Hold-down device, laser welding device and laser welding process

Abstract

The present invention relates to a hold-down device (1) for pressing down a first component (2) onto a second component (3) to be welded thereto. What is essential to the invention is - that the hold-down device (1) has a base body (4) with two parallel grooves (7) along two sides (5, 6), - that in each groove (7) a pressure ball (8) or a pressure roller is mounted so as to be longitudinally adjustable along the groove (7).

Description

[0001] The present invention relates to a hold-down device for pressing a first component onto a second component to be welded thereto, according to the preamble of claim 1. The invention also relates to a laser welding device comprising a laser, a control device for controlling a laser, and such a hold-down device. Furthermore, the present invention relates to a laser welding method for welding two components using such a laser welding device.

[0002] EP 2 473 312 B1 discloses a laser welding device for joining a first sheet metal part to a second sheet metal part by brazing and welding, comprising a housing supporting a head for emitting a laser beam and a nozzle for applying the welding wire, which are suitable for producing a welding wire along a connecting line between said first and second sheet metal parts. The housing further supports a pressure roller for prestressing the two sheet metal parts to be welded together, said pressure roller being arranged upstream of the laser beam relative to the direction of movement of the laser beam along the connecting line. The housing further has a second pressure roller whose position is offset relative to the first pressure roller and relative to the direction of movement of the laser beam, said second pressure roller being arranged between the first pressure roller and the laser beam.

[0003] JP 2001-129676 A discloses a laser welding device for laser welding two metal plates. Three pressure rollers rolling together with a laser welding head are arranged near an overlapping weld line. The second and third pressure rollers are arranged coaxially with one another, with the second pressure roller having a smaller diameter than the third pressure roller. The first pressure roller, in turn, is arranged on the opposite side of the two components. Due to the smaller diameter of the second pressure roller compared to the third pressure roller, a predefined gap can be maintained between the two components to be welded together. This is intended to improve the weld quality.

[0004] CN 201154422 Y discloses a laser welding device comprising a gantry frame, a movable table, and a front press beam arranged vertically and movably above the gantry frame. The front and rear press beams have several pressure rollers, which can be used to press the two components to be joined together.

[0005] EP 1 982 789 A2 discloses a laser welding method for welding two overlapping steel sheets, comprising the following steps: inserting inserts between the joining surfaces of the first steel sheet and the second steel sheet, and welding the two steel sheets using a laser beam. The inserts can create a defined gas outlet channel, which is intended to improve welding quality.

[0006] CN 116 511 714 A discloses a flexible jump control structure for laser welding thin plates, wherein the flexible jump control structure comprises a workbench, a correction mechanism, a jump elimination mechanism, and a centerline butt joint mechanism, and support legs are fixed to the bottom of the workbench; the correction mechanism is mounted on the workbench; the step difference elimination mechanism is installed on the workbench.

[0007] CN 104 816 092 A relates to a device and a method for laser spot welding heat exchange plates. The device for laser spot welding heat exchange plates comprises a workbench, a laser welding head, and a gas protection device, and further comprises a cooling base plate, two press beams, and two press wheels, the press beams being arranged in parallel. The two press wheels are arranged on either side of the laser welding head and are pressed tightly onto the two heat exchange plates. The pressing positions of the two press wheels are arranged between the two press beams, and the two press wheels and the laser welding head move synchronously during welding.

[0008] In addition to rollers, so-called rigid hold-down clamps are often used in laser welding, which press the components to be joined together. However, due to the inclination of the components to be welded and / or the use of such a hold-down clamp, gaps can form between the overlapping components, which has a detrimental effect on the laser welded joint.

[0009] The hold-down devices with pressure rollers known from the prior art can reduce the risk of a gap occurring between at least two components to be welded together, but the hold-down devices known from the prior art and used for this purpose are structurally very complex and therefore expensive.

[0010] The present invention therefore addresses the problem of providing an improved or at least an alternative embodiment for a hold-down device of the generic type, by means of which, on the one hand, a high welding quality can be achieved while, on the other hand, the hold-down device is structurally simple and cost-effective.

