DE102021119907A1 - Friction stir welding device, method for producing an assembly with a friction stir welding device and an assembly - Google Patents

Abstract

The invention relates to a friction stir welding device (1) for connecting a plurality of components (2, 3) arranged at least partially overlapping one another by generating frictional heat and by stirring a material of at least one component (2, 3). A method for producing an assembly (19) is also proposed, the assembly (19) comprising a plurality of components (2, 3) arranged at least partially overlapping one another in a connection region (20), and the components (2, 3) are connected to one another in the connection area (20) by a friction stir welding process. Finally, an assembly (19) for a battery cell is also specified, at least comprising a multiplicity of cell foils (21) stacked on top of one another for storing electrical energy and at least one contact plate (22); wherein the cell foils (21) form a foil stack (23) in a connection region (20) and the foil stack (23) is connected to the contact plate (22) by at least one friction stir weld connection (10).

Description

The invention relates to a friction stir welding device, a method for producing an assembly with a friction stir welding device and an assembly that was produced by the friction stir welding device and/or the method. The assembly described here includes in particular the electrode foils and the arresters of a battery cell.

The module is in particular a part of a battery cell, z. B. a Lilonen battery cell. The assembly comprises in particular a plurality of components arranged at least partially overlapping one another, preferably a plurality of cell foils stacked on top of one another for storing electrical energy and at least one contact plate. The cell foils form a foil stack in a connection section and the foil stack is connected to the contact plate by at least one welded joint for electrical contacting of the cell foils via the contact plate. The invention is used in particular in the production of lithium-ion batteries for e.g. electrified vehicles.

A battery cell is an electricity storage device that B. is used in a motor vehicle for storing electrical energy. Electrode foils (also referred to below as cell foils), ie anodes and cathodes, are arranged stacked on top of one another in a battery cell, with different electrode foils being arranged separated from one another by separator foils or a separator material. The electrode foils are arranged in an electrolyte within a housing.

The electrode foils arranged inside the housing are connected to an electrical circuit outside the housing via so-called conductors. The conductors extend outwards through the gas-tight housing. Inside the housing, the conductors are electrically conductively connected to the large number of cell foils of the same type, ie anodes or cathodes. In this case, a conductor (also referred to below as a contact plate) is connected to a large number of cell foils. The cell foils form a foil stack in a connection section and the foil stack is connected to the contact plate via a welded connection. This welded joint is generally realized by laser welding and in this case via spot welded joints.

Various methods are known for producing such weld connections: laser welding, ultrasonic welding, pre-ultrasonic welding and laser welding, crimping, resistance welding, riveting, friction stir welding as spot welding.

In terms of accessibility, heat transfer into the component and the mechanical stress on the joining partners, laser beam welding is the preferred joining method for the production of lithium-ion cells and batteries. However, the reproducible, error-free production of Cu-Cu, Al-Al and Al-Cu connections using laser beam welding is due to the poor coupling of the laser light at a wavelength of approx. 1050 nm [nanometer] (infrared laser) and the high thermal conductivity of the material to be welded Materials are severely restricted. Furthermore, copper (Cu) shows an absorptive jump when the physical state of the material changes from solid to liquid. This erratic behavior causes the Cu melt to suddenly overheat, which in turn leads to the vaporization of the material. As a result, there is an irregular shape of the welded joint or very heavy spattering. Faults occur in the welded joint, which can lead to holes, pores, ejections, spatter, unconnected foils, etc., especially when forming longer weld seams (in contrast to short stitched seams with a weld seam extension of less than 5 millimeters or spot welds). These errors reduce the quality of the battery cells and increase the risk of failures in the operation of the battery cells.

The process stability required for the production of such welded joints under large-scale production conditions (e.g. more than 1,000 components per day) has so far only been possible for short welded joints (i.e. stitched seams or spot welds). However, the errors that already occur limit the use of the battery cells produced to date in the manner mentioned above.

At the same time, however, with increasing performance (e.g. rapid charging capability of the battery cells) of the cell chemistry, especially with battery cells of the same size, there is an increasing demand on the quality and length of the welded joint. In particular, material connections between the foils and the arrester are required, which provide a correspondingly large cross-sectional area for the transmission of the increased amounts of electricity.

In addition to the difficulty of avoiding porosity in the weld joint, especially on the cathode side (aluminium), cell foils can tear off due to thermal stress effects when the material cools down after laser welding. When ultrasonic welding z. B. metal particles. The standard holding test is suitable for friction stir welding as spot welding pel of the friction stir welder into the small area to be welded.

• • durch zweifache Bearbeitung des Materials mit einem Laserstrahl,
• • durch das Schweißen von Einzelfolien anstatt eines Folienstapels,
• • durch das Schmelzen des Materials an den Rändern der Bauteile,
• • durch ein Ultraschallschweißverfahren als Vorprozess für das Material,
• • durch einen Reinigungsprozess, um eine Oxidschicht auf der Aluminiumoberfläche zu vermeiden,
• • Rührreibschweißen ist bisher nicht für derartige Baugruppen vorgesehen, weil z. B. die Dimension des Haltestempels für den Anwendungsfall zu groß ist.

