Abstract:
A first assembly includes a board member for wiring an electric wire thereon, and a first bus bar electrically connected to the electric wire. The first bus bar includes a first tab-shaped terminal having a first dimension in a first direction and a second dimension smaller than the first dimension in a second direction perpendicular to the first direction. A second assembly is joined to the first assembly in the first direction. The second assembly includes a mount section in which an electric component is mounted, and a second bus bar electrically connected to the electric component: The second bus bar includes a second tab-shaped terminal having a third dimension in the first direction and a fourth dimension smaller than the third dimension in the second direction. The first terminal and the second terminal are arranged so as to be overlapped in the second direction to be welded to each other, after the second assembly is joined to the first assembly, and arranged such that a relative position between the first terminal and the second terminal is gradually changed in the first direction during the joining operation of the first assembly and the second assembly.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a structure and a method for connecting bus bars in an electric junction box for electrically connecting an electric component block such as a fuse block to a circuit board assembly including wiring circuit boards, bus bar circuit boards and so on, by way of bus bars, by welding. 
     FIGS. 6 and 7 show one example of a conventional connecting structure of bus bars in an electric junction box, which is disclosed in Japanese Patent Publication No. 2001-309526A (cf., Page 3 and FIGS. 1 to  5 ). 
     This electric junction box comprises: an assembly  51  of a plurality of bus bar circuit boards which are stacked one on another, a relay block  54  which is connected by welding to terminal portions  53  of bus bars  52  (see FIG. 7) of the circuit board assembly  51 ; a fuse block  55  which is disposed on the circuit board assembly; and a cover  56  (see FIG. 7) made of synthetic resin for covering a sub assembly of these elements. 
     Each of the bus bars  52  is formed by stamping an conductive sheet metal into a desired circuit shape, and by bending a desired end portion of the bus bar  52  at a right angle or by extending it straightly to form a terminal portion  53 . The terminal portion  53  projects from one side edge of the circuit board assembly  51 , and is connected by welding to a terminal portion  57  at one end of bus bar  66  of the relay block  54 . Both the terminal portions  53  and  57  are clamped between a pair of electrodes of a resistance welding machine (not shown), and electrically heated to be welded. The relay block  54  is juxtaposed with the circuit board assembly  51 . 
     A terminal portion (not shown) at the other end of the bus bar  66  of the relay block  54  is connected to a relay connecting terminal (not shown) in a relay mounting part  65 . Terminal portions  58  projected from edges of the circuit board assembly  51  constitute a fuse connecting part in cooperation with terminal portions  59  of the fuse block  55 , for example. A fuse (not shown) having a pair of terminals is connected to the fuse connecting part. The bus bars  60  of the fuse block  55  are connected to vertical terminal portions  62  of the bus bars  61  of the circuit board assembly  51 , for example. 
     Other terminal portions  63  vertically uprighted from the circuit board assembly  51  are contained in a housing part  64  of the cover  56  (see FIG. 7) to constitute a connector or the like. An exterior wire harness (a power source circuit or an auxiliary equipment circuit) is connected to the connector. In this manner, the power source in the exterior, the bus bars, the relays, the fuses and an auxiliary equipment are mutually connected. 
     However, in the above configuration, when the terminal portions  57  of the relay block  54  are connected to the terminal portions  53  of the circuit board assembly  51 , they are positioned and welded by abutting the terminal portions  53 ,  57  in an L-shape against each other in a direction of their thickness. For this reason, there has been such an anxiety that the terminal portions  53 ,  57  may be excessively pushed and deformed, resulting in variations in welding strength, and reliability of the electrical connection is liable to be deteriorated. 
     There has been a further anxiety that when the terminal portions  53 ,  57  are abutted against each other, the bus bars  66  of the relay block may be pushed in a longitudinal direction and may give bad influences to the terminals in the relay mounting part  65  to deform them. Moreover, since relative position of the circuit board assembly  51  with respect to the relay block  54  is determined by the connecting position between the terminal portions  53  and  57 , the positions of the circuit board assembly  51  and the relay block  54  to be fixed to the cover (not shown) may vary due to variations of the connecting position, which leads to an anxiety that an assembling work cannot be conducted smoothly. Further, because it has been difficult to position the terminal portions  57  of the relay block  54  with respect to the terminal portions  53  of the circuit board assembly  51 , there has been an anxiety that a lot of trouble and many positioning tools may be required, and connecting workability may be deteriorated. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a structure and a method for connecting bus bars, in which it is possible to reliably perform connections between the bus bars of a circuit board assembly and the bus bars of an electric component block provided with electric components such as relays, fuses. 
