Method for Forming an End Part of a Tube, Respective Device for Performing the Method, Rolling Body, and Flange on an End Part of a Tube Formed with the Method

Abstract

A method for forming an end part of a tube, such as a hollow shaft for use as a vehicle axle, is described. A rolling body having a rolling surface with an inwardly-curved contour rotates around a longitudinal axis with a first rotational speed and a second rotational speed. The rolling body and the tube rotate in the same direction. The longitudinal axis of the rolling body is arranged eccentrically to a longitudinal axis of the tube by a predetermined normal distance. The rolling body and the tube are brought into contact such that the rolling surface contacts the end part of the tube at a contact surface situated on an inner tube wall. The rolling body transfers a force to the inner tube wall by a relative movement between the rolling body and the tube such that the end part of the tube is formed radially outward.

Claims

1. A method for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, wherein: a rolling body rotates around its longitudinal axis with a first rotational speed, wherein the rolling body is substantially cone shaped or truncated shaped, wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis, and wherein the contour of the rolling surface is at least sectionally curved inward, the tube rotates around its longitudinal axis with a second rotational speed, the rolling body and the tube rotate in the same direction, the longitudinal axis of the rolling body is arranged parallel to the longitudinal axis of the tube, the longitudinal axis of the rolling body is arranged eccentrically to the longitudinal axis of the tube by a predetermined normal distance, the rolling body and the tube are brought into contact such that the rolling surface of the rolling body contacts the tube in the end part region of the tube at a contact surface situated on an inner tube wall, wherein the first rotational speed and the second rotational speed are set such that the absolute value of the difference calculated from a circumferential speed of the rolling body minus a circumferential speed of the tube at the contact surface in relation to the circumferential speed of the rolling body is in the range of 0 to 10%, preferably 0 to 5%, more preferably 0 to 2%, and wherein the rolling body transmits a force to the inner tube wall of the tube in the region of the contact surface by a relative movement between the rolling body and the tube such that the end part of the tube is formed radially outward.

2. The method according to claim 1, characterized in that the force is not more than 500 kN, preferably in a range between 1 and 400 kN, preferably in a range between 5 and 300 kN, more preferably in a range between 10 and 250 kN.

3. The method according to claim 1, wherein when a projection of the contact surface and a projection of the rolling surface are on a plane perpendicular to the longitudinal axis of the rolling body, the projection of the contact surface is entirely enclosed in a circle sector of the projection of the rolling surface, and wherein the circle sector comprises an angle at center of not more than 240, preferably of not more than 180, preferably of not more than 150, more preferably of not more than 120.

4. The method according to claim 1, wherein the material of the end part of the tube abuts on an inner side of a circumferential collar on an outer circumference of the rolling body over a period of time during the forming from a first contact with the inner side.

5. The method according to claim 1, wherein the first rotational speed of the rolling body is between 300 to 1500 rpm, preferably between 450 to 1100 rpm, more preferably between 600 to 700 rpm.

6. The method according to claim 1, wherein the second rotational speed of the tube is between 300 to 1500 rpm, preferably between 450 to 1100 rpm, more preferably between 600 to 700 rpm.

7. The method according to claim 1, wherein the end part of the tube has a temperature between 700 to 1300 C., preferably between 1000 to 1250 C., more preferably between 1150 to 1200 C., at least during a time when the rolling body is in contact with an inner wall of the end part of the tube.

8. The method according to claim 1, wherein the rolling body has a temperature between 100 to 250 C., preferably between 140 to 210 C., more preferably between 150 to 200 C., at least during a time when the rolling body is in contact with an inner wall of the end part of the tube.

9. The method according to claim 1, wherein the tube is warm-upsetted before being formed by means of the rolling body.

10. The method according to claim 1, wherein after the forming by means of the rolling body, the upsetted end part of the tube is further formed by means of at least one pressure forming process.

11. A flange on an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, manufactured using the method according to claim 1.

