Connection of a metallic component and a plastic component

Abstract

Method for joining a metallic component (110) and a plastic component (112), comprising the steps: a) Providing a metallic component (110); b) Providing a plastic component (112) which has at least one recess (118) wherein a metallic connecting element (120) which has a depression (122) for receiving an electrode (124) is located in the recess (118); c) Inserting the electrode (124) into the recess (122) of the connecting element (120) such that the electrode (124) and the connecting element (120) come into contact; d) Pressing the metallic component (110) and the connecting element (120) together; and e) Applying an electric current to the metallic component (110) and the connecting element (120) such that the connecting element (120) connects the metallic component (110) and the plastic component (112) at a connecting surface (130), wherein the recess (122) of the metallic connecting element (120) provided for receiving the electrode (124) is conical and an end part (142) of the connecting element (120) facing the connecting surface (130) has an open bottom (144, 146), wherein the insertion of the electrode (124) into the recess (122) of the connecting element (120) according to step c) is carried out such that the electrode (124) penetrates the recess (122) to at least 75% of the total height of the connecting element (120), characterized in that the electrode (124) is made hollow in order to accommodate the counter electrode (136), separated by a gap (167).

Description

[0001] The present invention relates to a method for joining a metallic component and a plastic component. The method is particularly suitable for use in the production of metal-plastic hybrids from the combination of fiber-reinforced plastics and sheet metal or cast parts. Applications for the composite part are found particularly in vehicle, aircraft, or ship construction, or in the manufacture of electrical devices. State of the art

[0002] Under the term "multi-material lightweight construction," combinations of very different materials are increasingly being used in vehicle construction. In addition to the now more frequently used aluminum-steel composite construction, load-bearing and / or safety-relevant body parts are also being made of fiber-reinforced plastics. In this context, the combination of fiber-reinforced plastics and metal parts is gaining considerable importance.

[0003] When manufacturing metal-plastic hybrids, a distinction is made between a connection between a metallic component and a plastic component made during the injection molding process (in-mold assembly) and a connection made after the injection molding process (post-mold assembly). In a connection made during the injection molding process, a metallic component is placed into a plastic injection mold, with the metallic component and the plastic component being joined together in a form-fitting and, if necessary, material-fitting manner using the injection molding process. In a connection made after the injection molding process, the metallic component and the plastic component are only joined together after they have been shaped, for which a process selected from adhesive bonding, hot riveting, or collar joining is preferably used.

[0004] However, these processes have a number of disadvantages. The time required for bonding to cure the composite part is generally too long for assembly processes in car body construction. Furthermore, the strength of adhesives is so limited that even low levels of sound can cause bonded joints to fail.

[0005] In practice, hot riveting is only suitable for thermoplastics that are fiber-free or contain at most a small amount of fibers. Furthermore, due to the typically low thermal conductivity of the plastic used, hot riveting can generally only be carried out very slowly and also requires the plastic to protrude beyond the metal component. The disadvantage of this method is that it can limit or prevent the use of the composite part in visible areas.

[0006] WO 2003 / 031095 A1 discloses a forming process in which a collar is drawn into a sheet metal part and subsequently inserted into the plastic component for a positive connection. However, collar drawing cannot be performed with materials that are only partially formable, such as high-strength, particularly martensitic steels. Furthermore, collar drawing is a complex forming process that generally requires several forming steps. Furthermore, holes formed during collar drawing limit or prevent the use of the composite part in visible areas.

[0007] DE 10 2012 013 589 A1 and DE 10 2004 025 492 A1 each disclose a self-piercing joining element made of steel, which is pressed through an aluminum component to be joined in a punching process and then welded to a steel component. A related process based on resistance element welding is particularly suitable for use in aluminum-steel composite construction and represents a combination of positive and material bonding. Contrary to the description in DE 10 2004 025 492 A1, however, it was found that the components to be joined heat up when exposed to an electric current to such an extent that this process is unsuitable for composite parts made of plastic and steel, as the plastic can easily be damaged during the heating and / or punching process.

[0008] DE 693 17 969 T2 discloses a method for fastening a carrying handle to the wall of a metal container, which method comprises fastening fastening means to diametrically opposite sides of the container by welding, wherein perforated end sections of the handle are positioned between the container wall and respective sheet metal clamps in such a way that the handle holes are aligned with the locations on the container wall to which the sheet metal clamps are welded, and that the sheet metal clamps are guided through the handle holes and welded to the container wall.

[0009] DE 10 2010 034 183 A1, DE 297 18 724 U1, DE 695 09 201 T2, DE 10 2014 107 911 A1 and EP 0 967 044 A2 disclose further relevant methods for joining a metallic component and a plastic component. Object of the invention

[0010] In view of the prior art presented, the object of the present invention is to provide a method for joining a metallic component and a plastic component, which at least partially overcomes the disadvantages and limitations known from the prior art.

[0011] For this purpose, a method for joining a metallic component and a plastic component is to be proposed which makes it possible to join plastics, in particular fibre-reinforced plastics, with little effort, quickly and with high strength to metallic components, in particular to sheets made of aluminium and / or steel or to castings which are obtainable by means of aluminium die casting.

[0012] The connection thus obtained should also be as light, rigid and flat as possible on one side, be suitable for use in the visible area and, moreover, be mountable even with one-sided accessibility.

[0013] The composite part thus obtained should also be designed to be partially detachable in order to enable the metallic component and the plastic component to be separated from each other without destroying the individual components if necessary, for example during repairs. Disclosure of the invention

[0014] This problem is solved by a method for joining a metallic component and a plastic component with the features of the independent patent claims. Advantageous embodiments can be found in the dependent patent claims.

[0015] In a first aspect, the present invention relates to a method for joining a metallic component and a plastic component. This method serves to firmly join the metallic component and the plastic component to one another, although a conditional detachability is provided, as described in more detail below. The term "joining" the two parts thus refers to the production of a composite part that comprises the two parts and can be treated as an integrated component, wherein the connection is mechanically so stable and strong that the two parts can be separated again from the composite part only by locally removing a composite element creating the connection, in particular by drilling or machining.

