Cooling device for ultrasonic welding system, ultrasonic welding device and method for operating ultrasonic welding device

Abstract

The invention relates to a cooling device for an ultrasonic welding device, comprising a heat sink, the heat sink having at least one coupling surface for coupling the heat sink to the ultrasonic welding device, an inlet and an outlet, and at least one fluid channel extending between the inlet and the outlet.

Description

Technical Field

[0001] The present invention relates to a cooling device for an ultrasonic welding device, in particular to a welding head for an ultrasonic welding device. In addition, the present invention also relates to an ultrasonic welding device and a method for operating an ultrasonic welding device. Background Art

[0002] Ultrasonic welding is a material-fitting joining method in which high vibration energy is input into the contact surface between two workpieces through ultrasonic vibrations, causing plastic flow to occur on the surface of the workpieces at the contact surface between the workpieces and forming a material-fitting connection between the workpieces.

[0003] For vehicle manufacturing applications, ultrasonic welding is not only used for welding plastic parts, but also for welding metal workpieces. Due to the increasing application of aluminum alloys in metal wires (especially high-energy wires, battery wires, single cell connectors, battery module connectors, etc.), ultrasonic welding has become more and more practical because this welding method is particularly suitable for welding aluminum alloys.

[0004] In vehicle manufacturing applications, high-energy wires, battery wires, single cell connectors, battery module connectors, etc. are particularly needed, which can be designed as flat wires (busbars) or round wires, for example. In order to realize power shunting / branching on flat wires, connecting parts (such as studs, terminal lugs, cable lugs, etc.) are joined together with the wire material, especially by friction welding, especially ultrasonic welding.

[0005] In series production, which has become the norm in vehicle manufacturing applications, high cycle rates are indispensable. To achieve high cycle rates, the rest time between two welding processes must be as short as possible. Ultrasonic welding systems are capable of performing a large number of welds within a period of time at high cycle rates. In this way, the ultrasonic welding head for inputting ultrasonic vibrations is almost always in operation. This means that between two welding processes, while the system is loading the workpieces and while the system is removing the workpieces to be welded together, the welding head is in the rest position. During welding, the welding head is in the welding position. To achieve high cycle rates, the quotient between the time the welding head is in the rest position and the time the welding head is in the welding position should be as small as possible. A short rest time compared to the welding time can result in the welding head not being able to cool down sufficiently during the rest time.

[0006] As mentioned at the beginning of this article, ultrasonic vibrations are input into the contact surface between two workpieces by means of an ultrasonic welding head. During this process, intense friction occurs on the contact surface between the workpieces, causing the oxide layer to break and a material fit connection to be formed by the mutual meshing of the workpieces. The welding head heats up intensely during the welding process. It is important to avoid the welding head heating up above the limit temperature. For this reason, sufficiently long rest times were required in the past in order to sufficiently cool the welding head by convection. Such rest times would limit the cycle rate and thus the maximum throughput that could be achieved with an ultrasonic welding device.

[0007] In addition, due to the increased temperature, the welding head will also wear more. In addition, due to the heating of the welding head, it may also stick to the workpiece. Finally, a welding head that is too hot may cause the workpiece to deform. If the welding head is pressed against the workpiece, the temperature of the welding head alone may cause the workpiece to deform. Such deformation is undesirable. More precisely, it is desirable to achieve welding only by the ultrasonic vibrations input at the contact surface between the workpieces, but the welding head itself should not cause damage to the workpiece. Summary of the invention

[0008] For the reasons stated, the horn temperature is a limiting factor for the cycle rate of an ultrasonic welding device.It is an object of the present invention to cool the horn of an ultrasonic welding device as efficiently as possible.

[0009] The object of the invention is achieved by a cooling device according to claim 1 , an ultrasonic welding device according to claim 14 and a method according to claim 16 .

[0010] The cooling device comprises a heat sink. The heat sink has a coupling surface. The coupling surface can be designed in the form of a flange. The coupling surface is used to couple the heat sink to the ultrasonic welding device. For example, the heat sink flange can be connected to the ultrasonic welding device with the help of the coupling surface. The coupling surface is used to fix the cooling device to the ultrasonic welding device. In addition, the cooling device comprises at least one inlet and at least one outlet, between which at least one fluid channel extends, and the fluid channel connects the two to each other. The inlet is used to input a pressurized fluid, in particular compressed air or another pressurized gas. Starting from the ultrasonic welding device, the fluid can be blown into the heat sink through the inlet under pressure.