12. The flange according to claim 11, wherein a ratio between an outer diameter of the formed end part of the tube to an outer diameter of a not formed portion of the tube exceeds 1.5:1, preferably exceeds 2:1, preferably exceeds 3:1, and more preferably exceeds 4:1.

13. The flange according to claim 11, wherein the formed end part of the tube has at least one portion with a wall thickness which is greater than a wall thickness of a not formed portion of the tube.

14. A device for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, preferably suitable for performing the method according to claim 1, wherein the device comprises: a rolling body with a longitudinal axis, wherein the rolling body is substantially cone shaped or truncated shaped, wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis, and wherein the contour of the rolling surface is at least sectionally curved inward; and a rotatable means for receiving and attaching the tube, wherein the longitudinal axis of the rolling body is arranged eccentrically to a longitudinal axis of the tube by a predetermined normal distance, and parallel to the longitudinal axis of the tube, when the tube is attached to the means.

15. The device according to claim 14, wherein the ratio of the normal distance to an outer diameter of the end part of the tube before said forming is in a range of 1:60 to 1:2, preferably 1:30 to 1:3, and more preferably 1:6 to 1:3.

16. The device according to claim 14, wherein the rolling body can be driven axially around its longitudinal axis, preferably by means of a drive shaft.

17. A rolling body for forming an end part of a tube, preferably of a hollow shaft suitable for use in a vehicle, especially a hollow axle shaft, preferably suitable for performing the method according to claim 1, wherein the rolling body is substantially cone shaped or truncated shaped, wherein the rolling body has a rotationally symmetrical rolling surface around its longitudinal axis, wherein the contour of the rolling surface is at least sectionally curved inward, wherein a circumferential collar is arranged at an outer circumference of the rolling body, and wherein the collar has a draft angle larger than 0, preferably larger than 1, and more preferably larger than 5.

18. The rolling body according to claim 17, wherein a tangent to a radially outward edge portion of the rolling surface and the longitudinal axis define an angle larger than 70 to 105, preferably larger than 75 to 100, and more preferably larger than 80 to 95.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above described features and functions of the present invention as well as further aspects and features are further explained in the following with a detailed description of preferred embodiments with reference to the attached figures.

[0044] FIGS. 1a to 1c are sectional views of rolling bodies according to the present invention;

[0045] FIG. 2 is a sectional view of a device for forming an end part of a tube according to the present invention;

[0046] FIGS. 3 to 5 are sectional views illustrating different points in time of a method for forming an end part of a tube;

[0047] FIGS. 6 and 7 are projections of a contact surface and a rolling surface on one plane; and

[0048] FIGS. 8 and 9 illustrate a device for performing a pressure forming process with a punch and a die.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] FIG. 1a illustrates a sectional view of a rolling body W according to the invention pursuant to an embodiment of a rolling body. The rolling body W is formed rotationally symmetrical around its longitudinal axis LW with a rolling surface WF for forming, in particular rolling, a workpiece. The rolling surface WF is formed with an inward curved shape and extends from a mandrel-like top S lying on the longitudinal axis LW in an inward curved manner radially to the outside. A tangent T located on an arbitrary point P of the rolling surface WF shown in FIG. 1 and the longitudinal axis LW define an angle . Due to the inward curved configuration of the rolling surface LW, the angle increases from the mandrel-like top S radially outward, such that arbitrary points P of the rolling surface WF include an angle larger than 0 to about 85. Viewed from a top S towards a base BA, it is the angle between the longitudinal axis LW and the tangent, which is spanned averted from the top S. A circumferential collar B on an outer circumference of the rolling body W is provided at an edge portion of the rolling surface WF, where the point P has the largest angle . The collar B is formed integrally with the rolling body W and comprises an inner side I with a draft angle of 5. The rolling body W comprises a not shown stem for receiving in a device.

