Spot weld method and spot weld apparatus

Abstract

To provide a spot weld method and a spot weld apparatus which can improve bond strength of laminated four pieces of panels.SOLUTION: A spot weld method performing spot weld of a welded object 60 where a first panel 61, a second panel 62, a third panel 63, and a fourth panel 64 are laminated in order comprises the steps of: forming a first weld zone 71 by performing indirect spot weld of the first panel 61 and the second panel 62; forming a second weld zone 72 by performing indirect spot weld of the third panel 63 and the fourth panel 64; and forming a third weld zone 73 by performing direct spot welding of the welded object 60 after forming the first weld zone 71 and the second weld zone 72 to bond the second panel 62 and the third panel 63.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a spot welding method and a spot welding apparatus for welding a plurality of panels together by passing a current between electrodes. [Background technology]

[0002] 2. Description of the Related Art A known method for welding metal panels is resistance welding, in which a large current is passed between a plurality of stacked panels, and the panels are welded together by the heat generated.

[0003] In spot welding, a type of resistance welding, direct spot welding is often used, in which multiple stacked panels are clamped and pressed between a pair of electrodes arranged opposite each other, and current is passed between the electrodes. When multiple panels cannot be clamped between a pair of electrodes due to factors such as the shape of the panels, indirect pot welding is used, in which pressure is applied to the stacked portion of the panels with a welding electrode, and a ground electrode is placed in contact with a location other than the stacked portion to pass current between the electrodes.

[0004] When spot welding four stacked panels, direct spot welding can result in welding defects between panels where the pair of electrodes are not in contact. To avoid welding defects, a technology has been developed that combines direct spot welding and indirect spot welding to join four panels.

[0005] For example, in the spot welding method described in Patent Document 1, direct spot welding is first performed on a structure consisting of three stacked panels to form a first weld in the structure. Then, one panel is stacked on the structure, and indirect spot welding is performed between the fourth panel and the structure to form a second weld. The second weld is formed in a position that does not overlap with the first weld in the stacking direction to ensure a sufficient current flow when energized. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-23945 Summary of the Invention [Problem to be solved by the invention]

[0007] In the spot welding method described above, the first welding point where three panels are welded and the second welding point where the fourth panel is welded are formed at positions offset in the panel plane, making it difficult to increase the joint strength by welding multiple points in a small area.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a spot welding method and a spot welding apparatus that can improve joint strength. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, one embodiment of the present invention is a method for spot welding workpieces stacked in the order of a first panel, a second panel, a third panel, and a fourth panel, the method comprising: a first indirect welding step of indirectly spot welding the first panel and the second panel together to form a first welded portion joining the first panel and the second panel; a second indirect welding step of indirectly spot welding the third panel and the fourth panel to form a second welded portion joining the third panel and the fourth panel; and a direct welding step of, after forming the first welded portion and the second welded portion, directly spot welding the workpieces to form a third welded portion joining the second panel and the third panel.

[0010] Moreover, one embodiment of the present invention is a spot welding device used in the spot welding method, comprising: a first electrode in pressure contact with the outer surface of the first panel; a second electrode positioned off-axis from the central axis of the first electrode and in pressure contact with the surface of the second panel; a third electrode positioned coaxially opposite the second electrode and in pressure contact with the third panel; a fourth electrode positioned coaxially opposite the first electrode and in pressure contact with the outer surface of the fourth panel; a first circuit capable of switching between a conductive state and a non-conductive state between the first electrode and the second electrode; a second circuit capable of switching between a conductive state and a non-conductive state between the third electrode and the fourth electrode; and a third circuit capable of switching between a conductive state and a non-conductive state between the first electrode and the fourth electrode. [Effects of the Invention]

