JP2019081178A - Welding system and method for detecting abnormality on welding-current carrying path in welding system - Google Patents

Abstract

To provide a welding system capable of detecting abnormalities on a welding-current carrying path including the deterioration of a secondary cable that connects a welding transformer with a welding gun at an early stage and a low cost, and a method for detecting abnormalities on a welding-current carrying path in the system.SOLUTION: A welding controller 3 measures a current value, a weld time, and various kinds of monitor values of pressurization forces and usage ratios on welding and acquires various kinds of set values on welding to transmit various kinds of set values and various kinds of monitor values to a database server 5 on a cloud 8 by association, and a monitor 6 acquires a plurality of various kinds of set values and various kinds of monitor values from the database server 5 to use, for a usage ratio included in each of the plurality of various kinds of monitor values, at least one of various kinds of set values and various kinds of monitor values for grouping into those with approximate values, further sets a threshold value for each group to inform a user of a resistance welder 2 of the deterioration of a secondary cable if the threshold value is exceeded in each group.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a welding system provided with a resistance welder configured to connect a welding transformer and a welding gun by a secondary cable, and a method of detecting an abnormality on a welding current flow path in a welding system.

  Conventionally, in a resistance welding machine, a pair of plates (hereinafter, referred to as "work (workpieces to be welded") formed by overlapping at least two steel plates with two electrodes of upper and lower electrodes disposed opposite to each other is held. The lower part is a table-shaped electrode (hereinafter referred to as “table electrode”), and the upper part is a gun-type electrode movable up, down, left, and right. There is a table type in which a workpiece is placed on an electrode, a tip portion of a gun-type electrode is placed on a welding point of the workpiece, current is supplied while applying pressure, and welding is performed. Also, in recent years, many inventions of so-called single-sided welding have been seen in which welding is performed by pressing the electrode against the work from one direction (mainly the upper direction) instead of pressing the electrode against the work from above and below for welding. (See, for example, Patent Document 1).

  Moreover, some conventional resistance welding machines can detect the degree of deterioration of the secondary cable connecting the welding transformer and the welding gun. For example, there are a secondary cable deterioration detection method described in Patent Document 2 and a secondary cable deterioration determination device for a resistance welder described in Patent Document 3. The former secondary cable deterioration detection method comprises: a first step of detecting a time point at which a polarity of an AC voltage applied to a primary circuit or a secondary circuit of a resistance welder changes; a primary circuit or a secondary of the resistance welder A second step of detecting an end point of conduction of alternating current flowing in the circuit, and a power factor angle is determined based on the zero voltage detection signal obtained in the first step and the zero current detection signal obtained in the second step And 3) and a fourth step of detecting the degree of deterioration of the secondary cable based on the power factor angle obtained in the third step. Although not described, the secondary cable is for connecting the secondary side of the welding transformer and the welding gun.

  The latter secondary cable deterioration judging device is a deterioration detecting the deterioration by comparing the voltage detection part detecting the voltage drop of each of the pair of secondary cables of the resistance welding machine with the measurement limit value and the measurement voltage thereof. The detection unit includes an operation confirmation unit that confirms a normal operation using the measured voltage, and the voltage detection unit includes an input circuit connected between both ends of the pair of secondary cables, and an amplified output of the input circuit. The degradation detection circuit consists of a common welding current setter that sets the maximum welding current, an initial resistance setter that sets the initial resistance value of each secondary cable, and each secondary cable Limit value setter which sets the allowable limit value of each at a rate of increase, a comparator which receives as input each limit voltage set by them and each measurement voltage mentioned above, and when the measurement voltage exceeds the limit voltage Comparison And an alarm counter for counting the comparison results from each other, and the operation confirmation unit sets a trigger level setting device whose trigger level is a voltage generated in the secondary cable by a current less than the minimum welding current value, and its trigger level And two comparators that respectively receive the measured voltage and the aforementioned measured voltage, an AND gate that takes the logical product of the outputs of both comparators, and a current-indicating indicator that displays an indication during energization in response to the output of the AND gate To prepare.

  On the other hand, conventionally, in order to control and monitor a resistance welder from a remote place, an apparatus or system has been devised which can be connected to the resistance welder using a network. For example, the remote welding control device described in Patent Document 4 includes a welding machine side device that controls and monitors a welding machine, and a central side device that sets / adjusts welding conditions, monitoring conditions, etc. The control unit of the welding machine is displayed on the control unit's control panel, and the supervisor sets / adjusts welding conditions, monitoring conditions, etc. on this display screen, and communicates the set / adjusted setting values. Transmit to the welder side device via the line, and control and monitor welding with the welder side device.

  In addition, for example, the production facility management system described in Patent Document 5 monitors the operation status of a production facility that produces an object at a production site, and periodically and when an abnormality or a fault occurs, the contents thereof with date and time The production facility management information is sent to the server computer of the general monitoring base via the network, and the server computer receives the sent production facility management information and records it in the recording device, and periodically or when an error or failure occurs. At the time or request acceptance, it is automatically transmitted to the computer of the service base via the network, and the computer of the service base receives the production facility management information sent from the server / computer and displays it on the screen of the display device. The contents of equipment repair, improvement, inspection as a part of production equipment management information server via network To send to the computer.

  By the way, in recent years, IoT (Internet of Things) has been used to collect information indicating the operating status of production facilities such as machine tools and robots installed in a factory, and to save labor by analyzing the obtained information. Attempts have been made to improve productivity. By using this IoT for a welding machine, it is possible to collect a lot of information indicating the operating state of the welding machine, and it can be expected to improve maintenance such as early detection of a failure.

JP, 2011-031269, A Unexamined-Japanese-Patent No. 5-119085 gazette JP-A-7-328775 Japanese Patent Application Laid-Open No. 11-074950 JP, 2005-128818, A

  However, in the secondary cable degradation detection method described in Patent Document 2 described above, the power factor angle is determined from the voltage zero crossing point and the current conduction end point, and the degradation of the secondary cable is automatically performed based on the determined power factor angle. Although the difference in resistance value between works is not taken into consideration, and the value at the work where the power factor angle becomes the minimum value is used as the threshold, the power factor angle is If the work is not the smallest, the monitoring for detecting the deterioration of the secondary cable becomes loose, and there is a problem that an abnormality can not be detected early.

  Moreover, in the secondary cable deterioration determination device for a resistance welder described in Patent Document 3 described above, in order to individually monitor two secondary cables, a threshold is set for each, but each threshold is As the voltage drop when the maximum current flows, it is not monitored when the current flowing is smaller than the maximum current. That is, there is a problem that the deterioration of the cable progresses, and an abnormality can not be detected (an abnormality can not be detected early) until the same voltage drop as when the maximum current flows.

  The disconnection period of the secondary cable used in the resistance welding machine is several months, usually several years (3, 4 years) in the short case, depending on the use conditions and the frequency of use, and usually the disconnection is not so easy. However, if the wire is broken, the work can not be performed until it is replaced, and a decline in productivity can not be avoided during that time. From these facts, it can be said that providing a means capable of detecting deterioration of the secondary cable in the resistance welding machine is cost-effective. However, if the cost of the means for detecting the secondary cable deterioration can be further reduced, the cost competitiveness can be enhanced, and if it can be detected early, the facility storage performance can be enhanced. Therefore, it is worthwhile to develop a device that can be enhanced in terms of cost and early detection.

  Although the secondary cable is one of the components on the path through which the welding current flows, even if the secondary cable has an abnormality on the welding current flow path, the abnormality is on the welding current flow path If only a certain thing can be detected, it can be recognized that some abnormality has occurred on the welding current flow path, so that it is possible to shorten the time required for subsequent handling.

  The present invention has been made in view of such circumstances, and detects abnormalities in the welding current flow path including the deterioration of a secondary cable connecting a welding transformer and a welding gun in a resistance welding machine early and at low cost. It is an object of the present invention to provide a welding system and an anomaly detection method on a welding current flow path in the welding system.

  The welding system of the present invention can be connected to a resistance welding machine that performs welding while pressing a work with two opposing electrodes, and to cloud computing, and the current value, energization time, pressing force, material of the work, A welding control apparatus for controlling the resistance welding machine based on various setting values including a thickness of a work, a work name, and a position on the work, a database server constructed on the cloud computing, and the cloud computing A welding system comprising a monitoring device constructed on the database server and accessible to the database server, wherein the welding control device is configured to adjust a current value, an energization time, and an application time when welding is performed by the resistance welding machine. Measuring various monitor values including pressure and usage rate, and acquiring the various setting values when welding is performed by the resistance welding machine; The acquired various setting values and the measured various monitor values are associated with each other and transmitted to the database server, and the monitoring device acquires a plurality of the associated various setting values and the various monitor values from the database server, The usage rates included in each of the plurality of acquired various monitor values are grouped into those having similar values by using at least any one of the various set values and the various monitor values, and a group is formed. Every time it detects an abnormality on the welding current flow path.

  According to the above configuration, since the usage rates included in each of the plurality of various monitor values are grouped into at least two, the fluctuation range of the usage rates in the respective groups becomes narrow. Abnormality can be detected early.

  Moreover, according to the above-mentioned configuration, for example, a dedicated detector for detecting deterioration of the secondary cable is not required, so cost reduction can be realized.

  In the above configuration, the monitoring device sets a threshold for each group, and when there is a group exceeding the set threshold, notifies the user of the resistance welding machine of an abnormality on the welding current flow path.

