JP3767271B2 - Resistance welding machine control device and resistance welding machine control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a control apparatus and a control method for a resistance welding machine, and more specifically, by detecting signs of occurrence of scattering based on a rate of change in welding power over time and reducing welding power before the occurrence of scattering, The present invention relates to a control device and a control method for a resistance welding machine that suppresses the occurrence of scattering.
[0002]
[Prior art]
  In resistance welding, the occurrence of scattering has become a problem in terms of quality and safety. For this reason, various techniques for suppressing the occurrence of scattering and improving the welding quality have been proposed as described below.
[0003]
  In Japanese Patent Laid-Open No. 54-58655 (Japanese Patent Publication No. 57-37430), a change in the thickness of a member at a welding point during energization time is detected, and scattering occurs when the amount of change exceeds a reference value. A resistance that reduces the welding current by a predetermined amount when scattering occurs, and increases the welding current by a predetermined amount when scattering does not occur, so that the welding current is controlled along the scattering occurrence limit current value. A spot welding control method is described.
[0004]
  In JP-A-6-344155, the occurrence of scattering is predicted by comparing the voltage between the electrodes and a reference value, and by taking measures according to the prediction result, suppression of the occurrence of scattering and uniform welding nugget diameter is achieved. A control device for a spot welder that can perform welding is described. The occurrence of scattering can be suppressed by reducing the amount of current only for a predetermined period during welding energization. It has been experimentally confirmed that scattering is likely to occur during this predetermined period. This predetermined period is a period during which the area of the current path between the workpieces is about to suddenly expand. By reducing the welding current during this period, the area of the welding current path is gently expanded, thereby suppressing the occurrence of scattering. Since the presence or absence of scattering is predicted based on whether or not the voltage between the electrodes exceeds the reference value, the occurrence of scattering can be effectively suppressed.
[0005]
  In Japanese Patent Laid-Open No. 9-216070, from the energy distribution estimated using the welding current and the voltage between the electrodes, the risk of occurrence of scattering and the estimated time of occurrence of scattering are estimated, and immediately after the welding time set for the estimated time of occurrence of scattering is set. A control apparatus for a resistance welder is described in which the welding current is changed and controlled so that heat input is increased without causing scattering and a nugget having the maximum strength is obtained.
[0006]
  In Japanese Patent Laid-Open No. 10-94883, welding current and chip-to-chip voltage are detected, the weld is simulated by heat conduction calculation, and the nugget generation state is estimated to perform good welding. A welding condition control method for a resistance welder is described.
[0007]
[Problems to be solved by the invention]
  Japanese Patent Application Laid-Open No. 54-58655 controls the welding current when the occurrence of scattering is detected. For this reason, when scattering occurs, the welding current can be reduced or the supply of the welding current can be stopped, but the occurrence of scattering cannot be prevented in advance.
[0008]
  The control apparatus for a spot welder described in Japanese Patent Laid-Open No. 6-344155 is based on the reference inter-electrode voltage obtained by experiments in advance and the actual inter-electrode voltage generated when welding with a current slightly smaller than the scattering occurrence limit current. Is compared with the inter-electrode voltage detected, and the presence or absence of scattering is predicted depending on whether or not the actually detected inter-electrode voltage exceeds the reference inter-electrode voltage. The voltage between the reference electrodes is determined by experiments in advance.SeekingAs a result, even if the actually detected interelectrode voltage exceeds the reference interelectrode voltage only slightly and no scattering occurs, the occurrence of scattering may be predicted.
[0009]
  The resistance welding machine control device described in Japanese Patent Laid-Open No. 9-216070 requires a large number of arithmetic processes in order to estimate the energy distribution. This complicates the configuration of the control device. Since the welding condition control method for a resistance welder described in Japanese Patent Laid-Open No. 10-94883 is a configuration using a heat conduction simulator, the configuration of the control device and the like is complicated.
[0010]
OBJECT OF THE INVENTION
  The present invention has been made to solve such problems. Precisely predicts the occurrence of scattering with a relatively simple configuration, and controls the amount of heat generated in the welded portion based on the prediction result to achieve good welding. It is an object of the present invention to provide a control device and a control method for a resistance welder that can perform the above.