[0016] The present process comprises the steps a) to e described below. Steps a) to c) can be carried out in the specified order or in a different order and, preferably, at least partially simultaneously, while steps d) and e) can be carried out sequentially or, preferably, at least partially simultaneously, until the desired composite part is obtained. The individual steps are: a) Providing a metallic component; b) providing a plastic component having at least one recess, wherein a metallic connecting element having a recess for receiving an electrode is located in the recess; c) inserting the electrode into the recess of the connecting element such that the electrode and the connecting element come into contact; d) pressing the metallic component and the connecting element together; and e) applying an electric current to the metallic component and the connecting element in such a way that the metallic component and the plastic component are connected at a connecting surface by means of the connecting element, wherein the recess of the metallic connecting element designed to receive the electrode is conical and an end part of the connecting element facing the connecting surface has an open bottom, wherein the introduction of the electrode into the recess of the connecting element according to step c) is carried out in such a way that the electrode penetrates into the recess to at least 75% of a total height of the connecting element, and wherein the electrode is hollow in order to receive the counter electrode, separated by a gap.

[0017] According to step a) of the present method, a metallic component is provided. Here, the term "metallic component" refers to a single-part or multi-part extended object which, in its entirety or at least on a surface intended for establishing the connection, also referred to as the "connection surface," comprises a metallic material to the plastic component, which, however, may be completely or partially coated, in particular with a paint finish.The metallic material basically comprises any metal or any metallic alloy, whereby the metal or alloy has sufficient electrical conductivity and thus sufficient thermal conductivity as well as sufficient current carrying capacity with regard to both the selected material and its layer thickness, in order to enable sufficient heating of the metallic component for the application of resistance welding, arc welding or a soldering process involving the metallic component.

[0018] For this purpose, the surface of the metallic component is designed such that it has at least one surface suitable for receiving the plastic component intended for the connection. In particular, the surfaces of both the metallic component and the plastic component can be largely planar surfaces that can be easily placed against one another at least at the connection surface. However, other designs are possible, in particular surfaces that have a mutually aligned fit.

[0019] In a preferred embodiment, the metallic component can be a sheet metal part, the material of which preferably comprises aluminium or steel. The term “sheet metal part” here refers to a design of the metallic component in the form of an object whose thickness is much smaller than its length and width, preferably by at least a factor of 10, wherein the sheet metal part can be subjected to a further three-dimensional shaping process after its production, which is generally easy to carry out due to its small thickness. In an alternative embodiment, the metallic component can be in the form of a casting, which can be produced in particular by die-casting aluminium. The term “cast part” refers to a metallic shaped part whose geometry is determined by the solidification of a melt in a mould. However, other designs of the metallic component are conceivable.

[0020] The metallic component, in particular the sheet metal, can be provided with a coating, in particular with at least one layer of paint or a corrosion protection layer, on at least one side, i.e. on one or both sides or, depending on the design of the metallic component, even on multiple sides. This type of design is particularly suitable for automotive construction, in which the metallic component, which may be in the form of a body or a part thereof, is heated for some time to temperatures of approximately 150° to approximately 220°C to cure the paint or coating. This means that the metallic component and plastic component can only be joined after the paint has been baked, in order to avoid thermal degeneration, warping, damage or discoloration of the plastic component during the paint baking process.In this advantageous embodiment, the present method can therefore be carried out on metallic components, in particular sheet metal, that are already coated on one or both sides. For this purpose, the coating can be removed or penetrated locally before carrying out the present method or by the present method itself, in particular by applying a force to the connecting element and / or a counter electrode as a result of resistance heating and / or the arc.

[0021] In a particular embodiment, the metallic component can be connected to an electrode, hereinafter referred to as the "counter electrode." The term "electrode" typically refers to a pin-, tip-, or plate-shaped element designed to generate or dissipate electrical currents. For this purpose, the electrode can be made of a highly electrically conductive material, preferably a metal, in particular copper, steel, or aluminum, or alternatively, graphite. Other embodiments are conceivable.

[0022] In the preferred case of a sheet metal as the metallic component, the counter electrode connected to the sheet metal can be plate-shaped. Alternatively, the metallic component itself can serve as the counter electrode. As a further alternative, the counter electrode can be inserted into the electrode, separated from the electrode by a gap. For this purpose, the electrode inserted into the connecting element can be hollow in order to accommodate the counter electrode, which can come into direct contact with the metallic component during the process. This makes it possible to contact the metallic component within the connecting element. In order to absorb the resulting process forces, a counter holder can be used on the other side of the metallic component, although this cannot be designed to act as a counter electrode at the same time.To prevent the counterholder from penetrating the metallic component as a result of the process forces, the counterholder can be rounded at its edge, adapted to the component geometry, and / or at least partially made of a softer material than the metallic component, preferably a plastic, especially Teflon. However, other configurations are possible.

[0023] According to step b) of the present method, a plastic component is provided. The term "plastic component" basically refers to any molded part that at least partially, preferably completely, comprises any plastic, which can also be referred to with the term "polymer," as its material. In a particularly preferred embodiment, the plastic can additionally comprise a fiber material, i.e. a material that has a fiber content, in particular short fibers and / or long fibers, which can serve to reinforce the plastic, in particular with regard to its mechanical and / or thermal properties.In a preferred embodiment, the plastic component can comprise a plastically deformable thermoplastic or a thermoset that is no longer plastically deformable after curing, or a mixture thereof. The plastic can be a fiber-reinforced plastic, preferably a short-fiber-reinforced plastic or a long-fiber-reinforced plastic, in particular a carbon-fiber-reinforced plastic. The plastic component can be manufactured by a known process, in particular by injection molding or lamination.

