Abstract:
The invention concerns with connection of a lead from an electrical component of an alternator for a vehicle, and provides a terminal shape suitable for TIG welding (arc welding using a gas shielded non-consumable electrode) without being affected by dimensional accuracy of terminals to be connected to each other. Cross-shaped projections having a larger volume than a welded region of the terminal is provided near the welded region, and weld penetration (welding depth) is controlled based on a difference in heat capacity resulting from the volume difference, or melting is suppressed with promotion of heat radiation. Thus, the welding depth is stabilized without being affected by dimensional accuracy of the terminals including relative positions between them, and an alternator for a vehicle can be provided in which a lead from an electrical component has high connection reliability.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an alternator for a vehicle, and more particularly to an improvement of a weldment (weld joined portion) at which a terminal of a semiconductor part (e.g., a diode used as a rectifying device) and an electrical connection terminal of a wiring conductor, for example, are connected to each other by welding.  
           [0003]    2. Description of the Related Art  
           [0004]    In vehicular alternators (hereinafter referred to simply as “alternators”) as disclosed in Japanese Unexamined Patent Application Publication Nos. 6-98511 and 62-55878, for example, resistance welding has been conventionally employed for connection between electrical members of the alternator (e.g., between a connecting member connected to a lead from a stator or a rotor of an alternator and a terminal of a semiconductor device). More specifically, resistance welding is employed to connect copper-made pin-shaped (generally columnar) terminals of plural rectifying devices for rectifying three-phase AC power from the alternator and a steel-made terminal in the form of a flat plate, which is covered with an insulating member around it and which serves as a terminal for connecting the rectifying devices and supplying the rectified power to the vehicle side.  
           [0005]    The above-described connection terminal known as the related art generates a larger amount of heat as an output of the alternator increases, and has a problem that the insulating member and the rectifying devices may be damaged by the generated heat. To avoid such a problem, electrical resistance of the terminal for connection among the rectifying devices of the alternator having a large output must be reduced.  
           [0006]    Conceivable solutions for reducing the electrical resistance are to increase the size of a terminal shape and to change a material of the connection terminal to a good conductor such as copper. When adopting the solution to change the terminal material from the standpoint of space, however, resistance welding is not suitable for connecting the copper-made terminal of each rectifying device and an electrical connection terminal which is also made of copper, and TIG (tungsten inert gas) welding (i.e., arc welding using a gas shielded non-consumable electrode) must be used.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide a terminal shape and a weld joined structure, which are suitable for connecting copper-made terminals to each other by TIG welding, and to provide an alternator for a vehicle having stable welding quality such as weld strength and weld penetration (welding depth).  
           [0008]    According to the present invention, the above object is achieved by the feature that a portion for increasing a volume, e.g., a projection, is provided on a connecting member near its welded region to suppress an increase of the welding depth.  
           [0009]    More specifically, the above object is achieved by forming a projection near a position, at which a flat plate-shaped electrical connection terminal and a columnar terminal are joined to each other by welding, so as to project from a lateral surface of said flat plate-shaped electrical connection terminal.  
           [0010]    Also, the above object is achieved by providing a molten metal capturing portion provided in a weld joined portion of the electrical connection terminal.  
           [0011]    Further, the above object is achieved by providing a pair of heat radiating lugs near a weld joined portion of the electrical connection terminal so as to surround a rectifying device terminal.  
           [0012]    Still further, the above object is achieved by providing a thermal mass portion near a weld joined portion of the electrical connection terminal so as to suppress growth of a molten pool produced with welding. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a vertical sectional view showing one embodiment of an alternator for a vehicle in which the present invention is implemented;  
         [0014]    [0014]FIG. 2 is a right side view of the alternator of FIG. 1 in a state in which a rear cover is removed;  
         [0015]    [0015]FIG. 3 is a sectional view taken along the line A-A in FIG. 2;  
         [0016]    [0016]FIG. 4 is a sectional view taken along the line B-B in FIG. 2;  
         [0017]    [0017]FIG. 5 is a schematic view of a weld joined portion; and  
         [0018]    [0018]FIG. 6 is a schematic partial sectional view showing a state under welding. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    One embodiment of the present invention will be described below in more detail with reference to FIGS. 1, 2,  3  and  4 .  
