JPWO1996026036A1 - Seam welding method and seam welding device - Google Patents

Abstract

(57) [Summary] A pair of plate-shaped workpieces ( _12H , _12M) are conveyed by guide rollers (14) and guide members ( _18U , 18S ₎ and simultaneously positioned so that their mutual edge portions form a predetermined overlap (S), and are welded together at their edge portions by being sandwiched and crushed between a pair of roller electrodes ( _20U , _20S) while a welding current is passed between the roller electrodes ( _20U , 20S ₎ . Compared to using a clamping mechanism that holds the plate-shaped workpieces ( _12H , _12M) with upper and lower clamping members and moves them back and forth relative to the pair of roller electrodes ( _20U , _20S) , there is no need for a mechanism to move the upper and lower clamping members, which have been detached from the plate-shaped workpieces ( _12H , _12M) after welding, back to their original positions, and the seam welding apparatus does not become more complicated, resulting in a smaller size. Furthermore, compared to when the roller electrodes _20U , _20S are moved back and forth relative to the upper and lower clamp members, the reduction in productivity of seam welding caused by the movement of the roller electrodes _20U , _20S is eliminated, and therefore productivity of seam welding is improved.

Description

[Detailed Description of the Invention] Title of the Invention Seam Welding Method and Seam Welding Apparatus Technical Field The present invention relates to a seam welding method and seam welding apparatus in which the edges of two plate-shaped workpieces are overlapped, the overlapped portions are clamped between a pair of roller electrodes, or tightly clamped and crushed, and a welding current is passed between the pair of roller electrodes to continuously weld the overlapped portions.

BACKGROUND ART Seam welding, in which the edges of two plate-shaped workpieces are overlapped and then continuously welded by passing a welding current between a pair of roller electrodes while the overlapped portions are either clamped or tightly pressed together, is widely used in steel and automobile production lines due to its high speed and suitability for mass production.

In seam welding, the pressure applied by a pair of roller electrodes generates an expansion force at the overlapping portion of two plate-shaped workpieces, making it necessary to firmly hold the two plate-shaped workpieces so that the overlapping portions do not separate. This is particularly true in mash seam welding, in which a pair of roller electrodes tightly clamps the two plate-shaped workpieces together, crushing their edges while continuously welding them, because the expansion force that separates the overlapping portions of the two plate-shaped workpieces is large.

Therefore, in the past, for example, as shown in FIG. 10, two plate-shaped workpieces 12_H, 12_MThe upper and lower clamp members 120 of the clamp mechanism 122 are clamped and firmly held, and the upper and lower clamp members 120 are fixed to the pair of roller electrodes 20._U , 20_SWhile moving the two plate-shaped workpieces 12 relative to each other,_H, 12_MThe overlapping portions of the two sheets have been continuously seam-welded. For example, seam welding apparatuses such as those disclosed in Japanese Patent Laid-Open Publication Nos. 59-223179 and 61-52994 are known.

However, in the conventional seam welding apparatus described above, the clamp mechanism 122 is moved relative to the pair of roller electrodes _20U , _20S. Therefore, after welding is completed, the upper and lower clamp members 120 or the roller electrodes _20U , _20S must be removed from the plate-like workpieces _12H , _12M and moved back to their original positions. This movement mechanism has the disadvantage of making the seam welding apparatus complicated or large.

Furthermore, when the roller electrodes _20U , _20S are moved to their original positions, the adjustment must be interrupted, which reduces the productivity of the seam welding device.

The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a seam welding method and apparatus that enables continuous welding without moving the clamping mechanism and roller electrode relative to each other, and that is compact and highly productive.

DISCLOSURE OF THE INVENTION To achieve the above-mentioned objectives, the gist of the present invention is a seam welding method for continuously welding the edges of two plate-shaped workpieces by overlapping the edges of the two workpieces and sandwiching the overlapped portions between a pair of roller electrodes rotatable about two parallel axes. The method includes: (a) a moving step in which the two workpieces are moved in one direction toward the roller electrodes using multiple pairs of guide rollers that sandwich the two workpieces in their thickness direction; (b) a guiding step in which, as the two workpieces are moved in one direction by the moving step, the two workpieces are guided so that they are sandwiched between the pair of roller electrodes in an overlapping state with a predetermined overlap; and (c) a welding step in which a welding current is passed between the pair of roller electrodes to continuously weld the edges of the two workpieces sandwiched between the pair of roller electrodes.

In this manner, during the moving process, two plate-shaped workpieces sandwiched between pairs of guide rollers are moved in a direction perpendicular to the axis of the roller electrodes by the rotation of the guide rollers; during the guiding process, the two plate-shaped workpieces are guided so that the overlapping portions of the two plate-shaped workpieces are sandwiched between the pair of roller electrodes with a predetermined overlap; and during the welding process, a welding current is passed between the pair of roller electrodes, thereby continuously welding the edge portions of the two plate-shaped workpieces sandwiched between the pair of roller electrodes. Therefore, compared to using a clamping mechanism that holds a pair of plate-shaped workpieces with their edges overlapping each other and moves them relative to a pair of roller electrodes, the method of the present invention eliminates the need to move the upper and lower clamping members or roller electrodes back to their original positions after they are removed from the plate-shaped workpieces once welding is complete. This eliminates the need to make the seam welding equipment more complex, allowing for a smaller seam welding equipment and eliminating the reduction in seam welding productivity caused by the movement of the roller electrodes, thereby improving seam welding productivity.

Preferably, the guiding step guides the two plate-shaped workpieces by sliding the end faces of the overlapping edge portions of the two plate-shaped workpieces against a pair of guide surfaces provided on a fixed guide member upstream of the pair of roller electrodes and parallel to the axis of the roller electrodes in a direction perpendicular to the axis of the roller electrodes. This simple configuration improves the overlapping accuracy of the edge portions of the two plate-shaped workpieces.

Preferably, the guiding step uses at least two pairs of guide rollers positioned on either side of the guide member, each sandwiching the two plate-shaped workpieces in the thickness direction, to generate a component of force in a direction approaching the guide surface of the guide member in association with the transport of the two plate-shaped workpieces, thereby causing the end faces of the edge portions of the two plate-shaped workpieces to slide against the guide surface. In this way, the two plate-shaped workpieces are pressed against the guide surface of the guide member by at least two pairs of guide rollers as they move in their direction of movement, which has the advantage of reducing the number of sliding parts compared to when a guide plate is provided to press the plate-shaped workpieces against the guide surface of the guide member.

Preferably, the welding process involves a pair of roller electrodes rotatable about two parallel axes and biased toward each other, crushing the edges of two plate-shaped workpieces sandwiched between the pair of roller electrodes while welding them together. This eliminates the need for prior chamfering of the welded edges of the plate-shaped workpieces. Furthermore, in the case of so-called mash-type seam welding, a powerful clamping mechanism is required due to the large spreading force exerted on the two plate-shaped workpieces when clamped between the pair of roller electrodes, making the effects of the method of the present invention particularly pronounced.

Preferably, the method further includes a step of using two pairs of holding rollers, each provided at a lateral position of the pair of roller electrodes, to clamp the two plate-shaped workpieces in their thickness direction with a predetermined clamping pressure while their edges are being welded, thereby generating a frictional force that counteracts the spreading force of the two plate-shaped workpieces during the welding process, thereby preventing the two plate-shaped workpieces from spreading apart. In this way, the two plate-shaped workpieces are prevented from spreading apart during the welding process, thereby favorably improving the welding position accuracy.

Preferably, the method further includes a pressing step of pressing down the portion of the plate-shaped workpiece between the pair of roller electrodes and the holding roller in the axial direction of the roller electrodes where convex deformation occurs. This prevents the edges of the plate-shaped workpiece from shifting away from each other due to convex deformation of the plate-shaped workpiece, thereby advantageously preventing the molten zone formed between the roller electrodes from forming in both plate-shaped workpieces due to such shifting and thus reducing the welding strength.

