Inspection system and inspection method

Abstract

To easily inspect defects in a plurality of electric wires.SOLUTION: An inspection system 1 includes a pulse generation device 11 that applies a pulse to an object T including a plurality of electric wires; an input-side switch 13 that is connected to the object T and the pulse generation device 11 and sequentially inputs the pulse applied by the pulse generation device 11 to each of the plurality of electric wires; an output-side switch 14 that is connected to the object T and an oscilloscope 12, is sequentially connected to each of the plurality of electric wires, and sequentially inputs a reflected waveform caused by the pulse on each of the plurality of electric wires to the oscilloscope 12; and the oscilloscope 12 that observes the reflected waveform of each of the plurality of electric wires.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to an inspection system and an inspection method. [Background technology]

[0002] In the wire harness production process, continuity tests are performed to ensure product quality. Meanwhile, in the coaxial cable manufacturing process, wire breaks can occur due to excessive pressure from band clips. In the continuity test process, it is possible to eliminate wires that are completely broken.

[0003] Another method for inspecting electrical wires is TDR (Time Domain Reflectometry). TDR applies a pulse directly to an electrical wire and observes the reflected waveform to determine the state of the transmission line. For example, Patent Document 1 discloses that in non-destructive testing using TDR, a signal transmission line switching means is used to switch to a signal transmission line for fault analysis, which has a longer electrical wire length than a normal signal transmission line, thereby widening the distance between the connection points of the front and back stages of the board and improving resolution. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-197999 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the production process of an object to be inspected, such as a wire harness, defects such as scratches on the wires that do not result in breakage may occur.

[0006] Wire scratches cannot be eliminated by continuity testing because they still have continuity. However, to ensure quality, it is necessary to detect defects such as wire scratches in advance. TDR is suitable for detecting defects that do not result in a break in the wire, but in the case of a wire harness, it can be a burden to connect a pulse generator and oscilloscope to each of the multiple wires in the target object.

[0007] The present invention has been made in view of the problems inherent in the conventional techniques, and an object of the present invention is to provide an inspection system and an inspection method that can easily inspect a plurality of electric wires for defects. [Means for solving the problem]

[0008] An inspection system according to one aspect of the present invention includes a pulse generator that applies a pulse to an object having a plurality of electric wires, an input-side switch that connects the object to the pulse generator and inputs the pulse applied by the pulse generator to each of the plurality of electric wires in sequence, an output-side switch that connects the object to an oscilloscope and connects to each of the plurality of electric wires in sequence and inputs the reflected waveform of the pulse from each of the plurality of electric wires to the oscilloscope in sequence, and an oscilloscope that observes the reflected waveform of each of the plurality of electric wires.

[0009] In another aspect of the inspection method of the present invention, for each electric wire of an object, an input-side switch connecting the object to a pulse generator connects the pulse generator to the electric wire, the pulse generator applies a pulse to the electric wire, and then an output-side switch connecting the object to an oscilloscope connects the oscilloscope to the electric wire, and the oscilloscope repeats the process of observing the reflected waveform on the electric wire. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an inspection system and an inspection method that can easily inspect a plurality of electric wires for defects. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a diagram illustrating an inspection system according to an embodiment of the present invention. [Figure 1B] FIG. 2 is a diagram illustrating an example of an object to be inspected by the inspection system. [Figure 2] FIG. 1 is a diagram illustrating a TDR inspection system. [Figure 3] FIG. 2 is a diagram illustrating an example of a wire harness that is an object. [Figure 4] 1 is a diagram illustrating an example in which a short circuit occurs in a wire harness that is an object. FIG. [Figure 5] 4A and 4B are diagrams illustrating an example of a pulse signal applied to each electric wire by a pulse generator. [Figure 6] 10A and 10B are diagrams illustrating an example of a reflected waveform obtained by applying a pulse signal from a pulse generator. [Figure 7] 10A and 10B are diagrams illustrating an example of a pulse signal applied to each electric wire by a pulse generator and a waveform observed by an oscilloscope. [Figure 8] 10A and 10B are diagrams illustrating an example of the operation of an input-side switch and an output-side switch. [Figure 9] 1 is a diagram illustrating an example of a state in which a wire harness is broken but is not short-circuited with an adjacent wire; [Figure 10] FIG. 10 is a diagram illustrating an example of a reflected waveform when two electric wires in a wire harness are disconnected but not short-circuited. [Figure 11] FIG. 1 is a diagram illustrating an example of a state in which two electric wires in a wire harness are broken and short-circuited. [Figure 12] FIG. 10 is a diagram illustrating an example of a reflected waveform when two electric wires in a wire harness are broken and short-circuited. [Figure 13] 1 is a diagram illustrating an example of a state in which one electric wire in a wire harness is broken and short-circuits with an adjacent electric wire. FIG. [Figure 14]10A and 10B are diagrams illustrating an example of a reflected waveform when one electric wire in a wire harness is broken and short-circuits to an adjacent electric wire. [Figure 15] 10A and 10B are diagrams illustrating an example of a reflected waveform when the coating of an electric wire is damaged. [Figure 16] FIG. 10 is a diagram illustrating a reflected waveform when crosstalk occurs between two electric wires. [Figure 17] 10 is a flowchart illustrating an inspection method. DETAILED DESCRIPTION OF THE INVENTION