[0011]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, a resistance welding machine control device according to claim 1 comprises:Detect welding current A current detection unit, a voltage detection unit that detects a voltage between welding electrodes, and a welding power change rate calculation that calculates welding power based on the welding current and the welding electrode voltage and calculates a time change rate of the welding power And a welding power control means for reducing the welding power by determining that it is a sign of occurrence when the rate of change of the welding power over time exceeds a preset allowable increase rate of the welding power during the nugget growth period. It has. The welding power control means immediately stops the supply of the welding power when the time change rate of the welding power exceeds the allowable increase rate, and sets the supply amount of the welding power thereafter in a predetermined period. Reduce over time.
[0012]
  The resistance welding machine control device according to claim 1 monitors the time change rate of the welding power during the nugget growth period, and the time change rate of the welding power is preset.Below the allowable increase rateThe welding power is controlled so that By monitoring the rate of change in welding power over time, signs of a change in welding power can be quickly detected. As a result, the welding power can be reduced before the welding power becomes excessive during the nugget growth period and scattering occurs, and the occurrence of scattering can be prevented in advance. Further, it is possible to prevent the welding power from becoming too low during the nugget growth period and reducing the welding quality.
[0013]
  A control device for a resistance welder according to claim 2 is:A voltage detector for detecting the voltage between the welding electrodes, an interelectrode voltage change rate calculating means for calculating the time change rate of the welding electrode voltage, and the time change rate of the welding electrode voltage during the nugget growth period are preset. Welding power control means for reducing the welding power by judging that it is a sign of occurrence when the allowable increase rate of the voltage between the welding electrodes is exceeded. The welding power control means immediately stops the supply of the welding power when the rate of change over time of the voltage between the welding electrodes exceeds the allowable increase rate, and determines the supply amount of the welding power thereafter. Reduce over time.
[0014]
  The resistance welding machine control device according to claim 2 is the nugget growth period.Voltage between welding electrodesMonitor the rate of time change ofVoltage between welding electrodesThe time change rate ofAllowable increase rateIf it exceeds, it is judged as a sign of the occurrence of scattering and the welding power is reduced. Therefore, the occurrence of scattering can be prevented in advance.
[0015]
  Control of resistance welding machine according to claim 3MethodIsThe welding current and the voltage between the welding electrodes are detected, the welding power is calculated based on the detected welding current and the voltage between the welding electrodes, the time change rate of the welding power is calculated, and the welding power of the welding power is calculated during the nugget growth period. When the time change rate exceeds a preset allowable increase rate of the welding power, it is judged as a sign of occurrence of scattering and the welding power is reduced. And when the time change rate of the said welding electric power exceeds the said allowable increase rate, while the supply of the said welding electric power is stopped immediately, the supply amount of the said welding electric power after that is reduced over a predetermined period.
[0016]
  Control of resistance welding machine according to claim 3MethodIn the nugget growth periodWelding powerMonitor the rate of time change ofWelding powerThe time change rate ofAllowable increase rateIf it exceeds, it is judged as a sign of the occurrence of scattering and the welding power is reduced. Therefore, the occurrence of scattering can be prevented in advance.
[0017]
  The control method of the resistance welder according to claim 4 is:The voltage between the welding electrodes is detected, the time rate of change of the detected voltage between the welding electrodes is calculated, and the time rate of change of the voltage between the welding electrodes in the nugget growth period is set to the allowable increase rate of the voltage between the welding electrodes. If it exceeds, it is judged as a sign of the occurrence of scattering and the welding power is reduced. When the time change rate of the voltage between the welding electrodes exceeds the allowable increase rate, the supply of the welding power is immediately stopped and the supply amount of the welding power thereafter is reduced over a predetermined period.
[0018]
  The control method of the resistance welder according to claim 4 is the nugget growth period.Welding electrode voltageMonitor the rate of time change ofWelding electrode voltageWhen the rate of change in time exceeds a preset allowable increase rate, it is judged as a sign of occurrence of scattering and the welding power is reduced. Therefore, the occurrence of scattering can be prevented in advance.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0020]
  FIG. 1 is a block diagram of a resistance welding machine control apparatus according to the present invention. A resistance welding machine control device 1 according to the present invention includes a three-phase AC power source 2, a three-phase full-wave rectification unit 3, an inverter unit 4, a step-down transformer 5, a rectification unit 6, a pair of welding electrodes 7a, 7b, a voltage detector 8, a current detector 9, and a controller 10. The control unit 10 includes a welding power change rate calculation unit 11, a standard range storage unit 12, a welding power control unit 13, and an inverter drive circuit 14. Reference numeral 30 is an object to be welded, and reference numeral 31 is a nugget (dissolving part).
