Joining elements and methods for joining two workpieces

Abstract

Identify joining elements that ensure a more secure bond between two workpieces. [Solution] A joining element and a corresponding method for joining two workpieces are provided. The joining element comprises a head and a cylindrical shaft extending from the bottom of the head. The shaft includes a base extending from the bottom of the head. The shaft includes a tip that forms the end of the shaft opposite to the head. The shaft further includes a rib section between the base and the tip. The rib section has a plurality of ribs.

Description

Technical Field

[0001] The present invention relates to a joining element for joining at least two workpieces, in particular for drilling and joining, a corresponding method, and the use of the joining element in a drilling and joining method, in particular a flow drill fastening method or a flow drill screw tightening method.

Background Art

[0002] Joining elements for joining workpieces, elements, and components to one another are known and in use. In the case of a thread-forming joining element, prior to joining, the material of the workpiece is shaped or deformed such that threads are formed in the workpiece, rather than material being removed from the workpiece to form threads for the joining element. However, when the thread-forming joining element is inserted, a small amount of material is removed from the workpiece. Some thread-forming joining elements are also capable of forming a hole in the workpiece where the joining element is arranged. This hole can be formed simultaneously with the threads. A thread-forming joining element that is also capable of forming a hole is also referred to as a thread-forming / drilling joining element or a drilling joining element.

[0003] To insert the drilling joining element into the workpiece, the first workpiece and indirectly the second workpiece are heated by rotating the fastening element in contact with the first workpiece. Thereafter, the joining element is inserted into the first workpiece, pushed through the first workpiece, and inserted into the second workpiece. The screw-shaped joining element is kept rotating throughout the joining operation. As a result, threads are formed on the workpieces.

[0004] The joining element and the workpieces to be joined can be adapted to each other such that the surface of the second workpiece is not penetrated by the joining element. In the region of the joining element, a protrusion is formed on the non-penetrated surface.

[0005] International Publication No. 2023 / 214164 discloses a thread-forming / perforated joint element. This joint element includes a head and a shaft defining a longitudinal axis. The shaft has a shaft portion and a tip portion. The shaft portion extends from the head. The tip portion extends from the shaft portion and is located opposite the head. Threads are formed on at least a portion of the shaft portion.

[0006] It has been observed that when threaded joint elements are inserted, the starting end of the threaded portion of the joint element can act like a knife, potentially generating long, thread-like material chips. These chips can wrap around the head of the joint element, potentially preventing its complete insertion.

[0007] In the case of machine tools, it is known that a so-called chip breaker is installed to bend and crush the chips in order to make them smaller.

[0008] However, the chips that can be generated during drilling and joining methods, particularly flow drill screw tightening methods, are highly ductile because they are produced in a hot process, making it difficult to break or divide them into relatively small pieces.

[0009] German Patent Application Publication No. 102010046318 relates to a joining element that does not have threads but deforms itself during the joining process to form a secure joint between two overlapping joining parts.

[0010] Korean Patent Application Publication No. 1020040090612 relates to a riveting method that locally melts a material. This riveting method is implemented as a double-sided joining method.

[0011] International Publication No. 02 / 062518 relates to fastening elements that deform together with the workpiece, using materials of similar hardness. [Overview of the Initiative]

[0012] Therefore, there is a need for joining elements that at least partially mitigate the aforementioned problems from prior art. Furthermore, the objective is to identify joining elements that, when used, can avoid long material chips during flow drill fastening. Additionally, the objective is to identify joining elements that ensure a more secure joint between two workpieces. There is also a need for methods corresponding to these joining elements.

[0013] At least one of the above technical challenges is achieved by a joining element or joining method according to an independent claim. Further embodiments are specified in the dependent claims.

[0014] In an independent aspect of the present invention, a joining element for joining two workpieces is provided. The joining element comprises a head and a cylindrical shaft extending from the base of the head. The shaft includes a base extending from the base of the head. The shaft includes a tip that forms the end of the shaft opposite to the head. The shaft further includes a rib portion between the base and the tip. The rib portion has a plurality of ribs.

