SYSTEMS FOR AND METHOD OF WELDING WITH A LASER BEAM POINT LINEAR PROFILE OBLIQUELY ORIENTED RELATIVE TO THE TRAVEL DIRECTION

Abstract

A laser welding system is provided including a laser source configured to produce at least one laser beam, beam modifying means configured to split the at least one laser beam, directing means, and controlling means configured to control the directing means. The controlling is configured to control the directing means to cause the split laser beam to form at least two heat source points on the target, the heat source points maintaining a linear profile, and move the at least two heat source points in a travel direction along the target, wherein the linear profile forms a predetermined, oblique angle relative to the travel direction.

Claims

1.-11. (canceled)

12. A method for welding, the method comprising: splitting a laser beam to form at least three heat source points on a target, the heat source points maintaining a linear profile; directing the at least three heat source points in a travel direction along the target, wherein the linear profile forms a predetermined, oblique angle relative to the travel direction.

13. The method according to claim 12, comprising applying a force to the target on at least a portion of an area on the target heated by at least one of the at least three heat source points.

14. The method according to claim 12, wherein the directing comprises manipulating one or more optical elements such that the split laser beams are reflected.

15. The method according to claim 13, wherein the applying comprises directing a jet of gas from outside the target toward an inner portion of the target, the gas comprising an inert combustion-inhibiting gas.

16. The method according to claim 12, wherein the splitting results in at least one primary output beam and at least two subsidiary output beams, the at least one primary output beam having higher power than the at least two subsidiary beams.

17. The method according to claim 16, wherein the directing results in the at least one primary output beam forming a primary heat source point between two subsidiary heat source points.

18. The method according to claim 17, further comprising: when welding an end portion of an elongate battery case and cover, positioning a majority of the at least one primary heat source point over a gap to be closed by welding during the moving; and when welding an elongate portion of the elongate battery case and cover, positioning a majority of the at least one primary heat source point over the case.

19. The method for welding according to claim 12, wherein the splitting results in no more than five output beams.

20. A battery having an elongate battery case and cover welded according to the method of claim 12, such that the cover is welded to the elongate battery case.

21. A laser welding system, comprising: a laser source configured to produce at least one laser beam; a beam modifier configured to split the at least one laser beam; one or more optical elements configured to direct the split laser beam; a controller configured to control the one or more optical elements to: cause the split laser beam to form at least three heat source points on the target, the heat source points maintaining a linear profile, a midpoint of the linear profile formed by the at least three heat source points comprises a primary heat point source having a higher power than at least two subsidiary heat source points, the primary heat source point being positioned between the at least two subsidiary heat source points, move the at least three heat source points in a travel direction along the target, wherein the linear profile forms a predetermined, oblique angle relative to the travel direction.

22. The laser welding system according to claim 21, comprising a gas supply configured to impinge gas upon a target.

23. The laser welding system according 22, wherein the controller is configured to control the gas supply such that a force is applied to at least a portion of the target heated by at least one of the at least three heat source points

24. The laser welding system according to claim 21, wherein the beam modifier comprises a diffractive optical element.

25. The laser welding system according to claim 21, wherein the target comprises an elongate battery case and cover of a battery.

26. (canceled)

27. The laser welding system according to claim 25, wherein a majority of the primary heat source point is superposed on the battery case, at least during irradiation of longitudinal portions of the elongate battery case and cover.

28. The laser welding system according to claim 22, wherein the gas supply is configured to supply an inert, combustion-inhibiting gas.

29. The laser welding system according to claim 22, wherein the gas supply is applied in a direction from a position outside of the target toward an inner portion of the target.

30. The laser welding system according to claim 21, wherein the beam modifier is configured to split the laser beam into no more than five output beams.

31. (canceled)

32. The laser welding system according to claim 22, wherein the primary heat source point is located in proximity to a midpoint of the linear profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 A shows a prior art welding profile;

[0040] FIG. 1B is a diagram showing a scanning technique for welding using the welding profile of FIG. 1A;

[0041] FIG. 2A shows an exemplary welding system according to embodiments of the present disclosure;

[0042] FIG. 2B is an exemplary representation of a target in proximity to the welding system shown at FIG. 2A;

[0043] FIGS. 3A-C are exemplary linear profiles of heat source points according to embodiments of the present disclosure;

[0044] FIG. 4 is an exemplary linear profile at a particular orientation formed using a beam shaper;

[0045] FIG. 5 is a diagram representing exemplary positioning of a linear profile relative to a target during a welding operation;

[0046] FIGS. 6A-F show a representation of sequential steps in an exemplary welding process; and

[0047] FIG. 7 is a block diagram describing an exemplary method according to embodiments of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

[0048] Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0049] FIG. 1A shows a prior art welding profile, while FIG. 1B is a diagram showing a scanning technique for welding using the welding profile of FIG. 1A. As described above, at least five heat source points 30 have been used in prior art systems, and this can result in excess energy consumption, as well as production of various undesirable “ghost beams” 33.