[0021]
  The three-phase full-wave rectification unit 3 generates a DC power source by full-wave rectifying the three-phase AC supplied from the three-phase AC power source 2. The generated DC power is supplied to the inverter unit 4. The inverter unit 4 converts the DC power source into high-frequency AC and drives the primary winding of the step-down transformer 5. The inverter unit 4 includes four power semiconductor switching elements (for example, IGBTs) connected in an H-type bridge. The inverter unit 4 generates high-frequency alternating current by switching each power semiconductor switching element in a predetermined order based on a plurality of drive signals 10 a supplied from the inverter drive circuit 14 in the control unit 10. The welding power control means 13 in the control unit 10 controls the output power of the inverter 4 by changing the duty of the PWM signal 13a supplied to the inverter drive circuit 14, and thereby the step-down transformer 5, the rectification unit 6, the welding power. The welding electric power supplied to the to-be-welded part 30 via 7a, 7b is controlled. A low-frequency high-frequency alternating current is induced in the secondary winding of the step-down transformer 5. This low-frequency high-frequency alternating current is converted into direct current by the rectifier 6. The rectifying unit 6 includes two rectifying diodes 6a and 6b. The pulsating flow generated by the rectifying unit 6 is supplied to the welded part 30 via the welding electrodes 7a and 7b.
[0022]
  The voltage detector 8 detects the voltage between the pair of welding electrodes 7a and 7b, and outputs an electrical signal (voltage detection signal) 8a corresponding to the detected voltage. This voltage detection signal 8 a is supplied to the welding power change rate calculation means 11 in the control unit 10.
[0023]
  The current detection unit 9 detects a welding current and outputs an electrical signal (current detection signal) 9a corresponding to the detected welding current. This current detection signal 9 a is supplied to the welding power change rate calculation means 11 in the control unit 10.
[0024]
  The welding power change rate calculating means 11 calculates the welding power instantaneous value 11a at a preset time interval based on the voltage detection signal 8a and the current detection signal 9a, and also calculates the welding power instantaneous value time change rate 11b. calculate. The calculated instantaneous value 11a of the welding power and the temporal change rate 11b of the instantaneous value of the welding power are supplied to the welding power control means 13.
[0025]
  The standard range storage means 12 stores a standard range of the rate of change in welding power over time during the nugget growth period after the welding power reaches its maximum value. The standard range of the time change rate of the welding power is obtained by setting an upper limit value and a lower limit value every time the nugget growth period elapses.
[0026]
  The welding power control means 13 generates a PWM signal 13a based on the command value and supplies it to the inverter drive circuit 14 to start supplying the welding power, and each PWM modulation period based on the instantaneous value 11a of the welding power. The maximum value of the welding power integral value for each time or the instantaneous value 11a of the welding power for each PWM modulation period is obtained.
[0027]
  The welding power control means 13 monitors the change in the welding power integral value for each PWM modulation period or the maximum value of the instantaneous value 11a of the welding power for each PWM modulation period, and the welding power integral value for each PWM modulation period or Based on the fact that the maximum value of the instantaneous value 11a of the welding power for each PWM modulation period has reached the maximum value (maximum point), the temperature increase period shown in FIG. 2 ends and the decrease period (nugget growth period) starts. Recognize that. The descent period (nugget growth period) is a heating suppression period due to the autonomous action of welding.
[0028]
  When the welding power control means 13 enters the descending period (nugget growth period), the welding power integral value or the maximum value of the welding power instantaneous value 11a in the previous PWM modulation period, and the welding power in the current PWM modulation period. The rate of change from the integrated value or the maximum value of the instantaneous value 11a of the welding power is calculated. Then, the time change rate of the welding power for each PWM modulation period calculated is compared with the standard range, and if the time change rate of the welding power for each PWM modulation period exceeds the upper limit value of the standard range, the PWM signal By reducing the duty of 13a, the welding power is reduced, and when the rate of change in welding power over time for each PWM modulation period exceeds the lower limit of the standard range, the duty of PWM signal 13a is increased. Increase welding power. Thereby, the time change rate of the welding power for each PWM modulation period is controlled to be within a preset standard range.