     It is also an object of the invention to provide a structure and a method for connecting bus bars, in which, in which it is possible to smoothly and reliably assemble the electric component block to the circuit board assembly with good workability, without being affected by variations or so in connecting positions between terminal portions of the respective bus bars. 
     In order to achieve the above objects, according to the invention, there is provided a connection structure in an electric junction box, comprising: 
     a first assembly, comprising: 
     a board member, for wiring an electric wire thereon; and 
     a first bus bar, electrically connected to the electric wire, and including a first tab-shaped terminal having a first dimension in a first direction and a second dimension smaller than the first dimension in a second direction perpendicular to the first direction; and 
     a second assembly, joined to the first assembly in the first direction, the second assembly comprising: 
     a mount section, in which an electric component is mounted; and 
     a second bus bar, electrically connected to the electric component, and including a second tab-shaped terminal having a third dimension in the first direction and a fourth dimension smaller than the third dimension in the second direction, wherein: 
     the first terminal and the second terminal are arranged so as to be overlapped in the second direction to be welded to each other, after the second assembly is joined to the first assembly, and arranged such that a relative position between the first terminal and the second terminal is gradually changed in the first direction during the joining operation of the first assembly and the second assembly. 
     In such a configuration, both the first and second terminals will not be affected by a pressure in the second (thickness) direction and bending deformation of the terminals will be prevented. Moreover, because the direction of joining the first and second assemblies is same as the first (widthwise) direction of the terminals, the second assembly will be smoothly joined to the first assembly without being affected by connection between the terminals (that is, the relative position in the joining direction). Therefore, for example, a terminal in the first assembly to be connected to the electric component can be perfectly placed at a predetermined position in the second assembly. 
     It is preferable that: the first terminal is provided at a side end portion of the first assembly in the second direction, and extending in a third direction orthogonal to the first direction and the second direction; and the second terminal is provided at a side end portion of the second assembly in the second direction, and extending in the third direction. 
     In such a configuration, it is possible to obtain enough space to weld the terminals extended in the third direction, while reducing the space required for the terminals in the second direction. 
     Here, it is further preferable that a top end of the first terminal is situated upper than a top face of the first assembly. 
     In such a configuration, the workability of the welding operation can be further enhanced. 
     It is also preferable that: the second bus bar includes a joint portion continued from the second terminal and extending in the second direction; and the joint portion is fitted into the mount section in the first direction to receive the electric component. 
     In such a configuration, even when the terminals are brought into contact with each other in the second direction and a repulsion force is generated therebetween, such a repulsion force will not serve as a force for removing the second bus bar from the second assembly. Therefore, the inadvertent removal of the second bus bar can be avoided. 
     It is also preferable that: the first bus bar includes a third terminal extending in the first direction; and the third terminal is placed in the mount section to receive the electric component when the second assembly is joined to the first assembly. 
     In such a configuration, since the direction of entering the third terminal into the mount section is the same as the joining direction of the assemblies, even if the terminals are brought into contact with each other in the second direction and a repulsion force is generated therebetween, such a repulsion force will not affect the joining operation. 
     It is also preferable that the connecting structure further comprises a positioning member for determining a relative position between the first assembly and the second assembly. 
     In such a configuration, the joining operation of the assemblies can be performed smoothly and reliably. 
     According to the invention, there is also provided a method of providing a connection structure in an electric junction box, comprising steps of: 
     providing a first assembly, comprising: 
     a board member, for wiring an electric wire thereon; and 
     a first bus bar, electrically connected to the electric wire, and including a first tab-shaped terminal having a first dimension in a first direction and a second dimension smaller than the first dimension in a second direction perpendicular to the first direction; and 
     providing a second assembly, comprising: 
     a mount section, in which an electric component is mounted; and 
     a second bus bar, electrically connected to the electric component, and including a second tab-shaped terminal having a third dimension in the first direction and a fourth dimension smaller than the third dimension in the second direction; 
     joining the second assembly to the first assembly in the first direction while a relative position between the first terminal and the second terminal is gradually changed in the first direction; and 
     welding the first terminal and the second terminal which are overlapped in the second direction, after the second assembly is joined to the first assembly. 
