Abstract:
A laser apparatus for welding is disclosed. The laser apparatus includes: a laser optic head adapted and configured to modify a spot size of a laser beam oscillated by a laser oscillator and to project the laser beam into a joining portion of joining members, wherein the laser optic head is adapted and configured to modify the spot size to selectively perform brazing or welding. A method of selectively brazing or welding according to one or more exemplary embodiments of the present invention includes: providing a laser apparatus of as described herein; and actuating the laser optic head to modify the spot size of the laser beam and project the laser beam into the joining portion of the joining members to selectively perform brazing or welding.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2011-0104654 filed in the Korean Intellectual Property Office on Oct. 13, 2011, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a laser apparatus for welding. More particularly, the present invention relates to a laser apparatus for welding that enables brazing or laser welding that joins two joining members or panels by using a laser beam through one apparatus. 
       BACKGROUND OF THE INVENTION 
       [0003]    Recently, a laser beam is increasingly used in cutting, welding, and heat treatment of metal members due to cost reduction, factory automation, and quality improvement. 
         [0004]    Primary issues required for applying the laser beam are such that energy distribution of the laser beam is uniformized, laser output is controlled so as to maintain a constant heat treatment temperature, shooting speed of the laser beam is optimized so as to satisfy productivity and quality, and energy absorption ratio is maximized. That is, cost reduction and quality improvement can be achieved when applying the laser beam if the primary issues are satisfied. 
         [0005]    Herein, joining method for joining two joining members or panels by using the laser beam is divided into brazing and welding. 
         [0006]    Firstly, brazing is a metal-joining process where the joining members are not melted but a filler metal is melted since non-ferrous metal or non-ferrous metal alloy (e.g., solder or braze) having a lower melting point than the joining members is used as the filler metal. In this case, the molten filler metal is diffused between the joining members by capillary phenomenon and a base metal constituting the joining members is wet by the molten filler metal. After that, if the filler metal and the joining member are cooled, the joining members are joined. 
         [0007]    The laser brazing, compared with spot welding, can enhance degree of design freedom and productivity due to beautiful appearance, reduce cost since there is no need to spray molding or sealer into a joining portion, and improve strength of a vehicle body due to spreading stress of the joining portion. So as to obtain good brazing quality, the panels, focus of the laser beam, and an end of a filler wire should be aligned. 
         [0008]    In addition, the laser welding is a metal-joining process where, in a state that two joining members (panels) are overlapped with each other, the laser beam is shot into a welding portion (joining portion) so as to melt the panels. In this case, a molten metal is pushed to an opposite direction of welding progress by a pressure of plasma occurring around a laser welding portion. After that, the molten metal is solidified and a welding bead is produced such that the joining members (panels) are joined by the welding bead. 
         [0009]    Quality of laser welding is affected by gap size between the joining members. If sufficient space for expanding gasses to pass does not exist, the gas breaks through or caves the welding bead. Therefore, breakage of the welding portion can occur. 
         [0010]    Accordingly, an additional apparatus for applying pressure to or clamping the joining members is essentially required so as to maintain a gap between the joining members. 
         [0011]    A laser apparatus used in the laser brazing or welding includes a laser optic head in which a plurality of lenses is provided. The laser optic head is adapted to shoot the laser beam oscillated by the laser oscillator into the welding portion. 
         [0012]    According to a conventional laser apparatus, an apparatus for supplying the filler metal is essentially required when the brazing, and the additional apparatus for applying pressure to or clamping the joining members is essentially required when welding. Therefore, initial investment cost can increase. 
         [0013]    In a case that the laser brazing and the laser welding are simultaneously used for joining two joining members, one of the brazing and the welding should be performed after the other of the brazing and the welding was performed. Therefore, working hours are very long. 
         [0014]    Because the brazing and the welding cannot be performed by one laser apparatus, manufacturing cost can increase. 
         [0015]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it can 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 
       [0016]    The present invention has been made in an effort to provide a laser apparatus for welding having advantages of reducing manufacturing cost, shortening working hours, and enhancing productivity by enabling of brazing or laser welding that joins two joining members or panels through one apparatus. 
         [0017]    A laser apparatus for welding according to one or more exemplary embodiments of the present invention includes: a laser optic head adapted and configured to modify a spot size of a laser beam oscillated by a laser oscillator and to project the laser beam into a joining portion of joining members, wherein the laser optic head is adapted and configured to modify the spot size to selectively perform brazing or welding. 
         [0018]    In one or more exemplary embodiments of the present invention, the laser apparatus further includes a mounting frame 