[0024] Furthermore, the plastic component provided according to step b) has at least one recess in which a metallic connecting element is located. The term “connecting element” or “joining element” refers to an object present in addition to the two parts to be connected, namely the metallic component and the plastic component, which is designed to create the desired connection between the two parts to be connected. The connecting element can be inserted into an existing recess that was already provided during the manufacture of the plastic component. In a special embodiment, the plastic component can have at least two spatially separated recesses, wherein at least two metallic connecting elements can be inserted into the recesses simultaneously or one after the other.If the two connecting elements are used consecutively, the connecting element used first can enable particularly good contact between the metallic component and the electrode or counterelectrode. If, on the other hand, the two connecting elements are used simultaneously, an alternating electrical current can preferably be used to establish the connection, in particular in order to achieve the most uniform possible connection between the metallic component and the plastic component. One connecting element can serve as a counterelectrode for the other; additional contact, in particular with already painted metallic components, is not necessary. In a special embodiment, the two electrodes can be mechanically firmly connected to one another and can therefore act on the metallic component in the form of a common movement.Alternatively, the two electrodes can be movable independently of each other and connected to each other, preferably via at least one spring. However, other designs are possible.

[0025] Preferably, the connecting element can be inserted into the plastic component in a form-fitting and / or force-fitting manner. The term “form-fitting” refers to a connection in which the parts to be connected engage in such a way that they cannot be separated from one another without the transfer of force. This can be achieved, as can be seen from the following figures, by a correspondingly designed shape, in particular of the connecting element, but also of the plastic component, for example in the form of projections of the connecting element penetrating into the plastic component. Other designs are possible. In contrast, the term “force-fitting” refers to a connection between the two parts which, due to a unilateral or mutual application of force, exists for as long as it is not exceeded by a counterforce generated by static friction.In the present case, a force connection can be achieved in particular by the plastic component being able to exert a prestress on the connecting element, for example by designing the shape of the recess in the connecting element accordingly.

[0026] In an alternative embodiment, the connecting element can already be integrated into the plastic component during its manufacture. Here, too, the connecting element can preferably be integrated into the plastic component in a form-fitting and / or force-fitting manner. For this purpose, the metallic connecting element can be inserted into a plastic injection mold so that the metallic connecting element and the plastic component can be connected to one another in a form-fitting and, if necessary, material-fitting manner during injection molding. Other embodiments are possible, however. Thus, in this alternative embodiment, the plastic component provided according to step b) already has a metallic connecting element, which is positioned in the recess created thereby in the plastic component.

[0027] The connecting element can preferably comprise a material selected from steel or aluminum. Steels which do not exhibit hardening even at a high cooling rate can preferably be used here. Such steels are characterized in particular by a low carbon content on the one hand and a high content of chromium, nickel and / or manganese on the other. Furthermore, the connecting element can advantageously have a coating of an adhesion promoter and / or an electrically and / or thermally insulating material on its outer surface facing the recess in the plastic component in order to enable the best possible and intimate connection to the plastic component, to prevent contact corrosion with an existing fiber material and overall to avoid thermal stress on the plastic as far as possible.For this purpose, the connecting element can preferably be manufactured by means of a forming process, in particular by means of hot or cold extrusion or sheet metal forming. Alternatively, the connecting element itself can be manufactured by injection molding; in this case, fibers can preferably be introduced into the connecting element, in particular by weaving or threading.

[0028] The connecting element can, in principle, take any suitable shape, although a rotationally symmetrical, oval, or elongated basic shape is preferred. Particularly with respect to the connecting surface, the connecting element can have a head portion facing away from the connecting surface, an end portion facing the connecting surface, and a central portion located between the head portion and the end portion.

[0029] The central part can preferably be parallel or conical in shape and further has a recess designed to receive an electrode. The recess is preferably located on the inner surface of the connecting element facing away from the recess in the plastic component and can in particular also be designed as a through-hole towards the end part of the connecting element. The recess designed to receive the electrode is also conical in shape. Corresponding preferred embodiments can be found in the following figures. The central part can have a wall thickness that is small in relation to the overall dimensions of the connecting element, preferably less than 2.0 mm, particularly preferably less than 1.0 mm.The term “total dimensions” refers to a maximum extension of the connecting element in one direction, preferably the entire height of the connecting element, whereby the term “small” refers to a value of at most 20%, preferably of at most 10% of the total dimensions of the connecting element.

[0030] The head portion of the connecting element can preferably feature a flange or a head configured to improve the above-described positive engagement between the connecting element and the plastic component. In a particular embodiment, the connecting element, similar to a screw or nail head, can have a greater width, particularly at the head portion, compared to the width of the connecting element at the end portion. These and other advantageous embodiments can be found in the following figures.

[0031] The end portion of the connecting element is open. For this purpose, the end portion can preferably have a contact surface, which can be aligned with respect to the metallic component. In particular, to increase the concentration of the electrical current and thus to increase the localization of heat input, the contact surface can be locally reduced. For this purpose, a shoulder, a pin for arc ignition, a phase, and / or a bevel of the end portion can be provided. Advantageous embodiments for the end portion of the connecting element can be found in the following figures.

[0032] According to step c) of the present method, the electrode is inserted or immersed into the recess provided for it in the connecting element, wherein the insertion or immersion takes place such that the electrode and the connecting element come into contact with one another. As mentioned above, the term "electrode" usually refers to a pin-, tip-, or plate-shaped element made of a highly electrically conductive material, which is designed to provide or conduct electrical currents. Due to the conical design of the recess in the central part of the connecting element, the electrode to be inserted therein can preferably be pin- or tip-shaped. In a preferred embodiment, the insertion or immersion of the electrode into the recess of the connecting element can take place by pressing the connecting element onto the electrode.

