DE102013226929A1 - Method and device for producing a hollow shaft by radial forming and hollow shaft produced therewith - Google Patents

Abstract

The invention relates to a method for the forming production of a hollow shaft, which has a bore with a plurality of bore sections differing in cross-section, with:
- Providing a rotationally symmetrical preform (100 ') with an inner bore (110');
- Heating the preform (100 '); and
- Radial forming of the heated preform (100 ') for the simultaneous production of an outer mold and a bore inner mold, wherein the bore inner mold by means of at least one multi-functional mandrel (410) having a plurality of different in cross section mandrel portions (411, 412, 413) is generated.
The invention further relates to a device (400) for producing such a hollow shaft, and to a hollow shaft produced by the method according to the invention and / or the device (400) according to the invention.

Description

The invention relates to a method and an apparatus for the forming production of a hollow shaft having a plurality of different in cross section bore sections. The invention further relates to a corresponding hollow shaft.

Hollow shafts of the type mentioned are further processed in particular to transmission shafts for vehicle transmission.

In the DE 10 2008 036 226 A1 discloses a method for producing a hollow shaft of semi-finished products with a sequence of process steps, which makes it possible to optimally manufacture a hollow shaft in a large-scale production both in terms of production time, material and resource use and investment. The method comprises the steps of: forming a preform by forging; Performing a heat treatment of the preform; Forming the preform in an at least partially hollow intermediate form by Bohrungsdrücken; and swaging the intermediate shape to form a hollow shaft with a substantially uniform in the course of the hollow shaft wall thickness.

The invention had the object of providing a further advantageous procedure for producing a hollow shaft of the type mentioned above.

This object is achieved by an inventive method having the features of claim 1. With a sibling claim, the solution of the problem extends to a device according to the invention. With a further independent claim, the solution of the problem further extends to a hollow shaft produced by the method according to the invention and / or with the device according to the invention. Preferred developments and refinements are analogous to all subjects of the invention both from the dependent claims and from the following explanations.

To understand the invention is expressly also to the explanations in the DE 10 2008 036 226 A1 the same applicant.

• – Bereitstellen eines rotationssymmetrischen Vorformlings mit einer Innenbohrung;
• – Erwärmen des Vorformlings; und
• – Radialumformen des erwärmten Vorformlings zur gleichzeitigen Erzeugung einer Außenform und einer Bohrungsinnenform, wobei die Bohrungsinnenform mit Hilfe wenigstens eines Multifunktionsdorns, der mehrere sich im Querschnitt unterscheidende Dornabschnitte aufweist, erzeugt wird.

The inventive method for the forming production of a hollow shaft, which has a bore with a plurality of bore sections which differ in cross section (ie in cross-sectional size and / or shape), comprises at least the following method steps:

• - Providing a rotationally symmetrical preform with an inner bore;
• - heating the preform; and
• - Radial forming of the heated preform for simultaneously producing an outer mold and a bore inner mold, wherein the bore inner mold with the aid of at least one multi-function mandrel having a plurality of different in cross section mandrel portions, is generated.

Radial forming performed on a radial forming machine is an incremental forming process similar to rotary swaging. In this case, the workpiece having an inner bore is plastically deformed with a plurality of, and in particular four pulsating pressure rams or radial hammers, which displace the workpiece synchronously with radial impacts, wherein the workpiece rotates together with an inner mandrel relative to the hammers. The material is in the radial direction on the inner bore located in the inner mandrel, which is formed according to the invention as a multi-functional mandrel, and is thereby deformed in the axial direction of the inner mandrel or multifunction mandrel, so that the material flows defined in at least one axial direction along the multi-function mandrel , This results in an axial elongation of the workpiece, so that the finished shaped hollow shaft has a substantially greater axial length than the preform. In particular, the aspect ratio is> 2 (greater than two), d. H. the preform is elongated during radial forming at least 2 times and in particular at least 2.5 or 3 times in the axial direction. The main deformation direction is usually the axial direction, with high degrees of strain being achieved, for example, Phi> 3 (greater than three). Preferably, it is provided that the preform is elongated during radial forming in both axial directions, d. H. undergoes a deformation induced axial length change.

The hollow shaft to be produced has a plurality of bore sections which differ in their cross sections, with which axial sections lying one behind the other in the axial direction of the hollow shaft are meant. The individual axial sections fulfill different functions, as explained in more detail below. According to the invention, the internal bore shape of the hollow shaft is produced with the aid of at least one multifunction mandrel which has a plurality of mandrel sections differing in cross section. The mandrel sections are axial sections that lie one behind the other in the axial direction of the multifunction mandrel. With the aid of a multifunctional mandrel, in particular in a forming process, a plurality of bore sections differing in cross-section can be produced, wherein the respective outer shape of a mandrel section predetermines the generating internal shape of a bore section. The Mandrel sections thus function as functional units for the design of the bore inner contour or contour. According to the invention, it is also possible to use a plurality of internal mandrels, including conventional ones.

