Riveted structure

Abstract

This invention relates to a riveting structure in which the rivet feet (11) of the riveting element (1) are subjected to the following pressure (F) S The rivet foot (11) is pressed into the member (3), more specifically, when the rivet foot (11) is spread out, wherein the rivet foot (11) has a reduced cross-section in its undeformed state and a widened cross-section in its pressed-in state. According to the invention, the rivet foot (11) is designed as a bistable spring segment having two equilibrium states, namely, an undeformed state with a reduced cross-section and a widened spread-out state. By applying downward pressure (F... S The action of the rivet (1) causes the riveting element (1) to fold from its undeformed state to its open state. In the open state, the rivet foot (11) is spread open in the member (3) with a widened cross section. More precisely, in particular, without forming a spring force, the spring force is applied to the riveting element (1) in the direction of the undeformed state.

Description

Technical Field

[0001] This invention relates to a riveting structure. Background Technology

[0002] In this riveting structure, the rivet feet of the riveting element are pressed into the component by the following pressure, more precisely, while the remaining bottom thickness of the component is maintained and the rivet feet are stretched open. In the undeformed state, the rivet feet have a reduced cross-section. In the pressed-in state, the rivet feet have a widened cross-section.

[0003] In the prior art, this riveting structure is established during the riveting process. During riveting, the riveting element has a widened rivet head and rivet feet, with the rivet feet having an inwardly arched portion open at the tip. During installation, the component without pre-punched holes is clamped between the bottom mold and fixture of the installation machine. The riveting element is pressed in with a predefined downward pressure, thereby causing the tip of the rivet feet to widen radially outward through a spreading path. This creates an undercut between the rivet head and the widened tip of the rivet feet, which is filled with component material. At this point, the tip of the rivet feet is form-locked and surrounded by the component material. This prevents relative movement, for example, due to the springback of the rivet feet after spreading, as deformation of the component is required for this.

[0004] When using component materials with low ductility, such as cast aluminum, this form-locking enclosure at the tip of the rivet can only be achieved with limitations, resulting in springback of the rivet after installation (after being spread out). Therefore, the riveted components cannot be adequately tightened to prevent loosening. Furthermore, the low ductility of the component material poses a risk of scratches, which may lead to premature cracking or breakage of the component.

[0005] A joint connection structure is known from DE 10 2018 122 200 A1. A riveting process is known from WO 95 / 35174 A1. A method for establishing a connection between a functional element and a plate-like component is known from DE 10 2015 014 941 A1. Summary of the Invention

[0006] The object of the present invention is to provide a riveting structure in which the riveting elements are fastened in a simple manner to prevent accidental loosening from the component.

[0007] This invention is based on a riveting structure in which the rivet feet of a riveting element are pressed into at least one component by a pressure, more specifically, while the remaining bottom thickness of the component is maintained and the rivet feet are stretched. In its undeformed state, the rivet feet have a reduced cross-section. In the pressed-in state, the rivet feet, conversely, have a widened cross-section.

[0008] According to one aspect of the invention, unlike the conventional riveting process, the form-locking enclosure of the widened rivet foot tip is eliminated. Instead, according to the invention, the following working principle is used to fasten the riveting element to the component: that is, the rivet foot forms a bistable spring section with two equilibrium states. The first equilibrium state corresponds to the undeformed rivet foot state with a reduced cross-section. By applying downward pressure, the rivet foot is folded into a second equilibrium state, in which the rivet foot is spread open in the component with a widened cross-section. The folding into the spread state is carried out essentially without creating a spring force that would otherwise propel the riveting element toward the undeformed state.

[0009] Therefore, according to the present invention, the deformation of the riveting element is performed during the installation process using the so-called spring impact effect (also known as the spring frog effect). The spring impact effect is understood as a physical effect in which the shape of the riveting element has two stable states that can be transformed into each other by the application of a suitable force.

[0010] In one technical implementation, the component in its undeformed state can be designed not to be completely without pre-punched holes, but rather to have pre-punched holes at the joint to be formed. In the assembled state, the rivet feet of the riveting element are pushed outwards towards the inner periphery of the pre-punched holes.