So far, these problems z. B. by the following measures:

• • by processing the material twice with a laser beam,
• • by welding individual foils instead of a stack of foils,
• • by melting the material at the edges of the components,
• • through an ultrasonic welding process as a preliminary process for the material,
• • through a cleaning process to avoid an oxide layer on the aluminum surface,
• • So far, friction stir welding has not been planned for such assemblies, because e.g. B. the dimension of the holding stamp for the application is too large.

In the CN 104741769A becomes e.g. B. described the possibility of using a conventional tool for a friction stir welding process for welding stacked metal foils, which consists of three elements, a holding stamp, a cylindrical first tool and a sleeve-shaped second tool. It is proposed there to use this method for the production of battery cells. However, in order to ensure that the centrifugal forces generated by the tool and the friction only act in the desired area, it is necessary to use a strong holding punch. This requirement also prevents the tools from being smaller. The standard size used is therefore 12 mm [millimeters] in diameter, making it impossible to use the method when the desired area is e.g. B. would be less than 10 mm.

There is therefore a need to provide a method for producing such welded joints that is suitable for large-scale production.

From the EP 1 884 308 B1 a friction stir welding method for connecting two components is known, in which a rotary tool has a rotatable pin (hereinafter first tool) and a rotatable shoulder part surrounding the pin (hereinafter second tool).

A cylindrical burr restricting member (hereinafter holding punch) surrounds the turning tool and prevents burr generation around the friction stir whitening zone.

From the US 10,201,873 B2 a friction stir welding device for connecting two components is known, in which a rotary tool has a rotatable pin (hereinafter first tool) and a rotatable shoulder part surrounding the pin (hereinafter second tool). A cylindrical clamping element (hereafter holding punch) surrounds the turning tool and creates a clamping force around the friction stir weld zone.

From the US 20/0206840 A1 a friction stir welding device for connecting two components is known, in which a rotary tool has a rotatable pin (hereinafter first tool) and a rotatable shoulder part surrounding the pin (hereinafter second tool). A cylindrical clamping element (hereafter holding punch) surrounds the turning tool and creates a clamping force around the friction stir weld zone. The clamping element has an extension which penetrates into the friction stir welding zone.

The object of the present invention is to improve the possibility of using the method of friction stir welding in that the clamping ring of the commonly used tool is modified in such a way that the spinning tool fits into the welding area of the desired process.

Proceeding from this, it is an object of the invention to at least partially solve the problems described in connection with the prior art. In particular, the friction stir welding process is to be qualified for the battery cell application.

These objects are solved by the features of the independent patent claims 1 and 7. Further advantageous refinements of the solution proposed here are specified in the dependent patent claims. It should be pointed out that the features listed individually in the dependent patent claims can be combined with one another in any technologically meaningful manner and define further refinements of the invention. In addition, the features specified in the patent claims are specified and explained in more detail in the description, with further preferred configurations of the invention being presented.

A friction stir welding device is proposed for connecting a plurality of components arranged at least partially overlapping one another by generating frictional heat and by stirring a material of at least one component.

• • ein erstes Schweißwerkzeug mit einem, sich entlang einer axialen Richtung erstreckenden, zylindrischen ersten Werkzeug sowie einem sich entlang der axialen Richtung erstreckenden hohlzylindrischen zweiten Werkzeug, das sich um das erste Werkzeug herum erstreckt; sowie
• • einen Haltestempel mit einer Kontaktfläche, über die der Haltestempel während der Erzeugung der Rührreibschweißverbindung die Bauteile in einer Lage gegenüber den Werkzeugen fixiert.

The friction stir welding device comprises at least

• • a first welding tool having a cylindrical first tool extending along an axial direction and a hollow-cylindrical second tool extending along the axial direction and extending around the first tool; as well as
• • a holding stamp with a contact surface, via which the holding stamp fixes the components in a position relative to the tools while the friction stir welded joint is being produced.

The tools are rotatable about an axis of rotation extending along the axial direction and movable along the axial direction to produce a friction stir welded connection of the components relative to the holding stamp and independently of one another. The contact surface encloses a working area for the first welding tool, in which the first welding tool can be moved relative to the holding stamp in a radial direction running transversely to the axial direction.

In particular, the first welding tool is designed in a known manner. Friction stir spot welding (FSSW or refill friction stir spot welding - RFSSW) is a pressure welding process that works below the melting point of the components to be connected.

In the case of friction stir spot welding, e.g. B. created individual spot welds by a rotating pin-shaped first tool and a rotating hollow cylindrical second tool that surrounds the first tool with high force in the upper of z. B. two components, z. B. sheets are pressed, which are superimposed in the lap joint. The material of the upper component is plasticized by the frictional heat and the high pressure, so that the tip of the first tool and/or the second tool dips into the joining zone between the two components and there the materials of the two components or those present on the surfaces mixed oxides. The components are fixed in their position to each other and to the welding tool by the holding stamp. The tools are moved in the axial direction so that the material displaced by the immersion of a tool into the components can escape within the working area delimited by the holding stamp.