[0012] The inspection system 1 according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the sake of explanation and may differ from the actual ratios.

[0013] (Inspection System) The inspection system 1 shown in Fig. 1A inspects an object T. In this embodiment, the object T is a wire harness or the like, and includes a plurality of electric wires. Although the object T in Fig. 1A will be described as including four electric wires as shown in Fig. 1B, the number of electric wires may be any number.

[0014] The inspection system 1 according to this embodiment uses TDR to inspect each electric wire of the object T. The inspection system 1 according to this embodiment checks the continuity of each electric wire, as well as the length of the wire and the state of damage to the wire.

[0015] A typical TDR testing system 2 will be explained with reference to Figure 2. TDR is a method widely used to measure characteristic impedance. TDR is introduced in references such as EDN Japan's "Understanding the Basics of TDR Measurement" (https: / / edn.itmedia.co.jp / edn / articles / 0712 / 01 / news017.html). TDR applies a high-speed pulse or step signal to an electric wire or printed circuit board wiring, and observes the reflected waveform that returns. This reflected waveform indicates the change in characteristic impedance of the electric wire, etc.

[0016] The TDR inspection system 2 includes a pulse generator 11 and an oscilloscope 12 .

[0017] The pulse generator 11 applies a pulse to the target T. The pulse generator 11 has a function as a step generator capable of generating a pulse with a rise time of 10 ps to 30 ps.

[0018] The oscilloscope 12 observes the reflected waveform of the pulse applied by the pulse generator 11 in the electric wire of the target object T. The oscilloscope 12 is preferably a sampling oscilloscope having high time resolution.

[0019] In this embodiment, the wire harness of the object T is designed and manufactured according to the drawings, and the specifications of the electric wires to be inspected are known. The electric wire specifications include the diameter and length of each electric wire included in the object T.

[0020] Figure 3 shows an example of object T. Object T shown in Figure 1B is a simplified version of a typical wire harness, illustrating an example of a wire harness with four wires. Actual wire harnesses have a more complex structure than the one shown in Figure 1B, including many more wires and connectors. Object T has three terminals: connector A, connector B, and connector C. The object shown in Figure 3 has 10 wires. As shown in Table 1, the 10 wires include 0.13 sq wires, 0.35 sq wires, 0.5 sq wires, and 0.75 sq wires. The 0.13 sq wires come in three lengths: 3000 mm, 2500 mm, and 1500 mm. The 0.35 sq wires come in one length: 3000 mm. The 0.5 sq wires come in one length: 2500 mm. The length of the 0.75sq wire is 2500mm.

[0021] [Table 1]

[0022] Between connector A and connector B, wires α, β, γ, and δ are connected. Between connector A and connector C, wires ε and ζ are connected. Between connector B and connector C, wires η, θ, ι, and κ are connected.

[0023] When conducting continuity tests and TDR tests, connectors A, B, and C are connected to C / Fs (checker fixtures) corresponding to connectors A, B, and C, respectively. In this embodiment, C / Fs include C / Fa, C / Fb, and C / Fc, which are connected to connectors A, B, and C, respectively. Connector A connects to C / Fa, connector B connects to C / Fb, and connector C connects to C / Fc.

[0024] In the example of Fig. 1B, object T is a wire harness consisting of four electric wires. In the examples of Fig. 1A and Fig. 1B, object T has connectors A, B, and C. In Fig. 1A, C / F includes C / Fa, C / Fb, and C / Fc. C / Fa, C / Fb, and C / Fc are respectively connected to connectors A, B, and C of the object's wire harness.