[0033] According to the invention, the electrode is introduced into the recess of the connecting element according to step c) in such a way that the electrode penetrates into the recess to at least 75% of the total height of the connecting element. Since the end side of the connecting element is designed to be open, it can also be particularly advantageous for the electrode to penetrate into the recess of the connecting element to at least 80%, preferably 90%. Due to the intimate contact that can be achieved in this way between the electrode and the connecting element, a low contact resistance between the electrode and the connecting element can be achieved. At the same time, the connecting element can be fixed to the electrode in a force-fitting manner in such a way that the connecting element can also be positioned and handled by moving the electrode.

[0034] According to step d) of the present method, the plastic component connected to the electrode and the connecting element is placed on, on, or under the metallic component at the connecting surface and pressed together. Conventional methods can be used to press the metallic component and the connecting element together. In a particularly preferred embodiment, the electrode, which is non-positively connected to the connecting element, can be used for this purpose. The metallic component can rest on a base and / or be mounted on a counterholder.

[0035] According to step e) of the present method, an electric current is applied to the connecting element and the metallic component after, during, or before step d) in such a way that an indirect connection between the metallic component and the plastic component is established by means of the connecting element. To establish a current flow, the connecting element is connected to the electrode, while the metallic component can be connected to a counterelectrode or can itself represent the counterelectrode. As already mentioned, the counterelectrode can alternatively be integrated into the electrode. The current flow can be direct or alternating electrical current.For the current flow, this results in a particularly low contact resistance between the electrode and the connecting element, which is preferably in form-fitting contact with it, and a high contact resistance between the electrode and the metallic component. Depending on the design of the plastic component and the associated components, electrode and connecting element, the electrode can penetrate into the connecting element up to close to the metallic component, whereby a high heat transfer from the electrode and the connecting element to the metallic component can be achieved. After removal of the electrode, a form-fitting connection can be formed in this way between the plastic component, the metallic component and the connecting element inserted between the plastic component and the metallic component.

[0036] According to the invention, the electrode is immersed so deeply into the connecting element, at least 75% of the total height of the connecting element, that the connecting element itself cannot be completely traversed by the current and therefore cannot be completely heated. The intimate connection between the electrode and the connecting element results, on the one hand, in a large contact area between the electrode and the connecting element, and on the other hand, the surface pressure between the electrode and the connecting element results in a high contact force as a process force, whereby both the large contact area and the high contact force exceed both the contact area and the contact force between the connecting element and the metallic component. This allows for a very limited local heat introduction between the connecting element and the metallic component, which results in a high contact resistance. or, in a special embodiment, through which an arc can form between the connecting element and the metallic component. At the same time, due to its high intrinsic thermal conductivity, the electrode can have a particularly advantageous cooling effect on the connecting element and the adjacent plastic component, which should not be damaged by thermal degeneration.

[0037] Depending on the material and dimensions of the metallic component, the plastic component and the connecting element as well as the electrical power of the current flow introduced into the connecting element and the metallic component via the electrode, the heating of the connecting element and the metallic component caused during step e) can lead to the connection of the heated metallic component and the heated connecting element by means of resistance welding or an arc generated between the connecting element and the metallic component can lead to the connection of the metallic component and the connecting element by means of arc welding.The term “arc” refers to the briefly observable ionization of gas particles located in a gap between the connecting element and the metallic component when the electrical potential difference between the electrode and the metallic component is sufficiently high, whereby the electrons formed by the ionization can form a current path between the electrode, the connecting element and the metallic component.

[0038] In the embodiment according to step e), in which an arc is ignited between the connecting element and the metallic component in addition to the contact resistance used for heating, a tip-arc ignition or a drawn arc ignition can be used. With tip-arc ignition, at least one tip of the connecting element is in contact with the metallic component at the start of the current flow. Due to a high current load, the tip can melt or evaporate, whereby the desired arc can form. With drawn arc ignition, the connecting element is first brought into contact with the metallic component to ignite the arc and can be separated from the metallic component by means of an actuator, in particular an electromagnet, after the current has been applied. For this purpose, a capacitor bank with a charging voltage of 20 V to 600 V and a capacity of 10,000 µF to 500 can be used.000 µF are used for the power supply. Additionally, in this design, which uses an arc, the arc can be rotated by an external magnetic field to achieve a more spatially uniform connection between the connecting element and the metallic component.

[0039] In an alternative embodiment, the connection of the metallic component and the connecting element during step e) can be achieved by means of a soldering process, which can include both soldering and brazing. For this purpose, the material of the connecting element can, in particular, at least partially comprise a solder material. In principle, the entire connecting element can even be made of a material whose melting temperature is lower than that of the metallic component and, in this respect, functions as a solder. Alternatively or additionally, the end part of the connecting element can be coated with a solder. For this purpose, the solder can be applied to a connecting element with an enlarged contact area. Suitable solder materials include, in particular, aluminum solders, copper solders, lead solders, tin solders, and / or zinc solders. Other solder materials are conceivable.

[0040] When performing the present method using a brazing process, it is advantageous for maintaining the mechanical strength of the metallic component if it is not melted during the brazing process. Especially with a metal sheet made of high-strength steel, it is particularly advantageous if the present method does not reach or even exceed the austenitizing temperature (AC1 temperature). By selecting a temperature below the AC1 temperature and a short exposure time to this temperature on the metallic component, softening of the high-strength, tempered, or hardened steel or steel sheet can be largely prevented.

[0041] In a special embodiment, the electrode immersed in the connecting element and / or a counter electrode, if present, can be cooled. A closed cooling circuit can be provided, or a bore can be drilled through the electrode to direct cooling fluid directly onto the connecting element and / or the metallic component. This allows very high cooling rates to be achieved, which advantageously prevents damage to the plastic component. Water, compressed air, or ethanol, as well as a mixture thereof, can be used as the cooling medium.