Preferably, the method further includes a roller electrode rotation driving step of rotating the roller electrode so that a driving force in the direction of movement of the plate-shaped workpiece is transmitted from the roller electrode to the plate-shaped workpiece. In this way, the roller electrode is rotated so that the driving force for driving the plate-shaped workpiece is transmitted from the roller electrode to the plate-shaped workpiece. This suppresses the mutual spreading force between the pair of plate-shaped workpieces, thereby advantageously preventing the edge portions of the plate-shaped workpieces from shifting away from each other, making it difficult for the molten zone formed in the plate-shaped workpiece between the roller electrodes to form in both plate-shaped workpieces.

Preferably, the method further includes a cooling fluid supply step of supplying a cooling fluid to the portion of the plate-shaped workpiece that is being clamped by the roller electrodes to cool the portion of the plate-shaped workpiece that is heated by the seam welding with the roller electrodes. This suppresses the mutual spreading force between the pair of plate-shaped workpieces that is generated by the heat of the molten zone formed in the plate-shaped workpieces between the roller electrodes when current is passed between the roller electrodes, thereby advantageously preventing the molten zone formed in the plate-shaped workpieces between the roller electrodes from being difficult to form in both plate-shaped workpieces.

The gist of a seam welding apparatus for suitably implementing the above-mentioned method invention is a seam welding apparatus that overlaps the edges of two plate-shaped workpieces, sandwiches the overlapped portions between a pair of roller electrodes that can be rotated about parallel axes, and passes a welding current between the pair of roller electrodes to continuously weld the edges of the two plate-shaped workpieces. The seam welding apparatus comprises: (a) a pair of roller electrodes that can rotate about two parallel axes and are biased toward each other; and (b) a pair of roller electrodes positioned on both sides of the thickness direction of the two plate-shaped workpieces, respectively, and configured to weld the edges of the roller electrodes. (c) a drive unit that rotates at least some of the pairs of guide rollers in a predetermined direction, thereby moving the two plate-shaped workpieces in one direction while they are sandwiched between the guide rollers in the thickness direction; and (d) a guide unit that guides the two plate-shaped workpieces so that they are sandwiched between the pair of roller electrodes while overlapping each other with a predetermined overlap while the two plate-shaped workpieces are moved in one direction by the drive unit.

In this manner, as two plate-shaped workpieces sandwiched between pairs of holding rollers are rotated by a drive device and moved in a direction perpendicular to the axis of the roller electrodes, the guide device guides the two plate-shaped workpieces so that the overlapping portions of the two plate-shaped workpieces are sandwiched between the pair of roller electrodes. Thus, a welding current is passed between the pair of roller electrodes, continuously welding the edges of the two plate-shaped workpieces sandwiched between the pair of roller electrodes. Therefore, compared to a clamping mechanism that holds a pair of plate-shaped workpieces with their overlapping edges and moves them relative to the pair of roller electrodes, the present invention eliminates the need to move the upper and lower clamping members or roller electrodes back to their original positions after welding is complete. This reduces the complexity of the seam welding apparatus, thereby reducing the size of the seam welding apparatus and eliminating the productivity loss caused by roller electrode movement, thereby improving productivity.

Preferably, the guide device includes a guide member having a pair of parallel guide surfaces extending perpendicular to the axes of the pair of roller electrodes and fixed upstream of the roller electrodes, and the end faces of the overlapping edge portions of the two plate-shaped workpieces are brought into sliding contact with the guide surfaces of the guide member during the conveyance process to position the two plate-shaped workpieces relative to one another. This simple configuration improves the overlapping accuracy of the edge portions of the two plate-shaped workpieces.

Preferably, the guide device has at least two pairs of guide rollers positioned on either side of the guide member in the thickness direction to sandwich the two plate-shaped workpieces and guide the two plate-shaped workpieces in a direction that brings them closer to the roller electrodes and closer to the guide surface of the guide member, thereby causing the end faces of the edge portions of the two plate-shaped workpieces to slide against the guide surface. In this manner, the two plate-shaped workpieces are pressed against the guide surface of the guide member by at least two pairs of guide rollers as they move in the direction of movement, which has the advantage of reducing the sliding parts compared to when an inclined guide plate is provided to press the plate-shaped workpieces against the guide surface of the guide member.

Preferably, the pair of roller electrodes compresses the edges of the two plate-shaped workpieces sandwiched between them while welding the edges of the plate-shaped workpieces together. This eliminates the need for prior chamfering of the edges of the plate-shaped workpieces to be welded. Furthermore, in the case of so-called mash seam welding, a powerful clamping mechanism is required due to the large spreading force exerted on the two plate-shaped workpieces when clamped between the pair of roller electrodes, making the effects of the inventive device particularly pronounced.

Preferably, the welding system further includes two pairs of holding rollers, each rotatable about a pair of axes parallel to the axes of the pair of roller electrodes at positions to the sides of the pair of roller electrodes and sandwiching the two plate-shaped workpieces sandwiched between the pair of roller electrodes in the thickness direction, and a clamping force applying device that applies a clamping force to the two pairs of holding rollers sufficient to generate a frictional force sufficient to counteract the spreading force of the two plate-shaped workpieces generated during the welding process by the pair of roller electrodes. This prevents the two plate-shaped workpieces from spreading apart during the welding process, thereby favorably improving welding position accuracy.

Preferably, the method further includes a pressing device that pre-presses the area of the plate-shaped workpiece where convex deformation is expected to occur in order to prevent convex deformation of the plate-shaped workpiece between the roller electrode and the holding roller in the axial direction of the roller electrode. This prevents the edges of the plate-shaped workpiece from shifting away from each other due to convex deformation of the plate-shaped workpiece, thereby advantageously preventing the molten zone formed in the plate-shaped workpiece between the roller electrodes from being difficult to form in both plate-shaped workpieces due to such shifting.

Preferably, the pressing device further comprises an auxiliary roller rotatably disposed between the roller electrode and the holding roller in the axial direction of the roller electrode around an axis parallel to the axial direction of the roller electrode, allowing the plate-shaped workpiece to move in the moving direction while pre-pressing the portion of the plate-shaped workpiece where convex deformation is expected to occur, or an auxiliary skid disposed between the roller electrode and the holding roller in the axial direction of the roller electrode and in sliding contact with the plate-shaped workpiece.

Preferably, the apparatus further includes a roller electrode rotation drive device that rotates the roller electrode so that a driving force in the direction of movement is transmitted from the roller electrode to the plate-shaped workpiece. In this way, the roller electrode is rotated so that the driving force for driving the plate-shaped workpiece is transmitted from the roller electrode to the plate-shaped workpiece. This suppresses the mutual spreading force between the pair of plate-shaped workpieces, thereby advantageously preventing the edge portions of the plate-shaped workpieces from shifting away from each other, making it difficult for the molten zone formed between the roller electrodes to form within the two plate-shaped workpieces.

Preferably, the welding system further includes a cooling fluid supply device that supplies a cooling fluid to the portion of the plate-shaped workpiece that is being clamped by the roller electrodes to cool the portion of the plate-shaped workpiece that is heated by the seam welding with the roller electrodes. This configuration effectively prevents the mutual spreading force of the pair of plate-shaped workpieces, which is generated by the heat of the molten zone formed in the plate-shaped workpieces between the roller electrodes when current is passed between them, by supplying the cooling fluid. This advantageously prevents the molten zone formed in the plate-shaped workpieces between the roller electrodes from being difficult to form in both plate-shaped workpieces.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a schematic diagram of the conveyance process of a plate-shaped workpiece for explaining the seam welding method of the present invention.

FIG. 2 is a plan view illustrating the arrangement of guide rollers and holding rollers involved in the transport of a plate-shaped workpiece to explain the seam welding method of the embodiment of FIG.