  According to the above configuration, since the user of the resistance welder can replace the secondary cable, which is one component on the welding current flow path, before it can not be used, it is possible to prevent a decrease in productivity.

  The abnormality detection method on the welding current flow path in the welding system of the present invention can be connected to a resistance welding machine that performs welding while holding a work between two opposing electrodes, and to cloud computing. A welding control device for controlling the resistance welding machine based on various setting values including an energization time, a pressing force, a material of a workpiece, a thickness of a workpiece, a workpiece thickness, and a workpiece position on the workpiece; A method of detecting an abnormality on a welding current flow path, the method being executed in a welding system comprising: a constructed database server; and a monitoring device constructed on the cloud computing and accessible to the database server, When welding is performed by the resistance welding machine, various monitored values of current value, current passing time, pressing force and usage rate are measured. And acquiring the various setting values when welding is performed by the resistance welding machine, and associating the measured various monitoring values and the acquired various setting values with each other and transmitting them to the database server. A plurality of the various setting values and the various monitor values associated with each other are acquired from the database server, and the usage rates included in each of the plurality of acquired various monitor values are acquired from the various setting values and the various monitor values. And at least one of them is used to group values whose values are similar to each other, and detecting an abnormality on the welding current flow path for each group.

  According to the above method, since the usage rates included in each of the plurality of various monitor values are grouped into at least two, the fluctuation range of the usage rates in each group becomes narrow. Abnormality can be detected early.

  Further, according to the above-mentioned method, for example, a dedicated detector for detecting deterioration of the secondary cable is not required, so cost reduction can be realized.

  According to the present invention, it is possible to detect an abnormality on a welding current flow path including the deterioration of a secondary cable connecting a welding transformer and a welding gun in a resistance welding machine at an early stage and at a low cost.

A block diagram showing a schematic configuration of a welding system according to an embodiment of the present invention The side view which shows the external appearance of the resistance welding machine which comprises the welding system of FIG. 1 The schematic configuration of each of the power supply unit and the welding transformer of the resistance welding machine shown in FIG. 2 is shown, and the connection between the power supply unit and the operation panel and the welding control device is shown. The figure which shows the control pulse for controlling the electric current supplied to the primary side of the welding transformer of the resistance welding machine of FIG. 2, the primary current, and the welding current after rectification. A block diagram showing a schematic configuration of a welding control device constituting the welding system of FIG. 1 A block diagram showing a schematic configuration of a monitoring device constituting the welding system of FIG. 1 It is a figure for demonstrating the grouping process of the utilization factor of the monitoring apparatus which comprises the welding system of FIG. 1, Comprising: A figure which shows an example of a change of the utilization factor when grouping by electric current value 10KA, 12KA, and 17KA Figure showing an example of the usage rate when welding was performed in the order of current values 10KA, 12KA and 17KA along the elapsed time of the welding point Diagram showing an example of change in usage rate when the usage rates are not grouped Figure showing an example of usage rate and 50-point moving average A diagram showing an example of a long-term fluctuation range of usage rate and a threshold value Th ′ corresponding to the long-term fluctuation range Figure showing an example of secondary cable degradation detection Flow chart for explaining the operation of the welding control device of FIG. 5 Flow chart for explaining the operation of the monitoring apparatus of FIG. Diagram showing an example of change in utilization rate when the secondary cable starts to break

Hereinafter, preferred embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a welding system 1 according to an embodiment of the present invention. In the figure, a welding system 1 according to the present embodiment includes a resistance welding machine 2, a welding control device 3, a Web server 4, a database server 5, a monitoring device 6, and a PC (personal computer) 7. Prepare. The resistance welding machine 2 and the welding control device 3 are mainly used by sheet metal processing manufacturers. For example, as shown in the figure, the resistance welding machine 2-1 and the welding control device 3-1 are used by a sheet metal processing maker YY1, and the resistance welding machine 2-2 and the welding control device 3-2 are a sheet metal processing maker YY2. The resistance welding machine 2-n and the welding control device 3-n are used by the sheet metal processing maker YYn. In this specification, when the resistance welding machine and the welding control device are treated in singular, they are described as “resistance welding machine 2” and “welding control device 3”, and when treated in plural, “resistance welding machine 2” It is described as 1,2-2 to 2-n and "welding control device 3-1, 3-2 to 3-n".

  The resistance welder 2 welds the workpiece 500 (see FIG. 2) disposed between the two opposing electrodes while holding the pressure according to the control of the welding control device 3. The welding control device 3 has a communication function that enables connection to cloud computing (hereinafter referred to as "cloud") 8. The welding control device 3 controls the resistance welding machine 2, and The resistance welding machine 2 is set based on various set values including “energization time”, “pressing force”, “material of work”, “plate thickness of work”, “work name” and “dock position on work”. Control. Hereinafter, each of the resistance welding machine 2, the welding control device 3, the web server 4, the database server 5, the monitoring device 6, and the PC 7 will be described in detail in order.

  FIG. 2 is a side view showing an appearance of a resistance welder 2 constituting the welding system 1 of FIG. In the figure, the resistance welding machine 2 includes a cooling unit 10, a power supply unit 11, a support post 12, a support arm 13, a welding gun 14, secondary cables 15A and 15B, a table electrode 16, and a table drive. It comprises a part 17, an operation panel 18, and a welding transformer 19. Cooling unit 10 supplies cooling water for cooling a portion through which current flows, such as welding gun 14, secondary cables 15A and 15B, support arm 13, table electrode 16 and welding transformer 19. The cooling unit 10 always operates while the resistance welding machine 2 is powered on, and circulates the cooling water with the welding gun 14. The power supply unit 11 rectifies and converts three-phase AC power supplied from a power reception facility (not shown) into direct current, and generates high frequency alternating current from direct current obtained by this.

  The support post 12 is vertically erected near the cooling unit 10 and the power supply unit 11, and supports the support arm 13 so as to be horizontally rotatable. The support arm 13 is substantially L-shaped and holds the welding gun 14. The support arm 13 includes a horizontal arm 13A extending in the horizontal direction with respect to the support post 12, and a vertical arm 13B extending downward in the vertical direction from the tip of the horizontal arm 13A.

  The welding gun 14 is pivotally held by the end portion of the vertical arm portion 13B of the support arm 13 so as to draw an arc in the vertical direction. A spring coil 13C is stretched between the base end of the welding gun 14 and the tip of the vertical arm 13B, and the contraction of the spring coil 13C causes the base end of the welding gun 14 to be vertically upward Lifted up. The welding gun 14 is pressurized in the direction toward the table electrode 16 by a cylinder 26 whose tip portion is provided at the tip portion of the horizontal arm portion 13A. A chain (chain, not shown) is contained in the vertical arm portion 13B, one end of the chain is connected to the cylinder 26, and the other end is connected to the power point portion (not shown) of the welding gun 14. As the chain is pulled up by the cylinder 26, the welding gun 14 is pivoted about a fulcrum portion (not shown), and the tip end portion is in pressure contact with the table electrode 16. Since the work 500 is placed on the table electrode 16, the tip end portion of the welding gun 14 is in pressure contact with the work 500. Pressurization of the welding gun 14 is performed immediately before the start of welding (i.e., immediately before the current is supplied) and released after the welding is completed. The pressure applied to the welding gun 14 is detected by a pressure sensor 61 (see FIG. 3). The description of the mechanism for introducing air into the cylinder 26 will be omitted.

  The proximal end portion of the welding gun 14 is provided with a handle 14A for operating the welding gun 14. The handle 14A is provided with a push-button activation switch (not shown), which is turned on by pressing the activation switch to output an activation signal Sw (see FIG. 3). The start signal Sw output from the start switch is taken into the welding control device 3.

  The electrode tip 25 is attached to the tip of the welding gun 14. The electrode tips 25 have various shapes, and each of the electrode tips 25 is detachably attached to the tip portion of the welding gun 14. The secondary cable 15A is a so-called cooling cable having a structure that allows cooling water to flow, and a plurality of conductors in which thin copper wires are bundled are provided inside. One end of the secondary cable 15A is connected to the plus electrode of the secondary side output end of the welding transformer 19, and the other end is connected to the welding gun 14.

  The secondary cable 15B has a structure in which a plurality of thin copper plates called a so-called ounce copper plate are stacked, one end is connected to the negative electrode of the secondary side output end of the welding transformer 19, and the other end is connected to the table electrode 16 Ru. In the resistance welding machine 2, although an ounce copper plate is used for the secondary cable 15B because the welding transformer 19 is disposed immediately below the table electrode 16, the welding transformer 19 and the table electrode 16 are separated. For example, a cooling cable similar to the secondary cable 15A may be used. Although a copper material is suitable as a material of secondary cables 15A and 15B, if it is a material excellent in conductivity and heat conductivity, it will not be limited to a copper material.

  The table electrode 16 is a copper material formed in a substantially square flat plate shape. The work 500 placed on the table electrode 16 is a plate assembly made of two cold-rolled steel plates, a galvanized steel plate, or a metal plate such as a stainless steel plate. The table drive unit 17 has a mechanism for moving the table electrode 16 up and down in the vertical direction, and operates in accordance with the operation of the operation button (not shown). The operation panel 18 has a display (not shown) such as a liquid crystal panel and a touch panel (not shown) of a resistive film type or the like attached on the display surface of the display. Various settings including “current value”, “energization time”, “pressing force”, “material”, “plate thickness”, “work name” and “dock position on the work” which are welding conditions on the operation panel 18 The value is set. The various setting values described above are displayed on the display of the operation panel 18, and the “current value”, “energization time”, “energization time” measured by the welding control device 3 when welding to the workpiece 500 is performed. Various monitor values including the pressure and the usage rate (PWM duty value) are displayed. As the welding conditions, in addition to "current value", "energization time", "pressing force", "material", "plate thickness", "work name" and "dock position on work", "cooling time" There are also "retention time" and so on. In addition to the "current value", "energization time", "pressing force" and "usage rate", the monitor value also includes "detected amount of dust", "resistance between chips", and the like.