[0015] In a further independent aspect of the present invention, a joining element is provided for drilling and joining two workpieces. The joining element comprises a head and a cylindrical shaft extending from the base of the head. The shaft includes a base extending from the base of the head. The shaft includes a tip that forms the end of the shaft opposite to the head. The shaft further includes a rib section between the base and the tip. The rib section comprises a plurality of ribs that surround the shaft in their respective planes and have certain rib projections. These planes are parallel to each other. The rib section covers more than 30% of the shaft.

[0016] In a further independent aspect of the present invention, a method for drilling and joining two workpieces is provided. The method includes the steps of: providing a first workpiece, a second workpiece, and a joining element according to one aspect of the present disclosure; positioning the joining element on the surface of the first workpiece; rotating the joining element at a predetermined rotational speed; and applying a predetermined axial force to the joining element in the direction of the surface of the first workpiece.

[0017] In a further independent aspect of the present invention, the use of a joint element according to any one aspect of the present disclosure in a flow drill fastening method is provided.

[0018] The core of this invention is that, instead of the usual threads, at least a substantial portion of the shaft, e.g., 30% or more, is covered by multiple parallel ribs of the rib section. As a result, the joint element loses at least partially its thread properties. In contrast to the grooves of threads, the grooves between each pair of adjacent ribs or rib projections are limited to the circumferential length of the shaft. Therefore, in drilling joint methods, shorter chips are essentially generated than in threads. Even with at least partial replacement of the threads, this joint element can still be used in one-sided joint methods such as flow-drill fastening methods. Neither the multiple ribs nor the grooves formed between them have a helical shape. As a result, a chip surface, as in threads, can be avoided. Experiments have shown that the functionality of the joint element is maintained compared to threaded joint elements, for example, those described in International Publication No. 2023 / 214164. The deformed material of the two workpieces can flow into the grooves between each pair of adjacent ribs. Furthermore, it was found that the multiple ribs create an engagement interface at the joint of the two workpieces that is comparable to a screw thread, and also reduce the risk of incomplete insertion of the joining element and prevent loosening due to vibration. In other words, by replacing the screw thread of the joining element with ribs, it is possible to prevent the screw thread from acting as a cutting device and generating long, thread-like material residue, and to prevent the joining element from coming loose or being manipulated due to vibration. The non-helical grooves between the multiple ribs prevent the formed material threads from being pulled out and, for example, wrapping around the head of the joining element.

[0019] A joining element and / or method, or use of a joining element, may further have one or more of the following features:

[0020] Each rib in the rib section can surround the shaft in its respective plane.

[0021] At least one of the ribs may be substantially perpendicular to the shaft axis.

[0022] Each rib in the rib section may have a certain rib projection and / or a certain rib diameter.

[0023] The ribs may be formed parallel to each other. The planes on which the ribs surround the shaft may also be parallel to each other.

[0024] The rib portion can cover 30% or more of the shaft, preferably 50% of the shaft.

[0025] The rib portion may completely cover the shaft between the base and the tip. The rib portion may completely cover the region between the base and the tip. The shaft may have a complete groove between the base and the tip, i.e., it may not have a smooth portion. The rib portion may cover 40% or more, preferably 50% or more, and more preferably 60% or more of the shaft between the base and the tip. All ribs of the rib portion may surround the shaft in their respective planes, in particular completely, and each may have a certain rib projection or the same rib diameter. The rib diameter may correspond to or be the same as the outer diameter of the shaft.

[0026] The two workpieces may each be flat workpieces that can directly contact each other via a planar contact surface. The joining element is preferably introduced or inserted into the area of ​​the planar contact surface within the two workpieces which are arranged overlapping each other.

