the illustrated embodiment, the sheath 1h is formed of two layers, an inner layer 1h1 and an outer layer 1h2.

[0112] In the electric wire 1" having the conductive tape 20' wound around the outer circumference of the core wire 10" made of this composite electric wire, the conductive tape 20' is electrically connected to a measuring unit attached to the electric brake device, and the characteristic impedance is monitored constantly or frequently. In this case, the characteristic impedance 20' may be measured between the conductive layer 21 of the conductive tape 20' and another conductive material included in the electric wire 1', such as the conductor of any one of the insulated electric wires 1a to 1d and the disconnection detection line 1e. If damage occurs to the power lines 1a and 1b or the communication lines 1c and 1d constituting the electric brake device, it may have a significant effect on the brake system and even the entire automobile. However, by continuously monitoring the formation of damage by measuring the characteristic impedance using the conductive tape 20', it is possible to detect the formation of damage or the occurrence of a sign of the formation of damage at an early stage. Then, by appropriately notifying the driver of the automobile, it is possible to suppress the effects of the damage or to prevent it from occurring. Furthermore, by measuring the characteristic impedance by the TDR method or the FDR method, the position where the trauma or a sign of the trauma has occurred can be identified along the axial direction of the electric wire 1''.

[0113] In addition, when the disconnection detection wire 1e is disposed in the core wire 10", the characteristic impedance of the disconnection detection wire 1e is monitored, and when a sign of disconnection occurs in any of the insulated electric wires 1a to 1d constituting the core wire 10", the disconnection detection wire 1e, which has a low bending resistance of the conductor, is detected to break first, thereby making it possible to detect the sign of disconnection of the insulated electric wires 1a to 1d in advance. In this case as well, by applying the TDR method or the FDR method, the position where the sign of disconnection has occurred can be specified along the axial direction of the electric wire 1". In this way, by using the conductive tape 20' for detecting external damage in combination with the disconnection detection wire 1e for detecting signs of disconnection, it is possible to detect signs of disconnection of the conductor in addition to external damage among various types of damage that can be formed in the electric wire, and further to specify the position where the sign has occurred.

[0114] [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.

[0115] (Structure of laminated tape-wrapped electric wire) FIG. 13A shows a schematic perspective view of the laminated tape-wrapped electric wire 3. In the laminated tape-wrapped electric wire 3, the laminated tape 40 is wound in a spiral shape around the outer periphery of the core wire 30. As with the conductive tape 20, the laminated tape 40 may be wound around the outer periphery of a core wire having a single wire structure, or around the outer periphery of the core wire 30 in a state of a composite electric wire (wire harness) including a plurality of insulated electric wires. However, as shown in FIG. 13A, it is preferable that the laminated tape 40 is wound around the entire outer periphery of the core wire 30 configured as a composite electric wire including a plurality of insulated electric wires 31. 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 insulated electric wires 31 (wire bundle), or may be wrapped around the outer periphery of an exterior material such as a tube after the wire bundle is housed in the exterior material.

[0116] 13B, the cross-sectional view (cross-section perpendicular to the tape longitudinal direction) of 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).

[0117] 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 21 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, causing a change in impedance.

[0118] 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 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 causes breakage, short circuit, etc., and a change in characteristic impedance occurs sufficiently. The two coating layers 42, 42 are kept insulated from each other.

[0119] 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 wound state around the outer periphery of the core wire 30 including the multiple insulated electric wires 31. When the laminated tape 40 is directly wound around the outer periphery of the core wire 30 which is a bundle of multiple insulated electric wires 31, if the laminated tape 40 is arranged to hold down the bundle of electric wires via the adhesive tape 43, the laminated tape 40 may serve both as a damage detector and as a bundling material that prevents the bundle of electric wires from coming apart.

[0120] 13A and 13B, 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.

[0121] In the electric wire with laminated tape 3, the laminated tape 40 is wound in a spiral shape around the outer periphery of the core wire 30 configured as a composite electric wire. In this case, as in the case of the conductive tapes 20, 20' in the above-mentioned conductive tape-wrapped electric wires 1, 1', the laminated tape 40 may be wound without leaving any gaps between the turns of the spiral structure, or may be wound with a gap narrower than the expected length of damage. However, in the case of the laminated tape 40, unlike the conductive tapes 20, 20', improvement in damage detection sensitivity by leaving a gap between the turns cannot be expected, so from the viewpoint of improving spatial uniformity of detection, it is preferable to wind the laminated tape 40 without leaving any gaps. In this case, from the viewpoint of accurately measuring the characteristic impedance between the two coating layers 42, 42, it is preferable to keep the coating layers 42, 42 of the laminated tape 40 from contacting each other between the turns. In other words, it is preferable to prevent contact between the same coating layers (between the outer coating layers or the inner coating layers) and between different coating layers (between the outer coating layer and the inner coating layer) of the two coating layers 42, 42 from occurring between turns. The layer of the laminated tape 40 is preferably exposed on the outer surface of the laminated tape-wrapped electric wire 3 as a whole.