  The welding transformer 19 is, for example, a welding transformer for resistance welding, which the inventors of the present invention previously proposed in JP 2012-210654 A and JP 2013-179205 A, and can supply a large current in a short time.

  FIG. 3 is a view showing a schematic configuration of each of the power supply unit 11 and the welding transformer 19 of the resistance welding machine 2 of FIG. 2 and showing a connection state of the power supply unit 11 and the operation panel 18 and the welding control device 3. In the figure, the power supply unit 11 includes a rectifier 31, a smoothing capacitor 32, and an inverter circuit 34. The rectifier 31 adopts a three-phase full-wave rectification type configured of six rectification elements, and rectifies three-phase alternating current from a power reception facility (not shown) to convert it into direct current. The smoothing capacitor 32 smoothes the DC voltage obtained from the rectifier 31.

  The inverter circuit 34 includes an inverter control circuit 341, four switches 342 using an IGBT (Insulated Gate Bipolar Transistor), and a current sensor 343 using a CT (Current Transformer). The inverter control circuit 341 turns on / off each of the four switches 342 based on the command signal Sti supplied from the welding control device 3 and the primary current detected by the current sensor 343 to generate high frequency alternating current. That is, the inverter control circuit 341 generates a high frequency alternating current controlled by PWM (Pulse Width Modulation). The magnitude of the high frequency alternating current generated by the inverter control circuit 341 changes with the on / off duty of each of the four switches 342. By changing the on / off duty of each of the four switches 342, the width W (see FIG. 4) of the switching waveform is changed.

  The primary coil 191 of the welding transformer 19 is connected to the output end of the inverter circuit 34 of the power supply unit 11. The output of the high frequency alternating current from the inverter circuit 34 causes a primary current to flow through the primary coil 191 of the welding transformer 19. The secondary coil of the welding transformer 19 does not have to consider the polarity by itself, but for convenience, the secondary coil of the welding transformer 19 is referred to as a series connection of the positive coil 192 and the negative coil 193. Make it The anode (positive electrode) of the first rectifier 194 is connected to one end of the positive coil 192, and the anode (positive electrode) of the second rectifier 195 is connected to one end of the negative coil 193. The cathode (negative electrode) of the first rectifying element 194 and the cathode (negative electrode) of the second rectifying element 195 are commonly connected to the plus electrode 196. The other end of the positive coil 192 and the other end of the negative coil 193 are commonly connected to the negative electrode 197. The welding gun 14 is connected to the plus electrode 196, and the table electrode 16 is connected to the minus electrode 197. Although it is not necessary to mention, the plus electrode 196 and the welding gun 14 are connected by the secondary cable 15A, and the minus electrode 197 and the table electrode 16 are connected by the secondary cable 15B.

  FIG. 4 is a view showing a switching pulse ("control pulse") for controlling the current supplied to the primary side of the welding transformer 19 constituting the resistance welding machine 2, the primary current and the welding current after rectification. In the figure, the switching pulse of the width W controlled by the inverter circuit 34 is a fixed number of times within a fixed time H, here a total of 10 times in the positive direction pulse and the negative direction pulse. Supplied. As a result, a primary current as shown in FIG. 4B flows through the primary coil 191 of the welding transformer 19. The secondary current generated on the secondary side of the welding transformer 19 is full-wave rectified by the rectifying elements 194 and 195 when the primary current flows through the primary coil 191 of the welding transformer 19, as shown in FIG. 4C. The welding current flows through the welding gun 14.

  The magnitude of the welding current can be adjusted by increasing or decreasing the width W of the switching pulse shown in FIG. Further, the welding time can be adjusted by increasing or decreasing the number of times of supplying the switching pulse. Moreover, welding time can be adjusted more finely by raising the repetition frequency of a switching pulse. Further, by increasing the current supplied to the primary coil 191 of the welding transformer 19, larger welding current can be extracted from the positive side coil 192 and the negative side coil 193 of the secondary coil.

  Returning to FIG. 3, the resistance welding machine 2 includes a current sensor 60 for detecting a secondary current generated on the secondary side of the welding transformer 19 and a pressure sensor (strain gauge or the like) 61 for detecting a pressing force for pressing the workpiece 500. And a temperature sensor (thermocouple, thermistor or the like) 62 for detecting the temperature of the cooling water. The sensor signal Si output from the current sensor 60, the sensor signal Sp output from the pressure sensor 61, and the sensor signal St output from the temperature sensor 62 are taken into the welding control device 3.

  The welding control device 3 includes various items including “current value”, “energization time”, “pressing force”, “material of work”, “plate thickness of work”, “work name” and “dock position on work”. An operation panel 18 for setting setting values is connected. The welding control device 3 generates the command signal Sti for operating the resistance welding machine 2 based on the set various setting values by setting the various setting values on the operation panel 18, and the inverter of the power supply unit 11 It outputs to the circuit 34. The workpiece 500 is given in advance a “work name” representing a workpiece specification, a “position on the workpiece,” and the like, and this specification is set by the operation panel 18.

  In addition, when welding is performed by the resistance welding machine 2, the welding control device 3 uses the sensor signal Si of the current sensor 60, the sensor signal Sp of the pressure sensor 61, and the usage rate obtained by the inverter control circuit 341 of the inverter circuit 34. The PWM duty signal Spwm indicative of is taken in, and “current value”, “energization time”, “pressing force” and “usage rate” are measured. The welding control device 3 treats each of the measured "current value", "energization time", "pressure" and "usage rate" as monitor values.

  FIG. 5 is a block diagram showing a schematic configuration of a welding control device 3 constituting the welding system 1 of FIG. As shown in the figure, the welding control device 3 includes a control unit 301, a clock unit 302, a counter unit 303, an interface unit 304, a storage unit 305, a communication unit 306, and a common bus 307. The control unit 301 includes a central processing unit (CPU) (not shown), a read only memory (ROM) storing a program for controlling the CPU, and a random access memory (RAM) as a work memory used for the operation of the CPU. And. The control unit 301, the clock unit 302, the counter unit 303, the interface unit 304, the storage unit 305, and the communication unit 306 are connected to the common bus 307.

  In the control unit 301, the CPU cooperates with the program stored in the ROM to generate a command signal Sti, and measures the current value based on the sensor signal Si of the current sensor 60 during welding. Processing, energization time measurement processing for measuring the energization time at the time of welding, pressing force measurement processing for measuring the pressing force applied to the work 500 based on the sensor signal Sp of the pressure sensor 61 at the welding, inverter control circuit 341 at the welding Various processing such as usage rate measurement processing for measuring the usage rate based on the PWM duty signal Spwm and water temperature measurement processing for measuring the temperature of the cooling water based on the sensor signal St of the temperature sensor 62 are executed. The control unit 301 enables rewriting of a flash memory (also referred to as "EEPROM (also referred to as" Electrically Erasable Programmable Read Only Memory "), etc., in addition to the ROM described above as a medium for storing a program for controlling the CPU. The use of semiconductor memory is also possible. The program can be easily updated by using a semiconductor memory that enables rewriting.

  The clock unit 302 generates a clock signal necessary for the operation of each unit of the apparatus, and measures the conduction time under the control of the control unit 301. The counter unit 303 counts the number of times of welding (“the number of times of hitting”) under the control of the control unit 301, and counts the number of products produced. The interface unit 304 connects the power supply unit 11 and the operation panel 18, and also connects various sensors (the current sensor 60, the pressure sensor 61 and the temperature sensor 62) and the start switch of the welding gun 14.

  The storage unit 305 is configured of a large-capacity storage device such as a hard disk drive or a solid state drive (SSD), and stores the various setting values and various monitor values described above. The communication unit 306 connects to the cloud 8. The control unit 301 controls the communication unit 306 to transmit data to the database server 5. Data to be transmitted to the database server 5 include various monitor values including "current value", "pressing force", "usage rate" and "energization time" measured at the time of welding, and "current value" set immediately before welding. , And various setting values including “energization time”, “pressing force”, “work material”, “work thickness”, “work name” and “dock position on work”, and these are associated with each other 1 It is transmitted to the database server 5 as one data (of course, a header is added).

  The welding control device 3 is constantly connected to the database server 5 in order to transmit various setting values and various monitor values to the database server 5 each time welding is performed by the resistance welding machine 2. As a protocol used for communication between welding control unit 3 and database server 5, HTTPS (Hyper Text Transfer Protocol Secure) or MQTT (MQ Telemetry Transport) is suitable, but HTTP (Hyper Text Transfer Protocol) may be used. .

  The control unit 301 takes in the start signal Sw output from the welding gun 14 via the interface unit 304 to set various setting values (“current value”, “energization time”, Loads pressure, material, thickness, workpiece name, position on workpiece, etc.) and generates the command signal Sti based on the various setting values and various monitor values that have been read, and the power supply unit Output to 11.

  The welding control device 3 is connected to the resistance welding machine 2 by wire because it is disposed close to the resistance welding machine 2, but it is of course possible to connect wirelessly. For example, a wireless LAN or Bluetooth (registered trademark) is preferable as a means for wireless connection. Further, since the welding control device 3 and the operation panel 18 are also arranged close to each other, connection between them is also made by wire, but of course wireless connection is also possible.