[0011] The inlet is used to input a pressurized fluid, in particular compressed air or another pressurized gas. The fluid can be blown into the heat sink under pressure through the inlet.

[0012] The outlet is used to discharge the fluid, especially the pressurized gas, blown into the heat sink through the inlet. The inlet and the outlet are fluidically connected to each other so that there is a fluid channel (flow channel) between the inlet and the outlet. The fluid channel extends in the heat sink. The fluid channel connects the inlet and the outlet. The fluid flowing into the inlet flows out from the outlet. The fluid flowing out of the outlet flows through the welding head of the ultrasonic welding device after flowing out of the outlet, and then cools the welding head in addition to the convection cooling of the welding head. By allowing the fluid flowing out at the outlet to flow through the welding head, the cooling of the welding head can be improved. Therefore, preferably during the rest time, but additionally or alternatively, also during the welding time, the fluid is allowed to flow through the welding head, and cooling is thus achieved.

[0013] As mentioned at the beginning of this article, the welding head heats up by inputting ultrasonic vibrations into the workpiece. The welding head is usually the most temperature-critical tool on an ultrasonic welding device. By additionally allowing fluid from the outlet to flow through the welding head, the cooling effect can be improved. The welding head can be operated at an increased cycle rate without causing damage to the welding head or the workpiece. Cooling can be continuous, so that fluid flows through the welding head both during welding and during rest periods.

[0014] The fluid flows towards the outflow axis of the outlet. The outflow axis preferably extends along the surface normal of the outlet cross section. The outflow axis usually passes through the midpoint of the outlet cross section. The outflow axis is preferably directed towards the horn. Preferably, the outflow axis is directed towards the horn tip. The horn tip refers to the section of the horn closest to the workpiece to be machined. Advantageously, this is to achieve the most efficient cooling possible at the horn part where heat is generated. In the installed state, i.e. in the assembled state, the horn is mounted on the ultrasonic welding device.

[0015] Preferably, the fluid may be air. However, the fluid may also be an inert gas. In particular, the fluid may be nitrogen.

[0016] In a preferred embodiment, the heat sink has a basic hose-like shape and at least two openings, one of which is an inlet and the other is an outlet, between which the fluid channel extends. Optionally, multiple inlets and / or outlets can also be provided. Preferably, the coupling surface is located on the wall of the hose-like heat sink, and the heat sink is fixed to the ultrasonic welding device via the coupling surface to prevent the heat sink from slipping during the cooling process. The advantage of a hose-like heat sink is that it can be realized particularly easily.

[0017] In another preferred embodiment, the heat sink has at least one leg away from the coupling surface. At least one outlet is arranged in the at least one leg. Preferably, the heat sink has one or two legs, wherein an outlet is arranged in each leg. Although the heat sink with legs is much more complex than a simple hose-shaped heat sink, it has advantages in guiding the fluid channel and the adjustment capability of the heat sink to the existing ultrasonic device and the welding head. Through the legs of the heat sink, the fluid flow can be directed to the welding head in a targeted manner. In addition, compared with the hose-shaped heat sink, the heat sink with at least one leg can be approached and guided along the welding head.

[0018] Preferably, the heat sink has at least two legs that are away from the coupling surface and keep a certain distance from each other and each have an outlet. In other words, the heat sink extends from the coupling surface to at least two legs that keep a certain distance from each other. Preferably, the outflow axis of the fluid from the outlet is directed toward the welding head arranged between the legs. The outflow axes of the two outlets intersect in particular with the space occupied by the welding head. Preferably, the outflow axes of at least two of the outlets intersect in the space occupied by the welding head. In the installed state, that is, in the assembled state, the welding head is installed on the ultrasonic welding device. In this state, the welding head occupies the space between the legs of the heat sink. The outflow axes of at least two, preferably all outlets intersect at least with this space of the welding head. In this way, it is ensured that the fluid flowing out of the outlet flows through the welding head.

[0019] The inlet can be designed on the surface of the cooling device facing the ultrasonic device or facing away from the ultrasonic device, depending on how the fluid flow is to be fed in. Preferably, at least one inlet is arranged in the coupling surface so that the fluid flow is fed in directly via the ultrasonic device. Preferably, the coupling surface with the inlet is adapted for the ultrasonic welding device so that a fluid-tight connection, in particular a gas-tight connection, is ensured at the inlet with respect to the environment. The coupling surface seals the inlet in a fluid-tight manner, in particular a gas-tight manner, with respect to the environment in the circumferential direction.