         [0020]    A pulley  2  for transmitting a driving force from an engine (not shown) to a rotor shaft  1  is disposed at an end of the rotor shaft  1 , and a rotor  3  having claw-shaped magnetic poles, over which field coils  3   a  are wound, generates a revolving magnetic field with rotation of the pulley  2 . The revolving magnetic field induces an electromotive force in three-phase stator coils  5  wound over respective cores of a stator  4 , which is disposed around the rotor  3  with a gap left between them. The rotor shaft  1  is rotatably supported by bearings  6   a ,  6   b , and the bearings  6   a ,  6   b  are in turn supported by brackets  7 ,  8 , respectively. The cores of the stator  4  are supported by the bracket  8 . The bracket  8  is provided with a water passage  8   a  through which cooling water is circulated to cool heat generating parts such as the stator coils  5 . Gaskets  9   a ,  9   b  for sealing off the water passage  8   a  are disposed respectively at opposite ends of the water passage  8   a . The gasket  9   b  is fixed together with a plate member  10  and a rear cover  11  in a sandwiched relation to the bracket  8  using bolts  12 . A brush holder  14  for accommodating brushes  13   a ,  13   b  to supply field currents to the field coils  3   a  and a rectifier  15  for rectifying three-phase AC power generated in the stator coils  5  are both fixed to the plate member  10  using bolts  16   a ,  16   b  and nuts  17 . The brushes  13   a ,  13   b  supply the field currents to the field coils  3   a  of the rotor  3  while being held in slide contact with respective current collecting rings  19  by pressing forces of springs  18   a ,  18   b  both accommodated in the brush holder  14 . The field currents are regulated by a voltage regulator  25  accommodated in a part of the brush holder  14 , and the voltage of the field currents is adjusted to a prescribed value. The rectifier  15  comprises a minus-side diode  23  fixed to a heat radiating plate  22 , a plus-side diode  21  fixed to a heat radiating plate  20 , and a connecting member  24  for connecting respective terminals  21   a ,  23   a  of the plus-side diode  21  and the minus-side diode  23  to each other. The connecting member  24  comprises a terminal member  24   a  and an insulating member  24   b  in which the terminal members  24   a  are partly embedded. The three-phase stator coils  5  are interconnected in the form of Δ- or Y-connection, and three or four leads  5   a  from the stator coils  5  are each connected to a terminal portion  24   c  as a part of the terminal member  24   a  of the connecting member  24  of the rectifier  15 . The terminal  21   a ,  23   a  of the plus-side diode  21  or the minus-side diode  23  of the rectifier  15  is connected to another terminal portion  24   d  of the terminal member  24   a , which is positioned oppositely away from the terminal portion  24   c , and an AC current flows through the terminal member  24   a . Because the terminal member  24   a  generates heat upon the current flowing through it, a material having small electrical resistance, e.g., copper, is selected as the terminal member  24   a  of an alternator for a large power. Also, because the terminal portion  24   c  of the terminal member  24   a  and the terminals  21   a ,  23   a  of the plus-side diode  21  and the minus-side diode  23  are both made of copper, resistance welding has a difficulty in connecting them to each other, and TIG welding is used for connection therebetween. The use of TIG welding requires dimensional accuracy of each terminal and a welding electrode, and a variation occurs in weld penetration (welding depth) depending on the dimensional accuracy. The terminal portion  24   d  of the terminal member  24   a  is not uniform in shape and is provided with projected lugs  24   e  in its intermediate position that is determined in consideration of the welding depth of from the terminal end. The projected lugs  24   e  have a different heat capacity from the other part of the terminal portion  24   d . Accordingly, the projected lugs  24   e  limit the weld penetration, and even if there are large variations in distance between the welding electrode and each terminal and in dimensions of each terminal, the weld penetration is stopped at the position of the projected lugs  24   e  and the welding depth is stabilized.  
         [0021]    With this embodiment, since the weld penetration is stably set without being affected by the dimensional accuracy of the terminals, welding can be performed with stability in quality such as welding strength, and severe dimensional management is no longer required. As a result, an alternator can be provided which is relatively inexpensive and easy to manufacture.  
         [0022]    Another advantage is in that, by bending the projected lugs  24   e  of the terminal portion  24   d  of the terminal member  24   a  toward the side of the terminal  21   a ,  23   a  of the plus-side diode  21  or the minus-side diode  23 , it is possible to easily position the terminal portion  24   d  of the terminal member  24   a  relative to the terminal  21   a ,  23   a  of the plus-side diode  21  or the minus-side diode  23 .  
         [0023]    With reference to FIGS. 5 and 6, a description is made in detail of how the terminal  21   a  of the plus-side diode  21  fixed to the heat radiating plate  20  and the terminal  23   a  of the minus-side diode  23  fixed to the heat radiating plate  22  are welded to the electrical connection terminal members  24   a  to  24   e  by arc welding using a gas shielded non-consumable electrode. Note that, in FIGS. 5 and 6, principal parts are illustrated in exaggerated fashion with dimensions somewhat different from actual ones.  