         [0019]    In one or more exemplary embodiments of the present invention, the laser apparatus further includes a wire feeder supplying a filler metal into the laser beam projected by the laser optic head so as to perform the brazing. 
         [0020]    In one or more exemplary embodiments of the present invention, the wire feeder is disposed at a side portion of the laser optic head and is mounted at the mounting frame. 
         [0021]    In one or more exemplary embodiments of the present invention, the laser apparatus further includes a roller unit adapted to apply pressure to an upper portion of the joining members so as to control a gap between the joining members when laser welding the joining members. 
         [0022]    In one or more exemplary embodiments of the present invention, the roller unit is mounted at the mounting frame and is movable upwardly or downwardly to the mounting frame. 
         [0023]    In one or more exemplary embodiments of the present invention, the roller unit includes: a mounting bracket mounted at the mounting frame ahead of the laser optic head; an operating cylinder provided with an operating rod and mounted at a side portion of the mounting bracket, the operating rod being mounted at the operating rod so as to be movable upwardly or downwardly; and a roller connected to a front end of the operating rod, movably mounted at the operating cylinder through guide means, and adapted to slidably contact on an upper surface of the joining member according to the movement of the operating rod and to apply pressure to the joining members. 
         [0024]    In one or more exemplary embodiments of the present invention, the guide means includes: a rail mounted at a surface of the operating cylinder along a length direction thereof; and a rail block slidably mounted on the rail, connected to the operating rod, and having a front end at which the roller is mounted through a connecting block. 
         [0025]    In one or more exemplary embodiments of the present invention, the roller unit further includes an air blower for removing spatters when laser welding. 
         [0026]    In one or more exemplary embodiments of the present invention, the laser optic head includes: a head housing mounted at the lower portion of the mounting frame, and provided with an upper portion having a side connected to an optical fiber cable for transmitting the laser beam oscillated by the laser oscillator and a lower portion formed of a laser shooting hole; a collimation lens mounted at an extended portion of the head housing so as to be movable upwardly or downwardly through driving means and adapted to control the size of the laser beam oscillated by the laser oscillator; a first reflector mounted at a side portion in the head housing on a vertical line of the collimation lens and adapted to totally reflect the laser beam in a horizontal direction; a second reflector mounted at the other side in the head housing on a horizontal line of the first reflector and adapted to totally reflect the laser beam reflected by the first reflector in a vertical direction; and a focus lens mounted corresponding to the laser shooting hole of the head housing on the vertical line of the second reflector, and adapted to form a focus of the laser beam reflected by the second reflector and to shoot the laser beam into the joining portion of the joining members. 
         [0027]    In one or more exemplary embodiments of the present invention, the driving means includes: a guide rail mounted at both sides of an interior circumference of the extended portion and adapted to guide the collimation lens; a drive motor mounted at an exterior of the extended portion and having a rotation shaft facing downwardly; a driving screw connected to the rotation shaft of the drive motor; and a screw block engaged with the driving screw at the exterior of the extended portion in a state of being connected to the collimation lens. 
         [0028]    In one or more exemplary embodiments of the present invention, the drive motor is a step motor, rotation speed and rotating direction of which can be controlled. 
         [0029]    A method of selectively brazing or welding according to one or more exemplary embodiments of the present invention includes: providing a laser apparatus of as described herein; and actuating the laser optic head to modify the spot size of the laser beam and project the laser beam into the joining portion of the joining members to selectively perform brazing or welding. 
         [0030]    In one or more exemplary embodiments of the present invention, the spot size approximates a width of the joining portion. 
         [0031]    In one or more exemplary embodiments of the present invention, the method further includes supplying a filler metal into the laser beam projected by the laser optic head. 
         [0032]    In one or more exemplary embodiments of the present invention, the method further includes applying pressure to an upper portion of the joining members so as to control a gap between the joining members when laser welding the joining members. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  is a perspective view of a laser apparatus for welding according to an exemplary embodiment of the present invention. 
           [0034]      FIG. 2  is another perspective view of a laser apparatus for welding according to an exemplary embodiment of the present invention. 
           [0035]      FIG. 3  is a cross-sectional view of a laser optic head applied to a laser apparatus for welding according to an exemplary embodiment of the present invention. 
           [0036]      FIG. 4  is an operational state diagram of a laser optic head applied to a laser apparatus for welding according to an exemplary embodiment of the present invention. 
           [0037]      FIG. 5  is an operational state diagram of a laser apparatus for welding according to an exemplary embodiment of the present invention. 
       
