welding equipment

Abstract

To achieve appropriate welding in shorter time than conventional welding.SOLUTION: A welding device includes: electrodes 80a and 80b which are opposite to each other so as to sandwich a joined product and pressurize the joined product; a welding power source 20; detection parts 10-14, 150 and 151 for detecting a physical amount relating to the joined product while welding; and a control part 15 for performing welding by first energization of supplying current to the electrodes 80a and 80b from the welding power source 20, stopping the first energization when the physical amount detected while welding satisfies a termination condition, and performing welding by second energization of supplying current to the electrodes 80a and 80b from the welding power source 20 again. The physical amount is a welding current flowing through the electrodes 80a and 80b, a welding voltage applied between the electrodes 80a and 80b, welding power supplied to the electrodes 80a and 80b, a current square time product that is a product of a square of welding current and lapsed time from start of the first energization, a temperature of the welded product, and a displacement magnitude in a thickness direction of the joined product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a welding device, and more particularly to a welding device suitable for joining a laminate of a plurality of iron-based metal foils. [Background technology]

[0002] In recent years, stacked lithium-ion batteries have come into use, in which multiple flat positive and negative electrodes are stacked with separators between them. Figure 11(A) is a perspective view showing the stacked lithium-ion battery after stacking, and Figure 11(B) is a perspective view showing the state after the electrode tabs and lead terminals are connected.

[0003] In a stacked lithium-ion battery, as shown in Fig. 11(A), positive electrodes 100 made of metal foil and negative electrodes 101 made of metal foil are alternately stacked with separators (not shown) interposed between them. Each positive electrode 100 is provided with a tab 102 for lead connection, and these tabs 102 are stacked as shown in Fig. 11(B) and joined to a lead terminal 104 for external connection at a joint 106. Similarly, each negative electrode 101 is provided with a tab 103 for lead connection, and these tabs 103 are stacked and joined to a lead terminal 105 for external connection at a joint 107.

[0004] In conventional lithium ion batteries, ultrasonic bonding has often been used to bond aluminum foil or copper foil, which is generally used as a current collector (positive electrode 100, negative electrode 101). Meanwhile, in the development of next-generation batteries, there is a movement to use stainless steel as a current collector due to its excellent corrosion resistance and mechanical properties. However, ultrasonic welding is not suitable for stainless steel and other ferrous metals due to wear on the ultrasonic horn and anvil (receiving jig) and adhesion of the workpiece, so resistance welding is more appropriate.

[0005] As shown in FIG. 12, resistance welding is a method in which a plurality of tabs 102 (or tabs 103) and lead terminals 104 (or lead terminals 105) are sandwiched and pressed between a pair of electrodes 108a, 108b from above and below, while a current is passed between the electrodes 108a, 108b, and the Joule heat generated raises the temperature of the tabs 102 (or tabs 103) and lead terminals 104 (or lead terminals 105), thereby joining them.

[0006] Although resistance welding of iron-based metals is easy, the resistance value increases when a large number of iron-based metal foils are stacked. Therefore, when using the general current welding method (a method of joining in one shot for a specified time), spatter and dust are generated, and the metal foil adheres to the electrode, making it impossible to obtain a stable joint.

[0007] Therefore, in the technology disclosed in Patent Document 1, a preliminary step is performed in which a pressure is applied to at least a portion of the overlapping portion of the metal foil to bring them into close contact with each other, thereby leveling at least a portion of the overlapping portion and forming a portion with a uniform electrical resistance, followed by the main resistance welding step. However, the technology disclosed in Patent Document 1 has a problem in that the need for the preliminary step makes welding time longer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-66017 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a welding device that can achieve appropriate welding in a shorter time than conventional devices, even when welding a laminate of multiple iron-based metal foils. [Means for solving the problem]

[0010] a control unit configured to: perform welding by a first current supply from the welding power source to the first and second electrodes in response to an external instruction, and to stop the first current supply when one or more of the physical quantities detected during welding satisfy a predetermined end condition; and perform welding by a second current supply from the welding power source to the first and second electrodes again, wherein the physical quantities are the welding current flowing between the first and second electrodes, the welding voltage applied between the first and second electrodes, the welding power supplied between the first and second electrodes, the welding current supplied between the first and second electrodes, the current squared time product which is the product of the square of the welding current and the elapsed time from the start of the first current supply; the temperature of the workpiece; and the displacement of the workpiece in the thickness direction.