FIG. 3 is a diagram showing the essential parts of the guide member with which the plate-shaped workpiece slides, in order to explain the guiding process in the embodiment of FIG.

FIG. 4 is a diagram illustrating the guiding and holding functions of the guide rollers and the holding rollers used in the guiding and holding steps of the embodiment of FIG.

FIG. 5 is a diagram illustrating the relationship between the spreading force generated in the welding process of the embodiment of FIG. 1 and the position from the roller electrode.

FIG. 6 is a diagram illustrating the relationship between the spreading force generated in the welding process of the embodiment of FIG. 1 and the thickness of the plate-like workpiece clamped by the roller electrodes.

FIG. 7 shows a seam welding apparatus for suitably implementing the seam welding method of FIG. 1, illustrating a cross section perpendicular to the conveyance direction of the plate-shaped workpiece near the guide roller.

FIG. 8 is an enlarged view showing a main part of the seam welding apparatus of FIG.

FIG. 9 is a partially cutaway view illustrating the vicinity of the roller electrode of the seam welding apparatus of FIG.

FIG. 10 is a perspective view illustrating a process of a conventional seam welding method using a clamping mechanism that secures a pair of plate-shaped workpieces together.

FIG. 11 is a diagram illustrating a convex deformation F of a plate-shaped workpiece that may occur during seam welding.

FIG. 12 is a diagram illustrating the relationship between the convex deformation F shown in FIG. 11 and the distance between the roller electrode and the pressure roller.

FIG. 13 is a diagram illustrating a seam welding state when the convex deformation F shown in FIG. 11 does not occur.

FIG. 14 is a diagram illustrating the state of seam welding when the convex deformation F shown in FIG. 11 occurs.

FIG. 15 is a diagram illustrating the vicinity of a roller electrode and a retaining roller in another embodiment of the present invention.

FIG. 16 is a diagram illustrating the arrangement of the auxiliary rollers in the embodiment of FIG.

FIG. 17 is a diagram illustrating the prevention of convex deformation F by the auxiliary roller in the embodiment of FIG. 15.

FIG. 18 is a view illustrating the vicinity of a roller electrode and a support roller in another embodiment of the present invention, and corresponds to FIG. 15.

FIG. 19 is a side view of the auxiliary skid of the embodiment of FIG.

FIG. 20 is a diagram illustrating a roller electrode according to another embodiment of the present invention.

FIG. 21 is a diagram for explaining the function of the roller electrode of the embodiment of FIG.

FIG. 22 is a diagram for explaining the function of the roller electrode of the embodiment of FIG.

FIG. 23 is a diagram illustrating the configuration of the roller electrode and its vicinity in another embodiment of the present invention.

FIG. 24 is a perspective view showing the general configuration of a seam welding apparatus according to another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION An application example of the present invention will now be described in detail with reference to the drawings. Figures 1 through 4 illustrate the implementation of the seam welding method of the present invention, and Figures 5 through 7 illustrate a seam welding apparatus 10 for implementing the seam welding method.

1 and 2 , a pair of left and right plate-shaped workpieces _12H and _12M separated in a predetermined shape from a plate material such as a zinc steel plate are conveyed in a predetermined conveying direction B by a plurality of sets of guide rollers 14 (conveying process). During this conveying process, the workpieces are guided in sliding contact with guide surfaces _24U , _24S of a pair of upper and lower plate-shaped guide members _18U , _18S , whereby their edge portions are relatively positioned so as to overlap with each other with a predetermined overlap (overlapping width) S (guiding process). Then, in a state where the edge portions of the positioned pair of plate-shaped workpieces _12H and _12M are sandwiched and pressed between a pair of upper and lower roller electrodes _20U , _20S , a current supplied from a power source 22 is passed between the pair of roller electrodes _20U , _20S , whereby the workpieces are seam-welded to each other along a welding center line A that is parallel to the conveying direction B and passes through the center of the width of the overlapping width S of the overlapping portions of the edge portions of the pair of plate-shaped workpieces _12H and _12M (welding process). A pair of holding rollers 16 located on the sides of the roller electrodes _20U , _20S holds the pair of plate-shaped workpieces _12H and _12M during welding with a predetermined clamping pressure in the thickness direction, thereby preventing the plate-shaped workpieces _12H and _12M from spreading apart (holding process).

The pair of guide rollers 14 guides one plate-shaped workpiece 12_HA pair of upper and lower guide rollers 14 grips the sheet in the thickness direction with a predetermined gripping force._HUand 14_HSand the other plate-shaped workpiece 12_MA pair of upper and lower guide rollers 14 grips the sheet in the thickness direction._MUand 14_{M S} A plurality of sets are arranged along the conveying direction B, and at least one set is rotated._HU, 14_HS, 14_MU , 14_MSA pair of horizontal rotation axes C located above and below the welding center line A are in a plane that forms a predetermined angle θ with a plane perpendicular to the welding center line A.₁A pair of upper and lower guide rollers 14 are supported rotatably around the guide rollers 14._HUand 14_HS, 14_MUand 14_MSA pair of plate-shaped workpieces 12 being transported_Hand 12_Mand guide them through the guide member 18_U, 18_S The component of force (for example, F_FR1) is generated, for example, by a cylinder device 56 described later._H, 56_Mare given in the direction of approaching each other.

The set of holding rollers 16 also includes a roller electrode 20_U, 20_SOne plate-shaped workpiece 12 is located on one side of the_HA pair of upper and lower holding rollers 16 holds the sheet in its thickness direction with a predetermined gripping force._HUand 16_HSand roller electrode 20_U, 20_SThe other plate-shaped workpiece 12 is located on the other side of the_MA pair of upper and lower holding rollers 16 hold the sheet in its thickness direction._MUand 16_MSand a roller electrode 20_U, 20_SThe pair of upper and lower holding rollers 16 are arranged to sandwich the rollers 16 from the sides._HUand 16_HS , 16_MUand 16_MSA pair of plate-shaped workpieces 12 being welded_Hand 12_MA relatively large pressing force is applied to prevent the edges of the cylinder 56 from expanding apart from each other, for example, as described below._H, 56_MThe holding rollers 16 are respectively applied in a direction approaching each other by a cylinder device similar to that of the holding rollers 16._HU, 16_HS, 1 6_MU, 16_MSare a pair of horizontal rotation axes C located above and below the welding center line A in a plane perpendicular to the welding center line A.₂The plate-shaped workpiece 12 is supported rotatably around the workpiece 12, and the pressing force is applied to the workpiece 12 during transportation, i.e., welding._Hand 12_MBy holding the edges together, the edges are prevented from spreading (holding process).

The pair of roller electrodes 20_U, 20_SA pair of horizontal rotation axes C are located above and below the weld center line A in a plane perpendicular to the weld center line A.₃The pair of roller electrodes 20 are supported so as to be rotatable._U, 20_S is a plate-shaped workpiece 12_Hand 12_MThe overlapping edge portions of the plate-shaped workpiece 12 are, for example,_Hor 12_MA relatively large pressing force is applied by, for example, a cylinder device 80 (described later) in a direction in which the roller electrodes 20 approach each other, so that the thickness of the roller electrodes 20 approaches the thickness of the roller electrodes 20._U, 20_SThe pressed portion P is shown.

The plate-shaped guide member 18_U, 18_SAs shown in detail in FIG. 3, the guide rollers 14 are arranged in a pair of upper and lower guide rollers 14 with a predetermined gap between their opposing surfaces._HUand 14_HSand the other plate-shaped workpiece 12_MA pair of upper and lower guide rollers 14 grip the_Muand 14_MSA pair of roller electrodes 20 are welded along the welding center line A between_U, 20_SThe upper guide member 18 is provided close to the upper guide member 18 at a predetermined distance from the upper guide member 18._UThe plate-shaped workpiece 12 facing the_MThe side portion is provided with a plate-shaped workpiece 12._HThe guide surface 24 is brought into sliding contact with the edge of the_UThe protrusion 26 has_Uis formed, and the lower guide member 18_S Plate-shaped workpiece 12 on the opposing surface_HThe side portion is provided with a plate-shaped workpiece 12._MThe guide surface 24 is brought into sliding contact with the edge of the_SThe protrusion 26 has_Sis formed.

