SEMI-HOLLOW SELF-PIERCING RIVET, MANUFACTURING METHOD AND CONNECTION WITH SAME

Abstract

A rivet for connecting at least two components arranged one upon the other and are not pre-punched. The rivet has ahead, a shaft, a foot and a length L of the rivet between 7 mmL16 mm. The shaft has an outer diameter D.sub.S between 5.2 mmD.sub.S5.6 mm, and a bore hole with diameter D.sub.B between 3.1 mmD.sub.B3.5 mm and depth T.sub.B between 6 mmT.sub.B15 mm. A bore hole volume V.sub.B in the shaft between V.sub.BminV.sub.BV.sub.Bmax with V.sub.Bmin=7.3 [mm.sup.2].Math.L [mm] and V.sub.Bmax=0.9 [mm.sup.2].Math.L [mm] arises. In an axial sectional view, the foot has a conical outer chamfer and a conical inner chamfer interconnected by a cutting edge, the inner chamfer transitions into an inner bore wall of the shaft via a circular arc section and the outer chamfer and the inner chamfer enclose a cutting angle W.sub.S in the range from 80W.sub.S90.

Claims

1. A semi-hollow self-piercing rivet with which a connection between at least two components that are arranged one upon the other in a stack-like manner and are not pre-punched is establishable and which comprises the following features: a. a rivet head that is closed in axial direction, a rivet shaft extending from same, a rivet foot geometry at the end of the rivet shaft which faces away from the rivet head and an overall length L of the semi-hollow self-piercing rivet in the range from 7 mmL16 mm, b. the rivet head has a head diameter D.sub.K in a range from 7.5 mmD.sub.K7.9 mm, the form of a countersunk head with when viewed in axial cross section radially outside and starting in axial direction a cylindrical section, a truncated cone like section following the cylindrical section and an arc-like section tangentially transitioning into the rivet shaft and following the cone like section, c. the rivet shaft has a hollow cylindrical form with an outer shaft diameter D.sub.S in the range from 5.2 mmD.sub.S5.6 mm, a bore hole diameter D.sub.B in the range from 3.1 mmD.sub.B3.5 mm so that a relation of the bore hole diameter D.sub.S to the head diameter D.sub.K in the range from 0.39D.sub.B/D.sub.K0.5 arises, and with a bore hole depth T.sub.B in the range from 6 mmT.sub.B15 mm so that a bore hole volume V.sub.B in the rivet shaft depending on the overall length L of the semi-hollow self-piercing rivet in the range from V.sub.B minV.sub.BV.sub.B max with V.sub.B min=7.3 [mm.sup.2].Math.L [mm] and V.sub.B max=9.0 [mm.sup.2].Math.L [mm] arises, d. in an axial sectional view, the rivet foot has a conical radial outer chamfer as well as a conical inner chamfer interconnected by means of a cutting edge, with the conical inner chamfer tangentially transitioning into a radially inner bore wall of the shaft via a circular arc section and the outer chamfer as well as the inner chamfer enclose a cutting angle W.sub.S in the range from 80W.sub.S90.

2. The semi-hollow self-piercing rivet according to claim 1, wherein the conical radial outer chamfer has an outer chamfer height H.sub.S as a function of the overall length L of the semi-hollow self-piercing rivet according to H.sub.S0.032.Math.L [mm].

3. The semi-hollow self-piercing rivet according to claim 2, wherein the conical radial outer chamfer has an outer chamfer width B.sub.S in the range from 0.15 mmB.sub.S0.35 mm.

4. The semi-hollow self-piercing rivet according to claim 3, wherein the circular arc section axially following the conical radial inner chamfer comprises an entry radius R.sub.S into the shaft bore hole of 0.2 mmR.sub.S1.1 mm.

5. The semi-hollow self-piercing rivet according to claim 4, wherein the outer chamfer height H.sub.S in relation to the entry radius R.sub.S lies in a range from 0.2H.sub.S/R.sub.S1.2.

6. The semi-hollow self-piercing rivet according to claim 1, wherein a relation of shaft diameter D.sub.S to head diameter D.sub.K lies in the range from 0.5D.sub.S/D.sub.K0.75.

7. The semi-hollow self-piercing rivet according to claim 1, wherein the rivet head which is closed in axial direction has an axial head thickness H.sub.K1 depending on the overall length L of the semi-hollow self-piercing rivet according to H.sub.K1=0.1.Math.L0.1 mm.

8. The semi-hollow self-piercing rivet according to claim 1, having an overall length L in the range from 10.5 mmL16 mm.

9. A connection of at least two metal components that are arranged stack-like one upon the other and which are connected with each other with the help of the semi-hollow self-piercing rivet according to claim 1.