[0011] In one configuration example of the welding device of the present invention, the control unit is characterized in that, as welding by the first current supply, it performs constant voltage control welding in which a predetermined welding voltage is supplied between the first and second electrodes, or constant power control welding in which a predetermined welding power is supplied between the first and second electrodes, or intermittent constant voltage control welding in which a predetermined welding voltage is supplied intermittently between the first and second electrodes, or intermittent constant power control welding in which a predetermined welding power is supplied intermittently between the first and second electrodes. In addition, in one configuration example of the welding device of the present invention, the control unit is characterized in that, as the welding by the second current supply, it performs constant current control welding in which a predetermined welding current is supplied between the first and second electrodes, or intermittent constant current control welding in which a predetermined welding current is supplied intermittently between the first and second electrodes. In addition, in one configuration example of the welding device of the present invention, the control unit performs constant current control welding in which a predetermined welding current is supplied between the first and second electrodes as the welding by the second current flow, and reduces the welding current at a predetermined gradient when one or more of the physical quantities detected during this welding satisfy a predetermined cooling start condition. In one configuration example of the welding device of the present invention, the control unit performs constant current control welding in which a predetermined welding current is supplied between the first and second electrodes as the second current welding, and when one or more of the physical quantities detected during this welding satisfy a predetermined cooling start condition, calculates a slope at which to decrease the welding current so that the time from the start of the first current flow to the expected end of the second current flow approaches a predetermined target time, and decreases the welding current at the calculated slope. In one configuration example of the welding device of the present invention, the article to be welded is made of a laminate in which a plurality of metal foils are stacked. [Effects of the Invention]

[0012] According to the present invention, it is possible to prevent the generation of spatter and dust, and to prevent the adhesion of the object to be welded to the electrode, and to realize stable welding even when welding a laminate of multiple iron-based metal foils. Furthermore, since the present invention does not require the conventional preliminary process, it is possible to shorten the time required for welding. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing the configuration of a welding device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a welding head according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of changes in welding current, welding voltage, welding power, and inter-electrode resistance during welding. [Figure 4] FIG. 4 is a flowchart showing the operation of the welding device according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of a reference waveform of a welding voltage during the first current application in the first embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of a reference waveform of a welding current during second energization in the first embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of a reference waveform of welding power during the first current application in the first embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of a reference waveform of a welding current during second energization in the second embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart showing the operation of the welding device according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a block diagram showing an example of the configuration of a computer that realizes the welding apparatus according to the first and second embodiments of the present invention. [Figure 11] FIG. 11 is a perspective view showing the state after stacking of the stacked lithium ion battery and the state in which the electrode tabs and lead terminals are connected. [Figure 12] FIG. 12 is an enlarged cross-sectional view of a joint in resistance welding. DETAILED DESCRIPTION OF THE INVENTION

[0014] [First Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a welding device according to a first embodiment of the present invention. The welding device of this embodiment has a start switch 2, a rectifier circuit 3, a capacitor 4, an inverter 5, a welding transformer 6, a diode 7, a welding head 8, a Hall element 9, a current detector 10, a voltage detector 11, a temperature detector 12, a load detector 13, a displacement detector 14, a control unit 15, an operation unit 16, a memory unit 17, and a display unit 18 for displaying, for example, the waveform of a physical quantity detected during welding.

[0015] Start switch 2, rectifier circuit 3, capacitor 4, inverter 5, welding transformer 6, and diode 7 constitute a welding power source 20 that supplies current to welding head 8. Furthermore, Hall element 9, current detection unit 10, voltage detection unit 11, temperature detection unit 12, load detection unit 13, displacement detection unit 14, power detection unit 150, and current squared time product detection unit 151, which will be described later, constitute a detection unit that detects physical quantities related to the workpieces during welding.