[0025] The inspection system 1 according to this embodiment uses a TDR inspection method to inspect for defects in an object T that do not result in a break. As shown in FIG. 4, assume that the coating of an electric wire α of the object T is broken at the position marked "x." If only the coating is broken and the electric wire α is not broken, the coating break will not be detected by a continuity inspection. Furthermore, if the electric wire α does not short-circuit with an adjacent electric wire, the coating break will not be detected by a short-circuit inspection either.

[0026] However, after the wire harness, which is the object T, is installed in a vehicle, this broken coating may lead to a disconnection. The broken coating may also connect to the vehicle earth and cause a short circuit with the earth.

[0027] Therefore, the inspection system 1 according to this embodiment uses a TDR inspection method to grasp the wire length and transmission path status of each electric wire in an object T such as a wire harness, and detects defects that do not lead to disconnection.

[0028] In the present disclosure, the inspection system 1 repeats the process of applying a pulse and observing the reflected waveform for each electric wire. Specifically, the inspection system 1 applies a pulse and observes the reflected waveform for a first electric wire, and then applies a pulse and observes the reflected waveform for a second electric wire. The inspection system 1 repeats the application of a pulse and the observation of the reflected waveform for each electric wire of the object T, and then ends the process.

[0029] As shown in FIG. 1, the inspection system 1 according to this embodiment includes a pulse generator 11, an oscilloscope 12, an input-side switch 13, an output-side switch 14, a control device 21, and a determination device 22.

[0030] The pulse generator 11 and the oscilloscope 12 are as described with reference to Fig. 2. The pulse generator 11 sequentially applies pulses to each of the multiple electric wires included in the object T. The oscilloscope 12 observes the reflected waveforms of the pulses applied by the pulse generator 11 from each of the multiple electric wires included in the object T.

[0031] The input-side switch 13 connects the object T and the pulse generator 11. The input-side switch 13 is, for example, an analog switch. The input-side switch 13 connects the pulse generator 11 to one of the multiple electric wires provided in the object T. The input-side switch 13 connects to each of the multiple electric wires provided in the object T by switching the connection destination. The input-side switch 13 branches the pulse signal applied by the pulse generator 11 and applies it to one of the electric wires of the object T. The input-side switch 13 inputs the pulse applied by the pulse generator 11 sequentially to each of the multiple electric wires of the object T.

[0032] The output switch 14 connects the object T and the oscilloscope 12. The output switch 14 is, for example, an analog switch. The output switch 14 connects the oscilloscope 12 to one of the multiple electric wires provided in the object T. The output switch 14 connects to each of the multiple electric wires provided in the object T by switching the connection destination. The output switch 14 switches the reflected waveform of a pulse signal from any one of the electric wires to a signal to the oscilloscope 12. The output switch 14 sequentially connects to each of the multiple electric wires of the object T. The output switch 14 sequentially inputs the reflected waveform of a pulse from each of the multiple electric wires to the oscilloscope 12.

[0033] In this embodiment, the terminals of the input switch 13 on the side of the object T are referred to as IN1, IN2, IN3, etc. If the input switch 13 has n terminals on the side of the object T, the nth terminal is referred to as INn. The terminals of the output switch 14 on the side of the object T are referred to as OUT1, OUT2, OUT3, etc. If the output switch 14 has n terminals on the side of the object T, the nth terminal is referred to as OUTn.

[0034] In this embodiment, the electric wire connected to IN1 and OUT1 is referred to as electric wire E1. Similarly, the electric wire connected to IN2 and OUT2 is referred to as electric wire E2. The electric wire connected to IN3 and OUT3 is referred to as electric wire E3. The electric wire connected to INn and OUTn is referred to as electric wire En.

[0035] An example of switching of the input-side switch 13 and the output-side switch 14 is shown in Table 2. When the pulse generator 11 applies a pulse to the target T, the input-side switch 13 is open and the output-side switch 14 is closed. When the oscilloscope 12 observes the reflected waveform, the input-side switch 13 is closed and the output-side switch 14 is open. In Table 2, "open" means "energized" and "closed" means "not energized."

[0036] [Table 2]

[0037] The control device 21 controls the processing in the inspection system 1. The control device 21 transmits control signals to the input-side switch 13 and the output-side switch 14 at predetermined timing.