     It is preferable that: the first bus bar includes a third terminal extending in the first direction; and the second bus bar includes a joint portion continued from the second terminal and extending in the second direction. The method further comprises steps of: fitting the joint portion into the mount section in the first direction, before the second assembly is joined to the first assembly; and placing the third terminal in the mount section to receive the electric component when the second assembly is joined to the first assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
     FIG. 1 is an exploded perspective view of a connecting structure of bus bars in an electric junction box according to one embodiment of the invention; 
     FIG. 2 is a perspective rear view of a fuse block of the electric junction box; 
     FIG. 3 is a perspective view of the bus bars contained in the fuse block; 
     FIG. 4 is a rear view of a block body of the fuse block; 
     FIG. 5 is a perspective view showing a state that the fuse block is assembled to a circuit board assembly; 
     FIG. 6 is an exploded perspective view of a conventional connecting structure of bus bars in an electric junction box; and 
     FIG. 7 is a longitudinal sectional view showing the conventional connecting structure. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the invention will be described below in detail with reference to the accompanying drawings. 
     As shown in FIG. 1, this electric junction box comprises: a wiring circuit board  2 , a bus bar circuit board  3 , and a fuse block (an electric component block)  4  which are assembled into a sub assembly  1 ; and upper and lower covers (not shown) made of synthetic resin for covering this sub assembly  1 . 
     The wiring circuit board  2  has a flat case  5  made of insulative synthetic resin, and a plurality of electric wires  6  which are arranged in a desired shape in the case  5  and connected to press-fitting terminals  7  disposed inside the case  5 . The press-fitting terminals  7  are integrally formed with tab terminals  8  and elongated pin terminals  9 . These terminals  8 ,  9  are contained in a connector housing in the cover to constitute a connector (not shown), or connected to an electronic unit (not shown) inside the cover. In this embodiment, two of the upper and lower wiring circuit boards  2  are provided. 
     The bus bar circuit boards  3  are stacked in a plurality of layers and integrated with a front half area of the respective wiring circuit boards  2 . A circuit board assembly  10  is composed of the wiring circuit boards  2  and the bus bar circuit boards  3 . The electric wires  6  of the wiring circuit boards  2  are for a circuit for small current, and bus bars  11  of the bus bar circuit boards  3  are for a circuit for large current such as a power supply. The fuse block  4  is joined to the circuit board assembly  10  in a direction of an arrow mark A (a joining direction). 
     The bus bar circuit board  3  has an insulative board  12 , and a plurality of the bus bars  11  made of conductive material and arranged in a desired shape on a face of the insulative board  12 . The bus bars  11  respectively have uprighted tab terminals  13 , press-fitting terminals  14  which are bent downward and press-fitted to the electric wires  6  of the wiring circuit board  2 , horizontal U-shaped terminals (clamping terminals)  15  for connecting fuses, plate-shaped terminal portions  19 - 21  which are vertically uprighted and connected by welding to bus bars  16 - 18  in the fuse block  4 . 
     As shown in FIGS. 1 and 2, these terminal portions  1921  to be welded are arranged in right and left ends of the bus bar circuit board  3 , and projected higher than the bus bar circuit board  3   1  in the uppermost layer. The terminal portions  19  and  20  at the right side (in FIG. 1) are uprighted from the bus bars of the bus bar circuit board  3   2  in the second layer from the top, and juxtaposed in the front-rear direction. The terminal portion  21  at the left side (in FIG. 1) is uprighted from a front end part of the uppermost bus bar circuit board  3   1 . 
     The terminal portions  19 ,  20  at the right side are located along a side face of the bus bar circuit board  3  such that outer faces of the terminal portions  19 ,  20  are made flush with the side face of the bus bar circuit board  3 . Similarly, an outer face of the terminal portion  21  at the left side is made flush with the other side face of the bus bar circuit board  3  while being projected slightly forward from a front edge of the bus bar circuit board  3 . The bus bar having the front terminal portion  19  is continued to the clamping terminal  15  in a forward area, and the bus bar having the rear terminal portion  20  is continued to a backward area (for example, an area where the electric wires are press-fitted). 