Both the tools and the holding stamp can be profiled on their component-contacting end face in order to convey the plasticized material in a specific direction and to efficiently break up and stir up the oxide skins on the surfaces that lie on top of one another.

When using one-piece tools, a hole remains in the components after the first tool is pulled out. This hole can be filled up again by the second tool by moving the plasticized material, so that the material thickness of the components connected to one another is essentially constant in the work area even after the friction stir welding.

The most important process parameters in friction stir spot welding are the speed and direction of rotation of the individual tools and the contact pressure of the tools and the holding stamp. In particular, the immersion speed of the tools into the components results for a given material of the components. The tools can be controlled in particular via position control and/or force control.

In particular, the first tool and the second tool can rotate at different speeds and be advanced along the axial direction. The directions of rotation and infeed directions can also differ from one another.

In contrast to known friction stir welding devices, the holding stamp is not designed in such a way that it surrounds the tools and is therefore designed in the form of a ring or ring-cylindrical at least on an inner peripheral surface. The holding stamp proposed here is designed in particular at a distance from the second tool, so that the first welding tool can be moved relative to the holding stamp in the radial direction running transversely to the axial direction.

By changing the geometry of the holding stamp, the tools and also the holding stamp can be adapted to the requirements of an assembly intended for a battery cell. In particular, the rotating tools of the first welding tool can be made smaller without having to change the contact surface that is required to fix the components against rotation. Instead of the contact surface immediately surrounding the tools and thereby creating a ring-shaped impression in the components, the contact surface is now arranged at least partially at a distance from the friction stir welded connection. In particular, this contact surface can be designed in such a way that an impression of the contact surface is produced in the components at locations of the assembly that are unproblematic for the assembly.

With the replacement of the known ring-shaped holding stamp by a holding stamp that differs in particular from the shape of the tools, the required area of the contact surface can be distributed over a longer extent. With the possibility of not making the contact surface ring-shaped, the tools can also be reduced in diameter, so that the weld point produced or the width of the weld joint produced can be reduced. This means that the friction stir welding process can also be used to manufacture assemblies that are used in battery cells.

In particular, the contact surface runs along a line enclosing the work area and has a different width of the contact surface along the line.

In particular, the working area has an elongated shape, so that the first welding tool can only be moved along a straight line relative to the holding stamp. This allows multiple spot welds along z. B. the straight lines are generated next to each other, so that a running along the straight line, z. B. also continuous, welded connection can be produced without the retaining die having to be implemented between the different weld points.

In particular, the friction stir welding device also includes a second welding tool that can be or is arranged together with the first welding tool in the work area and can be operated at least partially simultaneously with the first welding tool to form a friction stir welded connection.

In particular, the tools for forming the friction stir welded connection have a maximum diameter of at most 10 millimeters.

In particular, the friction stir welding device also includes a device for generating a protective atmosphere at least in the work area. The facility includes B. an enclosure of at least the work area, so that a protective gas, in particular an inert gas, arranged or a vacuum or negative pressure can be generated.

1. a) Bereitstellen einer Rührreibschweißvorrichtung, insbesondere der beschriebenen Rührreibschweißvorrichtung; zumindest umfassend
   • • ein erstes Schweißwerkzeug mit einem, sich entlang einer axialen Richtung erstreckenden, zylindrischen ersten Werkzeug sowie einem sich entlang der axialen Richtung erstreckenden hohlzylindrischen zweiten Werkzeug, das sich um das erste Werkzeug herum erstreckt; sowie
   • • einen Haltestempel mit einer Kontaktfläche, die einen Arbeitsbereich des ersten Schweißwerkzeugs umschließt;
2. b) Bereitstellen der Mehrzahl von Bauteilen, die sich in dem Verbindungsbereich überlagern und Anordnen der Mehrzahl von Bauteilen in der Rührreibschweißvorrichtung; wobei der Haltestempel den Verbindungsbereich mit der Kontaktfläche umschließt und über die Kontaktfläche die Bauteile in einer Lage zueinander fixiert; und dann
3. c) Rotieren der Werkzeuge um die Drehachse und Bewegen der Werkzeuge entlang der axialen Richtung gegenüber den Bauteilen und Erzeugen einer Rührreibschweißverbindung, durch das die Mehrzahl der Bauteile miteinander verbunden werden; und dann
4. d) Bewegen des ersten Schweißwerkzeugs in einer quer zur axialen Richtung verlaufenden radialen Richtung relativ zu dem Haltestempel und Erzeugen einer weiteren Rührreibschweißverbindung zur Ausbildung der Baugruppe.