[0042] In a particular embodiment, after step e) has been completed, the connecting surface can be treated, in particular sealed, with an agent selected from a corrosion inhibitor, an adhesive, and an adhesive acting as a corrosion inhibitor. The agent can be applied to the connecting surface by means of an access through the electrode or by means of a separate tool. In particular, the adhesive can be introduced onto and / or around the connecting element by pressing under high pressure in order to fill any openings that may be present in the connecting element to the plastic component and / or to the metallic component. For this purpose, openings or recesses can in particular be provided in the connecting element, which can be designed to create a gap between the connecting element and the plastic component through which the agent can penetrate.

[0043] According to the invention, a method based on known resistance element welding is proposed, in which electrical energy, which can be provided in the form of electrical resistance heating and / or as an arc, is used to join a plastic component and a metallic component using a connecting element. In contrast to known methods, in the method presented here, the connecting element is neither completely axially traversed by the electrical current nor axially contacted by the electrode. As a result, a contact force between the connecting element and the electrode can be set greater than the contact force between the connecting element and the metallic component.This can be achieved according to the invention by means of a hollow connecting element or a connecting element which is recessed in the middle and in particular is conical on the inside, so that the electrode can be immersed in the connecting element and thus, on the one hand, reduce the contact resistance between the connecting element and the electrode and, on the other hand, ensure cooling of the connecting element and the plastic component adjacent to it.

[0044] The proposed method thus differs from known resistance element welding in that the connecting element is designed in such a way that the electrode can be immersed therein, that due to the arrangement of electrode, connecting element and metallic component an arc can be ignited between the connecting element and the metallic component, which is not possible with resistance element welding due to a high shunt, that the current cannot flow completely through the connecting element in the axial direction due to the introduction of the electrode into the connecting element and in that a recess is provided in the plastic component in which the connecting element is located.

[0045] Furthermore, the proposed method differs from the known joining method using threaded bolts, as in addition to the threaded bolt, another element is used to create a positive and / or frictional connection. In contrast, when joining using threaded bolts, the threaded bolt is first welded to the metal component, and only then is another element, particularly a nut or screw with a large head, attached to the threaded bolt to achieve the positive and / or frictional connection between the metal component and the plastic component.

[0046] In a further aspect, the present invention relates to a composite part obtainable using the described method and the associated configurations. The term "composite part" refers to an integrated component comprising the two parts to be joined, wherein the connection in the composite part is mechanically so stable and strong that the two parts can be separated again from the composite part only by locally removing a composite element creating the connection, in particular by drilling or machining. For further details, reference is therefore made to the description of the method.

[0047] In a further aspect, the present invention relates to a use of the composite part as a component or as a component in vehicle, aircraft or ship construction or in the manufacture of electrical devices. Advantages of the invention

[0048] The present method for joining a metallic component and a plastic component as well as composite parts obtainable by this method have a number of advantages.

[0049] This allows different semi-finished products to be joined together in a particularly advantageous manner, whereby the specific properties of the semi-finished products and the materials used can complement each other very well. Examples of this include high ductility and smooth surfaces of the metal component, as well as extensive design freedom and local stiffening structures for the plastic component. In particular, load-bearing plastic components, such as covers, can be joined to a body-in-white. A wide variety of other applications are possible.

[0050] To create the connection using electrical resistance welding or an arc, one-sided access to the intended four-bond surface is sufficient. To reduce the process temperature and thus avoid tempering effects in press-hardened steels, a variant of the present method based on the use of low-melting solders can be used. The proposed method also enables active cooling, in particular through a recess already present in the connecting element. The inventive connection of the metallic component and the plastic component is also conditionally detachable, in particular by drilling out the connecting element used for the connection.According to a variant of the proposed method, pressing of the connecting element, metallic component and plastic component by means of an adhesive, corrosion inhibitor or adhesive acting as a corrosion inhibitor can be used in particular to improve the rigidity, strength and / or corrosion resistance of a composite part obtainable by the present method. Short description of the characters

[0051] Preferred embodiments of the present invention are illustrated in the figures and are explained in more detail in the following description without limiting the scope. Herein: Fig. 1A to 1D are schematic representations of four preferred embodiments of the present method; Fig. 2A to 2C are schematic representations of three preferred embodiments of a connecting element; Fig. 3A to 3D are schematic representations of four preferred positive-locking designs for the connecting element; Fig. 4A to 4F are schematic representations of six preferred embodiments for an end part of the connecting element; Fig. 5A and Fig. 5B schematic representations of two embodiments for preferred cooling; Fig. 6 A and Fig. 6B schematic representations of embodiments for a preferred pressing of an adhesive; and Fig. 7 a schematic representation of another preferred embodiment of the present method. Embodiments of the invention

[0052] In the Fig. 1A to 1D schematically illustrate the present method for joining a metallic component 110 and a plastic component 112. According to step a), the metallic component 110 is preferably provided in the form of a sheet 114 made of steel or aluminum. Alternatively, the metallic component 110 can also be present as a cast part (not shown), which can be produced in particular by die-casting aluminum. The plastic component 112, which preferably comprises a fiber material 116, preferably a short- or long-fiber-reinforced plastic, in particular a carbon-fiber-reinforced plastic, made of a thermoplastic or a thermoset, or a mixture thereof, can be produced in particular by injection molding or lamination.

[0053] According to step b), the plastic component 112 has a recess 118, wherein a metallic connecting element 120 is located in the recess 118. In a particularly preferred embodiment, the connecting element 120 is integrated into the plastic component 112 in a form-fitting and / or force-fitting manner. Preferred embodiments for this can be found in the Fig. 3A to 3D. The connecting element 120 can be inserted into the existing recess 118 of the plastic component 112. Alternatively, the connecting element 120 can also be integrated into the plastic component 112 during the production of the plastic component 112, in particular by inserting the connecting element 120 into a plastic injection mold and connecting the connecting element 120 and the plastic component 112, preferably by positively and optionally by means of a material fit, during the injection molding process.

