CONNECTING ELEMENT AND TOOL FOR FIXING A CONNECTING ELEMENT TO A PART BY FRICTION WELDING - Patent application

Abstract

The present invention relates to a connecting element for fastening to a part, in particular a part made of a fiber composite material including a thermoplastic material, comprising a main part, a functional part and a friction welding inlay, wherein tool application points are formed on the upper surface of the main part, and the friction welding inlay is connected to the main part in an interlocking and / or force-locking manner.

Description

Technical Field

[0001] The present invention relates to a connecting element for fixing to the surface of a component made of a fiber-reinforced composite material such as CFRP or GFRP, particularly a thermally adhesive bonding projection.

Background Art

[0002] Such connecting elements are necessary, for example, to fix an attachment to a weight-optimized CFRP component or to connect it to other parts. In the case of components made of fiber composite materials, it is often undesirable or even impossible to drill holes in the component in order to guide rivets or screws through the component and connect the connecting element to the component in this well-known and established way. This limitation is because each hole disturbs the fiber pattern in the component made of the fiber-reinforced composite material (composite component) and reduces its load-bearing capacity. Also, inappropriate introduction of holes can lead to delamination.

[0003] To avoid these drawbacks, such connecting elements have conventionally been adhered to the surface of CFRP components. However, this securing method has various drawbacks. In particular, the long curing time of the adhesive for automated continuous production and the difficulty of manufacturing such an adhesive bond in a highly process-reliable way are drawbacks.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem addressed by the present invention is to provide a connecting element that avoids the drawbacks of the prior art. The connecting element is intended to be able to be connected to a component in a highly process-reliable and automated way without the component requiring holes. Furthermore, it is intended not only to be cost-effective but also to be flexible enough to adapt to different operations / fixing operations.

Means for Solving the Problems

[0005] This problem is solved by the present invention, which provides a connecting element for fixing to the surface of a part by friction welding, particularly a heat-adhesive bonding projection, comprising a main part and a functional part, wherein the main part has an upper surface and a lower surface opposite the upper surface having an annular bead, the main part has an opening connecting the upper surface and the lower surface, and the functional part has a shank and a head at the first end of the shank, wherein the diameter or spread of the head across the longitudinal axis of the shank is larger than the diameter of the opening of the main part.

[0006] Therefore, the connecting element according to the present invention is divided into two parts. The connecting element comprises a main part having a bead on its lower surface. The bead "supplies" the welding addition during friction welding. Furthermore, the strength of the friction welding process and the friction-welded joint can be easily and flexibly adapted to composite material parts and fastening operations by corresponding designs (particularly diameter, width, height and cross-sectional shape).

[0007] Furthermore, the connecting element according to the present invention comprises a functional part, the shank of which is inserted from below through an opening in the main part until the head of the functional part abuts against the lower surface of the main part. Tensile force can then be transmitted between the functional part and the main part. As soon as the main part is fixed to the part by friction welding in a manner bonded to its bead, the functional part is indirectly but permanently connected to the part. If necessary, a rotatable interlocking connection between the functional part and the main part can also be easily manufactured.

[0008] The two-part design allows different functional parts to be combined with a structurally identical main body, so that the functional parts can be used to create snap connections or screw connections by female or male threads without any changes to the main body and joining process according to the present invention. For example, a fixing element with a snap connection and a fixing element with female threads can be combined with different functional parts and fixed to a part using the same friction welding apparatus without changing process parameters, by a structurally identical main body supplied to the apparatus for friction welding. This is a great advantage for process-reliable continuous production of high-performance lightweight parts.

[0009] The connecting element according to the present invention is highly cost-effective because the materials of its two components (main part and functional part) can be optimized according to the relevant work. The main part is often made of a thermoplastic material. Preferably, it is made from a fiber-reinforced thermoplastic material such as PA 66 35 GF. Other (thermoplastic) plastic materials can, of course, be used with or without fiber reinforcement. Polyphenylene sulfide (PPS), polyamide 6 (PA 6), and polypropylene with 30% glass fibers (PP GF30) are particularly suitable.