[0122] (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 a wire inspection. In the wire inspection, damage that occurs in the coating layers 41, 41 of the laminated tape 40 is directly detected, but the purpose of the wire inspection is to use the damage in the coating layers 41, 41 as an indicator to detect the formation of external damage in the core wire 30 (or each insulated electric wire 31) or the onset of a warning sign that external damage is about to occur.

[0123] 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.

[0124] 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.

[0125] In this way, the characteristic impedance between the two conductive coating layers 42, 42 constituting the laminated tape 40 is measured as the electric wire inspection, and the characteristic impedance obtained as the response signal is compared between the first time point and the second time point, so that damage can be detected in the core wire 30 (or each insulated electric wire 31) around which the laminated tape 40 is wound. In other words, if there is a difference between the characteristic impedance at the first time point and the second time point, it can be detected that the core wire 30 (or each insulated electric wire 31) 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 shape, 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] Unlike the conductive tape-wrapped electric wire 1 described above, the laminated tape-wrapped electric wire 3 does not use components of the core wire 30 as the damage detection part, but instead uses only components of the laminated tape 40 provided separately from the core wire 30 to form the damage detection part. The laminated tape 40 used here has a more complex tape structure than the conductive tape 20 described above, but by not using components of the core wire 30 as the damage detection part, it is possible to impart a damage detection function regardless of the type or shape of the insulated electric wire 31 that constitutes the core wire 30. In other words, as long as the laminated tape 40 can be wrapped around the outer periphery, a damage detection part can be formed for insulated electric wires of various structures and types, and for composite electric wires including multiple insulated electric wires. For example, in an electric wire 1" having a core wire 10" made of the composite electric wire shown in FIG. 12, a preferred example is one in which the laminated tape 40 is wrapped around the outer periphery of the core wire 10" instead of the conductive tape 20'. Furthermore, damage detection using the laminated tape 40 does not utilize the constituent members of the core wire 30. Therefore, when the laminated tape 40 is wrapped around any long member other than an electric wire or a composite electric wire, it can be used to detect damage to that member in the same manner as described above. EXAMPLES

[0130] Examples are shown below, but the present invention is not limited to these examples.

[0131] [1] Conductive tape-wrapped wire First, we confirmed whether damage to conductive tape-wrapped wires could be detected by measuring the characteristic impedance.

[0132] [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.

[0133] (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 wound around the outer circumference of the core wire in a rough spiral shape with gaps between the pitches 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 gaps not occupied by the conductive tape was approximately 1:1.

[0134] 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.

[0135] (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.

[0136] (result) As an example, Fig. 14 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. 14 and Figs. 15 to 16C 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.

[0137] Looking at the measurement results in Figure 14, 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, the formation of a trauma can be detected, and furthermore, the position of the trauma can be identified with high accuracy.

[0138] Furthermore, FIG. 15 shows a number of measurement results when the position where the simulated trauma is formed is changed. The trauma is formed at the position (distance from the base end) described in the legend corresponding to the symbol in the graph. According to FIG. 15, 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 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.

[0139] [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.

[0140] (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.

[0141] (Injury detection) As in the above test [1-1], the characteristic impedance was measured using the MCTDR method.

[0142] (result) Fig. 16A shows the measurement results when no injury was formed. On the other hand, Fig. 16B 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.

[0143] Comparing the state without a wound in Figure 16A with the state with a wound in Figure 16B, very similar patterns of measurement results were obtained in both cases. An upward peak not present in Figure 16A is seen near the wound site indicated by an asterisk in Figure 16B, 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.

[0144] Figure 16C shows the difference between the measurement results in Figures 16A and 16B. This difference was obtained by subtracting the characteristic impedance value before the lesion was formed in Figure 16A from the characteristic impedance value after the lesion was formed in Figure 16B. The difference display in Figure 16C shows that the peak structure that was prominent in the short-distance region in the measurement results in Figures 16A and 16B has disappeared. On the other hand, an upward peak remains clearly at the lesion formation position indicated by a star.