  In FIG. 1, the Web server 4, the database server 5 and the monitoring device 6 are respectively constructed on the cloud 8 and can mutually exchange data bidirectionally. The Web server 4 stores image files in addition to HTML files written in HTML (Hyper Text Markup Language), and if there is a request from the Web browser of the PC 7, HTML files and image files etc. corresponding to the request are stored. Send to PC7. For example, if the request from the Web browser of the PC 7 is to request the processing result of the monitoring device 6, the Web server 4 transmits, to the PC 7, an HTML file or an image file indicating the processing result. As a protocol for communicating between the web server 4 and the web browser of the PC 7, for example, HTTP (Hyper Text Transfer Protocol) is used. The web browser of the PC 7 establishes a TCP (Transmission Control Protocol) connection with the web server 4 when accessing the web server 4 and then acquires an HTML file, an image file, etc. from the web server 4. The HTML file, the image file, etc. acquired by the web browser are displayed by the PC 7 on the monitor screen of the PC 7. The database server 5 receives and accumulates various setting values and various monitor values transmitted from the welding control device 3 each time one resistance welding is performed in each resistance welding machine 2.

  The monitoring device 6 monitors an abnormality on the welding current flow path of each of the resistance welding machines 2-1 to 2-n, and mainly, the resistance welding machines 2-1 to 2-n and the welding control device 3- It is used by the maker which manufactured 1-3-n. Most of the abnormalities that occur on the welding current flow path in each resistance welding machine 2-1 to 2-n are deterioration of the secondary cables 15A and 15B connecting the welding gun 14 and the welding transformer 19, so this embodiment In this case, the deterioration of the secondary cables 15A and 15B is treated as an abnormality on the welding current flow path. In addition, the contact defects, such as an electromagnetic switch (contactor) and a cable joint, also exist in the abnormality which arises on a welding current flow path.

  FIG. 6 is a block diagram showing a schematic configuration of a monitoring device 6 constituting the welding system 1 of FIG. As shown in the figure, the monitoring device 6 includes a control unit 601, a storage unit 602, an operation unit 603, a display unit 604, a communication unit 605, and a common bus 606. The control unit 601, the storage unit 602, the display unit 603, the operation unit 604, and the communication unit 605 are connected to the common bus 606. The control unit 601 has a CPU (not shown), a ROM storing a program for controlling the CPU, and a RAM as a work memory used for the operation of the CPU. The CPU cooperates with the program stored in the ROM to acquire various setting values and various monitor values stored in the database server 5, data acquisition processing for grouping, grouping processing for grouping the utilization rate, utilization rate Threshold setting processing for setting the threshold for each group, threshold correction processing for correcting the threshold, and cable deterioration notification processing for notifying the user of the resistance welding machine 2 of deterioration of the secondary cables 15A and 15B if there is a group exceeding the threshold Execute various processes of

  In addition to the ROM, a semiconductor memory that enables rewriting of a flash memory or the like can also be used as a medium for storing a program for controlling the CPU in the control unit 601. The program can be easily updated by using a semiconductor memory that enables rewriting. It is also possible to store the program in a storage medium such as an optical disk, a magnetic disk, a magneto-optical disk or the like and read out from the storage medium when the above processing is performed.

  The storage unit 602 stores a plurality of various setting values and various monitoring values from the resistance welding machine 2 acquired from the database server 5. For the storage unit 602, for example, a storage device such as a hard disk drive or an SSD, or a rewritable storage medium such as a flash memory is used.

  The operation unit 603 is used to operate the monitoring device 6. When an operation is performed on the operation unit 603, the control unit 601 performs processing in accordance with the operation. For example, when there is an operation of manually setting the threshold, the threshold is set in accordance with the operation. Further, the control unit 601 displays the processing result on the display unit 604 when there is an operation to visually display the processing result and the like.

  The monitoring device 6 acquires a plurality of various setting values and various monitoring values from the resistance welding machine 2 accumulated in the database server 5, and the secondary cable 15A based on the acquired various various setting values and various monitoring values. , 15B are detected. In this case, if there are a plurality of resistance welders 2, deterioration of the secondary cables 15A and 15B of each resistance welder 2 is detected. The period in which the monitoring device 6 acquires various set values and various monitor values from the resistance welder 2 is basically from the start of use of the resistance welder 2 (when the resistance welder 2 is purchased and used first) Of course, it is also possible to specify a period up to now, such as from the second year after the start of use to the present.

  Here, the deterioration of the secondary cables 15A and 15B of the resistance welder 2 in the welding system 1 according to the present embodiment occurs in most cases on the longer secondary cable 15A, and hence the secondary cables Deterioration refers to the secondary cable 15A. Further, the cause of the deterioration of the secondary cable 15A is, in most cases, the bending of the secondary cable 15A accompanying the operation of the welding gun 14. When the resistance welder 2 is used for a long time, the in-cable wiring of the secondary cable 15A is easily broken. When a part of the cable in the cable is broken when the secondary cable 15A is bent, the resistance value of the cable itself increases, and then, when the secondary cable 15A becomes straight or almost straight, the broken part Becomes connected, and the resistance value of the cable itself becomes approximately the original value (that is, the value at the normal time). As described above, when a part of the intra-cable wiring of the secondary cable 15A is broken, the resistance value of the cable itself changes due to the secondary cable 15A bending or becoming straight or nearly straight.

  The resistance welding machine 2 controls so that the set current value is always constant. Therefore, when the resistance value of the cable itself increases due to the deterioration of the secondary cable 15A, the usage rate is large to compensate for the decrease in the current value. Become. Deterioration of the secondary cable 15A can be detected by setting a threshold value for this usage rate. However, as will be described in detail below, even if the threshold value is simply set for the usage rate, the fluctuation range of the usage rate becomes wide, so the usage rate may not exceed the set threshold. Then, deterioration of the secondary cable 15A can not be detected early. According to the present invention, the usage rates are divided into groups based on predetermined conditions so that the deterioration of the secondary cable 15A can be detected early, so that the fluctuation range of the usage rates becomes narrow.

  The monitoring device 6 is at least one of various setting values and various monitoring values for each of a plurality of various setting values obtained by one resistance welding machine 2 and a plurality of usage rates among various monitoring values. Groups the values (values of usage rate) into similar ones. Thereafter, a threshold is set for each group to detect deterioration of the secondary cable 15A of the resistance welder 2. The usage rate is a value corresponding to various setting values such as “current value”, “energization time”, “pressing force”, “material”, “plate thickness”, “work name” and “dock position on work”. Therefore, grouping can be performed according to these setting values.

  Since the monitoring device 6 detects deterioration of the secondary cable 15A for each of the plurality of resistance welders 2, after detecting deterioration of the secondary cable 15A of the first resistance welder 2, two units are detected. Deterioration detection of the secondary cable 15A of the eye resistance welder 2 is performed. The same process is performed on all the remaining resistance welders 2. Moreover, since the temporal change of the usage rate is monitored, the plurality of various set values and various monitor values obtained by one resistance welding machine 2 are at the start of use of the resistance welding machine 2 as described above. It will be the number from to the present.

  The monitoring device 6 performs processing for detecting deterioration of the secondary cable 15A each time the database server 5 receives data from the welding control device 3, but can also perform processing at predetermined time intervals.

Next, how to divide the usage rate and how to set the threshold will be described in detail.
(Details of usage grouping)
For example, one of various setting values of “current value”, “energization time”, “pressing force”, “material of work”, “plate thickness of work”, “work name” and “dock position on work” In the case where the usage rate is divided into groups based on the "current value", which is one of the two, it is assumed that the grouping is made by the current values 10KA, 12KA and 17KA. In addition, "KA" is a thing of kiloampere. FIG. 7 is a diagram showing an example of a change in usage rate for each hit when grouped by current values 10KA, 12KA and 17KA, the horizontal axis is a hit point (or time), and the vertical axis is a usage rate. In the figure, a group G1 is a usage rate at a current value 10KA, a group G2 is a usage rate at a current value 12KA, and a group G3 is a usage rate at a current value 17KA. However, although the groups G1 to G3 are drawn side by side in the vertical axis direction in FIG. 7, in actuality, since the usage rate for each hit point, each of the groups G1 to G3 is different in the horizontal axis direction. FIG. 8 is a diagram showing an example of the usage rate when welding is performed in the order of current values 10KA, 12KA, and 17KA, the horizontal axis is the hit point, and the vertical axis is the usage rate. In the example shown in the figure, welding is performed with first to 100th spots having a current value of 10KA, 101 to 200th spots having a current value of 12KA, and 201st to 300th spots having a current value of 17KA. Shows the usage rate when Although it is necessary to set the horizontal axis for each of the groups G1 to G3 in order to express one graph, it is omitted in FIG.

  After the usage rates are grouped by the current value, threshold values Th1 to Th3 are set for each group, and changes in the usage rates in each group are monitored. By the way, if the usage rate is not divided into groups, the threshold value is set for the 17KA with the largest current value, but with the current value set to 17KA, welding with a current value of 10KA or 12KA If there are many opportunities to do so, even if degradation occurs in the secondary cable 15A, degradation of the secondary cable 15A can not be detected unless the usage rate exceeds the threshold. After that, the deterioration of the secondary cable 15A can be detected only when there is an opportunity to weld at a current value of 17KA. As described above, when the usage rates are not grouped, it is difficult to detect the deterioration of the secondary cable 15A early.

