Method for manufacturing a hollow shaft

Abstract

Method for producing a hollow shaft having at least one shoulder (7) from a tubular preform by means of flow forming, wherein the tubular preform (1) is arranged on a mandrel (2) with at least two sections (2a, 2b) having different outer diameters (D1, D2) during the entire forming process, wherein a first section (2a) has an outer diameter (D1) corresponding to the inner diameter (D1) of the tubular preform (1) and at least a second section (2b) has an outer diameter (D2) corresponding to the inner diameter (D2) of the at least one shoulder (7) of the hollow shaft to be produced, wherein the first section (2a) of the mandrel (2) is fixed at its free end (2c) during the entire forming process.wherein in a first forming step the tubular preform (1) is pressed radially against the first region (2a) of the mandrel (2) by means of a clamping device (4) and the tubular preform (1) is drawn towards its free end around the at least one second region (2b) of the mandrel (2) by means of a press rolling operation using at least one press rolling roller (5), forming a radial end face (6) and the at least one shaft shoulder (7), characterized in that in a second forming step along the longitudinal axis (L) of the tubular preform (1) a tubular preform (8) is pressed axially with its end face (9) against the radial end face (6) produced in the first forming step, the clamping device (4) is released and the still unformed region of the tubular preform (1) is stretched along the first region (2a) of the mandrel (2) by means of at least one press rolling roller (5).

Description

[0001] The invention relates to a method for producing a hollow shaft having at least one shaft shoulder from a tubular preform by means of flow-forming with the features of the preamble of patent claim 1.

[0002] Hollow shafts of this type are used, for example, as hollow rotor shafts in electrical machines. DE 10 2019 109 183 A1 discloses a method for producing a hollow shaft from a tubular preform by flow-forming. Both ends of the preform are each formed with at least one forming roll, and the preform is held in the central tube region by a workpiece holder throughout the entire manufacturing process until the finished hollow shaft is formed. However, this method is not suitable for producing a hollow shaft with only one shaft shoulder, in which the tubular body is to be formed over its entire length.

[0003] DE 196 20 812 A1 discloses a method having the features of the preamble of patent claim 1. DE 22 30 554 A discloses a method for producing a pivot housing in which pressure rollers are used to form a tube. DE 25 51 156 A1 discloses a method for producing hollow bodies with a circular cross-section using pressure rollers.

[0004] The object of the invention is to produce a hollow shaft having at least one shaft shoulder from a tubular preform in the simplest possible manner.

[0005] This object is achieved according to the invention in a method of the type described at the outset in that, in a second forming step along the longitudinal axis of the tubular preform, a tubular pre-former is pressed with its end face axially against the radial end face produced in the first forming step, the clamping means is released and the not yet formed region of the tubular preform is stretched along the first region of the stretching mandrel by means of at least one flow-forming roller.

[0006] According to the invention, the flow-forming process is performed in a single setup, meaning the tubular preform and mandrel do not need to be removed from this setup during the entire forming process. This makes the process very simple and time-saving. Furthermore, perfect concentricity of all forming areas is guaranteed. In principle, several shaft shoulders can be formed with diameters decreasing toward the free end.

[0007] Thus, in one embodiment, it is provided that a stretching mandrel is used which has at least two second regions with different outer diameters, wherein in the first forming step the tubular preform is drawn in towards its free end around the first second region of the stretching mandrel to form a first corrugated shoulder and around at least one second second region of the stretching mandrel to form at least one second corrugated shoulder.

[0008] Preferably, a stretching mandrel is used whose first region has a circumferential surface profile over at least part of its longitudinal extent. This makes it possible to roll a complementary contour, e.g., a toothing, into the first region of the hollow shaft on the inside without additional processing steps.

[0009] Additionally or alternatively, it may be provided that a stretching mandrel is used, at least one second region of which has a circumferential surface profile over at least part of its longitudinal extent. Accordingly, a complementary contour can also be rolled into the second region of the hollow shaft if necessary.

[0010] The hollow shaft can preferably be used as part of a rotor hollow shaft.

[0011] The invention is explained in more detail below with reference to the drawings, which show a longitudinal section through Fig. 1 a tubular preform, Fig. 2 a first forming step and in Fig. 3 a second forming step.

[0012] A tubular preform as a starting product for the process according to the invention is shown in Fig. 1 is generally designated 1. This tubular preform 1 can be, for example, a drawn or welded metal tube.

[0013] In order to produce a hollow shaft having at least one shaft shoulder from such a preform 1 by flow forming, the tubular preform 1 is arranged on a stretching mandrel 2 which, in the exemplary embodiment, has two regions with different outer diameters, namely a first region 2a with an outer diameter D1 corresponding to the inner diameter D1 of the tubular preform 1 and a second region with an inner diameter D2 which corresponds to the inner diameter of the shaft shoulder of the hollow shaft to be produced.

[0014] The first region 2a of the stretching mandrel 2 is fixed with its free end 2c in a chuck 3 of the forming machine (not shown in detail) during the entire forming process.