[0038] The control device 21 controls the input-side switch 13 and the output-side switch 14 so that the oscilloscope 12 can successively observe the reflected waveform of each electric wire. After the pulse signal generated by the pulse generator 11 is applied to each electric wire of the object T, the control device 21 controls the operation of the input-side switch 13 and the output-side switch 14 taking into account the length of each electric wire so that the oscilloscope 12 can observe the reflected waveform of each electric wire.

[0039] When the inspection of the second electric wire is completed, the control device 21 controls the inspection of each electric wire provided in the object T, such as the third electric wire, the fourth electric wire, . . .

[0040] The control device 21 repeatedly switches the terminal to which the input switch 13 is connected on the side of the target T and the terminal to which the output switch 14 is connected on the side of the target T. This allows the inspection system 1 to apply a pulse to each electric wire and observe the reflected waveform of each electric wire.

[0041] The timing at which the control device 21 transmits the control signal is merely an example and is not limited thereto. For example, when the pulse generator 11 applies a pulse to the target T, it may transmit a control signal to each of the input switch 13 and the output switch 14, which corresponds to the sequence of operations and timing of each switch. The sequence of operations is an operation for applying a pulse to each electric wire and observing the reflected waveform of each electric wire. In this case, the timers of the input switch 13 and the output switch 14 are synchronized.

[0042] The determination device 22 displays the reflected waveform observed by the oscilloscope 12 and analyzes the reflected waveform to estimate a defect in the electric wire. The determination device 22 may be realized by installing a program that executes predetermined processing in a general computer that includes a storage device, a processor, etc.

[0043] The timing of the pulse signals applied to each wire will be described with reference to FIG.

[0044] 5 shows pulse signals applied to each of the electric wires E1, E2, E3, and En. With respect to the reference start time t0, the electric wire E1 applies a pulse signal for Δt at time t1, which is delayed by T1 hours from t0. The electric wire E2 applies a pulse signal for Δt at time t2, which is delayed by T2 hours from t0. The electric wire E3 applies a pulse signal for Δt at time t3, which is delayed by T3 hours from t0. The electric wire En applies a pulse signal for Δt at time tn, which is delayed by Tn hours from t0. The pulse signals applied to each electric wire are branched by the input-side switch 13, so that the time t0 for each of the electric wires E1, E2, E3, and En is the same.

[0045] A pulse signal is applied to each electric wire at a time delayed by a predetermined time from the reference start time t0, and therefore it is possible to determine from which electric wire the reflected wave originates based on the start time of the reflected wave.

[0046] The reflected waveform obtained when a pulse signal is reflected within an electric wire will be explained with reference to Figure 6. The example in Figure 6 shows a state in which a wire harness made up of a bundle of electric wires is measured with a predetermined characteristic impedance.

[0047] In Figure 6, the vertical axis represents characteristic impedance and the horizontal axis represents propagation time. The wire length is calculated from the propagation time. In Figure 6, the length in the time direction indicated by D corresponds to the wire length of the wire being inspected for the object T. There is a positive correlation between the length of the wire being inspected and the length of D.

[0048] The example in Figure 6 shows a state where the wire has no breaks or scratches. When measuring an actual wire harness, the waveform is rarely flat like part D in Figure 6. Depending on the wiring condition of the wire harness, part D may become a wavy waveform. Here, in TDR evaluation, it is important that no sudden changes in the waveform occur in part D. This is because a wire harness is made up of a bundle of wires, and therefore metal is not uniformly adjacent to the wire being inspected. On the other hand, if a sudden change in the waveform occurs in part D, it is determined that a break or scratch has occurred in the wire.

[0049] There are peaks in the characteristic impedance on both sides of part D in Figure 6. The two peaks in the characteristic impedance are the characteristic impedance of the coaxial cable connected to the output from pulse generator 11 and the coaxial cable connected to the input to oscilloscope 12. The characteristic impedance of the coaxial cable is 50 Ω. The rising part to the left of the left peak of the characteristic impedance and the processed part to the right of the right peak are each the characteristic impedance of the connecting connector.

[0050] The oscilloscope 12 observes the reflected wave of the pulse signal on the electric wire. The measurement end can be terminated at 50 Ω, open, or shorted. If there are no problems with the equipment, a 50 Ω termination or open is preferable. This is because it makes it easier to see where the waveform ends. This section D varies depending on the diameter or material of the electric wire. As a rough guide, a propagation time of 5 nsec corresponds to a wire length of 1 m.