10. A manufacturing method of a semi-hollow self-piercing rivet which comprises the following steps: a. providing a wire section and b. cold forming a semi-hollow self-piercing rivet with the features of claim 1.

11. The manufacturing method according to claim 10 with the further step: c. applying a corrosion protection layer onto the cold formed semi-hollow self-piercing rivet.

12. The manufacturing method according to claim 10 with the further step: d. applying a liquid coating to reduce a friction coefficient of a surface of the semi-hollow self-piercing rivet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The embodiments of the present disclosure are described in more detail based on the accompanying drawings. They show:

[0041] FIG. 1 a schematic sectional view of an embodiment of the semi-hollow self-piercing rivet,

[0042] FIG. 2 a further schematic sectional view of a further embodiment of the semi-hollow self-piercing rivet with dimensioning,

[0043] FIG. 3 a schematic illustration of a connection of at least two components arranged one upon the other with the help of the semi-hollow self-piercing rivet, and

[0044] FIG. 4 a flow chart of a further embodiment of a manufacturing method of the semi-hollow self-piercing rivet.

DETAILED DESCRIPTION

[0045] FIG. 1 shows a schematic illustration of an embodiment of the semi-hollow self-piercing rivet 1. At least two sheet layers which are arranged upon one another may be connected with the help of the semi-hollow self-piercing rivet 1. Such a connection between the components B with the help of the semi-hollow self-piercing rivet 1 is shown in FIG. 3. According to a further embodiment, at least one component B may be made of aluminum or an aluminum alloy.

[0046] The semi-hollow self-piercing rivet 1 comprises a rivet head 10 which is closed in axial direction, a rivet shaft 30 extending from the rivet head 10 and a rivet foot 50 axially concluding the rivet shaft 30. The axial direction of the semi-hollow self-piercing rivet 1 is illustrated by means of the dashed central longitudinal axis 1 in FIG. 1.

[0047] Due to the axially closed rivet head 10, the established connection of the components B is protected against corrosion as neither pollution nor humidity can enter the rivet shaft 30.

[0048] The semi-hollow self-piercing rivet 1 has an overall length L in the range from 7 mmL16 mm.

[0049] The rivet head 10 has a head diameter D.sub.K in a range from 7.5 mmD.sub.K7.9 mm.

[0050] Furthermore, the rivet head has the form of a countersunk head. In a joining direction R.sub.F, viewed in an axial cross section of FIG. 1, the countersunk head is comprised of the following sections. At the end of the semi-hollow self-piercing rivet 1 which faces away from the rivet foot 50, the rivet head 10 has a cylindrical section 12 with a cylindrical lateral surface. This cylindrical section 12 is followed by a conical section 14 in joining direction R.sub.F. The conical section 14 may enclose a cone angle K in a range from 120K160.

[0051] The conical section 14 tangentially transitions in an arc like section 16 into a radially outer lateral surface 32 of the rivet shaft 30.

[0052] A summarized axial extension H.sub.K2 of the three sections cylindrical section 12, conical section 14 and arc like section 16 may be smaller than an axial head thickness H.sub.K1, which may be a minimum axial head thickness H.sub.K1.

[0053] The minimum axial head thickness H.sub.K1 is the difference of the overall length L of the semi-hollow self-piercing rivet 1 and a bore hole depth T.sub.B of a central shaft bore hole 34.

[0054] A reason for a larger minimum axial head thickness H.sub.K1 in comparison with the summarized axial extension H.sub.K2 is that otherwise, a material ingress could arise in a radially outer portion of the bore hole bottom of the central shaft bore hole 34 during cold molding or cold forming the semi-hollow self-piercing rivet 1 out of a wire blank. This would lead to a mechanical weakening of the semi-hollow self-piercing rivet 1.

[0055] According to a further embodiment of the semi-hollow self-piercing rivet 1, the closed rivet head 10 has the axial head thickness H.sub.K1 depending on the overall length L of the semi-hollow self-piercing rivet 1 according to H.sub.K1=0.1.Math.L [mm]-0.1 mm. For the application of the mentioned equation, the overall length L is given in millimeter, as is shown in square brackets.

[0056] According to a further embodiment of the semi-hollow self-piercing rivet 1, the minimum axial head thickness H.sub.K1 lies in a range from 0.9 mmH.sub.K13.1 mm.

[0057] The rivet shaft 30 has the hollow-cylindrical shape which can be seen in the schematic sectional views of FIGS. 1 and 2. The hollow-cylindrical rivet shaft 30 has an outer diameter D.sub.S in the range from 5.2 mmD.sub.S5.6 mm.