[0011] This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0012] The present invention is based on the general idea of providing two pressure balls or pressure rollers in a hold-down device, which roll in associated grooves at the same height as a laser beam. These pressure balls or pressure rollers ensure, on the one hand, a reliable and, in particular, tilt-free pressing of the first component onto a second component to be welded thereto and, on the other hand, enable an extremely simple and therefore cost-effective design of the hold-down device. The hold-down device according to the invention for pressing a first component onto a second component to be welded thereto has a base body with two grooves parallel along two sides, with a pressure ball or pressure roller mounted in each of these grooves so as to be longitudinally adjustable along the groove.The pressure roller is mounted so smoothly along and within the groove that, during a laser welding process, simply applying varying loads to the base body allows the pressure roller or pressure ball to slide along the corresponding groove. During the welding process, the pressure roller or pressure ball is preferably always at the same height as a laser beam welding at least two components together. This ensures reliable and gap-free pressing of the two components to be welded together, without, for example, having to fear that the hold-down device or the two components will become jammed.Due to the fact that the hold-down device according to the invention only has the base body with the two parallel grooves and two pressure balls or two pressure rollers, it essentially consists of only three components, which enables a significantly simpler structural design compared to hold-down devices known from the prior art and having such pressure rollers.

[0013] In an advantageous development of the hold-down device according to the invention, the base body is designed as a frame with a central opening, with the two grooves running along two parallel frame sides. The frame can thus be designed, for example, as a rectangular frame with two longitudinal legs and two transverse legs, with the grooves being arranged, for example, in the two longitudinal legs, so that the two pressure balls or the two pressure rollers are also adjustable along these two longitudinal sides. The central opening serves to guide a laser beam from a laser device between the two pressure balls or between the two pressure rollers onto the components to be welded together.

[0014] The present invention is further based on the general idea of providing a laser welding device with a laser and a hold-down device as described in the previous paragraphs, as well as with a device for pressing down the hold-down device and with a control device for controlling the laser and the device. As a result, the advantages described with regard to the hold-down device can also be transferred to the laser welding device according to the invention. Specifically, these advantages lie, on the one hand, in a structurally simple and thus cost-effective hold-down device and, on the other hand, in high welding quality, since the hold-down device according to the invention enables particularly effective and gap-free pressing together of the two components to be welded together.

[0015] In a particularly preferred embodiment of the laser welding device according to the invention, the laser beam is arranged centrally relative to the two pressure balls or pressure rollers. The laser, and thus the laser beam of the laser, is arranged pivotably relative to the frame so that the laser beam can always be kept centrally between the two pressure balls or the two pressure rollers during the welding process. By aligning the laser beam in this way with respect to the pressure balls or the pressure rollers, or vice versa, the two components to be welded can be welded at exactly the point at which the two pressure balls or the two pressure rollers are connected to the first component in a force-introducing manner, so that the two components are always welded at exactly the point at which the greatest hold-down force is introduced.

[0016] The control device can be used to control the alignment of the laser beam as well as the adjustment of the two pressure balls or pressure rollers.

[0017] The present invention is further based on the general idea of specifying a laser welding method for welding two components by means of a laser welding device described in the previous paragraphs. In the laser welding method according to the invention, a laser beam of the laser is moved at a feed speed in a feed direction relative to the hold-down device and relative to the components to be welded together, with a force F1 being exerted on the hold-down device at the front and a force F2 at the rear. The control device controls the forces F1 and F2 as a function of the feed speed of the laser, so that the two pressure balls or the two pressure rollers are always at the level of the laser beam. "Front" and "rear" on the hold-down device means front or rear in the feed direction. An adjusting movement of the pressure balls or the pressure rollers is determined by a ratio of the two forces F1 and F2.-rollers in the respective associated groove are controlled analogously to the laser beam, so that the two pressure rollers or the two pressure balls can always be kept at the height of the laser beam by different forces F1 and F2 and there ensure effective compression, in particular gap-free compression, of the components to be welded together.

[0018] In the method according to the invention, the force F2 is greater than the force F1 at the start of a welding process and less than the force F1 at the end of the welding process. This makes it possible to move the pressure balls or the pressure rollers from a rear end of the groove forwards by means of a force F2 that is initially greater at the start of the welding process, whereby the force F2, which is initially greater than the force F1 at the start of the welding process, can accelerate the pressure balls. If the two forces F1 and F2 are equal, the pressure balls or the pressure rollers do not move. To set the pressure balls or the pressure rollers in motion, F1 ≠ F2 must therefore always apply. The greater the difference between the force F2 and the force F1, the greater the acceleration or deceleration of the pressure balls or the pressure rollers. By applying different loads to the base body of the hold-down device using the force F1 orF2 thus allows for precise positioning of the pressure balls or pressure rollers, so that they are positioned throughout the entire welding process, preferably at exactly the same height as the laser beam positioned between them. This ensures that the first component is always pressed down optimally onto the second component in the area of the laser beam. By arranging the two pressure rollers or pressure balls adjacent to the laser beam, a comparatively high surface pressure can be achieved directly at the welding position, reliably closing any gap and, if necessary, even slightly deforming or bending an upper component.