[0027] The shaft can be formed from a material that is harder than the material of the two workpieces, preferably 50% or more harder. The term "hardness" means the mechanical resistance of a material or workpiece to mechanical penetration by another object, for example a joining element. This difference in hardness between the shaft and the workpieces to be joined allows more appropriate control of material displacement in the workpieces, and can increase the joining strength of the two workpieces.

[0028] The base portion, in the region adjacent to the rib portion, may have a diameter that corresponds to or is identical to the diameter of the rib or the rib portion. The tip portion may have a maximum diameter in the region adjacent to the rib portion. The maximum diameter of the tip portion may be smaller than the diameter of the rib or the rib portion. In other words, the outer shell of the shaft may be tapered at the transition from the rib portion to the tip portion. Thereby, the material displacement in the first workpiece and / or the second workpiece can be improved.

[0029] A constant rib protrusion may mean that the ribs have the same height relative to the shaft in the circumferential direction of the shaft. Each rib may have a circular cross section. Each rib may be rotationally symmetric about the rotational axis of the joining element. The shaft may have a circular cross section and / or may be rotationally symmetric about the rotational axis of the joining element.

[0030] The joining element can be inserted into the two workpieces on one side, that is, without the support of a second component located on the side opposite the joining element relative to the two workpieces.

[0031] The joint element may further have a threaded portion positioned between the rib portion and the base portion. The threaded portion may have threads, particularly male threads. The threaded portion may be formed on the shaft axially towards the head portion than the rib portion. The rib portion may be directly adjacent to the tip portion. This allows for equally effective avoidance of long material chips, while the threaded portion can create an additional clamping effect in the region closer to the head of the joint element. Advantageously, the width of the threaded portion is selected to be particularly equal to the thickness of the first workpiece. This allows the threaded portion to more effectively secure the first workpiece to the second workpiece in the formed joint.

[0032] The ribs may have a symmetrical rib cross-sectional shape. Each rib may have a symmetrical rib cross-sectional shape. The term “rib cross-sectional shape” refers to a longitudinal cross-section passing through one or more rib projections that abut each other. Each rib or each rib projection may have a first side and a second side. A symmetrical rib cross-sectional shape may mean that the first side is mirror-symmetric with respect to the second side in the longitudinal cross-section. The plane on which each rib is formed may function as a mirror. The mirror may be perpendicular to the axis of rotation of the joint element or intersect the axis of rotation at an angle other than 90°.

[0033] The axis of rotation of the joint element may be coaxial with the longitudinal axis of the shaft.

[0034] The ribs may have an asymmetric rib cross-sectional shape. Each rib may have an asymmetric rib cross-sectional shape. The first side of the rib projection may face the head. The second side of the rib projection may face the tip. The first side may intersect a plane that intersects both sides and is parallel to the rib at a first angle. The first angle may be smaller or larger than the second angle at which the second side intersects the plane. In other words, the ribs may have a sawtooth shape in the longitudinal cross-section. The asymmetric rib cross-sectional shape can improve material flow or material displacement between two workpieces and increase pull-out resistance or tear resistance.

[0035] The rib section, individual ribs, and / or each rib may have a trapezoidal shape in its longitudinal cross-section. Alternatively or in addition to this, the rib section, individual ribs, and / or each rib may have a rounded shape, a sawtooth shape, and / or a triangular shape in its longitudinal cross-section.

[0036] A circumferential groove may be formed between each pair of ribs. Each groove may have a constant groove depth. The groove depth may vary along the axial direction of the shaft, and may increase particularly towards the tip. This may mean that closer to the tip, the groove between two ribs may be deeper than the groove between two adjacent ribs. The outer diameter of the ribs may be the same for all ribs. The diameter of the shaft may vary along the axial direction, and may be conical or tapered in particular. This may result in different groove depths for different axial positions of the groove.

