METHOD FOR THE CHIPLESS PRODUCTION OF A ROTATIONALLY SYMMETRICAL BODY FROM A SHEET METAL BLANK

Description

[0001] The invention relates to a method for the non-cutting production of a rotationally symmetrical body from a sheet metal blank, wherein the sheet metal blank is formed into a cup-shaped body by pressing or flow-forming around an inner mandrel and a hub-shaped projection projecting outwards from the bottom of the cup-shaped body is formed by pressing around a central insert.

[0002] Such a method is known from EP 0 725 693 B1. This well-known method, which has long been tried and tested in principle, is used to manufacture a gear part having a hub. First, a cup-shaped form is created from a sheet metal blank by pressing it around an internal mandrel. Then, the outer bent-over edge region of the sheet metal blank is held all the way around the tool by a clamping tool, i.e. the edge region of the sheet metal blank is fixed so that it cannot move outwards during the subsequent pressing process. The cup-shaped form held in this way in the edge region is then deformed by pressing it around a central tool pin to form a cylindrical projection protruding from the sheet metal blank. The cylindrical projection is then opened to accommodate a coaxial shaft.

[0003] This process already offers significant advantages over other methods, such as welding or forging. However, to hold the peripheral edge before forming the hub, a clamping tool is required that is circumferentially applied to the bent peripheral edge. This is both complex and can lead to unintentional deformation of the bent peripheral edge held or clamped in this way, thus preventing perfect concentricity of the peripheral edge area. This is generally acceptable in the manufacture of pulleys, but makes the known process unsuitable when exact concentricity of the forming areas is critical.

[0004] One component that requires such precise concentricity is, for example, a housing for a pressure accumulator in an automatic transmission (especially a dual-clutch transmission) or similar. In such a housing, it must be ensured that the generally cylindrical inner surface is precisely concentric over its entire length to ensure that the pressure piston guided within the housing is properly guided. Therefore, it has not been possible to manufacture pressure accumulators of this type using non-cutting flow forming. Instead, such pressure accumulator housings are currently generally manufactured by bulk forming followed by machining, which is correspondingly complex.

[0005] FR 2 559 078 A1 discloses a method for producing a rotationally symmetrical body, in which a container with a thickened base is used as the starting product. A hub-shaped projection protruding outward from the base of the pot-shaped container is formed onto this thickened base by pressing or flow-forming. This method is complex because the starting product requires a container with a thickened base, which can then be formed by flow-forming.

[0006] EP 1 108 483 A2 discloses a method for producing a pot-like structure, in which a hub is produced before the production of the pot-like shape.

[0007] The object of the invention is to improve the known method, in particular to simplify production and to ensure perfect concentricity of the forming areas.

[0008] This object is achieved in a method according to claim 1 in that the sheet metal blank is clamped in the axial direction only in its radial inner region between the inner mandrel and at least one pre-setter during the entire forming process, wherein the sheet metal blank is initially held between an outer pre-setter surrounding the central pre-setter and the inner mandrel and in a first pressing process the sheet metal blank is formed into a cup-shaped preform, wherein subsequently, in order to form the hub-shaped projection, the central pre-setter is moved axially in the direction of the inner mandrel in order to clamp the sheet metal blank in its radial inner region against the inner mandrel, and subsequently the outer pre-setter is moved axially outwards away from the inner mandrel and then the hub-shaped projection is formed around the central pre-setter.

[0009] According to the invention, the process is thus carried out in a single setup, and the sheet metal blank is only held or clamped in its radial inner region; a rotating clamping tool and clamping of the outer edge region are completely eliminated. This significantly simplifies the process, and also eliminates any unwanted deformation of the already formed peripheral edge. It is essential that, starting from the sheet metal blank, the hub is not formed first, followed by the cup-shaped region, because otherwise, as has been found, material in the hub region will crack. Since the sheet metal blank is only clamped in its radial inner region, and the sheet metal blank is formed exclusively by pressing or flow-forming, perfect concentricity of all forming regions is guaranteed. The process is therefore also suitable for the production of components where exact concentricity is important, e.g.for the production of housings for pressure accumulators. Machining of the component is also not required.