Während der Schritte c) und d) sind die Bauteile durch den Haltestempel fixiert und der Arbeitsbereich bleibt unverändert.A method for producing an assembly is also proposed, the assembly comprising a plurality of components which are arranged at least partially overlapping one another in a connection area. The procedure comprises at least the following steps:

1. a) providing a friction stir welding device, in particular the described friction stir welding device; at least extensively
   • • a first welding tool having a cylindrical first tool extending along an axial direction and a hollow-cylindrical second tool extending along the axial direction and extending around the first tool; as well as
   • • a holding stamp with a contact surface that encloses a working area of the first welding tool;
2. b) providing the plurality of components superimposed in the connection area and arranging the plurality of components in the friction stir welding device; wherein the holding stamp encloses the connection area with the contact surface and fixes the components in a position relative to one another via the contact surface; and then
3. c) rotating the tools about the axis of rotation and moving the tools along the axial direction relative to the components and creating a friction stir weld joint by which the plurality of components are connected to one another; and then
4. d) moving the first welding tool in a radial direction transverse to the axial direction relative to the holding stamp and creating a further friction stir weld joint to form the assembly.

During steps c) and d) the components are fixed by the holding stamp and the working area remains unchanged.

The above (non-exhaustive) division of the method steps into a) to d) is primarily intended to serve only as a distinction and does not impose any order and/or dependency. The frequency of the process steps, e.g. B. may vary. Steps b), c) and d) can be repeated several times after step a) has been carried out once (for a large number of identical components). It is also possible for method steps to at least partially overlap one another in terms of time. Process steps c) and d) are very particularly preferably carried out one after the other, but if necessary at least partially in parallel. In particular, steps a) through d) are performed in the order listed.

The assembly is particularly suitable for storing electrical energy. The components can be, for example, a component for a (rechargeable) lithium-ion battery. In this context, the component can, for example, be a component for a (lithium form an ion) cell. The assembly comprises at least one cell stack for storing electrical energy and at least one contact sheet for making electrical contact with the at least one cell stack. As a rule, after the connection of cell stack and contact sheet as described here, several assemblies produced in this way can be connected to form a battery cell. The assembly may include a single cell stack. Furthermore, the assembly can include (precisely) two contact sheets (or even more than two).

The method serves in particular to electrically conductively connect the contact sheet to the (each individual) foil stack, so that the at least one foil stack can be connected to a circuit via the contact sheet. The contact plate forms, for example, an electrical connection of the assembly or an electrical connection element of the assembly for connecting the assembly to components external to the assembly or other components or assembly groups.

According to step a), a friction stir welding device is provided, in particular the friction stir welding device described. The friction stir welding device comprises in particular at least one first welding tool with a cylindrical first tool extending along an axial direction and a hollow-cylindrical second tool extending along the axial direction, which extends around the first tool. The second tool surrounds the first tool in particular directly and without any appreciable distance. The axes of rotation of the two tools are arranged coaxially to one another. The friction stir welding device also includes a holding stamp with a contact surface that encloses a working area of the first welding tool. The holding stamp is used to fix the location or position of the components to be connected.

According to step b), in particular, the plurality of components are provided, which overlap in the connection region, and the plurality of components are arranged in the friction stir welding device. In particular, the holding stamp encloses the connection area with the contact surface and fixes the components in one position relative to one another via the contact surface.

The plurality of components includes, in particular, the stack of a large number of cell foils and the contact sheet. In particular, the cell foils are provided with a coating (eg active material) outside the connection area, with the cell foils being uncoated in the connection area. The cell foils are arranged in a stack, with at least the uncoated areas being arranged in alignment with one another along the axial direction. In particular, the film stack comprises at least 10, preferably at least 20, particularly preferably at least 30 or even at least 50 or at least 75 cell films.

The contact sheet is arranged in particular in such a way that it is arranged at least along the axial direction partially in alignment with the uncoated areas of the cell foils, so that the stack of cell foils and the contact sheet form a common connection area.

The holding stamp makes contact with the surface of the contact sheet and/or the surface of at least one cell foil. The stack of cell foils and the contact plate are thus fixed by the holding stamp.

A counter-holder or a solid base or a third welding tool can be provided for clamping and fixing the components, which is arranged at least partially flush with the holding stamp and/or with the first or second welding tool along the axial direction.

According to step c), the tools are rotated about the (common) axis of rotation and the tools are moved along the axial direction relative to the components and a friction stir welded connection is produced, by which the majority of the components are connected to one another. The friction stir welded connection includes in particular all components, ie in particular a contact plate and all cell foils of the stack. The friction stir weld connection is particularly similar to a spot weld connection, since the tools only rotate during step c), but in particular are not moved along a radial direction running transversely to the axial direction.

According to step d), the first welding tool is moved in a radial direction running transversely to the axial direction relative to the holding stamp and a further friction stir welded connection is produced for forming the assembly. In particular, the holding stamp is not moved between steps c) and d). In particular, only the tools are moved in relation to the holding stamp, so that the further friction stir welded connection produced in step d) is spaced apart from the friction stir welded connection produced in step c) or arranged only partially overlapping with it. During steps c) and d), the components are fixed by the holding stamp and the working area, which is enclosed by the holding stamp and in which the stirring friction welded connections are generated remains unchanged.

In particular, the method includes several steps d), d. H. a large number of friction stir welded joints can be produced in the work area without the holding stamp being released.

In particular, a protective atmosphere is generated at least during steps c) and d), at least in the work area. For this purpose, the working area is subjected in particular to a protective gas, in particular an inert gas, or a vacuum or negative pressure.