[0011] The riveting element can be designed to be rotationally symmetrical about its longitudinal axis. Furthermore, the riveting element can have a widened rivet head that transitions axially into the rivet foot. Another functional element, such as a threaded bolt, can also be formed on the upper side of the rivet head. According to the invention, the rivet foot can be divided into a solid rivet foot section on the head side and an inner arched portion connected to the solid rivet foot section. The inner arched portion is designed to open towards the tip of the rivet foot and terminate at a circumferentially surrounding mounting edge. The inner arched portion is confined by a surrounding rivet foot wall, the rivet foot wall material transitioning uniformly and integrally into the solid rivet foot section. In this case, the rivet foot wall can form a bistable spring section. In the extended state, the rivet foot wall can fold in the opposite direction to the mounting direction, that is, towards the rivet head. In this case, the mounting edge can be extended and engage with the inner periphery of a pre-punched hole in the component. Furthermore, the rivet foot wall is disc-shaped and continuously surrounds the solid material section of the rivet foot in the circumferential direction without any gaps.

[0012] In one technical implementation, the component can be a casting, such as an aluminum die casting, while the riveting element can be made of cold-worked (cold riveting, cold hammering, cold forging, cold forging) material. Particularly preferred in this case is that the component undergoes essentially no plastic deformation during the installation process, that is, it is subjected primarily to elastic loads. Particularly preferred is that the component remains substantially undeformed after the installation process is completed.

[0013] Advantageously, in terms of the unimpeded transition of the riveting element from its undeformed state to its expanded state, the pre-punched hole of the component has a corresponding activation profile. With the aid of this activation profile, the transition of the riveting element from its undeformed state to its second expanded state can be reliably performed during installation. In a preferred embodiment, the pre-punched hole can have the following geometry: that is, the pre-punched hole can be implemented as a blind hole with a closed bottom. This blind hole can have a larger diameter inlet section. The inlet section transitions into a smaller diameter recess at a surrounding annular shoulder. The mounting edge of the undeformed riveting element can be located on a diameter larger than the inner diameter of the annular shoulder. Thus, (in preparation for the installation process), the riveting element can be positioned on the annular shoulder of the pre-punched hole using its mounting edge.

[0014] Under downward pressure, the riveting element can widen radially outward using its mounting edges, more precisely, until it reaches its maximum outer diameter. As the installation process continues, the solid material section of the rivet foot can be pressed into the pre-punched recess with an additional over-dead-point travel distance. This achieves over-deformation or over-spreading of the rivet foot, in which the rivet foot folds into the spread position.

[0015] Preferably, the riveting element can be made of a cold-worked material, in which case, especially when the deformation limit is exceeded during over-stretching, hardening of the riveting element material occurs, which is advantageous in improving the connection strength between the riveting element and the component. Therefore, according to the invention, the bottom mold whose shape assists in the rivet foot stretching can be eliminated. Instead, the component can be clamped in the middle between a jig and a flat anvil.

[0016] The installation process according to the invention can be part of a fully automated process chain in which the installation machine is fixed at the distal end of the robotic arm of an industrial robot that operates autonomously under program control. To ensure an unobstructed installation process, it is preferable that the outer diameter of the rivet foot is designed to be smaller than the outer diameter of the annular shoulder. In this way, the undeformed riveting element can be positioned on the annular shoulder in a floating support manner, i.e., with lateral clearance, using its mounting edges, thereby compensating for component tolerances and / or manufacturing tolerances.

[0017] When using die-cast parts, pre-punched holes can be created in the surface of the component during the casting process. In this case, the pre-punched holes can have a tapered inner circumference that serves as a demolding ramp. During the assembly process, the tapered inner circumference also serves as an entry ramp to ensure that the riveting element is positioned unobstructed on the annular shoulder of the pre-punched hole. Attached Figure Description

[0018] An embodiment of the present invention will now be described with reference to the accompanying drawings.

[0019] in:

[0020] Figure 1 The riveting structure is shown in cross-sectional view;

[0021] Figures 2 to 4 Views illustrating the processing steps used to create the riveted structure are shown respectively;

[0022] Figure 5 and Figure 6 Views of comparative examples not included in this invention are shown respectively. Detailed Implementation

[0023] To more easily understand this invention, first refer to... Figure 5 and Figure 6 ,according to Figure 5 and Figure 6 Describe the riveting structures known in the prior art. Figure 5 The riveting structure shown consists of a riveting element 1 and a component 3. The riveting element 1 is designed to be rotationally symmetrical with respect to the longitudinal axis L of the riveting element. Furthermore, the riveting element 1 has a widened rivet head 9 that transitions axially into the rivet foot 11. The rivet foot 11 is divided into a solid material section 13 on the head side and a cylindrical rivet foot wall 17 connected to the solid material section. The rivet foot wall ends at a circumferentially surrounding mounting edge 15 and is confined to an open inner arch 14 at the tip of the rivet foot.

