Welding equipment

Abstract

A welding apparatus (1) used for welding a workpiece (W) comprises a rotating mechanism (4), a first electrode (1E), a second electrode (2E), and a support member (5). The rotating mechanism (4) rotates the first member (41) and the second member (42) in directions perpendicular to the predetermined direction, in opposite directions and at the same speed, by rotational power input to a rotating shaft (4R) extending along a predetermined direction. The first electrode (1E) extends in a predetermined direction along the rotating shaft (4R) of the rotating mechanism (4), is fixed to the first member (41), and can freely contact the surface (W1) of the workpiece (W). The second electrode (2E) extends in the above predetermined direction, is fixed to the second member (42), and can freely contact the surface (W1) of the workpiece (W). The support member (5) is able to abut against the back surface (W2) of the workpiece (W) at at least one point on the perpendicular bisector (P) of the line segment (S) connecting the first electrode (1E) and the second electrode (2E) when viewed from a predetermined direction.

Description

Technical Field

[0001] This invention relates to a welding apparatus for welding a workpiece.

Background Art

[0002] As one of the welding methods, resistance welding is known, in which an electric current is passed through a workpiece against which an electrode is abutted, and the melted portion of the workpiece due to resistance heating is welded. Regarding an apparatus for performing such resistance welding, a technique has been proposed in which two electrodes that are pressurized from one side of the workpiece and one electrode that is pressurized from the other side of the workpiece are provided.

[0003] For example, Patent Document 1 discloses an apparatus provided with a first electrode and a second electrode for sandwiching a workpiece and welding a flange joint portion, and a third electrode disposed at a position on the same side of the workpiece as the position where the first electrode is located and different from the first electrode. If one side surface of the workpiece is called the front (omote) and the surface opposite to one side of the workpiece is called the back (ura), the apparatus of Patent Document 1 can be paraphrased as 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the apparatus disclosed in Patent Document 1, at the point where one of the two electrodes provided on the front side of the workpiece abuts against it, it is supported by being sandwiched between the electrodes provided on the back side. On the other hand, in this apparatus, at the point where the other of the two electrodes provided on the front side abuts against it, it is not supported from the back side. In this cantilevered support state, where one of the two electrodes provided on the front side is supported from the back side but the other is not, even if sufficient pressure can be secured on the workpiece by one electrode, sufficient pressure cannot be secured on the workpiece by the other electrode, which may lead to a decrease in welding quality. Therefore, there is room for improvement in ensuring welding quality.

[0006] The welding apparatus in question was devised in light of these challenges, and one of its objectives is to ensure welding quality. However, beyond this objective, another objective of this invention is to achieve effects and benefits that cannot be obtained with conventional technology, derived from the various configurations described in the "Modes for Carrying Out the Invention" section below. [Means for solving the problem]

[0007] The disclosed welding apparatus can be realized in the following embodiments (examples of application) and solves at least some of the above-mentioned problems. Each of embodiments from Embodiment 2 onward is an additional embodiment that can be appropriately selected and is an embodiment that can be omitted. None of embodiments from Embodiment 2 onward disclose any embodiments or configurations that are essential to this case.

[0008] Embodiment 1. The welding apparatus disclosed is used for welding workpieces and comprises a rotating mechanism, a first electrode, a second electrode, and a support member. The rotating mechanism rotates the first member and the second member in directions perpendicular to the predetermined direction, in opposite directions and at the same speed, by rotational power input to a rotating shaft extending along a predetermined direction. The first electrode extends in the predetermined direction, is fixed to the first member, and is able to abut against the surface of the workpiece. The second electrode extends in the predetermined direction, is fixed to the second member, and is able to abut against the surface. The support member is able to abut against the back surface of the workpiece at least at one point on the perpendicular bisector of the line segment connecting the first electrode and the second electrode, from a viewpoint in the predetermined direction.

[0009] Embodiment 2. In Embodiment 1 described above, it is preferable that the welding apparatus includes a device body that detachably holds the support member. Embodiment 3. In Embodiment 1 or 2 described above, the welding apparatus preferably comprises a first actuator for biasing the first electrode to the surface, a second actuator for biasing the second electrode to the surface, and a control unit for controlling the first actuator and the second actuator.

[0010] Embodiment 4. In Embodiment 3 described above, it is preferable that the control unit controls the first actuator and the second actuator according to a preset profile such that the difference between the first pressing force, which is the magnitude of the force that biases the first electrode on the surface, and the second pressing force, which is the magnitude of the force that biases the second electrode on the surface, falls within a predetermined range.

[0011] Embodiment 5. In any one of embodiments 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 abut against the back surface on the vertical bisector.

[0012] Embodiment 6. In any one of embodiments 1 to 4 described 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 the above Aspects 1 to 6, it is preferable that the support member is a rod-shaped member that bends toward the back side.