[0016] 2 is an enlarged cross-sectional view of the welding head 8. The welding head 8 is equipped with electrodes 80a and 80b that face each other with the workpiece 85 sandwiched therebetween and that apply pressure to the workpiece 85. The electrodes 80a and 80b are each composed of an electrode body 81a and 81b made of a copper alloy such as chromium copper (Cu-Cr) or alumina-dispersed copper (Cu-Al2O3), and tip portions 82a and 82b made of the above copper alloy or an alloy containing at least one element selected from the group consisting of molybdenum (Mo), tungsten (W), iron (Fe), nickel (Ni), and titanium (Ti). The welding head 8 further includes thermocouples 83a and 83b attached to the tip portions 82a and 82b, and pressure mechanisms 84a and 84b that move the electrodes 80a and 80b up and down to sandwich and pressurize the workpiece 85.

[0017] The pressure mechanisms 84a and 84b are provided with load cells (not shown) so that the magnitude of the load applied to the article to be bonded 85 can be converted into an electric signal. Also, the pressure mechanisms 84a and 84b are provided with displacement sensors (not shown) so that the amount of displacement in the thickness direction of the article to be bonded 85 can be converted into an electric signal. Incidentally, the temperatures of the tip ends 82a and 82b can be detected based on the voltages from the thermocouples 83a and 83b, but a radiation thermometer may be provided instead of the thermocouples 83a and 83b.

[0018] The operation of the welding device will be described below. In this embodiment, a laminate in which a plurality of tabs 102 and lead terminals 104 are stacked is described as the object to be joined 85. Tabs 102 are made of, for example, iron-based metal foil. First, the pressure mechanisms 84a and 84b of the welding head 8 sandwich and pressurize the workpiece 85 from above and below (in the direction along the stacking direction of the laminate) using the electrodes 80a and 80b as shown in Fig. 2. In the example of Fig. 2, the pressure mechanisms 84a and 84b apply pressure to the electrodes 80a and 80b, respectively, but it goes without saying that they may also apply pressure to only one of the electrodes 80a and 80b.

[0019] For example, when a user operates operation unit 16 to give an instruction to start welding, a start signal is output from operation unit 16 and start switch 2 is turned on. When start switch 2 is turned on, rectifier circuit 3 full-wave rectifies the AC output of 200V AC commercial three-phase AC power supply 1 and charges capacitor 4 connected in parallel between the output terminals of rectifier circuit 3. Rectifier circuit 3 is composed of a three-phase full-wave mixed bridge using six diodes 30.

[0020] Inverter 5 converts the charging voltage of capacitor 4 into AC voltage and supplies it to the primary side of welding transformer 6. Inverter 5 is configured as a bridge consisting of four NPN transistors 50. The secondary output of welding transformer 6 is full-wave rectified by rectifier (diode) 7 and led to electrodes 80a, 80b. This causes a large current to flow between electrodes 80a, 80b, and the generated Joule heat raises the temperature of the joining surfaces (joining surfaces between metal foils) of objects to be joined 85, thereby joining them.

[0021] Current detection unit 10 detects current I flowing through the secondary side of welding transformer 6 (i.e., welding current flowing through electrodes 80a, 80b) from the output of Hall element 9 provided on the secondary side of welding transformer 6. Voltage detection unit 11 detects welding voltage V applied between electrodes 80a, 80b.

[0022] The temperature detecting section 12 detects the temperature T of the article 85 (the temperature of the tip portions 82a, 82b) based on the voltages from the thermocouples 83a, 83b. As described above, a radiation thermometer may be used instead of the thermocouples 83a, 83b to detect the temperature T of the article 85. The load detecting section 13 detects the load G applied to the article 85 based on the output of a load cell provided in the pressure mechanisms 84a, 84b. The displacement detecting section 14 detects the amount of displacement D in the thickness direction of the article 85 based on the output of a displacement sensor provided in the pressure mechanisms 84a, 84b.

[0023] A power detection unit 150 provided in the control unit 15 detects the welding power W supplied to the electrodes 80a, 80b by integrating the value of the welding current I detected by the current detection unit 10 and the value of the welding voltage V detected by the voltage detection unit 11. A current squared time product detection unit 151 provided in the control unit 15 detects the current squared time product I, which is the product of the square of the welding current I and the elapsed time t from the start of current flow. 2 Calculate t.