[0019] In a further advantageous embodiment of the method according to the invention, the hold-down device is not adjusted in the feed direction relative to the components to be welded during the welding process. Thus, there is no relative adjustment of the hold-down device relative to the components to be welded in the feed direction. To move the pressure balls or pressure rollers in the associated grooves, the base body of the hold-down device is simply pivoted relative to the first component.

[0020] In a particularly preferred embodiment of the method according to the invention, the control device controls the forces F1 and F2 acting on the base body of the hold-down device in such a way that the two pressure balls or the two pressure rollers are always at the same height as a laser beam welding the two components. This allows the advantage described in the previous paragraph—namely, high surface pressure—to be achieved directly in the laser welding area, allowing any gaps between the components to be welded to be reliably closed.

[0021] In a particularly preferred embodiment of the method according to the invention, the two pressure balls or the two pressure rollers move in the feed direction from a rear end of the respective groove to a front end of the respective groove during the welding process. This ensures that the pressure balls or the pressure rollers move with the laser beam and are always positioned directly adjacent to it. Movement of the base body of the hold-down device in the feed direction is not required.

[0022] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention as defined by the claims. Components mentioned above and to be mentioned below of a higher-level unit, such as a device, an apparatus, or an arrangement, which are designated separately, may form separate parts or components of this unit or be integral areas or sections of this unit, even if this is shown differently in the drawings.

[0024] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0025] They show, schematically, Fig. 1 a plan view of a hold-down device according to the invention for pressing down a first component onto a second component to be welded thereto, Fig. 2 a laser welding device according to the invention with a laser and a corresponding Fig. 1 shown hold-down device in side view, Fig. 3 different process steps of a laser welding process according to the invention for welding two components by means of a laser welding device according to the invention, Fig. 4 an exemplary force-displacement diagram to illustrate a load on a base body of the blank holder during the welding process.

[0026] According to the Fig. 1 comprises a hold-down device 1 according to the invention for pressing down a first component 2 (compare Fig. 2) onto a second component 3 to be welded thereto, a base body 4 with two parallel grooves 7 running along two sides 5, 6. In each of these grooves 7, a pressure ball 8 or a pressure roller (not shown in detail) is mounted so as to be longitudinally adjustable along the groove 7.

[0027] Looking at the Fig. 1, it can be seen that the base body 4 is designed as a frame with a central opening 9, with the two grooves 7 running along two parallel frame sides, here sides 5 and 6. A laser beam 10 of a laser welding device 11 can be directed through the central opening 9 to produce a weld seam 12.

[0028] The laser welding device 11 according to the invention has a laser and a laser optics 13 and a hold-down device 1 according to the previous paragraphs as well as a device 16 for pressing down the hold-down device 1 and a control device 14 for controlling the laser and the laser optics 13 as well as the device 16. The control device 14 acts on the device 16 in such a way that it controls a load on the base body 4 of the hold-down device 1 by means of a force F1 and a force F2 and thus a movement of the pressure balls 8 in the same way as the laser beam 10 moves.

[0029] Looking at the Fig. 1 closer, it can be seen that the laser beam 10 is arranged centrally to the two pressure balls 8 or the two pressure rollers.

[0030] In the following, the method according to the invention for welding two components 2, 3 by means of a laser welding device 11, as shown in FIG. Fig. 2. First, the laser beam 10 is moved at a predefined feed rate in a feed direction 15 (compare the Fig. 1 to 3) relative to the blank holder 1 and to the components 2, 3 to be welded together. A force F1 is exerted on the blank holder 1 at the front, ie in the feed direction 15, and a force F2 is exerted at the rear, for example by means of the device 16, as is shown in the Fig. 2 and Fig. 3. The control device 14 now controls these forces F1 and F2 as a function of the feed rate of the laser beam 10 via the device 16.

[0031] In order to ensure that the pressure rollers 8 are always at the same height as the laser beam 10 producing the weld seam 12, the base body 4 of the hold-down device 1 is at the beginning of a welding process (compare Fig. 3a) is loaded at the rear with a force F2 which is greater than the front force F1. This causes the pressure rollers 8 to be pushed forward, as shown in the Fig. 3b. In the further welding process, the force F2 is reduced and the force F1 is increased, as shown in the diagram in Fig. 4. By increasing the front force F1 and reducing the rear force F2, the adjustment movement of the pressure balls 8 is slowed down. In this case, it must always be ensured that the control device 14 controls the forces F1 and F2 in such a way that the two pressure balls 8 or alternatively the two pressure rollers are always at the same height as a laser beam 10 of the laser 13 welding the two components 2, 3, since this can ensure that the two components 2, 3 to be welded together are reliably pressed against one another in the plane in which they are to be welded and that any gaps that may be present there are closed.