[0024] This installation process is achieved using an installation machine. Figure 5 or Figure 6 The installation machine includes a clamp 27, an installation piston 29, and a bottom mold 30. The bottom mold is designed so that the auxiliary rivet feet 11 are radially outwardly extended during installation. During installation, the component 3 without pre-punched holes is clamped between the bottom mold 30 and the clamp 27. The riveting element 1 is installed by the piston 29 with a predefined downward pressure F. S As it is pressed in, the tip of the rivet widens radially outward through the spreading path. The downward pressure F introduced into the riveting element 1... S The load path is distributed at the top portion above the inner arch 14, where the load path is located. Figure 5 or Figure 6 The expansion line 16 extends along the envisioned (indicated by the dotted line) spreading line. The spreading line 16 unfolds to form a spreading angle α. During the installation process ( Figure 6 In the process, the riveting element 1 is pressed in with the installation stroke until the bottom dead center T ( Figure 6 At the bottom dead center T, the tip of the rivet foot contacts the component material and opens at an angle α (towards...). Figure 5(Compared to) the increase. As a result, an undercut is created between the rivet head 9 and the widened rivet foot tip, which is filled with component material.

[0025] During installation, the riveting element 1 deforms not only plastically but also elastically; more precisely, it generates a springback force that is applied to the riveting element 1 towards its undeformed state. To prevent it from springing back to its undeformed state, in Figure 6 The tip of the rivet foot is form-locked and surrounded by the component material. This prevents relative movement, such as due to the springback of the rivet foot 11 after it has been opened, which would require deformation of component 3. In this way, the riveting element 1 is reliably secured to prevent loosening. To achieve the form-locking of the rivet foot tip by means of the component material, the component material needs to have sufficiently high fluidity or ductility.

[0026] Conversely, the riveting structure according to the invention can also be achieved using a component 3 with lower fluidity or ductility compared to the prior art. That is, according to the invention, the fastening of the riveting element 1 is not achieved by enclosing the rivet tip with a form-locking mechanism using component material, but rather by the fastening mechanism described below:

[0027] according to Figure 1 The riveting element 1 is pressed into the pre-punched hole 5 of the component, which tapers to a depth t and ends at the bottom 7 of the pre-punched hole. The core of this invention is that the rivet foot 11 serves as a bistable spring section. The rivet foot has two equilibrium states: a state where the undeformed cross-section is reduced (…). Figure 2 ) and the widened, expanded state ( Figure 1 or Figure 4 ). By applying downward pressure F S The function of the riveting element 1 is to maintain its undeformed state. Figure 2 The rivet foot 11 is folded into the open position, in which it expands within component 3 with a wider cross-section. This open position ( Figure 1 or Figure 4 The characteristic of this invention is that (unlike the prior art) it substantially does not generate a springback force that applies to the riveting element 1 in the direction of its undeformed state. Therefore, according to the present invention, the method of enclosing the tip of the rivet foot by means of a form-locking mechanism with the component material can be eliminated.

[0028] The following is based on Figures 2 to 4 The pre-punching geometry of component 3, the geometry of the riveting elements, and the installation process according to the present invention are described: Therefore, according to Figure 2 The undeformed riveting element 1 is designed to be rotationally symmetric with respect to its longitudinal axis L. Figure 1In the figure, the rivet foot 11 is divided into a solid rivet foot section 13 on the head side and an inner arched portion 14 connected to the solid rivet foot section, the inner arched portion opening at the top of the rivet foot. The inner arched portion 14 ends at the mounting edge 15 that is circumferentially surrounded by the riveting element 1. Furthermore, the inner arched portion 14 is limited by the surrounding rivet foot wall 17, the rivet foot wall material transitioning uniformly and integrally into the solid rivet foot section 13. In the figure, a functional section 19, such as a threaded bolt, is formed on the upper side of the rivet head 9.

[0029] The folding of the rivet foot wall 17, which serves as the bistable spring section, is achieved by means of a special activation profile 32 in the pre-punched hole 5 of the component. Figure 2 With the assistance of [unclear], the activation contour is designed as follows: that is, in [unclear] Figure 2 The pre-punched hole 5 of the component has a larger diameter inlet section 21. This inlet section transitions in a stepped manner at the surrounding annular shoulder 23 into the smaller diameter pre-punched hole recess 25 in the direction of the bottom 7 of the pre-punched hole. Before the riveting element 1 is deformed, the mounting edge 15 extends on a diameter d1 that is designed to be larger than the inner diameter d2 of the annular shoulder 23. In addition, the outer diameter of the rivet foot is designed to be smaller than the outer diameter d3 of the annular shoulder.