[0024] FIG. 3 is a diagram showing an example of changes in welding current I, welding voltage V, welding power W, and inter-electrode resistance R during welding, and FIG. 4 is a flowchart showing the operation of the welding device of this embodiment. In this embodiment, the electrodes 80a and 80b are energized twice, first and second energizations, with the first energization being performed using a constant voltage control method and the second energization being performed using a constant current control method.

[0025] Desired reference waveforms for energizing electrodes 80a, 80b are stored as desired welding conditions for each of the first and second energizations in memory unit 17. In this embodiment, a reference waveform for welding voltage V is set as the welding condition for the first energization, and a reference waveform for welding current I is set as the welding condition for the second energization. Memory unit 17 also stores an end condition for the first energization and a cooling start condition for the second energization.

[0026] First, control unit 15 operates inverter 5 to generate an AC voltage, thereby applying a current to electrodes 80a, 80b. Then, control unit 15 monitors in real time welding voltage V detected by voltage detection unit 11, and controls the on / off of transistor 50 of inverter 5 to control the amount of current flow to electrodes 80a, 80b so that welding voltage V at the current time, t, which is the elapsed time from the start of first current flow, matches the value of welding voltage V at elapsed time t on the reference waveform stored in memory unit 17.

[0027] 5 is a diagram showing an example of a reference waveform of welding voltage V during first current application. In the reference waveform of welding voltage V in this embodiment, for example, a set voltage Vsp, a rise time t1 up to set voltage Vsp, and a waveform up to set voltage Vsp are defined. By controlling the amount of current applied to electrodes 80a, 80b in this manner so that the waveform of welding voltage V coincides with the reference waveform, constant voltage control welding is performed in which a constant welding voltage V is supplied between electrodes 80a, 80b by first current application as shown in FIG. 3 (step S1 in FIG. 4).

[0028] Next, the control unit 15 determines whether the termination conditions for the first energization are satisfied (Step S2 in FIG. 4). The termination conditions for the first energization include a termination condition value for the welding current I, a termination condition value for the welding power W, and a current squared time product I 2 These include an end condition value of t, an end condition value (temperature range) and duration of the temperature T of the object 85 to be bonded, and an end condition value of the displacement D in the thickness direction of the object 85 to be bonded.

[0029] Control unit 15 determines that the termination condition for the first energization is met when welding current I detected by current detection unit 10 reaches or exceeds the termination condition value (current) for the first energization stored in memory unit 17. Control unit 15 may also determine that the termination condition for the first energization is met when welding power W calculated by power detection unit 150 reaches or exceeds the termination condition value (power) for the first energization stored in memory unit 17.

[0030] The control unit 15 also detects the current squared time product I 2The control unit 15 may determine that the termination condition for the first current flow is met when t reaches or exceeds the termination condition value (product of current squared times) for the first current flow stored in the storage unit 17. Moreover, the control unit 15 may determine that the termination condition for the first current flow is met when the temperature T of the object 85 detected by the temperature detection unit 12 reaches or exceeds the termination condition value (temperature) for the first current flow stored in the storage unit 17. Moreover, the control unit 15 may determine that the termination condition for the first current flow is met when the displacement D in the thickness direction of the object 85 detected by the displacement detection unit 14 reaches or exceeds the termination condition value (displacement) for the first current flow stored in the storage unit 17.

[0031] When it is determined that the termination condition for the first energization is satisfied, the control unit 15 stops the operation of the inverter 5 and terminates the first energization to the electrodes 80a, 80b (step S3 in Fig. 4). In the example in Fig. 3, when the welding current I increases to the termination condition value (current) for the first energization, it is determined that the termination condition for the first energization is satisfied, and the first energization is terminated.

[0032] In the above example, the first current supply is terminated when one termination condition is met, but the first current supply may be terminated when multiple termination conditions are met, rather than just one.

[0033] Next, control unit 15 operates inverter 5 again to generate an AC voltage, thereby applying a current to electrodes 80a, 80b. Control unit 15 then monitors in real time the welding current I detected by current detection unit 10, and controls the on / off of transistor 50 of inverter 5 to control the amount of current flow to electrodes 80a, 80b so that the welding current I at the current time t, which is the elapsed time from the start of the second current flow, matches the value of the welding current I at the elapsed time t on the reference waveform stored in memory unit 17.

