Abstract:
A spot welding system is disclosed. In particular, the spot welding system includes an upper moving unit provided with an upper electrode and a lower moving unit mounted separately from the upper moving unit and provided with a lower electrode corresponding to the upper electrode. Together, the upper moving unit and the lower moving unit separately vary a position of the lower electrode to allow for reduced size restrictions of objects to be spot welded therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0168970 filed in the Korean Intellectual Property Office on Dec. 31, 2013, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention lo The present invention relates to a spot welding system and an operation method for the same. More particularly, the present invention relates to a spot welding system and an operation method for the same may increase the speed at which a spot weld may be completed regardless of size of panels through the use of separated upper and lower welding electrodes. 
     (b) Description of the Related Art 
     In general, several parts such as panels, roofs, pillars, side panels, flanges of opening portions for a vehicle body door and so on, are bonded by spot welding in the assembly line of a vehicle body factory. Spot welding is a welding method of bonding objects via a small concentrated weld, using electric resistance by applying electricity and pressure to weld together portions that overlap. 
     A spot welding device, for example C-type welding gun, is used for spot welding and typically includes a fixed electrode and a moving electrode on a gun body. The spot welding device performs spot welding on an object to weld, using electric resistance by pressing the object to weld supported on the fixed electrode, operating the movable electrode with an actuator, and applying electric resistance to the fixed electrode and the moving electrode. 
     However, the upper electrode and the lower electrode are connected by a welding gun arm, thus the size of the panel for welding is limited by distance between the welding electrodes and the welding gun. 
     Increasing entire size of the welding gun may overcome the above drawback, but welding gun may then be too big and heavy to manage. Thus, mounting the welding gun to a robot or operating the welding gun may be restricted, and welding speed may deteriorate. Thus, numbers of robots, costs for facilities, maintenance expenditure, space for equipment and so on may be increased. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a spot welding system and an operation method for the same having advantages of implementing spot weld with high speed regardless of the size of panels by utilizing by separating the upper and lower welding electrodes. 
     Also, the present invention has been made in an effort to provide a spot welding system and an operation method for the same having advantages of reducing numbers of robots, costs for facilities, maintenance expenditure, space for equipment and so on. 
     Also, the present invention has been made in an effort to provide a spot welding system and an operation method for the same having advantages of improving productivity and efficiency of welding. 
     A spot welding system according to one or a plurality of exemplary embodiments of the present invention may include an upper moving unit provided with an upper electrode and configured and disposed to vary a position of the upper electrode, and a lower moving unit mounted separately from the upper moving unit, provided with a lower electrode corresponding to the upper electrode, and configured and disposed to vary a position of the lower electrode. 
     The upper moving unit may include a welding gun where the upper electrode is mounted through a pushing unit and a robot where the welding gun is mounted thereto. The robot configured to vary a position of the welding gun. 
     The pushing unit may include a gear box mounted to the welding gun, a pushing actuator mounted to a lower portion of the gear box, and a first moving block where the upper electrode is mounted, mounted to the lower portion of the gear box. The first moving block selectively moves up and down by an operation of the pushing actuator. 
     The lower moving unit may include a table, length direction moving members disposed on both ends of the table along length direction of the table, and a width direction moving member connected to the length direction moving member, moved along the length direction of the table by an operation of the length direction moving members, of which the lower electrode is mounted thereto, and the width direction moving member movable along width direction of the table. 
     The length direction moving member may include a first screw shaft disposed on both ends of the table along length direction of the table respectively, a second moving block engaged with and movable along the each first screw shaft, and a first motor (e.g., a servo motor) mounted to a side of the table and selectively rotating the first screw shaft. The first motor may be mounted and configured to supply torque to the each first screw shaft on each side of the table respectively. 
     The width direction moving member may include a second motor, a second screw shaft connected with each of the second moving blocks along the width direction of the table and a third moving block engaged with and movable along the second screw shaft. In particular, the lower electrode is mounted to the third moving block, and the second motor may be mounted to the third moving block and selectively rotates the second screw shaft. More specifically, the lower electrode may be mounted to the third moving block through a cylinder so as to be selectively moved up and down. 
     The upper and lower moving units may be configured to communicate with a controller configured to control operations of the upper and lower moving units. The controller may synchronize positions of the upper electrode and lower electrode, detect a signal from an encoder of the first and second motors, and then synchronize positions of the upper and lower moving units according to the detected signal. 
     A operation method for a spot welding system including an upper moving unit provided with an upper electrode and configured to vary a position of the upper electrode and a lower moving unit mounted separately from the upper moving unit, provided with a lower electrode corresponding to the upper electrode, and configured to vary a position of the lower electrode is also provided. In particular, the operation method for a spot welding system according to one or a plurality of exemplary embodiments of the present invention may include disposing a welding object between the upper electrode and the lower electrode, synchronizing positions of the upper and lower moving units by control of a controller configured to control operation of the upper moving unit and the lower moving unit, and moving the upper and lower moving units of which the positions are synchronized by according to signals received by the controller to welding points of the welding object for welding. 