[0011] According to the spot welding method and spot welding device of the present invention, the joining strength of the panel can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram schematically illustrating a main part of a spot welding device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a circuit configuration of a spot welding device. [Figure 3] FIG. 2 is a diagram showing a circuit configuration of a spot welding device. [Figure 4] FIG. 2 is a diagram showing a circuit configuration of a spot welding device. [Figure 5] FIG. 2 is a diagram showing a circuit configuration of a spot welding device. [Figure 6] FIG. 2 is a cross-sectional view showing four panels joined together by the spot welding method of the present embodiment. [Figure 7] FIG. 1 is a cross-sectional view showing four panels joined together by a conventional spot welding method. [Figure 8] FIG. 1 is a diagram showing the circuit configuration of a spot welding device, and is a diagram for explaining a method for spot welding five panels. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 is a diagram schematically illustrating the main components of a spot welding apparatus 10 according to one embodiment of the present invention. The spot welding apparatus 10 is used, for example, in the manufacturing process of a vehicle such as an automobile (for example, joining panels that constitute a vehicle body). The spot welding apparatus 10 is capable of welding a plurality of metal panels that are at least partially overlapped, and is particularly suitable for joining four stacked panels 61, 62, 63, and 64.

[0014] 2 is a diagram showing the circuit configuration of spot welding device 10, and shows four panels 61, 62, 63, and 64 that are workpieces 60, and four electrodes 51, 52, 53, and 54 of spot welding device 10 that are brought into pressure contact with workpieces 60. In this embodiment, a laminated panel in which, from top to bottom, a first panel 61, a second panel 62, a third panel 63, and a fourth panel 64 are stacked is shown as an example of workpieces 60 to be spot-welded.

[0015] As shown in FIGS. 1 and 2 , workpiece 60 has a joining region 60a where four panels 61, 62, 63, and 64 are stacked, and a non-joining region 60b where two panels 62 and 63 are stacked between the four panels 61, 62, 63, and 64. Four electrodes 51, 52, 53, and 54 of spot welding device 10 are brought into pressure contact with first to fourth panels 61, 62, 63, and 64, respectively. In this embodiment, the electrode in contact with first panel 61 is referred to as first electrode 51, the electrode in contact with second panel 62 is referred to as second electrode 52, the electrode in contact with third panel 63 is referred to as third electrode 53, and the electrode in contact with fourth panel 64 is referred to as fourth electrode 54. First electrode 51 and fourth electrode 54, and second electrode 52 and third electrode 53 are arranged coaxially opposite each other.

[0016] 2, in this embodiment, an insulating material 68 is disposed in a portion of the non-bonding region 60b of the workpieces 60 between the second panel 62 and the third panel 63, which is sandwiched between a pair of electrodes 52, 53 (described later). The insulating material 68 may be made of, for example, a rubber material or weld bond, and may be formed to be thin.

[0017] Next, the components of spot welding apparatus 10 will be described. As shown in Fig. 1, spot welding apparatus 10 includes primary power source 12 and welding transformer 14, which constitute welding power source 15, switch box 16, switch control unit 18, first welding gun 30, and second welding gun 40. First welding gun 30 includes first electrode 51 and fourth electrode 54, and second welding gun 40 includes second electrode 52 and third electrode 53. Switch box 16 houses first switch 25 and second switch 26, as shown in Fig. 2. First switch 25 is connected to the positive side of welding power source 15, and second switch 26 is connected to the negative side of welding power source 15.

[0018] Welding transformer 14 converts the current from primary power supply 12 into a large current suitable for spot welding and outputs it to spot welding guns 30, 40. Welding current control device 13 is interposed between primary power supply 12 and welding transformer 14, and welding current control device 13 controls the welding current value and current flow time supplied to each of electrodes 51, 52, 53, 54.

[0019] The first welding gun 30 is attached to the tip of the first robot arm 31. The first welding gun 30 is equipped with a first electrode 51 and a fourth electrode 54 arranged coaxially opposite each other. The first electrode 51 is configured to be movable in the axial direction by a drive mechanism 32. The fourth electrode 54 is fixed to the tip of the gun arm 34 of the first welding gun 30. Alternatively, the first electrode 51 may be a fixed electrode and the fourth electrode 54 may be a movable electrode. The axial movement of the first electrode 51 and the clamping pressure applied by the first and fourth electrodes 51, 54 are controlled by a first welding gun control device 36 connected to the first welding gun 30.

[0020] Second welding gun 40 is attached to the tip of second robot arm 41. Second welding gun 40 is equipped with second electrode 52 and third electrode 53 arranged coaxially facing each other. Second electrode 52 is configured to be movable in the axial direction by drive mechanism 42. Third electrode 53 is fixed to the tip of gun arm 44 of second welding gun 40. Alternatively, second electrode 52 may be a fixed electrode and third electrode 53 may be a movable electrode. The axial movement of second electrode 52 and the clamping pressure applied by second and third electrodes 52, 53 are controlled by second welding gun control device 46 connected to second welding gun 40.