As shown in detail in FIG. 4 , at least some (all in this embodiment) of the guide rollers 14 located on both the left and right sides of the guide members 18 _U and 18 _S are configured so that their rotation axes C ₁ are inclined at a predetermined small angle θ (1 to 3° in this embodiment) with respect to the conveying direction B with respect to a line perpendicular to the welding center line A, thereby driving or guiding the plate-shaped workpieces 12 _H and 12 _M in a direction inclined inward at the predetermined small angle θ with respect to the conveying direction B (the direction of a driving force F _R described later).

As a result, when, for example, the plate-shaped workpiece _12M is in contact with the guide surface _24S , the guide roller _14MU generates a component force F _R1 in a direction perpendicular to the conveying direction B and directed toward the welding center line A, i.e., the guide surface _24S , and a component force F _R2 in a direction parallel to the conveying direction _B , based on the driving force F _R. Therefore, the plate-shaped workpiece _12M is conveyed while being pressed against the guide surface _24S , and the plate-shaped workpiece _12H is also conveyed while being pressed against the guide surface _{24U .} Therefore, the pair of plate-shaped workpieces _12H and _12M are positioned relative to each other so that the overlap width of their edge portions becomes a predetermined overlap width S before they are clamped between the pair of upper and lower roller electrodes 20U and 20S. Therefore, even if the pair of plate-shaped workpieces _12H and _12M are set on the conveying path with their relative positions disturbed, their relative positions are automatically determined during conveyance.

Incidentally, the pair of upper and lower roller electrodes 20_Uand 20_STwo plate-shaped workpieces 12_Hand 12_MWhen the overlapping edge portions of the plate-shaped workpieces 12 are pinched or crushed,_Hand 12_MAs shown by line L in FIG. 4, this spreading force acts from the upstream side of the roller electrode 20 in the conveying direction B to the downstream side of the roller electrode 20._Uand 20_SThe closer to the roller electrode 20_Uand 20_S The pressure is maximum at the lateral position. Meanwhile, the holding roller 16 holds the plate-shaped workpiece 12 with a predetermined clamping pressure._Hand 12_MSince the plate-shaped workpiece 12 is clamped,_Hand 12_MAs a reaction force to the spreading force, an inward frictional force corresponding to the clamping force of the holding rollers 16 acts on the sheet.

Therefore, the pair of plate-shaped workpieces 12_Hand 12_MIn order to prevent the spreading of the guide member 18, the friction force should be made equal to or greater than the spreading force._U, 18_S From the guide roller 14 on the side of the guide member 18_U, 18_SComponent force F towards_R1is acting, the friction force F required at this position is_F1is the spreading force F_E1From the above component force F_R1or more (F_F1≧F_E1-F_R1On the other hand, the plate-shaped workpiece 12_H and 12_MAmong these, the roller electrode 20_Uand 20_SSince the portion held by the holding roller 16 located to the side of the_F2is the spreading force F_E2Equal to or higher than (F_F2≧F_E2)

That is, to prevent the pair of plate-shaped workpieces _12H and _12M from spreading, the frictional forces F _F1 and F _F2 , i.e., the clamping forces of the holding rollers 16, are set so as to satisfy the relationship F _F1 ≥ _{F E1} - F _R1 on the sides of the guide members 18U and _18S , and so as to satisfy the relationship F _F2 ≥ F _E2 on the sides of the roller electrodes _20U and _20S . In this embodiment, the rotational axis _C2 of the holding roller 16 is perpendicular to the conveying direction, i.e., the welding direction B, and its guiding direction is parallel to the conveying direction B, because considering only the frictional forces makes it easier to control the overlap S in a stable manner.

Figure 5 shows the effect of plate thickness t on the distribution of spreading force, and Figure 6 shows the effect of t on the maximum spreading force at the sides of roller electrodes _20U , _20S . For example, for general-purpose steel plates used in automobile manufacturing up to a plate thickness t = 1.0 mm, the spreading force becomes zero at a position 150 mm before roller electrodes _20U , _20S (Figure 5). Therefore, upstream of that position, the clamping force of retaining rollers 16 can be set to a level that applies a driving force to the pair of plate-shaped workpieces _12H and _12M . Furthermore, since the maximum spreading force at the sides of roller electrodes _20U , _20S increases linearly with increasing plate thickness (Figure 6), the clamping force of retaining rollers 16 is automatically determined once the plate thickness is determined.

A mash seam welding apparatus 10 for carrying out the above-described mash seam welding method is configured, for example, as shown in Figures 7 to 9. Figure 7 is a cross section perpendicular to the conveyance direction B, illustrating the configuration in the vicinity of the guide roller 14 of the mash seam welding apparatus 10, Figure 8 is an enlarged view of the configuration in the vicinity of the guide roller 14, and Figure 9 is a partially cutaway view illustrating the support structure for the roller electrode _20U .

The guide rollers 14 and the support rollers 16 are basically constructed in the same manner, and therefore, the following description will focus on the guide roller 14 as a representative example, and will explain their construction and supporting structure.

7 and 8 , guide rollers _14HS , _14MS are provided via base blocks _53H , _53M on the upper end surfaces of a pair of support pillars _52H , 52M erected from a base frame 50 extending in the welding direction B. Furthermore, a pair of left and right cylinder devices 56H, _56M are fixed to an erection frame 55 fixed to the base frame 50 via an outer frame 54 for applying clamping pressure to the pair of upper and lower guide rollers _14HU , _14HS or _14MU , _14MS , respectively, _and movable plates _60H , _60M , on which the guide rollers _14HU , _14MU are provided, are fixed to the tips of extension rods _58H , _{58M that} extend extendably and contractibly downward from the cylinder devices _56H , _56M .

Each set of guide rollers 14 _HS , 14 _MS , 14 _HU , 14 _MU integrally includes a shaft 66 supported by shaft cases 62 _HS , 62 _MS , 62 _HU , 62 _MU via bearings 64, and the shaft cases 62 _HS , 62 _MS are fixed to the upper end surfaces of the supports 52 _H , 52 _M , and the shaft cases 62 _HU , 62 _MU are fixed to the movable plates 60 _H , 60 _M , so that the rollers are rotatable about a pair of rotation axes _C1 located above and below the welding center line A in a plane perpendicular to the welding center line A. As shown in FIG. 3, the guide members _18U and _18S are fixed to the cylinder device _56H and the support column _52M , respectively, with a predetermined gap between their opposing surfaces, so that the welding center line A is positioned at the center in the width direction of the opposing surfaces between the pair of upper and lower guide rollers _14HU and _14MS and the pair of upper and lower guide rollers _14MU and _14MS that grip the other plate-shaped workpiece _12M .

The shafts 66 of the lower guide rollers _14HS , _14MS are each connected to a drive motor 76 via a pair of joints 68, 70, an intermediate shaft 72, and a chain 74. An intermediate shaft 72 is provided for each of the left and right guide rollers _14HS , _14MS in one set of guide rollers 14, and these are connected to the drive motor 76 via the chain so that they can rotate at the same speed. As a result, the lower guide rollers _14HS , _14MS of each set of guide rollers 14 are rotated by the drive motor 76, and the pair of plate-shaped workpieces _12H and _12M are conveyed. In this embodiment, the drive motor 76 functions as a drive device that rotates the guide rollers 14 or the holding rollers 16.