[0029]
  Further, the welding power control means 13 immediately stops the output of the PWM signal 13a that is currently output when the temporal change rate 11b of the instantaneous value of the welding power exceeds a preset scattering sign detection value. At the same time, the duty of the PWM signal 13a is changed to an extremely small value over a period of several cycles from the next PWM modulation cycle. By detecting the sign of the occurrence of scattering and reducing the power supply, the occurrence of scattering can be prevented in advance.
[0030]
  FIG. 2 is a graph showing a change characteristic of the voltage between electrodes during welding, a change rate of welding power, and a change characteristic of power consumption. In FIG. 2, the period from time 0 to time t0 is a preliminary energization period. In this preliminary energization period, the workpiece is heated, the contact resistance disappears, and the voltage between the electrodes drops. The length of this pre-energization period can be obtained statistically. Time t0 to time tp is a temperature rise period. In this temperature rise period, the workpiece is heated and the temperature rises. The peak time tp can be obtained based on the maximum point of the welding power. From time tp to time te is a descending period. After the peak time tp, the voltage between the electrodes decreases due to the autonomous action of welding. This falling period is a period during which the nugget grows. Time te is the energization end time. After the energization end time te, the energization current is gradually decreased as an end process. The area shown by hatching in FIG. 2B is the standard range of the welding power change rate.
[0031]
  FIG. 3 is an explanatory diagram showing an operation of detecting the sign of occurrence of scattering and reducing welding power. 3A shows a change characteristic of welding power, FIG. 3B shows a welding power change rate (welding power differential value), and FIG. 3C shows a switching pulse (supply power). Scattering is known to occur during the descent period (nugget growth period). As shown in FIG. 3A, welding power increases when scattering occurs. This increase in welding power is detected as a change in the welding power change rate. That is, as shown in FIG. 3 (b), the welding power change rate changes abruptly before the occurrence of scattering. This rapid change in the welding power change rate is taken as a sign of the occurrence of scattering, and the supplied power is suppressed as shown in FIG. Thereby, the occurrence of scattering can be prevented in advance.
[0032]
  FIG. 4 is a welding power waveform diagram showing an example of a power waveform during welding when the supply of welding power is controlled by an AC resistance welding machine. In FIG. 4, the horizontal axis represents time, and the vertical axis represents welding power. Here, an example is shown in which scattering occurs at two points (a) and (b) during the falling period (nugget growth period). 5 and 6 are welding power waveform diagrams in which the time axis of the welding power waveform shown in FIG. 4 is enlarged. 7 and 8 are power waveform diagrams showing power waveforms before and after the occurrence of scattering.
[0033]
  The welding power change rate calculating means 11 shown in FIG. 1 includes a D / A converter for D / A converting the interelectrode voltage 8a, and a D / A converter for D / A converting the welding current 9a. It has. The welding power change rate calculation means 11 samples the inter-electrode voltage 8a and the welding current 9a at the same timing using the two D / A converters in a short period of, for example, 1/100 or more of the PWM modulation period. Thus, obtaining each D / A conversion data is sequentially repeated. Then, the instantaneous value 11a of the welding power is calculated by multiplying the interelectrode voltage and the welding current based on the interelectrode voltage data and the welding current data, and the calculated welding power instantaneous value 11a is used as the welding power control means. 13 are sequentially supplied. The welding power change rate calculation means 11 calculates a change rate between the instantaneous value of the welding power calculated based on the previous sampling and the instantaneous value of the welding power calculated based on the current sampling, and the calculated instantaneous change rate 11b. Are sequentially supplied to the welding power control means 13.
[0034]
  The welding power control means 13 integrates the instantaneous value 11a of the welding power sequentially supplied at a short cycle of, for example, 1/100 or more of the PWM modulation cycle over one PWM modulation cycle, so that each PWM modulation cycle. Find the welding power of
[0035]
  As shown in FIG. 2 (c), the welding power continues to increase during the temperature rise period, and starts the descent period (nugget growth period) from the time when the welding power exceeds the maximum value (maximum value). The welding power control means 13 recognizes that the temperature rise period is based on the fact that the welding power for each PWM modulation period continues to increase. The welding power control means 13 recognizes that the falling period (nugget growth period) has been entered based on the fact that the welding power of the current PWM modulation period is equal to or decreased with respect to the welding power of the previous PWM modulation period.