Advantages of the Invention

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

Brief Description of the Drawings

[0014] [Figure 1] It is an elevation view showing a robot arm to which a welding apparatus according to an embodiment is applied, together with the welding apparatus. [Figure 2] It is a perspective view schematically showing a welding apparatus according to an embodiment. [Figure 3] It is a plan view schematically showing a state where the electrodes of a welding apparatus according to an embodiment are closest to each other. [Figure 4] It is a plan view schematically showing a state where the electrodes of a welding apparatus according to an embodiment are most separated from each other. [Figure 5] It is a perspective view schematically showing a rotation mechanism provided in a welding apparatus according to an embodiment. [Figure 6] It is a partially exploded perspective view of FIG. 5. [Figure 7] It is a perspective view schematically showing a single reduction gear used in a rotation mechanism provided in a welding apparatus according to an embodiment. [Figure 8] It is a schematic diagram showing a first rotation mechanism of a welding apparatus according to a modification. [Figure 9] It is a schematic diagram showing a second rotation mechanism of a welding apparatus according to a modification. [Figure 10] It is a schematic diagram showing a third rotation mechanism of a welding apparatus according to a modification.

Modes for Carrying Out the Invention

[0015] Referring to the drawings, an embodiment of the welding apparatus will be described. The welding apparatus of the present embodiment is an apparatus for resistance welding metal materials such as steel materials and aluminum materials with a pair of welding guns. Examples of workpieces (welding targets) welded by a welding device include metal members used in vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). A plug-in hybrid electric vehicle means a hybrid electric vehicle capable of external charging of a battery or external power supply from the battery. A plug-in hybrid electric vehicle is provided with a charging port (inlet) for inserting a charging cable through which power is supplied from an external charging facility and an outlet for external power supply.

[0016] In the following embodiments, a rectangular coordinate system having three mutually orthogonal coordinate axes, the X-axis, the Y-axis, and the Z-axis, is used as a reference for the directions used in the description of the welding device. In this rectangular coordinate system, the direction along the X-axis is referred to as the "X direction" (predetermined direction, 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] In the X direction, the direction from the negative to the positive of the X-axis and the direction from the positive to the negative of the X-axis are opposite to each other, and two types of directions are inherent. Therefore, one of the X directions is referred to as the "X1 direction", and the other of the X directions is referred to as the "X2 direction". Similarly, for the Y direction, one is referred to as the "Y1 direction", and the other is referred to as the "Y2 direction". For the Z direction as well, one is referred to as the "Z1 direction", and the other is referred to as the "Z2 direction".

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

[0019] [I. One Embodiment] [1. Structure] Figure 1 is an elevation view showing a robot arm to which a welding apparatus according to one embodiment is applied. Figure 2 is a schematic perspective view showing a welding apparatus according to one embodiment. Figure 3 is a schematic plan view showing the state in which the electrodes of the welding apparatus according to one embodiment are closest to each other. Figure 4 is a schematic plan view showing the state in which the electrodes of the welding apparatus according to one embodiment are furthest apart.

[0020] [1-1. Examples of Welding Equipment Applications] As shown in Figure 1, the welding apparatus 1 of this embodiment is attached to the tip 9a of the robot arm 9. The robot arm 9 is an industrial robot that changes the position and orientation of various devices attached to its tip 9a. The robot arm 9 illustrated in Figure 1 is a vertical articulated robot equipped with multiple arms 91, joints 92 on 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 orientation suitable for welding.

[0021] [1-2. Welding equipment] As shown in Figure 2, the welding apparatus 1 is equipped with a first welding gun 21 and a second welding gun 22, a control unit 3, and a rotation mechanism 4 for changing the relative positions of the two welding guns 21 and 22. The welding apparatus 1 described here is equipped with a support member 5 for supporting the workpiece W (shown as a dashed line in Figure 2), and a main apparatus body 6 to which various devices, including the support member 5, are attached.

[0022] =Welding gun= Each of the welding guns 21 and 22 has electrodes 1E and 2E (referred to as "E" unless otherwise distinguished) provided at the end (tip) in the X1 direction, actuators 1A and 2A (referred to as "A" unless otherwise distinguished) provided at the end (base) in the X2 direction, and a main body 1B and 2B (referred to as "B" unless otherwise distinguished) provided between the electrode E and actuator A in the X direction, and has welding centers 1C and 2C (referred to as "C" unless otherwise distinguished) extending in the X direction. Each electrode E of the welding guns 21 and 22 is positioned to overlap with each welding center C when viewed from the X direction (view in the X direction, which is the axial view of the rotation axis 4R described later, and view in a predetermined direction, which is the viewpoint from a predetermined direction). Preferably, the centers of each electrode E of the welding guns 21 and 22 and each welding center C are positioned on the same line.

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

[0024] Actuator A is a drive source that biases electrode E in the X1 direction. In other words, actuator A biases electrode E against the surface W1 of workpiece W. Actuator A is equipped with a motor body that generates a biasing force that presses electrode E against the surface W1 of workpiece W, and an encoder for adjusting the amount of rotation of the motor body (degree of drive, rotation angle, rotation speed). The main body B incorporates a mechanism (not shown in the figure) that transmits the biasing force from the motor body of actuator A to electrode E. The main body B shown in Figure 2 is cylindrical in shape with a cylindrical axis along the X direction.