[0032] Looking at the Fig. 3c, this represents an end of the welding process in which the force F2 is smaller than the force F1, whereby here too the pressure balls 8 are again at the same height as the laser beam 10 at its impact surface on the first component 2. A “same height” should be understood in this case in the feed direction 15.

[0033] The two pressure balls 8, or the two pressure rollers, thus move during the welding process in the associated groove 7 in the feed direction 15 from a rear end of the respective groove 7 to a front end of the respective groove 7. The hold-down device 1 is not adjusted in the feed direction 15 with respect to the components 2, 3 to be welded together during the entire welding process.

[0034] Looking again at the Fig. 3a to 3c, it can be seen that an inclination of the base body 4 of the blank holder 1 at the beginning of the welding process according to the Fig. 3a is greater and until the welding process is completed, as described in Fig. 3c, becomes increasingly smaller, allowing the adjustment movement of the pressure balls 8 to be controlled extremely precisely. In general, the sum of the forces F1 and F2 remains the same throughout the entire process, so that only the percentage shares of the total force for the forces F1 and F2 change.

[0035] All in all, with the hold-down device 1 according to the invention and the laser welding device 11 according to the invention, a hold-down device 1 can be created which is structurally significantly simpler and therefore more cost-effective than hold-down devices previously known from the prior art, which also has a positive effect on the manufacturing costs of the laser welding device 11. The hold-down device 1 used in the laser welding method according to the invention ensures that, during the entire welding process, the first component 2 is pressed down onto the second component 3 in the area of the point of impact of the laser beam 10 on the first component 2 with maximum force due to the simultaneous adjustment of the two pressure balls 8 and the laser beam 10, whereby any gaps that may occur there can be reliably closed and a high-quality weld seam 12 can therefore be produced.

Claims

[1] Hold-down device (1) for pressing down a first component (2) onto a second component (3) to be welded thereto, wherein the hold-down device (1) has a base body (4) with two grooves (7) parallel along two sides (5, 6), and wherein in each groove (7) a pressure ball (8) or a pressure roller is mounted so as to be longitudinally adjustable along the groove (7), characterized by , that the pressure ball or the pressure roller is mounted so smoothly along the groove and within it that during a laser welding process a simple different loading of the base body allows the pressure roller or the pressure ball to slide along in the corresponding groove. [2] Hold-down device (1) according to claim 1, characterized by that the base body (4) is designed as a frame with a central opening (9), wherein the two grooves (7) run along two parallel sides (5, 6) of the frame. [3] Laser welding device (11) with a laser and laser optics (13) and a hold-down device (1) according to claim 1 or 2 and with a device (16) for pressing down the hold-down device (1) and a control device (14) for controlling the laser (13) and the device (16). [4] Laser welding device (11) according to claim 3, characterized by that the laser beam (10) is arranged centrally to the two pressure balls (8) or pressure rollers. [5] Laser welding method for welding two components (2, 3) by means of a laser welding device (11) according to one of claims 3 or 4, in which a laser beam (10) of the laser and the laser optics (13) is adjusted at a feed rate in a feed direction (15) relative to the hold-down device (1) and to the components (2, 3) to be welded together, wherein by means of the device (16) a force F1 is exerted on the hold-down device (1) at the front and a force F2 at the rear, characterized bythat the control device (14) controls the forces F1 and F2 as a function of the feed rate of the laser beam (10), and at the start of a welding process the force F2 is greater than the force F1 and at the end of the welding process the force F2 is smaller than the force F1. [6] Method according to claim 5, characterized by that the control device (14) controls the forces F1 and F2 via the device (16) in such a way that the two pressure balls (8) or pressure rollers are always at the same height as the laser beam (10) of the laser and the laser optics (13) welding the two components (2, 3). [7] Method according to one of claims 5 or 6, characterized by that the hold-down device (1) is not adjusted in the feed direction (15) during the welding process with respect to the components (2, 3) to be welded together. [8] Method according to one of claims 5 to 7, characterized bythat the two pressure balls (8) or pressure rollers move in the feed direction (15) from a rear end of the respective groove (7) to a front end of the respective groove (7) during the welding process in the associated groove (7).

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