[0036]
  When the welding power control means 13 recognizes that it has entered the falling period (nugget growth period), each PWM is calculated to calculate the rate of change between the welding power in the previous PWM modulation period and the welding power in the current PWM modulation period. Repeat every modulation period. The welding power control means 13 compares the calculated change rate of the welding power with the change rate set as the standard range. When the calculated welding power change rate exceeds the upper limit of the standard range, the welding power control means 13 reduces the duty of the PWM signal 13a generated in the next PWM modulation period by a predetermined value. To do. Thereby, the welding power of the next PWM modulation period is reduced. When the calculated welding power change rate exceeds the lower limit value of the standard range, the welding power control means 13 increases the duty of the PWM signal 13a generated in the next PWM modulation period by a predetermined value. To do. Thereby, the welding power of the next PWM modulation period is increased.
[0037]
  The welding power control means 13 obtains the maximum value of the instantaneous value of the welding power in each PWM modulation period without obtaining the welding power for each PWM modulation period, and the falling period (nugget growth period) based on the change in the maximum value. ) May be recognized. The welding power control means 13 calculates the change rate of the maximum value of the instantaneous value of the welding power in each PWM modulation period, and controls the welding power by comparing the calculated change rate with the standard range. Also good.
[0038]
  When the welding power control means 13 recognizes that it has entered the falling period (nugget growth period), the change between the instantaneous value of the welding power calculated by the previous sampling and the instantaneous value of the welding power calculated by the current sampling. If the rate (instantaneous change rate) exceeds a preset rate of increase (allowable rate of increase), this is regarded as a sign of the occurrence of scattering and the output of the PWM signal 13a that is currently output is immediately stopped. The welding power control means 13 changes the duty of the PWM signal 13a to an extremely small value over a period of several cycles from the PWM modulation cycle next to the PWM modulation cycle in which the output of the PWM signal 13a is forcibly stopped. The occurrence of scattering is prevented by reducing the power supply over a predetermined period after the sign of occurrence of scattering is detected.
[0039]
  As shown in FIGS. 7 and 8, when scattering occurs, a rapid increase in welding power occurs as an indication. Therefore, by monitoring the rapid increase in welding power, the sign (A) shown in FIG. 7 and the sign (B) shown in FIG. 8 can be detected, and the sign (A), sign (B)By immediately stopping the supply of welding power at the time of detection, it is possible to prevent the occurrence of scattering that occurs approximately 1 to 2 milliseconds after the signs (A) and (B).
[0040]
  FIG. 9 is a flowchart showing the operation of the control device 1 of the resistance welder shown in FIG. In step S1, energization is started in step S2 after the welding conditions are set corresponding to the material, plate thickness, etc. of the workpiece. In step S3, it is determined whether or not the elapsed time t from the start of energization has reached the preliminary energization time (preliminary energization end time) t0.
[0041]
  When the preliminary energization period ends, the temperature rises. In this temperature rise period, the welding power for each PWM modulation period is calculated in step S4, and it is determined whether or not the welding power is increased in step S5. If the welding power is increasing, it is checked in step S6 whether or not the energization end time te has been reached. If the increase in welding power continues even after the energization end time te is reached, it is determined in step S7 that the nugget generation is defective, and in step S8, a display indicating that the energization has stopped and an abnormality has occurred is displayed. Anomaly processing is performed.
[0042]
  When it is detected in step S5 that the temperature increase period has ended, processing in the nugget growth period after step S9 is started. In step S9, it is determined whether or not the instantaneous change rate of the welding power exceeds the allowable increase rate. If the instantaneous change rate of the welding power exceeds the allowable increase rate, a scattering prevention process is performed in step S10. In this scattering prevention processing, the output of the currently output PWM signal 13a is immediately stopped and the duty of the PWM signal 13a is set to a very small value over several cycles from the next PWM modulation cycle. The supply amount of the welding power is greatly reduced over a predetermined time from the time when the instantaneous change rate of exceeds the allowable increase rate. This prevents the occurrence of scattering.
[0043]
  If the instantaneous change rate of the welding power does not exceed the allowable increase rate, the welding power is integrated in step S11. When it is detected in step S12 that one PWM modulation cycle has ended, the rate of change between the welding power in the previous PWM modulation cycle and the welding power in the current PWM modulation cycle exceeds the upper limit of the standard range in step S13. In step S14, it is determined whether the rate of change between the welding power in the previous PWM modulation period and the welding power in the current PWM modulation period exceeds the lower limit of the standard range.