[0025] Hereafter, each element provided in the first welding gun 21, such as electrode E and actuator A, will be prefixed with "first" and the number "1" in its name. Similarly, each element provided in the second welding gun 22 will be prefixed with "second" and the number "2" in its name. For example, electrode E provided in the first welding gun 21 will be called "first electrode 1E," and actuator A provided in the second welding gun 22 will be called "second actuator 2A."

[0026] ==Command== The control unit 3 is a controller (electronic control device, control board, controller, etc.) that controls actuators 1A and 2A that bias electrodes 1E and 2E on the surface W1 of the workpiece W. Here, the magnitude of the force that biases the first electrode 1E to the surface W1 of the workpiece W is defined as the "first pressure," and the magnitude of the force that biases the second electrode 2E to the surface W1 of the workpiece W is defined as the "second pressure." The control unit 3 illustrated in this embodiment controls the first actuator 1A and the second actuator 2A according to a preset profile so that the difference between the first pressure and the second pressure falls within a predetermined range. The "predetermined range" here includes a range in which the difference between the first pressure and the second pressure does not become excessively large, and an appropriate range determined by the properties of the workpiece W.

[0027] ==Rotation Mechanism== The rotation mechanism 4 is a mechanism that rotates the first member 41 and the second member 42, which will be described later, in opposite directions and at the same speed. This rotating mechanism 4 has a rotating shaft 4R (shown as a dashed line in Figure 2) to which rotational power from the drive unit 4S is input, and a reduction gear 40 that reduces and outputs the rotation of the rotating shaft 4R. The drive unit 4S and the reduction gear 40 are arranged coaxially with the axis 4C of the rotating shaft 4R in the welding apparatus 1. This axis 4C extends along the X direction. Therefore, it can be said that the rotating shaft 4R extends along the X direction (a predetermined direction), and it can also be said that the axial direction of the rotating shaft 4R is the X direction.

[0028] The drive unit 4S is not located on the outer circumference of the rotating shaft 4R, but rather on the extending direction of the axis 4C. The drive unit 4S, like actuators 1A and 2A, is equipped with a motor body that generates rotational power and an encoder for adjusting the amount of rotation of the motor body (degree of drive, rotation angle, rotation speed). The reduction gear 40 is equipped 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. Any mechanism can be used in the reduction gear 40 as long as it rotates the first member 41 and the second member 42 in opposite directions and at the same speed.

[0029] Since the first member 41 and the second member 42 rotate around an axis 4C along the X direction, they can be said to be members that rotate in a direction perpendicular to the X direction. Furthermore, if we consider the rotation direction of the first member 41 and the second member 42 as a reference, the rotation axis 4R of the rotation mechanism 4 can be rephrased as extending 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 rotation axis 4R in the first direction (for example, counterclockwise from a viewpoint looking from the X2 direction towards the X1 direction), the first member 41 rotates in the opposite direction to the first direction, and the second member 42 rotates in the first direction. Conversely, when the drive unit 4S rotates the rotation axis 4R in the second direction (for example, clockwise from a viewpoint looking from the X2 direction towards the X1 direction), the first member 41 rotates in the opposite direction to the second direction (i.e., the first direction as described above), and the second member 42 rotates in the second direction.

[0031] A first welding gun 21 is attached to the first member 41. Specifically, the first main body 1B of the first welding gun 21 is fixed to the outer circumferential surface 4a of the first member 41. As a result, the first electrode 1E is fixed to the first member 41 via the first main body 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, the second main body 2B of the second welding gun 22 is fixed to the outer circumferential surface 4b of the second member 42. As a result, the second electrode 2E is fixed to the second member 42 via the second main body 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 the welding guns 21 and 22 are to be moved apart, the drive unit 4S rotates the rotation shaft 4R in the first direction, causing the outer surface 4a of the first member 41 to rotate in the second direction, and the outer surface 4b of the second member 42 to rotate in the first direction. When the welding guns 21 and 22 are to be moved closer together, the drive unit 4S rotates the rotation shaft 4R in the second direction, causing the outer surface 4a of the first member 41 to rotate in the first direction, and the outer surface 4b of the second member 42 to rotate in the second direction. In this way, the relative position of the welding guns 21 and 22 is changed by the rotation mechanism 4 which rotates the first member 41 and the second member 42 in opposite directions and 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 explanation, the phase at which the outer surface 4a of the first member 41 is most rotated in the first direction is called the "first minimum phase," and the phase at which the outer surface 4b of the second member 42 is most rotated in the second direction is called the "second minimum phase." Furthermore, the phase at which the outer surface 4a of the first member 41 is most rotated in the second direction is called the "first maximum phase," and the phase at which the outer surface 4b of the second member 42 is most rotated in the first direction is called the "second maximum phase."

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

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

[0036] As shown in Figures 3 and 4, in the view in the X direction, line segment S extends along the Y direction, and the perpendicular bisector P of line segment S extends along the Z direction. If the first dimension L1 is the distance that the first electrode 1E is separated from the perpendicular bisector P toward the Y1 direction (one side), and the second dimension L2 is the distance that the second electrode 2E is separated from the perpendicular bisector P toward the Y2 direction (the other side), then regardless of the length of dimensions L1 and L2, the first dimension L1 and the second dimension L2 are maintained at equal dimensions (L1=L2, so to speak, "equal pitch").