[0020] According to one embodiment, it is proposed to process the heat sink by an additive manufacturing method. The additive manufacturing method is also known as a 3D printing method, which has the advantage that a fluid channel between an inlet and an outlet in the heat sink can be formed by a simple processing method. In addition, the heat sink can be processed with a filling degree of less than 100%.

[0021] For the processing of the heat sink, various additive manufacturing methods are suitable, such as binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination or stereolithography. Such manufacturing methods make it particularly easy to process heat sinks with different form factors. In particular, not only the coupling surface can be adapted to the ultrasonic welding device, but also the possible feet can be adapted to the shape of the welding head used. Additive manufacturing methods make it particularly easy to adapt the heat sink to existing ultrasonic welding devices.

[0022] It is particularly advantageous to use synthetic polymers for the additive manufacturing method, preferably polylactic acid (PLA), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS) and / or polyamide 6.6. In this context, polylactic acid (PLA) has been found to be particularly suitable for processing heat sinks.

[0023] The heat sink is preferably designed as a hollow body, wherein the fluid channel is arranged in the outer wall surface of the heat sink. Here, the filling of the heat sink is recommended to have a filling degree of less than 90%, preferably less than 50%, and particularly preferably less than 20%. In order to avoid the formation of condensate on the heat sink, the heat sink should have a filling degree as low as possible.

[0024] The fluid flow through the fluid channel generally has the effect of cooling the fluid channel. If the heat conduction between the fluid channel and the outer wall is intense, condensate may form on the outer wall depending on the ambient temperature and air humidity, wherein the condensate may drip from the outer wall onto the workpiece. It has been found that a filling degree of less than 90%, in particular less than 50%, is sufficient to avoid the formation of condensate. And good results can be achieved in particular with a filling degree of less than 20%. In addition to the fluid channel and the outer wall, the heat sink is in particular hollow. Such a hollow structure of the heat sink can be processed particularly conveniently using additive manufacturing methods. It is also recommended that the heat sink has a hollow structure. That is, a web is formed between the outer wall and the fluid channel, which contributes to the mechanical stability of the heat sink. Honeycomb structures are particularly helpful to achieve mechanical stability of the heat sink.

[0025] According to one embodiment, it is proposed that the legs extend in a plane parallel to the coupling surface. The coupling surface extends along a plane. The two legs preferably extend parallel to the coupling surface in their longitudinal direction.

[0026] According to another embodiment, the extension direction of the support leg may be parallel to the surface normal of the coupling surface. Then the support leg extends parallel to the surface normal.

[0027] The cooling device according to the invention is used to cool the welding head before, during and / or after welding. During welding, the welding head is moved onto the workpiece and bears against the workpiece. During this process, the welding head preferably performs a linear lifting movement. The workpiece is located below the welding head and the welding head is moved onto the workpiece. The heat sink preferably moves stably together with the welding head.

[0028] In order to ensure the flow of fluid through the welding head, outlets are advantageously arranged on the legs on both sides of the welding head. In order to be able to arrange the welding head between the legs, it is recommended that the legs extend a U-shaped support. The outlet can be arranged on the inside of the legs. The legs extend from the support and the welding head can be arranged in the support. Since the cooling device is connected to the ultrasonic welding device by means of the coupling surface, the cooling device can follow the lifting and lowering movement of the welding head. In other words, the cooling device moves stably along the stroke together with the welding head. In this way, it can be ensured that the fluid flows through the welding head at any time.

[0029] According to one embodiment, it is proposed that the legs are arranged relative to one another in such a way that a sonotrode of an ultrasonic welding device can be supported in a support between the legs.

[0030] According to one embodiment, it is proposed that the outlet on one leg faces the other outlet of the other leg. The outlets are thus facing each other. The welding head is arranged between the outlets.

[0031] According to one embodiment, it is suggested to arrange the outlet at the end of the heat sink away from the coupling surface. In this way, the outlet is arranged on the heat sink away from the coupling surface. In this way, as much space as possible can be ensured to arrange the welding head between the legs of the heat sink.