[0145] 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.

[0146] [2] Laminated tape-wrapped electric wire Finally, we confirmed whether damage detection was possible for laminated tape-wrapped electric wires.

[0147] (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.

[0148] 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.

[0149] (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 set to Z0 at the undamaged location and Z at the damaged location. L Then, the reflection coefficient ρ is expressed by the following equation (1). ρ = (Z L -Z0) / (Z L +Z0) (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.

[0150] (result) First, the results when a break is formed in the copper tape as an external injury are confirmed. FIG. 17A shows the measurement results of the reflection coefficient in the normal state before the break is formed, and FIG. 17B shows the state after the break is formed. In FIG. 17A to 17C, 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. 17B, 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. 17A. FIG. 17C 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.

[0151] Next, we will examine the results when a short circuit is formed in the copper tape as an external injury. Figure 18A shows the measurement results of the reflection coefficient in a normal state before the short circuit is formed, and Figure 18B shows the state after the short circuit is formed. In the measurement result after the short circuit is formed in Figure 18B, 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 18A. Figure 18C 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.

[0152] 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.

[0153] 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]

[0154] 1,1',1” Conductive tape wrapped wire 1a,1b power line 1c,1d communication line 1e Disconnection detection line 1f Drain wire 1g Pressure winding layer 1h Sheath 1h1 Inner layer 1h2 outer layer 1A Base end of wire 10,10' core wire 10" core wire (composite wire) 11 Conductor 12 Insulation coating 13A~13C Branching section 14 Main Line 15A~15C branch line 20 Conductive Tape 20' Conductive Tape (single-sided conductive tape) 21 Conductive layer 22 Base material 25 Gap 3. Laminated tape-wrapped wire 30 core wire (composite wire) 31 Insulated wire 40 Laminated Tape 41 Base material 42 Covering layer 43 Adhesive Tape 9. Measurement Equipment A Electrical Wire Inspection System A1 Inspection Department A2 storage section A3 Analysis Department C,C' Electric wire Cp1~Cp6 Points on wire C c1 Response signal of wire C' at the first time c2 Response signal of wire C' at the second time point D Trauma D1 Damage to conductive tape P Peak R Change area S1~S4 Each step of the wire inspection method

Claims

1. An electric wire inspection system for inspecting a damage state of an electric wire, comprising: The electric wire is It is configured as a composite electric wire for electric brakes with a damage detection function, A core wire having a conductor and an insulating coating, the core wire including at least one of a power line and a communication line of an electric brake device of an automobile; a damage detection unit having two electrically insulated conductive members, the two conductive members being composed of at least one of a component of the core wire and a member other than the core wire arranged along the core wire; The electric wire inspection system includes an inspection unit, a storage unit, and an analysis unit, the damage detection unit is a measuring device that integrally comprises the functions of the inspection unit, the storage unit, and the analysis unit, and is constantly electrically connected to a measuring unit attached to the electric brake device, the inspection unit performs an electric wire inspection at a first time point and a second time point after the first time point, the electric wire inspection inputting an electric signal including an AC component as an inspection signal and acquiring a characteristic impedance between the two conductive members as a response signal by a time domain reflectometry or a frequency domain reflectometry; The storage unit stores the response signal obtained by the electric wire inspection by the inspection unit at the first time point, the analysis unit performs an analysis step of retrieving the response signal at the first time point from the storage unit, comparing it with the response signal acquired in the electric wire inspection by the inspection unit at the second time point, and, if a difference exists between the two response signals, associating a region in the response signal in which the difference exists with a position along an axial direction of the electric wire; the inspection unit is kept connected to the two conductive members constituting the damage detection unit of the electric wire, and the electric wire inspection is always in a state in which it is possible to carry out the electric wire inspection, and the response signal is input from the inspection unit to the memory unit and the analysis unit, and the memory unit stores data that has received the input, and the analysis unit analyzes the data, an inspection unit that performs the inspection of the electric wire repeatedly at all times, or automatically performs the inspection of the electric wire at predetermined time intervals, or each time an apparatus equipped with the electric wire performs a predetermined operation, and the inspection unit stores the response signal at the first time point that is used in the analysis process, and the response signal is updated by re-storing the newly acquired response signal in the memory unit as the inspection of the electric wire is repeated.

2. 2. The electrical wire inspection system according to claim 1, 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.