[0037] The rib projection or rib may have a first rounded shape in its longitudinal cross-section, and / or the groove may have a second rounded shape in its longitudinal cross-section between the ribs. The second rounded shape may have a curvature opposite to that of the first rounded shape. The first and second rounded shapes may have the same curvature in magnitude. In other words, the ribs and / or grooves may be rounded or curved.

[0038] A groove having a first groove width can be formed between each pair of ribs. At least one of the grooves may have a second groove width greater than the first groove width. One of the grooves having the second groove width preferably connects its tip to the rib section. In other words, the grooves in the rib section may be a mixture of large and small grooves. To reduce the penetration resistance of the joining element to the two workpieces, it may be advantageous for the tip and the rib section to be connected by a larger groove, i.e., a wider and / or deeper groove, compared to the other grooves.

[0039] The axis of rotation of the joint element may intersect the plane of the rib perpendicularly or at an angle other than 90°. This means that the ribs in the rib section may be arranged horizontally or obliquely, but not in a mixed arrangement of horizontal and oblique. Obliquely arranged ribs differ from a screw thread in that, unlike a screw thread which has only a single groove, multiple ribs are arranged with separate grooves between them.

[0040] The tip does not need to have grooves, threads, or ribs.

[0041] The head may further have an undercut. The undercut may be adjacent to the shaft and may extend particularly around the shaft. The undercut may be configured to receive material from the first workpiece and / or the second workpiece when the joint element is used.

[0042] The head may further have a hexagonal section, which is a means by which the joining tool can transmit torque to the joining elements.

[0043] The tip may have a conical shape to form the largest possible contact surface with the first workpiece when positioned on the surface of the first workpiece. Friction between the joining element and the first workpiece is caused by the rotation of the joining element and by applying an axial force to the joining element. The joining element penetrates into the first workpiece depending on the axial force and the material properties of the first workpiece. When the joining element penetrates deeply enough into the first workpiece, or into the first and second workpieces, that the groove of the groove portion contacts the first workpiece, a groove cross-sectional shape corresponding to the groove of the groove portion is formed in the first and / or second workpieces as the joining element penetrates further.

[0044] The rotation of the joining element heats the first workpiece, and through it, the second workpiece. In this case, the rotation is configured to heat the first workpiece and / or the second workpiece only to a processing temperature of approximately 300°C. The first workpiece and / or the second workpiece may be made of aluminum having a melting temperature of 660°C. This ensures that the processing temperature is maintained below the melting temperature of the first workpiece and / or the second workpiece, i.e., that melting of the first or second workpiece does not occur. As a result, the material of the first workpiece and / or the second workpiece is maintained near or below its recrystallization temperature in the hot-forming region, thus avoiding problems associated with hot-forming, such as grain growth and loss of local mechanical properties, while improving ductility compared to cold-forming.

[0045] Preferably, before or when the joining element is placed on the surface of the first workpiece, the first and / or second workpieces do not have holes in the region of the first or second workpiece that is aligned axially with the axis of rotation of the joining element. That is, the joining element can be introduced into the first and second workpieces without drilling pilot holes in the first and / or second workpieces.

[0046] When the first and second workpieces are joined together, the tip may be surrounded by the first and / or second workpieces. In particular, when the joining element penetrates the first and second workpieces to their final depth, the tip may be surrounded by the first and / or second workpieces. When the first and second workpieces are joined together, or when the joining element penetrates the first and second workpieces to their final depth, the tip does not have to protrude from the first and / or second workpieces. The tip may be at least partially surrounded by a protrusion formed on the second workpiece. When the first and second workpieces are joined together, or when the joining element penetrates the first and second workpieces to their final depth, the surface of the second workpiece does not have to be penetrated by the joining element.