[0010] However, the connecting element according to the present invention can also be manufactured from a metal material that can be pressure-welded.

[0011] Next, the connecting elements can be connected to the metal parts by friction welding. In this case, the parts and the main body must be able to be pressure-welded together. Since the functional parts are connected to the connecting parts only by an interlocking method and not by material bonding, there are no restrictions on the material of the functional parts.

[0012] These non-exhaustive examples demonstrate the great flexibility and adaptability of the connection elements according to the present invention to a wide variety of requirement profiles.

[0013] According to the present invention, at least one interlocking element is formed on the upper surface and / or outer casing of the main body, and the at least one interlocking element is designed to transmit the torque required during friction welding from the joining tool to the main body.

[0014] One or more interlocking elements may, for example, be provided with one or more preferably circular recesses (blind holes) on the upper surface of the main body. Alternatively, interlocking elements may be formed as longitudinal grooves or recesses on the outer casing of the main body. Of course, the main body may also be formed with a non-rotationally symmetrical geometric casing, such as a polygon (triangle, quadrilateral, pentagon, hexagon, etc.) or equivalent, so that the torque required for friction welding can be introduced into the main body through the casing. This results in connecting elements with smooth surfaces.

[0015] Due to the numerous possible interlocking elements, the main design is largely unconstrained. Rather, design concerns can be taken into account, resulting in a compelling design.

[0016] For example, in applications where cleanliness is of paramount importance, a main body enclosure with a smooth surface free of depressions or grooves may be particularly advantageous. In this case, the main body enclosure may be polygonal or similar in shape. Blind holes and grooves on the enclosure may be omitted.

[0017] To ensure good and elastic transmission of tensile force from the shank of the functional part to the main part, the head of the functional part is designed as a plate, preferably as a non-rotationally symmetric plate. If the plate is not rotationally symmetric and a corresponding recess is formed on the underside of the main part, torque can also be transmitted between the main part and the functional part. This is often advantageous when the functional part has male or female threads on its shank and a screw or nut is screwed into the functional part. The dimensions of the head are determined according to the set of loads (axial force, torque) to which the connecting element is subjected, and the expected axial force is selected.

[0018] The functional part may optionally have a centering portion that interacts with an opening in the main part of the housing. The functional part is then positioned at the center of the opening in the main part by the centering portion. In this case, a tight fit or a slight interlocking fit may also be provided, and when the centering portion of the functional part is pushed into the opening in the main part, the two components of the connecting element according to the present invention are connected to each other. This facilitates handling (manual or automated) of the connecting element according to the present invention before the main part is pressed against the component.

[0019] Depending on the application requirements, the shank of the functional part can be part of the snap connection. However, it may have male or female threads. A lateral hole for receiving a cotter pin and a groove for receiving a retaining ring (Sieger ring) may also be formed. A barb may be placed on the shank, thereby allowing soft materials to be secured to the shank. The shank can be designed to connect optimally to one or more parts. There are no restrictions on the design of the shank.

[0020] The invention described in the claims also includes a tool for joining a connecting element to a part, the tool having at least a partially hollow or tubular tool body, the first end of which is designed to form a rotatable interlocking connection with the centering portion of the main and / or functional portion when the first end is positioned over the connecting portion. A cavity / center hole within the tool body is used to house the shank of the functional portion.

[0021] The first end of the tool according to the present invention is complementary to the upper surface or outer casing of the main part. For example, as shown in Figure 1, if a recess is formed on the upper surface of the main part, the first end of the tool according to the present invention has three pins that fit into the recess when the tool is placed on the main part. Numerous other designs are possible. However, for the complementary design of the first end of the tool and the main part, it is important that the torque required for friction welding is transmitted from the tool to the main part during the friction welding process, and that the connecting element according to the present invention is connected to the part in this manner.