[0050] When scanning the weld line using the profile 35 of FIG. 1A, as shown at FIG. 1B, it is possible that ghost beams 33 may pass between the gap to be welded and enter the internal portion of the target 2. This can lead to undesirable effects.

[0051] FIG. 2A shows an exemplary welding system 1 configured to remedy the above problems according to embodiments of the present disclosure while FIG. 2B is an exemplary representation of a target in proximity to the welding system shown at FIG. 2A. Welding system 1 may include a laser source 3, a collimator 4, a beam modifier 5 (e.g., a diffractive optical element (DOE)), a directing unit 14, a gas supply 20, and a controller 12. One of skill in the art will understand that more or fewer components may be present without departing from the scope of the present disclosure.

[0052] Laser source 3 includes any suitable device for providing a laser beam, for example, a laser oscillator. Laser source 3 may provide laser light at any wavelength and energy level suitable for welding materials associated with target 2. For example, suitable laser sources include, ruby lasers, Nd:YAG lasers, fiber lasers, gas lasers (helium, nitrogen, carbon dioxide), etc.

[0053] Collimator 4 may be optionally provided and can be configured to collimate laser light provided by laser source 3. For example, laser light provided by laser source 3 may pass through a delivery medium 42 (e.g., optical fiber) to arrive at a desired location. Upon exiting delivery medium 42, the laser light may be collimated to desirably align the light waves and narrow the beam before passing through additional optical elements, e.g., beam modifier 5. Collimator 4 may therefore be any lens, mirror, or other suitable element for collimating laser light.

[0054] FIGS. 3A-C are exemplary linear profiles of heat source points according to embodiments of the present disclosure. Beam modifier 5 may comprise one or more optical elements configured to split a laser beam provided by laser source 3 into a desired number of output laser beams and to shape the output laser beams into a desired profile. For example, beam modifier 5 may comprise a diffraction element (e.g., a diffraction grating) fabricated to function as a beam splitter to split an incident laser beam provided by laser source 3 into five or fewer output laser beams.

[0055] In addition, beam modifier 5 may comprise a beam shaper configured to arrange the output beams to form a linear profile, i.e., the heat source points 30 resulting from incidence upon target 2 being aligned linearly as shown at FIGS. 3A-C. For example, one suitable beam shaper may be an FBS-Gauss-to-Top Hat Focus Beam Shaper by TOPAG. One of skill in the art will recognize that this device is exemplary only.

[0056] Importantly, when discussing the output beams resulting from the split laser beam, any resulting higher order diffraction beams referred to as “ghost beams 33” (i.e.,) are not to be taken into consideration. In other words, “output beam(s)” is used to refer to the intended output of beam modifier 5, and not unintended ghost beams 33 formed as a result of splitting the laser beam using beam modifier 5.

[0057] Heat source points 30 resulting from output beams of beam modifier 5 may have greater or lesser incident power based on, for example, a diffractive order associated with each of heat source points 30 and diffraction efficiency of beam modifier 5, among others. For example, a primary heat source point 31 having a diffractive order of 0 may be positioned between two or more subsidiary heat source points 32 having a diffractive order greater than 0 (e.g., 1, 2, etc.) (e.g., at a midpoint of the linear profile).

[0058] Returning to FIGS. 2A-B, directing unit 14 is configured to perform scanning, i.e., directing of one or more output laser beams to a desired location to perform a welding operation. Therefore, directing unit 14 may include a controller 12 and one or more optical elements 7 configured to direct one or more laser beams to and along a weld line 9 of target 2.

[0059] Importantly, while controller 12 is discussed within the context of directing unit 14, one of skill in the art will recognize that controller 12 may be integrated with directing unit 14 (i.e., a single structure) or may be provided separately from directing unit 14. One of skill will further recognize that portions of controller 12 may be present with directing unit 14 while other portions of controller 12 are implemented at a location remote from directing unit 14. Any such configurations are intended to be covered by the present disclosure.

[0060] Controller 12 may comprise any suitable control device capable of generating and sending commands to directing device 14 to accomplish a desired welding task. For example, controller 12 may comprise a PIC based controller, a RISC based controller, etc. Controller 12 may further be configured to interface with one or more networks, e.g., LAN, WAN, Internet, cellular, etc. so as to receive instructions via the network.