The pairs of upper and lower guide rollers 14 _HU and 14 _HS , 14 _MU and 14 _MS are steel rollers whose outer surfaces are covered with an elastic material such as urethane rubber, and a clamping force sufficient to transport the pair of plate-shaped workpieces 12 _H and 12 _M being transported and generate a component force directing them toward the guide members 18 _U and 18 _S is applied to the guide rollers 14 _HU and 14 _HS , 14 _MU and 14 _MS in directions that bring them closer to each other by cylinder devices 56 _H and 56 M that function as clamping force applying _devices .

The pair of upper and lower holding rollers 16 that constitute one set of holding rollers 16_HUand 16_HS , 16_MUand 16_MSAs shown in FIG. 15, which will be described later, the guide roller 14_HUand 14_HS , 14_MUand 14_MSand the rotation axis C₂and the guide roller 14 is rotatably mounted around the guide roller 14._HS, 14_MSThe pair of upper and lower holding rollers 16 are rotated by a drive motor 76 so as to have a peripheral speed similar to that of the pair of upper and lower holding rollers 16._HUand 16_HS, 16_MUand 16_MS, the plate-shaped workpiece 12_Hand 12_MA steel roller with a knurled outer surface to increase the frictional force in the direction of the rotation axis against a pair of plate-shaped workpieces 12 during welding._Hand 12_MThe frictional force of each holding roller 16 is such that the edge portions of the holding rollers 16 cannot be spread apart from each other._HS, 16_MS, 16_HU, 16_MUThe relatively large clamping force to be generated on the outer peripheral surface of the cylinder device 56 functions as a clamping force applying device._H, 56_MThe holding roller 16 is held by a cylinder device similar to that_HSand 16_HU , 16_MSand 16_MUare given in directions approaching each other.

Since the pair of roller electrodes _20U , _20S have the same configuration as each other, as shown in Fig. 15 described below, the upper roller electrode _20U will be described using Fig. 9. Fig. 9 shows the upper roller electrode _20U and its support structure with a portion cut away. In Fig. 9, in order to apply a clamping pressure to the roller electrodes _20U , _20S , a cylinder device _80U equipped with an extendable rod _82U that protrudes extendably downward is fixed to the installation frame 55, and a support block _86U that rotatably supports the roller electrode _20U is fixed to a movable plate ₈₄ fixed to the tip of the extendable rod 82U.

Roller electrode 20_UThe flange portion 88 is located at the middle of the axial direction._UA rotating shaft 90 integrally having_Uand the flange portion 88_UThe clamping plate 92_UWith the screws 94_U Circular electrode plate 96 fastened by_Uand its rotation axis 90_UBoth ends of the power supply bush 98_Uvia the support block 86_Uthrough hole 100 formed in_U By fitting into the support block 86_UThe electrode plate 96 is rotatably supported by the_Uis a good electrical conductor and the plate-shaped workpiece 12_H, 12_MThe rotating shaft 90 is made of a metal material such as chrome steel, beryllium copper alloy, or chrome zirconium copper alloy, which has durability such as low wear even when a relatively large current is passed through it while in contact with the rotating shaft 90._U, clamping plate 92_U, power supply bush 9 8_U, and support block 86_UThe power supply 22 is connected to the support block 86 via an electric wire (not shown)._U, power supply bush 98, rotating shaft 90_Uetc. via electrode plate 96_UThe current is supplied to the

A flow passage 102U is formed within the rotating shaft _90U , communicating from one end face to the other end face, with the intermediate portion of the flow path being exposed in an arc shape at the contact surface between the flange portion _88U and the electrode plate _96U. A pair of hose connection devices _108U , _110U are attached to the end faces of the rotating shaft _90U , which connect the flow passage _102U to _{hoses 104U} , _106U that guide the cooling fluid while allowing the rotating shaft _90U to rotate.

In the mash seam welding apparatus 10 configured as described above, when the drive motor 76 continuously rotates the plurality of guide rollers 14 and the one set of holding rollers 16, the pair of plate-shaped workpieces 12_H, 12_MAs previously mentioned, the guide rollers 14 and guide members 18_U, 18_UThe electrodes are conveyed by the pair of roller electrodes 20, and at the same time, the edges of the electrodes are positioned so that the predetermined overlap width S is reached._U , 20_SThe roller electrodes 20 are pinched and crushed by the_U, 20_SBy passing a welding current between the pair of plate-shaped workpieces 12, their edges are welded together, as shown in FIG. 13, which will be described later. Therefore, according to this embodiment, for example, a pair of plate-shaped workpieces 12, as shown in FIG._H, 12_MThe pair of roller electrodes 20 are held by upper and lower clamp members 120 with their edge portions overlapping each other._U, 20_SCompared to using a clamping mechanism 122 that reciprocates relative to the plate-shaped workpiece 12 after welding is completed,_H, 12_MSince there is no need for a mechanism for moving the upper and lower clamp members 120 released from the roller electrode 20 back to their original positions, the seam welding device does not become complicated, and the seam welding device can be made compact._U, 20_SThe roller electrode 20 is moved back and forth relative to the upper and lower clamp members 120._U, 20_SThis eliminates the problem of reduced productivity in seam welding due to movement of the welding rod, thereby increasing productivity in seam welding.

Furthermore, according to this embodiment, guide members _18U , _18S are provided which have a pair of guide surfaces _24U , _24S which are arranged parallel to the axis of the pair of roller electrodes _20U , _20S and which are fixed upstream of the roller electrodes _20U , _20S , and during the conveying process, the end faces of the overlapping edge portions of the two plate-shaped workpieces _12H , _12M are brought into sliding contact with the guide surfaces _24U , _24S of the guide members _18U , _18S , respectively, so that the two plate-shaped workpieces _12H , _12M are positioned relative to one another, thereby improving the overlapping accuracy of the edge portions of the two plate-shaped workpieces _12H , _12M with a simple configuration.

Furthermore, according to this embodiment, the guide member 18_U, 18_STwo plate-shaped workpieces 12 are positioned on both sides of the thickness direction of the_H, 12_Mare sandwiched in the thickness direction, and the two plate-shaped workpieces 12_H, 12_Mroller electrode 20_U, 20_SThe closer to the guide member 18_U, 18_SGuide surface 24_U, 24_SBy guiding the workpieces in a direction approaching each other, the two workpieces 12_H, 12_MThe end surface of the edge of the guide surface 24_U, 24_SAt least two pairs of guide rollers 14 that slide against the_HUand 14_HS, 14_MUand 14_MSTherefore, the two pairs of guide rollers 14_HUand 14_HS, 14_MUand 14_MSTwo plate-shaped workpieces 12_H, 12_MAs the guide member 18 moves in the moving direction,_U, 18_SGuide surface 24_U, 24_SSince the plate-shaped workpiece 12 is pressed against the_H , 12_MThe guide member 18_U, 18_SGuide surface 24_U, 24_SThis has the advantage of reducing the number of sliding parts compared to when using guide plates, etc.

Furthermore, according to this embodiment, the pair of roller electrodes _20U , _20S welds the edge portions of the two plate-shaped workpieces _12H , _12M to each other while crushing the edge portions of the two plate-shaped workpieces _12H , _12M sandwiched between them, so there is no need to previously perform chamfering or the like on the welded surfaces of the edge portions of the plate-shaped workpieces _12H , _12M . Furthermore, in the case of such so-called mash-type seam welding, a powerful clamping mechanism was required because the spreading force of the two plate-shaped workpieces _12H , _12M when clamped between the pair of roller electrodes _20U , _20S was large, so this has the advantage of making the device even more compact.

