Disconnection detection device

Abstract

To provide a disconnection detection device capable of easily detecting disconnection of a cable wired to a device.SOLUTION: A disconnection detection device 1 detects disconnection of an element wire of a cable 2 that has a conductor composed of multiple element wires and is wired to a management object device by operation of the management object device, and includes a detection section 3 for applying a detection signal to a conductor 21 and measuring a resistance value of the conductor 21 that changes in time series by operation of a movable section, a disconnection determination section 413 for determining disconnection of an element wire on the basis of a measurement result of the resistance value of the conductor 21, and signal route switching means 7 that is provided in both the ends of the cable 2 and suppresses a flow of a detection signal to a connection destination of the cable 2 in the management object device.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wire break detection device. [Background technology]

[0002] In cables wired to moving parts of equipment such as industrial robots, the wires that make up the conductor gradually break due to repeated bending, twisting, and other movements of the moving parts, and ultimately lead to a break in the conductor. Therefore, it is desirable to detect the break in the wires and replace the cable before the entire conductor breaks.

[0003] However, when the number of broken wires that make up the conductor is small, the change in the resistance value of the conductor is so slight that it cannot be distinguished from noise. For this reason, in the past, it was often determined that a wire had broken when the resistance value of the conductor rose by several tens of percent from its initial value. In this case, however, there was little time (or number of operations) between the detection of a broken wire and the conductor being completely broken, and there was a risk that the conductor would break before the cable could be replaced.

[0004] Patent Document 1 proposes a method for detecting wire breakage based on the results of measuring the resistance of the conductor when the cable is operated (bent, twisted, etc.) at a constant cycle and analyzing the fluctuations in the resistance using frequency analysis. This method has high sensitivity, making it possible to detect wire breakage even when, for example, only one wire is broken. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2021-162570 A Summary of the Invention [Problem to be solved by the invention]

[0006] When detecting whether the conductor of a cable that is the subject of breakage detection has been broken, it is desirable to be able to detect a break in the conductor without removing the cable itself from the device to which the cable is wired (a managed device such as an industrial robot) or removing the motors, sensors, drive circuits, or control devices connected to both ends of the cable wired to the device, in order to reduce the effort required for performing breakage detection and to enable breakage detection to be performed frequently.

[0007] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a cable disconnection detection device that can easily detect a disconnection in a cable wired to an apparatus. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a wire break detection device having a conductor composed of a plurality of wires, which detects that the wire of a cable wired to a managed device is broken due to the operation of the managed device, the wire break detection device comprising: a detection unit that applies a detection signal to the conductor and measures the resistance value of the conductor, which changes over time due to the operation of the managed device; a wire break determination unit that determines whether the wire is broken based on the measurement result of the resistance value of the conductor; and a signal path switching means that is provided at both ends of the cable and prevents the detection signal from flowing to a connection destination of the cable in the managed device. Effect of the Invention

[0009] According to the present invention, it is possible to provide a disconnection detection device that can easily detect a disconnection in a cable wired to an apparatus. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a wire break detection device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a diagram illustrating the principle of disconnection detection. [Diagram 3] 4(a) and 4(b) are circuit diagrams showing an example of a detection unit. [Figure 4] 1 is a flow diagram of a disconnection detection method according to an embodiment of the present invention. [Diagram 5] FIG. 13 is a schematic configuration diagram of a wire breakage detection device according to a modified example of the present invention. [Figure 6] FIG. 13 is a schematic configuration diagram of a wire breakage detection device according to a modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] FIG. 1 is a schematic diagram of a wire breakage detection device 1 according to the present embodiment. As shown in FIG. 1, the wire breakage detection device 1 is used to detect a wire breakage in a cable 2 wired to a device (=a device to be managed) such as an industrial robot. The cable 2 is wired to a device having a moving part, such as an industrial robot, so as to pass through the moving part. The cable 2 also has a conductor 21 made of a stranded conductor in which a plurality of elemental wires are twisted together. The plurality of elemental wires are made of metal wires made of copper, copper alloy, aluminum, aluminum, or the like. The surface of the metal wire may be covered with tin plating or silver plating.