[0022] Further advantages and advantageous embodiments of the present invention can be found in the following drawings, the description thereof and the claims. All features disclosed in the drawings, the description thereof and the claims may be essential to the present invention both individually and in any combination with each other.

[0023] Drawings

[0024] In the drawings:

Brief Description of the Drawings

[0025] [Figure 1a] FIG. 1 is a view of the main part of the connecting element according to the present invention as seen from above; [Figure 1b] [Figure 2] FIG. 2 is a side view of the main part; [Figure 3] FIG. 3 shows a cross-sectional view through the main part according to the present invention; [Figure 4] FIG. 4 is a view of the main part according to the present invention as seen from below; [Figure 5] FIGS. 5 to 7 are different views of the functional part according to the present invention; [Figure 6] [Figure 7] [Figure 8] FIG. 8 partially shows a two-part connecting element according to the present invention having a main part and a functional part; [Figure 9] FIG. 9 shows a two-part connecting element pressed against a component; [Figure 10] FIG. 10 shows an embodiment of a tool according to the present invention for joining the connecting element to a component.

Modes for Carrying Out the Invention

[0026] Description of Embodiments

[0027] Figure 1a is a view from above of the main body 1 of the connecting element according to the present invention. In this embodiment, the main body 1 is designed as a substantially circular disk or plate. The main body has an opening 3 in the center. Three circular recesses 5 are arranged on the upper surface of the main body 1, distributed circumferentially. The recesses are blind holes used to transmit the torque required for friction welding from the tool to the main body 1 by corresponding pins of a complementaryly designed and positioned tool (see Figure 9).

[0028] Another alternative for torque transmission between the friction welding tool and the main body 1 is shown in Figure 1b: three longitudinal grooves or recesses 7 are arranged on a circular outer casing. The recesses 7 can form interlocking engagements with corresponding ribs or pins on the friction welding tool, thereby allowing the required torque to be transmitted from the tool to the main body 1. In this case, the recesses 5 in the first embodiment can be omitted.

[0029] It is not necessary to form both the recess 5 and the groove 7 in a single main part. Generally, one of the elements 5 or 7 is sufficient. The main part 1 can be centered relative to the tool by both the longitudinal groove 7 and the recess 5. However, the main part 1 can also be centered relative to the tool, for example, by the complementary design of the main part 1's outline and the tool.

[0030] Furthermore, instead of forming the main part 1 in a circular shape, it can be formed, for example, as a hexagon or an equivalent (polygon). Then, torque can be transmitted from the tool to the main part by a tool having a complementary shape rather than rotational symmetry in the outer casing. In this case, neither the recess 5 nor the longitudinal groove 7 is necessary. This results in a smooth outer casing of the main part 1 that is particularly resistant to contamination. Illustrations of this embodiment are omitted.

[0031] The dashed circular lines in Figures 1a and 1b indicate the bead 9 and recess 11 on the lower surface of the main part 1. The form and function of the bead 9 and recess 11 will be described in more detail later in relation to Figures 3 and 4.

[0032] Figure 2 is a side view of the main body 1 according to the present invention. From this side view, the basic disc-shaped structure of the main body 1 is clear. The bead 9 is clearly visible on the lower surface of the main body 1 (lower part of Figure 2). The bead 9 is used as a welding add-on or material add-on for friction welding. Specifically, when the main body 1 is connected to a part (not shown) by friction welding, the main body 1 is set to rotate, and at the same time the bead 9 is pressed against the part. Due to the resulting frictional heat, the material of the bead 9 becomes at least partially soft and plastic. As soon as this process has progressed sufficiently, the rotation is stopped, and the main body is pressed against the part together with its liquefied / plasticized bead 9 until the material of the bead 9 solidifies again.

[0033] Figure 3 shows the main part 1 in a cross-sectional view. In this figure, the central opening 3 and one of the three recesses 5 are clearly visible. A small rib 13 is formed in the recess 5. It is used to create a press fit together with a pin (not shown) of a joining tool. At that time, the connecting element (main part 1) and the functional part (not shown) according to the present invention will not detach from the tool before the element or part is joined to the component.