[0037] In this example, the axis 4C of the rotation axis 4R intersects the perpendicular bisector P. In particular, in the maximum pitch state illustrated in Figure 4, the axis 4C of the rotation axis 4R extends in the Z direction through the intersection of line segment S and the perpendicular bisector P. If we liken the system to an analog clock with the axis of rotation 4R centered at the axis 4C and the hour hand pointing in the Z1 direction to 12 o'clock, the first electrode 1E with the first minimum phase is positioned at 1 o'clock, and the second electrode 2E with the second minimum phase is positioned at 11 o'clock. Similarly, if we liken the system to an analog clock, the first electrode 1E with the first maximum phase is positioned at 3 o'clock, and the second electrode 2E with the second maximum phase is positioned at 9 o'clock. By likening the system to the analog clock described above, the relative positions of electrodes 1E and 2E are changed when the first electrode 1E is displaced from either the 3 o'clock position or the 1 o'clock position to the other, and when the second electrode 2E is displaced 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 explained below with reference to Figures 5 to 7. Figure 5 is a schematic perspective view showing a rotating mechanism 4 provided in a welding apparatus 1 according to one embodiment. Figure 6 is a perspective view showing a part of Figure 5 in an exploded view. Figure 7 is a schematic perspective view showing the reduction gears 70 and 80 used in the rotating mechanism 4 provided in the welding apparatus 1 according to one embodiment. In the rotating mechanism 4 illustrated here, as shown in Figures 5 and 6, there is only one drive unit 4S (see Figure 2) that rotates the rotating shaft 4R, while the reduction gear 40 consists of two units: a first reduction gear 70 and a second reduction gear 80. Each reduction gear 70 and 80 receives the rotational power from the rotating shaft 4R.

[0039] First, the common configuration of the reduction gears 70 and 80 will be explained with reference to Figure 7. The gearboxes 70 and 80 are gearboxes in which the rotating shafts 41R and 42R (4R), cases 71 and 81, and output flanges 72 and 82 are arranged coaxially with each other. If we consider the rotating shafts 41R and 42R as the first elements, the cases 71 and 81 as the second elements, and the output flanges 72 and 82 as the third elements, then gearboxes 70 and 80 can be described as three-element, two-degree-of-freedom gearboxes. In this context, a three-element, two-degree-of-freedom gearbox means a gearbox in which, once the rotational speeds of two of the three elements are determined, the rotational speed of the remaining element is uniquely determined.

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

[0041] Each reduction gear 70, 80 is provided with spur gears 7s, 8s that mesh with an input gear 4i located on the outer circumference of the rotating shaft 4R, and cases 71, 81 and output flanges 72, 82 that are rotatably mounted in accordance with the rotation of each spur gear 7s, 8s.

[0042] Specifically, the first reduction gear 70 is equipped with a first spur gear 7s, a first case 71 (first output section), and a first output flange 72 (second output section). The first reduction gear 70 is set to a first reduction ratio i1. Furthermore, the second reduction gear 80 is equipped with a second spur gear 8s, a second case 81 (third output section), and a second output flange 82 (fourth output section). The second reduction gear 80 is set to a second reduction ratio i2.

[0043] The first case 71 and the second case 81 are provided with a rotating shaft 4R inserted through them, allowing them to rotate freely around the rotating shaft 4R. The first output flange 72 is rotatably mounted on the first case 71. Similarly, the second output flange 82 is rotatably mounted on 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 arranged in a cylindrical (annular) shape around 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 the part inserted through the first case 71 and the first output flange 72 of the first reduction gear 70, and a second rotating shaft 42R, which is the part inserted through the second case 81 and the second output flange 82 of the second reduction gear 80. These first rotating shaft 41R and second rotating shaft 42R are connected to each other along the axis 4C and rotate together as a single unit.

[0045] Each of the cases 71 and 81, and each of the output flanges 72 and 82, can output rotational power without being constrained by other elements. Furthermore, they can be used in ways such as being fixed to other fixed (immovable) members and thus immobile, or being constrained to rotate integrally with other rotating elements. Therefore, it can be said that the cases 71 and 81 and the output flanges 72 and 82 are elements (output units) that can reduce and output the rotational power of the rotating shaft 4R according to the reduction ratios i1 and i2 of the reducers 70 and 80.

[0046] One common application of the reducers 70 and 80 is to output rotational power to the output flanges 72 and 82 while the cases 71 and 81 are fixed in a non-rotatable state. The first reduction ratio i1 of the first reducer 70 is defined as the value obtained by dividing the rotational speed of the first output flange 72 by the rotational speed of the first rotating shaft 41R, while the first case 71 is fixed in a non-rotatable state. The second reduction ratio i2 of the second reducer 80 is defined as the value obtained by dividing the rotational speed of the second output flange 82 by the rotational speed of the second rotating shaft 42R, while the second case 81 is fixed in a non-rotatable state.