     The fuse block  4  comprises a block body  22  made of insulative resin; a short bus bar  17 ; and long bus bars  16 ,  18 . The block body  22  in this embodiment has a plurality of fuse chambers (electric component chambers)  23  arranged in parallel to form two upper and lower rows. As shown in FIG. 3, the bus bars  16 - 18  are provided with vertical terminal portions  24 - 26  to be subjected to the welding; and fuse connecting portions point portions)  27 ,  28  which are bent from the terminal portions  24 - 26  and extend horizontally. Since the joint portions  27  of a pair of the long right and left bus bars  16 ,  18  have substantially the same shape, the bus bar  18  at the left side is omitted in FIG.  3 . 
     The terminal portions  24 - 26  are positioned along both sides of the block body  22 . The terminal portions  24 ,  25  at the right side are juxtaposed in the front and the back. The joint portion  27  continued from the front terminal portion  24  is positioned at upper edges of the fuse chambers  23  in the lower row (see FIG.  2 ), and has a plurality of U-shaped terminals (clamping terminals)  30  which are arrayed at an equal pitch and adapted to enter into the respective fuse chambers  23 . The joint portion  27  continued from the front terminal portion  24  is contained in a slit  32  which extends horizontally from a side wall  31  (see FIG. 2) of the block body  22 . The joint portion  29  (see FIG. 2) of the bus bar  18  is contained in this slit  32  in symmetry with the joint portion  27  of the bus bar  16 . Direction of inserting the fuse connecting portions  27 - 29  of the bus bars  16 - 18  matches with a direction of width of the terminal portions  24 - 26  and a direction of inserting the clamping terminals  15 ,  30 . 
     As shown in FIG. 3, the rear terminal portion  25  at the right side of the fuse block  4  is formed in an L-shape having a vertical portion  25   a  and a horizontal portion  25   b , and a lower part of a tip end of the horizontal portion  25   b  is perpendicularly bent to be continued to a short fuse connecting portion  28 . The fuse connecting portion  28  has only one clamping terminal  30  and only one tab portion  33 . The tab portion  33  is also provided on the fuse connecting portion  27  continued from the front terminal portion  24 . The tab portions  33  serve as a positioning and retaining member for the block body  22 . 
     As seen on a back face (an inner face) of the block body  22  as shown in FIG. 4, the respective tab portions  33  are introduced into upper and lower slots  34 ,  35  to be engaged therewith. The respective clamping terminals  30  are introduced into slots  36  which are juxtaposed to the slots  34 ,  35 . The joint portions  27 ,  29  of a pair of the right and left bus bars  16 ,  18  are stacked one on another and inserted into the slit  32  in a press-fitting manner without a clearance. 
     In FIG. 1, the front and rear terminal portions  24 ,  25  of the fuse block  4  aligned on the same vertical plane as in the terminal portions  19 ,  20  of the circuit board assembly  10 . Respective upper ends of the terminal portions  24 ,  25  are extended to the same height and formed with protrusions (indents)  37  for welding are formed by swelling inwardly (see FIG.  3 ). The bus bar  18  at the left side has a substantially symmetrical shape to the long bus bar  16  at the right side. The terminal portion  26  at the left side straightly extends upwardly along a side face of the block body  22 , and is located in substantially symmetry with the front terminal portion  24  at the right side. The block body  22  is partly cut out so that at least top end parts of the front terminal portions  24 ,  26  are exposed to the exterior to a large extent, as shown in FIG.  1 . 
     As shown in FIG. 3, the front terminal portion  24  at the right side is enlarged in width in the joining direction in comparison with the rear terminal portion  25 , and has an upwardly projected part  24   a  in a rear half portion thereof. Different from the terminal portion  26  at the left side, the terminal portion  24  has the protrusion  37  in the projected part  24   a . Shapes, sizes, etc. of these terminal portions  24 - 26  can be appropriately determined according to configurations of the fuse block  4 , the terminals  15  on the bus bar circuit boards  3 , and so on. 