[0034] The recess 11 on the lower surface of the main part 1 is clearly visible in Figure 3. The recess 11 has a circular basic shape and a flat portion 15 on its right side, as is particularly clear from Figure 4; therefore, it is not rotationally symmetric. This flat portion 15 is used to provide a rotationally fixed interlock connection with the head of a functional part (not shown).

[0035] The dimensions of the bead 9, particularly its height, width, diameter, and cross-section, determine the available pressure welding addition and friction welding process parameters. The dimensions of the bead 9 can be adjusted according to application requirements. The good adaptability of the connecting element according to the present invention to different applications is also evident here.

[0036] In the illustrated embodiment, the bead 9 is relatively large, and as a result, a large amount of material is available for friction welding.

[0037] In Figure 4, the main part 1 is shown as viewed from below. From this figure, the shape of the recess 11, along with the flat part 15, is particularly clear. The outer shape of the main part 1 is indicated by 17 in Figure 4.

[0038] Figures 5 to 7 show different diagrams of two embodiments of the functional part 19 according to the present invention. Figure 5 is a top view of the first embodiment of the functional part 19. As can be seen from Figures 5 to 7, the functional part 19 comprises a head 21, a centering part 23, and a shank 25 in all embodiments.

[0039] As can be seen particularly clearly from the view from above (Figure 5), the head 21 is circular and has a flat portion 27. The head 21 and the flat portion 27 are complementary to the recess 11, with the flat portion 15 located on the lower surface of the main portion 1. As a result, when the shank 25 is pushed in from below through the opening 3 of the main portion 1 until the head 21 abuts against the main portion 1, a rotational fixed interlock connection is created between the head 21 of the functional portion 19 and the main portion 1.

[0040] In the illustrated embodiment, the functional part 19 includes an (optional) centering part 23 whose dimensions match the diameter of the opening 3 of the main part 1. When the shank 25 of the functional part is pushed into the main part through the opening, a slight press-fit preferably occurs between the centering part 23 and the opening 3 of the main part 1. This prevents the functional part 19 from accidentally falling out of the main part 1 again.

[0041] The recessed portion 11 and the flat portions 15 and 27 within the head portion 21 ensure reliable and efficient torque transmission between the functional portion 19 and the main portion 1, respectively. Torque transmission is not limited to the illustrated embodiment. Furthermore, large axial forces can also be transmitted between the functional portion 19 and the main portion 1 via the head portion 21.

[0042] In Figure 6, the shank 25 of the functional part 19 is designed as part of a snap connection. The shank has a number of undercuts 29 that form the aforementioned snap connection together with the corresponding latch hook or snap hook (not shown) of the corresponding part.

[0043] An alternative functional part 19 is illustrated in Figure 7. In this case, the shank 25 has an internal thread. The centering part 23 and the head 21 are structurally identical to those in the embodiment shown in Figure 6. This has the advantage that the functional parts 19 shown in Figures 6 and 7 can be used interchangeably with the same main part 1. As a result, there is no change in the friction welding process for connecting the main part 1 to the component. Due to the two-part design, many more functional parts 19 (not shown) can be combined with the same main part. There are almost no restrictions on the design freedom of the functional parts 19. The functional parts 19 can also be made from a different material than the main part 1.

[0044] Figure 8 shows an assembly diagram of the connecting element according to the present invention. The connecting element 31 is formed in two parts. As already mentioned, the connecting element comprises a main part 1 and a functional part 19. A slight press fit between the opening 3 and the centering part 23 prevents the functional part 19 from falling out of the main part 1.

[0045] Next, the two connecting elements according to the present invention may be placed on a joining tool and connected to the parts by friction welding in the manner described above.