  FIG. 9 is a diagram showing an example of the change in the usage rate when the usage rates are not grouped, and the horizontal axis is a hit point (or time) and the vertical axis is the usage rate. As shown in the figure, when the usage rate is not divided into groups, the fluctuation range is wider than when grouped, and when the threshold value Th is set immediately above the upper limit of this fluctuation range, the lower side of the fluctuation range and Therefore, the usage rate does not exceed the threshold Th even if the secondary cable 15A is deteriorated. Therefore, the deterioration of the secondary cable 15A can not be detected early. On the other hand, as shown in FIG. 7, by dividing the usage rate into three current values of 10 KA, 12 KA and 17 KA and setting the threshold for each group, if there are many opportunities to be used at current value 10 KA The deterioration of the secondary cable 15A can be detected in the group of the current value 10KA, and the deterioration of the secondary cable 15A can be detected in the group of the current value 12KA if there are many opportunities to be used at the current value 12KA. . In addition, if there are many opportunities for use at the current value 17KA, deterioration of the secondary cable 15A can be detected in the group of the current value 17KA. Thus, by grouping the usage rates, it is possible to detect the deterioration of the secondary cable 15A early.

  By the way, even if the usage rate is divided into the same group, the energization time is different, the pressing force is different, the material and thickness of the work are different, the work name is different, and the hit point position on the work is different. The value of the utilization rate may be largely different (ie, the fluctuation range of the group may be large). For example, even at a current value of 17 KA, the usage rate differs between when the energization time is 50 msec and when the energization time is 200 msec, and the fluctuation range of the usage rate group G3 at the current value of 17 KA is wide. When the fluctuation range of the usage rate becomes wide, it becomes difficult to detect the deterioration of the secondary cable 15A early as described in FIG. In such a case, by adding a new grouping condition, the current value of the same 17KA can be divided into different groups. If, for example, the energization time is used as a new grouping condition, it can be divided into a group of current value 17KA + energization time 50 msec and a group of current value 17KA + energization time 200 msec. Each variation width is narrower than in the case of only the current value 17KA, so that deterioration of the secondary cable 15A can be detected early. As described above, by increasing the grouping condition, finer grouping can be performed, and the fluctuation range of each can be narrowed, so that deterioration of the secondary cable 15A can be detected early.

  As the grouping condition, in addition to the “current value” and “energization time” described above, “pressing force”, “work material”, “work thickness”, “work name”, “dock position on work” The fluctuation range is narrowed by increasing the conditions. Above all, when using the hit point position on the work, since the grouping can be performed for each hit point, the fluctuation range of the usage rate becomes narrower than the other conditions. In the case of passing the same current value, at the first point and the second point adjacent to the first point, the current flowing at the time of welding is divided by the welding at the first point, so the usage rate at the second point is the first point Although smaller than the usage rate, this difference can be distinguished by using the hit point position on the work. Thereby, deterioration of the secondary cable 15A can be detected more reliably.

The conditions for grouping the usage rates are easier to manage if they are smaller, so it is better to group in the following order. In addition, since the conditions used for grouping the usage rates have superiority or inferiority, this point will also be described.
(1) Group only by current value (set value or monitor value). It is inferior in that different work is included.
(2) Group by current value (set value or monitor value) and energization time. The detection of deterioration of the secondary cable 15A is more reliable than in the case of the condition (1).
(3) Group by current value, energization time, usage rate (monitor value). The detection of deterioration of the secondary cable 15A is more reliable than in the case of the condition (2).

(4) Group by work name only. Since different welding conditions are included only with the work name, the reliability of detection of deterioration of the secondary cable 15A is inferior.
(5) Group by work name and hitting position on the work. Deterioration detection of the secondary cable 15A is reliable.
(6) Group by work name, current value, and energization time. Although the deterioration detection of the secondary cable 15A is reliable, it is more reliable than the case of the condition (5).

Grouping also means "stratified" because the usage rate is divided according to the value.
Also, grouping of usage rates is performed for each resistance welder, even if the deterioration degree of the secondary cable 15A is different for each resistance welder, it means that usage rates obtained by other resistance welders can be grouped Because there is no

(Details of threshold setting)
After grouping the usage rate as described above, the threshold value is set for each group, but the usage rate fluctuates due to noise and so forth, and also gently due to fluctuations in the power supply voltage and electrode tips. Due to fluctuations, setting a threshold of a constant value for the fluctuating usage rate increases the chances of false detection. Therefore, it is necessary to set a threshold that follows fluctuations in the usage rate.

  In setting the threshold, in order to even out fluctuations such as noise to the usage rate, a moving average is obtained. Next, with respect to the obtained moving average, a process of setting a value at which the secondary cable 15A is erroneously detected and a process of setting a value at which the secondary cable 15A is not erroneously detected are repeated to set appropriate threshold values. In this case, the initial setting of the threshold may be determined within a range in which the margin is seen (that is, detection is delayed). For example, it is set to a place where there is a margin for erroneous detection or disconnection of the secondary cable 15A. Then, looking at the fluctuation range of the utilization rate, the range for false detection is narrowed to reduce the margin.

  By the way, since the usage rate changes, it is necessary to make the threshold follow the change, but if the tracking speed of the threshold is not made slower than the change in the usage rate due to the deterioration of the secondary cable 15A, the deterioration It is not possible to accurately grasp the change in utilization rate (i.e., the disconnection state of the secondary cable 15A) accompanying the above. It is necessary to consider the point in setting the threshold.

  In addition, since the usage rate gently fluctuates (long-term fluctuation) due to fluctuation of the power supply voltage, fluctuation of the electrode tip, or the like, it is necessary to correct the threshold with respect to this long-term fluctuation. The correction of the threshold value for the long-term fluctuation is performed by calculating the amount of change using the usage rate stabilized by the moving average, and correcting based on the amount of change obtained by this calculation. The moving average of the usage rate is calculated every 50 to 100 batts, and when the fluctuation is large due to disturbance or the like, the number of batting points is adjusted. In addition, the amount of change in usage rate is calculated every several hundreds of points, and if the fluctuation is large due to disturbance or the like, the number of batting points is adjusted. FIG. 10 is a diagram showing an example of the usage rate and the moving average, and the horizontal axis is the hit point (or time), and the vertical axis is the usage rate. The figure shows the usage rate and the moving average of the usage rate calculated every 50 points. Further, the figure is an enlargement of the usage rate, and the usage rate is a continuous waveform including noise. The figure also shows the amount of change calculated for every 300 points. FIG. 11 is a diagram showing an example of the long-term fluctuation range of the usage rate and the threshold value Th ′ corresponding to the long-term fluctuation range, the horizontal axis is a hit point (or time), and the vertical axis is the usage rate.

  In addition, if a threshold with no margin for false detection is used, the chance of false detection of deterioration of the secondary cable 15A increases, and if a threshold with margin is used, deterioration of the secondary cable 15A can not be detected. There are many opportunities. In order to be able to accurately detect the deterioration of the secondary cable 15A, setting of the threshold is repeated to set an appropriate threshold, but the setting may usually be performed automatically. However, until the threshold value is stabilized, such as at the beginning of the introduction of the welding system 1, it may be verified whether or not it is a false detection manually at the time of detection of deterioration, and the threshold value is manually corrected. Further, since the threshold value is always corrected according to the short-term fluctuation and the long-term fluctuation of the usage rate, it is of course possible to utilize AI (Artificial Intelligence) for the correction processing.

  In this way, a moving average of the utilization rate is calculated for each group, a threshold for detecting an abnormality of the secondary cable 15A is set for the moving average obtained by this, and further, from the moving average Since the gradual change over a long period is calculated and the threshold value is corrected based on the obtained change, the fluctuation of the power supply voltage and the fluctuation of the tip of the electrode tip (attached to the tip of the welding gun) It is possible to detect an abnormality on the welding current flow path without erroneous detection even if a gradual fluctuation is included.

In addition, "there is allowance in the setting of a threshold value" mentioned above is as follows.
The usage rate is the current value to be used, the work resistance, and the resistance other than work (the resistance of the resistance welding machine 2, which is the sum of the resistance of the secondary cable 15A, the internal resistance of the welding transformer 19, and the other resistances Depending on the That is, the usage rate becomes large, for example, when the current value is large or the work resistance value is large. Here, assuming that the resistance other than the work is 500 μΩ and the secondary voltage of the welding transformer 19 is 10 V, the short circuit current (usage rate 100%) is 20 KA at 10 V / 500 μΩ.

  In the case of the group G1 shown in FIG. 7, assuming that the current 10 KA and the work resistance 200 μΩ, the estimated value of the usage rate at this time is 10 V / (500 μΩ + 200 μΩ) = 14.3 KA, 10 KA / 14.3 KA = about 70% usage rate It becomes. In this case, there is a margin of 30%, and even if the resistance value is increased due to the deterioration of the secondary cable 15A, the set current flows due to the correction of the usage rate. Therefore, monitoring can use a value (threshold) of 70% or more, and a value of 90% can be used as a value to see the margin.

  On the other hand, in the case of the group G2 shown in FIG. 7, assuming that the current 12KA and the work resistance 250 μΩ, the estimated value of the usage rate at this time is 10 V / (500 μΩ + 250 μΩ) = 13.3KA, 12KA / 13.3KA = about 90% It will be the usage rate. In this case, there is only a margin of 10%, and the monitoring needs to have a value of 90% or more, and it is impossible to set a value for viewing the margin as in group G1.