     At least a pair of right and left positioning projections  38  are provided at a front end face of the wiring circuit board  2  (see FIG.  1 ), and a pair of right and left recesses  39  adapted to be engaged with the projections  38  are provided in the fuse block  4  (see FIGS.  2  and  4 ). The recesses  39  are positioned directly above the joint portions  27 ,  29  of the right and left bus bars  16 ,  18 , and peripheral walls of the respective recesses  39  serve also as members for holding areas near the bent parts of the joint portions  27 ,  29 . 
     As shown in FIG. 5, by assembling the fuse block  4  to the circuit board assembly  10 , inner faces of the terminal portions  24 - 26  of the bus bars  16 - 1 B of the fuse block are brought into contact with or placed in proximity to (with slight clearances) outer faces of the terminal portions  19 - 21  of the bus bars  11  of the circuit board assembly  10 . The terminal portions  19 - 21  and  24 - 26  protrude higher than the bus bar circuit board  3   1  in the uppermost layer, and the top ends of the terminal portions  19 - 21 ,  24 - 26  are positioned at the same height. 
     The fuse block  4  and the circuit board assembly  10  are aligned with respect to each other by initially engaging the positioning projections  38  (see FIG. 1) with the recesses  39  (see FIG.  2 ). Then, by inserting the projections  38  into the recesses  39 , insertion of the clamping terminals  15  of the circuit board assembly  10  into the fuse block  4  can be performed smoothly, easily and accurately. 
     On occasion of such assembling, the fuse block  4  is moved toward a front end of the circuit board assembly  10 , as shown by the arrow mark A in FIG. 1, so that the clamping terminals  15  are permitted to enter into the fuse chambers  23 . In this embodiment, the clamping terminals  15  are positioned at upper and lower parts in the chambers  23  in the upper row, and at lower parts in the chambers  23  in the lower row of the fuse block  4  (except areas where the clamping terminal  30  of the short bus bar  17  is contained). 
     Because the clamping terminals  30  of the long bus bar  16  of the fuse block  4  are contained in the fuse chambers  23  in the lower row, the bus bars  16 - 18  of the fuse block and the bus bars  11  of the circuit board assembly  10  are connected to each other by way of a plurality of fuses  40  (see FIG.  5 ). The short bus bar  17  at the lower side of the fuse block  4  and the long bus bar  16  at the upper side are connected by way of a single fuse  40 . 
     When the fuse block  4  is assembled to the circuit board assembly  10 , the terminal portions  24 - 26  of the bus bars  16 - 18  of the fuse block move in a direction perpendicular to the thickness direction of the terminal portions, that is, in a widthwise direction of the terminal portions. During the joining operation, the inner faces of the terminal portions  24 - 26  of the fuse block  4  are slid on the outer faces of terminal portions  19 - 21  of the circuit board assembly  10  in the widthwise direction of the terminal portion. 
     Since the widthwise direction of the terminal portions matches with the direction of joining the fuse block  4  and the circuit board assembly  10 , both the terminal portions  19 - 21  and  24 - 26  are gradually overlapped on each other in the thickness direction thereof, while relatively moving in the widthwise direction thereof, during the joining operation. 
     According to the above described structure, different from the conventional configuration, the terminal portions will not excessively press with each other in the thickness direction thereof. Therefore, the terminal portions  19 - 21  and  24 - 26  will not be deformed nor displaced, and welding work in the next step can be accurately conducted. 
     Moreover, because the fuse connecting portions  27 - 29  of the bus bars  16 - 18  in the fuse block  4  are inserted into the block body  22  in the same direction as the widthwise direction of the terminal portions  24 - 26 . Therefore, when the fuse block  4  is joined to the circuit board assembly  10 , even if the terminal portions  19 - 21  and  24 - 26  are tightly fitted to each other by elastic forces in the thickness direction thereof (that is, repulsive forces in the thickness direction are accordingly generated), no force will be exerted in a direction to for removing the fuse connecting portions  27 - 29 , and there will be no anxiety that the fuse connecting portions  27 - 29  may be detached from the fuse block  4 . 