[0015] During the entire forming process until the hollow shaft is completed, the stretching mandrel 2 remains fixed with its free end 2c in the chuck 3. The tubular preform 1 also remains unchanged on the stretching mandrel 2 until the end of the forming process.

[0016] In a first forming step, the tubular preform 1 is pressed radially against the first region 2a of the stretching mandrel 2 by means of a clamping means 4 and is drawn in by flow-forming by means of at least one flow-forming roller 5 towards its free end around the second region 2a of the stretching mandrel 2, forming a radial end face 6 and a corrugated shoulder 7. The at least one flow-forming roller 5 rotates relative to the stretching mandrel 2 and the tubular preform 1 and is movable relative to the preform 1 along the longitudinal axis L of the preform 1. The axis of rotation of the flow-forming roller 5 is inclined relative to the longitudinal axis L.

[0017] In Fig. 2 already shows the retracted state.

[0018] After completion of the formation of the shaft shoulder 7, a second forming step ( Fig. 3) a tubular or pot-shaped preformer 8 enclosing the shaft shoulder 7 is pressed with its end face 9 along the longitudinal axis L of the tubular preform 1 and the stretching mandrel 2 axially against the radial end face 6 produced in the first forming step. Subsequently, the clamping device 4 is released and the not yet formed area of ​​the tubular preform 1 is stretched to the desired length along the first area 2a of the stretching mandrel 2 by means of at least one flow-forming roller 5. Fig. 3 a state in which this ironing process is not yet completed.

[0019] At the end of the ironing process, after the clamping device 4 has of course been removed from the path of movement of at least one flow-forming roller 5, the finished hollow shaft with a shaft shoulder 7 is available.

[0020] If an internal profile is to be formed into the hollow shaft, a stretching mandrel 2 is used, the first region 2a and / or the second region 2b of which has a circumferential surface profile over at least part of its longitudinal extent. During the flow-forming process, a complementary internal profile, e.g., an internal toothing, is created on the hollow shaft to be produced in a known manner.

[0021] The finished hollow shaft is preferably a part of a hollow rotor shaft of an electrical machine. This finished hollow rotor shaft of an electrical machine can, for example, be produced from two hollow shafts manufactured according to the method described above, by positioning the two hollow shafts end-on and welding them together. Other designs are also possible (e.g., a welded-on cover or other components). In principle, it is also possible to fix the hollow shaft manufactured in this way with its shaft shoulder and part of the first region in the chuck 3 and then to carry out the process with the tubular preform manufactured in this way from the front, so that the end product is then a hollow shaft having at least one shaft shoulder at both ends.Alternatively, the tubular preform 1 can also be a hollow shaft which has already been partially manufactured in another way and which can be fixed in a chuck of a flow-forming machine for carrying out the process. List of reference symbols: 1 Tubular preform 2 stretching mandrel 2a First area 2b Second area 2c Free end 3 chucks 4 clamping devices 5 pressure roller 6 Frontal surface 7 wave heel 8 pre-setters 9 Frontal surface D1 diameter D2 diameter L Longitudinal axis

Claims

[1] Method for producing a hollow shaft having at least one shaft shoulder (7) from a tubular preform by means of flow-forming, wherein the tubular preform (1) is arranged on a stretching mandrel (2) having at least two regions (2a, 2b) with different outer diameters (D1, D2) during the entire forming process, wherein a first region (2a) has an outer diameter (D1) corresponding to the inner diameter (D1) of the tubular preform (1) and at least a second region (2b) has an outer diameter (D2) corresponding to the inner diameter (D2) of the at least one shaft shoulder (7) of the hollow shaft to be produced, wherein the first region (2a) of the stretching mandrel (2) is fixed with its free end (2c) during the entire forming process,wherein in a first forming step, the tubular preform (1) is pressed radially against the first region (2a) of the stretching mandrel (2) by means of a clamping means (4) and by pressure-forming by means of at least one pressure-forming roller (5), the tubular preform (1) is drawn towards its free end around the at least one second region (2b) of the stretching mandrel (2) to form a radial end face (6) and the at least one wave shoulder (7), , characterized by that in a second forming step along the longitudinal axis (L) of the tubular preform (1) a tubular pre-former (8) is pressed with its end face (9) axially against the radial end face (6) produced in the first forming step, the clamping means (4) is released and the not yet formed region of the tubular preform (1) is stretched along the first region (2a) of the stretching mandrel (2) by means of at least one flow-forming roller (5). [2] Method according to claim 1, characterized bythat a stretching mandrel (2) is used which has at least two second regions with different outer diameters, wherein in the first forming step the tubular preform (1) is drawn in towards its free end around the first second region (2b) of the stretching mandrel (2) to form a first corrugated shoulder (7) and around at least one second second region (2b) of the stretching mandrel (2) to form at least one second corrugated shoulder. [3] Method according to claim 1 or 2, characterized by that a stretching mandrel (2) is used, the first region (2a) of which has a circumferential surface profiling over at least part of its longitudinal extent. [4] Method according to claim 1, 2 or 3, characterized by that a stretching mandrel (2) is used, at least one second region (2b) of which has a circumferential surface profiling at least over part of its longitudinal extent.

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