  The threshold value is set each time the processing for detecting deterioration of the secondary cable 15A is performed, but the pattern does not have to be one pattern, and a plurality of patterns are set and monitored in each pattern. It is also possible. For example, if it is assumed that the threshold pattern set at the first time is “A pattern” and the threshold pattern set at the second time is “B pattern”, both “A pattern” and “B pattern” are monitored. In this case, which pattern is optimal can not be determined unless the secondary cable 15A is completely degraded. However, if it is known, the optimal one can be selected. Thus, the deterioration of the secondary cable 15A can be detected with high accuracy by preparing a plurality of threshold patterns. Incidentally, it goes without saying that correction is performed as needed for any pattern. Also, it is of course possible to utilize the above-described AI in the process of setting a plurality of patterns and selecting an optimum pattern.

Further, although the setting of the threshold is performed for each group, a group having many false detections may be excluded from monitoring targets. That is, the threshold value may be set only for the group which is stably changing while being grouped.
Also, the threshold can be corrected based on the usage rate at the time of actual occurrence of abnormality.

  After setting the threshold for each group, the monitoring device 6 determines whether there is a group that exceeds the threshold. As described above, when the secondary cable 15A is degraded, the usage rate is increased. Therefore, if the usage rate in each group exceeds the threshold value, it can be determined that the secondary cable 15A is degraded. FIG. 12 is a diagram showing an example of detection of deterioration of the secondary cable 15A, in which the horizontal axis is a hit point (or time) and the vertical axis is a usage rate (PWM duty value). As shown in the figure, when the usage rate exceeds the threshold values Th1 'to Th3' in each of the groups G1 to G3, the monitoring device 6 detects the deterioration of the secondary cable 15A. However, if the deterioration of the secondary cable 15A is detected once the threshold is exceeded, the deterioration of the secondary cable 15A is detected even if the deterioration of the secondary cable 15A is not the cause, so the case where the threshold is exceeded a predetermined number of times False detection can be eliminated by detecting the deterioration of the secondary cable 15A.

  When the monitoring device 6 detects the deterioration of the secondary cable 15A, the monitoring device 6 notifies the user of the resistance welder 2 to that effect. As a method of notifying the user of the resistance welding machine 2, a method of transmitting maintenance information to the welding control device 3 of the user, transmitting maintenance information by mail to information equipment such as a personal computer or a portable terminal of the user of the resistance welding machine 2. , And a method of directly calling a user of the resistance welding machine 2. When transmitting maintenance information to the welding control device 3 of the user, the operation panel 18 is provided with a display for informing the cable exchange, or a buzzer or voice synthesis informing the cable exchange is provided to affect the user's vision and perception. You should do it.

  As a method of notifying the deterioration of the secondary cable 15A, there is also a method of transmitting an HTML file or an image file indicating maintenance information from the Web server 4 to the Web browser of the PC 7. That is, the HTML file and the image file for notifying degradation of the secondary cable 15A to the Web server 4 are stored in advance, and when there is a request for requesting maintenance information from the PC 7, the Web server 4 performs the maintenance information The HTML file and the image file shown are sent to the PC 7. By doing this, the user of the resistance welding machine 2 can view maintenance information of the resistance welding machine 2 with his / her PC (personal computer, not shown) at any time, and the secondary cable 15A can be prematurely Exchange can be done. Needless to say, in this case, the maintenance information of other users can not be viewed.

  As described above, when the monitoring device 6 detects the deterioration of the secondary cable 15A of the resistance welder 2 based on a plurality of various setting values and various monitor values obtained from the resistance welder 2, the user of the resistance welder 2 Of the deterioration of the secondary cable 15A.

Next, operations of the welding control device 3 and the monitoring device 6 will be described.
(Operation of welding control device 3)
FIG. 13 is a flowchart for explaining the operation of welding control device 3. In addition, since the operation in the welding control device 3 is performed by the control unit 301, the subject is the control unit 301. However, since the operation will be described as the operation of the welding control device 3 itself, the subject is the welding control device 3 and Do.

  The welding control device 3 first connects to the cloud 8 (step S10). When connection with the cloud 8 is established, the welding control device 3 sets “current value”, “energization time”, “pressing force”, “work material”, “work thickness”, “operation value” on the operation panel 18. If it is determined whether various set values of the work name and the hit position on the work are set (step S11), and if it is determined that the various set values are not set (that is, it is determined NO in step S11) This process is continued until the various set values are set. When it is determined that the various setting values are set in step S11 (that is, when it is determined as "YES" in step S11), welding control device 3 temporarily stores the set various setting values (step S12).

  After temporarily storing the set various setting values, welding control device 3 determines whether or not start signal Sw is output (step S13), and when it is determined that start signal Sw is output (ie, in step S13) If "YES", the command signal Sti is generated based on various setting values temporarily stored (step S14). If welding control device 3 determines that start signal Sw is not output in step S13 (that is, if it determines "NO" in step S13), it returns to step S11. Returning to step S11, it is determined whether or not various setting values have been set. If even one of the various setting values is changed, the various setting values temporarily stored are updated.

  After generating the command signal Sti, the welding control device 3 outputs the command signal Sti to the power supply unit 11 of the resistance welder 2 (step S15). Thereby, welding for one hit point is performed. The welding control device 3 outputs a command signal Sti, and measures various monitor values when welding is performed (step S16). That is, welding control device 3 takes in sensor signal Si of current sensor 60 to measure “current value”, takes in sensor signal Sp of pressure sensor 61, measures “pressing force”, and also uses inverter circuit 34. The PWM signal Spwm, which is the PWM duty value to be obtained, is taken in to measure the “usage rate”, and the conduction time is measured based on the clock signal from the clock unit 302. In addition, although the sensor signal St of the temperature sensor 62 is taken in and the "water temperature" of a cooling water is also measured, it abbreviate | omits here.

  The welding control device 3 treats each of “current value”, “energization time”, “pressing force” and “usage rate” measured at the time of welding as a monitor value, and stores the various setting values temporarily stored together with the storage unit The data is stored in 305 (step S17), and further, various monitor values and various setting values are associated with each other as data for one hit point and transmitted to the database server 5 (step S18). After transmitting various monitor values and various setting values for one hit point to the database server 5, the welding control device 3 returns to step S11. The processes from step S11 to step S18 are repeatedly performed.

  As described above, on the operation panel 18, "current value", "energization time", "pressing force", "material of work", "plate thickness of work", "work name" and "dock position on work" The “current value”, “energization time”, “pressing force” and “usage rate” are measured every time 1-point welding is performed by the resistance welder 2 with various set values of “1” set. Various monitor values and various setting values are associated with each other and transmitted to the database server 5.

(Operation of monitoring device 6)
FIG. 14 is a flowchart for explaining the operation of the monitoring device 6. Since the operation in the monitoring device 6 is performed by the control unit 601, the subject is the control unit 601. However, since the monitoring device 6 is described as the operation of the monitoring device 6 itself, the subject is the monitoring device 6.

  The monitoring device 6 first connects to the cloud 8 (step S30). When the connection with the cloud 8 is established, the monitoring device 6 determines whether a grouping condition is designated (step S31). That is, various setting values of "current value", "energization time", "pressing force", "material of work", "plate thickness of work", "work name" and "dock position on work", and "current" It is determined whether at least one of various monitor values of “value”, “energization time” and “pressing force” is designated.

  If the monitoring apparatus 6 determines that the grouping condition is not designated (that is, if it determines “No” in step S31), the main determination is repeated until the grouping condition is designated. On the other hand, if the monitoring apparatus 6 determines that the grouping condition is specified (that is, if it determines "YES" in step S31), it temporarily stores the specified grouping condition (step S32). As the grouping condition, for example, when the “current value” of the set value is designated, the “current value” is temporarily stored.

  After temporarily storing the designated grouping condition, the monitoring device 6 temporarily stores data of a predetermined period (for example, from the start of use to the present) of the resistance welding machine 2 stored in the database server 5 (ie, Various setting values and various monitor values are acquired (step S33). In addition, the period which acquires data is not limited from the use start time of the resistance welding machine 2 to the present, of course, it is also possible to be arbitrarily determined by a supervisor. For example, it may be from the second year after the start of use of the resistance welding machine 2 to the present. After acquiring various setting values and various monitor values for the predetermined period of the resistance welding machine 2, the monitoring device 6 stores the acquired various setting values and various monitor values (step S34).

  After storing the various setting values and the various monitor values, the monitoring device 6 divides the usage rate into groups using the designated grouping condition (step S35). That is, the monitoring device 6 groups the usage rates whose values are similar to each other using the designated grouping condition. Here, when the “current value” of the set value is designated as the grouping condition, the monitoring device 6 performs the grouping of the usage rate using the “current value”. When there are a plurality of grouping conditions, grouping of usage rates is performed using a plurality of conditions. For example, if the grouping condition is the “current value” and the “energization time” of the set values, the “current value” and the “energization time” are used to group the usage rates. In addition to the set value, the monitor value is also a grouping condition. For example, when the “current value” and the “energization time” of the monitor value are designated, the monitoring device 6 performs the grouping of the usage rate using the “current value” and the “energization time” of the monitor value. As described above, the monitoring device 6 performs grouping into those having similar values by using at least one of various setting values and various monitoring values.