In this embodiment, a pair of roller electrodes 20_U, 20_SAt the lateral position of the pair of roller electrodes 20_U, 20_SThe pair of roller electrodes 20 are provided so as to be rotatable about a pair of axes parallel to the axis of the roller electrodes 20._U, 20_STwo plate-shaped workpieces 12 sandwiched between_H, 12_MTwo pairs of holding rollers 16 sandwich the sheet in the thickness direction._HUand 16_HS , and 16_MUand 16_MSand the two pairs of holding rollers 16_HUand 16_HS, and 16_MU and 16_MSOn the other hand, a pair of roller electrodes 20_U, 20_STwo plate-shaped workpieces 12 generated during the welding process_H, 12_MThe clamping force applying device (cylinder device) is further provided to apply a clamping force of a magnitude sufficient to generate a frictional force sufficient to counter the spreading force of the two plate-shaped workpieces 12 during the welding process._H, 12_M This prevents the gap from widening, thereby effectively improving welding position accuracy.

Next, another embodiment of the present invention will be described. In the following description, parts common to the above embodiment will be designated by the same reference numerals and will not be described again.

In the above-described embodiment, buckling of the plate-shaped workpieces _12H , _12M , i.e., convex deformation F, may occur between the roller electrodes _20U , _20S and the two pairs of holding rollers _16HU and _16HS or _16MU and _16MS in the axial direction of the roller electrodes _20U , _20S due to the spreading force of the plate-shaped workpieces _12H , _12M , as shown in Fig. 11. Such convex deformation F is more likely to occur as the thickness of the plate-shaped workpieces _12H , _12M becomes thinner, but as shown in Fig. 12, the closer the two pairs of holding rollers _16HU and _16HS , and _16MU and _16MS are arranged to the roller electrodes _20U , _20S , the less likely it is to occur. Therefore, it is desirable to arrange the two pairs of holding rollers _16HU and _16HS , and _16MU and _16MS as close to the roller electrodes _20U , _20S as possible. When the convex deformation F does not occur, the edge portions of the plate-shaped workpieces _12H and _12M are suitably crushed, forming a gently inclined boundary surface G, as shown in Fig. 13, and as a result, a molten zone (nugget) N due to the welding current is formed near the boundary surface G, which is midway between the electrode plates _96U and _96S and has a high resistance, but when the convex deformation F occurs, the edge portions of the plate-shaped workpieces _12H and _12M move to the left and right, increasing the inclination of the boundary surface G, and at the same time, the plate-shaped workpieces _12H and _12M come into contact with the electrode plates _96U and _96S , respectively, as shown in Fig. 14, making it difficult to form a molten zone N and making seam welding difficult. The dashed arrows in Figs. 13 and 14 indicate the welding current.

However, not only are there support blocks 86 and the like near the roller electrodes _20U , _20S to support them, but as the roller electrodes _20U , _20S reduce in diameter due to wear, the support blocks _86U , _86S move closer to the plate-shaped workpieces _12H , _12M as shown by the dashed lines in Figure 15. As a result, the roller electrodes 20U, 20S cannot be brought closer than a predetermined distance D to the roller electrodes _20U , _20S , and depending on the thickness of the plate-shaped workpieces _12H , _12M , it may not be possible to prevent the above-mentioned convex deformation F from occurring.

Fig. 15 shows an embodiment in which a pressing device is provided to prevent the occurrence of the convex deformation F. In Fig. 15, in the direction perpendicular to the conveying direction B, i.e., in the direction of the rotation axis, auxiliary rollers _130HU , 130MS, _130MU , 130MS for preventing _{the convex deformation F of the plate-like workpieces 12H, 12M are provided between the roller electrodes 20U, 20S and the pair of holding rollers 16HU and 16HS , and between the} roller electrodes _20U , _20S and the _pair of holding rollers _16MU and _16MS , at positions where they press the areas where the convex deformation F is expected to occur. That is, the auxiliary rollers _130HS and _130MS located below the plate-shaped workpieces _12H , _12M are rotatably supported at the tip ends of brackets _132HS and _132MS fixed to the base blocks _53H , _53M , and the auxiliary rollers _130HU and _130MU located above the plate _- shaped workpieces _12H , 12M are rotatably supported at the tip ends of brackets _132HU and _132MU fixed to the movable plates _60H , _60M . The auxiliary rollers _130HU , _130HS , _130MU , and _130MS are rotatable about axes C4 that are parallel to the rotation axes _C3 of the roller electrodes _20U , _20S and the rotation axes _C2 of the pair of holding rollers _16HU and _16HS , and the lateral positions of the roller electrodes _20U , _20S on the plate-like workpieces _12H , _12M are pressed with a predetermined clamping pressure _by the pairs of upper and lower auxiliary rollers _130HU and _130HS , and _130MU and _130MS, respectively.

16 , each of the auxiliary rollers _130HU , _130HS , _130MU , _130MS is composed of three rollers connected in series along _{the conveying direction B at the tip of the bracket 132HU, 132MU, 132HS , 132MS so} as to be able to sufficiently press the convex deformation F of the plate-shaped workpieces _12H , _12M formed along the conveying direction B. Furthermore, each of the auxiliary rollers 130HU, _130HS , _130MU , _130MS has a smaller _diameter than the distance between the tip of the support blocks _{86U, 86S (shown by dashed lines) of the roller electrodes 20U , 20S in} their maximum wear state and _the plate-shaped workpieces _12H , _{12M ,} so that the auxiliary rollers can approach _the roller _{electrodes 20U} , _20S sufficiently. 16 is a view of brackets 132 _HU and 132 _HS located on the left side in the conveying direction B and the auxiliary rollers 130 _HU and 130 _HS rotatably supported thereby, viewed from the roller electrodes 20 _U and 20 _S. In this embodiment, the auxiliary rollers 130 _HU , 130 _HS , 130 _MU , and 130 _MS and the brackets 132 _HU , 132 _MU , 132 _HS , and 132 _MS that support them function as pressing devices to prevent the occurrence of convex deformation F.

According to this embodiment, the roller electrode 20_U, 20_SRoller electrode 2 in the axial direction of_U, 20_Sand holding roller 16_HU, 16_HSand the roller electrode 20_U, 20_S and holding roller 16_MU, 16_MSThe plate-shaped workpiece 12 between_H, 12_MIn order to prevent the convex deformation F, an auxiliary roller 130 is provided as a pressing device._HU, 130_HS, 130_MU , 130_MS, and a bracket 132 supporting them._HU, 132_MU, 132_HS , 132_MSAs a result, the portions where the convex deformation F is expected to occur are pressed (pressing process), and the plate-shaped workpiece 12_H, 12_MEven if the plate thickness is thin, as shown in FIG. 17, the convex deformation F indicated by the dashed line is prevented, and the resulting deformation of the plate-shaped workpiece 12 is prevented._H, 12_MThe edge portions of the roller electrode 20 are displaced in the direction away from each other, and the roller electrode 20 is displaced in the direction away from each other._U, 20_SPlate-shaped workpiece 12_H, 12_MThis advantageously prevents the fusion zone N formed within the mold from being not formed.

In the embodiment shown in Figure 18, instead of the auxiliary rollers _130HU , _130HS , _130MU , and _130MS of the embodiment shown in Figure 15 above, auxiliary skids _134HU , _134HS , _134MU , and _134MS that slide against the plate-like workpieces _12H and _12M are provided at the tip ends of the brackets _132HU , _132HS , _132MU , and _132MS . The auxiliary skids _134HU , _134HS , _134MU , _134MS have a height dimension smaller than the distance between the tips (indicated by dashed lines) of the support blocks _86U , _86S of the roller electrodes _20U , _20S in their maximum wear state and the plate-shaped workpieces _12H , _12M , and are therefore positioned between the tips of the roller electrodes _20U , _20S and the plate-shaped workpieces _12H , _12M , pressing the plate-shaped workpieces _12H , _12M from both sides at positions similar to those pressed by the auxiliary rollers _130HU , _130HS , _130MU , _130MS , as shown in Figure 19. The auxiliary skids _134HU , _134HS , _134MU , _134MS are preferably made of a material with high wear resistance and low friction resistance, such as molybdenum disulfide or carbon-impregnated sintered metal. This embodiment also provides the same effects as the embodiment of Fig. 15. Fig. 19 is a view of the right-side auxiliary skids _134MU and _134MS and the roller electrodes _20U and _20S viewed from the right side in the conveyance direction.