[0013] In the illustrated example, a first connector 12 is provided at one end of the cable 2, and the one end of the cable 2 is connected to a motor 10 via the first connector 12. A second connector 13 is provided at the other end of the cable 2, and the other end of the cable 2 is connected to an inverter circuit 11 via the second connector 13. The cable 2 has four conductors 21 corresponding to the U-phase (U), V-phase (V), W-phase (W) and ground (GND). The disconnection detection device 1 detects a disconnection of each conductor 21 of the cable 2. More specifically, the disconnection detection device 1 detects a disconnection of the wires constituting each conductor 21.

[0014] Hereinafter, "breakage of a wire" means that each of the wires constituting the conductor of the cable 10 is broken. In addition, "breakage progression state of the conductor" means the breakage ratio, i.e., the number of broken wires among the number of wires constituting the conductor, due to repeated bending, twisting, and other operations applied to the cable 10. The breakage progression state of the conductor can be expressed as the ratio (%) of the number of broken wires to the total number of wires constituting the conductor. For example, the breakage progression state of a wire constituting the conductor indicates that all of the wires constituting the conductor are broken when the breakage ratio is 100%. In other words, the breakage progression state of the conductor can be said to be the breakage progression state of the cable 10.

[0015] Moreover, "conductor breakage" means that the conductor breakage rate reaches a preset rate and reaches a state where it is determined that the conductor has broken. For example, the state where it is determined that the conductor has broken is set to when the resistance increase rate (the rate of increase in the resistance value of the conductor relative to the initial resistance value of the conductor) of the conductor constituting the cable 10 exceeds 20%, and the conductor breakage rate (= the progress of the conductor breakage) at this time is, for example, 80% or more. Conductor breakage indicates the time when it is determined that the cable 10 has reached the end of its life (= the cable life), and serves as a guide for encouraging replacement of the cable 10.

[0016] (Principle of disconnection detection) First, the principle of disconnection detection in this embodiment will be described. Fig. 2 is a schematic diagram for explaining the principle of disconnection detection in this embodiment. In the example of Fig. 2, it is assumed that a disconnection occurs at a portion (referred to as disconnection portion 2a) in an element wire of conductor 21 included in cable 2. Fig. 2 shows the resistance value of conductor 21 when it is reciprocated in a bending angle range of +90° to -90°, assuming such a disconnection state. The operating frequency f is 0.5 Hz.

[0017] As shown in FIG. 2, when the bending angle is +90°, the distance between the wires at the break point 2a becomes shorter than when the bending angle is 0°, and the resistance value decreases. On the other hand, when the bending angle is -90°, the distance between the wires at the break point 2a becomes longer than when the bending angle is 0°, and the resistance value increases. In this way, the distance between the wires at the break point 2a varies depending on the bending operation, and the resistance value of the conductor 21 varies accordingly. That is, the resistance value is modulated by the operating frequency f. On the other hand, when no break occurs, the change in the resistance value ideally does not include a component that changes with the operating frequency f.

[0018] Therefore, the resistance value of the conductor 21, which changes over time in response to the operation of the movable part, is measured, and the component of the operating frequency f is extracted from the frequency components included in the time-series change in the resistance value of the conductor 21. As a result, the time point when the component of the operating frequency f occurs can be regarded as the time point when an initial break occurs, that is, when a break occurs in the first wire among the multiple wires that make up the conductor 21. In other words, from a different perspective, it becomes possible to detect the occurrence of a break in at least the wires, including the initial break, based on whether or not the component of the operating frequency f occurs at each time point (for example, whether or not the magnitude of the component is equal to or greater than a preset threshold). In addition, it becomes possible to extract a breakage rate indicating how many of the multiple wires have been broken, and to determine whether or not the conductor has reached a breakage state based on whether or not the breakage rate is equal to or greater than a preset threshold.

[0019] (Disconnection detection device 1) The disconnection detection device 1 includes a detection section 3, a calculation device 4 having a disconnection determination section 413, and a signal path switching means 7. Each of the components will be described in detail below.

[0020] (Detection unit 3) When the device (particularly the movable part) performs an operation to check the progress of a disconnection in the conductor 21, that is, when detecting a disconnection of the multiple wires that make up the conductor 21, the detection part 3 applies a detection signal to the conductor 21 and measures the resistance value of the conductor 21 that changes over time due to the operation of the movable part. In this embodiment, the detection part 3 is mounted on the second connector 13 on the inverter circuit 11 side. However, the present invention is not limited to this, and the detection part 3 may be mounted on a dedicated module or the like provided separately from the second connector 13.