[0046] Figure 9 shows the connecting element according to Figure 8, which is connected to the composite material part 30 by friction welding. The bead 9 is remarkably flat and wide. This is a result of the plastic deformation and deformation of the bead 9 that occurs during friction welding. The bonding area between part 30 and the main part 1 of the connecting element is much larger than the cross-sectional area of ​​the bead 9 before friction welding. As a result, the load capacity of the joint is very high. As already mentioned, the bonding surface can be adapted to the requirements of individual cases within a very wide range of limitations by the dimensions and design of the bead 9.

[0047] Figure 10 shows an embodiment of a tool 31 according to the present invention for joining. It comprises a tubular body 33 that houses the shank 25 of the connecting element.

[0048] The first end 35 of the tool 31 is designed as a contact surface 36 for the main part 1. Three pins 37 are pressed against the end face of the tool 31, two of which are visible. These pins 37 move into the recess 5 of the main part 1 shown in Figure 1a, thus providing an interlocking connection suitable for transmitting the torque required for friction welding from the tool to the connecting element.

[0049] The drive element 39 is located at the end opposite to the first end 35. In the illustrated embodiment, the drive element 39 is a cylindrical pin having two parallel surfaces for clamping within the tool holder. The tool 31 is clamped to the drive element within a device for friction pressing.

[0050] List of reference symbols [Explanation of Symbols]

[0051] 1. Subject 3 aperture 5. Indentation 7. Vertical grooves 9 beads 11. Recess / Indentation 13 Ribs 15 Flat area 17 Outer shell 19 Functional Section 21 Head 23 Centering section 25 Shank 27 Flat area 29 Undercut 30 parts 31 Tools 33 Tubular body 35 First end 37 pins 39. Drive element 41 Female thread

Claims

1. A connecting element for fastening to a surface of a part (38) by friction welding, comprising: The connecting element comprises a main part (1) and a functional part (19), The main part (1) has an upper surface and a lower surface opposite the upper surface and provided with an annular bead (9); The main portion (1) has an opening (3) connecting the upper surface and the lower surface, The functional portion (19) has a shank (25) and a head (21) at a first end of the shank (25), the diameter or extent of the head transverse to the longitudinal axis of the shank (25) is greater than the diameter of the opening (3); Connection element.

2. the main part (1) has at least one interlocking element on the top surface and / or on the outer shell (17); The at least one interlocking element is designed to transmit the torque required during friction welding from a tool (31) for joining to the main part (1). A connecting element according to claim 1 .

3. The interlocking element has one or more recesses (5) on the upper surface of the main part (1). A connecting element according to claim 2 .

4. The interlocking element may have one, two or more longitudinal grooves (7) or recesses on the outer contour (17) of the main part (1). A connecting element according to claim 2 .

5. One of the interlocking elements has a non-rotationally symmetric outer contour (17). A connecting element according to claim 2 .

6. The head (21) of the functional part (10) is designed as a plate. A connecting element according to any one of claims 1 to 5.

7. The lower surface of the main part (1) is complementary to the head part (21) of the functional part (19) such that the functional part (19) and the main part (1) are connected to each other in a rotationally fixed and interlocking manner. A connecting element according to any one of claims 1 to 6.

8. The functional part (19) has a centering part (23) which interacts with the opening (3) in the main part (1). A connecting element according to any one of claims 1 to 7.

9. The opening (3) of the main part (1) and the centering part (23) of the functional part (19) are connected to each other in a rotationally fixed and interlocking manner. A connecting element according to any one of claims 1 to 8.

10. The shank (25) of the functional part (19) has one or more undercuts (29). Designed as part of a snap connection A connecting element according to any one of claims 1 to 9.

11. A male and / or female thread (41) is formed on the shank (25) of the functional part (1). A connecting element according to any one of the preceding claims.

12. The main part (1) is made of a material that can be pressed. A connecting element (10) according to any one of the preceding claims.

13. A connecting element as described in claim 2, characterized in that one of the interlocking elements has an outer contour of a regular polygon, an irregular polygon, or a figure of constant width (Gleichdick).

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