[0034] 6 is a diagram showing an example of the reference waveform of welding current I during second energization. In the reference waveform of welding current I in this embodiment, for example, a set current Isp, a rise time t2 to the set current Isp, a waveform up to the set current Isp, a time t3 from the start of cooling to the end of energization, and a waveform from the start of cooling to the end of energization are defined. In this way, by controlling the amount of energization to electrodes 80a, 80b so that the waveform of welding current I matches the reference waveform, constant current control welding is performed in which a constant welding current I is supplied to electrodes 80a, 80b by second energization, as shown in FIG. 3 (step S4 in FIG. 4).

[0035] Next, control unit 15 determines whether a cooling start condition is met (step S5 in FIG. 4). The cooling start condition is the value of welding voltage V. Control unit 15 determines that the cooling start condition is met when welding voltage V detected by voltage detection unit 11 becomes equal to or less than the cooling start condition value (voltage) stored in memory unit 17.

[0036] When it is determined that the cooling start condition is met, the control unit 15 controls the amount of current supplied to the electrodes 80a, 80b so that the welding current I detected by the current detection unit 10 coincides with the reference waveform from the cooling start point shown in Fig. 6, thereby decreasing the welding current I (step S6 in Fig. 4). In this embodiment, good welding quality can be achieved by gradually decreasing the welding current I to gradually cool the workpiece 85. When the amount of current supplied to the electrodes 80a, 80b becomes 0, the second current supply is terminated (step S7 in Fig. 4).

[0037] As described above, in this embodiment, when resistance welding of the workpieces 85 is performed, the physical quantity detected during welding is monitored in real time, and when the physical quantity reaches a predetermined termination condition value, the first current to the electrodes 80a, 80b is terminated and the second current is started, and the current required for joining is passed through, thereby completing the joining of the workpieces 85.

[0038] In this embodiment, the first current is used to perform constant voltage control welding, which breaks down the oxide film present on the metal foil surface and secures a current path. If the second current is applied without securing a current path using the first current, a high voltage will be applied instantaneously to pass the set current value, causing spattering, adhesion of the metal foil to the electrodes 80a and 80b, and wear at the tips of the electrodes 80a and 80b, making it difficult to achieve a stable joint.

[0039] Furthermore, in order to break the surface oxide film of the workpiece 85 during the first current application, the set voltage Vsp must be relatively high. At this time, if the reaction speed during control switching is slow, a large current may flow instantaneously. Therefore, by measuring and controlling the physical quantities during the first current application, fast control switching to the second current application is achieved. The time from the start of the first current application to the establishment of the termination condition is not necessarily the same every time, even if the number of metal foil layers and welding conditions are the same, depending on the surface condition and distortion of the metal foil, etc. Therefore, if control switching is performed at a predetermined time without measuring the physical quantities during the first current application, sometimes the current path cannot be secured during the first current application, and sometimes a large current exceeding the required value may flow.

[0040] According to this embodiment, it is possible to prevent the generation of spatters and dust, and also to prevent the metal foil from adhering to the electrodes 80a and 80b, thereby realizing stable bonding of the iron-based metal foil laminate.

[0041] In this embodiment, the preliminary process disclosed in Patent Document 1 is not required. Although the preliminary process takes time, the total time for the first and second currents in this embodiment is, for example, about 100 ms. Therefore, according to this embodiment, the time required for welding can be shortened.

[0042] In this embodiment, welding is performed using a constant voltage control method during the first current application, but welding using a constant power control method may also be performed. In this case, a reference waveform of the welding power W for the first current application is stored in advance in memory unit 17. Figure 7 is a diagram showing an example of the reference waveform of the welding power W during the first current application. In the reference waveform of the welding power W in this embodiment, for example, a set power Wsp, a rise time t1 up to the set power Wsp, and a waveform up to the set power Wsp are defined.