     Further, the clamping terminals  15  of the circuit board assembly  10  are projected and inserted into the fuse block  4  in the widthwise direction of the terminal portions  19 - 21  and  24 - 26 . Therefore, in a state where the terminal portions  19 - 21  and  24 - 26  are in slide contact with each other, the terminals  15  are reliably inserted into the fuse block  4 , and there will be no anxiety that incomplete insertion may occur. In the conventional case in which the terminal portions have been abutted against each other in the thickness direction thereof, it is sometimes happened that the terminals  15  are not inserted into the fuse block  4  with a perfect stroke due to variations in projected positions of the terminal portions. In this case, contact between the terminals  15  and the terminals  41  of the fuses  40  (see FIG. 5) in the fuse block will be incomplete. 
     Both the terminal portions  19 - 21  and  24 - 26  are clamped with pressure in the thickness direction thereof by a pair of electrodes (not shown) of a resistance welding machine, and electrically heated to be welded to each other. Since the terminal portions  19 - 21  and  2426  are projected higher than the circuit board assembly  10 , a large space can be obtained for disposing the electrodes, and the welding work can be easily and rapidly conducted. It is also possible to conduct automatic welding, employing an automatic assembling machine. 
     By welding the terminal portions  19 - 21  and  24 - 26 , the fuse block  4  is provisionally fixed to the circuit board assembly  10 . The sub assembly  1  composed of the fuse block  4  and the circuit board assembly  10  is contained and fixed in upper and lower covers (a main cover and an under cover) which are not shown. 
     The respective terminal portions  24 - 26  of the bus bars are located along (in proximity to or in contact with) inner wall faces of the main cover having insulative property, and reliably insulated and protected from the exterior. The front face of the fuse block  4  is exposed to the exterior, and the fuses which are covered with fuse covers so as to be opened and closed are protected in a detachable manner. The fuse  40  (see FIG. 5) has a pair of tab terminals  41  which are clamped between the clamping terminals  15 ,  30  to be connected therewith. 
     An electronic control unit (not shown), for example, is disposed underneath of the wiring circuit board  2 , and covered with a unit cover (not shown) to be protected. The electric junction box is composed of the circuit board assembly  10 , the fuse block  4 , the electronic control unit, and the covers. The main cover (not shown) which is positioned in an upper part in FIG. 5 has a plurality of connector housings in which the terminals  8 ,  13  respectively uprighted from the circuit boards  2 ,  3  in the upper layers (see FIG. 1) are contained, thereby to constitute a connector. An exterior wire harness (not shown) such as a power source is connected to the connector. The bus bar circuit boards  3  are connected to the electric wires  6  of the wiring circuit boards  2  by way of the press-fitting terminals  14 . 
     The bus bars  11  of the circuit board assembly  10  are connected to the bus bars  16 - 18  of the fuse block  4  by way of the terminal portions  19 - 21  and  24 - 26  for welding connection, enabling both the bus bars  11  and  16 - 18  to be connected by way of the fuses  40 . The bus bars  11  of the circuit board assembly  10  are connected to the tab terminals  8  and the pin-shaped terminals  9  in the connector by way of the electric wires  6 , or directly connected to the connector, relays and so on, by the tab terminals  13  of the bus bars  11 . 
     In the above described embodiment, directivity of the electric junction box in vertical, longitudinal, and lateral directions can be appropriately changed according to situations in which the electric junction box is used (a direction of assembling to a vehicle). Moreover, the above described electric junction box is simply one of the examples, and can be appropriately configured according to specifications of the circuits. For example, the electronic control unit may be omitted, the wiring circuit board  2  and the bus bar circuit board  3  may be formed in two layers or more, or only in one layer, and the fuses of the fuse block  4  may be arranged in three steps or in one step. Also according to the specifications of the circuits, either of the front and rear terminals  24 ,  25  at the right side may be omitted, or the bus bar  18  and the terminal  26  at the left side may be omitted. 
     Further, it is possible to constitute the circuit board assembly  10  without employing the wiring circuit board  2 , but employing only the bus bar circuit board  3 . It is also possible to employ a relay block or the like as the electric component block, in place of the fuse block  4 . It is also possible to provide the projections  38  as the positioning means on the fuse block  4 , and to provide the recesses  39  to be engaged with the projections  38  on the circuit board assembly  10 . It is also possible to employ other means such as laser beam welding, soldering, etc. instead of the resistance welding.