[0047] The first workpiece and / or the second workpiece may be a component. In particular, the first workpiece and / or the second workpiece may contain metal or be composed of metal. Preferably, the first workpiece is a metal element or metal component, in particular a steel element or steel component. Similarly, the first workpiece may be an aluminum component. The aluminum component may be composed of or contain AA5000, AA6000, or AA7000 alloys. The second workpiece may be a metal element or metal component, in particular an aluminum element or aluminum component. Particularly preferably, the second workpiece is an aluminum cast element. The second workpiece may be an unheat-treated aluminum cast element. Similarly, the second workpiece may be an aluminum cast element with a high proportion of secondary aluminum, i.e., a high proportion of recycled aluminum. The second workpiece may be composed of or contain AA7000 alloy.

[0048] The present invention, or further embodiments and advantages thereof, will be described in more detail below with reference to the drawings, which merely illustrate exemplary embodiments of the present invention. Identical components are denoted by the same reference numerals in the drawings. Elements drawn with dashed lines are considered optional elements. [Brief explanation of the drawing]

[0049] [Figure 1] This is a perspective side view of a first example of a joint element according to an embodiment of the present disclosure. [Figure 2a] Figure 1 is a longitudinal cross-sectional view of the joint element. [Figure 2b] This shows an enlarged region of the longitudinal cross-section of Figure 2a. [Figure 3a] This is a longitudinal cross-sectional view of a second example of a joint element according to an embodiment of the present disclosure. [Figure 3b] This shows an enlarged region of the longitudinal cross-section of Figure 3a. [Figure 4] This is a longitudinal cross-sectional view of a third example of a joint element according to an embodiment of the present disclosure. [Figure 5]This is a longitudinal cross-sectional view of a fourth example of a joint element according to an embodiment of the present disclosure. [Figure 6] This is a longitudinal cross-sectional view of a fifth example of a joint element according to the embodiments of the present disclosure. [Figure 7] This is a longitudinal cross-sectional view of a sixth example of a joint element according to the embodiments of the present disclosure. [Figure 8a] This is a perspective side view of a seventh example of a joint element according to an embodiment of the present disclosure. [Figure 8b] Figure 8a is a longitudinal cross-sectional view of the joint element. [Figure 9a] This is a perspective side view of an eighth example of a joint element according to an embodiment of the present disclosure. [Figure 9b] Figure 9a is a longitudinal cross-sectional view of the joint element. [Figure 10] This is a longitudinal cross-sectional view of a used joint element in the method according to the embodiments of this disclosure. [Modes for carrying out the invention]

[0050] In the following, unless otherwise noted, the same reference numerals are used for elements that are identical and have the same effect. The illustrated elements should not be assumed to be to scale; rather, individual elements may be illustrated in an exaggerated size for the sake of understanding.

[0051] Figure 1 shows a first example of a joint element 100 according to an embodiment of the present disclosure. The joint element 100 has a head 10 and a shaft 20. The shaft 20 extends from the head 10, more precisely from the bottom of the head 10. The head may have a hexagonal portion 12 for connecting the joint element 100 to a joining tool.

[0052] In the example shown in Figure 1, the shaft 20 can be divided into three regions. The base 21 is formed directly adjacent to the bottom of the head 10 and extends from there. The base 21 is preferably formed rotationally symmetric with respect to the axis of rotation RA.

[0053] Adjacent to the base 21, the rib section 22 continues axially Z. The rib section 22 has a plurality of ribs 1, and a groove 2 may be formed between two directly adjacent ribs 1. In the example of Figure 1, the ribs 1, more precisely each rib 1, have a trapezoidal shape. In the trapezoidal shape, the smaller base can be significantly smaller than the larger base. The rib 1 has a rib projection 1h, which may also be called the rib height. The rib projection 1h or rib height corresponds to the groove depth. The groove 2 further has a groove width 2w, which may be defined between the two ends of the rib 1 that form the groove 2. In the example of Figure 1, all ribs 1 are formed in the same way. The ribs 1 are each formed parallel to each other and perpendicular to the axis of rotation RA. Each rib 1, and thus the rib section 22 itself, has a diameter 1d, which can be larger than the (internal) diameter 2d of the shaft 20, which corresponds to the diameter of the groove 2. Thus, reference numeral 1d means the rib diameter, and reference numeral 2d means the groove diameter. The groove 2, rib 1, and rib portion 22 can be formed rotationally symmetric with respect to the rotation axis RA.