[0058] The shaft bore hole 34 has a bore hole diameter D.sub.B in the range from 3.1 mmD.sub.B3.5 mm. Furthermore, the shaft bore hole 34 has a bore hole depth T.sub.B in a range from 6 mmT.sub.B15 mm. In this case, the bore hole depth T.sub.B may be measured along the central longitudinal axis 1. Thus, the semi-hollow self-piercing rivet 1 may have a relation of bore hole depth T.sub.B to the overall length L of the semi-hollow self-piercing rivet in the range from 0.7 to 0.95.

[0059] The main function of the deep bore hole is the material uptake of the displaced material from the components B. By means of a high material uptake, the necessary die volume is reduced and dies of a lower height can be used for the production of a punch rivet connection.

[0060] In addition, an insufficient material uptake of component material into the rivet bore hole 34 leads to an accumulation of component material in front of the rivet blade 52 during the joining process, which leads to deteriorated cutting properties of the rivet foot 50 (see below) and a potential clinching of blades.

[0061] Therefore, the semi-hollow self-piercing rivet 1 comprises a bore hole volume V.sub.B in the rivet shaft 30 depending on the overall length L of the semi-hollow self-piercing rivet 1 in the range from V.sub.BminV.sub.BV.sub.Bmax with V.sub.Bmin=7.3 mm.sup.2.Math.L [mm] and V.sub.Bmax=9.0 mm.sup.2.Math.L [mm].

[0062] In order to be able to take up sufficient material in the form of a punch slug within the bore hole 34 with the help of the available bore hole volume V.sub.B, the above-defined bore hole diameter D.sub.B of the shaft bore hole 34 is necessary. A specific wall thickness S.sub.W of the rivet shaft 30 is necessary so that during the joining process, the semi-hollow self-piercing rivet 1 cuts over a long period of time with its rivet foot 50 and does not deform too early. This wall thickness S.sub.W of the rivet shaft 30 arises from the equation S.sub.W= (D.sub.SD.sub.B), with the wall thickness S.sub.W which may lie in a range from 0.85 mmS.sub.W1.25 mm.

[0063] Tests have shown that it is advantageous when a quotient of bore hole diameter D.sub.B and diameter D.sub.K lies in a certain range. This range emphasizes a still sufficient head stability with the largest uptake volume of the shaft bore hole 34. Specifically, the relation of bore hole diameter D.sub.B and head diameter D.sub.K lies in a range of 0.39D.sub.B/D.sub.K0.5.

[0064] Furthermore, the range of the above relation equation emphasizes the correlation between firstly the energy effort for setting the semi-hollow self-piercing rivet 1, as the rivet shaft 30 with a shaft bore hole 34 of this diameter requires a high setting force or setting energy, respectively, for punching out the punch slug and for receiving the punch slug in the shaft bore hole 34.

[0065] The above relation equation emphasizes the correlation between secondly a controlled energy consumption during the setting process, because while the supply of the setting force and setting energy via a punch of a setting device starts the setting process, a countersunk head 10 which widens radially up to its head diameter may cause a conversion of the supplied setting energy into displacement energy of the component material of at least the cover sheet of the component stack. Thus, a determined head diameter D.sub.K may provide for a specific reduction of setting energy that is still present.

[0066] The above observations regarding energy during the joining process, i.e. the alternating relation between the setting energy supplied to the semi-hollow self-piercing rivet 1 and the energy consumption by geometry-caused features of the semi-hollow self-piercing rivet 1 may be also expressed by a relation of the shaft diameter D.sub.S to the head diameter D.sub.K. According to a further embodiment, 0.5D.sub.S/D.sub.K0.75 may apply.

[0067] The semi-hollow self-piercing rivet 1 furthermore comprises a rivet foot 50 with a specific rivet foot geometry, the details of which are shown in FIGS. 1 and 2.

[0068] A rivet blade or cutting blade 52 may be needed so that thick and/or multi-layered metal sheet combinations and the associated material combinations may be joined. The cutting blade 52 separates the component material, thereby generating a punch slug. Furthermore, the cutting blade 52 which is influenced by the directly adjacent further constructive features of the rivet foot 50 must be capable of preventing a clinching of blades due to the component material to be separated. For this purpose, it is necessary that the rivet foot geometry is sufficiently stable so that it does not deform too early. Furthermore, this stability guarantees that in joining direction, the rivet foot 50 enters up to the last material sheet of the components B to be connected with each other.

[0069] For achieving the above goals, the cutting edge 52 is formed by a conical radial outer chamfer 54 and a conical radial inner chamfer 56. The outer chamfer 54 and the inner chamfer 56 may be configured linearly directly adjacent to the cutting edge 52 in axial cross section of the semi-hollow self-piercing rivet 1 and enclose a cutting angle W.sub.S in the range from 80W.sub.S90.