[0044]
  When the rate of change from the welding power exceeds the upper limit value of the standard range, a supply power reduction process is performed in step S15. In this supply power reduction process, the duty of the PWM signal 13a in the next PWM modulation cycle is set to a value smaller than the previous duty by a predetermined amount. As a result, the welding power supplied in the next PWM modulation cycle is reduced.
[0045]
  When the rate of change from the welding power exceeds the lower limit value of the standard range, a supply power increase process is performed in step S16. In this supply power increase process, the duty of the PWM signal 13a in the next PWM modulation period is set to a value larger by a predetermined amount than the previous duty. Thereby, the welding power supplied in the next PWM modulation period is increased.
[0046]
  In step S17, it is checked whether or not the energization end time te has been reached, and the processes in and after step S9 are repeated until the energization end time te is reached. When the energization end time te is reached, a normal end process is performed in which the supply of welding power is stopped while gradually reducing the welding power in step S18, and a series of welding controls are ended.
[0047]
  FIG. 10 is a block diagram of a control device for another resistance welding machine according to the present invention. 10 is different from that shown in FIG. 1 in the configuration of the control unit 60. The control unit 60 shown in FIG. 10 includes welding power integration means 61 that calculates and outputs a welding power integrated value 61a for each PWM modulation period based on the signal 8a related to the interelectrode voltage and the signal 9a related to the welding current. The inter-electrode voltage change that outputs the instantaneous change rate 62a of the inter-electrode voltage by calculating the instantaneous change rate of the inter-electrode voltage in a cycle sufficiently shorter than the PWM modulation cycle of, for example, about 1/100 of the PWM modulation cycle The rate calculation means 62, the welding power control means 63, and the inverter drive circuit 14 are provided.
[0048]
  When the welding power control means 63 recognizes that the nugget growth period has been entered by monitoring the change in the welding power integrated value 61a for each PWM modulation period, the welding power control means 63 monitors the instantaneous change rate 62a of the interelectrode voltage, If the instantaneous voltage change rate 62a exceeds a preset allowable increase rate, the output of the PWM signal 13a is immediately stopped to stop the supply of welding power, and from the next PWM modulation cycle to several cycles. By setting the duty of the PWM signal 13a to a very small value, the welding power supply amount can be greatly increased until a predetermined time elapses after the instantaneous change rate 62a of the interelectrode voltage exceeds the preset allowable increase rate. To reduce.
[0049]
  FIG. 11 is a waveform diagram showing changes in the interelectrode voltage when scattering occurs. As shown in FIG. 11, the inter-electrode voltage increases rapidly just before scattering occurs. The rapid increase in the inter-electrode voltage is regarded as a sign of the occurrence of scattering, and the supply of welding power is immediately stopped when the inter-electrode voltage suddenly increases, thereby preventing the occurrence of scattering.
[0050]
【The invention's effect】
  As described above, the resistance welding machine control device according to claim 1 monitors the time change rate of the welding power during the nugget growth period, and the time change rate of the welding power is preset.Below the allowable increase rateTherefore, the welding power can be reduced before the welding power becomes excessive during the nugget growth period and the scattering occurs, and the occurrence of the scattering can be prevented in advance. Further, it is possible to prevent the welding power from becoming too low during the nugget growth period and reducing the welding quality.
[0051]
  The resistance welding machine control device according to claim 2 is the nugget growth period.Welding electrode voltageMonitor the rate of time change ofWelding electrode voltageThe time change rate ofAcceptableWhen the rate of increase is exceeded, it is determined as a sign of occurrence of scattering and the welding power is reduced, so that occurrence of scattering can be prevented in advance.
[0052]
  Control of resistance welding machine according to claim 3MethodIn the nugget growth periodWelding powerMonitor the rate of time change ofWelding powerThe time change rate ofAllowable increase rateSince the welding power is reduced by determining that it is a sign of the occurrence of scattering when exceeding the value, it is possible to prevent the occurrence of scattering.
[0053]
  The control method of the resistance welder according to claim 4 is the nugget growth period.Welding electrode voltageMonitor the rate of time change ofWelding electrode voltageWhen the rate of change in time exceeds a preset allowable increase rate, it is judged as a sign of the occurrence of scattering and the welding power is reduced, so that the occurrence of scattering can be prevented in advance..