[0054] The connecting element 120 can be manufactured from steel or aluminum. Preferably, a steel with a low carbon content and a high proportion of chromium, nickel, and / or manganese is used for this purpose, which steel does not exhibit any hardening even at high cooling rates. The connecting element 120 itself can be manufactured, in particular, by means of a forming process or by injection molding and can, in particular, be woven, braided, or penetrated by long fibers. Furthermore, the connecting element 120 can have a coating of an adhesion promoter and / or an electrically and / or thermally insulating material on its outer surface 128 facing the recess 122 in the plastic component 112 in order to enable the best possible connection to the plastic component 112, to prevent contact corrosion with the fiber material 116, and to avoid thermal stress on the plastic component 112.

[0055] The connecting element 120 further has a recess 122 configured to receive an electrode 124, in particular a copper electrode 126, which is introduced into the recess 122 of the connecting element 120 according to step c). In a particularly preferred embodiment, the electrode 124 can be introduced into the recess 122 of the connecting element 120 by pressing the connecting element 120 onto the electrode 124.

[0056] According to step d), the metallic component 110 and the plastic component 112 are pressed together at a provided connecting surface 130 such that no distance or a distance, in particular in the form of a gap 132, can remain between the electrode 124 and the metallic component 110. As shown in the Fig. 1A to 1D, this can be achieved by placing the plastic component 112, which is connected to the connecting element 120 into which the electrode 124 is inserted, onto the metallic component 110. However, other embodiments are also possible, in particular placing the metallic component 110 onto the plastic component 112 or placing the metallic component 110 and the plastic component 112 side by side and, if necessary, clamping them.

[0057] According to step e), the metallic component 110 and the connecting element 120 are subjected to an electric current which, as in Fig. 1A, is designed in the form of an electrical circuit 134 closed by the metallic component 110 and the connecting element 120. In a Fig. In the alternative embodiment shown in Figure 1B, the circuit 134 can be closed by a counter electrode 136, which rests against the metallic component 110. In this way, an indirect connection of the metallic component 110 to the plastic component 112 is achieved by means of the connecting element 120.

[0058] In Fig. 1C shows a further alternative embodiment, which is particularly suitable for use in cases in which the metallic component 110 is provided with a coating, in particular with a lacquer layer, on one or both surfaces (not shown). However, this alternative embodiment can also be used if the metallic component 110 is not coated. In this embodiment according to the invention, the electrode 124, which is introduced into the recess 122 of the connecting element 120, is hollow in order to accommodate a second electrode, for which purpose the counter electrode 136 serves here, which in this alternative embodiment can come into direct contact with the metallic component 110, in particular with the coated metallic component 110. In this way, direct contact with the metallic component 110 can be made within the connecting element 120.The connection surface 130 can be removed after removing the electrodes 124, 136 as shown below. Fig. 6B schematically shown, sealed. In order to absorb the process forces generated by pressing the metallic component 110 and the plastic component 112 together, a counterholder 137 can preferably be used, which, however, cannot be configured to act simultaneously as an electrode or counterelectrode. However, in order to prevent the counterholder 137 from leaving an impression in the metallic component 110 due to the process forces, the counterholder 137 can be rounded, in particular at the edge, adapted to the component geometry of the metallic component 110 and / or at least partially comprise a material that is softer than the metallic component 110, preferably a plastic, in particular Teflon.

[0059] Fig. 1D describes a further alternative embodiment, which is also particularly suitable in cases in which the metallic component 110 is provided with a coating, in particular with a lacquer layer, on one or both surfaces (not shown). However, this alternative embodiment can also be used if the metallic component 110 is not coated. In this alternative embodiment, the connection of the metallic component 110 and the plastic component 112 can be effected in particular in such a way that the Fig. 1D can be inserted simultaneously or sequentially into the two recesses 118, 118'. If the connecting elements 120, 120' are used sequentially, the connecting element 120 inserted first can enable particularly good contact between the metallic component 110 and the electrode 124. If the two connecting elements 120, 120' are used simultaneously, an alternating electrical current can preferably be used to establish the connection according to the invention, in particular in order to achieve the most uniform possible connection between the metallic component 110 and the plastic component 112. In a special embodiment, the two electrodes 124, 136 can be mechanically firmly connected to one another and can therefore act on the metallic component 110 in the form of a common movement (not shown).Alternatively, the two electrodes 124, 136 can be movable independently of each other and can be connected to each other, preferably via at least one spring.

[0060] For a current flow through the circuit 134, it follows that in particular a low contact resistance can arise between the electrode 124 and the connecting element 120, which is preferably in positive contact therewith, as well as a high contact resistance between the electrode 124 and the metallic component 110. As shown in the Fig. 1A to 1D, the electrode 124 can preferably penetrate into the connecting element 120 in such a way that it can be positioned close to the metallic component 110, which can result in a high heat transfer from the electrode 124 and the connecting element 120 to the metallic component 110.

[0061] As continued in the Fig. As shown in Figures 1A to 1D, the electrode 124 is immersed in the connecting element 120 in such a way that the connecting element 120 itself cannot be completely heated by the current. The close connection between the electrode 124 and the connecting element 124 can, on the one hand, result in a large contact area between the electrode 124 and the connecting element 120, and on the other hand, the surface pressure between the electrode 124 and the connecting element 120 can result in a high contact force, which can exceed both the contact area and the contact force between the connecting element 120 and the metallic component 110. This allows for a very limited local heat input between the connecting element 120 and the metallic component 110.

[0062] Depending on the material and dimensions of the metallic component 110, the plastic component 112, and the connecting element 120, as well as the electrical power of the current flow in the circuit 134, heating the connecting element 120 and the metallic component 110 can lead to a connection of the heated metallic component 110 and the heated connecting element 120 by means of resistance welding. Alternatively or additionally, an arc (not shown) can be generated in the gap 132 between the electrode 124 and the metallic component 110, which can also lead to the connection of the components adjacent to the arc, metallic component 110 and connecting element 120, by means of arc welding. To ignite the arc, a tip-arc ignition or a drawn arc ignition, in which the connecting element 120 is pulled away from the metallic component 110 during the current flow, can be used.If the arc is additionally set in rotation by an external magnetic field, a more spatially uniform connection of the metallic component 110 and the connecting element 120 can be achieved.