[0030] The installation process is performed using an installation machine. Figure 3 In the process, the mounting machine has a clamp 27, in which the mounting piston 29 is guided in a reciprocatingly adjustable manner. The component 3 is clamped in the middle between the clamp 27 and the mating contour 31 of the plane. This is similar to the bottom mold 30 known from the prior art. Figure 5 and Figure 6 Unlike other mating profiles, the mating profile 31 does not have a special profile for assisting the spreading movement of the rivet foot 11; instead, it is designed to be planar. It also does not exhibit the characteristics seen in... Figure 5 and Figure 6 The deformation of component 3 is shown in the prior art. Figure 3 In the process, the riveting element 1 is supported on the annular shoulder 23 in the pre-punched hole 5 of the component by its mounting edge 15. Under the downward pressure F S Under the action of the rivet foot 11, the mounting edge 15 expands radially outward, more precisely until it reaches the mounting stroke dead point T. Figure 3 At the installation dead point T, the mounting edge 15 of the riveting element 1 is at its maximum diameter d. max The rivet foot widens and expands, engaging with the inner circumference of the larger diameter inlet section 21 of the pre-punched hole 5. Furthermore, the end side of the rivet foot tip contacts the annular shoulder 23 over a large area. Additionally, at the installation stroke dead point T ( Figure 3 In the diagram, the spreading angle α, which is formed by the spreading line, is approximately 180°.

[0031] According to the present invention, the installation stroke beyond the dead point T is extended by a stroke distance s ( ). Figure 3 Therefore, as the installation process continues, the solid material section 13 of the rivet foot is pressed into the pre-punched recess 25 through a dead-point travel distance s. In this way, over-deformation or over-spreading of the rivet foot wall 17 occurs, in which the rivet foot wall 17 folds into a spread state. In the spread state, the spread angle α (as determined by the spread line 16) is... Figure 3 The dead point T of the installation stroke is increased to about 200°. Therefore, the rivet foot wall 17 is folded in the opposite direction to the installation direction, that is, in the direction of the rivet head 9. The folded rivet foot wall 17 extends continuously in the circumferential direction and extends in a disc shape around the solid material section 13 of the rivet foot of the riveting element 1.

[0032] As from Figure 2 It can also be seen that the inner circumference of the larger diameter inlet section 21 of the pre-punched hole 5 is designed to be tapered, thus serving as an inlet ramp. This inlet ramp allows the riveting element 1 to be smoothly inserted into the pre-punched hole 5. Furthermore, the riveting element 1 is positioned on the annular shoulder 23 by a floating support. Figure 2 In other words, it is positioned by lateral clearance, which can compensate for component tolerances and / or manufacturing tolerances.

[0033] List of reference numerals in the attached diagram:

[0034] 1. Riveting components

[0035] 3 components

[0036] 5. Pre-punching

[0037] 7. Bottom of pre-punched hole

[0038] 9 Rivet heads

[0039] 11 Rivet feet

[0040] 13. Solid material section for rivet feet

[0041] 14 Inner dome

[0042] 15 Install the edges

[0043] 16. Spread the lines

[0044] 17 Riveted foot wall

[0045] 19 Functional Sections

[0046] 21. Larger diameter inlet section

[0047] 23. Circular shoulder

[0048] 25 Pre-punched hole recess

[0049] 27 Fixtures

[0050] 29 Install piston

[0051] 30 Bottom Mold

[0052] 31. Planar mating profile

[0053] 32 Activation profile in component pre-punching

[0054] t Pre-punching depth

[0055] d1 Installation edge diameter

[0056] d2 Inner diameter of the ring shoulder

[0057] d3 outer diameter of the ring shoulder

[0058] F S Downforce

[0059] d max Maximum diameter

[0060] T dead point

[0061] s Distance traveled past the dead point

[0062] I. Longitudinal axis of the riveting component

[0063] α is the opening angle.