         [0024]    As shown in FIGS. 3 and 4, the heat radiating plates  20 ,  22 , to which the plus-side diode  21  and the minus-side diode  23  are fixed respectively, are disposed in two steps one above the other in the height direction. Therefore, the distances from the positions, at which the plus-side diode  21  and the minus-side diode  23  are mounted, to respective welding positions differ from each other depending on which one of the plus-side diode  21  and the minus-side diode  23  is subjected to the welding.  
         [0025]    In this embodiment, the connecting member  24  comprises the insulating member  24   b  made of an insulating resin, and an electrical connection conductor made of copper or a copper alloy and partly molded (embedded) in the insulating member  24   b . The terminal member  24   a  is a part of the electrical connection conductor.  
         [0026]    The terminal member  24   a  is projected out of an edge of an insulating plate constituting the insulating member  24   b , and a part of the terminal member  24   a , which is bent at 90 degrees relative to the insulating plate of the insulating member  24   b  and extended from it, serves as the terminal portion  24   d . The terminal portion  24   d  is extended in a juxtaposed relation to each of the terminals  21   a ,  23   a  of the plus-side diode  21  and the minus-side diode  23 .  
         [0027]    The terminals  21   a ,  23   a  of the plus-side diode  21  and the minus-side diode  23  have lengths set different from each other such that terminal upper ends are located in positions at the same level.  
         [0028]    A pair of left and right projected lugs (projections)  24   e  projecting from each terminal portion  24   d  in the cross form are formed midway each of the terminal portions  24   d  at the same level.  
         [0029]    The terminals  21   a ,  23   a  of the plus-side diode  21  and the minus-side diode  23  are arranged adjacent to the respective terminal portions  24   d . Preferably, the terminals  21   a ,  23   a  and the terminal portions  24   d  are held in a closely contact state.  
         [0030]    In that condition, the projected lugs  24   e  are slightly bent toward the terminal  21   a  or  23   a  so as to surround it. The amount by which the projected lugs  24   e  are bent is set to be the same regardless of the terminal type, and is adjusted to a value that has been determined based on experiments beforehand for each model in consideration of the effect of the projected lugs  24   e  limiting the metal penetration (welding depth of the metal) during the welding.  
         [0031]    A gas nozzle N of a welding device is moved toward a preset position between the projected lugs  24   e  and a distal end of the terminal portion  24   d , and generates an arc A between a distal end of a tungsten electrode Tg and the terminal portions  24   d.    
         [0032]    An inert gas G is ejected from the surroundings of a collet K, and the arc welding is performed in the inert gas G. A welding rod P is automatically inserted into the arc A by the welding device.  
         [0033]    When the tungsten electrode Tg is set to a plus electrode, the weld penetration in a weldment is small, but a superior cleaning action is obtained in the welding position.  
         [0034]    On the other hand, when the tungsten electrode Tg is set to a minus electrode, the weld penetration in a weldment is increased. In this embodiment, the welding is performed in the latter setting.  
         [0035]    When the arc A occurs, the terminal portions  24   d  as a base material and the terminal  21   a  or  23   a  as a welding metal are molten, whereupon a molten pool S is produced. In the molten pool S, three kinds of metals including the metal of the welding rod fused together, and a metal joined layer is formed after cooling.  
         [0036]    Since the distance and angle of the tungsten electrode Tg relative to a welded region differ, though just a small, depending on each of welded regions, the extent of growth of the molten pool S also differs correspondingly. The welding time is set such that a weld joined portion is surely formed even under the worst welding conditions. In a place where better welding conditions are satisfied, therefore, the molten pool S grows faster and spreads over a larger area. The inventors have discovered that, if there occurs a variation in growth of the molten pool, the resistance value is affected when looking at the weld joined portion as an electrical conductor.  
         [0037]    Then, the inventors have made endeavors to find a solution for keeping the growth of the molten pool as even as possible. The principle of the effective solution resides in that a heat radiating portion having a large thermal mass is disposed near the weld joined portion in the direction of growth of the molten pool, whereby when the molten pool reaches the position of the heat radiating portion, further growth of the molten pool is prevented.  
         [0038]    Based on that principle, even when a relatively long welding time is required depending on the welded region, the growth of the molten pool is surely stopped at the position of the heat radiating portion, and an area over which the weld joined metal portion spreads becomes more uniform than in the related art. As a result, the weld joined portion can be formed with even electrical resistance.  