[0054] The base can have a diameter corresponding to the diameter 1d of the rib 1.

[0055] Figure 2a shows an example of the joint element 100 in Figure 1 in a longitudinal section.

[0056] To clearly show the parallel planes on which each rib 1 is formed, dashed lines passing through rib 1 are drawn in Figure 2a.

[0057] In the longitudinal section of Figure 2a, the undercut 11 of the head 10 is further shown compared to Figure 1, and the base 21 extends from this undercut.

[0058] Figure 2b shows detail A of the shaft 20. Here, the ribs 1 and the grooves 2 formed between the ribs 1 are highlighted in the longitudinal section view. In the examples of Figures 1, 2a, and 2b, each rib 1 may have the same rib projection 1h. In the enlarged view of Figure 2b, it can be clearly seen that the maximum diameter of the tip 23 directly adjacent to the rib portion 22 is smaller than the diameter 1d of the rib 1 and larger than the diameter 2d of the groove 2. Therefore, the tip 23 can be tapered relative to the rib portion 22.

[0059] Figures 3a and 3b show a second example of the joint element 100. Similar to Figure 2b, Figure 3b shows a magnified view of detail A in Figure 3a.

[0060] The joint element 100 in the examples of Figures 3a and 3b may have rounded ribs 1 and grooves 2 compared to the joint element 100 in the examples of Figures 1, 2a, and 2b. This means that the rib portion 22 has a rounded shape in its longitudinal cross-section. The curvature of the rounded shape of the rib 1 may be substantially opposite to the curvature of the rounded shape of the groove 2. The remaining properties and features of the joint element in Figures 3a and 3b apply in the same way as those described with respect to Figures 1, 2a, and 2b.

[0061] In the enlarged view of Figure 3b, the rounded shape of the rib portion 22 can be seen compared to the trapezoidal shape in Figure 2b.

[0062] Figure 4 shows a third example of the joint element 100. In the example of Figure 4, the rib projection 1h can vary along the axial Z compared to the examples of Figures 1, 2a, and 2b. That is, in this configuration, the grooves 2, 2' may have different groove diameters 2d, 2d' and / or different groove widths 2w, 2w'. Grooves 2, 2' having different groove diameters 2d, 2d' and / or different groove widths 2w, 2w' can be mixed in the rib portion 22.

[0063] A first groove 2 and a second groove 2' can be formed between each of the two ribs 1. The first groove 2 may have a first groove width 2w, and the second groove 2' may have a second groove width 2w'. Preferably, the tip portion 23 and the rib portion 22 are connected by the second groove 2'. In other words, the last groove 2 in the axial direction Z is preferably the second groove 2'. Furthermore, it is advantageous to form two, three, or four second grooves 2', particularly in the half of the rib portion 22 that is closer to the tip portion 23 than to the base portion 21.

[0064] Figure 5 shows a fourth example of the joint element 100. In the example of Figure 5, each groove 2 has a different groove diameter 2d, but the rib diameter 1d may be the same for all ribs. In particular, the groove diameter 2d may decrease or taper continuously in the axial Z direction with respect to a continuous groove 2. The (inner) diameter of the shaft 20 may have a conical shape. The rib projection 1h of the rib 1 may increase in the axial Z direction with respect to a continuous rib 1, especially continuously. This allows the groove 2 located closer to the tip 23 and penetrating deeper into the two workpieces to accept more deformed material from the workpieces than the groove 2 located closer to the base 21. Thus, the penetration resistance of the joint element 100 into the two workpieces can be reduced.