[0032] According to one embodiment, it is suggested that the fluid channel in the heat sink has branches, so that the fluid channel is divided into a channel leading to each outlet at the branch starting from the inlet. In this way, the fluid can be blown into the heat sink through a single inlet, and the fluid channel ensures that the fluid is distributed to each outlet.

[0033] Another aspect relates to an ultrasonic welding device according to claim 14. The welding head is arranged between the legs of the heat sink. The heat sink follows the lifting and lowering movement of the welding head. The lifting and lowering movement of the welding head is in particular consistent with the lifting and lowering movement of the heat sink. In this case, the welding head and the heat sink are particularly preferably fixed to each other mechanically.

[0034] According to one aspect, a method for operating the aforementioned ultrasonic welding device is proposed. During ultrasonic welding, the welding surface of the welding head is pressed against the workpiece, and ultrasonic vibrations are introduced into the welding head. This ultrasonic vibration is transmitted to the workpiece, and welding energy is input through ultrasonic welding vibrations on the contact surface between the two workpieces, so that the workpieces undergo plastic flow on their contact surfaces and form a material-fitting connection with each other. It is recommended to blow a cooling fluid (especially gas) into the inlet of the heat sink before, during and / or after the ultrasonic vibrations are introduced into the welding head. Preferably, the cooling fluid is blown into the inlet continuously. However, it is also possible to blow the cooling fluid into the inlet only during the welding process. The cooling fluid is blown into the inlet under pressure and flows out from the outlet, thereby flowing through the welding head. The welding head is cooled by the cooling fluid flowing through. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be explained in more detail below with reference to the accompanying drawings which illustrate embodiments.

[0036] Figure 1 An ultrasonic welding device according to an embodiment is shown;

[0037] Figure 2a , Figure 2b A view showing a heat sink according to an embodiment;

[0038] Figure 3a , Figure 3b A view of a heat sink according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0039] Figure 1 A view of an ultrasonic welding device 2 is schematically shown. The ultrasonic welding device 2 comprises a so-called horn 4, by means of which ultrasonic vibrations can be introduced into a horn 6. An anvil 8 is arranged on the ultrasonic welding device 2 opposite the horn 6. Between the horn 6 and the anvil 8, workpieces 10a, 10b are arranged for welding. The workpieces 10a, 10b are directly in contact with each other on a contact surface 10c. During welding, the horn 6 is moved along a stroke 12 onto the workpiece 10a and pressed against the workpiece 10a. The workpieces 10a, 10b are pressed against the contact surface 10c by the horn 6 and the anvil 8. Subsequently, ultrasonic vibrations are introduced into the horn 6 by means of the horn 4, and the workpieces 10a, b undergo plastic flow on the contact surface 10c and form a material-fit connection with each other.

[0040] According to the present invention, it is proposed to arrange the heat sink 14 on the ultrasonic welding device 2 .

[0041] Figure 2a FIG. 1 shows a view of such a heat sink 14. The heat sink 14 comprises a coupling surface 16 and two legs 18a, 18b. Figure 2aAs shown, the legs 18a, 18b extend out of the support portion 20. Figure 2b ) An opening 22 is designed so that the heat sink 14 can be screwed to the ultrasonic welding device 2 or fixed in another way in a form-fitting manner.

[0042] Figure 2a It can also be seen in FIG. 1 that an outlet 24 a is arranged on the side of the foot 18 a facing the support part 20 .

[0043] Figure 2b Another view shows Figure 2a The heat sink 14 shown. It can be seen here that an outlet 24b is arranged on the foot 18b, also on the side facing the support part 20. The outlets 24a, b face each other. An inlet 26 is designed on the coupling surface 16. A groove 28 can be arranged around the inlet 26. An O-ring can be arranged in the groove 28 to seal the opening 26 in a fluid-tight manner in the circumferential direction.

[0044] Figure 3a Shows Figure 2a , b are top views of the heat sink 14. In the top view, it can be seen that the fluid channel 30 extends from the inlet 26 into the heat sink 14. The fluid channel 30 is divided into two branches in the heat sink 14, which lead to the outlets 24a and 24b respectively. In this way, the inlet 26 is fluidically connected to the outlets 24a and 24b through the fluid channel 30. During the welding process and / or

[0045] Or before and after the welding process, fluid (air / gas) is blown into the fluid channel 30 through the inlet 26 and flows out from the outlets 24a, 24b to cool the welding head 6.