Claims

1. A riveting structure in which the rivet feet (11) of the riveting element (1) are subjected to the following pressure (F) S ) pressed into component (3), more precisely, when the rivet foot (11) is spread open, wherein, The rivet foot (11) has a reduced cross-section in its undeformed state and a widened cross-section in its pressed-in state. Its features are, The rivet foot (11) is designed as a bistable spring section, which has two equilibrium states: a reduced cross-section without deformation and a widened, expanded state. This is achieved by applying downward pressure (F... S The action of the rivet (1) causes the riveting element (1) to fold from the undeformed state to the open state. In the open state, the rivet foot (11) is opened in the component (3) with a widened cross section without forming a spring force that loads the riveting element (1) in the direction of the undeformed state.

2. The riveting structure according to claim 1, characterized in that, The component (3) has a pre-punched hole (5) at the joint to be established in an undeformed state, and the rivet feet (11) of the riveting element (1) in the riveting structure are spread out toward the inner periphery of the pre-punched hole (5).

3. The riveting structure according to claim 1 or 2, characterized in that, The riveting element (1) is designed to be rotationally symmetrical about the longitudinal axis (L) of the riveting element, and / or the riveting element (1) has a widened rivet head (9) that transitions axially into the rivet foot (11), and / or the rivet foot (11) is divided into a solid rivet foot section (13) on the head side and a cylindrical rivet foot wall (17) connected to the solid rivet foot section. The rivet foot wall ends at an annular mounting edge (15) and is confined to an open inner arch (14) at the top of the rivet foot, and / or the rivet foot wall (17) forms a bistable spring section.

4. The riveting structure according to claim 3, characterized in that, In the open state of the riveting element (1), the rivet foot wall (17) is folded in the opposite direction to the installation direction, that is, towards the rivet head (9), and / or the rivet foot wall (17) is disc-shaped around the solid material section (13) of the rivet foot, and / or the mounting edge (15) is opened and engages with the inner periphery of the pre-punched hole (5) of the component.

5. The riveting structure according to claim 2, characterized in that, The pre-punched hole (5) of the component has an activation profile (32), which assists the riveting element (1) in the transition from an undeformed state to an open state during installation.

6. The riveting structure according to claim 5, characterized in that, The component pre-punch hole (5) is a blind hole with a closed bottom (7), and / or in order to form an activation profile (32), the blind hole has a larger diameter inlet section (21) that transitions in a stepped manner at the surrounding annular shoulder (23) into a smaller diameter recess (25), and the mounting edge (15) of the undeformed riveting element (1) is located on a diameter (d1) larger than the inner diameter (d2) of the annular shoulder (23), so that when the installation process is ready, the riveting element (1) can be positioned on the annular shoulder (23) of the component pre-punch hole (5) using its mounting edge (15).

7. The riveting structure according to claim 6, characterized in that, During the installation process, the riveting element (1) can be pressed into the pre-punched hole (5) of the component until the dead point (T), and at the dead point (T), the riveting element (1) widens radially outward using its mounting edge (15) until it reaches the maximum diameter (d). max ), and / or the tip of the rivet foot contacts the pre-punched annular shoulder (23) planarly with its end side, and the installation stroke is extended by the over-dead travel distance (s), the solid material section (13) of the rivet foot can be pressed into the pre-punched recess (25) by the over-dead travel distance, thereby achieving over-deformation or over-spreading of the rivet foot wall (17), in which the rivet foot wall (17) is folded into the spread state.

8. The riveting structure according to claim 1 or 2, characterized in that, During installation, the riveted element (1) undergoes plastic deformation, while the component (3) is subjected to elastic load without plastic deformation and / or remains unchanged.

9. The riveting structure according to claim 2, characterized in that, The inner periphery of the pre-punched hole (5) of the component forms a tapered guide slope.

10. The riveting structure according to claim 1 or 2, characterized in that, The component (3) is a casting with low ductility, and / or the riveting element (1) is made of cold-worked material, in the case of cold-worked material, the deformation limit is exceeded when overstretched, and from this deformation limit, the riveting element material hardens.

11. The riveting structure according to claim 10, characterized in that, The outer diameter of the rivet foot is designed to be smaller than the outer diameter of the ring shoulder (d3), so that the undeformed riveting element (1) can be positioned on the ring shoulder (23) in a floating support manner using its mounting edge (15).

12. The riveting structure according to claim 2, characterized in that, The larger diameter inlet section (21) of the pre-punched hole (5) of the component forms a tapered inlet slope.

13. The riveting structure according to claim 10, characterized in that, Component (3) is an aluminum die casting.

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