Fig. 20 shows another embodiment of the present invention, a roller electrode _20U that is rotationally driven by an electric motor 140. In Fig. 20, a clamping plate 92U for clamping a circular electrode plate _96U between it and a flange portion _88U of a rotating shaft _90U is formed with outer peripheral teeth ₁₄₂ , and an intermediate gear 144 that meshes with the outer peripheral teeth 142 is rotatably mounted on a support block _86U . An electric motor 140 having an output gear 146 that meshes with the clamping plate _92U via the intermediate gear 144 is fixed to the support block _86U . The electric motor 140 rotationally drives the roller electrode _20U so that the outer peripheral speed of the roller electrode _20U is higher than the conveying speed when the roller electrode _20U is not in contact with the plate-like workpiece _12H , thereby transmitting a driving force in the movement direction from the roller electrode _20U to the plate-like workpiece _12H when the roller electrode _20U is in contact with the plate-like workpiece _12H . 20, the area around the electric motor 140 and the intermediate gear 144 is shown developed around the rotation axis of the intermediate gear 144.

Here, during seam welding, the roller electrode 20_U, 20_SA pair of plate-shaped workpieces 12_H, 12_MWhen the edge of the plate-shaped workpiece 12 is clamped, for example, as shown by the arrow in FIG._H, 12_MThe spreading force acting on the roller electrode 20_U, 20_SThe force is generated radially from the pinch point, but the spreading force is_U, 20_SIt is believed that the force component toward the unwelded portion (toward the welding end point) behind (upstream of) the roller electrode 20 has the greatest influence._UPlate-shaped workpiece 12_HThe roller electrode 20 is driven by the electric motor 140 so that a driving force in the direction of movement of the umbilicus is transmitted._Uis rotated (roller electrode rotation drive process), so the roller electrode 20_UThe pushing force, i.e., the driving force F_D is generated as shown in Figure 21 or Figure 22. Therefore, the driving force F_Dand a force having a directional component toward the unwelded portion, for example, F_PThe resultant force F_TAs shown in FIG. 22, a force having a directional component toward the unwelded portion, such as F_Pis a force (F) with a directional component toward the weld completion part._THowever, the completed welded portion is a pair of plate-shaped workpieces 12._H, 12_Mare mutually connected parts, so the above force F_TTherefore, the spreading force in the direction of the welding end point is suppressed, and the plate-shaped workpiece 12_H, 12_MAs a result, according to this embodiment, the pair of plate-shaped workpieces 12 can be prevented from buckling, i.e., from occurring as a convex deformation F._H, 1 2_MSince the mutual spreading force between the plate-shaped workpieces 12 is suppressed,_H, 12_MThe roller electrode 20 is caused by the edge portions of the roller electrode 20 being displaced away from each other._U, 20_SPlate-shaped workpiece 12_H, 12_MThis has the advantage that the fusion zone formed within the workpiece is suitably prevented from shifting from the boundary between the two plate-shaped workpieces.

Figure 23 is a conceptual diagram showing the main components of a seam welding apparatus according to another embodiment of the present invention. In Figure 23, a cooling fluid supply device 150 is composed of a cooling fluid supply source 152 and a spray nozzle 154. The cooling fluid supply source 152 is equipped with a pump or a cylinder for pressurizing and feeding a cooling fluid such as air, gas, water, or oil, and is optionally equipped with a cooling device for pre-cooling the cooling fluid, and pressure-feeds the cooling fluid to the spray nozzle 154. The spray nozzle 154 applies pressure-fed cooling fluid from the cooling fluid supply source 152 to the roller electrode 20 during seam welding._U , 20_Snear the pinching point of the roller electrode 20_U, 20_SThe heat is supplied by jetting it toward the part of the plate-shaped workpiece 12 that is heated by the current passing through the plate-shaped workpiece 12._H, 12_MAccording to this embodiment, the plate-shaped workpiece 12 is cooled during seam welding (cooling fluid supply step)._H, 12_MAmong them, roller electrode 20_U, 20_SThe part heated by the current from the roller electrode 20 is cooled by the cooling fluid supply device 150._U, 20_SPlate-shaped workpiece 12_H, 12_MPlate-shaped workpiece 12 generated by the heat of the molten zone N formed within_H, 12_MSince the spreading force of the melted portion N is suppressed, the melted portion N is prevented from spreading to the plate-shaped workpiece 12._H , 12_MThis advantageously prevents the formation of a hard film within the cavity.

24 is a conceptual diagram showing the main components of a seam welding apparatus according to another embodiment of the present invention, which differs mainly in that four sets of retaining rollers 16 are provided in this embodiment, whereas one set of retaining rollers 16 is provided in the embodiment of FIG. In FIG. 24, a pair of plate-shaped workpieces _12H , _12M are supplied to a predetermined position by a workpiece supply device (not shown), such as a pusher, and are conveyed along the conveying direction B by five sets of guide rollers 14 (conveying step). In this conveying step, the workpieces are guided so as to slide along the guide surfaces _24U , _24S of a pair of upper and lower plate-shaped guide members _18U , _18S , whereby their edge portions are relatively positioned so as to overlap with each other by a predetermined overlap (overlapping width) S (guiding step). Then, the edge portions of the positioned pair of plate-shaped workpieces _12H , _12M are sandwiched and pressed between a pair of upper and lower roller electrodes _20U , _20S , and a welding current is passed between the pair of roller electrodes _20U , _20S , whereby the workpieces are seam-welded to each other along a _welding center line A that is parallel to the conveying direction B and passes through the center of the width of the overlapping width S of the overlapping portions of the edge portions of the _pair of plate-shaped workpieces 12H, 12M (welding step). The pair of plate-shaped workpieces _12H and _12M being welded is held in place in the thickness direction by four sets of holding rollers 16 located on the sides of the roller electrodes _20U , _20S with a predetermined clamping pressure, thereby preventing the plate-shaped workpieces _12H and _12M from spreading apart (holding process). After welding, the pair of plate-shaped workpieces _12H and _12M are transported by a conveyor 160 onto a pallet 162 and stacked.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can be applied in other ways as well.

For example, in the above-described embodiment, the edge portions of the plate-shaped workpieces 12 _H and 12 _M are seam-welded, but the seam-welding may be performed at a position closer to the center than the edge portions.

Furthermore, in the above-described embodiment, so-called mash seam welding was described in which the edge portions of the plate-shaped workpieces _12H , _12M are crushed by being sandwiched between a pair of roller electrodes _20U , _20S , but seam welding in which the edge portions are simply sandwiched between the roller electrodes _20U , _20S may also be used. In this case, the portions of the edge portions of the plate-shaped workpieces _12H , _12M that come into contact with each other may be removed in advance by chamfering or the like, or may be deformed in advance by crushing.

Furthermore, in the guide rollers 14 and holding rollers 16 of the above-described embodiment, the guide rollers 14 _HS and 14 _MS and holding rollers 16 _HS and 16 _MS located below the plate-shaped workpieces 12 _H and 12 _M are rotationally driven by the drive motor 76, but the upper guide rollers 14 _HU and 14 _MU and holding rollers 16 _HU and 16 _MU may also be rotationally driven by the drive motor 76, or the rollers on both the upper and lower sides may also be rotationally driven by the drive motor 76.

In the above-described embodiment, all of the guide rollers _14HS , _14MS are rotationally driven by the drive motor 76, but only some of them may be rotationally driven. In addition, when a pair of plate-shaped workpieces _12H , _12M can be sufficiently transported by a plurality of sets of guide rollers 14, for example, one set of holding rollers 16 in the embodiment of Figures 1 to 9 does not need to be rotationally driven.