[0050] FIG. 1b is a sectional view of another rolling body W according to the present invention. The rolling body W with a longitudinal axis LW has a different rolling surface WF compared to the rolling body W according to FIG. 1a. The rolling surface WF comprises three sections A.sub.1, A.sub.2, A.sub.3 with a different slope, in which the tangents T located on arbitrary points P in one respective section A.sub.1, A.sub.2, A.sub.3 of the rolling surface WF defines the same angle with the longitudinal axis LW. The angle of the tangents located on the points P in section A.sub.1 of the rolling surface WF is 45, the angle of the tangents located on the points P in section A.sub.2 of the rolling surface WF is 70, and the angle of the tangents located on the points P in section A.sub.3 of the rolling surface WF is 90. Viewed from a top S towards a base BA, it is the angle between the longitudinal axis LW and the tangent, which is spanned averted from the top S.

[0051] FIG. 1c is a sectional view of another rolling body W according to the present invention. The rolling body W with a longitudinal axis LW does not comprise a mandrel-like top S compared to the rolling body W according to FIG. 1a but a flattening AB so that the rolling body has a truncated shape. The flattening AB is not for forming an end part of a tube and does not constitute a part of the rolling surface WF. A passage between the flattening AB to the rolling surface WF is formed such that the angle of a tangent located at a point P to the longitudinal axis LW of the rolling surface WF is 45. Viewed from a flattening AB towards a base BA, it is the angle between the longitudinal axis LW and the tangent, which is spanned averted from the flattening AB.

[0052] FIG. 2 is a sectional view of a device according to the present invention for forming an end part of a tube R pursuant to an embodiment of such a device. With the device for forming an end part of a tube R, the rolling body W according to FIG. 1a is used.

[0053] The rolling body W which is attached to a drive shaft via a stem Z is rotationally driven by a first drive motor, not shown, with a first rotational speed D.sub.1. The drive shaft is moveable in the axial direction together with the rolling body W by means of a not shown feed motor, and for an accurate positioning transverse to the axial direction via a slide system consisting of several slides.

[0054] The tube R is attached in a rotatable means H for receiving and attaching the tube R. The tube R which is attached in the means H is rotationally driven by another not shown drive motor with a second rotational speed D.sub.2. For an accurate positioning transverse to the axial direction, the rotatable means H also has a not shown slide system consisting of a plurality of slides.

[0055] The rolling body W with its longitudinal axis LW and the tube R with its longitudinal axis LR are arranged parallel and eccentric to each other with a normal distance a in FIG. 2.

[0056] FIGS. 3 to 5 are sectional views showing different points in time and snap shots, respectively, of an method for forming an end part of a warm-upsetted tube R according to the present invention. The warm-upsetted tube R is made of steel and has an outer diameter of 115 mm and a wall thickness 1 of 18 mm. The normal distance a between the longitudinal axis LW of the rolling body W and the longitudinal axis LR of the warm-upsetted tube R is 15 mm. The first rotational speed D.sub.1 of the rolling body W and the second rotational speed D.sub.2 of the warm-upsetted tube R are set to 600 rpm during the whole forming process so that a circumferential speed U.sub.1 of the rolling body W and a circumferential speed U.sub.2 of the warm-upsetted tube R are the same. The warm-upsetted tube R is inductive heated up to 1150 C. and the rolling body W is inductive heated up to 150 C. for forming.

[0057] The warm-upsetted tube R with a first rotational speed D.sub.1 is moved in the axial direction to the rolling surface WF of the rolling body W with a second rotational speed D.sub.2. At the beginning of the forming by means of the rolling body W, the end part of the warm-upsetted tube R to be formed and the rolling surface WF contact each other at an inner edge IN of the end part of the warm-upsetted tube R so that in case of a three-dimensional view, a contact surface KF corresponds to a line running in the circumferential direction, and in case of a two-dimensional view, as shown in FIG. 3, corresponds to a point.