  After grouping the usage rates into groups, the monitoring device 6 sets a threshold for each group (step S36). In setting the threshold for each group, an appropriate threshold is set by repeating the process of setting a value erroneously detected as abnormal and the process of setting a value not erroneously detected. Also, after setting an appropriate threshold value, the change amount calculated using the usage rate value stabilized by moving average processing so as to follow a gradual change due to a change in power supply voltage, a change in electrode tip, etc. Correct the threshold based on

  After setting the threshold for each group, the monitoring device 6 determines whether there is a group that exceeds the threshold (step S37). If the monitoring device 6 determines that any one group exceeds the threshold (that is, if “YES” in step S37), it determines whether the number of times the threshold is exceeded is equal to or greater than a predetermined number (step S38). If the monitoring device 6 determines that the number of times the threshold is exceeded is a predetermined number of times or more (that is, if it determines "YES" in step S38), it notifies the user of the resistance welding machine 2 of deterioration of the secondary cable 15A. (Step S39). The monitoring device 6 determines that the number of times the threshold is exceeded is a predetermined number or more, notifies the user of the resistance welder 2 of the deterioration of the secondary cable 15A, and then returns to the process of step S31.

  On the other hand, if the monitoring device 6 determines that the number of times the threshold is exceeded is not more than the predetermined number (that is, if "NO" in step S38), notification to the user of the resistance welder 2 is not performed. Return to the processing of In addition, if the monitoring device 6 determines that there is no group exceeding the threshold in the determination of step S37 (that is, if it determines “NO”), it returns directly to the process of step S31. The process of step S31-step S39 is repeatedly performed with respect to all the resistance welding machines 2 which the monitoring apparatus 6 monitors.

  As described above, according to the welding system 1 according to the present embodiment, the monitoring device 6 acquires a plurality of various setting values and various monitoring values from the database server 5, and uses included in each of the plurality of acquired various monitoring values As the rate is divided into groups of similar values using at least one of various setting values and various monitoring values, the fluctuation range of the utilization rate can be narrowed, and the deterioration of the secondary cable 15A can be made early. It can be detected.

  Further, since a detector or the like specialized for detecting deterioration of the secondary cable 15A is not required, it is possible to realize deterioration detection of the secondary cable 15A at low cost.

  In addition, the monitoring device 6 sets a threshold for each group, and notifies the user of the resistance welding machine 2 of deterioration of the secondary cable 15A when the threshold is exceeded in each group, so the user of the resistance welding machine 2 The secondary cable 15A of the welding machine 2 can be replaced before it can not be used, and a decrease in productivity can be prevented.

  Also, the monitoring device 6 calculates the moving average of the usage rate for each group, sets a threshold for detecting deterioration of the secondary cable 15A to the moving average obtained by this, and further, from the moving average Since the gradual change over time of the usage rate is calculated and the threshold value is corrected based on the obtained change, fluctuation of the power supply voltage and the tip of the electrode tip (attached to the tip of the welding gun) are used. Even if a gradual change such as a change is included, the deterioration of the secondary cable 15A can be detected without erroneous detection.

  Although the invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  For example, the deterioration of the secondary cable 15A may be detected not from the change in the level of the utilization rate but from the change in the inclination of the use rate. That is, a threshold for the gradient of the moving average of the usage rate is set, and when the gradient of the moving average of the usage rate exceeds the threshold, it is determined that the secondary cable 15A has deteriorated.

  Further, the threshold set for each group may be corrected with reference to the threshold set in each of the many other resistance welders 2-2, 2-3,. By doing this, the setting accuracy of the threshold can be enhanced, and deterioration of the secondary cable 15A can be detected more reliably. In particular, the accuracy can be further enhanced by referring to the threshold set in the one of the other resistance welding machines 2-2, 2-3,.

  Further, the deterioration of the secondary cable 15A may not be grasped by the utilization rate itself, but the deterioration of the secondary cable 15A may be grasped by a value obtained by replacing the utilization rate with a resistance equivalent. By replacing the usage rate with resistance, it is possible to intuitively grasp the deterioration state of the secondary cable 15A. Hereinafter, a method of replacing the usage rate with resistance will be described.

The resistance of the secondary cable 15A, the resistance of the work 500 and the total resistance of the welding gun 14 are measured as secondary resistance. Also, the secondary voltage and secondary current of the welding transformer 19 are measured, and the resistance value of the secondary circuit is measured.
The secondary resistance equivalent of the usage rate (PWM duty value) can be represented by secondary voltage × (PWM duty value) / current. An example is given below.

Secondary voltage = power supply voltage × √2 / turn ratio of welding transformer 19 −0.7 V
Here, assuming that the power supply voltage: AC 400 V, and the turns ratio of the welding transformer 19: 50,
Secondary voltage = 400 × 2 2/50-0.7V = 10.6V (about 11V)
Current: 10KA, PWM duty value: 60%,
The equivalent of the secondary resistance = 11 V × 60% / 10 KA = about 660 μΩ.

  Moreover, it is also possible to use resistance between chips instead of using a usage rate as a grouping target. As well known, the resistance between chips can be obtained by dividing the voltage between chips by the welding current. The resistance between chips is divided into groups of similar values using at least one of various setting values and various monitoring values. The processing after grouping is the same as in the case of using the usage rate.

  In addition, as a grouping condition, various kinds of “current value”, “energization time”, “pressing force”, “material of work”, “plate thickness of work”, “work name” and “dock position on work” A condition that the user of the resistance welder 2 does not want to display on the surface instead of enabling all the set values and various monitor values of “current value”, “energization time” and “pressing force” (eg “current value” ") May be disabled. That is, the grouping of the usage rates may be performed only with data that the user of the resistance welding machine 2 thinks that it may be exposed.

  Further, the monitoring device 6 does not detect deterioration of the secondary cable 15A of the resistance welder 2 but causes the PC 7 to have the function of the monitoring device 6, and the PC 7 detects deterioration of the secondary cable 15A of the resistance welder 2 May be performed. That is, an application in which the function of the monitoring device 6 is programmed is installed in the PC 7. The PC 7 operates in accordance with the application, acquires various setting values and various monitor values from the database server 5, and performs deterioration detection of the secondary cable 15A of the resistance welding machine 2.

  Also, besides detecting deterioration of the secondary cable 15A of the resistance welding machine 2 with the PC 7, a functional tool & data processing tool (not shown) is constructed on the cloud 8, and this functional tool & data processing tool performs resistance welding The deterioration detection of the secondary cable 15A of the machine 2 may be performed. In this case, the functional tool & data processing tool acquires various setting values and various monitor values from the database server 5. The monitoring device 6 notifies the user of the resistance welder 2 of the deterioration of the secondary cable 15A when the deterioration of the secondary cable 15A is detected by the functional tool & data processing tool.

  In addition, it is possible to detect a sudden change of the usage rate that occurs when the secondary cable 15A is in a substantially disconnected state, and to detect the deterioration of the secondary cable 15A. The sudden change of the usage rate is a change amount embedded in noise when moving average is performed, and is a rapid change exhibiting a peak value larger than the noise. Detection of a sudden change in utilization is detected using a value before moving average of utilization. The reason is that moving averages of usage rates equalize the values, so the peak value of the sudden change in usage rate becomes smaller and is buried in noise.

  FIG. 15 is a diagram showing an example of a sudden change in the usage rate that occurs when the secondary cable 15A is about to break, where the horizontal axis is the hitting point (or time) and the vertical axis is the usage rate (PWM duty value ). When the secondary cable 15A starts to break, a sudden change in the utilization rate occurs for each group as shown in the figure. When a sudden change in the utilization rate occurs, it is determined that the secondary cable 15A has deteriorated, but since the moving average of the utilization rate is not taken, even if a sudden change appears, There may be a factor other than the onset of disconnection of the next cable 15A. Therefore, it may be determined that the secondary cable 15A has deteriorated when it occurs with a certain frequency. Note that the detection of a sudden change in the usage rate and the detection of a gradual (relative to a sudden change) change in the usage rate described in the embodiment may be performed continuously, or either One of them may be selected to detect it.

  As described above, since the threshold value for detecting the deterioration of the secondary cable 15A with respect to the rapid change of the utilization rate is set, the sudden occurrence of the utilization rate generated when the secondary cable 15A is in a substantially disconnected state Change can be captured.

  The present invention has the effect of being able to detect abnormalities on the welding current flow path including the deterioration of the secondary cable connecting the welding transformer and the welding gun in a resistance welding machine early and at low cost, It is suitable for a welding machine.