[0010] In a first embodiment, it is preferably provided that the cup-shaped preform is first formed into a cup-shaped final shape by pressure rolling and then the hub-shaped projection is formed.

[0011] Alternatively, it can preferably be provided that after formation of the cup-shaped preform, the hub-shaped projection is formed by pressing and then the cup-shaped preform is formed into a cup-shaped final shape by pressure rolling.

[0012] The process can generally be carried out using a flat sheet metal blank. However, one embodiment provides for the sheet metal blank to be provided with a beveled peripheral edge before the cup-shaped preform is pressed. This can be achieved, for example, by deep drawing or another suitable forming process.

[0013] It can be particularly preferably provided that the sheet metal blank is provided with a central bore before the cup-shaped preform is pressed.

[0014] Depending on the material selection and the component to be formed, it may also be preferable for the sheet metal blank to be preheated, e.g. by induction, before and / or during pressing or flow-forming.

[0015] The cup-shaped end shape can be cylindrical or conical.

[0016] It may also be advantageous to use an inner mandrel with longitudinal grooves. This automatically creates ridges and grooves on the inner circumference of the component.

[0017] Furthermore, it can also be advantageous to use a central adapter with a surface profile. The inner area of the pushed-on hub can then have different geometric shapes, e.g., a hexagon socket, Torx profile, or the like. This can be easily achieved by appropriately profiling the surface of the central adapter.

[0018] The invention is explained in more detail below with reference to the drawings, which show a longitudinal section through Fig. 1 shows a sheet metal blank held in a spinning / forming device before the start of the forming process, Fig. 2 shows the deformation of the sheet metal blank into a cup-shaped preform by spinning, Fig. 3 shows the deformation of the sheet metal blank into a cup-shaped final shape by spinning, and Fig. 4 shows the formation of a hub-shaped projection by spinning.

[0019] A spinning / forming device, generally designated 1, is shown in the drawings only with elements essential to the invention. The spinning / forming device 1 is designed rotationally symmetrically to a longitudinal axis A and has a substantially cylindrical inner mandrel 2. A pre-setter is arranged opposite the front end 2a of the inner mandrel 2. In the exemplary embodiment, this pre-setter is constructed in two parts, namely a central pre-setter 3 and an outer annular pre-setter 4 surrounding the central pre-setter 3. Both the central pre-setter 3 and the outer pre-setter 4 are designed to be movable in both directions in the axial direction.

[0020] Furthermore, the spinning / forming device 1 has spinning rollers 5, 6, and 7, whereby a plurality of spinning rollers 5, 6, 7 can also be provided distributed around the circumference. The spinning rollers 5, 6, 7 are arranged in a known manner so as to be relatively rotatable in the circumferential direction relative to the pre-setters 3 and 4 and the inner mandrel 2, whereby the angular position and the geometric shape of the respective spinning roller 5, 6, 7 are adapted to the respective desired pressure-rolling process, i.e., the desired shape and dimensions of the rotationally symmetrical body to be produced.

[0021] To carry out the method according to the invention, a sheet metal blank 8 according to Figure 1clamped between the outer pre-setter 4 and the end face 2a of the inner mandrel 2 by pressing the outer pre-setter 4 in the axial direction against the sheet metal blank 8 and thus the inner mandrel 2. Subsequently, the spinning roller 5 (or several spinning rollers 5) are set in rotation relative to the sheet metal blank 8 and thus the pre-setter 4 and the inner mandrel 2, while at the same time the spinning roller 8 is moved in the direction of arrow 9. As a result, a cup-shaped preform 10 is formed from the sheet metal blank 8, which has an axially extended region 10a on the outer circumference. The sheet metal blank 8 is clearly held or clamped between the inner mandrel 2 and the outer pre-setter 4 only in its radial inner region.

[0022] Subsequently, the cup-shaped preform 10 is formed into a cup-shaped final shape 11 using a second spinning roller 6 (or several spinning rollers 6), in that the spinning rollers 6 are moved axially in the direction of the arrow 12 with simultaneous relative rotational movement with respect to the outer pre-setter 4 and the inner mandrel 2; this cup-shaped final shape 11 has a significantly longer axially extended circumferential region 11b than the cup-shaped preform 10.