[0051] In this embodiment, the wire configuration and specifications of the wire harness to be inspected, as well as the wire diameter and material of each wire, are known. The determination device 22 may store the characteristic impedance of each wire and compare it with the reflected waveform observed by the oscilloscope 12.

[0052] Referring to Figure 7, the reflected waveform of the pulse signal applied to each electric wire by the pulse generator 11 will be described. Each reflected waveform shown in Figure 7 is in a state where no defects such as disconnection, scratches, crosstalk, etc. have occurred. In Figure 7, the length of each electric wire is as follows: electric wire E3 length > electric wire E1 length > electric wire E2 length > electric wire En length. The time D corresponding to each electric wire in each reflected waveform is D3 > D1 > D2 > Dn.

[0053] In this embodiment, for the sake of explanation, the reflected waveforms of the pulse signals applied to each wire are plotted on the same time axis in accordance with the expected behavior of the control signal. In reality, the input waveform is not visible on the oscilloscope 12 due to the timing of the opening and closing of the input switch 13 and the output switch 14. As shown in FIG. 1 and other figures, in this embodiment, the input waveform is reflected and becomes the output waveform. The time at which this input waveform is observed is designated as t0, and the time at which a certain output waveform is observed is designated as tn. The input switch 13 and output switch 14 shown in FIG. 1 are switched so that the signal from the pulse generator 11 reaches the target T at time t0. At this time, the output switch 14 is "closed," so the input waveform cannot be observed on the oscilloscope 12.

[0054] As shown in Figure 7, the pulse generator 11 applies a pulse signal to the electric wire E1 at time t1. A reflected wave is generated immediately after time t1. The oscilloscope 12 can observe a delay time D1 for the electric wire E1. The delay time D1 corresponds to the length of the electric wire E1.

[0055] The pulse generator 11 applies a pulse signal to the electric wire E2 at time t2, which is ΔT after time t1. A reflected wave is generated immediately after time t2. The oscilloscope 12 can observe a delay time D2 for the electric wire E2. The delay time D2 corresponds to the length of the electric wire E2.

[0056] The pulse generator 11 applies a pulse signal to the electric wire E3 at time t3, which is ΔT after time t2. A reflected wave is generated immediately after time t3. The oscilloscope 12 can observe a delay time D3 for the electric wire E3. The delay time D3 corresponds to the length of the electric wire E3.

[0057] Pulse generator 11 applies a pulse signal to each electric wire at intervals of ΔT. If the propagation time of the electric wire is approximately 5 nsec / m and the maximum wire length of the electric wires in the wire harness is 20 m, the pulse signal applied by pulse generator 11 will be at intervals of 100 nsec.

[0058] The correlation between the input-side switches 13 and the output-side switches 14 will be described with reference to Fig. 8. In Fig. 8, the number of wires n is set to 4, and the number of switches is set to 4 for inputs and 4 for outputs.

[0059] When a pulse signal is applied to wire E1, input switch 13 connects to IN1. After input switch 13 connects to IN1 for Δt, output switch 14 connects to OUT1, and input switch 13 opens the connection to IN1. The same applies to wires E2, E3, and En. While the pulse signal is being applied, input switch 13 connects to the wire to be applied. While output switch 14 connects to the wire to be observed, and the reflected waveform is observed on oscilloscope 12, input switch 13 opens the connection.

[0060] (If the wire is broken and there is no short circuit with the adjacent wire) 9 and 10, a case where there is a complete break in the wire and no short circuit with adjacent wires will be described. The inspection system 1 applies a pulse signal from connector A. As shown in FIG. 9, wire α and wire β are broken at a point 2000 mm from connector A.

[0061] In the case of Figure 9, as shown in Figure 10, a constant characteristic impedance cannot be maintained in section D, which is the design value. The characteristic impedance suddenly rises to infinity at d', where the break occurs. If there is a break but no short circuit with adjacent wires, the characteristic impedance will not be affected by the multiple surrounding wires. Since wires α and β produce similar waveforms with respect to the time of the pulse signal, Figure 10 omits and shows only one waveform. The determination device 22 can detect the break, its location, and whether or not there is a short circuit from the reflected waveform.