DESCRIPTION OF SYMBOLS 1 welding system 2, 2- 1, 2- 2, 2- n resistance welding machine 3, 3- 1,3- 2,3- n welding control apparatus 4 Web server 5 database server 6 monitoring apparatus 7 PC
8 Cloud 10 Cooling Unit 11 Power Supply Unit 12 Support Post 13 Support Arm 14 Welding Gun 15A, 15B Secondary Cable 16 Table Electrode 17 Table Drive 18 Operation Panel 19 Weld Transformer 25 Electrode Tip 26 Cylinder 31 Rectifier 32 Smoothing Capacitor 34 Inverter Circuit 301, 601 control unit 302 clock unit 303 counter unit 304 interface unit 305, 602 storage unit 306, 605 communication unit 307, 606 common bus 60 current sensor 61 pressure sensor 62 temperature sensor 194 first rectifying element 195 second rectifying element 341 inverter Control circuit 342 Switch using IGBT 343 Current sensor 500 Work 603 Operation unit 604 Display unit

The welding system of the present invention can be connected to a resistance welding machine that performs welding while pressing a work with two opposing electrodes, and to cloud computing, and the current value, energization time, pressing force, material of the work, A welding control device that generates a command signal for operating the resistance welding machine based on various setting values including a thickness of a work, a work name, and a hit position on the work, and measures a usage rate based on a PWM duty signal And a welding transformer for supplying a high frequency alternating current to the primary side and outputting a direct current obtained by rectifying the high frequency alternating current from the secondary side, and the command signal generated by the welding control device and the primary flowing through the primary side of the welding transformer. An inverter control circuit that generates a high frequency alternating current that is PWM controlled based on current and supplies it to the primary side of the welding transformer, and outputs the PWM duty signal , And the database server built on the cloud computing, said built on cloud computing, a welding system and a Akuseasu capable monitoring device in the database server, the welding control apparatus, the When welding is performed with a resistance welder, various monitor values including current value, current application time, pressure, and usage rate are measured, and the various set values when welding is performed with the resistance welder are acquired , The acquired various setting values and the measured various monitor values are associated with each other and transmitted to the database server, and the monitoring device acquires a plurality of the associated various setting values and the various monitor values from the database server. The various setting values for the usage rates included in each of the plurality of various monitor values acquired Using at least any one of the fine the various monitor values, and grouped into each other what values are approximate, to detect the abnormality of the welding electric distribution flow on the route for each group.

The abnormality detection method on the welding current flow path in the welding system of the present invention can be connected to a resistance welding machine that performs welding while holding a work between two opposing electrodes, and to cloud computing. Generates a command signal to operate the resistance welder based on various setting values including energization time, pressing force, workpiece material, workpiece thickness, workpiece name and workpiece position on workpiece, and PWM duty signal Welding control device which measures usage rate on the basis, a welding transformer which supplies high frequency alternating current to the primary side and outputs direct current obtained by rectifying the high frequency alternating current from the secondary side, and the command generated by the welding control device A high frequency alternating current that is PWM controlled based on a signal and a primary current flowing on the primary side of the welding transformer is generated and supplied to the primary side of the welding transformer; Run and an inverter control circuit for outputting a Ti signal, and a database server that is built on the cloud computing, it said built on cloud computing, in a welding system and a Akuseasu capable monitoring device in the database server Method of detecting deterioration of a part on a welding current flow path, wherein, when welding is performed by the resistance welding machine, various monitor values of current value, energization time, pressurizing force and usage rate are measured, and The steps of acquiring the various setting values when welding is performed by a resistance welding machine, associating the measured various monitor values and the acquired various setting values, and transmitting the same to the database server, and the database A plurality of the various setting values and the various monitor values associated with each other are acquired from the server, The usage rates included in each of the plurality of various monitor values obtained are grouped into those having similar values by using at least any one of the various setting values and the various monitor values, and a group is formed. Detecting an abnormality on the welding current flow path each time.

The welding system of the present invention can be connected to a resistance welding machine that performs welding while pressing a work with two opposing electrodes, and to cloud computing, and the current value, energization time, pressing force, material of the work, A welding control device that generates a command signal for operating the resistance welding machine based on various set values including the thickness of a work, the work name and the position on the work, and measures the PWM duty value based on the PWM duty signal And, a high frequency alternating current is supplied to the primary side, and a welding transformer that outputs a direct current obtained by rectifying the high frequency alternating current from the secondary side, and the command signal generated by the welding control device and the primary side of the welding transformer An inverter which generates a high frequency alternating current controlled by PWM based on a primary current and supplies it to the primary side of the welding transformer, and outputs the PWM duty signal. A motor control circuit, and a database server that is built on the cloud computing, built on the cloud computing, a welding system and a accessible monitoring device in the database server, the welding control The apparatus measures various monitor values including a current value, an energization time, a pressing force and a PWM duty value when welding is performed by the resistance welding machine, and the welding when the welding is performed by the resistance welding machine. The various setting values are acquired, the acquired various setting values and the measured various monitor values are associated and transmitted to the database server, and the monitoring device associates the various setting values and the various items associated from the database server. multiple captures a monitor value, the PWM de included in the plurality of various monitor values respectively obtained For Ti values, using said at least any one of various setting values and the various monitor values, and grouped into each other what values are approximate, to detect the abnormality of the welding electric distribution flow on the path for each group .

According to the above configuration, since the PWM duty values included in each of the plurality of various monitor values are grouped into at least two, the fluctuation range of the PWM duty value in each group becomes narrow. The above abnormalities can be detected early.

The abnormality detection method on the welding current flow path in the welding system of the present invention can be connected to a resistance welding machine that performs welding while holding a work between two opposing electrodes, and to cloud computing. Generates a command signal to operate the resistance welder based on various setting values including energization time, pressing force, workpiece material, workpiece thickness, workpiece name and workpiece position on workpiece, and PWM duty signal A welding control device for measuring a PWM duty value based on the welding control device; a welding transformer for supplying a high frequency alternating current to the primary side and outputting a direct current obtained by rectifying the high frequency alternating current from the secondary side; A high frequency alternating current which is PWM-controlled based on a command signal and a primary current flowing on the primary side of the welding transformer is generated and supplied to the primary side of the welding transformer, Serial and inverter control circuit for outputting a PWM duty signal, the cloud and computing database server built on computing, built on the cloud computing, welding system and an accessible monitoring device in the database server A method of detecting deterioration of a part on a welding current flow path performed in the step of measuring various monitor values of current value, energization time, pressing force and PWM duty value when welding is performed by the resistance welding machine And acquiring the various setting values when welding is performed by the resistance welding machine, and associating the measured various monitoring values and the acquired various setting values and transmitting them to the database server. The various setting values and the various items associated from the database server The Nita value obtains a plurality, for the PWM duty value contained in each acquired plurality of various monitored values, using at least one among the various set values and the various monitor values, the values are approximate And grouping the objects into groups, and detecting an abnormality on the welding current flow path for each group.

According to the above method, since the PWM duty values included in each of the plurality of various monitor values are grouped into at least two, the fluctuation range of the PWM duty value in each group becomes narrow, so the welding current flow path The above abnormalities can be detected early.

In addition, when welding is performed by the resistance welder 2, the welding control device 3 obtains the sensor signal Si of the current sensor 60, the sensor signal Sp of the pressure sensor 61, and the PWM duty obtained by the inverter control circuit 341 of the inverter circuit 34. The signal Spwm is taken in, and "current value", "energization time", "pressing force" and " PWM duty value " are measured. The welding control device 3 treats each of the measured "current value", "energization time", "pressing force" and " PWM duty value " as monitor values. Hereinafter, the PWM duty value will be referred to as "usage rate" or "usage rate (PWM duty value)".

After generating the command signal Sti, the welding control device 3 outputs the command signal Sti to the power supply unit 11 of the resistance welder 2 (step S15). Thereby, welding for one hit point is performed. The welding control device 3 outputs a command signal Sti, and measures various monitor values when welding is performed (step S16). That is, welding control device 3 takes in sensor signal Si of current sensor 60 to measure “current value”, takes in sensor signal Sp of pressure sensor 61, measures “pressing force”, and also uses inverter circuit 34. The PWM duty signal Spwm obtained is taken in to measure the “ PWM duty value ”, and the conduction time is measured based on the clock signal from the clock unit 302. In addition, although the sensor signal St of the temperature sensor 62 is taken in and the "water temperature" of a cooling water is also measured, it abbreviate | omits here.

Claims (3)

A resistance welder that welds while pinching the workpiece with two opposing electrodes,
Connection to cloud computing is possible, and the resistance welding machine is based on various setting values including current value, energizing time, pressing force, workpiece material, workpiece thickness, workpiece name and hitting position on workpiece Welding control device to control,
A database server built on the cloud computing;
A monitoring device built on the cloud computing and accessible to the database server;
A welding system equipped with
The welding control device measures various monitor values including a current value, an energization time, a pressing force and a usage rate when welding is performed by the resistance welding machine, and welding is performed by the resistance welding machine. Acquiring the various setting values, and associating the acquired various setting values and the measured various monitor values with each other, and transmitting them to the database server;
The monitoring device acquires a plurality of the various setting values and the various monitor values associated with each other from the database server, and the various setting values and the information regarding the usage rate included in each of the plurality of acquired various monitor values. A welding system that groups at least one of various monitor values into groups with similar values and detects an abnormality on a welding current flow path for each group.   The said monitoring apparatus sets a threshold value for every said group, and when there exists a group exceeding the set said threshold value, it notifies the user on the said resistance welding machine of the abnormality on the said welding current flow path. Welding system. A resistance welder that welds while pinching the workpiece with two opposing electrodes,
Connection to cloud computing is possible, and the resistance welding machine is based on various setting values including current value, energizing time, pressing force, workpiece material, workpiece thickness, workpiece name and hitting position on workpiece Welding control device to control,
A database server built on the cloud computing;
A monitoring device built on the cloud computing and accessible to the database server;
A method of detecting deterioration of parts on a welding current flow path, the method being performed in a welding system comprising:
While welding is performed by the resistance welding machine, various monitor values of current value, energization time, pressing force and usage rate are measured, and the various setting values when welding is performed by the resistance welding machine are acquired. Step to
Associating the measured various monitor values with the acquired various setting values and transmitting them to the database server;
The various setting values and the various monitor values associated with each other are acquired from the database server, and among the various setting values and the various monitor values, the usage rate included in each of the acquired various monitor values is acquired. Grouping at least one of the values into which the values are similar, and detecting an abnormality on the welding current flow path for each group;
A method of detecting an abnormality on a welding current flow path in a welding system, comprising: