Welding device

Abstract

A welding device (1) to be used to weld a workpiece (W) comprises a rotation mechanism (4), a first electrode (1E), a second electrode (2E), and a support member (5). The rotation mechanism (4) rotates a first member (41) and a second member (42) at the same speed and in mutually opposite directions which are orthogonal to a prescribed direction by means of rotational power inputted to a rotary shaft (4R) extending along the prescribed direction. The first electrode (1E) extends in the prescribed direction along the rotary shaft (4R) of the rotation mechanism (4), is fixed to the first member (41), and can freely come into contact with a front surface (W1) of the workpiece (W). The second electrode (2E) extends in the prescribed direction indicated above, is fixed to the second member (42), and can freely come into contact with the front surface (W1) of the workpiece (W). The support member (5) can freely come into contact with a rear surface (W2) of the workpiece (W) at at least one location on a perpendicular bisector (P) of a line segment (S) connecting the first electrode (1E) and the second electrode (2E) in a prescribed-direction view, which is the viewpoint from the prescribed direction.

Description

welding equipment

[0001] The present invention relates to a welding device for welding workpieces.

[0002] Resistance welding is a known welding technique in which an electric current is passed through a workpiece with electrodes in contact therewith, and the workpiece is melted by resistance heating to weld the melted portion. A technique has been proposed for a device that performs this resistance welding, which includes two electrodes that apply pressure to the workpiece from one side and one electrode that applies pressure to the workpiece from the other side.

[0003] For example, Patent Document 1 discloses an apparatus that includes a first electrode and a second electrode that clamp a workpiece and weld a flange joint, and a third electrode that is disposed on the same side of the workpiece as the first electrode but in a different position from the first electrode. If one side of the workpiece is called the front side and the opposite side of the workpiece is called the back side, the apparatus of Patent Document 1 can be said to be an apparatus in which the first electrode and the third electrode are abutted against the front side of the workpiece and the second electrode is abutted against the back side of the workpiece.

[0004] Patent No. 7346982

[0005] In a device such as that disclosed in Patent Document 1, the workpiece is supported in a sandwiched state between two electrodes provided on the front side at the point where one electrode abuts against the workpiece and is provided between the electrodes provided on the back side. On the other hand, in this device, the workpiece is not supported from the back side at the point where the other electrode abuts against the front side. In this cantilevered state, where one of the two electrodes provided on the front side is supported from the back side but the other is not supported from the back side, even if the pressing force of one electrode on the workpiece can be secured, the pressing force of the other electrode on the workpiece cannot be secured, which may result in a decrease in welding quality. Therefore, there is room for improvement in ensuring welding quality.

[0006] The welding device of the present invention was invented in consideration of these problems, and one of its objectives is to ensure welding quality. However, in addition to this objective, another objective of the present invention is to achieve operational effects derived from the respective configurations shown in the "Mode for Carrying Out the Invention" below, which are not obtainable with conventional techniques.

[0007] The disclosed welding device can be realized as the following disclosed aspects (application examples) and solves at least part of the above-mentioned problems. Each of the aspects from aspect 2 onwards is an aspect that can be selected as an additional option, and each of the aspects from aspect 2 onwards is an aspect that can be omitted. None of the aspects from aspect 2 onwards discloses an aspect or configuration that is essential to the present invention.

[0008] Aspect 1. The disclosed welding device is used for welding workpieces and includes a rotation mechanism, a first electrode, a second electrode, and a support member. The rotation mechanism rotates a first member and a second member in opposite directions perpendicular to the predetermined direction at the same speed by rotational power input to a rotation shaft extending along the predetermined direction. The first electrode extends in the predetermined direction, is fixed to the first member, and is capable of abutting against the surface of the workpiece. The second electrode extends in the predetermined direction, is fixed to the second member, and is capable of abutting against the surface. The support member is capable of abutting against the back surface of the workpiece at at least one point on the perpendicular bisector of a line segment connecting the first electrode and the second electrode when viewed from the predetermined direction.

[0009] Aspect 2. In the above-mentioned Aspect 1, it is preferable that the welding device includes a device main body that detachably holds the support member. Aspect 3. In the above-mentioned Aspect 1 or 2, it is preferable that the welding device includes a first actuator that urges the first electrode against the surface, a second actuator that urges the second electrode against the surface, and a control unit that controls the first actuator and the second actuator.

[0010] Aspect 4. In the above-described aspect 3, it is preferable that the control unit controls the first actuator and the second actuator according to a preset profile so that a difference between a first pressure force, which is a magnitude of the force that urges the first electrode against the surface, and a second pressure force, which is a magnitude of the force that urges the second electrode against the surface, falls within a predetermined range.

[0011] Aspect 5. In any one of Aspects 1 to 4 above, it is preferable that the first electrode and the second electrode are welding electrodes, and the support member has a ground electrode that can freely abut against the back surface on the perpendicular bisector.

[0012] Aspect 6. In any one of Aspects 1 to 4 above, it is preferable that one of the first electrode and the second electrode is a welding electrode and the other is a ground electrode. Aspect 7. In any one of Aspects 1 to 6 above, it is preferable that the support member is a rod-shaped member bent toward the back surface side.

[0013] According to the disclosed welding device, welding quality can be ensured.

[0014] 5 is an elevation view showing a robot arm to which a welding device according to an embodiment is applied, together with the welding device; FIG. 6 is a perspective view schematically showing a welding device according to an embodiment; FIG. 7 is a plan view schematically showing a state in which electrodes of a welding device according to an embodiment are closest to each other; FIG. 8 is a plan view schematically showing a state in which electrodes of a welding device according to an embodiment are furthest apart from each other; FIG. 9 is a perspective view schematically showing a rotation mechanism provided in a welding device according to an embodiment; FIG. 10 is a partially exploded perspective view of FIG. 11; FIG. 11 is a perspective view schematically showing a reducer alone used in a rotation mechanism provided in a welding device according to an embodiment; FIG. 12 is a schematic view showing a first rotation mechanism of a welding device according to a modified example; FIG. 13 is a schematic view showing a second rotation mechanism of a welding device according to a modified example; and FIG. 14 is a schematic view showing a third rotation mechanism of a welding device according to a modified example.

[0015] An embodiment of a welding device will be described with reference to the drawings. The welding device of this embodiment is a device that resistance-welds metal materials such as steel and aluminum using a pair of welding guns. Examples of workpieces (welding targets) that are welded by the welding device include metal members used in vehicles such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). A plug-in hybrid vehicle is a hybrid vehicle that can externally charge or receive power from a battery. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable that supplies power from an external charging facility and a power outlet (outlet) for external power supply.

[0016] In the following embodiments, a Cartesian coordinate system having three mutually orthogonal coordinate axes, X, Y, and Z, is used as a reference for directions used in the description of the welding device. In this Cartesian coordinate system, the direction along the X axis is referred to as the "X direction" (a predetermined direction, a direction along the rotation axis of the rotation mechanism), the direction along the Y axis is referred to as the "Y direction," and the direction along the Z axis is referred to as the "Z direction."

[0017] The X direction has two inherent directions: the direction from negative to positive on the X axis and the direction from positive to negative on the X axis, which are opposite to each other. Therefore, one of the X directions will be referred to as the "X1 direction" and the other as the "X2 direction." Similarly, one of the Y directions will be referred to as the "Y1 direction" and the other as the "Y2 direction." One of the Z directions will be referred to as the "Z1 direction" and the other as the "Z2 direction."

[0018] The welding device exemplified in the following embodiment is formed symmetrically in the Y direction. However, the welding device does not have to be completely Y-symmetrical, and may be asymmetrical in the Y direction. Note that the expressions relating to directions such as "along," "along," and "extending along" used in this embodiment are not limited to directions parallel to a reference direction, but may also be slightly inclined relative to the reference direction.

[0019] [I. One Embodiment] [1. Configuration] Fig. 1 is an elevation view showing a robot arm to which a welding device according to one embodiment is applied. Fig. 2 is a perspective view schematically showing the welding device according to one embodiment. Fig. 3 is a plan view schematically showing a state in which electrodes of the welding device according to one embodiment are closest to each other. Fig. 4 is a plan view schematically showing a state in which electrodes of the welding device according to one embodiment are farthest from each other.

[0020] [1-1. Application Example of Welding Device] As shown in Fig. 1 , a welding device 1 according to this embodiment is attached to the tip 9a of a robot arm 9. The robot arm 9 is an industrial robot that changes the positions and postures of various devices attached to the tip 9a. The robot arm 9 illustrated in Fig. 1 is a vertical articulated robot that includes a plurality of arms 91, joints 92 for each arm 91, and actuators (not shown) built into the joints 92. The actuators built into the joints 92 are controlled by a controller (not shown), thereby controlling the welding device 1 attached to the tip 9a of the robot arm 9 to a position and posture suitable for welding.

[0021] 2, welding device 1 is provided with first welding gun 21 and second welding gun 22, a control unit 3, and a rotation mechanism 4 that changes the relative positions of the two welding guns 21, 22. The welding device 1 described here is provided with a support member 5 that supports a workpiece W (shown by a two-dot chain line in FIG. 2), and a device main body 6 to which various devices including support member 5 are attached.

[0022] Welding Guns 21 and 22 each have an electrode 1E, 2E (referred to as "E" when not otherwise distinguished) provided at the end (tip) in the X1 direction, an actuator 1A, 2A (referred to as "A" when not otherwise distinguished) provided at the end (base) in the X2 direction, and a main body 1B, 2B (referred to as "B" when not otherwise distinguished) provided between the electrode E and the actuator A in the X direction. The welding guns also have welding centers 1C, 2C (referred to as "C" when not otherwise distinguished) extending in the X direction. The electrodes E of the welding guns 21 and 22 are positioned so as to overlap with the respective welding centers C when viewed from the X direction (as viewed in the axial direction of a rotation shaft 4R, as described later, or as viewed from a predetermined direction). Preferably, the centers of the electrodes E of the welding guns 21 and 22 and the respective welding centers C are positioned on the same line.

[0023] Various known welding guns can be used for the welding guns 21 and 22. For example, any of an X-type welding gun, a C-type welding gun, and an indirect welding gun can be used for the first welding gun 21. Furthermore, any of an X-type welding gun, a C-type welding gun, and an indirect welding gun can be used for the second welding gun 22. The electrode E extends in the X direction and is provided so as to be able to abut against a surface W1 of the workpiece W facing the X2 direction (hereinafter referred to as the "front surface").

[0024] Actuator A is a drive source that biases electrode E in the X1 direction. That is, actuator A biases electrode E toward surface W1 of workpiece W. This actuator A is provided with a motor main body that generates a biasing force that presses electrode E toward surface W1 of workpiece W, and an encoder for adjusting the amount of rotation (driving degree, rotation angle, rotation speed) of the motor main body. Main body B incorporates a mechanism (not shown) that transmits the biasing force of the motor main body of actuator A to electrode E. The main body B illustrated in FIG. 2 is provided in a cylindrical shape with a cylindrical axis along the X direction.

[0025] Hereinafter, for each element such as the electrode E and actuator A provided on the first welding gun 21, the element name will be prefixed with "first" and the reference number will be prefixed with "1." Furthermore, for each element provided on the second welding gun 22, the element name will be prefixed with "second" and the reference number will be prefixed with "2." For example, the electrode E provided on the first welding gun 21 will be referred to as the "first electrode 1E," and the actuator A provided on the second welding gun 22 will be referred to as the "second actuator 2A."

[0026] ==Control Unit== The control unit 3 is a controller (electronic control device, control board, controller, etc.) that controls the actuators 1A, 2A that urge the electrodes 1E, 2E against the surface W1 of the workpiece W. Here, the magnitude of the force urging the first electrode 1E against the surface W1 of the workpiece W is referred to as the "first pressure force," and the magnitude of the force urging the second electrode 2E against the surface W1 of the workpiece W is referred to as the "second pressure force." The control unit 3 exemplified in this embodiment controls the first actuator 1A and the second actuator 2A in accordance with a preset profile so that the difference between the first pressure force and the second pressure force falls within a predetermined range. The "predetermined range" here includes a range in which the difference between the first pressure force and the second pressure force is not excessively large, an appropriate range determined by the properties of the workpiece W, etc.

[0027] ==Rotation Mechanism== The rotation mechanism 4 is a mechanism that rotates a first member 41 and a second member 42 (described later) in opposite directions and at the same speed. This rotation mechanism 4 has a rotation shaft 4R (indicated by a dashed line in FIG. 2 ) to which rotational power is input from a drive unit 4S, and a reducer 40 that decelerates and outputs the rotation of the rotation shaft 4R. The drive unit 4S and the reducer 40 are arranged coaxially with an axis 4C of the rotation shaft 4R in the welding device 1. This axis 4C extends along the X direction. Therefore, in other words, the rotation shaft 4R extends along the X direction (a predetermined direction), and the axial direction of the rotation shaft 4R can also be said to be the X direction.

[0028] The drive unit 4S is not disposed on the outer periphery of the rotating shaft 4R, but is disposed in the extension direction of the axis 4C. Similar to the actuators 1A and 2A, the drive unit 4S is provided with a motor main body that generates rotational power and an encoder for adjusting the rotation amount (drive degree, rotation angle, rotation speed) of the motor main body. The reducer 40 is provided with a first member 41 and a second member 42 that output rotational power. The first member 41 and the second member 42 are annular members that rotate around the axis 4C. Note that any mechanism can be used for the reducer 40 as long as it rotates the first member 41 and the second member 42 in opposite directions and at the same speed.

[0029] The first member 41 and the second member 42 rotate around an axis 4C along the X direction, and therefore can be said to be members that rotate in a direction perpendicular to the X direction. Furthermore, when the rotation direction of the first member 41 and the second member 42 is used as a reference, the rotation axis 4R of the rotation mechanism 4 can be said to extend in a direction perpendicular to the rotation direction of the first member 41 and the second member 42.

[0030] When the drive unit 4S rotates the rotating shaft 4R in a first direction (e.g., counterclockwise when viewed from the X2 direction toward the X1 direction), the first member 41 rotates in the direction opposite to the first direction, and the second member 42 rotates in the first direction. Conversely, when the drive unit 4S rotates the rotating shaft 4R in a second direction (e.g., clockwise when viewed from the X2 direction toward the X1 direction), the first member 41 rotates in the direction opposite to the second direction (i.e., the above-mentioned first direction), and the second member 42 rotates in the second direction.

[0031] A first welding gun 21 is attached to the first member 41. Specifically, a first body portion 1B of the first welding gun 21 is fixed to the outer peripheral surface 4a of the first member 41. As a result, a first electrode 1E is fixed to the first member 41 via the first body portion 1B, and the position of the first electrode 1E is adjusted to a position corresponding to the rotational phase of the first member 41. A second welding gun 22 is attached to the second member 42. Specifically, a second body portion 2B of the second welding gun 22 is fixed to the outer peripheral surface 4b of the second member 42. As a result, a second electrode 2E is fixed to the second member 42 via the second body portion 2B, and the position of the second electrode 2E is adjusted to a position corresponding to the rotational phase of the second member 42.

[0032] When moving the welding guns 21, 22 away from each other, the drive unit 4S rotationally drives the rotating shaft 4R in a first direction, rotates the outer peripheral surface 4a of the first member 41 in a second direction, and rotates the outer peripheral surface 4b of the second member 42 in the first direction. When moving the welding guns 21, 22 closer to each other, the drive unit 4S rotationally drives the rotating shaft 4R in a second direction, rotates the outer peripheral surface 4a of the first member 41 in the first direction, and rotates the outer peripheral surface 4b of the second member 42 in the second direction. In this way, the relative positions of the welding guns 21, 22 are changed by the rotation mechanism 4, which rotates the first member 41 and the second member 42 in opposite directions but at the same speed.

[0033] The relative arrangement of the first electrode 1E and the second electrode 2E will be described below with reference to Figures 3 and 4. In the following description, the phase in which the outer peripheral surface 4a of the first member 41 has rotated the most in the first direction is referred to as the "first minimum phase," and the phase in which the outer peripheral surface 4b of the second member 42 has rotated the most in the second direction is referred to as the "second minimum phase." Furthermore, the phase in which the outer peripheral surface 4a of the first member 41 has rotated the most in the second direction is referred to as the "first maximum phase," and the phase in which the outer peripheral surface 4b of the second member 42 has rotated the most in the first direction is referred to as the "second maximum phase."

[0034] 3, when the rotation shaft 4R is rotated in the second direction, the outer peripheral surface 4a of the first member 41 has a first minimum phase, and the outer peripheral surface 4b of the second member 42 has a second minimum phase. The state in which the outer peripheral surfaces 4a, 4b have the minimum phase is the state in which the welding guns 21, 22 are closest to each other (hereinafter referred to as the "minimum pitch state"). In the minimum pitch state, as viewed in the X direction, a first midpoint M1 of a line segment S connecting the first welding center 1C and the second welding center 2C is located on the Z1 direction side of the shaft center 4C.

[0035] 4, when the rotation shaft 4R is rotated in the first direction, the outer peripheral surface 4a of the first member 41 assumes a first maximum phase, and the outer peripheral surface 4b of the second member 42 assumes a second maximum phase. The state in which the outer peripheral surfaces 4a, 4b assume the maximum phase is the state in which the welding guns 21, 22 are furthest apart (hereinafter referred to as the "maximum pitch state"). In the maximum pitch state, the second midpoint M2 of the line segment S coincides with the axis 4C as viewed in the X direction.

[0036] 3 and 4 , when viewed in the X direction, the line segment S extends along the Y direction, and the perpendicular bisector P of the line segment S extends along the Z direction. If the dimension by which the first electrode 1E is spaced from the perpendicular bisector P in the Y1 direction (one side) is defined as a first dimension L1, and the dimension by which the second electrode 2E is spaced from the perpendicular bisector P in the Y2 direction (the other side) is defined as a second dimension L2, then regardless of whether the dimensions L1 and L2 are long or short, the first dimension L1 and the second dimension L2 are maintained equal to each other (L1 = L2, or "equal pitch," so to speak).

[0037] Here, the illustrated perpendicular bisector P intersects with the axis 4C of the rotation shaft 4R. In particular, in the maximum pitch state illustrated in FIG. 4 , the axis 4C of the rotation shaft 4R extends in the Z direction through the intersection of the line segment S and the perpendicular bisector P. If we compare it to an analog clock with an hour hand centered on the axis 4C of the rotation shaft 4R and pointing in the Z1 direction indicating 12 o'clock, the first electrode 1E of the first minimum phase would be positioned at the 1 o'clock position, and the second electrode 2E of the second minimum phase would be positioned at the 11 o'clock position. Also, if we compare it to a similar analog clock, the first electrode 1E of the first maximum phase would be positioned at the 3 o'clock position, and the second electrode 2E of the second maximum phase would be positioned at the 9 o'clock position. If we compare it to the analog clock described above, the relative positions of the electrodes 1E and 2E will be changed as the first electrode 1E moves from either the 3 o'clock position or the 1 o'clock position to the other and the second electrode 2E moves from either the 9 o'clock position or the 11 o'clock position to the other.

[0038] A specific example of the rotation mechanism 4 will be described below with reference to FIGS. 5 to 7 . FIG. 5 is a perspective view schematically illustrating the rotation mechanism 4 provided in a welding device 1 according to an embodiment. FIG. 6 is a perspective view showing a portion of FIG. 5 exploded. FIG. 7 is a perspective view schematically illustrating each of the reducers 70 and 80 used in the rotation mechanism 4 provided in the welding device 1 according to an embodiment. As shown in FIGS. 5 and 6 , the rotation mechanism 4 illustrated here includes only one drive unit 4S (see FIG. 2 ) that rotationally drives the rotating shaft 4R, whereas two reducers 40, a first reducer 70 and a second reducer 80, are provided. The rotational power of the rotating shaft 4R is input to each of the reducers 70 and 80.

[0039] First, the configuration common to the reducers 70, 80 will be described with reference to Figure 7. The reducers 70, 80 are reducers in which the rotating shafts 41R, 42R (4R), cases 71, 81, and output flanges 72, 82 are arranged coaxially with one another. If the rotating shafts 41R, 42R are considered to be first elements, the cases 71, 81 are considered to be second elements, and the output flanges 72, 82 are considered to be third elements, the reducers 70, 80 can be said to be three-element, two-degree-of-freedom reducers. Here, a three-element, two-degree-of-freedom reducer means a reducer in which the rotational speed of the remaining element is uniquely determined when the rotational speeds of two of the three elements are determined.

[0040] The illustrated reducers 70 and 80 are high-precision control reducers that employ a planocentric reduction mechanism. A specific example of the reducers 70 and 80 is a so-called precision reducer RV. However, each reducer 70 and 80 may be a three-element, two-degree-of-freedom reducer consisting of at least three coaxially arranged elements, and a well-known planetary gear mechanism or harmonic reducer may be applied.

[0041] Each reducer 70, 80 is provided with a spur gear 7s, 8s that meshes with an input gear 4i provided on the outer periphery of the rotating shaft 4R, and each case 71, 81 and each output flange 72, 82 that are freely rotatable in accordance with the rotation of each spur gear 7s, 8s.

[0042] Specifically, the first reducer 70 includes a first spur gear 7s, a first case 71 (first output portion), and a first output flange 72 (second output portion). １ The second reducer 80 is provided with a second spur gear 8s, a second case 81 (third output portion), and a second output flange 82 (fourth output portion). The second reducer 80 has a second reduction ratio i ２ is set.

[0043] The rotary shaft 4R is inserted through the first case 71 and the second case 81, and the first case 71 and the second case 81 are rotatable about the rotary shaft 4R. The first output flange 72 is rotatable relative to the first case 71. Similarly, the second output flange 82 is rotatable relative to the second case 81.

[0044] The cases 71, 81 and the output flanges 72, 82 are coaxial with the axis 4C of the rotating shaft 4R and are provided in a cylindrical (annular) shape centered on the axis 4C. That is, the rotating shaft 4R is inserted through the cases 71, 81 and the output flanges 72, 82. This rotating shaft 4R has a first rotating shaft 41R, which is a portion that is inserted through the first case 71 and the first output flange 72 of the first reducer 70, and a second rotating shaft 42R, which is a portion that is inserted through the second case 81 and the second output flange 82 of the second reducer 80. The first rotating shaft 41R and the second rotating shaft 42R are connected to each other along the axis 4C and rotate together.

[0045] Each of the cases 71, 81 and each of the output flanges 72, 82 can output rotational power without being constrained by other elements, and can also be used by being attached to another fixed (immovable) member to prevent rotation, or by being constrained to rotate integrally with another rotating element. Therefore, the cases 71, 81 and the output flanges 72, 82 can output rotational power without being constrained by other elements, and can be used by being attached to another fixed (immovable) member to prevent rotation, or by being constrained to rotate integrally with another rotating element. １ , i ２ In other words, it is an element (output section) that can reduce the speed of the rotational power of the rotating shaft 4R and output it in accordance with the speed.

[0046] One common use of the reducers 70, 80 is to output rotational power to the output flanges 72, 82 in a state where the cases 71, 81 are fixed so as not to rotate. １ is defined as the value obtained by dividing the rotation speed of the first output flange 72 by the rotation speed of the first rotary shaft 41R when the first case 71 is fixed so as not to rotate. ２ is defined as the value obtained by dividing the rotation speed of the second output flange 82 by the rotation speed of the second rotary shaft 42R when the second case 81 is fixed so as not to rotate.

[0047] The cases 71, 81 are case-shaped members that house the spur gears 7s, 8s on the shaft center 4C side (inside, so to speak). If the output flanges 72, 82 are fixed so as not to rotate, the reduction ratio i of the reducers 70, 80 can be adjusted. １ , i ２ The output flanges 72, 82 are arranged to rotate in the opposite direction to the rotation direction of the rotary shaft 4R regardless of the position of the output flanges 72, 82 in the X direction relative to the cases 71, 81. The output flanges 72, 82 can also be considered as members that protrude like a flange along the X direction. The output flanges 72, 82 that are not fixed so as to be non-rotatable are arranged to rotate in the direction opposite to the rotation direction of the rotary shaft 4R regardless of the position of the output flanges 72, 82 in the X direction relative to the cases 71, 81. １ , i ２ The direction of rotation is determined by

[0048] Next, the configuration of each of the reducers 70, 80 will be described with reference to Figures 5 and 6. In the reducer 40, the first output flange 72 and first case 71 of the first reducer 70 and the second case 81 and second output flange 82 of the second reducer 80 are arranged in this order from the X2 direction to the X1 direction. In other words, the first output flange 72 is located on the X2 direction side (one side) of the first case 71, the second case 81 is located on the X1 direction side (other side) of the first case 71, and the second output flange 82 is located on the X1 direction side (other side) of the second case 81.

[0049] 5, a connecting member 78 is provided between the first case 71 and the second case 81. The connecting member 78 is a member that connects the first case 71 and the second case 81 so that the first case 71 and the second case 81 rotate together, and is provided in a cylindrical shape that is coaxial with the axis 4C, just like the cases 71 and 81. However, the connecting member 78 may be omitted, and a reducer 40 in which the cases 71 and 81 are directly connected to each other may be used.

[0050] The first reducer 70 converts the rotational power of the rotary shaft 4R into a rotational power at a first reduction ratio i １The first reducer 70, to which the rotational power is transmitted, is decelerated by a reduction ratio i １ , i ２ Regardless of the rotation direction, the outer peripheral surface 73 of the first case 71 is rotated in the direction opposite to the rotation direction of the rotary shaft 4R.

[0051] The second reducer 80 converts the rotational power of the rotating shaft 4R into a second reduction ratio i ２ The rotational speed is reduced by the first reduction ratio i １ In the second reducer 80, the rotational power of the first case 71 reduced by the reduction ratio i １ , i ２ The direction in which the outer peripheral surface 83 of the second output flange 82 is rotated is determined by the above.

[0052] Specifically, the first reduction ratio i of the first reducer 70 １ is expressed by the following equation 1, and the second reduction ratio i ２ is expressed by the following equation 2.

[0053]

[0054] The rotational speeds a, b, and c are positive when rotating in the same direction as the rotational direction of the rotary shaft 4R, and negative when rotating in the opposite direction to the rotational direction. The rotational speed a of the rotary shaft 4R is positive only, the rotational speed b of the first case 71 is negative only, and the rotational speed c of the second output flange 82 is determined by the reduction ratio i １ , i ２ It can take a positive or negative value depending on

[0055] In the first example of the reducer 40 described here, the first reduction ratio i １ and second reduction ratio i ２The "predetermined condition" here means a condition in which the rotation speed c of the second output flange 82 is a positive value and the absolute values ​​of the rotation speed c of the second output flange 82 and the rotation speed b of the first case 71 are equal to each other. In other words, the first reduction ratio i is set so as to satisfy the predetermined condition that the rotation speed c of the second output flange 82 and the rotation speed b of the first case 71 are the same speed but rotate in opposite directions to each other. １ and second reduction ratio i ２ Specifically, the relative magnitude relationship between the first reduction ratio i １ is the second reduction ratio i ２ is set to half of the

[0056] In the above-described reducers 70 and 80, the first case 71 is an example of the first member 41 in the rotation mechanism 4, and the second output flange 82 is an example of the second member 42 in the rotation mechanism 4. In this example, the outer peripheral surface 73 of the first case 71 corresponds to the outer peripheral surface 4a of the first member 41, and the outer peripheral surface 83 of the second output flange 82 corresponds to the outer peripheral surface 4b of the second member 42.

[0057] ==Support Member== However, if the workpiece W is simply biased in the X1 direction by the two electrodes 1E, 2E, there is a risk that the workpiece W will move away in the X1 direction, making it impossible to ensure the pressure of the electrodes 1E, 2E on the workpiece W. Furthermore, even if the workpiece W is supported so as to be sandwiched only on the back side of the point where one of the two electrodes 1E, 2E abuts against the workpiece W, there is a risk that the pressure of the other of the two electrodes 1E, 2E will not be ensured.

[0058] Alternatively, if the workpiece W is supported so as to be sandwiched between the two electrodes 1E, 2E on the backside of the points where each of the electrodes 1E, 2E abuts against the workpiece W, the pressure applied by each of the electrodes 1E, 2E is ensured, but supporting members are required at two points on the backside of the workpiece W. If an attempt is made to provide members that support the workpiece W from the backside at two points corresponding to the positions of the two electrodes 1E, 2E in this way, the configuration becomes complicated, and depending on the shape and size of the workpiece W, the supporting members and the workpiece W may interfere with each other, which may restrict the shape and size of the workpiece W.

[0059] Therefore, in order to ensure a reaction force to the pressing force with a simple configuration, the welding device 1 of this embodiment is provided with a support member 5 that abuts against a surface W2 of the workpiece W facing the X1 direction (hereinafter referred to as the "back surface"). The support member 5 is provided so as to be able to abut against the back surface W2 of the workpiece W at least at one location on the perpendicular bisector P as viewed in the X direction. Fig. 2 illustrates an example in which the support member 5 is provided at only one location.

[0060] 3 and 4, the location of the support member 5 is preferably set in a region between the first midpoint M1 and the second midpoint M2 of the line segment S on the perpendicular bisector P, including the first midpoint M1 and the second midpoint M2, so that the support member 5 can easily resist the pressure of the electrodes 1E and 2E regardless of the positions of the electrodes 1E and 2E. It is more preferable that the location of the support member 5 (see FIG. 2) be midway between the first midpoint M1 and the second midpoint M2 on the perpendicular bisector P.

[0061] As shown in FIG. 2 , the support member 5 is a rod-shaped member bent toward the back surface W2 of the workpiece W. The illustrated support member 5 includes a first arm 51, a second arm 52, and a support electrode 5E. The first arm 51 is a portion extending in the X direction in a space spaced apart from the workpiece W in the Z2 direction. The second arm 52 is a portion on the X1 direction side of the workpiece W, extending from the Z2 direction end of the first arm 51 toward the Z1 direction. When the support member 5 is viewed from the Y1 direction, the first arm 51 and the second arm 52 form an L shape, and the X2 direction end of the first arm 51 is attached to the device main body 6, which will be described later. The support electrode 5E is an electrode protruding from the Z1 direction end of the second arm 52 toward the X2 direction.

[0062] The support member 5 is formed so as to embrace the workpiece W from the back side by the first arm portion 51, the second arm portion 52, and the support electrode 5E. The illustrated support electrode 5E is provided as an earth electrode. Meanwhile, the first electrode 1E and the second electrode 2E are provided as welding electrodes. In resistance welding using the welding device 1, the portion where the support electrode 5E provided as an earth electrode abuts on the workpiece W is not welded, but the portion where the electrodes 1E, 2E provided as welding electrodes abut on the workpiece W is welded.

[0063] Specifically, electrodes 1E, 2E, and 5E are brought into contact with the workpiece W and a current is passed through them, and the electrodes 1E and 2E provided as welding electrodes on the workpiece W melt due to resistance heat at the points where they are in contact with the workpiece W, thereby welding the melted points. For this reason, it is desirable to suppress the contact resistance of the support electrode 5E provided as an earth electrode and suppress heat generation at the points where the support electrode 5E is in contact.

[0064] From this perspective, in the welding apparatus 1 of this embodiment, two electrodes 1E, 2E provided as welding electrodes are brought into contact with the front surface W1 of the workpiece W with a first pressure force and a second pressure force, while one support electrode 5E provided as an earth electrode is brought into contact with the back surface W2 of the workpiece W with a pressure force that is the sum of the first pressure force and the second pressure force, thereby supporting the workpiece W in a balanced manner. This balance of pressure forces suppresses the contact resistance of the support electrode 5E provided as an earth electrode, thereby suppressing resistance heating at the contact points of the support electrode 5E. Furthermore, resistance heating at the contact points of the electrodes 1E, 2E provided as welding electrodes is ensured.

[0065] The support electrode 5E does not necessarily have to be provided on the support member 5. In place of the support electrode 5E, a support member 5 not provided with the support electrode 5E is provided with a member protruding toward the X2 direction at the Z1 direction end of the second arm portion 52. In this case, it is preferable that one of the first electrode 1E and the second electrode 2E is a welding electrode and the other is a ground electrode.

[0066] ==Device Main Body== The support member 5 is detachably held in the device main body 6. By replacing the attached support member 5 with another support member 5 of a different shape or size, it is possible to attach various support members 5 to the device main body 6. The rotation mechanism 4 is attached to this device main body 6, and various devices and components may also be attached, including a transformer that changes and outputs voltage to the drive unit 4S of the rotation mechanism 4 and the actuators 1A, 2A of the welding guns 21, 22.

[0067] Since the device main body 6 and the devices and members attached to the device main body 6 are fixed (immovable), they are set at fixed locations that non-rotatably restrain the first output flange 72. For example, the first output flange 72 is fixed to a transformer attached to the device main body 6.

[0068] [2. Actions and Effects] The welding device 1 of this embodiment is configured as described above, and therefore provides the following actions and effects. (1) According to the welding device 1 of this embodiment, the distance between the first electrode 1E fixed to the first member 41 and the second electrode 2E fixed to the second member 42 can be changed by rotating the first member 41 and the second member 42 in opposite directions and at the same speed using the rotation mechanism 4. Furthermore, while maintaining the first dimension L1, which is the distance between the first electrode 1E in the Y1 direction relative to the perpendicular bisector P, and the second dimension L2, which is the distance between the second electrode 2E in the Y2 direction relative to the perpendicular bisector P, equal, the lengths of the first dimension L1 and the second dimension L2 can be adjusted.

[0069] Furthermore, a support member 5 is provided that can freely contact the back surface W2 of the workpiece W at at least one location on the perpendicular bisector P of the line segment S connecting the first electrode 1E and the second electrode 2E when viewed in the X direction. By supporting the workpiece W from the back side by the support member 5 arranged in this manner, it is possible to ensure both a first pressing force that applies the first electrode 1E to the front surface W1 of the workpiece W and a second pressing force that presses the second electrode 2E against the front surface W1 of the workpiece W. This makes it possible to ensure the welding quality of the workpiece W.

[0070] (2) Because the support member 5 is detachably held by the device body 6, it is possible to replace the support member 5 with one of a shape and size that abuts against the back surface W2 of the workpiece W at an appropriate position depending on the distance between the first electrode 1E and the second electrode 2E. This also contributes to improving welding quality. (3) The first actuator 1A, which urges the first electrode 1E toward the front surface W1 of the workpiece W, is controlled by the control unit 3, so that the first pressing force applied by the first electrode 1E toward the front surface W1 of the workpiece W can be adjusted. Furthermore, the second actuator 2A, which urges the second electrode 2E toward the front surface W1 of the workpiece W, is controlled by the control unit 3, so that the second pressing force applied by the second electrode 2E toward the front surface W1 of the workpiece W can be adjusted. Therefore, the first pressing force applied by the first electrode 1E and the second pressing force applied by the second electrode 2E can be controlled independently, contributing to balanced support of the workpiece W. This also contributes to improving welding quality.

[0071] (4) According to the control unit 3 of this embodiment, the first actuator 1A and the second actuator 2A are controlled according to a preset profile so that the difference between the first and second pressurizing forces falls within a predetermined range. Therefore, the workpiece W can be supported in a balanced manner without being supported in an unbalanced state where the difference between the first and second pressurizing forces exceeds the predetermined range. This also further improves welding quality.

[0072] (5) If the first electrode 1E and the second electrode 2E are welding electrodes and the support electrode 5E of the support member 5 is a ground electrode, two locations where the first electrode 1E and the second electrode 2E contact the workpiece W can be simultaneously welded. (6) However, if the support electrode 5E is not provided on the support member 5 and one of the first electrode 1E and the second electrode 2E is a welding electrode and the other is a ground electrode, welding can be performed at a single location where the welding electrode contacts the workpiece W. In other words, welding can be performed at a single location where one of the first electrode 1E and the second electrode 2E contacts the workpiece W (so-called "indirect spot welding").

[0073] (7) If a rod-shaped member that bends toward the back surface W2 of the workpiece W is used as the support member 5, it contributes to improving the degree of freedom in adapting to various shapes that can be adopted for the workpiece W. For example, when welding a workpiece W with large irregularities, by using a rod-shaped support member 5 that is bent so as to wrap around the back surface W2 of the workpiece W without interfering with the irregularities of the workpiece W, the workpiece W with large irregularities is held by the support member 5 from the back surface W2 side, thereby increasing the supportability of the workpiece W and improving welding quality.

[0074] [II. Modifications] The above-described embodiment is merely an example, and is not intended to exclude various modifications and application of techniques not explicitly described in this embodiment. Each configuration of this embodiment can be modified in various ways without departing from the spirit of the invention. Furthermore, the configurations can be selected and combined as needed.

[0075] The welding device 1 of this embodiment only needs to include at least a rotation mechanism 4 that rotates the first member 41 and the second member 42 in opposite directions and at the same speed, a first electrode 1E fixed to the first member 41 and capable of contacting the front surface W1 of the workpiece W, a second electrode 2E fixed to the second member 42 and capable of contacting the front surface W1 of the workpiece W, and a support member 5 that can contact the back surface W2 of the workpiece W at at least one point on the perpendicular bisector P. For example, the rotation mechanism 4 does not need to be provided with a reducer 40, and the shapes and configurations of the first member 41 and the second member 42 are also examples. Furthermore, the support member 5 is not limited to being detachably held by the device main body 6, and may be fixed to the device main body 6.

[0076] The rotation mechanism 4 is not limited to the mechanism described above in one embodiment. For example, in one embodiment, instead of the rotation mechanism 4 described above, any one of a first rotation mechanism 14 as shown in FIG. 8, a second rotation mechanism 24 as shown in FIG. 9, and a third rotation mechanism 34 as shown in FIG. 10 may be used. The first rotation mechanism 14 and the second rotation mechanism 24 receive rotational power from rotation shafts 41R and 41R' that are rotationally driven by a single drive unit (not shown in FIGS. 8 and 9). The third rotation mechanism 34 receives rotational power from rotation shafts 41R" and 42R" that are rotationally driven by two drive units (not shown in FIG. 10).

[0077] 8, the first rotation mechanism 14 is provided with a first reducer 170 that is substantially similar to the above-described first reducer 70, and a second reducer 180 that is different from the above-described second reducer 80. However, the first reducer 170 of the first rotation mechanism 14 differs only in that a first case 171 and a first output flange 172 of the first reducer 170 are arranged in this order from the X2 direction to the X1 direction, and the first case 171 is fixed so as not to rotate.

[0078] The first rotation mechanism 14 is provided with only the above-described first rotation shaft (hereinafter simply referred to as the "rotation shaft") 41R, and is provided with a third rotation shaft A3 (described below) instead of the above-described second rotation shaft 42R. Rotational power is input from the rotation shaft 41R to a first reducer 170, and the rotational power is output from a first output flange 172 of the first reducer 170 to a second reducer 180. The first output flange 172 can be rephrased as a first member 141 to which a first welding gun (not shown) is attached.

[0079] The second reducer 180 illustrated in Figure 8 includes four (plural) gears: a first gear G1, a second gear G2, a third gear G3, and a fourth gear G4. These gears G1, G2, G3, and G4 are combined to form a second member 142 that rotates integrally with the fourth gear G4. A second welding gun (not shown) is attached to the second member 142. For convenience, in Figure 8, the reference numeral for the first output flange 172 is followed by the reference numeral for the first member 141 in parentheses, and the reference numeral for the second member 142 is followed by the reference numeral for the fourth gear G4 in parentheses.

[0080] The rotational power output from the first output flange 172 of the first reducer 170 is transmitted in this order through the first gear G1, the second gear G2, the third gear G3, and the fourth gear G4, and then transmitted to the second member 142 that rotates integrally with the fourth gear G4. The rotational power is input to the first gear G1 from the first output flange 172. For convenience of illustration, FIG. 8 shows the first gear G1 that meshes with the first output flange 172.

[0081] The first gear G1 and the second gear G2 are fixed to a first rotation axis A1 common to the first gear G1 and the second gear G2 and rotate integrally therewith about the first rotation axis A1, the third gear G3 rotates about the second rotation axis A2, and the fourth gear G4 rotates about the third rotation axis A3. The first rotation axis A1 and the second rotation axis A2 are disposed at positions different from the rotation axis 41R when viewed in the X direction. The third rotation axis A3 is disposed coaxially with the rotation axis 41R when viewed in the X direction.

[0082] The first rotation shaft A1 extends over an X-direction region overlapping with the first reducer 170. The second rotation shaft A2 and the third rotation shaft A3 extend only in a region on the X1-direction side of the first reducer 170. The first gear G1 is a spur gear that rotates in an opposite direction to the rotation of the first output flange 172 of the first reducer 170 in conjunction with the rotation of the first output flange 172. The second gear G2 is a spur gear to which the rotational power from the first gear G1 is transmitted by the first rotation shaft A1 and which rotates in the same direction and at the same speed as the first gear G1.

[0083] The third gear G3 is a spur gear that meshes with the second gear G2 and the fourth gear G4 and rotates in the opposite direction to the second gear G2 and the fourth gear G4. That is, the fourth gear G4 is a spur gear that rotates in the opposite direction to the third gear G3. In this way, the fourth gear G4 rotates in the opposite direction to the rotation direction of the first output flange 172 in conjunction with the rotation of the first output flange 172. The number of teeth of each of the four gears G1, G2, G3, and G4 is set so that the rotation speed of the first output flange 172 and the rotation speed of the fourth gear G4 are the same.

[0084] 9 , the second rotation mechanism 24 is provided with a first bevel gear B1, a second bevel gear B2, and a third bevel gear B3. In the second rotation mechanism 24, as described above in one embodiment, the first rotation shaft 41R and the second rotation shaft 42R of the rotation shaft 4R are not connected, and a second rotation shaft 42R' is provided that is separated from the first rotation shaft 41R' to which rotational power is input, and a third rotation shaft 43R' is also provided that is perpendicular to the rotation shafts 41R' and 42R'.

[0085] The second bevel gear B2 is provided in mesh with the first bevel gear B1 and the third bevel gear B3. Therefore, rotational power in the second rotation mechanism 24 is transmitted in the order of the first bevel gear B1, the second bevel gear B2, and the third bevel gear B3. The first bevel gear B1 rotates integrally with a first member 241 to which a first welding gun (not shown) is attached. The third bevel gear B3 rotates integrally with a second member 242 to which a second welding gun (not shown) is attached. Note that, for convenience, in FIG. 9 , the reference numeral of the first bevel gear B1 is given in parentheses next to the reference numeral of the first member 241, and the reference numeral of the third bevel gear B3 is given in parentheses next to the reference numeral of the second member 242.

[0086] The first bevel gear B1 is a bevel gear that rotates integrally with the first member 241. The first bevel gear B1 is fixed to the first rotation shaft 41R' and rotates integrally therewith about the first rotation shaft 41R'. The second bevel gear B2 is a bevel gear that rotates about the third rotation shaft 43R' and rotates the third bevel gear B3 in the direction opposite to the rotation direction of the first bevel gear B1. In other words, the third bevel gear B3 is a bevel gear that rotates in the opposite direction to the first bevel gear B1.

[0087] The first bevel gear B1 and the third bevel gear B3 illustrated here have the same number of teeth. More specifically, the number of teeth of each of the three bevel gears B1, B2, and B3 is set so that the rotation speed of the first bevel gear B1 (i.e., the first member 241) is the same as the rotation speed of the third bevel gear B3 (i.e., the second member 242). The drive unit (not shown in FIG. 9 ) that inputs rotational power to the second rotation mechanism 24 is not limited to a drive unit that rotates the first rotation shaft 41R', but may also be a drive unit that rotates the second rotation shaft 42R' or the third rotation shaft 43R'.

[0088] 10 , the third rotation mechanism 34 is provided with a first reducer 370 and a second reducer 380. However, in one embodiment, the third rotation mechanism 34 is provided with the first rotation shaft 41R and the second rotation shaft 42R of the rotation shaft 4R that are not connected to each other as described above, but with the first rotation shaft 41R″ and the second rotation shaft 42R″ that are separated from each other.

[0089] Furthermore, in the third rotation mechanism 34, rotational power is input to each of the first reducer 370 and the second reducer 380 without power being transmitted from one to the other. Specifically, the first rotating shaft 41R" is rotationally driven by a first drive unit (not shown), and the second rotating shaft 42R" is rotationally driven by a second drive unit. The rotation directions of the first rotating shaft 41R" driven by the first drive unit and the second rotating shaft 42R" driven by the second drive unit are set to be opposite to each other. In other words, the rotational drive direction by the first drive unit is set to be opposite to the rotational drive direction by the second drive unit.

[0090] In this third rotation mechanism 34, the first case 371 and first output flange 372 of the first reducer 370 and the second output flange 382 and second case 381 of the second reducer 380 are arranged in this order from the X2 direction to the X1 direction. The first output flange 372 can be said to be the first member 341 to which a first welding gun (not shown) is attached, and the second output flange 382 can be said to be the second member 342 to which a second welding gun (not shown) is attached. For convenience, in Figure 10, the reference numeral of the first output flange 372 is given in parentheses the reference numeral of the first member 341, and the reference numeral of the second output flange 382 is given in parentheses the reference numeral of the second member 342.

[0091] The first case 371 and the second case 381 are each fixed so as to be non-rotatable. For example, the first case 371 of the first reducer 370 and the second case 381 of the second reducer 380 are connected by a connecting member 378 (shown by a thick dashed line in FIG. 10 ). However, the connecting member 378 may be omitted from the third rotation mechanism 34, and the first case 371 and the second case 381 may each be fixed so as to be non-rotatable.

[0092] In the first reducer 370, with the first case 371 fixed so as to be non-rotatable, the rotational power of the first rotating shaft 41R" is output to the first output flange 372. The first output flange 372 rotates in the same direction as the rotational direction of the first rotating shaft 41R". In the second reducer 380, with the second case 381 fixed so as to be non-rotatable, the rotational power of the second rotating shaft 42R" is output to the second output flange 382. The second output flange 382 rotates in the same direction as the rotational direction of the second rotating shaft 42R".

[0093] Since the rotation directions of the first rotating shaft 41R" and the second rotating shaft 42R" are set opposite to each other, the second output flange 382 rotates in the opposite direction to the first output flange 372. In the third rotation mechanism 34 described above, the reduction ratios of the first reducer 370 and the second reducer 380 are set, or the rotation speeds of the drive parts that rotate the first rotating shaft 41R" and the second rotating shaft 42R" are adjusted, so that the rotation speed of the first output flange 372 and the rotation speed of the second output flange 382 are the same.

[0094] The control units 3 of the welding guns 21 and 22 are not limited to a configuration in which they control the actuators 1A and 2A according to a preset profile so that the difference between the first and second pressurizing forces falls within a predetermined range, but may be any control configuration. Alternatively, the control units 3 of the welding guns 21 and 22 may be omitted from the welding apparatus 1.

[0095] The support member 5 is not limited to a rod-shaped member that bends toward the back surface W2 of the workpiece W as described above in the embodiment, and various other members can be used as long as they can freely come into contact with the back surface W2 of the workpiece W. Furthermore, the support member 5 may be configured to be able to come into contact with the back surface W2 of the workpiece W at two or more locations on the perpendicular bisector P as viewed in the X direction, or multiple support members 5 may be provided so as to be able to come into contact with the back surface W2 of the workpiece W at two or more locations.

[0096] The present invention is applicable to manufacturing industries that use welding equipment.

[0097] DESCRIPTION OF SYMBOLS 1 Welding device 14 First rotation mechanism (rotation mechanism) 24 Second rotation mechanism (rotation mechanism) 34 Third rotation mechanism (rotation mechanism) 1A First actuator 1E First electrode 2A Second actuator 2E Second electrode 21 First welding gun 22 Second welding gun 3 Control unit 4 Rotation mechanism 41, 141, 241, 341 First member 42, 142, 242, 342 Second member 4R, 41R, 41R', 41R", 42R, 42R', 42R" Rotation shaft 5 Support member 5E Support electrode 6 Device body P Perpendicular bisector S Line segment W Workpiece W1 Front surface W2 Back surface

Claims

1. A welding device used for welding workpieces, comprising: a rotation mechanism that rotates a first member and a second member in opposite directions perpendicular to a predetermined direction at the same speed by rotational power input to a rotation shaft extending along the predetermined direction; a first electrode that extends in the predetermined direction, is fixed to the first member, and is capable of contacting the surface of the workpiece; a second electrode that extends in the predetermined direction, is fixed to the second member, and is capable of contacting the surface of the workpiece; and a support member that is capable of contacting the back surface of the workpiece at at least one location on the perpendicular bisector of a line segment connecting the first electrode and the second electrode when viewed from the predetermined direction.

2. The welding device according to claim 1, further comprising a device body for detachably holding said support member.

3. The welding device according to claim 1 or 2, characterized in that it comprises: a first actuator that urges the first electrode against the surface; a second actuator that urges the second electrode against the surface; and a control unit that controls the first actuator and the second actuator.

4. The welding device described in claim 3, characterized in that the control unit controls the first actuator and the second actuator according to a preset profile so that the difference between the first pressure force, which is the magnitude of the force that urges the first electrode against the surface, and the second pressure force, which is the magnitude of the force that urges the second electrode against the surface, falls within a predetermined range.

5. A welding device as set forth in claim 1 or 2, characterized in that the first electrode and the second electrode are welding electrodes, and the support member has an earth electrode that can be freely brought into contact with the back surface on the perpendicular bisector.

6. The welding device according to claim 1 or 2, wherein one of the first electrode and the second electrode is a welding electrode and the other is an earth electrode.

7. A welding device according to claim 1 or 2, characterized in that the support member is a rod-shaped member that is bent toward the rear surface side.

Images