[0062] 11 and 12, we will explain the case where there is a complete break in the wire and a short circuit with an adjacent wire. The inspection system 1 applies a pulse signal from connector A. When there is a short circuit with an adjacent wire, there are two cases: (i) as shown in FIG. 11, where there is a short circuit on the connector A side but not on the connector B side, and (ii) where there is a short circuit on the connector B side but not on the connector A side.

[0063] As shown in Figure 11, (i) if there is a short on connector A and no short on connector B, the area more than 2000 mm from connector A will be OPEN. If there is no short, the delay time will be D, but since there is a short at a position 2000 mm from connector A, the delay time will be shortened to d'.

[0064] In the case of Fig. 11, when a pulse signal is applied to the electric wire α at time t1 and a pulse signal is applied to the electric wire β at time t2, if the electric wires α and β are short-circuited, reflected waveforms with a short delay time d' are observed from each of the electric wires α and β, as shown in Fig. 12. In this way, the determination device 22 can detect a break, the position of the break, the presence or absence of a short circuit, and the state of the short circuit from the reflected waveforms.

[0065] On the other hand, (ii) if there is a short on connector B but not on connector A, the inspection result from connector A will be the same as a simple open circuit. The reflected waveforms shown in Figure 10 are obtained from both wire α and wire β.

[0066] As shown in Figure 13, there are cases where wire α is not broken, but wire β is broken at the "x" point and short-circuited to wire α. When viewed from connector A, terminal A1 of connector A should normally connect only to B1 of connector B, but in the example of Figure 13, terminal A1 connects to terminals B1 and B2 on the connector B side.

[0067] In the case of Figure 13, the electric wire α is shorted at a position 2000 mm from connector A, so a reflected waveform with a short delay time d' is observed, as shown in Figure 14. The electric wire β is connected to terminal A2 of connector A and both terminals B1 and B2 of connector B and is open, so a normal reflected waveform with a delay time D is observed. From the reflected waveform, the determination device 22 can detect a break, the position of the break, the presence or absence of a short, and the state of the short.

[0068] (If the wire is damaged) When an electric wire has a scratch, there are two cases: (i) the scratch is only on the coating and the core wire is not scratched, and (ii) the scratch is on both the coating and the core wire.

[0069] (i) In the case of a scratch on the coating, specifically, if there is a scratch only on the coating but not on the core wire, the spacing between the core wires in the bundle of electric wires will be locally narrowed. In this case, as shown in Figure 15, the characteristic impedance will be lower at the time corresponding to the location of the scratch on the coating than at a location where there is no scratch on the coating. (ii) If there are scratches on both the coating and the core wire, the core wire diameter will be locally narrowed. In this case, the characteristic impedance will be higher at the time corresponding to the location of the scratch on the core wire than at a location where there is no scratch on either the coating or the core wire. The determination device 22 can detect the presence or absence of scratches on the coating and the core wire, and if there is a scratch, the location of the scratch from the reflected waveform.

[0070] (if crosstalk is present) The reflected waveform when there is crosstalk between the electric wires E1 and E2 will be described with reference to Fig. 16. Normally, the electric wires E1 and E2 affect each other through crosstalk, but Fig. 16 describes a case where the electric wire E1 does not affect the electric wire E2 through crosstalk, but the electric wire E2 affects the electric wire E1 through crosstalk.

[0071] Because wire E2 has a crosstalk effect on wire E1, a pulse of less than half the power is induced in wire E1 at time t2. In this state, the reflected waveforms shown at the bottom of Figure 16 are obtained from wires E1 and E2. The delay time D remains the same for each reflected waveform, and the delay time D corresponds to the length of wires E1 and E2. Furthermore, because wire E2 has a crosstalk effect on wire E1, the characteristic impedance of the reflected waveform is halved. The determination device 22 can detect crosstalk noise between the two wires from the reflected waveforms from each of the two wires.

[0072] Table 3 shows an example of the test results when a general continuity test is performed simultaneously using the test system 1 according to this embodiment. In Table 3, "wire length OK" means that "the wire length determined by the TDR test is as specified." In Table 3, "predetermined characteristic impedance" means that "the characteristic impedance of the wire being tested is a normal value." For example, the normal value of the characteristic impedance of a coaxial wire is 50 Ω. The normal value of the characteristic impedance of a twisted wire is 120 Ω. The normal value of the characteristic impedance of the wire being tested is measured in advance from normal sample data.