    
    
       [0038]    The following legend of the reference numerals is provided for convenience: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                  1: laser apparatus 
                  3: arm of robot 
               
               
                   
                  5: mounting frame 
                 10: laser optic head 
               
               
                   
                 11: laser oscillator 
                 13: head housing 
               
             
          
           
               
                   
                 14: extended portion 
                 15: laser shooting hole 
               
             
          
           
               
                   
                 16: collimation lens 
                 17: first reflector 
               
             
          
           
               
                   
                 18: second reflector 
                 19: focus lens 
               
             
          
           
               
                   
                 20: driving means 
                 21: guide rail 
               
             
          
           
               
                   
                 22: drive motor 
                 23: driving screw 
               
             
          
           
               
                   
                 24: screw block 
                 25: controller 
               
             
          
           
               
                   
                 30: wire feeder 
                 40: roller unit 
               
               
                   
                 41: mounting bracket 
                 43: operating cylinder 
               
               
                   
                 45: rail 
                 47: rail block 
               
               
                   
                 48: connecting block 
                 49: roller 
               
               
                   
                 50: air blower 
                 60: sensor 
               
             
          
           
               
                   
                 P: joining member 
                 B: laser beam 
               
               
                   
                 G: gap 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0039]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0040]    Exemplary embodiments described in this specification and drawings are just exemplary embodiments of the present invention. It is to be understood that there can be various modifications and equivalents included in the spirit of the present invention at the filing of this application. 
         [0041]      FIG. 1  is a perspective view of a laser apparatus for welding according to an exemplary embodiment of the present invention;  FIG. 2  is another perspective view of a laser apparatus for welding according to an exemplary embodiment of the present invention; and  FIG. 3  is a cross-sectional view of a laser optic head applied to a laser apparatus for welding according to an exemplary embodiment of the present invention. 
         [0042]    Referring to the drawings, a laser apparatus  1  for welding according to an exemplary embodiment of the present invention enables of brazing or laser welding that joins two joining members or panels through one apparatus. Therefore, manufacturing cost and working hours can be reduced and productivity can be improved. 
         [0043]    For achieving these purposes, the laser apparatus  1  for welding according to an exemplary embodiment of the present invention, as shown in  FIG. 1  and  FIG. 2 , includes a mounting frame  5 , a laser optic head  10 , a wire feeder  30 , and a roller unit  40 , and each element will be described in detail. 
         [0044]    Firstly, the mounting frame  5  is mounted at a front end of an arm of a robot  3 . 
         [0045]    In the present exemplary embodiment, the laser optic head  10  is mounted at a lower portion of the mounting frame  5 , changes a spot size of a laser beam B oscillated by a laser oscillator  11 , and projects the laser beam B into a joining portion of the joining members P. 
         [0046]    The laser optic head  10 , as shown in  FIG. 3 , includes a head housing  13 , a collimation lens  16 , first and second reflectors  17  and  18 , and a focus lens  19 . 
         [0047]    The head housing  13  substantially has a rectangular shape having a space therein. An upper end of the head housing  13  is mounted at the lower portion of the mounting frame  5 . 
         [0048]    An extended portion  14  is formed at a side of an upper portion of the head housing  13 , and an optical fiber cable is connected to the extended portion  14 . The optical fiber cable is adapted to transmit the laser beam oscillated by the laser oscillator  11 . A laser shooting hole  15  is formed at a lower portion of the head housing  13 . 
         [0049]    The collimation lens  16  is mounted at the extended portion  14  of the head housing  13  and is movable upwardly or downwardly through driving means  20 . The collimation lens  16  is adapted to control the size (spot size) of the laser beam B oscillated by the laser oscillator  11 . 
         [0050]    Herein, the driving means  20  include a guide rail  21 , a drive motor  22 , a driving screw  23 , and a screw block  24 , and each element will be described in detail. 
         [0051]    The guide rail  21  is mounted at both sides of an interior circumference of the extended portion  14  and is adapted to guide the collimation lens  16  stably. 
         [0052]    In the present exemplary embodiment, the drive motor  22  is mounted at an exterior of the extended portion  14  and has a rotation shaft facing downwardly. The driving screw  23  is connected to the rotation shaft of the drive motor  22 . 