[0070] The conical radial inner chamfer 56 transitions tangentially into a radial inner bore wall 36 of the rivet shaft 30 via a circular arc section 58.

[0071] The conical radial outer chamfer 54, which may form or constitutes an annular surface which surrounds the rivet shaft 30 in a closed manner generates a pressure that is directed to the radial inside on the rivet foot 50 and thus on the rivet shaft 30 during the joining process. This radially inwards directed pressure on the shaft wall 38 may counteract a radially outwards directed pressure of the punch slug which enters the rivet shaft 30. Thus, a specifically adjusted size of the surface of the conical radial outer chamfer 54 prevents the rivet shaft 30 from spreading open too early.

[0072] In order to control the surface of the conical radial outer chamfer 54, the outer chamfer 54 may include a outer chamfer height H.sub.S in axial cross section of the semi-hollow self-piercing rivet 1. According to FIG. 2, the outer chamfer height H.sub.S is measured parallel to the central longitudinal axis 1 of the semi-hollow self-piercing rivet 1. It is determined by the axial distance between the rivet blade 52 and the point where the conical outer chamfer 54 meets the radial outer lateral surface 32 of the rivet shaft 30.

[0073] The outer chamfer height H.sub.S may be determined depending on the overall length L of the semi-hollow self-piercing rivet 1 according to H.sub.S=0.032.Math.L [mm].

[0074] The surface of the outer chamfer 54 may be further determined by a radial outer chamfer width B.sub.S in a range from 0.15 mmB.sub.S0.35 mm.

[0075] As already mentioned above, the conical radial inner chamfer 56 tangentially transitions via a circular arc section 58 into the radial inner wall 36 of the shaft bore hole 34. The circular arc section 58 prevent the conical radial inner chamfer 56 and the radial inner wall 36 of the shaft bore hole 34 from forming an edge or an offset. In practice, it has been shown that the punch slug which rises in the shaft bore hole 34 tends to be blocked or impeded by such edges or offsets in the course of its rising movement.

[0076] According to a further embodiment, the circular arc section 58 may include a radius R.sub.S in a range from 0.2 mmR.sub.S1.1 mm. According to a further embodiment, the radius R.sub.S may lie in a range from 0.5 mmR.sub.S1 mm.

[0077] With this size and the course of the circular arc section 58, which are determined by the radius R.sub.S, a balanced relation between the mechanical load which spreads open the rivet shaft 30 by means of the rising slug and the radially inwards acting forces of the displaced component material on the conical radial outer chamfer 54 may be created.

[0078] According to the disclosure, the above-mentioned balanced relation may be defined in numbers by a quotient of the outer chamfer height H.sub.S and the entry radius R.sub.S. This quotient may lie in a range from 0.2H.sub.S/R.sub.S1.2.

[0079] The above-described geometrical features of the semi-hollow self-piercing rivet 1 may have an advantageous effect when the semi-hollow self-piercing rivet 1 has an overall length L of 10.5 mmL16 mm.

[0080] According to a further embodiment, a liquid coating may be applied on the semi-hollow self-piercing rivet 1 for reducing a friction coefficient of its surface. This coating may fulfil two functions. Firstly, a rising of the punch slug in the shaft bore hole 34 is facilitated due to this coating. As the coating also reduces the friction at the radial outer lateral surface 32 of the rivet shaft 30, necessary setting forces for the semi-hollow self-piercing rivet 1 can be reduced with the coating.

[0081] In contrast to this, a high friction at the surface of the semi-hollow self-piercing rivet and a slow rising of the punch slug would lead to a material accumulation in front of the cutting edge 52, to a clinching of blades at the rivet foot 50 and to a potentially early spreading of the rivet shaft 30 during the joining process.

[0082] The coating may be comprised of two components: a corrosion resistant basic coating and a topcoat for adjusting the friction properties. The basic coating can be applied galvanically or mechanically. The topcoat is applied as a dry gliding film by means of a liquid coating.

[0083] Furthermore, the present disclosure comprises the connection which is schematically shown in FIG. 3, of at least two components B that are arranged stack-like one upon the other. They are connected with one another by means of the semi-hollow self-piercing rivet 1 according to one of the above-described embodiments.

[0084] Furthermore, the present disclosure includes the manufacturing method of the semi-hollow self-piercing rivet 1 according to the flow chart in FIG. 4. It comprises the following steps: providing a wire section (S1), cold forming a semi-hollow self-piercing rivet with the features of at least one of the above-described configurations (step S2), optionally applying a corrosion protection layer on the cold-formed semi-hollow self-piercing rivet 1 (step S3) and/or applying a liquid coating for reducing a friction coefficient of a surface of the semi-hollow self-piercing rivet 1 (step S4).