[0063] Due to its high thermal conductivity, the electrode 124 can simultaneously have a cooling effect on the connecting element 120 and the adjacent plastic component 112, the damage to which due to thermal degeneration is to be avoided.

[0064] After removing the electrode 124, a positive connection can be created between the plastic component 112, the metallic component 110 and the connecting element 120 located between the plastic component 112 and the metallic component 110. As shown in the Fig. 1A to 1D, a connection of the metallic component 110 and the plastic component 112 can thus be achieved by means of the connecting element 120.

[0065] The Fig. 2A to 2C show various embodiments of the connecting element 120. While the Fig. 2A schematically illustrated connecting element 120 has a cylindrical design 138, the Fig. 2B and Fig. 2C, the connecting elements 120 each have a conical design 140. In addition, the connecting elements 120 each have an end part 142 facing the connecting surface 130 in various embodiments. While the Fig. 2A has a flat, open bottom 144, the end part 142 in the embodiment of the connecting element 120 according to Fig. 2B has an open, beveled bottom 146, which is particularly designed to achieve the highest possible concentration of the current. The end part 142 in the embodiment according to Fig. 2C shows a flat, closed bottom 148, which closes off the connecting element 120 at the bottom. The design according to Fig. 2C is particularly suitable for a soldering process according to Fig. 7. The embodiments according to the Fig. 2A to 2C have the overall advantage that the end part 142 each has a larger surface area, so that a significant part of the heat generation in the connecting element 120 cannot occur directly adjacent to the plastic component 112 in order to further reduce the thermal load on the plastic component 112.

[0066] As mentioned above, it is particularly advantageous for carrying out the present method if the connecting element 120 is integrated into the plastic component 112 in a form-fitting and / or force-fitting manner. Fig. 3A to 3D show corresponding form-fitting embodiments of the connecting element 120, in which the connecting element 120 and the plastic component 112 are designed such that they engage with each other in such a way that they cannot be separated from each other without force transmission. This is done in the Fig. 3A and Fig. 3B by way of example of projections 150 of the connecting element 120 penetrating into the plastic component 112, which can be received in particular by correspondingly designed grooves 152. In contrast, the projections 150 shown in the Fig. 3C and Fig. The connecting elements 120 schematically illustrated in Figure 3D each have a differently configured positive connection 154, 154' on a head portion 156 of the respective connecting element 120, facing away from the connecting surface 130. For this purpose, the plastic component 112 can be thickened in the region of the connecting surface in order to achieve the best possible force introduction.

[0067] The Fig. 4A to 4F show various embodiments of the end part 142 of the connecting element 120. As already particularly apparent from the Fig. 2A to 2C, the end part 142 of the connecting element 120 can be closed or open. This difference is also found in the Fig. 4A to 4F, wherein the end part 142 in the Fig. 4A and Fig. 4B is closed, while in the Fig. 4C to 4F each show an open version.

[0068] The Fig. 4A to 4F each show an advantageous embodiment for the end part 142 of the connecting element 120. Accordingly, the end part 142 can preferably have a contact surface 158, which can be aligned with respect to the metallic component 110. In particular, to increase the concentration of the electrical current and thus to increase the localization of heat input from the electrode 124 into the metallic component 110, the contact surface 158 can be designed such that the size of the contact surface 158 can be reduced. A reduction in the size of the contact surface 158 takes place in Fig. 4A by means of paragraph 160, in Fig. 4B by means of a pin 162 for arc ignition, in Fig. 4C by means of a phase 164 and in the Fig. 4D to 4F each by means of a bevelled end part 166. However, further designs of the end part 142 of the connecting element 120, which can reduce the size of the contact surface 158, are conceivable.

[0069] The Fig. 5A and Fig. 5B show further, special embodiments of the present method, in which the electrode 124 immersed in the connecting element 120 and a counter electrode 136, which is also present here, are cooled. As in Fig. 5A, a bore 168, 168' can be provided through the electrode 124 and the counter electrode 136, respectively, which are designed to direct a cooling fluid as directly as possible onto the connecting element 120 and / or the metallic component 110. In this case, the cooling fluid can also flow through a gap 167 between the electrode 124, which is in contact with the connecting element 120, and the counter electrode 136. In the inventive embodiment according to Fig. 5B, in which the electrode 124, which is inserted into the recess 122 of the connecting element 120, is hollow to accommodate the counter electrode 136, the bore 168 provided for receiving the cooling fluid can only be introduced into the counter electrode 136. In a particularly preferred embodiment, the gap 167 between the electrode 124 and the counter electrode 136 can be sealed at the tips of the electrode 124 and the counter electrode 136 by an elastic sealing element 169, which can be designed in particular in the form of an O-ring or a silicone joint, in order to thereby enable a repositioning movement and / or a relative movement of the counter electrode 136 with respect to the electrode 124 and / or the connecting element 120. This allows cooling of the counter electrode 136, the electrode 124 and / or the connecting element 120 without the cooling fluid escaping.Regardless of the actual design, very high cooling rates can be achieved, which can prevent damage to the plastic component 112. Water, compressed air, or ethanol, as well as a mixture thereof, are particularly suitable as cooling media. In an alternative embodiment (not shown), a closed cooling circuit can also be provided.

[0070] The bore 168 through the electrode 124 can be used alternatively or additionally to provide and press in an agent 170 selected from a corrosion inhibitor, an adhesive, and an adhesive acting as a corrosion inhibitor.