         [0053]    Herein, the drive motor  22  is electrically coupled with a controller  25 , and can be a step motor. Rotation speed and rotating direction of the drive motor  22  can be controlled according to an output signal of the controller  25 . 
         [0054]    The driving screw  23  is connected to the rotation shaft of the drive motor  22  so as to rotate according to rotation of the drive motor  22 . 
         [0055]    In addition, the screw block  24  is engaged with the driving screw  23  at the exterior of the extended portion  14  in a state of being connected to the collimation lens  16 . 
         [0056]    Therefore, if the drive motor  22  is operated by a control signal of the controller  25 , the driving screw  23  rotates clockwise or counterclockwise and the screw block  24  engaged with the driving screw  23  moves upwardly or downwardly on the driving screw  23 . 
         [0057]    Accordingly, the collimation lens  16  connected to the screw block  24  slides upwardly or downwardly along the guide rail  21  in the extended portion  14 . 
         [0058]    In the present exemplary embodiment, the first reflector  17  is mounted at a side portion in the head housing  13  on a vertical line of the collimation lens  16  and is adapted to totally reflect the laser beam B in a horizontal direction. 
         [0059]    In addition, the second reflector  18  is mounted at the other side portion in the head housing  13  on a horizontal line of the first reflector  17  and is adapted to totally reflect the laser beam B reflected by the first reflector  17  in a vertical direction. 
         [0060]    That is, the first reflector  17  and the second reflector  18  reflects the laser beam B oscillated by the laser oscillator  11  and forming the focus controlled through the collimation lens  16  respectively in the horizontal and vertical direction so as to lead the laser beam B into the laser shooting hole  15 . 
         [0061]    In the present exemplary embodiment, the focus lens  19  is mounted corresponding to the laser shooting hole  15  of the head housing  13  on the vertical line of the second reflector  18 . 
         [0062]    The focus lens  19  is adapted to form the focus F of the laser beam B reflected from the second reflector  18  and to shoot the laser beam B of high power into the joining portion of the joining members P. 
         [0063]    The laser optic head  10  changes the spot size of the laser beam B according to laser brazing or laser welding of the joining members P. These processes will be described in detail, referring to  FIG. 4 . 
         [0064]      FIG. 4  is an operational state diagram of a laser optic head applied to a laser apparatus for welding according to an exemplary embodiment of the present invention. 
         [0065]    Referring to  FIG. 4 , the screw block  24  of the driving means  20  is disposed on the driving screw  23  close to the drive motor  22  when laser brazing the joining member P. Therefore, the collimation lens  16  is positioned at an upper portion of the extended portion  14 . 
         [0066]    Accordingly, a diameter of the laser beam B oscillated by the laser oscillator  11  is formed to be small by the collimation lens  16  disposed at the upper portion of the extended portion  14  of the head housing  13 . The laser beam B passes through the focus lens  19  as a consequence of being reflected by the first and second reflectors  17  and  18 . 
         [0067]    Then, the laser beam B forms the focus F at a position apart from and above the joining members P by the focus lens  19 , and the laser beam B spreads toward the joining members P with respect to the focus F so as to be shot into joining members P with the diameter thereof increased. Therefore, the laser brazing is performed. 
         [0068]    On the contrary, the driving screw  23  rotates through the operation of the drive motor  22  and the screw block  24  moves downwardly from an initial position when laser welding joining members P. Therefore, the collimation lens  16  moves downwardly along the guide rail  21  together with the screw block  24  and is disposed at a lower portion of the extended portion  14 . 
         [0069]    Accordingly, the diameter of the laser beam B oscillated by the laser oscillator  11  becomes larger than that of the laser beam B at the brazing by the collimation lens  16  positioned at the lower portion of the extended portion  14 . The laser beam B passes through the focus lens  19  as a consequence of being reflected by the first and second reflectors  17  and  18 . 
         [0070]    Then, the laser beam B is shot into the joining members P with the focus F formed on a surface of the joining portion of the joining members P by the focus lens  19 . Therefore, the laser welding is performed. 
         [0071]    In the present exemplary embodiment, the wire feeder  30  is adapted to supply a filler metal into the laser beam B shot from the laser optic head  10 . The wire feeder  30  is disposed at a side of the laser optic head  10  and is mounted at the mounting frame  5 . The filler metal is melted by the laser beam B. 
         [0072]    The wire feeder  30  is used only when the laser brazing. That is, the filler metal supplied into the laser beam B shot from the laser optic head  10  is melted and the joining members P are brazed by the molten filler metal. 
         [0073]    In addition, the roller unit  40 , as shown in  FIG. 2 , is adapted to apply pressure to an upper portion of the joining members P so as to control a gap between the joining members P when the laser welding of the joining members P. The roller unit  40  is mounted at the mounting frame  5  ahead of the laser optic head  10  and is movable upwardly or downwardly to the mounting frame  5 . 