[0023] Subsequently, the central pre-setter 3 is moved axially in the direction of arrow 13 toward the inner mandrel 2 and clamps the cup-shaped final shape 11 in its radial inner region against the inner mandrel 2. Subsequently, the outer pre-setter 4 is moved axially outward in the direction of arrow 14, to such an extent that one or more spinning rollers 7 can be moved radially inward in the direction of arrow 14. By simultaneous rotation of the spinning roller 7, a hub-shaped projection 16 is formed around the central pre-setter 3 onto the thus completed rotationally symmetrical body 16.

[0024] It can be seen that during the entire process sequence, the sheet metal blank 8 or the resulting cup-shaped preform 10, the cup-shaped final shape 11 and the final product, namely the rotationally symmetrical body 17, are held only in the radial inner area between the inner mandrel 2 and the central pre-setter 3 or the outer pre-setter 4.

[0025] The procedure can also be modified so that the sequence of Figures 3 and 4 is reversed, ie after formation of the cup-shaped preform 10, in the sense of Figure 4 the hub-shaped projection 15 is formed and then in the sense of Figure 3 the cup-shaped final shape 11 is produced.

[0026] Instead of a flat sheet metal blank 8, a sheet metal blank with a beveled peripheral edge can also be used as the starting product for the process. Furthermore, the sheet metal blank 8 can also be provided with a central hole before the cup-shaped preform is pressed.

[0027] In addition, it can be provided that the sheet metal blank 8 is preheated before and / or during pressing or flow-forming. List of reference symbols

[0028] ALongitudinal axis 1Spinning / forming device 2Inner mandrel 2aFront end 3Central pre-setter 4Outer pre-setter 5,6,7Spinning rollers 8Sheet metal blank 9Arrow 10Cup-shaped preform 10Aaxially extended area 11Cup-shaped final form 11Aaxially extended area 12Arrow 13Arrow 14Arrow 15Arrow 16Hub-shaped projection 17Rotationally symmetrical body

Claims

1. Method for the chipless production of a rotationally symmetrical body (17) from a sheet metal blank (8), wherein the sheet metal blank (8) is formed into a pot-shaped body by pressing or flow-forming around an inner mandrel (2) and a hub-shaped projection (16) projecting outwards from the base of the pot-shaped body is molded on by pressing around a central pre-setter (3), characterized in that during the entire forming process the sheet metal blank (8) is clamped in the axial direction only in its radially inner region between the inner mandrel (2) and at least one pre-setter (3, 4), wherein the sheet metal blank (8) is initially held between an outer pre-setter (4) surrounding the central pre-setter (3) and the inner mandrel (2), and in a first pressing process the sheet metal blank (8) is formed into a pot-shaped premold (10), wherein subsequently in order to form the hub-shaped projection (16) the central pre-setter (3) is moved axially in the direction of the inner mandrel (2), in order to clamp the sheet metal blank (8) in its radially inner region against the inner mandrel (2), and subsequently, the outer pre-setter is moved axially outwards away from the inner mandrel (2) and subsequently the hub-shaped projection (16) is molded around the central pre-setter (3).

2. Method according to claim 1, characterized in that the pot-shaped preform (10) is initially formed into a pot-shaped final mold (11) and then the hub-like projection (16) is molded on.

3. Method according to claim 1, characterized in that the pot-shaped preform (10) is then formed into a pot-shaped final mold (11).

4. Method according to any one of claims 1 to 3, characterized in that before pressing the pot-shaped preform (10) the sheet metal blank (8) is provided with a beveled peripheral edge.

5. Method according to any one of claims 1 to 4, characterized in that before the pot-shaped preform (10) is pressed the sheet metal blank (8) is provided with central bore.

6. Method according to any one of claims 1 to 5, characterized in that the sheet metal blank (8) is preheated before and / or during the pressing or flow-forming.

7. Method according to any one of claims 1 to 6, characterized in that an inner mandrel (2) with longitudinal grooves is used.

8. Method according to any one of claims 1 to 7, characterized in that a central pre-setter (3) is used with a surface profiling.