[0073] [Table 3]

[0074] As shown in Table 3, if the specified characteristic impedance is met and the design line length is observed, the result is OK. If the specified characteristic impedance is met but the line length observed is less than the design line length, the result is NG, as it is assumed that the line length at the point of disconnection has been observed. If the characteristic impedance falls outside the specified range and the line length observed is less than the design line length, the result is NG, as it is assumed that there is a short circuit with another line and the line length at the point of disconnection has been observed.

[0075] If a specified location has a higher characteristic impedance than specified, while other locations have the specified characteristic impedance, and the designed wire length is observed, the insulation is deemed to have been cut or the core wire is compressed at the location where the higher characteristic impedance than specified is observed, and the result is NG. If a specified location has a variation in characteristic impedance, while other locations have the specified characteristic impedance, and the designed wire length is observed, the insulation is deemed to have been cut or damaged at the location where the variation is observed, and the result is NG. If the designed wire length is not observed, the wire is deemed to be inappropriate, even though it is conductive, and the result is NG.

[0076] Note that Table 3 does not mention whether crosstalk occurs or not. During a continuity test of a wire harness, crosstalk often occurs because the electric wires are often adjacent and in close contact. However, in this embodiment, a normal judgment can be made even when crosstalk occurs.

[0077] An ID (Identifier) ​​is attached to the wire under test. There are various ways to attach an ID, but one example is to regard the pulse timing as a bit. An example of pulse timing is shown in Table 4.

[0078] [Table 4]

[0079] For example, when the pulse shown in Figure 5 is applied to the wire harness shown in Figure 4, the pulse arrives at wire α at time t1, and the pulse arrives at wire β at time t2. The ID of each wire is expressed as the timing at which the pulse arrives, with 1 being the time when the pulse is applied and 0 being the time when it is not applied, using 16 bits. This is just an example, and the ID may be expressed using a number of bits other than 16. If there are a large number of wires, the number of bits can be increased. Furthermore, the method of assigning IDs to wires is not limited to this method.

[0080] In the "ID Status" column of Table 3, "Normal Read" means that the ID set in the pulse timing bit was read, in other words, the timing for reading the characteristic impedance was appropriate.

[0081] (Testing method) The inspection method according to this embodiment will be described with reference to Fig. 17. In the inspection method, the processes from step S1 to step S4 are repeated for each electric wire included in the object. When the object T includes four electric wires E1-E4, the inspection system 1 executes processing for the electric wire E1, then for the electric wire E2, for the electric wire E3, and for the electric wire E4, and then ends the processing. Note that the inspection system 1 is not limited to executing processing for all electric wires included in the object T, and may execute processing for some of the electric wires included in the object T. The some electric wires may be, for example, electric wires specified by an operator, or electric wires that satisfy predetermined conditions.

[0082] In step S1, the input-side switch 13 connects the pulse generator 11 to the electric wire to be inspected. The control device 21 transmits a control signal to the input-side switch 13 to connect the pulse generator 11 to the electric wire E1. At this time, the control device 21 transmits a control signal to the output-side switch 14 to disconnect the oscilloscope 12 from the electric wire E1.

[0083] In step S2, the pulse generator 11 applies a pulse to the electric wire to be inspected.

[0084] In step S3, the output-side switch 14 connects the oscilloscope 12 to the electric wire under test. The control device 21 sends a control signal to the output-side switch 14 to connect the oscilloscope 12 to the electric wire E1. At this time, the control device 21 sends a control signal to the input-side switch 13 to disconnect the connection between the pulse generator 11 and the electric wire E1.

[0085] In step S4, the oscilloscope 12 observes the reflected waveform from the electric wire under test.

[0086] When the processes from step S1 to step S4 are completed for each electric wire included in the object T, the process of the inspection method ends.

[0087] This inspection method allows multiple wires to be inspected sequentially.

[0088] 5, the pulse generator 11 applies pulse signals to each electric wire at equal time intervals, but this is not limiting. The pulse generator 11 may apply pulse signals to each electric wire irregularly. In this case, the control device 21 may associate the identifier of each electric wire with the time at which the pulse signal is applied to that electric wire. The identifier of the electric wire may be the terminal number of the connector to which the electric wire is connected.

[0089] The control device 21 or the determination device 22 may also store wire details for each wire, including wire specifications such as terminal part numbers, wire diameters, and wire lengths.

[0090] 5, a case where one pulse signal is applied to each wire has been described, but this is not limiting. For example, one pulse may be input to wire E1, two pulses to wire E2, and three pulses to wire E3. This makes it easy to identify which wire the waveform observed by oscilloscope 12 was observed on.