[0065] Figure 6 shows a fifth example of the joint element 100. In the example of Figure 6, the rib portion 22, the rib 1, and / or each of the ribs 1 may have an asymmetric rib cross-sectional shape, particularly a sawtooth shape. As shown in detail in the circular enlargement, the first side of the rib 1 faces the base 21 or the head 10, and the second side faces the tip 23. Furthermore, the plane in which the rib projection 1h has its maximum extent is shown by a dashed line. In the longitudinal cross-section of Figure 6, the first side, the second side, and the plane intersect. In this case, the first side may intersect the plane more steeply than the second side. In other words, the first side may form a first angle α with the plane, and the second side may form a second angle β with the plane. The first angle α may be greater than the second angle β. Alternatively, as shown in Figure 7, the first angle α may be less than the second angle β. For example, in the case of a symmetrical rib cross-sectional shape as shown in Figures 1, 2a, and 2b, the first angle α and the second angle β can be of equal size.

[0066] Figures 8a and 8b show a seventh example of the joint element 100. In contrast to all other examples described according to embodiments of this disclosure, the joint element 100 comprises a shaft 20 having a threaded portion 24 in addition to the rib portion 22. The threaded portion 24 may have threads, in particular male threads, i.e., a single groove. The rib portion 22 can be configured as described with reference to Figures 1-7, 9a and 9b. The rib portion 22 may be positioned on the tip portion 23 side of the threaded portion 24. In other words, the rib portion 22 may extend from the threaded portion 24 in the axial direction Z.

[0067] Figure 8b shows a longitudinal cross-section corresponding to Figure 8a, where the transition from the threaded portion 24 to the rib portion 22 is indicated by a dotted line. Furthermore, a portion of the parallel plane surrounding the shaft 20 by the rib 1 is indicated by a dashed line.

[0068] Figures 9a and 9b show an eighth example of the joint element 100. In the example of Figure 9a, the parallel planes surrounding the shaft 20 by the ribs 1 are inclined with respect to the head 10. The ribs 1 or their corresponding planes may be at an angle other than 90° with respect to the axis of rotation RA. The axis of rotation RA may intersect the planes of the ribs at an angle other than 90°. Unlike threads, each rib 1 is formed within its own plane, where the ribs 1 or planes are arranged parallel to each other. Some of these planes are shown as dashed lines in the longitudinal section of Figure 9b. The groove diameter 2d may be constant in the axial direction Z in the rib portion 22 of Figures 9a and 9b. For clarity, the axial direction is not shown in Figures 4-9a and 9b, but it is the same as in Figure 1.

[0069] In the examples shown in Figures 1 to 7, 9a, and 9b, the rib portion 22 may completely cover the shaft 20 between the tip portion 23 and the base portion 21. This means that the shaft 20 does not need to have a complete screw thread.

[0070] The individual features of the rib portion 22 are described in different examples of the joint element 100, but the joint element 100 can have a combination of the described features. Thus, the rib 1 in Figures 4 and 5 can have a rounded shape in the longitudinal cross-section. Furthermore, the sawtooth shape in Figures 6 and 7 can be combined with the alternating groove widths 2w, 2w' according to Figure 4, and / or have a varying groove diameter according to Figure 5.

[0071] Figure 10 shows a longitudinal cross-sectional view (photograph) of the joint element 100 after use in the method according to the embodiment of the present disclosure.

[0072] In the first step, a first workpiece, a second workpiece, and a joining element 100 (as described above) were provided. The first and second workpieces may be planar workpieces as shown in Figure 10. The first workpiece may be placed on top of the second workpiece. As shown in Figure 10, neither workpiece had holes or recesses at the joining point.

[0073] In the second step, the joining element 100 is placed on the surface of the first workpiece. The joining element 100 can be placed on the first workpiece by a joining tool, particularly by a pressing device. This allows the joining element 100 to make direct contact with the surface of the first workpiece. The joining element 100 can be placed from one side, i.e., on the opposite side of the second workpiece, without any auxiliary structures.