[0071] As in the Fig. 6A and Fig. 6B, the connecting surface 130 can be treated, in particular sealed, after step e) has been completed, using an agent 170, which is selected from a corrosion inhibitor, an adhesive, and an adhesive acting as a corrosion inhibitor. The agent 170 can, in particular, be a curable substance, which can solidify after application to the intended locations. The agent 170 can, on the one hand, be applied via the Fig. 5 through the bore 168 shown in FIG. 5 through the electrode 124 or alternatively through a separate tool, which may in particular take the form of a nozzle 172, onto the connecting surface 130. The agent 170 can be introduced, in particular, by pressing under high pressure on and / or around the connecting element 120 in order to fill any recesses or openings 174 that may be present in the connecting element 120 to the plastic component 112 and / or to the metallic component 110. Furthermore, openings or recesses can be separately provided in the connecting element 120, which can be configured to create a gap 176 between the connecting element 120 and the plastic component 112, through which the agent 170 can penetrate.

[0072] Fig.7 schematically shows a further preferred embodiment of the present method, in which the connection of the metallic component and the connecting element 120 during step e) can be effected by means of a soldering process, which can include both soldering and brazing. For this purpose, the connecting element 120 can at least partially comprise a solder material 178. In principle, even the entire connecting element 120 can consist of the solder material 178. Alternatively or additionally, only the end portion 142 of the connecting element 120 can be coated with the solder material 178. Aluminum solder, copper solder, lead solder, tin solder, and / or zinc solder are particularly suitable as the solder material 178. However, other solder materials 178 and designs are conceivable. List of reference symbols 110 metallic component 112 plastic component 114 sheet metal 116 Fiber material 118, 118' recess 120, 120' (metallic) connecting element 122 Deepening 124 Electrode 126 copper electrode 128 outer surface 130, 130' connecting area 132 gap 134 (electrical) circuit 136 Counter electrode 137 Counterholder 138 cylindrical version 140 conical version 142 end part 144 flat, open floor 146 open, sloping floor 148 flat, closed bottom 150 lead 152 groove 154, 154' form closure 156 headboard 158 contact area 160 paragraph 162 Arc ignition pin 164 Phase 166 bevelled end piece 167 gap 168, 168' bore 169 elastic sealing element 170 Agents (corrosion inhibitors and / or adhesives) 172 nozzle 174 Opening 176 gap 178 Solder material (solder)

Claims

[1] Method for joining a metallic component (110) and a plastic component (112), comprising the steps: a) providing a metallic component (110); b) providing a plastic component (112) having at least one recess (118), wherein a metallic connecting element (120) having a recess (122) for receiving an electrode (124) is located in the recess (118); c) inserting the electrode (124) into the recess (122) of the connecting element (120) such that the electrode (124) and the connecting element (120) come into contact; d) pressing the metallic component (110) and the connecting element (120) together; and e) applying an electric current to the metallic component (110) and the connecting element (120) such that the metallic component (110) and the plastic component (112) are connected at a connecting surface (130) by means of the connecting element (120), wherein the recess (122) of the metallic connecting element (120) designed to receive the electrode (124) is conical and an end part (142) of the connecting element (120) facing the connecting surface (130) has an open bottom (144, 146), wherein the introduction of the electrode (124) into the recess (122) of the connecting element (120) according to step c) is such that the electrode (124) penetrates into the recess (122) to at least 75% of the total height of the connecting element (120), characterized by that the electrode (124) is hollow in order to accommodate the counter electrode (136) separated by a gap (167). [2] Method according to the preceding claim, wherein a counter electrode (136) connected to the metallic component (110) is plate-shaped or the metallic component (110) itself serves as the counter electrode (136). [3] Method according to one of the preceding claims, wherein the metallic component (110) is mounted on a counterholder (137). [4] Method according to one of the preceding claims, wherein the connecting element (120) is introduced into the recess (118) of the plastic component (112) or wherein the connecting element (120) is integrated into the plastic component (112) during manufacture of the plastic component (112). [5] Method according to one of the preceding claims, wherein the introduction of the electrode (124) into the recess (122) of the connecting element (120) is carried out by pressing the connecting element (120) onto the electrode (124). [6] Method according to one of the preceding claims, wherein the connecting element (120) has a through-hole and has a wall thickness in a conical central part which is less than the overall dimensions of the connecting element (120) and / or less than 2.0 mm, preferably less than 1.0 mm. [7] Method according to one of the preceding claims, wherein during step e) at least a local heating of the connecting element (120) and the metallic component (110) is brought about and the connection of the heated metallic component (110) and the heated connecting element (120) is effected by means of resistance welding. [8] Method according to one of the preceding claims, wherein an arc is generated in the distance configured as a gap (132) between the connecting element (120) and the metallic component (110) during step e) and the connection of the metallic component (110) and the connecting element (120) is effected by means of arc welding. [9] Method according to one of the preceding claims, wherein the connecting element (120) at least partially comprises a solder material (178) and / or is coated with a solder material (178) on a side facing the connecting surface (130), wherein the connection of the metallic component (110) and the connecting element (120) during step e) is effected by means of a soldering process. [10] Method according to one of the preceding claims, wherein the connecting surface (130) is cooled at least during step e). [11] Method according to one of the preceding claims, wherein the connecting surface (130) is treated after step e) with an agent (170) selected from a corrosion inhibitor, an adhesive and an adhesive acting as a corrosion inhibitor. [12] Method according to one of the preceding claims, wherein the plastic component (112) is selected from a thermoplastic and / or a thermosetting plastic and / or from a fiber-reinforced plastic component and / or wherein the connecting element is selected from an element comprising steel or aluminum. [13] Method according to one of the preceding claims, wherein the metallic component (110) is provided on at least one side with a coating, in particular with at least one lacquer layer or a corrosion protection layer. [14] Method according to one of the preceding claims, wherein the plastic component (112) has at least two recesses (118, 118'), wherein the at least two metallic connecting elements (120, 120') are introduced into the recesses (118, 118') simultaneously or successively.

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