[0021] 1 and 2, during spot welding, with workpiece 60 set in place, first electrode 51 and second electrode 52 are respectively brought close to fourth electrode 54 and third electrode 53 by drive mechanisms 32 and 42. As a result, a joining region 60a of workpiece 60 is clamped and pressed between the pair of electrodes 51 and 54 of first welding gun 30, and a non-joining region 60b of workpiece 60 is clamped and pressed between the pair of electrodes 52 and 53 of second welding gun 40.

[0022] Next, the circuit configuration of the above-mentioned spot welding apparatus 10 will be described. As shown in Figures 1 and 2, the first electrode 51 is connected to the welding power source 15 via a first electric line 21 and a first switch 25. The second electrode 52 is connected to the welding power source 15 via a second electric line 22 and a second switch 26. The third electrode 53 is connected to the welding power source 15 via a third electric line 23 and a first switch 25. The fourth electrode 54 is connected to the welding power source 15 via a fourth electric line 24 and a second switch 26.

[0023] First switch 25 is operated to connect welding power source 15 to first electrode 51 or third electrode 53. Second switch 26 is operated to connect welding power source 15 to second electrode 52 or fourth electrode 54. First switch 25 and second switch 26 are each switched by switch control unit 18 shown in FIG. 1.

[0024] In the spot welding apparatus 10 having the circuit configuration described above, as shown in Fig. 3, a first circuit 28A electrically connecting the first electrode 51 and the second electrode 52 is formed by connecting the first switch 25 to the first electrical line 21 and the second switch 26 to the second electrical line 22. As shown in Fig. 4, a second circuit 28B electrically connecting the third electrode 53 and the fourth electrode 54 is formed by connecting the first switch 25 to the third electrical line 23 and the second switch 26 to the fourth electrical line 24. As shown in Fig. 5, a third circuit 28A electrically connecting the first electrode 51 and the fourth electrode 54 is formed by connecting the first switch 25 to the first electrical line 21 and the second switch 26 to the fourth electrical line 24. In the spot welding device 10, the switch control unit 18 switches the switches 25, 26, thereby switching each of the first circuit 28A, the second circuit 28B, and the third circuit 28C between a conductive state and a non-conductive state.

[0025] Next, a spot welding method using the above-described spot welding apparatus 10 will be described. As shown in Fig. 2, when welding, the first electrode 51 of the spot welding apparatus 10 is brought into pressure contact with the outer surface of a first panel 61 in a joining region 60a of the workpiece 60, and the fourth electrode 54 is brought into pressure contact with the outer surface of a fourth panel 64. The second electrode 52 of the spot welding apparatus 10 is brought into pressure contact with the outer surface of a second panel 62 in a non-joining region 60b of the workpiece 60 so as to be offset from the central axis of the first electrode 51, and the third electrode 53 is brought into pressure contact with the outer surface of a third panel 63.

[0026] In this state, spot welding apparatus 10 uses switch control unit 18 to switch the current-carrying circuit to first circuit 28A shown in FIG. 3. At this time, second circuit 28B and third circuit 28C are de-energized. In this state, spot welding apparatus 10 applies current between first electrode 51 and second electrode 52 to perform indirect spot welding. As a result, as shown in FIG. 3, a first welded portion 71 is formed on the axis of first electrode 51, joining first panel 61 and second panel 62 (first indirect welding step).

[0027] Next, spot welding apparatus 10 uses switch control unit 18 to switch the current-carrying circuit to second circuit 28B shown in FIG. 4. At this time, first circuit 28A and third circuit 28C are de-energized. In this state, spot welding apparatus 10 applies current between third electrode 53 and fourth electrode 54 to perform indirect spot welding. As a result, as shown in FIG. 4, a second weld 71 is formed on the axis of fourth electrode 54, joining third panel 63 and fourth panel 64 (second indirect welding process).

[0028] Next, the spot welding apparatus 10 switches the current-carrying circuit to the third circuit 28C shown in FIG. 5 using the switch control unit 18. At this time, the first circuit 28A and the second circuit 28B are de-energized. In this state, the spot welding apparatus 10 applies current between the first electrode 51 and the fourth electrode 54 to perform direct spot welding. As a result, as shown in FIG. 5, a third welded portion 71 is formed on the axis of the first electrode 51, joining the second panel 62 and the third panel 63 (direct welding process). As a result, the first welded portion 71, the second welded portion 72, and the third welded portion 73 are formed on the axes of the first and fourth electrodes 51 and 52 so as to overlap in the stacking direction of the workpieces 60.

[0029] In each welding process, the pressure applied to the workpiece 60 by the first electrode 51 and the fourth electrode 54 and the pressure applied by the second electrode 52 and the third electrode 53 can be set appropriately. As an example, in the spot welding device 10 of this embodiment, the pressure applied by the first electrode 51 and the fourth electrode 54 is set to be higher in the direct welding process than in the first and second indirect welding processes. The pressure applied by the second electrode 52 and the third electrode 53 is set to an equal value in each welding process and is set to a lower value than the pressure applied by the first electrode 51 and the fourth electrode 54 in the direct welding process. Note that in each welding process, the pressure applied by the first electrode 51 and the fourth electrode 54 and the pressure applied by the second electrode 52 and the third electrode 53 may be set to an equal value.

[0030] In the spot welding method using the spot welding apparatus 10 described above, in the first and second indirect welding steps and the direct step, the electrodes 51, 52, 53, 54 are positioned at the same position relative to the workpiece 60, and the workpiece 60 can be maintained in a clamped and pressurized state. In this embodiment, an insulating material 68 is inserted between the second and third panels 62, 63 at the clamping position between the second and third electrodes 52, 53, so that current can be prevented from flowing between the second and third panels 62, 63 in the first and second indirect welding steps.

[0031] Furthermore, when spot welding is performed at multiple locations in the joining area 60a of the workpiece 60, the spot welding device 10 can perform welding efficiently by changing only the clamping positions of the first and fourth electrodes 51, 54, without changing the clamping positions of the second and third electrodes 52, 53.

[0032] In the spot welding method described above, as shown in FIG. 5, each welded portion 71, 72, 73 is formed overlapping in the stacking direction of the workpiece 60, so that welding can be performed at multiple locations in a small area of ​​the workpiece 60, thereby increasing the joining strength of the workpiece 60.

[0033] Fig. 6 is a cross-sectional view showing four panels 61, 62, 63, and 64 joined together using the spot welding method of this embodiment, and Fig. 7 is a cross-sectional view showing four panels 61, 62, 63, and 64 joined together using a conventional spot welding method. In Figs. 6 and 7, A, B, C, D, E, F, and G respectively indicate the order in which the welds are formed.

[0034] 7 , three panels (second panel 62, third panel 63, and fourth panel) are direct spot welded together to form a first welded portion 171 where the second panel 62 and the third panel 63 are joined, and a second welded portion 172 where the third panel 63 and the fourth panel 64 are joined. Then, one panel (first panel 61) is stacked, and the first panel 61 and the second panel 62 are indirect spot welded to form a third welded portion 173 where the first panel 61 and the second panel 62 are joined. With the conventional method, in order to ensure the amount of current flow, the welded portions 171 and 172 formed by direct spot welding and the welded portion 173 formed by indirect spot welding are misaligned in the plane direction of the welded part 60.

[0035] In contrast, in the spot welding method of this embodiment, as shown in Fig. 6, first welded portion 71, second welded portion 72, and third welded portion 73 are formed overlapping each other without being misaligned in the planar direction, so that more welded portions can be formed in the same area than in the past, thereby improving the joint strength of workpiece 60.

[0036] The above-described spot welding apparatus 10 can also join five stacked panels. Fig. 8 is a diagram showing the circuit configuration of the spot welding apparatus 10 and an embodiment of a method for spot welding five panels 61, 62, 63, 64, and 65.