3. 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; 3. The electric wire inspection system according to claim 1, wherein in the electric wire inspection, a characteristic impedance between the two conductive members is measured as the response signal by a time domain reflectometry.

4. 4. The electric wire inspection system according to claim 3, wherein in the inspection signal, the excluded frequency includes a frequency of an electromagnetic wave originating from a source external to the electric wire and propagating around the electric wire.

5. The electric wire inspection system according to claim 1 , wherein the electric wire to be inspected has a branch portion midway.

6. The electric wire to be inspected has a conductive tape wound in a spiral shape around the outer periphery of the core wire, The electric wire inspection system according to claim 1 , wherein the damage detection unit is configured with the conductor of the core wire and the conductive tape as the two conductive members.

7. The conductive tape has a conductive layer made of a conductive material formed on one surface of a base material formed as a tape-shaped insulator or semiconductor, The wire is wound around the core wire in a spiral shape without any gaps.

7. The electrical wire inspection system of claim 6, wherein in the helical configuration, the conductive layers between adjacent turns do not contact each other.

8. The core wire is in the form of a composite electric wire including a plurality of insulated electric wires each having the insulating coating provided on the outer periphery of the conductor, 8. The electric wire inspection system according to claim 6, wherein the conductive tape is wound in a spiral shape around an outer periphery of the composite electric wire as a whole.

9. The electric wire to be inspected has a laminated tape disposed around the outer periphery of the core wire, The laminated tape is a tape-shaped insulator or semiconductor substrate having conductive coating layers formed on both sides thereof, The electric wire inspection system according to claim 1 , wherein the damage detection unit is configured such that the two coating layers of the laminated tape serve as the two conductive members.

10. The core wire is in the form of a composite electric wire including a plurality of insulated electric wires each having the insulating coating provided on the outer periphery of the conductor, The electric wire inspection system according to claim 9 , wherein the laminated tape is spirally wound around an outer periphery of the composite electric wire as a whole.

11. The laminated tape is wound around the outer periphery of the core wire in a spiral shape without any gaps, 11. The electric wire inspection system according to claim 9 or 10, wherein the coating layer is not in contact between turns in the spiral shape.

12. The electric wire inspection system according to claim 9 , wherein the electrical characteristics of the base material change depending on an external environment.

13. The electric wire inspection system according to claim 1 , wherein the predetermined operation is activation of a brake.

14. Using the electric wire inspection system according to any one of claims 1 to 13, an initial data acquiring step of performing the electric wire inspection on the electric wire by the inspection unit 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 in the storage unit; a measuring step of performing the electric wire inspection on the 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 from the memory unit, compares it with the response signal acquired in the measurement step at the second time point, and, if a difference exists between the two response signals, associates an area in the response signal where the difference occurs with a position along the axial direction of the electric wire.

15. A core wire formed as a composite electric wire in which a plurality of insulated electric wires each having a conductor and an insulating coating covering the outer periphery of the conductor are twisted together; A conductive tape as a detection tape body arranged on an outer periphery of the core wire as the entire composite electric wire, The conductive tape has a conductive layer made of a conductive material formed on one surface of a base material formed as a tape-shaped insulator or semiconductor, the conductive tape is wound in a spiral shape around the outer periphery of the core wire, with gaps between adjacent turns remaining unoccupied by the conductive tape; In the spiral shape, the conductive layers between adjacent turns are not in contact with each other, and the spiral pitch is 1 / 3 or less of the allowable bending radius of the electric wire, The electric wire is configured as a composite electric wire for an electric brake with a damage detection function, The insulated electric wire is an electric wire including at least one of a power line and a communication line of an electric brake device of an automobile, The detection tape body is constantly electrically connected to a measuring unit attached to the electric brake device.

16. A core wire formed as a composite electric wire in which a plurality of insulated electric wires each having a conductor and an insulating coating covering the outer periphery of the conductor are twisted together; a laminated tape as a detection tape body arranged on an outer periphery of the core wire as the entire composite electric wire, 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 wire is wound around the core wire in a spiral shape without any gaps. In the spiral shape, the coating layers between adjacent turns are not in contact with each other, The electric wire is configured as a composite electric wire for an electric brake with a damage detection function, The insulated electric wire is an electric wire including at least one of a power line and a communication line of an electric brake device of an automobile, A method of using an electric wire, wherein the detection tape body is constantly electrically connected to a measuring unit attached to the electric brake device.

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