[0021] The detection unit 3 has an output terminal (MOD_OUT) 3a that outputs a detection signal, a sensor terminal (SENS) 3b for current detection, a ground terminal (GND) 3c for grounding, and a test terminal (TEST) 3d that outputs a switching signal for controlling a relay 7a described later. The detection unit 3 outputs a detection signal of a preset voltage from the output terminal (MOD_OUT) 3a, and detects a resistance value (i.e., the resistance value of the conductor 21 that changes over time) based on a current flowing between the sensor terminal (SENS) 3b and the ground terminal (GND) 3c. The detection unit 3 transmits the detected resistance value of the conductor 21 that changes over time to the calculation device 4.

[0022] FIG. 3(a) is a circuit diagram showing an example of the detection unit 3. As shown in FIG. 3(a), the detection unit 3 includes, for example, a signal source (for example, a constant voltage source) 35a that generates a detection signal, an input resistor 35b, and a resistance value detector 35c. When a constant current source is used as the signal source 35a, the input resistor 35b is not necessary. The signal source 35a is connected to an output terminal (MOD_OUT) 3a via an input resistor 35b, and a detection signal is output from the output terminal (MOD_OUT) 3a. A modulated signal (a modulated signal including a component of an operating frequency f (=0.5 Hz) in the example of FIG. 3) modulated by the operation of the movable part is input between the sensor terminal (SENS) 3b and the ground terminal (GND) 3c. The resistance value detector 35c detects a time-series change in the resistance value of the conductor 21, for example, by amplifying the modulated signal with a predetermined gain. The output signal from the resistance value detector 35c is converted into a digital signal by the A / D converter 37 and then output to the calculation device 4, and is stored in the memory unit 42 of the calculation device 4 as resistance value data 421.

[0023] The specific configuration of the detection unit 3 is not limited to the example shown in Fig. 3(a) and can be changed as appropriate. For example, as shown in Fig. 3(b), the detection unit 3 may be configured to include a lock-in amplifier that detects a specific frequency component from the measurement signal. The detection unit 3 shown in Fig. 3(b) includes a frequency analysis unit 36.

[0024] The frequency analysis unit 36 ​​includes, for example, a carrier signal generator 36a, a mixer 36b, and a low-pass filter (LPF) 36c. The carrier signal generator 36a generates a carrier signal having the same carrier frequency (ωc, 0.5 Hz in the case of FIG. 2) as the operating frequency f, that is, the resistance value fluctuation frequency due to a disconnection, and the same phase as the resistance value fluctuation frequency. The mixer 36b multiplies (in other words, performs synchronous detection) this carrier signal by the output signal from the resistance value detector 35c, thereby outputting a signal in which a DC component signal and a "2×ωc" component signal are superimposed. Note that, in the carrier signal generator 36a shown in FIG. 3(b), sin(ωct) can extract the resistance value fluctuation component of the operating frequency f when ωc=2πf.

[0025] The low-pass filter 36c receives the output signal from the mixer 36b, blocks the signal of the "2×ωc" component, and passes the signal of the DC component. This DC component signal represents the magnitude of the resistance value fluctuation component of the operating frequency f (=ωc). In this way, the basic configuration of a lock-in amplifier is to detect the component of a predetermined frequency (here, the operating frequency f) using the carrier signal generator 36a, mixer 36b, and low-pass filter 36c. The signal from the low-pass filter 36c is converted into a digital signal by the A / D converter 37 and output to the calculation device 4.

[0026] 3(b), a desired frequency component (for example, a component of the operating frequency) can be extracted from the time-series change in the resistance value of the conductor 21, and the detection unit 3 can play the same role as the frequency analysis unit 411 and the extraction unit 412 described later. In this case, the frequency analysis unit 411 and the extraction unit 412 in the calculation device 4 can be omitted. The detection unit 3 is not limited to the configuration using a lock-in amplifier as in FIG. 3(b), and may be configured to extract the component of the operating frequency f using, for example, an actual band pass filter (BPF).

[0027] (Signal path switching means 7) The signal path switching means 7 are provided at both ends of the cable 2, and perform branching and merging of a signal conducted through the conductor 21 when the device is in operation (hereinafter referred to as a device use signal) and a detection signal.