[0047] Cases 71 and 81 are case-shaped members that house the spur gears 7s and 8s on the shaft 4C side (so to speak, the inside). These cases 71 and 81 are designed to rotate in the opposite direction to the rotation direction of the rotating shaft 4R, regardless of the reduction ratios i1 and i2 of the reducers 70 and 80, provided that the output flanges 72 and 82 are fixed so as not to rotate. The output flanges 72 and 82 are positioned at different locations in the X-direction relative to the cases 71 and 81. The output flanges 72 and 82 can also be described as flange-shaped protrusions along the X-direction. Since the output flanges 72 and 82 are not fixed to prevent rotation, their rotation direction is determined by the reduction ratios i1 and i2 of the reducers 70 and 80.

[0048] Next, the configurations of the reduction gears 70 and 80 will be explained with reference to Figures 5 and 6. In the reduction gear 40, the first output flange 72 and first case 71 of the first reduction gear 70 and the second case 81 and second output flange 82 of the second reduction gear 80 are arranged in the 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) relative to the first case 71, the second case 81 is located on the X1 direction side (the other side) relative to the first case 71, and the second output flange 82 is located on the X1 direction side (the other side) relative to the second case 81.

[0049] In the gearbox 40 illustrated in Figure 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 they rotate together as a single unit, and is provided in a cylindrical shape coaxial with the axis 4C, just like the cases 71 and 81. However, a gearbox 40 in which the cases 71 and 81 are directly connected may be used without the connecting member 78.

[0050] The first reduction gear 70 reduces the rotational power of the rotating shaft 4R by a first reduction ratio i1 with the first output flange 72 fixed in a non-rotatable position and outputs it to the first case 71. In this way, the first reduction gear 70, with the first output flange 72 fixed in a non-rotatable position, causes the outer surface 73 of the first case 71 to rotate in the opposite direction to the rotation of the rotating shaft 4R, regardless of the reduction ratios i1 and i2 of the reduction gears 70 and 80.

[0051] The second reducer 80 reduces the rotational power of the rotating shaft 4R by a second reduction ratio i2 with the second case 81 fixed to the first case 71, and outputs it to the second output flange 82. In this way, in the second reducer 80, where the rotational power of the first case 71, which has been reduced by a first reduction ratio i1, is input to the second case 81, the direction in which the outer surface 83 of the second output flange 82 rotates is determined by the reduction ratios i1 and i2 of the reducers 70 and 80.

[0052] Specifically, the first reduction ratio i1 of the first reducer 70 is expressed by equation 1 below, and the second reduction ratio i2 of the second reducer 80 is expressed by equation 2 below.

[0053]

number

[0054] Note that rotational speeds a, b, and c are positive values ​​when rotating in the same direction as the rotational axis 4R, and negative values ​​when rotating in the opposite direction. The rotational speed a of the rotating shaft 4R can only take positive values, the rotational speed b of the first case 71 can only take negative values, and the rotational speed c of the second output flange 82 can take positive or negative values ​​depending on the reduction ratios i1 and i2.

[0055] In the first example of the gearbox 40 described here, the relative magnitudes of the first reduction ratio i1 and the second reduction ratio i2 are set to satisfy predetermined conditions. Here, "predetermined conditions" means that the rotational speed c of the second output flange 82 is a positive value, and the absolute values ​​of the rotational speed c of the second output flange 82 and the rotational speed b of the first case 71 are equal to each other. In other words, the relative magnitudes of the first reduction ratio i1 and the second reduction ratio i2 are set to satisfy the predetermined conditions that the rotational speed c of the second output flange 82 and the rotational speed b of the first case 71 are in opposite directions and at the same speed. Specifically, the first reduction ratio i1 is set to half of the second reduction ratio i2.

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

[0057] ==Support Members== However, if the workpiece W is only biased in the X1 direction by two electrodes 1E and 2E, there is a risk that the workpiece W may move away in the X1 direction, making it impossible to ensure sufficient pressure applied by electrodes 1E and 2E to the workpiece W. Furthermore, even if the workpiece W is supported so that it is sandwiched only on the back side of the point where one of the two electrodes 1E and 2E abuts against the workpiece W, there is a risk that the pressing force from the other electrode 1E or 2E cannot be secured.

[0058] Alternatively, if the workpiece W is supported by being sandwiched between the electrodes 1E and 2E at the points where they abut the workpiece W, then although the pressure applied by each electrode 1E and 2E is ensured, two support members are needed on the back of the workpiece W. If support members are to be provided on the back of the workpiece W at two points corresponding to the positions of the electrodes 1E and 2E, the configuration becomes complex, and depending on the shape and size of the workpiece W, the support members and the workpiece W may interfere with each other, potentially restricting the shape and size of the workpiece W.

[0059] Therefore, in order to secure the reaction force of the applied pressure with a simple configuration, the welding apparatus 1 of this embodiment is provided with a support member 5 that abuts against the surface W2 of the workpiece W that faces in the X1 direction (hereinafter referred to as the "back surface"). The support member 5 is provided so as to be able to contact the back surface W2 of the workpiece W at at least one point on the vertical bisector P when viewed in the X direction. Figure 2 illustrates a configuration in which the support member 5 is provided at only one point.

[0060] As shown in Figures 3 and 4, the location of the support member 5 is preferably set in the region between the first midpoint M1 and the second midpoint M2 of the line segment S, including the perpendicular bisector P, in order to easily counteract the pressure applied by electrodes 1E and 2E regardless of their positions. Furthermore, it is even more preferable that the location of the support member 5 (see Figure 2) is midway between the first midpoint M1 and the second midpoint M2 of the perpendicular bisector P.