In particular, the friction stir welding device also includes a second welding tool, which is arranged together with the first welding tool in the work area at least during one of steps c) and d) and which produces a friction stir welded connection at least partially simultaneously with the first welding tool.

The statements regarding the first welding tool apply in particular equally to the second welding tool.

In particular, an assembly for a battery cell is proposed. The assembly comprises at least a large number of cell foils stacked on top of one another for storing electrical energy and at least one contact plate. The cell foils form a foil stack in a connection area and the foil stack is connected to the contact plate by at least one friction stir weld connection. The friction stir welded connection is produced in particular with the friction stir welding device described or by the method described.

In particular, the assembly has the markings on the surface of at least one of the components caused by the holding stamp or its contact surface.

In particular, the holding stamp and the welding tool are arranged on the contact sheet or on one of the cell foils. The arrangement preferably takes place on one of the cell foils, so that the connection of the contact plate in the context of the formation of the friction stir weld connection takes place only via the plasticization of the material of the components starting from the cell foil.

In particular, the contact sheet has a thickness, at least in the connection area, which is between 0.2 and 3 millimeters and comprises at least 99.0% by weight of either copper or aluminum. In particular, the thickness is between 20 μm and 1 (one) millimeter, preferably between 50 μm and 500 μm.

In particular, the contact sheet has a coating which has a maximum thickness of 2 μm and which comprises at least 99.0% by weight nickel. The thickness is in particular at least 0.1 μm.

In particular, each cell foil has a thickness of less than 0.1 millimeters, in particular less than 0.07 millimeters.

In particular, the materials of the components, in particular the cell foils and/or the contact sheet, contain at least 99.0% copper or at least 99.0% aluminum.

In particular, at least one system for data processing is provided which has means which are suitably equipped, configured or programmed to carry out the method or which carry out the method.

In particular, the friction stir welding device comprises a system for data processing, e.g. B. a control device that has means for executing the steps of the method and / or has means that are suitably equipped, configured or programmed to execute the steps of the method or that execute the method.

The funds include B. a processor and a memory in which instructions to be executed by the processor are stored, as well as data lines or transmission devices which enable transmission of instructions, measured values, data or the like between the listed elements.

A computer program is also proposed, comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method described or the steps of the method described.

A computer-readable storage medium is also proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the method described or the steps of the method described.

The statements on the method can be transferred in particular to the friction stir welding device, the assembly, the system for data processing and/or the computer-implemented method (ie the computer program and the computer-readable storage medium) and vice versa.

The use of indefinite articles (“a”, “an”, “an” and “an”), particularly in the claims and the description reflecting them, is to be understood as such and not as a numeral. Correspondingly introduced terms or components are to be understood in such a way that they are present at least once and in particular can also be present several times.

As a precaution, it should be noted that the numerals used here (“first”, “second”, ...) primarily (only) serve to distinguish between several similar objects, sizes or processes, i.e. in particular no dependency and/or sequence of these objects, sizes or make processes mandatory for each other. Should a dependency and/or order be necessary, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described embodiment. If a component can occur several times (“at least one”), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

• 1: das bekannte Verfahren Rührreibschweißen in unterschiedlichen Verfahrenszuständen;
• 2: eine bekannte Rührreibschweißvorrichtung, in einer Seitenansicht im Schnitt;
• 3: die Rührreibschweißvorrichtung nach 2 in einer Ansicht entlang der axialen Richtung;
• 4: eine Rührreibschweißvorrichtung in einer perspektivischen Ansicht;
• 5: die Rührreibschweißvorrichtung nach 4 in einer Ansicht entlang der axialen Richtung;
• 6: eine Baugruppe mit einer Rührreibschweißverbindung in einer Seitenansicht im Schnitt;
• 7: die Rührreibschweißvorrichtung nach 4 und 5 in einer Seitenansicht im Schnitt;
• 8: eine alternative Ausführungsvariante einer Rührreibschweißvorrichtung in einer perspektivischen Ansicht;
• 9: die eine Rührreibschweißvorrichtung nach 8 in einer Ansicht entlang der axialen Richtung; und
• 10: eine weitere alternative Rührreibschweißvorrichtung in einer Seitenansicht im Schnitt.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be pointed out that the invention should not be limited by the exemplary embodiments given. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. Show it:

• 1 : the well-known friction stir welding process in different process states;
• 2 : a known friction stir welding device, in a side view in section;
• 3 : the friction stir welding device after 2 in a view along the axial direction;
• 4 : a friction stir welding device in a perspective view;
• 5 : the friction stir welding device after 4 in a view along the axial direction;
• 6 1: an assembly with a friction stir welded connection in a side view in section;
• 7 : the friction stir welding device after 4 and 5 in a side view in section;
• 8th : an alternative embodiment variant of a friction stir welding device in a perspective view;
• 9 : which according to a friction stir welding device 8th in a view along the axial direction; and
• 10 : another alternative friction stir welding device in a side view in section.

1 shows the well-known friction stir welding process in different process states. 2 shows a known friction stir welding device 1, in a side view in section. 3 shows the friction stir welding device 1 2 in a view along the axial direction 5. The 1 until 3 are described together below.