[0028] In this embodiment, the signal path switching means 7 is mounted on the connectors 12 and 13 provided at both ends of the cable 2. Hereinafter, the signal path switching means 7 mounted on the first connector 12 is referred to as the first signal path switching means 71, and the signal path switching means 7 mounted on the second connector 13 is referred to as the second signal path switching means 72. The first signal path switching means 71 passes the device use signal from the cable 2 to the motor 10 side, and passes the detection signal from the cable 2 to the detection unit 3 side. That is, the first signal path switching means 71 suppresses the device use signal from passing to the detection unit 3 side, and suppresses the detection signal from passing to the motor 10 side. The second signal path switching means 72 passes the device use signal from the inverter circuit 11 to the cable 2 side, and passes the detection signal from the detection unit 3 to the cable 2 side. That is, the second signal path switching means 72 suppresses the device use signal from passing to the detection unit 3 side, and suppresses the detection signal from passing to the inverter circuit 11 side.

[0029] In this embodiment, both the first signal path switching means 71 and the second signal path switching means 72 are formed of relays 7a capable of switching the connection destination of the cable 2 to the detection unit 3. The relay 7a is configured to switch the connection destination in response to a switching signal from the detection unit 3. The relay 7a is configured to connect the cable 2 to the motor 10 and the inverter circuit 11 when it is off and no switching signal is input. The relay 7a is configured to connect the cable 2 to the detection unit 3 when it is on and a switching signal is input.

[0030] Providing the signal path switching means 7 can prevent the detection signal from leaking to the connection destination of the cable 2, such as the motor 10 or the inverter circuit 11, and can prevent the device from failing due to the leakage of the detection signal. In particular, by using the relay 7a as the signal path switching means 7, the connection between the cable 2 and the motor 10 or the inverter circuit 11 is mechanically cut off when a break is detected, so that the leakage of the detection signal can be reliably prevented. Providing the signal path switching means 7 can also prevent the device usage signal from leaking to the detection unit 3, which can cause the detection unit 3 to fail.

[0031] (Arithmetic unit 4) The arithmetic device 4 has a control unit 41 and a storage unit 42. A display unit 5 is connected to the arithmetic device 4, and is configured to be able to display various data such as resistance value data 421 and the result of disconnection detection on the display unit 5. The arithmetic device 4 is also provided with an input device 6 such as a keyboard, and various settings and the display contents of the display unit 5 can be operated by inputting from the input device 6. The display unit 5 may be configured as a touch panel display so that the display unit 5 also serves as the input device 6. Furthermore, the display unit 5 and the input device 6 do not need to be connected to the arithmetic device 4 by wire, and may be connected wirelessly. In this case, the display unit 5 and the input device 6 may be, for example, a smartphone or a tablet.

[0032] The control unit 41 is equipped with a frequency analysis unit 411, an extraction unit 412, a disconnection determination unit 413, and a disconnection detection operation control unit 414. The frequency analysis unit 411, the extraction unit 412, the disconnection determination unit 413, and the disconnection detection operation control unit 414 are realized by appropriately combining a calculation element such as a CPU, a memory such as a RAM or a ROM, software, an interface, a storage device, and the like.

[0033] The frequency analysis unit 411 performs frequency analysis on the resistance value data 421 (i.e., data on the resistance value of the conductor 21 that changes over time) measured by the detection unit 3. The result of the frequency analysis is stored in the storage unit 42 as frequency analysis data 422. Note that the frequency analysis means analyzing the magnitude of each frequency component included in the resistance value data 421 and obtaining the frequency analysis data 422, which is data obtained by extracting the magnitude of the component for each frequency.

[0034] The extraction unit 412 extracts the resistance value fluctuation components of an operating frequency f corresponding to the operating period of the movable part (or the resistance value fluctuation components of a higher-order frequency f×n (n is a natural number equal to or greater than 2) of the operating frequency f) based on the frequency analysis data 422, which is the analysis result of the frequency analysis.