In addition, the pair of roller electrodes 20 shown in FIGS._U, 20_SAt least one of the pair of plate-shaped workpieces 12 is driven by, for example, an electric motor 140 shown in FIG._H , 12_MThe rotation speed may be the same as the moving speed of the roller.

Furthermore, in the embodiment shown in Figures 1 to 9, the guide roller 14 is inclined by a predetermined angle θ, so that the pair of plate-shaped workpieces _12H , _12M are pressed toward the guide members _18U , _18S during transport. However, an inclined guide plate that approaches the guide members _18U , _18S as it moves in the transport direction may be provided so as to come into contact with the outer edges of the pair of plate-shaped workpieces _12H , _12M .

The above is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit and scope of the present invention.

───────────────────────────────────────────────────── Continued from the front page (72) Inventor: Muneaki Toda Toyota Motor Corporation, 1 Toyota-cho, Toyota City, Aichi Prefecture (72) Inventor: Fumito Natsumi Toyota Motor Corporation, 1 Toyota-cho, Toyota City, Aichi Prefecture (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (18)

[Claims] 1. A seam welding method for overlapping the edge portions of two plate-shaped workpieces and continuously welding the edge portions of the two plate-shaped workpieces while sandwiching the overlapped portion between a pair of roller electrodes rotatable about two parallel axes, comprising: a moving step for moving the two plate-shaped workpieces in one direction toward the roller electrodes using multiple pairs of guide rollers that sandwich the two plate-shaped workpieces in their thickness direction; a guiding step for guiding the two plate-shaped workpieces so that they are sandwiched between the pair of roller electrodes while overlapping each other with a predetermined overlap while the two plate-shaped workpieces are moved in one direction by the moving step; and a welding step for continuously welding the edge portions of the two plate-shaped workpieces sandwiched between the pair of roller electrodes by passing a welding current between the pair of roller electrodes. 2. The seam welding method of claim 1, wherein the guiding step guides the two plate-shaped workpieces by sliding the end faces of the overlapping edges of the two plate-shaped workpieces against a pair of guide surfaces provided parallel to each other in a direction perpendicular to the axis of the roller electrodes on a guide member that is fixed in position upstream of the pair of roller electrodes. 3. The seam welding method of claim 2, wherein the guiding step uses at least two pairs of guide rollers positioned on either side of the guide member and sandwiching the two plate-shaped workpieces in the thickness direction, to generate a component of force in a direction approaching the guide surfaces of the guide member in association with the transport of the two plate-shaped workpieces, thereby causing the end faces of the edge portions of the two plate-shaped workpieces to slide against the guide surfaces. 4. A seam welding method according to any one of claims 1 to 3, wherein the welding step comprises welding two plate-like workpieces together while crushing the edge portions of the two workpieces sandwiched between a pair of roller electrodes that are rotatable about two parallel axes and biased in directions that bring them closer together. 5. The seam welding method according to any one of claims 1 to 4, further comprising the step of using two pairs of holding rollers provided at lateral positions of the pair of roller electrodes to clamp the two plate-shaped workpieces in the thickness direction with a predetermined clamping pressure, thereby generating a frictional force that counteracts the spreading force of the two plate-shaped workpieces generated during the welding process, thereby preventing the two plate-shaped workpieces from spreading apart. 6. The seam welding method of claim 5, further comprising a pressing step of pre-pressing a portion of the plate-shaped workpiece where convex deformation occurs between the roller electrode and the holding roller in the axial direction of the roller electrode. 7. The seam welding method according to any one of claims 1 to 6, further comprising a roller electrode rotation driving step of rotating the roller electrode so that a driving force is transmitted from the roller electrode to the plate-like workpiece in the direction of movement thereof. 8. The seam welding method according to any one of claims 1 to 7, further comprising a cooling fluid supply step of supplying a cooling fluid to a portion of the plate-like workpiece that is clamped by the roller electrodes to cool the portion of the plate-like workpiece that is heated by the seam welding with the roller electrodes. 9. A seam welding device that overlaps the edges of two plate-shaped workpieces, sandwiches the overlapped portion between a pair of roller electrodes that rotate about parallel axes, and passes a welding current between the pair of roller electrodes to continuously weld the edges of the two plate-shaped workpieces. The device comprises: a pair of roller electrodes that are rotatable about two parallel axes and biased toward each other; multiple pairs of guide rollers that are located on both sides of the thickness of the two plate-shaped workpieces and rotatable about axes approximately parallel to the axes of the roller electrodes; and a drive device that rotates at least some of the pairs of guide rollers in a predetermined direction to move the two plate-shaped workpieces in one direction while they are sandwiched between the guide rollers in the thickness direction. a guide device that guides the two plate-shaped workpieces so that they are sandwiched between the pair of roller electrodes in a state where they are overlapped with each other by a predetermined overlap while the two plate-shaped workpieces are moved in one direction by the drive device. 10. The seam welding apparatus of claim 9, wherein the guide device includes a guide member fixedly disposed upstream of the roller electrodes and having a pair of guide surfaces extending parallel to a direction perpendicular to the axes of the pair of roller electrodes, and the end faces of the overlapping edge portions of the two plate-like workpieces are brought into sliding contact with the guide surfaces of the guide member during transport to position the two plate-like workpieces relative to one another. 11. The seam welding apparatus of claim 10, wherein the guide device has at least two pairs of guide rollers positioned on either side of the guide member in the thickness direction, sandwiching the two plate-shaped workpieces therebetween, and guiding the two plate-shaped workpieces in a direction approaching the guide surfaces of the guide member as they approach the roller electrodes, thereby causing the end faces of the edge portions of the two plate-shaped workpieces to slide against the guide surfaces. 12. The seam welding apparatus according to any one of claims 9 to 11, wherein the pair of roller electrodes presses and crushes the edge portions of two plate-shaped workpieces sandwiched between them while welding the edge portions of the plate-shaped workpieces together. 13. The seam welding apparatus of any one of claims 9 to 12, further comprising: two pairs of holding rollers rotatably disposed on either side of the pair of roller electrodes about a pair of axes parallel to the axes of the pair of roller electrodes, for sandwiching the two plate-shaped workpieces sandwiched between the pair of roller electrodes in the thickness direction; and a clamping force applying device for applying a clamping force to the two pairs of holding rollers sufficient to generate a frictional force sufficient to counteract the spreading force of the two plate-shaped workpieces generated during the welding process by the pair of roller electrodes. 14. The seam welding apparatus of claim 13, further comprising a pressing device that pre-presses the area of the plate-shaped workpiece where convex deformation is expected to occur in order to prevent convex deformation of the plate-shaped workpiece between the roller electrode and the holding roller in the axial direction of the roller electrode. 15. The seam welding apparatus of claim 14, wherein the pressing device includes an auxiliary roller rotatably disposed between the roller electrode and the holding roller in the axial direction of the roller electrode about an axis parallel to the axial direction of the roller electrode, and pressing the plate-like workpiece while allowing it to move in the direction of movement. 16. The seam welding apparatus according to claim 14, wherein the pressing device has an auxiliary skid that is provided between the roller electrode and the holding roller in the axial direction of the roller electrode and that comes into sliding contact with the plate-like workpiece. 17. The seam welding apparatus of any one of claims 9 to 15, further comprising a roller electrode rotation drive device that rotates the roller electrode so that a driving force is transmitted from the roller electrode to the plate-like workpiece in the direction of movement thereof. 18. The seam welding apparatus according to any one of claims 9 to 17, further comprising a cooling fluid supply device that supplies a cooling fluid for cooling the portion of the plate-like workpiece that is heated by the seam welding with the roller electrodes toward the portion of the plate-like workpiece that is clamped by the roller electrodes.