The friction stir welding device 1 comprises a holding stamp 8, a cylindrical first tool 6 and a sleeve-shaped second tool 7. During friction stir spot welding, individual spot welds are created by a rotating, pin-shaped first tool 6 and a rotating, hollow-cylindrical second tool 7 that surrounds the first tool 6 , with great force in the upper of the two (in 1 ) or the several ( 2 ) illustrated components 2, 3, z. B. sheets are pressed, which are superimposed in the lap joint. The material of the upper, first component 2 is plasticized by the frictional heat and the high pressure, so that the tip of the first tool 6 and/or the second tool 7 dips into the joining zone between the components 2, 3 and there the materials of the components 2 , 3 or the oxides present on the surfaces. The components 2 , 3 are fixed in their position relative to one another and to the first welding tool 4 by the holding stamp 8 . The tools 6 , 7 are moved in the axial direction 5 , so that the material displaced by the immersion of a tool 6 , 7 into the components 2 , 3 can escape within the working area 12 delimited by the holding stamp 8 .

When using one-piece tools 6, 7, a hole remains in the components 2, 3 after the first tool 6 has been pulled out. This hole can be filled up again by the second tool 7 by moving the plasticized material, so that the material thickness of the interconnected components 2, 3 is essentially constant in the working area 12 even after the friction stir welding, see 1 , right image, in which the generated friction stir welded connection 10 is shown.

In order to ensure that the centrifugal forces generated by the tools 6, 7 and the friction only act in the desired area, the use of a strong holding stamp 8 is necessary. This requirement prevents the tools 6, 7 from being smaller. The standard size used is therefore 12 mm [millimeters] in diameter, making it impossible to use the method when the desired area is e.g. B. would be less than 10 mm. However, the requirements in the production of battery cells include smaller work areas 12 or connection areas 20 (see 3 ). In 3 shows that the connection area 20, i.e. the area in which a connection can be created due to the overlapping arrangement of the components 2, 3, is smaller than the largest diameter 16 of the tools 6, 7.

4 shows a friction stir welding device 1 in a perspective view. 5 shows the friction stir welding device 1 4 in a view along the axial direction 5. 6 shows an assembly 19 with a friction stir welded connection 10 in a side view in section. 7 shows the friction stir welding device 1 4 and 5 in a side view in section. The 4 until 6 are described together below. To the remarks 1 until 3 is referenced.

The assembly 19 comprises a multiplicity of cell foils 21 (first component 2) stacked on top of one another for storing electrical energy and a contact plate 22 (second component 3). The cell foils 21 form a foil stack 23 in a connection area 20 and the foil stack 23 is connected to the contact plate 22 by at least one friction stir weld connection 10 .

The connection area 20 is formed in the overlap area formed by the overlapping components 2, 3. In the case of the assembly 19, the connection area 20 is arranged adjacent to a sealing seam 25 of the battery cell, by means of which the housing of the battery cell is sealed. The connection area 20 is later arranged inside the housing of the battery cell, so that the contact plate 22 extends from the connection area 20 via the sealing seam 25 to the outside of the housing.

The holding stamp 8 and the first welding tool 4 are arranged on the uppermost of the cell foils 21 . The contact plate 22 is connected as part of the formation of the friction stir welded connection 10 only via the plasticization of the material of the cell foils 21 starting from the uppermost cell foil 21.

The friction stir welding device 1 comprises a first welding tool 4 with a cylindrical first tool 6 extending along an axial direction 5 and a hollow-cylindrical second tool 7 extending along the axial direction 5 and extending around the first tool 6 . Furthermore, the friction stir welding device 1 comprises a holding stamp 8 with a contact surface 9, via which the holding stamp 8 fixes the components 2, 3 in a position relative to the tools 6, 7 during the production of the friction stir welded connection 10.

The tools 6 , 7 can be rotated relative to the holding stamp 8 and independently of one another about an axis of rotation 11 extending along the axial direction 5 and can be moved along the axial direction 5 to produce a friction stir welded connection 10 of the components 2 , 3 . The contact surface 9 encloses a working area 12 for the first welding tool 4 , in which the first welding tool 4 can be moved in a radial direction 12 running transversely to the axial direction 5 relative to the holding stamp 8 .

The first tool 6 and the second tool 7 can rotate at different speeds and be advanced along the axial direction 5 . The directions of rotation and infeed directions can also differ from one another.

In contrast to known friction stir welding devices 1, the holding stamp 8 is not designed in such a way that it surrounds the tools 6, 7 and is therefore designed in the form of a ring or ring-cylindrical at least on an inner peripheral surface. The holding stamp 8 proposed here is designed at a distance from the second tool 7 so that the first welding tool 4 can be moved in the radial direction 13 running transversely to the axial direction 5 relative to the holding stamp 8 .

