Process for laser welding resinous members, apparatus for the same and laser-welded resinous product

1. A process for laser welding resinous members, the process comprising the steps of:

overlapping a transparent resinous member on an absorptive resinous member,

the transparent resinous member having a first predetermined shape, and comprising a part including a strip-shaped first weld surface, at least the part being formed of a transparent resin allowing a laser beam to transmit therein,

the absorptive resinous member having a second predetermined shape, and comprising a part including a strip-shaped second weld surface to be welded to the first weld surface, at least the part of the absorptive resinous member being formed of an absorptive resin which absorbs the laser beam; and

irradiating the transparent resinous member with the laser beam, thereby welding an interface between the first weld surface of the transparent resinous member and the second weld surface of the absorptive resinous member as a strip shape, the interface having a weld line welded as a strip shape and comprising linear part neighboring with each other, a major-curvature-radius curved part intervening between the linear parts and a minor-curvature-radius curved part intervening between the linear parts,

wherein an energy averaging device is configured to average the energy of the laser beam acting on a side of the major-curvature-radius curved part and the energy of the laser beam acting on a side of the minor-curvature-radius curved part in the second weld surface of the absorptive resinous member,

wherein the energy averaging device is configured to let the laser beam traverse along a scanning line shifted on a side of the major-curvature-radius curved part with respect to the center line of a strip-shaped width of the weld line,

wherein the energy averaging device is configured to let the laser beam exhibit a cross-sectional energy-density distribution which is axially symmetrical to a scanning direction of the laser beam at the linear parts of the weld line, and swings the laser beam about the axial line of the laser beam synchronously with the scanning with the laser beam at the major-curvature-radius curved part and minor-curvature-radius curved part of the weld line, thereby lowering an energy density at the minor-curvature-radius curved part than that at the major-curvature-radius curved part, and

wherein the energy averaging device is configured to let the laser beam rotate about the axial line of the laser beam by rotating a cylindrical lens or a polarizing plate at the linear parts of the weld line, and lets the laser beam swing about the axial line of the laser beam by swinging the cylindrical lens or the polarization plate at the major-curvature-radius curved part and minor-curvature-radius curved part of the weld line.

2. A process for laser welding resinous members, the process comprising the steps of:

overlapping a transparent resinous member on an absorptive resinous member,

the transparent resinous member having a first predetermined shape, and comprising a part including a strip-shaped first weld surface, at least the part being formed of a transparent resin allowing a laser beam to transmit therein,

the absorptive resinous member having a second predetermined shape, and comprising a part including a strip-shaped second weld surface to be welded to the first weld surface, at least the part of the absorptive resinous member being formed of an absorptive resin which absorbs the laser beam; and

irradiating the transparent resinous member with the laser beam, thereby welding an interface between the first weld surface of the transparent resinous member and the second weld surface of the absorptive resinous member as a strip shape, the interface having a weld line welded as a strip shape and comprising linear part neighboring with each other, a major-curvature-radius curved part intervening between the linear parts and a minor-curvature-radius curved part intervening between the linear parts,

wherein an energy averaging device is configured to average the energy of the laser beam acting on a side of the major-curvature-radius curved part and the energy of the laser beam acting on a side of the minor-curvature-radius curved part in the second weld surface of the absorptive resinous member,

wherein the energy averaging device is configured to let the laser beam traverse along a scanning line shifted on a side of the major-curvature-radius curved part with respect to the center line of a strip-shaped width of the weld line, and

wherein the averaging device is configured to equalize an energy density of the laser beam at the linear parts of the weld line by rotating the laser beam about the axial line of the laser beam at a high revolving speed, and turns off the high-revolving-speed rotation of the laser beam temporarily at the major-curvature-radius curved part and minor-curvature-radius curved part of the weld line so as to swing the laser beam about the axial line of the laser beam synchronously with the scanning with the laser beam, thereby lowering an energy density at the minor-curvature-radius curved part than that at the major-curvature-radius curved part.

3. The process set forth in claim 2 , wherein the energy averaging device is configured to let the laser beam rotate about the axial line of the laser beam by rotating a cylindrical lens or a polarization plate at the linear parts of the weld line, and the energy averaging device is configured to let the laser beam swing about the axial line of the laser beam by swinging the cylindrical lens or the polarization plate at the major-curvature-radius curved part and minor-curvature-radius curved part of the weld line.