[0037] 8 , the workpiece 60 is a laminated panel formed by stacking, from top to bottom, a first panel 61, a second panel 62, a fifth panel 65, a third panel 63, and a fourth panel 64. The workpiece 60 has a laminated region 60a in which five panels 61, 62, 65, 63, and 64 are stacked, and a non-bonded region 60b in which three panels 62, 65, and 63 are stacked between the first and fourth panels 61 and 64. In this embodiment, insulating material 68 is disposed in the non-bonded region 60b of the workpiece 60 between the second panel 62, the fifth panel 65, and the third panel 63, respectively, at portions that are sandwiched between the second and third electrodes 52 and 53.

[0038] When welding five panels 61, 62, 63, 64, and 65, first, current is passed between the first and second electrodes 51 and 52 to indirectly spot weld the first panel 61 and the second panel 62 together (first indirect welding process). This forms a first welded portion 71, joining the first and second panels 61 and 62, on the axis of the first electrode 51. Next, current is passed between the third and fourth electrodes 53 and 54 to indirectly spot weld the third panel 63 and the fourth panel 64 together (second indirect welding process). This forms a second welded portion 72, joining the third and fourth panels 63 and 64, on the axis of the fourth electrode 54. Next, current is passed between the first and fourth electrodes 51 and 54 to perform direct spot welding (direct welding process). As a result, a third welded portion 74 where the second, fifth, and third panels 61, 65, and 62 are joined is formed on the axis of the first electrode 51. As a result, the welded portions 71, 72, and 74 can be formed so as to overlap in the stacking direction of the workpieces 60.

[0039] The present invention is not limited to the above-described embodiment and modifications, and various modifications are possible without departing from the spirit of the invention.

[0040] For example, the spot welding method may involve indirect spot welding the third panel 63 and the fourth panel 64 to form the second weld 72, and then indirect spot welding the first panel 61 and the second panel 62 to form the first weld 71.

[0041] Additionally, the insulating material 68 is optional, and spot welding can be performed without using the insulating material 68. [Explanation of symbols]

[0042] 10 Spot welding equipment 12 Primary power supply 13 Welding current control device 14 Welding transformer 15 Welding power source 16 Switch Box 18 Switch control section 25 First Switch 26 Second Switch 30 First welding gun 40 Second welding gun 51 First electrode 52 Second electrode 53 Third Electrode 54 Fourth Electrode 60 Workpiece 61 First Panel 62 Second Panel 63 Third Panel 64 Fourth Panel 65 Fifth Panel 68 Insulation

Claims

1. A method for spot welding a workpiece including a first panel, a second panel, a third panel, and a fourth panel stacked in this order, the method comprising: a first indirect welding step of indirect spot welding the first panel and the second panel to form a first welded portion at which the first panel and the second panel are joined; a second indirect welding step of indirectly spot welding the third panel and the fourth panel to form a second welded portion at which the third panel and the fourth panel are joined; a direct welding step of, after forming the first welded portion and the second welded portion, direct spot welding the workpieces to form a third welded portion at which the second panel and the third panel are joined.

2. The spot welding method according to claim 1 , wherein the first welded portion, the second welded portion, and the third welded portion are formed so as to overlap in a stacking direction of the workpieces.

3. an electrode that comes into pressure contact with the second panel and an electrode that comes into pressure contact with the third panel in the second welding step are disposed coaxially opposite each other; 3. The spot welding method according to claim 1, wherein in the first and second indirect welding steps, an insulating material is disposed between the second panel and the third panel and on the axis of each of the electrodes.

4. the workpiece has a fifth panel laminated between the second panel and the third panel; The spot welding method according to any one of claims 1 to 3, wherein in the direct welding step, the second panel, the fifth panel, and the third panel are joined by the direct spot welding.

5. A spot welding device used in the spot welding method according to any one of claims 1 to 3, a first electrode in pressure contact with the outer surface of the first panel; a second electrode disposed at a position offset from the central axis of the first electrode and brought into pressure contact with a surface of the second panel; a third electrode disposed coaxially opposite the second electrode and brought into pressure contact with the third panel; a fourth electrode disposed coaxially opposite the first electrode and in pressure contact with the outer surface of the fourth panel; a first circuit capable of switching between a conducting state and a non-conducting state between the first electrode and the second electrode; a second circuit capable of switching between a conducting state and a non-conducting state between the third electrode and the fourth electrode; a third circuit capable of switching between a conducting state and a non-conducting state between the first electrode and the fourth electrode; A spot welding device comprising:

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