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

[0062] The support member 5 is formed 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 described above. The support electrode 5E shown here is provided as a ground electrode. On the other hand, the first electrode 1E and the second electrode 2E are provided as welding electrodes. In resistance welding using welding apparatus 1, the areas where the support electrode 5E, which is provided as a ground electrode, comes into contact with the workpiece W are not welded, while the areas where the electrodes 1E and 2E, which are provided as welding electrodes, come into contact with the workpiece W are welded.

[0063] Specifically, electrodes 1E, 2E, and 5E are brought into contact with the workpiece W and current is passed through it. Electrodes 1E and 2E, which are provided as welding electrodes on the workpiece W, melt due to resistive heating at the point of contact with the workpiece W, thereby welding the molten area. Therefore, it is desirable to suppress the contact resistance of the support electrode 5E, which is provided as a ground electrode, in order to suppress the heating of the contact point of the support electrode 5E.

[0064] From this perspective, in the welding apparatus 1 of this embodiment, two electrodes 1E and 2E, provided as welding electrodes, are in contact with the surface W1 of the workpiece W with a first and second applied pressure, while a single support electrode 5E, provided as a ground electrode, supports the workpiece W in a balanced manner by counteracting the combined first and second applied pressure on the back surface W2 of the workpiece W. This balance of applied pressure suppresses the contact resistance of the support electrode 5E, which is provided as a ground electrode, thereby suppressing resistive heating at the contact points of the support electrode 5E. Furthermore, resistive heating at the contact points of electrodes 1E and 2E, which are provided as welding electrodes, is ensured.

[0065] The support member 5 does not necessarily have to be provided with a support electrode 5E. In the case of a support member 5 that does not have a support electrode 5E, a member is provided that protrudes from the end of the second arm portion 52 in the Z1 direction toward the X2 direction instead of the support electrode 5E. 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] ==Main Unit== The support member 5 is detachably held in the main body 6 of the device. By replacing the attached support member 5 with another support member 5 of a different shape or size, various support members 5 can be attached to the main body 6 of the device. The main body 6 of this device is fitted with a rotating mechanism 4, and various other components, including transformers that change and output voltage to the drive unit 4S of the rotating mechanism 4 and the actuators 1A and 2A of the welding guns 21 and 22, may also be fitted with this device.

[0067] Since the main body of the device 6 and the equipment and components attached to the main body of the device 6 are fixed (immovable), the first output flange 72 is set to a fixed point that restricts it from rotating. For example, the first output flange 72 is fixed to a transformer attached to the main body of the device 6.

[0068] [2. Action and Effects] Since the welding apparatus 1 of this embodiment is configured as described above, the following operations and effects can be obtained. (1) According to the welding apparatus 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, the length of the first dimension L1 and the second dimension L2 can be adjusted while maintaining the first dimension L1, which is the distance between the first electrode 1E and the second electrode 2E and the distance between the second electrode 2E and the perpendicular bisector P, to be equal.

[0069] Furthermore, in the view in the X direction, a support member 5 is provided that can abut against the back surface W2 of the workpiece W at at least one point on the perpendicular bisector P of the line segment S connecting the first electrode 1E and the second electrode 2E. By supporting the workpiece W from the back side with the support member 5 arranged in this manner, both a first pressing force that attaches the first electrode 1E to the surface W1 of the workpiece W and a second pressing force that biases the second electrode 2E to the surface W1 of the workpiece W can be ensured. Thus, the welding quality of the workpiece W can be ensured.

[0070] (2) Since the support member 5 is detachably held on the main body 6 of the apparatus, the support member 5 can be replaced with one of a shape and size that contacts the back surface W2 of the workpiece W at an appropriate position according to 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 biases the first electrode 1E to the surface W1 of the workpiece W, is controlled by the control unit 3, thereby allowing adjustment of the first pressure applied by the first electrode 1E to the surface W1 of the workpiece W. Similarly, the second actuator 2A, which biases the second electrode 2E to the surface W1 of the workpiece W, is controlled by the control unit 3, thereby allowing adjustment of the second pressure applied by the second electrode 2E to the surface W1 of the workpiece W. As a result, both the first pressure applied by the first electrode 1E and the second pressure applied by the second electrode 2E can be controlled, contributing to balanced support of the workpiece W. This also improves 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 such that the difference between the first pressing force and the second pressing force falls within a predetermined range. As a result, the workpiece W can be supported in a balanced manner without being supported in an unbalanced state where the difference between the first pressing force and the second pressing force exceeds a predetermined range. From this point of view as well, welding quality can be further improved.

[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 the ground electrode, then two locations on the workpiece W where the first electrode 1E and the second electrode 2E are in contact can be welded simultaneously. (6) However, if the support member 5 is not provided with a support electrode 5E, 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 one point where the welding electrode is in contact with the workpiece W. That is, welding can be performed at one point where one of the first electrode 1E and the second electrode 2E is in contact with the workpiece W (so-called "indirect spot welding").