     According to one or a plurality of exemplary embodiments of the present invention, spot weld may be implemented at high speeds regardless of size of panels by operating and disposing the upper and lower welding electrodes separately. Also, numbers of robots, costs for facilities, maintenance expenditure, space for equipment and so on may be reduced. Productivity and efficiency of welding may also be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a spot welding system according to an exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view of a pushing unit applied to a spot welding system according to an exemplary embodiment of the present invention. 
         FIG. 3  is a top plan view of a lower moving unit applied to a spot welding system according to an exemplary embodiment of the present invention. 
         FIG. 4  is a partial enlarged view of a lower electrode applied to a spot welding system according to an exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SYMBOLS 
       1 : spot welding system 
       3 : upper moving unit 
       5 : lower moving unit 
     P: welding object 
       7 : welding gun 
       9 : robot 
       11 : upper electrode 
       13 : pushing unit 
       15 : gear box 
       17 : pushing actuator 
       19 : first moving block 
       21 : drive motor 
       23 : lower electrode 
       25 : table 
       27 : length direction moving member 
       29 : width direction moving member 
       31 : second moving block 
       33 : first servo motor 
       35 : first screw shaft 
       37 : second screw shaft 
       39 : third moving block 
       41 : second servo motor 
       43 : cylinder 
       45 : controller 
       47 : first control portion 
       49 : second control portion 
       51 : third control portion 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description, only certain exemplary embodiments of to the present invention have been shown and described, simply by way of illustration. 
     However, the size and thickness of each component illustrated in the drawings are arbitrarily shown for ease of description and the present invention is not limited thereto, and the thicknesses of portions and regions are exaggerated for clarity. 
     Additionally, it is understood that the below control features are executed by at least one controller. The term “controller” refers to a hardware device that includes a memory and a processor configured to specifically execute one or more steps that should be interpreted as its algorithmic control structure. The memory is configured to store the algorithmic control structure and the processor is specifically configured to execute said algorithmic control steps to perform one or more processes which are described further below. 
     Further, in the following detailed description, names of constituents, which are in the same relationship, are divided into “the first”, “the second”, etc., but the present invention is not necessarily limited to the order in the following description. 
       FIG. 1  is a perspective view of a spot welding system according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , a spot welding system  1  according to an exemplary embodiment of the present invention includes an upper moving unit  3  and a lower moving unit  5 . During operation, a welding object P is inserted between the upper moving unit  3  and the lower moving unit  5  for welding. Supplying the welding object P between the upper and lower moving units  3  and  5  is performed by a robot, a panel moving apparatus and so on which is not intended part of the present invention. Additionally, those skilled in the in vehicle manufacturing industry would readily understand how to supply robotically the welding object P to the to present invention, and thus detailed description will be omitted. 
     The upper moving unit  3  is provided with a welding gun  7  and a robot  9  to which the welding gun is mounted. In particular, the robot  7  positions the welding gun  7  into its welding position. Scheme and operation of the robot  9  are well known in vehicle industry, and thus detailed description will be omitted. An upper electrode  11  of the welding gun  7  is mounted to a pushing unit  13 , and the pushing unit  13  is mounted to the robot  9 . 
       FIG. 2  is a perspective view of a pushing unit applied to a spot welding system according to an exemplary embodiment of the present invention. Referring to  FIG. 2 , the pushing unit  13  includes a gear box  15 , a pushing actuator  17  and a first moving block  19 . The pushing actuator  17  is connected to a lower portion of the gear box  15 , and the first moving block  19  is slidable up and down under the gear box  15  by operations of the pushing actuator  17  and the gear box  15 . In the gear box  15 , a plurality of gears are disposed for transferring driving torque of the pushing actuator  17  to move the first moving block  19  up and down. The pushing actuator  17  may be operated by a drive motor  21 . The drive motor  21  may be a step motor or a servo motor configured to control rotation speed and rotating direction. The upper electrode  11  is mounted to the first moving block  19 , and the first moving block  19  moves up and down by the operation of the pushing actuator  17  in welding process. 
     Meanwhile, the pushing actuator  17  may be a roller screw actuator configured to change rotation torque of the drive motor  21  to straight motion. The pushing actuator  17  may rotate a screw shaft (not shown) parallel to the pushing actuator  17  through the gear box  15  so as to move the first moving block  19  on the screw shaft up and down. The operation of a roller screw actuator which may be configured as the pushing actuator is well known in the vehicle industry, and thus detailed description will be omitted. 
     The robot  9  provide with the welding gun  7  may position the welding gun  7  to the welding point. The scheme and the operation of the robot  9  are well known to a person skilled in the art, and thus detailed description will be omitted. In this case, a multi axis moving apparatus may be configured as the robot  9 . 