[0046] exist Figure 3b In the cross-sectional view II Ib-IIIb visible in FIG, the fluid channel 30 in the upper part of the heat sink 14 can be seen. The outlet 24a can be seen on the leg 18a. The heat sink 14 is preferably a component processed by means of additive manufacturing, and the interior of the component is largely hollow. The outer wall of the heat sink 14 and the wall of the flow channel 30 can be formed from the material of the additive manufacturing method. Between the walls, the heat sink is hollow to the greatest extent. The fluid channel 30 can be connected to the outer wall of the heat sink 14 by a web (not shown) so as to be mechanically fixed in the heat sink 14. A hollow structure, in particular a honeycomb structure, can be designed inside the heat sink 14 in order to give the heat sink mechanical stability.

[0047] The heat sink 14 can be used to cool the welding head 6, thereby increasing the cycle rate of the ultrasonic welding device 2. In addition, damage to the workpiece 10 due to overheating of the welding head 6 can be avoided.

[0048] Description of Reference Numerals

[0049] 2 Ultrasonic welding device

[0050] 4 Luffing rod

[0051] 6 Welding head

[0052] 8 Anvil

[0053] 10 Workpiece

[0054] 12 Itinerary

[0055] 14 Heat sink

[0056] 16 Coupling surface

[0057] 18a, b Support feet

[0058] 20 Supporting part

[0059] 22 Opening

[0060] 24a, b Exit

[0061] 26 Entrance

[0062] 28 grooves

[0063] 30 Fluid Channels

Claims

1. Cooling device for ultrasonic welding device, having - a heat sink, wherein the heat sink has at least - a coupling surface for coupling the heat sink to the ultrasonic welding device, - entrance, and -exit, It is characterized in that - At least one fluid channel extends between said inlet and said outlet.

2. The cooling device according to claim 1, characterized in that: - the heat sink has at least one leg away from the coupling surface, It is characterized in that - At least one of said outlets is arranged in at least one of said feet.

3. The cooling device according to claim 1 or 2, characterized in that: At least one of the inlets is arranged in the coupling surface.

4. A cooling device according to any one of the preceding claims, It is characterized in that The heat sink is processed by an additive manufacturing method, in particular by binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination or stereolithography.

5. A cooling device according to any one of the preceding claims, It is characterized in that The heat sink is at least partially processed from a synthetic polymer, preferably from polylactic acid (PLA), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS) and / or polyamide 6.6, in particular from polylactic acid (PLA).

6. A cooling device according to any one of the preceding claims, It is characterized in that The heat sink is designed as a hollow body and preferably has a filling degree of less than 90%, particularly preferably less than 50%, in particular less than 20%.

7. The cooling device according to any one of claims 2 to 6, It is characterized in that The cooling device has at least two of the legs, each having at least one of the outlets.

8. The cooling device according to claim 7, It is characterized in that - the legs extend in a plane parallel to the coupling surface, or The legs extend in a plane parallel to the surface normal of the coupling surface.

9. The cooling device according to claim 7 or 8, It is characterized in that - The foot extends out of a U-shaped support.

10. The cooling device according to any one of claims 7 to 9, It is characterized in that The feet are arranged relative to one another in such a way that a welding head of the ultrasonic welding device can be supported in the support between the feet.

11. The cooling device according to any one of claims 7 to 10, It is characterized in that - said outlet of one of said legs is directed towards the other of said legs.

12. The cooling device according to any one of claims 7 to 11, It is characterized in that The outlet is arranged at an end of the heat sink remote from the coupling surface.

13. The cooling device according to any one of claims 7 to 12, It is characterized in that The fluid channel in the heat sink has branches, so that the fluid channel is divided from the inlet into at least one fluid channel leading to each of the outlets at the branches.

14. Ultrasonic welding device having a cooling device, a horn and an anvil according to any one of the preceding claims, wherein: At least one outlet of the heat sink faces the welding head.

15. The ultrasonic welding device according to claim 14, comprising a cooling device according to any one of claims 7 to 13, wherein: The welding head is arranged between the legs of the heat sink.

16. Method for operating an ultrasonic welding device according to claim 14 or 15, wherein: - placing the welding face of the horn against the workpiece and introducing ultrasonic vibrations into the horn, and - before, during and / or after the introduction of ultrasonic vibrations into the welding head, a cooling fluid, in particular a gas, is blown into the inlet of the heat sink.

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