[0073] (7) If a rod-shaped member that bends toward the back surface W2 side of the workpiece W is used as the support member 5, it contributes to an increased degree of freedom in accommodating various shapes that may be used 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 to the back surface W2 side of the workpiece W without interfering with the irregularities of the workpiece W, the support member 5 can be used to hold the workpiece W with large irregularities from the back surface W2 side, thereby increasing the support of the workpiece W and improving the welding quality.

[0074] [II. Variant Examples] The embodiments described above are merely illustrative, and there is no intention to exclude various modifications or applications of techniques not explicitly stated in these embodiments. Each configuration of these embodiments can be modified in various ways without departing from their spirit. Furthermore, they can be selected and combined as needed.

[0075] The welding apparatus 1 of this embodiment may include at least a rotation mechanism 4 that rotates a first member 41 and a 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 surface W1 of the workpiece W, a second electrode 2E fixed to the second member 42 and capable of contacting the surface W1 of the workpiece W, and a support member 5 capable of contacting 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 reduction gear 40, and the shape and configuration 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 to the device body 6, but may also be fixed to the device body 6.

[0076] The rotating mechanism 4 is not limited to the mechanism described above in one embodiment. For example, in one embodiment, instead of the rotating mechanism 4 described above, one of the first rotating mechanism 14 shown in Figure 8, the second rotating mechanism 24 shown in Figure 9, or the third rotating mechanism 34 shown in Figure 10 may be used. The first rotating mechanism 14 and the second rotating mechanism 24 receive rotational power from rotating shafts 41R and 41R′, which are driven by a single drive unit (not shown in Figures 8 and 9). The third rotating mechanism 34 receives rotational power from rotating shafts 41R″ and 42R″, which are driven by two drive units (not shown in Figure 10).

[0077] ==First Rotation Mechanism== As shown in Figure 8, the first rotating mechanism 14 is provided with a first reduction gear 170 which is substantially the same as the first reduction gear 70 described above, and a second reduction gear 180 which is different from the second reduction gear 80 described above. The only difference is that in the first reduction gear 170 of the first rotating mechanism 14, the first case 171 and the first output flange 172 of the first reduction gear 170 are arranged in the order from the X2 direction to the X1 direction, and the first case 171 is fixed so as not to rotate.

[0078] This first rotation mechanism 14 is provided only with the first rotation shaft (hereinafter abbreviated as "rotation shaft") 41R mentioned above, and the third rotation shaft A3 described later is provided in place of the second rotation shaft 42R mentioned above. Rotational power is input from the rotation shaft 41R to the first reduction gear 170, and rotational power is output from the first output flange 172 of the first reduction gear 170 to the second reduction gear 180. This first output flange 172 can be rephrased as the first member 141 to which the first welding gun (not shown) is attached.

[0079] In the second reduction gear 180 illustrated in Figure 8, four (or more) first gears G1, second gear G2, third gear G3, and fourth gear G4 are provided. 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. In Figure 8, for convenience, 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 fourth gear G4 is followed by the reference numeral for the second member 142 in parentheses.

[0080] The rotational power output from the first output flange 172 of the first reduction gear 170 is transmitted in the order of the first gear G1, second gear G2, third gear G3, and fourth gear G4, and is then transmitted to the second member 142 which rotates integrally with the fourth gear G4. The first gear G1 receives rotational power from the first output flange 172. For convenience, Figure 8 shows the first gear G1 meshing with the first output flange 172.

[0081] The first gear G1 and the second gear G2 are each fixed to a common first rotation axis A1, and rotate together with it around the first rotation axis A1. The third gear G3 rotates around the second rotation axis A2, and the fourth gear G4 rotates around the third rotation axis A3. The first rotation axis A1 and the second rotation axis A2 are located at different locations from the rotation axis 41R when viewed in the X direction. The third rotation axis A3 is located coaxially with the rotation axis 41R when viewed in the X direction.

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

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

[0084] ==Second Rotation Mechanism== As shown in Figure 9, the second rotation mechanism 24 is equipped with a first bevel gear B1, a second bevel gear B2, and a third bevel gear B3. In this 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 disconnected from the first rotation shaft 41R' into which rotational power is input, and a third rotation shaft 43R' is also provided that is perpendicular to these rotation shafts 41R' and 42R'.

[0085] The second bevel gear B2 is meshed with the first bevel gear B1 and the third bevel gear B3. Therefore, the rotational power in the second rotating 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 the first member 241 to which a first welding gun (not shown) is attached. The third bevel gear B3 rotates integrally with the second member 242 to which a second welding gun (not shown) is attached. For convenience, in Figure 9, the reference numeral for the first bevel gear B1 is followed by the reference numeral for the first member 241 in parentheses, and the reference numeral for the third bevel gear B3 is followed by the reference numeral for the second member 242 in parentheses.