[0091] The inspection system 1 according to this embodiment can inspect the object T for defects that do not lead to a break, such as scratches on an electric wire. The inspection system 1 can identify the location where a break or a defect that does not lead to a break has occurred.

[0092] Furthermore, the inspection system 1 can sequentially inspect multiple electric wires at different times by switching the connections of the input switch 13 and the output switch 14. This eliminates the need to reconnect each of the multiple electric wires included in the object T to the inspection system, as in the case of a wire harness. The inspection system 1 can easily inspect the object T for defects.

[0093] Thus, the inspection system 1 according to the first aspect of this embodiment comprises a pulse generator 11 that applies a pulse to an object T having a plurality of electric wires, an input-side switch 13 that is connected to the object T and the pulse generator 11 and that inputs the pulse applied by the pulse generator 11 to each of the plurality of electric wires in sequence, an output-side switch 14 that is connected to the object T and an oscilloscope 12 and that is connected to each of the plurality of electric wires in sequence and that inputs the reflected waveform of the pulse from each of the plurality of electric wires in sequence to the oscilloscope 12, and an oscilloscope 12 that observes the reflected waveform of each of the plurality of electric wires.

[0094] In the inspection system 1, the input switch 13 connects the pulse generator 11 to the first electric wire. After the pulse generator 11 applies a pulse to the first electric wire, the output switch 14 connects the first electric wire to the oscilloscope 12, and the oscilloscope 12 may observe the waveform reflected on the first electric wire.

[0095] In the inspection system 1, after the oscilloscope 12 observes the reflected waveform on the first electric wire, the input-side switch 13 may connect the pulse generator 11 to the second electric wire.

[0096] The inspection system 1 may further include a determination device 22 connected to the oscilloscope 12, and the determination device 22 may detect a defect in the coating of the electric wire from the reflected waveform.

[0097] The inspection system 1 may further include a determination device 22 connected to the oscilloscope 12, and the determination device 22 may detect crosstalk noise between the two electric wires from the reflected waveforms on each of the two electric wires.

[0098] In the inspection method according to the second aspect of this embodiment, for each electric wire provided in the object T, an input switch 13 connecting the object T to a pulse generator 11 connects the pulse generator 11 to the electric wire, the pulse generator 11 applies a pulse to the electric wire, and then an output switch 14 connecting the object T to an oscilloscope 12 connects the oscilloscope 12 to the electric wire, and the oscilloscope 12 repeats the process of observing the reflected waveform in the electric wire.

[0099] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0100] 1. Inspection system 11 Pulse generator 12 Oscilloscope 13 Input side switch 14 Output switch 21 Control device 22 Judgment device T object

Claims

1. a pulse generator that applies pulses to an object having a plurality of electric wires; an input-side switch connected to the object and the pulse generator, for sequentially inputting pulses applied by the pulse generator to each of the plurality of electric wires; an output-side switch connected to the object and an oscilloscope, and connected to each of the plurality of electric wires in sequence, for inputting reflected waveforms of the pulses from each of the plurality of electric wires in sequence to the oscilloscope; an oscilloscope for observing the reflected waveforms of each of the plurality of electric wires; An inspection system comprising:

2. the input-side switch connects the pulse generator to a first electric wire; After the pulse generator applies a pulse to the first electric wire, the output switch connects the oscilloscope to the first electric line; The inspection system of claim 1 , wherein the oscilloscope observes a reflected waveform on the first electrical wire.

3. After the oscilloscope observes the reflected waveform on the first electric wire, The inspection system according to claim 2 , wherein the input-side switch connects the pulse generator to a second electric wire.

4. Further comprising a determination device connected to the oscilloscope, The inspection system according to claim 1 , wherein the determination device detects a defect in the coating of the electric wire from the reflected waveform.

5. Further comprising a determination device connected to the oscilloscope, The inspection system according to claim 1 , wherein the determination device detects crosstalk noise between the two electric wires from reflected waveforms on each of the two electric wires.

6. For each electric wire equipped in the object, an input-side switch connected to the object and a pulse generator connects the pulse generator and the electric wire; After the pulse generator applies a pulse to the electric wire, an output-side switch that connects the object and an oscilloscope connects the oscilloscope and the electric wire; The inspection method includes repeating a process in which the oscilloscope observes the waveform reflected from the electric wire.

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