[Brief description of the drawings]
FIG. 1 is a block diagram of a resistance welding machine control apparatus according to the present invention.
FIG. 2 is a graph showing the change characteristics of the voltage between electrodes during welding, the rate of change of welding power, and the change characteristics of power consumption.
FIG. 3 is an explanatory diagram showing an operation of detecting welding power signs by detecting signs of occurrence of scattering.
FIG. 4 is a welding power waveform diagram showing an example of a power waveform at the time of welding when the supply of welding power is controlled by an AC resistance welding machine.
FIG. 5 is a welding power waveform diagram in which the time axis of the welding power waveform shown in FIG. 4 is enlarged.
6 is a welding power waveform diagram in which the time axis of the welding power waveform shown in FIG. 4 is enlarged.
FIG. 7 is a power waveform diagram showing power waveforms before and after the occurrence of scattering.
FIG. 8 is a power waveform diagram showing power waveforms before and after the occurrence of scattering.
FIG. 9 is a flowchart showing the operation of the resistance welding machine control device shown in FIG. 1;
FIG. 10 is a block configuration diagram of another resistance welding machine control device according to the present invention.
FIG. 11 is a waveform diagram showing changes in the interelectrode voltage when scattering occurs.
[Explanation of symbols]
  1,50 resistance welding machine control device
  4 Inverter section
  5 Step-down transformer
  6 Rectifier
  7a, 7b Welding electrode
  8 Voltage detector
  9 Current detector
  10, 60 control unit
  11 Welding power change rate calculation means
  12 Standard range storage means
  13, 63 Welding power control means
  14 Inverter drive circuit
  30 Workpiece
  31 Nugget (dissolving part)
  61 Welding power integration means
  62 Electrode voltage change rate calculation means

Claims (4)

Based on the current detection unit for detecting the welding current, the voltage detection unit for detecting the voltage between the welding electrodes, the welding current and the voltage between the welding electrodes, and calculating the rate of change over time of the welding power. Welding power change rate calculating means, and when the time change rate of the welding power exceeds a preset allowable increase rate of the welding power during the nugget growth period, it is judged as a sign of occurrence of scattering and the welding power is reduced. A welding power control means , and a resistance welding machine control device comprising:
The welding power control means immediately stops the supply of the welding power when the time change rate of the welding power exceeds the allowable increase rate, and then supplies the welding power supply amount over a predetermined period. A resistance welding machine control device characterized in that it is reduced . A voltage detector for detecting the voltage between the welding electrodes, an interelectrode voltage change rate calculating means for calculating the time change rate of the welding electrode voltage, and the time change rate of the welding electrode voltage during the nugget growth period are preset. In a control apparatus for a resistance welding machine, comprising a welding power control means for reducing welding power by judging that it is a sign of occurrence of scattering when the allowable increase rate of the voltage between the welding electrodes is exceeded ,
The welding power control means immediately stops the supply of the welding power when the time change rate of the voltage between the welding electrodes exceeds the allowable increase rate, and sets the subsequent supply amount of the welding power to a predetermined period. A resistance welding machine control device, characterized in that it is reduced over time . The welding current and the voltage between the welding electrodes are detected, the welding power is calculated based on the detected welding current and the voltage between the welding electrodes, the time change rate of the welding power is calculated, and the welding power of the welding power is calculated during the nugget growth period. In the control method of a resistance welding machine, when the rate of time change exceeds a preset allowable increase rate of the welding power, it is judged as a sign of occurrence of scattering and the welding power is reduced.
If the time rate of change of the welding power exceeds said allowable rate of increase, as well as immediately stopping the supply of the welding power, reduces over the supply amount of subsequent said weld power to a predetermined period, and characterized in that To control resistance welding machine. The voltage between the welding electrodes is detected, the time rate of change of the detected voltage between the welding electrodes is calculated, and the time rate of change of the voltage between the welding electrodes in the nugget growth period is set to the allowable increase rate of the voltage between the welding electrodes. In the resistance welding machine control method that reduces welding power by judging that it is a sign of the occurrence of scattering when it exceeds,
If the time rate of change of front Symbol welding electrode voltage exceeds the allowable rate of increase, as well as immediately stopping the supply of the welding power, reduces over the supply amount of subsequent said weld power to a predetermined time period, it A control method for a resistance welding machine.

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