Method and apparatus for using multiple laser beams to weld members that are separated by a gap

1. A fusion welding method for butt-welding a first member and a second member, comprising the steps of:

measuring a width of a gap between the first member and the second member along an extending direction of the gap; and

generating a hybrid laser beam by mixing a low-intensity laser beam with a first high-intensity laser beam and a second high-intensity laser beam, the first high-intensity laser beam and the second high-intensity laser beam each having a smaller application area and a higher intensity peak than the low-intensity laser beam, and

moving the hybrid laser beam along the gap to apply the low-intensity laser beam, the first high-intensity laser beam and the second high-intensity laser beam to the gap and a periphery of the gap, an area of the first member to which the low-intensity laser beam is applied, and an area of the second member to which the low-intensity laser beam is applied, respectively,

in the step of moving the hybrid laser beam along the gap, the fusion welding method comprising the steps of:

adjusting an intensity of the low-intensity laser beam to be within a range where a keyhole is not formed in the first member and the second member in the periphery of the gap, depending on a change in the width of the gap;

forming a first keyhole in the first member in the periphery of the gap with the first high-intensity laser beam and the low-intensity laser beam to melt a portion facing the gap of the first member via the first keyhole, and forming a second keyhole in the second member in the periphery of the gap with the second high-intensity laser beam and the low-intensity laser beam to melt a portion facing the gap of the second member via the second keyhole;

filling the gap with melt obtained by melting the portion facing the gap of the first member and melt obtained by melting the portion facing the gap of the second member, and

cooling down a welded part between the first member and the second member with the low-intensity laser beam.

2. The fusion welding method according to claim 1 , wherein in the step of moving the hybrid laser beam along the gap, if there is a change in the width of the gap, the method further comprises the step of:

adjusting an application position of the first high-intensity laser beam so that a distance between the first keyhole and the portion facing the gap of the first member is held constant, and

adjusting an application position of the second high-intensity laser beam so that a distance between the second keyhole and the portion facing the gap of the second member is held constant.

3. The fusion welding method according to claim 1 , wherein in the step of moving the hybrid laser beam along the gap, further comprising the steps of:

increasing the intensity of the low-intensity laser beam so as to increase an amount of the melt of each of the first member and the second member when the width of the gap increases; and

reducing the intensity of the low-intensity laser beam so as to reduce the amount of the melt of each of the first member and the second member when the width of the gap decreases.

4. A fusion welding method for butt-welding a first member and a second member, comprising the steps of:

measuring a width of a gap between the first member and the second member along an extending direction of the gap; and

generating a hybrid laser beam by mixing a low-intensity laser beam with a first high-intensity laser beam and a second high-intensity laser beam, the first high-intensity laser beam and the second high-intensity laser beam each having a smaller application area and a higher intensity peak than the low-intensity laser beam, and moving the hybrid laser beam along the gap to apply the low-intensity laser beam, the first high-intensity laser beam and the second high-intensity laser beam to the gap and a periphery of the gap, an area of the first member to which the low-intensity laser beam is applied, and an area of the second member to which the low-intensity laser beam is applied, respectively,

in the step of moving the hybrid laser beam along the gap, depending on a change in the width of the gap, the fusion welding method comprising the steps of:

adjusting an intensity of the first high-intensity laser beam to be within a range where the first member is not penetrated;

adjusting an intensity of the second high-intensity laser beam to be within a range where the second member is not penetrated; and

melting the first member and the second member in the periphery of the gap with the hybrid laser beam, and filling the gap with melt of the first member and melt of the second member to weld the first member and the second member.

5. The fusion welding method according to claim 4 , wherein in the step of moving the hybrid laser beam along the gap, the method further comprises the steps of:

increasing the intensity of the first high-intensity laser beam so as to increase an amount of the melt of the first member, and

increasing the intensity of the second high-intensity laser beam so as to increase an amount of the melt of the second member, when the width of the gap increases; and

reducing the intensity of the first high-intensity laser beam so as to reduce the amount of the melt of the first member, and

reducing the intensity of the second high-intensity laser beam so as to reduce the amount of the melt of the second member, when the width of the gap decreases.

6. A fusion welding method for lap-welding a first member and a second member, in a case where the first member is a horizontally extending thin plate, the second member is vertically extending foil, the fusion welding method comprising the steps of:

locating the first member vertically above the second member; and,

generating a hybrid laser beam obtained by mixing a low-intensity laser beam with a first high-intensity laser beam and a second high-intensity laser beam, and moving the hybrid laser beam on an upper surface of the first member, thereby

melting the first member with the hybrid laser beam, and filling a gap between the first member and the second member with a lower portion of melt of the first member to weld the first member and an end of the second member, wherein

the first high-intensity laser beam and the second high-intensity laser beam each have a smaller application area and a higher intensity peak than the low-intensity laser beam,

the low-intensity laser beam is applied to the upper surface of the first member,

the first high-intensity laser beam and the second high-intensity laser beam are applied to an outer periphery in an area to which the low-intensity laser beam is applied,

an optical axis of the low-intensity laser beam is arranged between the first high-intensity laser beam and the second high-intensity laser beam,

a sectional shape of the melt of the first member becomes substantially rectangular or trapezoidal when viewed from a traveling direction of the hybrid laser beam,

a lower surface of the first member is brought into contact with the end of the second member.

7. A fusion welding apparatus comprising:

a low-intensity laser beam output unit for outputting a low-intensity laser beam;

a first high-intensity laser beam output unit for outputting a first high-intensity laser beam having a smaller application area and a higher intensity peak than the low-intensity laser beam;

a second high-intensity laser beam output unit for outputting a second high-intensity laser beam having a smaller application area and a higher intensity peak than the low-intensity laser beam;

an optical system for mixing the first high-intensity laser beam and the second high-intensity laser beam on the low-intensity laser beam to generate a hybrid laser beam; and

a blow-off unit for blowing off an inactive gas from a front and rear in a traveling direction of the hybrid laser beam toward a portion to which the hybrid laser beam is applied,

wherein an intensity of the low-intensity laser beam is set so that a keyhole is not formed in a portion to which only the low-intensity laser beam is applied,

an intensity of the first high-intensity laser beam is set so that a keyhole is formed in a portion to which the first high-intensity laser beam and the low-intensity laser beam are applied together,

intensity of the second high-intensity laser beam is set so that a keyhole is formed in an area to which the second high-intensity laser beam and the low-intensity laser beam are applied together, and

foci of the low-intensity laser beam, the first high-intensity laser beam, and the second high-intensity laser beam are set so that the first high-intensity laser beam and the second high-intensity laser beam are distributed to an outer periphery of the low-intensity laser beam with an optical axis of the low-intensity laser beam held between the first high-intensity laser beam and the second high-intensity laser beam.