[0061] According to embodiments of the present disclosure, one exemplary directing unit 14 and controller 12 combination may comprise a Galvanoscanner, such as, for example, a MIRAMOTION (Y-E data). This exemplary device is not intended to be limiting, however, and any other suitable device may be implemented.

[0062] Optical elements 7 may include, for example, one or more mirrors, half mirrors, lenses, mirrored lenses, fibers, etc. suitable for manipulating light. For example, optical elements 7 may include a first mirror 8 positioned at a 45 degree angle relative to a laser beam so as to reflect light perpendicular to the incident laser beam. A scanning mirror 11 may also be provided and configured to direct the laser beam resulting from first mirror 8 in a travel direction T along weld line 9 of target 2. One of skill will recognize that the described configuration is exemplary only, and that more or fewer optical components 7 may be present. For example, one or more lenses 17 and protective coverings may be present to focus output laser beams.

[0063] In addition, directing unit 14 may comprise one or more elements designed to manipulate optical elements 7 in an automated manner. For example, one or more servo motors (not shown) may be provided and configured to rotate, and/or otherwise manipulate optical elements 7 (e.g., scanning mirror 11) so as to perform a desired scanning operation during welding.

[0064] FIG. 4 is an exemplary linear profile at a particular orientation formed using, for example, a beam shaper. Such a linear profile may be manipulated by directing unit 14 controlled by controller 12, for example, based on predetermined instructions programmed within controller 12.

[0065] Directing unit 14 may also be configured to orient linear profile 60 associated with output laser beams and heat source points 30, for example, during scanning. As noted, during scanning, directing unit 14 is configured to cause heat source points 30 to travel along a weld line 9 of target 2. During such movement, directing unit 14 may orient linear profile 60 of heat source points 30 at an predetermined oblique angle a relative to the direction of travel T (i.e., movement direction) along weld line 9 of target 2. As used herein, “travel direction” is intended to mean the direction of movement of heat source points 30 along a weld line 9 of target 2 as directed by directing unit 14.

[0066] Because the linear profile of heat source points 30 forms oblique angle a relative to the travel direction T, a leading heat source point 37 and a trailing heat source point 39 may be present, with one or more additional heat source points 30 (e.g., primary heat source point 31) located between leading heat source point 37 and trailing heat source point 39. Therefore, each heat source point 30 has a separation distance D.sub.S as measured along the travel direction T of the linear profile from a previous or subsequent heat source point 30, as well as an offset distance D.sub.O relative to a previous or subsequent heat source point 30 as measured perpendicular to the travel direction T, as shown at FIGS. 3A-C.

[0067] FIG. 5 is a diagram representing exemplary positioning of a linear profile relative to a target during a welding operation. As shown, as linear profile 60 of heat source points 30 travels along weld line 9 of target 2, leading heat source point 37 is incident upon a portion of target 2 forming a portion of melt pool 40, followed in time by, for example, primary heat source point 31, at an offset distance D.sub.O from the first portion by a function of angle a (i.e., D.sub.O=D.sub.S/Tan α), and finally by trailing heat source point 39.

[0068] Such a configuration allows leading heat source point 37 to irradiate and heat a portion of target 2 to begin formation of melt pool 40 (e.g., to begin melting material associated with target 2), followed at separation distance D.sub.S by a subsequent heat source point 30 (e.g., primary heat source point 31), the subsequent heat source point 30 irradiating and heating at offset distance D.sub.O in an overlapping manner within melt pool 40 formed by leading heat source point 37, and thereby further expanding a width W of melt pool 40. Such an expansion of melt pool 40 continues until passage of trailing heat source point 39.

[0069] According to embodiments of the present disclosure, during welding of an elongate portion of target 2, the linear profile of heat source points 30 may be arranged at an angle a between about 20 and 80 degrees relative to the direction of travel T of heat source points 30 along the weld line 9 of target 2. Further, during welding of such an elongate portion, it may be desirable to position linear profile 60 of heat source points 30 such that leading heat source point 37 irradiates a portion closest to the an outer portion of target 2 (i.e., an outboard portion of target 2). For example, where a battery case 15 and cover 10 comprise target 2, during welding of an elongate side of case 15 and cover 10, linear profile 60 of heat source points 30 can be arranged such that leading heat source point 37 irradiates a portion on case 15 while trailing heat source point 39 irradiates a portion on cover 10. Primary heat source point 31, positioned substantially at the center between trailing heat source point 39 and leading heat source point 37, may be positioned substantially over case 15 during such elongate portion welding.