[0035] The disconnection determination unit 413 determines a disconnection of the wires of the conductor 21 based on the magnitude of the resistance value fluctuation component of the operating frequency f (or the resistance value fluctuation component of the higher order frequency) extracted by the extraction unit 412. For example, when the magnitude of the resistance value fluctuation component of the operating frequency f (or the resistance value fluctuation component of the higher order frequency) becomes equal to or greater than a preset threshold, it may be determined that a disconnection has occurred in the wires. More specifically, the disconnection determination unit 413 determines that an initial disconnection has occurred in the multiple wires constituting the conductor 21 when the magnitude of the resistance value fluctuation component of the operating frequency f becomes equal to or greater than a preset threshold. Furthermore, the disconnection reflection unit 413 determines how many of the total number of wires constituting the conductor 21 have had a disconnection when the magnitude of the resistance value fluctuation component of a higher order frequency f×n (n is a natural number equal to or greater than 2) of the operating frequency f becomes equal to or greater than a preset threshold. This makes it possible to grasp the disconnection progress state of the conductor 21 (the disconnection rate, i.e., the degree to which the multiple wires constituting the conductor 21 have been disconnected). The determination result is stored in the storage unit 42 as disconnection detection data 423.

[0036] When detecting a disconnection (starting disconnection detection), the operation control unit 414 outputs a switching signal to the detection unit 3 to turn on the relay 7a, and causes the detection unit 3 to start measuring the resistance value while moving the movable part of the device at a constant cycle and speed. The timing for detecting a disconnection can be set arbitrarily, and can be performed, for example, during maintenance of the device or at the start of daily operation. The operation control unit 414 at the time of detecting a disconnection communicates with a control device of the device (not shown), and causes the device to execute a preset operation for detecting a disconnection (for example, an operation of bending or twisting the movable part at a constant cycle and speed) for a predetermined time, and the detection unit 3 measures the resistance value of the conductor 21.

[0037] At this time, all of the relays 7a corresponding to the three conductors 21 of the U, V, and W phases may be turned on to collectively detect breaks in the three conductors 21 in a state in which the three conductors 21 of the U, V, and W phases are connected in parallel. Alternatively, the relays 7a corresponding to the three conductors 21 of the U, V, and W phases may be turned on in sequence at predetermined time intervals to sequentially detect breaks in the multiple wires constituting each of the three conductors 21.

[0038] The arithmetic device 4 is configured by, for example, a personal computer. However, the present invention is not limited to this, and the arithmetic device 4 may be, for example, a server device. In this case, the resistance value data 421 measured by the detection unit 3 is transmitted to the arithmetic device 4, which is a server device, via a network.

[0039] (Disconnection detection method) FIG. 4 is a flow diagram showing the procedure of the disconnection detection method according to the present embodiment. As shown in FIG. 4, in the disconnection detection method according to the present embodiment, first, in step S1, the disconnection detection operation control unit 414 outputs a switching signal to the detection unit 3 to turn on the relay 7a. Thereafter, in step S2, the disconnection detection operation (for example, an operation of bending or twisting the movable part at a constant period and constant speed) is started, and the detection unit 3 starts measuring the resistance value of the conductor 21. Thereafter, in step S3, it is determined whether a predetermined time has passed (or whether a predetermined number of operations has been reached). If it is determined as NO (N) in step S3, the process returns to step S2, and the disconnection detection operation and resistance measurement are continued. If it is determined as YES (Y) in step S3, the disconnection detection operation and resistance measurement are stopped in step S4, and the switching signal is stopped to turn off the relay 7a. Thereafter, data on the resistance value of the conductor 21 measured by the detection unit 3 is transmitted to the calculation device 4 as resistance value data 421, and is stored in the storage unit 42 of the calculation device 4. Note that the "predetermined time" in step S3 is the shortest possible time required to detect a change in the resistance value modulated by the operating frequency f, and may vary appropriately depending on the configuration of the detection unit 3 and the measurement environment (i.e., the magnitude of the noise component), etc.

[0040] Then, in step S6, the frequency analysis unit 411 performs a frequency analysis of the resistance value data 421. The result of the frequency analysis is stored in the storage unit 42 as frequency analysis data 422. Then, in step S7, the extraction unit 412 extracts a resistance value fluctuation component of the operating frequency f (or a higher order frequency thereof) from the frequency analysis data 422. Then, in step S8, the disconnection determination unit 413 determines whether the magnitude of the resistance value fluctuation component of the operating frequency f (or a higher order frequency thereof) extracted in step S7 is greater than a threshold value. If the determination in step S8 is YES, in step S9, the disconnection determination unit 413 determines that there is a disconnection in the wire constituting the conductor 21, and ends the process. If the determination in step S8 is NO, in step S10, the disconnection determination unit 413 determines that there is no disconnection in the wire constituting the conductor 21, and ends the process. Note that in step S9, the disconnection determination unit 413 may determine whether the disconnection rate of the wire constituting the conductor 21 is increasing. Furthermore, if it is determined in step S9 that the wires constituting the conductor 21 are broken (or that the proportion of broken wires has increased to a predetermined proportion), an alarm may be issued using sound, light, or the like.