[0086] The first bevel gear B1 is a bevel gear that rotates integrally with the first member 241. This first bevel gear B1 is fixed to the first rotation axis 41R' and rotates integrally with it around the first rotation axis 41R'. The second bevel gear B2 rotates the third bevel gear B3 in the opposite direction to the rotation direction of the first bevel gear B1, and is a bevel gear that rotates around the third rotation axis 43R'. 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 exemplified here have the same number of teeth. More specifically, the number of teeth of each of the three bevel gears B1, B2, and B3 are 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). Furthermore, the drive unit (not shown in Figure 9) that inputs rotational power to the second rotation mechanism 24 is not limited to a configuration that rotates the first rotation shaft 41R', but may also rotate the second rotation shaft 42R' or the third rotation shaft 43R'.

[0088] ==Third Rotation Mechanism== As shown in Figure 10, the third rotation mechanism 34 is provided with a first reduction gear 370 and a second reduction gear 380. However, in one embodiment, the first rotation shaft 41R and the second rotation shaft 42R of the rotation shaft 4R are not connected as described above, and the first rotation shaft 41R'' and the second rotation shaft 42R'' are provided separately from each other.

[0089] Furthermore, in the third rotation mechanism 34, rotational power is input to each of the reduction gears 370 and 380 without power being transmitted from one of the first reduction gear 370 to the other. Specifically, the first rotating shaft 41R'' is rotationally driven by a first drive unit (not shown in the diagram), and the second rotating shaft 42R'' is rotationally driven by a second drive unit. The rotational direction of the first rotating shaft 41R'' driven by the first drive unit and the rotational direction of the second rotating shaft 42R'' driven by the second drive unit are set to be opposite to each other. That is, the rotational driving direction by the first drive unit is set to be opposite to the rotational driving 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 reduction gear 370 and the second output flange 382 and second case 381 of the second reduction gear 380 are arranged in that order from the X2 direction to the X1 direction. The first output flange 372 can be replaced with the first member 341 to which a first welding gun (not shown) is attached, and the second output flange 382 can be replaced with the second member 342 to which a second welding gun (not shown) is attached. For convenience, in Figure 10, the reference numeral for the first output flange 372 is followed by the reference numeral for the first member 341 in parentheses, and the reference numeral for the second output flange 382 is followed by the reference numeral for the second member 342 in parentheses.

[0091] The first case 371 and the second case 381 are each fixed in a non-rotatable manner. For example, the first case 371 of the first reduction gear 370 and the second case 381 of the second reduction gear 380 are connected by a connecting member 378 (shown as a thick dashed line in Figure 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 in a non-rotatable manner.

[0092] In the first reduction gear 370, with the first case 371 fixed in a non-rotatable state, 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 rotation of the first rotating shaft 41R″. In the second reduction gear 380, with the second case 381 fixed in a non-rotatable state, 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 rotation of the second rotating shaft 42R″.

[0093] Since the rotation direction of the first rotating shaft 41R″ and the rotation direction of the second rotating shaft 42R″ are set to be opposite to each other, the second output flange 382 rotates in the opposite direction to the first output flange 372. In the third rotating mechanism 34 described above, the reduction ratios of the first reduction gear 370 and the second reduction gear 380 are set, or the rotation speeds of the drive units 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 unit 3 of the welding guns 21 and 22 is not limited to controlling the actuators 1A and 2A according to a preset profile so that the difference between the first and second pressures falls within a predetermined range; it may be any control configuration. Alternatively, the control unit 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 one embodiment, but can be any type of member as long as it can abut against the back surface W2 of the workpiece W. Furthermore, the support member 5 may be configured to abut against the back surface W2 of the workpiece W at two or more points on the vertical bisector P when viewed in the X direction, or multiple support members 5 may be provided to abut against two or more points. [Industrial applicability]

[0096] This technology is applicable to manufacturing industries that use welding equipment. [Explanation of symbols]

[0097] 1. Welding equipment 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 component 42,142,242,342 Second component 4R, 41R, 41R′, 41R″, 42R, 42R′, 42R″ Rotation axis 5. Support Member 5E Support electrode 6. Main unit of the device P perpendicular bisector S line segment Double job W1 surface W2 Reverse side

Claims

1. A welding apparatus used for welding workpieces, A rotation mechanism that rotates a first member and a second member in directions perpendicular to the predetermined direction, in opposite directions and at the same speed, by rotational power input to a rotating shaft extending along a predetermined direction, A first electrode extending in the predetermined direction, fixed to the first member, and freely contacting the surface of the workpiece, A second electrode extending in the predetermined direction, fixed to the second member, and freely in contact with the surface, In a predetermined view from the predetermined direction, the workpiece is provided with a support member that can abut against the back surface at at least one point on the perpendicular bisector of the line segment connecting the first electrode and the second electrode. A welding apparatus characterized by the following features.

2. The device includes a main body that detachably holds the aforementioned support member. The welding apparatus according to claim 1, characterized in that

3. A first actuator that biases the surface of the first electrode, A second actuator that biases the surface of the second electrode, The system includes a control unit that controls the first actuator and the second actuator. A welding apparatus according to claim 1 or 2, characterized in that

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

5. The first electrode and the second electrode are welding electrodes. The support member has an earth electrode that can abut against the back surface along the vertical bisector. A welding apparatus according to claim 1 or 2, characterized in that

6. Of the first electrode and the second electrode, one is a welding electrode and the other is a ground electrode. A welding apparatus according to claim 1 or 2, characterized in that

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