[0070] Further, it may be desirable during welding of other portions of target 2 (e.g., end portions of battery case 15 and cover 10) to position linear profile 60 of heat source points 30 such that leading heat source point 37 irradiates a portion of cover 10 (i.e., an inboard portion of target 2), while trailing heat source point 39 irradiates a portion of case 15. One of skill in the art will recognize that the configuration described above is exemplary only and multiple such configurations are available depending on, e.g., target 2, desired melt pool 40, etc. In addition, oblique angle a may also be varied based on a position along weld line 9 of target 2. Any such configuration is intended to fall within the scope of the present disclosure.

[0071] Gas supply 20 is configured to apply a force to at least a portion of target 2 heated by heat source points 30. Therefore, gas supply may be configured to move in travel direction T along with linear profile 60 during a welding operation, e.g., based on commands from controller 12 to a servo motor operatively connected to gas supply 20.

[0072] According to some embodiments, a force applied by gas supply 20 may be directed from a region outside target 2 towards an inner region of target 2. For example, where target 2 comprises a case 15 and cover 10 for a battery, gas supply 20 may cause a force to be applied in a direction from case 15 toward cover 10 as shown at FIG. 5.

[0073] Gas supply 20 may include one or more nozzles, diffusers, and/or other suitable devices for creating, for example, a gas jet that may impinge upon target 2 at least at a portion where melt pool 40 remains substantially fluid. According to some embodiments, gas supply 20 may include a supply of compressed gas (not shown), e.g., an inert combustion-inhibiting gas (e.g., CO.sub.2) that when decompressed through a nozzle may provide a gas jet configured to exert force on melt pool 40 formed by heat source points 30 on target 2. By exerting such a force, a portion of the molten material in melt pool 40 may be caused to flow, for example, in a direction from case 15 toward cover 10. Such flow may therefore assist in closing a gap to be welded and may further strengthen the weld. Because the gap may be closed as a result of the flowed molten material, the risk of subsequent heat source points 30 entering internal portions of the battery is significantly reduced.

[0074] FIGS. 6A-F shows top and cross-sectional representations along plane AA of an exemplary welding process according to embodiments of the present disclosure. As shown at FIG. 6A, prior to scanning by heat source points 30, a gap 55 exists between a case 15 and cover 10 of a battery. As leading heat source point 37 passes over position AA of target 2 (e.g., case 15), a melt pool 40 begins to form as shown at FIG. 6B. Gas supply 20 then exerts a force upon melt pool 40 to cause flow of melt pool 40 toward gap 55 as shown at FIG. 6C. Scanning continues and primary heat source point 31 irradiates at AA at offset D.sub.O thereby further enlarging melt pool 40, and as shown at FIG. 6D, gas supply 20 continues to exert force to cause melt pool 40 to flow. Scanning continues and trailing heat source point 39 arrives at position AA at offset D.sub.O′ thereby continuing enlargement of melt pool 40, as gas supply 20 continues to exert force as shown at FIG. 6E. Finally, as shown at FIG. 6F the welding process is complete at position AA and gap 55 has been closed.

[0075] FIG. 7 is a flow chart 100 demonstrating an exemplary method for laser welding according to embodiments of the present disclosure. A laser beam may initially be split into several output laser beams so as to create at least two heat source points 30 on target 2 (step 105). As noted above heat source points 30 may form a linear profile.

[0076] Heat source points 30 may then be directed in a travel direction along a weld line 40 of target 2 (step 110). During such directing, linear profile 60 formed by heat source points 30 may maintain a predetermined, oblique angle a relative to travel direction T.

[0077] As heat source points 30 irradiate a portion of target 2, a force may be applied to weld pool 40 on target 2 in an area heated by at least one of the heat source points 30 (step 115). As noted above, such a force may be exerted by a gas stream, e.g., gas supply 20, or any other suitable manner.

[0078] One of skill in the art will recognize that variations may be made to structures and methods described herein. For example, while exemplary embodiments have been discussed using a leading heat source point 37, primary heat source point 31, and trailing heat source point 39, additional heat source points 30 may be provided as desired, for example where width of target 2 renders welding difficult without additional heat source points 30.

[0079] Throughout the description, including the claims, the term “comprising a” should be understood as being synonymous with “comprising at least one” unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms “substantially” and/or “approximately” and/or “generally” should be understood to mean falling within such accepted tolerances.

[0080] Where any standards of national, international, or other standards body are referenced (e.g., ISO, etc.), such references are intended to refer to the standard as defined by the national or international standards body as of the priority date of the present specification. Any subsequent substantive changes to such standards are not intended to modify the scope and/or definitions of the present disclosure and/or claims.

[0081] Although the present disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure.

[0082] It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.