[0041] (Modification) In the example of FIG. 1, the motor 10 is star-connected, but as shown in FIG. 5, the disconnection detection device 1 can also be applied to a case where the motor 10 is delta-connected.

[0042] Also, as shown in FIG. 6, at least one of the signal path switching means 7 may be configured using a filter 7b that blocks signals of a predetermined frequency. In this case, the detection signal is set to a frequency different from that of the device use signal that is conducted to the conductor in the device. More specifically, the detection signal may be set to a frequency at which the impedance on the motor 10 side is sufficiently higher than the impedance on the detection unit side due to the inductance L of the motor 10. Also, the frequency of the detection signal may be a frequency that is sufficiently different from the frequency of the device use signal and is lower than the frequency of the device use signal. For example, when the fundamental modulation frequency of the inverter circuit 11 is 10 kHz, the frequency of the detection signal may be 3 kHz.

[0043] The filter 7b is provided so as to short-circuit the conductors 21 of each of the U-phase, V-phase, and W-phase and the ground conductor 21 via the filter 7b. As the filter 7b, a filter (e.g., a band-pass filter) that blocks the frequency of the device use signal output from the inverter circuit 11 and passes the detection signal is preferably used.

[0044] By configuring the signal path switching means 7 with the filter 7b, it is possible to omit the relay 7a, which has a relatively high failure rate, and to reduce failures caused by the relay 7a. In addition, since the relay 7a is no longer interposed between the motor 10 and the inverter circuit 11, the impedance between the motor 10 and the inverter circuit 11 can be reduced.

[0045] For example, in an industrial robot, the motor 10 is disposed in various parts of the device in a dispersed manner, so it is not desirable to place the relay 7a, which has a relatively high failure rate, near the motor 10. Therefore, it is more desirable that the first signal path switching means 71 provided on the motor 10 side is configured using the filter 7b.

[0046] The second signal path switching means 72 on the inverter circuit 11 side may also be configured using the filter 7b. By configuring both the first signal path switching means 71 and the second signal path switching means 72 using the filter 7b, it becomes possible to detect a disconnection even during operation of the device, enabling constant monitoring.

[0047] (Functions and Effects of the Embodiments) As described above, the disconnection detection device 1 according to this embodiment includes signal path switching means 7 that are provided at both ends of the cable 2 and suppress the flow of a detection signal to a connection destination of the cable 2 in the device. This makes it possible to detect a disconnection of the conductor 21 without removing the cable 2 itself from the device (a managed device such as an industrial robot) to which the cable 2 is wired, or removing the motors, sensors, drive circuits, and control devices connected to both ends of the cable 2 wired to the device. As a result, it is possible to reduce the effort required for disconnection detection and to perform disconnection detection frequently. In other words, according to this embodiment, it is possible to easily perform disconnection detection on the cable 2 wired to the device.

[0048] In addition, in a conventional detection method using the rate of increase in resistance, the resistance value of the conductor 21 before the break, i.e., the initial resistance value, was required, but in this embodiment, the occurrence of a break is detected using the amount of change (relative amount) in the resistance value during operation, not the absolute value of the resistance value, so the initial resistance value is not required. Therefore, according to this embodiment, even if the initial resistance value of the conductor 21 is unknown, it is possible to detect with high sensitivity that a break has occurred in the wire of the conductor 21.

[0049] Furthermore, although the resistance value of the conductor 21 and the contact resistance between the conductor 21 and the detection unit 3 vary greatly with temperature, the variation in resistance value due to temperature is unrelated to the operating cycle. Therefore, according to this embodiment, it is possible to detect a break in the conductor 21 without being affected by temperature changes.