[0043] Control unit 15 simply controls the amount of current supplied to electrodes 80a, 80b so that welding power W at the current time t, which is the elapsed time from the start of first current supply, matches the value of welding power W at elapsed time t on the reference waveform stored in memory unit 17. When welding is performed using the constant power control method, it goes without saying that the termination condition value of welding power W is not used as the termination condition value of first current supply.

[0044] The control unit 15 may be configured to determine that the cooling start condition is met when the welding power W calculated by the power detection unit 150 becomes equal to or less than the cooling start condition value (power) stored in the storage unit 17. The control unit 15 may be configured to determine that the cooling start condition is met when the temperature T of the workpiece 85 detected by the temperature detection unit 12 reaches equal to or greater than the cooling start condition value (temperature) stored in the storage unit 17, or when a state in which the temperature T is within the range of the cooling start condition value (temperature) stored in the storage unit 17 continues for equal to or greater than the duration stored in the storage unit 17. The control unit 15 may be configured to determine that the cooling start condition is met when the displacement amount D in the thickness direction of the workpiece 85 detected by the displacement detection unit 14 reaches equal to or greater than the cooling start condition value (displacement amount) stored in the storage unit 17. In the above example, cooling is started when one cooling start condition is met, but cooling may be started when multiple cooling start conditions are met, rather than when one cooling start condition is met.

[0045] [Second Example] In the first embodiment, the welding current I is gradually decreased when the cooling start condition is met during the second current application, but the time when the first current application end condition is met varies depending on, for example, the surface condition or distortion of the metal foil, which may result in a large variation in the time required for welding (the time from the start of the first current application to the end of the second current application). Therefore, instead of decreasing the welding current I at a predetermined gradient as shown in Figure 6, the gradient of the welding current I from the start of cooling may be adjusted so that the time required for welding approaches a predetermined target time.

[0046] In this embodiment, the configurations of the welding equipment and the workpieces are the same as those in the first embodiment, so the explanation will be given using the reference numerals in FIGS. Fig. 8 is a diagram showing an example of the reference waveform of the welding current I during the second energization in this embodiment. The difference from Fig. 6 is that the waveform from the start of cooling to the end of energization is not defined.

[0047] 9 is a flowchart showing the operation of the welding device of this embodiment. The processes in steps S1 to S5 are the same as those in the first embodiment.

[0048] When it is determined that the cooling start condition is met (YES in step S5 of FIG. 9), the control unit 15 calculates the slope at which the welding current I is decreased from the set current Isp to 0 based on the set current Isp, the time required from the start of the first current flow to the start of cooling of the second current flow, and a predetermined target time so that the time from the start of the first current flow to the expected end of the second current flow approaches the target time (step S8 of FIG. 9).

[0049] Then, the control unit 15 controls the amount of current supplied to the electrodes 80a, 80b so that the welding current I detected by the current detection unit 10 decreases at the slope calculated in step S8 (step S9 in FIG. 9). When the amount of current supplied to the electrodes 80a, 80b becomes 0, the second current supply is terminated (step S10 in FIG. 9). In this way, in this embodiment, the time from the start of the first current supply to the end of the second current supply can be made closer to the target time.

[0050] In addition, if the time required from the start of the first current flow to the start of cooling of the second current flow has already exceeded the target time, and even if the welding current I is lowered vertically, the time from the start of the first current flow to the expected end of the second current flow will exceed the target time, then the slope can be set to a predetermined value (for example, a slope close to vertical descent).

[0051] In the first and second examples, the article 85 is a laminate of a plurality of iron-based metal foils, but the present invention is not limited to this. The article 85 may be a laminate of a plurality of plates made of nickel, or a laminate of a plurality of plates made of a nickel alloy, or a laminate of a plurality of plates made of aluminum, or a laminate of a plurality of plates made of an aluminum alloy, or a laminate of a plurality of plates made of copper or a copper alloy, or a laminate obtained by laminating a plurality of plates made of nickel or a nickel alloy, plates made of aluminum or an aluminum alloy, and plates made of copper or a copper alloy.

[0052] In the first and second embodiments, welding during the first energization is performed using a constant voltage control method or a constant power control method, but pulse control welding may also be used. That is, welding may be performed using an intermittent constant voltage control method in which a predetermined welding voltage is intermittently supplied between electrodes 80a, 80b, or welding may be performed using an intermittent constant power control method in which a predetermined welding power is intermittently supplied between electrodes 80a, 80b. Similarly, in the first and second embodiments, welding during the second energization is performed using a constant current control method, but intermittent constant current control welding may also be used.