[0074] In the third step, the joining element 100 is set to rotate at a predetermined rotational speed. Direct contact between the joining element 100 and the first workpiece, and the resulting frictional force, heats the first workpiece as a result of the rotation. The heating of the first workpiece to a maximum of 300°C can be specified as the processing temperature.

[0075] In the fourth step, a predetermined axial force is applied to the joining element 100 in the direction of the surface of the first workpiece. This allows the joining element 100 to be pressed into the first workpiece, and subsequently into the second workpiece. Exemplary ranges of the predetermined rotational speed and predetermined axial force can be found, for example, in German Patent Application Publication No. 102024110303.

[0076] The joint element 100 has not yet been fully pushed through to the second workpiece. Instead, a protrusion has been formed, and as a result, the shaft 20 of the joint element 100 is fully embedded in the two workpieces.

[0077] According to the joining element of the present invention, in a drilling joining method, chips are essentially generated at the tip that are shorter than the adjacent joining elements in terms of thread length. Neither the multiple ribs 1 nor the grooves 2 formed between them have a helical shape. Therefore, chip surfaces such as those in threads can be avoided, and filamentous material residue is reduced, thus reducing the risk of the joining elements coming loose or being manipulated as a result of vibration.

Claims

1. A joining element for joining two workpieces, The head and The head comprises a shaft extending from the bottom of the head, The aforementioned shaft is The base extending from the bottom of the head, A tip portion that forms the end of the shaft opposite to the head, A joining element comprising a rib portion located between the base portion and the tip portion and having a plurality of ribs.

2. The joining element according to claim 1, wherein each rib of the rib portion surrounds the shaft in its respective plane.

3. The joining element according to claim 1, wherein each rib in the rib portion is perpendicular to the shaft axis.

4. The joining element according to claim 1, wherein each rib in the rib portion has a certain rib projection and / or a certain rib diameter.

5. The joining element according to claim 1, wherein the ribs are each formed parallel to each other, and / or the planes on which the ribs surround the shaft are each parallel to each other.

6. The joint element according to claim 1, wherein the rib portion covers 30% or more of the shaft.

7. The joint element according to claim 1, wherein the rib portion covers 50% of the shaft.

8. The joining element according to claim 1, further comprising a threaded portion disposed between the rib portion and the base portion.

9. The joining element according to claim 1, wherein the rib has an asymmetrical rib cross-sectional shape.

10. The joining element according to claim 1, wherein the rib portion has a trapezoidal shape in its longitudinal cross-section.

11. The joining element according to claim 1, wherein a circumferential groove is formed between each pair of ribs, each circumferential groove has a constant groove depth, and the depth of the circumferential groove changes along the axial direction of the shaft, and increases particularly in the direction of the tip.

12. The joining element according to claim 1, wherein the rib portion completely covers the region between the base portion and the tip portion.

13. The joining element according to claim 1, wherein the rib has a first rounded shape in its longitudinal cross-section, and / or the circumferential groove has a second rounded shape in its longitudinal cross-section between the ribs, the second rounded shape having a curvature opposite to that of the first rounded shape.

14. The joining element according to claim 13, wherein the first rounded shape and the second rounded shape have the same curvature.

15. The joining element according to claim 1, wherein a groove having a first groove width is formed between each pair of ribs, and at least one of the grooves has a second groove width that is greater than the first groove width.

16. The joining element according to claim 15, wherein one of the grooves having the second groove width connects its tip to the rib portion.

17. The joint element according to claim 1, wherein the axis of rotation of the joint element intersects the plane of the rib perpendicularly or at an angle other than 90°.

18. A method for manufacturing a drilled joint between two workpieces, The steps include providing a first workpiece, a second workpiece, and a joining element according to claim 1, The steps include: placing the joining element on the surface of the first workpiece; The steps include rotating the connecting element at a predetermined rotational speed, A method comprising the step of applying a predetermined axial force to the joining element in the direction of the surface of the first workpiece.

19. The method according to claim 18, wherein the method is a flow drill fastening method.

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