By changing the geometry of the holding stamp 8, the tools 6, 7 and also the holding stamp 8 can be adapted to the requirements of an assembly 19 provided for a battery cell. The rotating tools 6, 7 of the first welding tool 4 can be made smaller without having to change the contact surface 9, which is required to fix the components 2, 3 against twisting. Instead of the contact surface 9 immediately surrounding the tools 6 , 7 and thereby creating an annular imprint in the components 2 , 3 , the contact surface 9 is now at least partially spaced from the friction stir welded connection 10 . This contact surface 9 can be designed in such a way that an impression of the contact surface 9 is left in the components 2, 3 at for the assembly 2, 3 unproblematic points of the assembly 2, 3 is generated.

With the replacement of the known ring-shaped holding stamp 8 by a holding stamp 8 that differs from the shape of the tools 6, 7, the required area of the contact surface 9 can be distributed over a longer extent. With the possibility of not making the contact surface 9 ring-shaped, the diameter 16 of the tools 6, 7 can also be reduced, so that the weld point produced or the width of the friction stir weld joint 10 produced can be reduced. The friction stir welding method can thus also be used to produce assemblies 19 that are used in battery cells.

The contact surface 9 runs along a line enclosing the working area 12 and has a different width 14 of the contact surface 9 along the line.

The working area 12 has such an elongated shape that the first welding tool 4 can only be moved along a straight line relative to the holding stamp 8 . In this way, several spot welds or friction stir weld connections 10 can be produced next to one another along the straight line, so that a z. B. also continuous, friction stir welded connection 10 can be produced without the holding stamp 8 having to be converted between the different friction stir welded connections 10 .

The friction stir welding device 1 also has a device 17 (see 4 ) for generating a protective atmosphere 18 at least in the work area 12. The device 17 includes z. B. an enclosure of at least the work area 12, so that a protective gas, in particular an inert gas, arranged or a vacuum or negative pressure can be generated.

According to step a) of the method, a friction stir welding device 1 is provided. The friction stir welding device 1 comprises a first welding tool 4 with a cylindrical first tool 6 extending along an axial direction 5 and a hollow-cylindrical second tool 7 extending along the axial direction 5, which extends around the first tool 6. The second tool 7 surrounds the first tool 6 directly and without any appreciable distance. The axes of rotation 11 of the two tools 6, 7 are arranged coaxially to one another. The friction stir welding device 1 also includes a holding stamp 8 with a contact surface 9 which encloses a working area 12 of the first welding tool 4 . The holding stamp 8 is used to fix the location or position of the components 2, 3 to be connected.

According to step b), the plurality of components 2, 3, which overlap in the connection area 20, are provided and the plurality of components 2, 3 are arranged in the friction stir welding device 1. The holding stamp 8 encloses the connection area 20 with the contact surface 9 and is fixed via the contact surface 9, the components 2, 3 in a position to each other.

The plurality of components 2, 3 comprises the stack of a large number of cell foils 21 and the contact plate 22. The cell foils 21 are provided with a coating (e.g. active material) outside of the connection area 20, with the cell foils 21 being uncoated in the connection area 20 . The cell foils 21 are arranged in a stack, with at least the uncoated areas being arranged in alignment with one another along the axial direction 5 . The contact sheet 22 is arranged in such a way that it is at least partially aligned along the axial direction 5 with the uncoated areas of the cell foils 21, so that the stack of cell foils 21 and the contact sheet 22 form a common connection area.

A solid base 26 is provided for clamping and fixing the components 2 , 3 , which is arranged in alignment with the holding stamp 8 and the welding tool 4 along the axial direction 5 .

According to step c), the tools 6, 7 are rotated about the (common) axis of rotation 11 and the tools 6, 7 are moved along the axial direction 5 relative to the components 2, 3 and a friction stir welded connection 10 is created, through which the majority of the Components 2, 3 are connected to each other. The friction stir weld connection 10 includes all components 2, 3, i.e. the contact plate 22 and all cell foils 21 of the foil stack 23. The friction stir weld connection 10 is similar to a spot weld connection, since the tools 6, 7 only rotate during step c) but not along a direction transverse to the axial direction 5 extending radial direction 13 are moved.

According to step d), the first welding tool 4 is moved in a radial direction 13 running transversely to the axial direction 5 relative to the holding stamp 8 and a further friction stir weld connection 10 is produced to form the assembly 19. The holding stamp 8 is between steps c) and d) just not moved. Only the tools 6, 7 are moved in relation to the holding stamp 8, so that the further friction stir welded connection 10 produced in step d) differs from the friction stir welded connection 10 produced in step c). spaced or arranged with this only partially overlapping. During steps c) and d), the components 2, 3 are fixed by the holding stamp 8 and the working area 12, which is enclosed by the holding stamp 8 and in which the friction stir welded connections 10 are produced, remains unchanged.

8th shows an alternative embodiment variant of a friction stir welding device 1 in a perspective view. 9 shows the one friction stir welding device 1 after 8th in a view along the axial direction 5. The 8th and 9 are described together below. On the remarks on the 1 until 7 is referenced.

The friction stir welding device 1 additionally includes a second welding tool 15 that is arranged together with the first welding tool 4 in the work area 12 and can be operated at least partially simultaneously with the first welding tool 4 to form a friction stir welded joint 10 .