         [0039]    This implies that currents flowing in armatures and rotors can be made even in individual alternators, and hence alternators having smaller variations in performance and higher quality can be mass-produced.  
         [0040]    In short, basic constructions of the preferred embodiment and examples of the present invention are as follows:  
         [0041]    1. An alternator for a vehicle comprises a stator  4 , a rotor  3  rotatably disposed inside the stator  4  with a predetermined gap therebetween, and a semiconductor device (plus-side diode  21  or minus-side diode  23 ) electrically connected through a connecting member  24  to at least a lead  5   a  from each of the stator  4  and the rotor  3 . A portion of the connecting member  24  welded to the lead (lead  5   a  from a stator coil  5 ) has a smaller volume than the other portions of the connecting member  24  and the lead (lead  5   a  from the stator coil  5 ).  
         [0042]    2. A material of an electrically conductive portion of the connecting member  24  (terminal portion  24   a  of the connecting member  24 ) is copper or a copper alloy.  
         [0043]    3. An alternator for a vehicle comprises an insulating plate (connecting member  24 ) mounted to an alternator body; a flat plate-shaped electrical connection terminal (terminal member  24   a ) projecting from an edge of the insulating plate; and a rectifying device (plus-side diode  21  or minus-side diode  23 ) having a columnar terminal (terminal  21   a  or  23   a ) extended in a juxtaposed relation to the electrical connection terminal (terminal member  24   a ), the flat plate-shaped electrical connection terminal (terminal member  24   a ) and the columnar terminal (terminal  21   a  or  23   a ) being joined to each other by welding (TIG welding). The flat plate-shaped electrical connection terminal (terminal member  24   a ) has a projection (projected lug  24   e ) formed near (under) a position, at which the flat plate-shaped electrical connection terminal and the columnar terminal are joined to each other by welding, so as to project from a lateral surface of the flat plate-shaped electrical connection terminal (terminal member  24   a ).  
         [0044]    4. The projection (projected lug  24   e ) comprises a pair of projections extending in directions opposed to each other, and the flat plate-shaped electrical connection terminal (terminal portion  24   a ) and the projection (projected lug  24   e ) intersect in a cross form.  
         [0045]    5. The flat plate-shaped electrical connection terminal (terminal portion  24   a ) and the columnar terminal (terminal  21   a  or  23   a ) of the rectifying device (plus-side diode  21  or minus-side diode  23 ) are made of copper or a copper alloy having electrical conductivity.  
         [0046]    6. The flat plate-shaped electrical connection terminal (terminal portion  24   a ) and the columnar terminal (terminal  21   a  or  23   a ) of the rectifying device (plus-side diode  21  or minus-side diode  23 ) are welded to each other by arc welding using a gas shielded non-consumable electrode.  
         [0047]    7. An alternator for a vehicle comprises an electrical connection terminal (terminal portion  24   a ) made of copper or a copper alloy; and a molten metal capturing portion (projected lug  24   e ) provided near a weld joined portion (molten pool S) of the electrical connection terminal to a terminal (terminal  21   a  or  23   a ) of a rectifying device (plusside diode  21  or minus-side diode  23 ), which is made of copper or a copper alloy.  
         [0048]    8. An alternator for a vehicle comprises an electrical connection terminal (terminal member  24   a ) made of copper or a copper alloy; and a pair of heat radiating lugs (projected lugs  24   e ) provided near a weld joined portion (molten pool S) of the electrical connection terminal (terminal member  24   a ) to a terminal (terminal  21   a  or  23   a ) of a rectifying device (plus-side diode  21  or minus-side diode  23 ), which is made of copper or a copper alloy, the pair of heat radiating lugs surrounding the terminal (terminal  21   a  or  23   a ) of the rectifying device (plus-side diode  21  or minus-side diode  23 ).  
         [0049]    9. An alternator for a vehicle comprises an electrical connection terminal (terminal member  24   a ) made of copper or a copper alloy; and a thermal mass portion (projected lug  24   e ) provided near a weld joined portion (molten pool S) of the electrical connection terminal to a terminal (terminal  21   a  or  23   a ) of a rectifying device (plus-side diode  21  or minus-side diode  23 ), which is made of copper or a copper alloy, the thermal mass portion suppressing growth of the molten pool S produced with welding.  
         [0050]    According to the present invention, as described above, quality of the weld joined portion in an alternator for a vehicle is ensured. For example, welding quality such as weld strength and weld penetration is stabilized. As a result, quality of individual alternators is stabilized. For example, a variation in electrical resistance value of the weld joined portion is reduced.