[0058] With a continuous movement of the warm-upsetted tube R in the axial direction towards the rolling surface WF of the rolling body W, as shown in FIG. 4, the material of the end part of the tube R is formed radial outward continuously along the contour of the rolling surface WF, that is, the material flows radial outward. Therefore, the contact surface KF at which the rolling surface WF of the rolling body W is in contact with a contacting machining surface BF of an inner tube wall RI of the warm-upsetted tube R increases, and in case of a three-dimensional view, is identifiable as a surface, and in case of a two-dimensional view, as illustrated in FIG. 4, as a line. The machining surface BF forms the entire surface to be machined during the forming, that is, an expanded inner side of the warm-upsetted tube R.

[0059] At the end of the forming process by means of the rolling body W, as shown in FIG. 5, the contact surface KF is maximal. Already shortly before this point in time, the end part of the warm-upsetted tube R abuts against the inner side I of the circumferential collar B on the outer circumference of the rolling body W, so that a thickening forms at the end part of the tube R. Near the end face, the formed end part has a thickness l.sub.1 greater than a thickness l.sub.2 of a not formed region of the warm-upsetted tube R and/or of a formed region of the tube R lying further at the center of the warm-upsetted tube R. The draft angle enables a separation of the warm-upsetted tube R from the rolling body W in an opposite axial direction or vice versa.

[0060] FIGS. 6 and 7 are projections of the contact surface KF and the rolling surface WF on a plane lying in the drawing layer at different points in time of the forming process. A hatched projection PK of the contact surface KF and a projection PW of the rolling surface WF are illustrated on a plane perpendicular to the longitudinal axis LW, wherein the projection PK of the contact surface KF is entirely enclosed in a circle sector of the projection PW of the rolling surface WF. The circle sector has an angle at center of 65 in FIG. 6, and in FIG. 7, the circle sector has an angle at center of 120. The projection PK of the contact surface KF illustrated in FIG. 6 approximately corresponds to the contact surface KF shown in FIG. 4. The projection PK of the contact surface KF illustrated in FIG. 7 approximately corresponds to the contact surface KF shown in FIG. 5.

[0061] As the hatched projection PK of the contact surface KF only takes a circle sector of the projection PW of the rolling surface WF, that is, does not extend around the entire circumference of the warm-upsetted tube R, less feed force (maximal 250 kN and 25 t, respectively) is required for forming the end part of the warm-upsetted tube R. Further, at the beginning of the forming process, the highest pressure is applied to the end part of the warm-upsetted tube R by the rolling body W with a constant feed force over the entire forming process as the contact surface is smallest at this point in time.

[0062] FIGS. 8 and 9 illustrate a device for performing a pressure forming process with a punch S and a die M. The end part of the warm-upsetted tube R is inserted as a blank into the die M and obtains its final shape by an interaction of the punch S and the die M, so that a flange is formed at a warm-upsetted tube R.

[0063] In addition to the explained embodiments, the present invention also allows further configuration approaches.

[0064] The rolling body W comprises three sections or portions with a different slope. However, the rolling surface of a rolling body according to the present invention may also be formed such that it comprises one, two, four, five or any number of rectilinear sections and/or one, two, three or any number of inward curved sections.

[0065] The above described rolling bodies comprise a not shown stem for receiving in a device; however, the rolling bodies may also be formed as shell tools.

[0066] The rolling body with the device for forming an end part of a tube R is not limited to the rolling body illustrated in FIGS. 2 to 5 but using other rolling bodies, such as the rolling body W according to FIG. 1b, or the rolling body W according to FIG. 1c et seq. is possible.

[0067] Although a warm-upsetted tube R with a wall thickness 1 of 18 mm is formed above, according to the invention, also tubes with a wall thickness between 5 mm to 100 mm, preferably between 10 mm to 80 mm, more preferably between 15 mm and 70 mm, can be formed.

[0068] Although the warm-upsetted tube R machined in the embodiment is made of steel, also tubes made of aluminum or an alloy of steel and/or aluminum can be formed.

[0069] Although not shown in FIGS. 8 and 9, openings, such as bores, threaded holes et seq., may be provided in the flange at the warm-upsetted tube R.