         [0074]    The roller unit  40  includes a mounting bracket  41 , an operating cylinder  43 , and a roller  49 . 
         [0075]    The mounting bracket  40  is mounted at the mounting frame  5  ahead of the laser optic head  10 . 
         [0076]    Herein, the mounting bracket  41  can be slanted with reference to the mounting frame  5  by a predetermined angle. 
         [0077]    In the present exemplary embodiment, the operating cylinder  43  includes an operating rod R and is mounted at a side portion of the mounting bracket  41 . The operating rod R is mounted at the operating cylinder  43  and is movable upwardly or downwardly with reference to the operating cylinder  43 . 
         [0078]    In addition, the roller  49  is connected to a front end of the operating rod R of the operating cylinder  43 , and is movably mounted at the operating cylinder  43  through guide means  42 . Therefore, the roller  49  is slidably contacted to an upper surface of the joining members P depending on movement of the operating rod R so as to apply pressure to the joining members P. 
         [0079]    Herein, the guide means  42  includes a rail  45  mounted at a surface of the operating cylinder  43  along a length direction thereof and a rail block  47  slidably mounted on the rail  45 . The rail block  47  is connected to the operating rod R of the operating cylinder  43 , and the roller  49  is mounted at a front end of the rail block  47  through a connecting block  48 . 
         [0080]    The guide means  42  guides movement of the roller  49  stably when the operating rod R moves upwardly or downwardly. 
         [0081]    In addition, the guide means  42  supports the roller  49  so as to apply pressure to the joining members P stably when the roller  49  applies the pressure to the joining members P. 
         [0082]    In the present exemplary embodiment, the roller unit  40  further includes an air blower  50  beside the roller  49  so as to remove spatters generated when the laser welding. 
         [0083]    When the joining members P are welded by the laser beam B shot by the laser optic head  10 , the air blower  50  prevents the spatters generated from the joining members P from being attached to a surface of the joining member P or the focus lens  19  of the laser optic head  10 . 
         [0084]    Meanwhile, a sensor  60  is mounted at the mounting bracket  41  according to the present exemplary embodiment. The sensor  60  is used for inspecting welding quality when the laser welding. 
         [0085]    Hereinafter, operation of the laser apparatus  1  for welding according to an exemplary embodiment of the present invention will be described in detail. 
         [0086]      FIG. 5  is an operational state diagram of a laser apparatus for welding according to an exemplary embodiment of the present invention. 
         [0087]    As shown in  FIG. 4 , the laser apparatus  1  for welding according to an exemplary embodiment of the present invention changes a position of the collimation lens  16  in the head housing  13  by the driving means  20  when laser brazing of the joining members P. Therefore, the diameter of the laser beam B oscillated by the laser oscillator  11  is controlled to perform the brazing of the joining members P. 
         [0088]    At this time, the wire feeder  30  supplies the filler metal into the laser beam B continuously until the brazing is completed such that the brazing of the joining members P is smoothly performed. 
         [0089]    In addition, the collimation lens  16 , as shown in  FIG. 4 , is moved to the lower portion of the extended portion  14  by the driving means  20  when the laser welding of the joining members P is performed. 
         [0090]    Therefore, the focus F of the laser beam B, as shown in &lt;S 1 &gt; of  FIG. 5 , is positioned on the surface of the joining portion of the joining member P. 
         [0091]    In this case, the gap G 1  formed between the joining member P 1  and the joining member P 2  is larger than that required for the laser welding. 
         [0092]    At this state, the operating rod R of the roller unit  40  moves downwardly and the rail block  47  as well as the operating rod R slides downwardly along the rail  45 . 
         [0093]    Then, the roller  49  mounted at the front end of the rail block  47  applies load of the operating cylinder  43  to the joining members P 1  in a state of being slidably contacted on the surface of the joining members P 1 . 
         [0094]    Therefore, the gap G 2  formed between the joining member P 1  and the joining member P 2  becomes smaller than the gap G 1  shown in &lt;S 1 &gt; of  FIG. 5 . 
         [0095]    That is, the roller unit  40  controls a size of the gap formed between the joining member P 1  and the joining member P 2  to a size required for the laser welding and maintains the gap to have a constant size during the laser welding. Therefore, welding quality can be improved. 
         [0096]    As described above, the laser apparatus  1  for welding according to an exemplary embodiment of the present invention enables of brazing or laser welding that joins two joining members P or the panels through one apparatus. Therefore, manufacturing cost and working hours can be reduced and productivity can be improved. 
         [0097]    In addition, (i) it is possible to change the spot size of the laser beam B, (ii) the wire feeder  30  enables supplying of filler metal, and (iii) the roller unit  40  can apply pressure to the joining members so as to maintain the gap G between the joining members P. Therefore, laser brazing and welding can be simultaneously performed without an additional apparatus and at a higher quality. 
         [0098]    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.