[0050] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiment will be described by using the reference numerals and the like in the embodiment. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0051] [1] A device for detecting when a wire of a cable (2) having a conductor composed of a plurality of wires and wired to a device to be managed is broken due to the operation of the device to be managed, the device comprising: a detection unit (3) that applies a detection signal to the conductor (21) and measures a resistance value of the conductor (21) that changes over time due to the operation of the device to be managed; a breakage determination unit (413) that determines a breakage of the wire based on the measurement result of the resistance value of the conductor (21); and signal path switching means (7) provided at both ends of the cable (2) and that suppresses the flow of the detection signal to a connection destination of the cable (2) in the device to be managed.

[0052] [2] The disconnection detection device (1) described in [1], wherein at least one of the signal path switching means (7) comprises a relay (7a) capable of switching the connection destination of the cable (2) to the detection unit (3).

[0053] [3] The disconnection detection device (1) described in [1] or [2], wherein the detection signal has a different frequency from the signal conducted to the conductor (21) in the managed device, and at least one of the signal path switching means (7) is configured using a filter (7b) that blocks signals of a predetermined frequency.

[0054] [4] The disconnection detection device (1) described in [3], wherein one end of the cable (2) is connected to a motor (10) and the other end is connected to an inverter circuit (11), and the signal path switching means (7) provided on the motor (10) side is configured using the filter (7b).

[0055] [5] The disconnection detection device (1) described in any one of [1] to [4], wherein the signal path switching means (7) is mounted on connectors (12, 13) provided at both ends of the cable (2), respectively.

[0056] [6] The wire break detection device (1) according to any one of [1] to [5], wherein the detection unit (3) includes a frequency analysis unit (411) that performs frequency analysis on the resistance value of the conductor that changes over time measured by the detection unit (3), and an extraction unit (412) that extracts, from a result of the frequency analysis, a resistance value fluctuation component of an operating frequency or a higher-order frequency thereof that corresponds to an operating period of the operation of the managed device, and the wire break determination unit (413) determines a wire break based on the magnitude of the resistance value fluctuation component of the operating frequency or a higher-order frequency thereof extracted by the extraction unit (412).

[0057] (Additional Note) Although the embodiment of the present invention has been described above, the invention according to the claims is not limited to the embodiment described above. It should be noted that not all of the combinations of features described in the embodiment are essential to the means for solving the problems of the invention. The present invention can be modified appropriately without departing from the spirit of the invention. [Explanation of symbols]

[0058] 1...Disconnection detection device 2…Cable 21...Conductor 3. Detection unit 4…Arithmetic device 41...Control unit 411…Frequency analysis section 412...Extraction part 413…Disconnection detection unit 414...Disconnection detection operation control unit 42...Storage section 421…Resistance data 422…Frequency analysis data 423…Disconnection detection data 7...Signal path switching means 7a…Relay 7b…Filter 10…Motor 11...Inverter circuit 12,13…Connector

Claims

1. A device for detecting that a wire of a cable having a conductor composed of a plurality of wires and wired to a device to be managed is broken due to an operation of the device to be managed, a detection unit that applies a detection signal to the conductor and measures a resistance value of the conductor that changes over time in response to an operation of the managed device; a disconnection determination unit that determines whether the wire is disconnected based on a measurement result of the resistance value of the conductor; and a signal path switching means provided at each end of the cable, the signal path switching means suppressing the detection signal from flowing to a connection destination of the cable in the device to be managed. Disconnection detection device.

2. At least one of the signal path switching means is a relay capable of switching a connection destination of the cable to the detection unit. The disconnection detection device according to claim 1 .

3. the detection signal has a frequency different from that of a signal conducted through the conductor in the managed device; At least one of the signal path switching means is configured using a filter that blocks signals of a predetermined frequency. The disconnection detection device according to claim 1 .

4. One end of the cable is connected to a motor, and the other end is connected to an inverter circuit, The signal path switching means provided on the motor side is configured using the filter. The disconnection detection device according to claim 3.

5. The signal path switching means is mounted on connectors provided at both ends of the cable, The disconnection detection device according to claim 1 .

6. The detection unit is a frequency analysis unit that performs frequency analysis on the resistance value of the conductor that changes over time measured by the detection unit; an extracting unit that extracts a resistance value fluctuation component of an operating frequency corresponding to an operating period of the managed device or a higher order frequency thereof from a result of the frequency analysis, the disconnection determination unit determines a disconnection of the wire based on a magnitude of a resistance value fluctuation component of the operating frequency or a higher harmonic frequency thereof extracted by the extraction unit. The disconnection detection device according to claim 1 .

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