10 shows another alternative friction stir welding device 1 in a side view in section. On the remarks on the 1 until 9 is referenced.

Here, a third welding tool 24 is provided for clamping and fixing the components 2, 3, which is arranged along the axial direction 5 at least partially aligned with the holding stamp 8 and the first welding tool 4 or second welding tool 15.

Reference List

1

friction stir welding device

2

first component

3

second component

4

first welding tool

5

axial direction

6

first tool

7

second tool

8th

holding stamp

9

contact surface

10

friction stir welded connection

11

axis of rotation

12

Workspace

13

radial direction

14

Broad

15

second welding tool

16

diameter

17

Furnishings

18

protective atmosphere

19

module

20

connection area

21

cell foil

22

contact plate

23

foil stack

24

third welding tool

25

sealing seam

26

document

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• CN 104741769A [0011]
• EP 1884308 B1 [0013]
• US 10201873 B2 [0015]
• US200206840A1 [0016]

Claims (10)

Friction stir welding device (1) for connecting a plurality of components (2, 3) arranged at least partially overlapping one another by generating frictional heat and by stirring a material of at least one component (2, 3), at least comprising • a first welding tool (4) with a cylindrical first tool (6) extending along an axial direction (5) and a hollow-cylindrical second tool (7) extending along the axial direction (5), which extends around the first tool (6) extends around; as well as • a holding stamp (8) with a contact surface (9) via which the holding stamp (8) fixes the components (2, 3) in a position relative to the tools (6, 7) during the production of a friction stir weld connection (10); wherein the tools (6, 7) for producing the friction stir welded connection (10) can be rotated relative to the holding stamp (8) and independently of one another about an axis of rotation (11) extending along the axial direction (5) and can be moved along the axial direction (5). are; the contact surface (9) enclosing a working area (12) for the first welding tool (4), in which the first welding tool (4) can be moved in a radial direction (13) running transversely to the axial direction (5) relative to the holding stamp (8) is movable. Friction stir welding device (1) after Claim 1 , wherein the contact surface (9) runs along a line enclosing the work area (12) and has a different width (14) of the contact surface (9) along the line. Friction stir welding device (1) according to one of the preceding claims, wherein the working area (12) has an elongated shape, so that the first welding tool (4) can only be moved along a straight line relative to the holding stamp (8). Friction stir welding device (1) according to one of the preceding claims, additionally comprising a second welding tool (15) which can be arranged together with the first welding tool (4) in the work area (12) and at least partially simultaneously with the first welding tool (4) to form a further friction stir welded connection (10) can be operated. Friction stir welding device (1) according to one of the preceding claims, wherein the tools (6, 7) for forming the friction stir weld connection (10) have a maximum diameter (16) which is at most 10 millimeters. Friction stir welding device (1) according to one of the preceding claims, additionally comprising a device (17) for generating a protective atmosphere (18) at least in the working area (12). Method for producing an assembly (19), wherein the assembly (19) comprises a plurality of components (2, 3) arranged at least partially overlapping one another in a connection area (20); the method comprising at least the following steps: a) providing a friction stir welding device (1); at least extensively • a first welding tool (4) with a cylindrical first tool (6) extending along an axial direction (5) and a hollow-cylindrical second tool (7) extending along the axial direction (5) around the first tool (6) extends around; as well as • a holding stamp (8) with a contact surface (9) which encloses a working area (12) of the first welding tool (4); b) providing the plurality of components (2, 3) which are superimposed in the connection area (20) and arranging the plurality of components (2, 3) in the friction stir welding device (1); the holding stamp (8) enclosing the connection area (20) with the contact surface (9) and fixing the components (2, 3) in one position relative to one another via the contact surface (9); and then c) Rotating the tools (6, 7) about the axis of rotation (11) and moving the tools (6, 7) along the axial direction (5) relative to the components (2, 3) and creating a friction stir welded connection (10) by the plurality of components (2, 3) are connected to one another; and then d) moving the first welding tool (4) in a radial direction (13) running transversely to the axial direction (5) relative to the holding stamp (8) and producing a friction stir welded connection (10) to form the assembly (19); wherein during steps c) and d) the components (2, 3) are fixed by the holding stamp (8) and the working area (12) remains unchanged. procedure after Claim 7 , wherein at least during steps c) and d) a protective atmosphere (18) is generated at least in the work area (12). Method according to any of the preceding Claims 7 and 8th , wherein the friction stir welding device (1) additionally comprises a second welding tool (15) which is arranged together with the first welding tool (4) in the work area (12) at least during one of steps c) and d) and at least partially simultaneously with the first welding shop tool (4) produces a further friction stir welded connection (10). Assembly (19) for a battery cell, at least comprising a multiplicity of cell foils (21) stacked on top of one another for storing electrical energy and at least one contact plate (22); wherein the cell foils (21) form a foil stack (23) in a connection area (20) and the foil stack (23) is connected to the contact plate (22) by at least one friction stir weld connection (10); wherein the friction stir welded connection (10) is made with a friction stir welding device (1) according to one of the preceding ones patent claims 1 until 6 or by a method according to any of the preceding Claims 7 until 9 is made.

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