[0053] The functions of the control unit 15, operation unit 16, storage unit 17, and display unit 18 in the first and second embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage unit, and an interface with the outside, and a program that controls these hardware resources. An example of the configuration of this computer is shown in Figure 10.

[0054] The computer includes a CPU 200, a storage device 201, and an interface device (hereinafter abbreviated as I / F) 202. A welding power source, current detection unit 10, voltage detection unit 11, temperature detection unit 12, load detection unit 13, displacement detection unit 14, etc. are connected to I / F 202. In such a computer, a program for implementing the method of the present invention is stored in storage device 201. CPU 200 executes the processes described in the first and second embodiments in accordance with the program stored in storage device 201. [Industrial Applicability]

[0055] The present invention can be applied to a resistance welding device. [Explanation of symbols]

[0056] 1...3-phase AC power supply, 2...start switch, 3...rectifier circuit, 4...capacitor, 5...inverter, 6...welding transformer, 7...diode, 8...welding head, 9...hall element, 10...current detection unit, 11...voltage detection unit, 12...temperature detection unit, 13...load detection unit, 14...displacement detection unit, 15...control unit, 16...operation unit, 17...memory unit, 18...display unit, 20...welding power source, 80a, 80b...electrodes, 81a, 81b...electrode body, 82a, 82b...tips, 83a, 83b...thermocouple, 84a, 84b...pressure mechanism, 85...workpiece, 150...power detection unit, 151...current squared time product detection unit

Claims

1. first and second electrodes that face each other with an object to be bonded sandwiched therebetween and are configured to apply pressure to the object to be bonded; a welding power source that supplies current between the first and second electrodes; a detection unit configured to detect one or more physical quantities related to the workpieces during welding; a control unit configured to perform welding by a first current supply, in which current is supplied from the welding power source to between the first and second electrodes in response to an external instruction, and to stop the first current supply when one or more of the physical quantities detected during the welding satisfy a predetermined end condition, and to perform welding by a second current supply, in which current is again supplied from the welding power source to between the first and second electrodes; the physical quantities are a welding current flowing between the first and second electrodes, a welding voltage applied between the first and second electrodes, a welding power supplied between the first and second electrodes, a current-squared-time product which is the product of the square of the welding current and the elapsed time from the start of the first current flow, a temperature of the workpiece, and a displacement amount in the thickness direction of the workpiece.

2. 2. The welding device according to claim 1, The control unit performs, as the welding by the first current application, constant voltage control welding in which a predetermined welding voltage is supplied between the first and second electrodes, constant power control welding in which a predetermined welding power is supplied between the first and second electrodes, intermittent constant voltage control welding in which a predetermined welding voltage is supplied intermittently between the first and second electrodes, or intermittent constant power control welding in which a predetermined welding power is supplied intermittently between the first and second electrodes.

3. 3. The welding device according to claim 1, The control unit performs, as the welding by the second current application, constant current control welding in which a predetermined welding current is supplied between the first and second electrodes, or intermittent constant current control welding in which a predetermined welding current is supplied intermittently between the first and second electrodes.

4. The welding device according to any one of claims 1 to 3, the control unit performs constant current control welding in which a predetermined welding current is supplied between the first and second electrodes as the second current welding, and decreases the welding current at a predetermined gradient when one or more of the physical quantities detected during the welding satisfy a predetermined cooling start condition.

5. The welding device according to any one of claims 1 to 3, the control unit performs constant current control welding in which a predetermined welding current is supplied between the first and second electrodes as the second current welding, and when one or more of the physical quantities detected during the welding satisfy a predetermined cooling start condition, calculates a slope at which the welding current is decreased so that the time from the start of the first current flow to the predicted end of the second current flow approaches a predetermined target time, and decreases the welding current at the calculated slope.

6. The welding device according to any one of claims 1 to 5, The welding device is characterized in that the object to be welded is a laminate in which a plurality of metal foils are stacked.

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