       FIG. 3  is a top plan view of a lower moving unit applied to a spot welding system according to an exemplary embodiment of the present invention, and  FIG. 4  is a partial enlarged view of a lower electrode applied to a spot welding system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1  and  FIG. 3 , the lower moving unit  5  is mounted welding process line separately from the upper moving unit  3 , provided with a lower electrode  23  corresponding to the upper electrode  11 . The lower moving unit  5  includes a table  25 , a length direction moving member  27  and a width direction moving member  29 . The table  25  may be, for example, installed on a floor of a welding process line. 
     The length direction moving members  27  may be disposed both ends of the table  52  along length direction of the table  25  and the each length direction moving member  27  includes a second moving block  31 , a first (servo) motor  33  including an encoder and a first screw shaft  35 . The each second moving block  31  is disposed on each of the first screw shafts  35  disposed along the length direction of the table  25 . 
     Each of the first servo motors  33  transfers torque to each of the first screw shafts  35  respectively, and the second moving block  31  engaged with the first screw shaft  35  moves along the first screw shaft  35  by rotation of the first screw shaft  35 . 
     As shown in the drawing, the first servo motor  33  as a pair may be disposed on the table  25  to supply torque each of the first screw shafts  35  respectively, or one first servo motor  33  may be used for drive the both first screw shafts  35 . 
     The width direction moving member  29  may be connected with the second moving blocks  31  of the length direction moving member  27 , moves along length direction of the table  25  with the second moving block  31 , and the lower electrode  23  may be mounted thereto. The width direction moving member  29  may include a second screw shaft  37 , a third moving block  39  and a second (servo) motor  41  including an encoder. The second screw shaft  37  may be connected with the each second moving blocks  31  along width direction of the table  25 . The third moving block  39  may be engaged with the second screw shaft  37  and move along the second screw shaft  37  by rotation of the second screw shaft  37 , and the lower electrode  23  may be mounted thereto. 
     Referring to  FIG. 4 , the lower electrode  23  may be mounted on the third moving block  39  through a cylinder  43  for moving up and down by operation of the cylinder  43 . The lower electrode  23  may move up and down by the operation of the cylinder  43  corresponding height of welding points of the welding object P. The second (servo) motor  41  may be mounted to second moving block  31  of the length direction moving member  27 , and transfer torque to the second screw shaft  37  for the third moving block  39  to move on the second screw shaft  37 . The lower moving unit  5  may position the lower electrode  23  on table  25  by operating the length direction moving member  27  and width direction moving member  29 . 
     Furthermore, in some exemplary embodiments of the present invention, the upper and lower moving units  3  and  5  may be configured to communicate with a controller  45  that is configured to control the operations of the upper and lower moving units  3  and  5 . 
     In particular, the controller  45  synchronizes positions of the upper electrode  11  mounted to the upper moving unit  3  and lower electrode  23  mounted to the lower moving unit  5 . Thus, the positions of the upper electrode  11  and the lower electrode  23  are synchronized for welding of the welding points of the welding object P. 
     The controller  45  may also include a first control portion  47  controlling the operation of the upper moving unit  3 , a second control portion  49  controlling the operation of the lower moving unit  5 , and a third control portion  51  synchronizing the positions of the upper and lower electrodes  11  and  23 . 
     The third control portion  51  may be configured to detect signals from the encoders of the first and second servo motors  33  and  41 , and then synchronizes positions of the upper and lower moving units  3  and  5  together with the first and second control portions  47  and  49  according to the detected signal. However, operations of the controller  45  can be executed by any means known to those skilled in the art, and thus detailed description will be omitted. Hereinafter, however, the specific operation method of the spot welding system  1  will be discussed. 
     The welding object P is inserted between the upper electrode  11  and the lower electrode  23 . The positions of the upper and lower moving units  3  and  5  where the upper electrode  11  and lower electrode  23  are mounted respectively are synchronized by to the operation of the controller  45  and then the upper and lower moving units  3  and  5  of which the positions are synchronized by the controller  45  are moved to predetermined welding positions of the welding object P for welding. 
     In detail, the welding object P is supplied between the upper electrode  11  and the lower electrode  23  separated from the upper electrode  11  and then the controller  45  synchronizes the positions of the upper and lower moving units  3  and  5 . In doing so, the positions of the upper electrode  11  and the lower electrode  23  correspond. 
     Next the controller  45  controls the operations of the upper and lower moving units  3  and  5  for the upper electrode  11  and the lower electrode  23  to be located to the predetermined welding positions of the welding object P repeatedly until the spot welding process is completed. 
     According to one or a plurality of the exemplary embodiments of the present invention, the upper electrode  11  and the lower electrode  23  are mounted to the upper and the lower moving units  3  and  5  separated from each other, and thus welding process may be implemented with at a high speed regardless of size of the welding object P. That is, a welding gun, connecting an upper electrode and a lower electrode  23 , equipped to a conventional art is not used. And thus welding process may be implemented at high speeds regardless of size of the welding object P. 
     Also, numbers of robots required for welding process may be reduced, and also costs for facilities, maintenance expenditure, space for equipment and so on may be reduced. And Productivity and efficiency of welding may be improved. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.