The production according to the invention of a hollow shaft takes place by deformation and thus without cutting. Nevertheless, the reshaping production can be followed by machining operations. Preferably, the hollow shaft produced according to the invention is subsequently further processed to form a gear shaft for a motor vehicle gearbox (for example, longitudinal or transverse gear). The hollow shaft or gear shaft preferably has an axial length of 150 mm to 600 mm.

The procedure according to the invention allows more freedom of design freedom than the previously known procedures. In addition, the hollow shaft can be made faster and with less device overhead. Further advantages of the invention, such as, for example, a favorable fiber flow on the hollow shaft produced, will be explained below.

The internal bore in the preform can be a through-hole or a blind hole. In particular, it is a circular cylindrical inner bore. It is preferably provided that the inner diameter of the inner bore in the preform corresponds to the maximum inner or bore diameter of the bore in the hollow shaft to be produced and / or that the outer diameter of the preform corresponds to the maximum outer diameter of the hollow shaft to be produced.

During radial forming, at least one bore section on the hollow shaft to be produced is preferably produced with internal toothing. The internal toothing is preferably a spline (or internal spline), the radially inwardly facing teeth are formed in particular with Einfädelfasen. The internal teeth and possibly the Einfädelfasen on the teeth are generated only by radial forming. For this purpose, the multi-functional mandrel has at least one corresponding mandrel section, which is formed with a corresponding toothing geometry (or toothed profile).

The temperature during radial forming is preferably at a medium temperature level, whereby heating energy can be saved. Preferably, the preform is heated to a temperature between 200 ° C and 800 ° C, preferably to a temperature between 200 ° C and 600 ° C and in particular to a temperature <600 ° C (below 600 ° C) before radial deformation and has at Radial forming a corresponding forming temperature, but gradually decreases in the course of the forming. Reheating is usually not provided.

Preferably, the preform has a simple geometric shape. The preform is preferably a turned part, a forged part or a cut-to-length piece of pipe, it being possible to provide such preforms cost-effectively. For example, preforms formed as forgings can be produced in large numbers piece by piece on a horizontal forging press. The material used is, for example, a case hardening steel. It is particularly preferably provided that the wall thickness or thickness of the preform formed with an internal bore is at least 10 mm, preferably at least 15 mm and in particular at least 20 mm, which requires a small axial length. Due to the short axial length, the inner bore can be inexpensively manufactured by simply drilling or punching. Furthermore, the preform may have compact dimensions.

• – mehrere Radialhämmer, die synchrone radiale Schläge auf den Vorformling aufbringen können; und
• – wenigstens einen Multifunktionsdorn, der mehrere und insbesondere wenigstens drei sich im Querschnitt unterscheidende Dornabschnitte aufweist.

Die erfindungsgemäße Vorrichtung ist insbesondere zur Herstellung einer Hohlwelle mit dem erfindungsgemäßen Verfahren geeignet. A device according to the invention for producing a hollow shaft, which has a bore with a plurality of bore sections differing in cross-section, by radial deformation of a heated preform, comprising:

• A plurality of radial hammers capable of applying synchronous radial impacts to the preform; and
• - At least one multi-functional mandrel having a plurality and in particular at least three different in cross section mandrel sections.

The device according to the invention is particularly suitable for producing a hollow shaft with the method according to the invention.

The device according to the invention may comprise further device components, such as a drive device for the rotary drive of the workpiece and the multifunction mandrel relative to the radial hammers, a drive device for bringing about a relative movement between the workpiece and the radial hammers, a control device, clamping means and the like.

The multifunction mandrel has a plurality of mandrel sections differing in cross section. The multifunction mandrel preferably has at least three differing mandrel sections. Preferably, at least one mandrel section for generating an internal toothing, in particular with Einfädelfasen, formed on the hollow shaft to be produced and has a corresponding tooth geometry, as already explained above. Of the Multifunction mandrel may have at least one mandrel portion for producing a lightweight rear section. Preferably, the multi-functional mandrel has a plurality of, in particular juxtaposed or axially one behind the other, mandrel sections for the production of lightweight undercuts, in particular with different bore diameters on. Preferably, the multifunction mandrel is formed from a steel and in particular a tool steel and has a polished surface.

• – die (definiert ausgebildeten) Wanddicken im Bereich von wenigstens zwei benachbarten Bohrungsabschnitten sind unterschiedlich, wodurch ein Wanddickensprung zwischen den betreffenden Bohrungsabschnitten besteht;
• – die (definiert ausgebildeten) Wanddicken im Bereich von wenigstens zwei benachbarten Bohrungsabschnitten sind identisch, so dass kein Wanddickensprung zwischen den betreffenden Bohrungsabschnitten besteht;
• – wenigstens ein Bohrungsabschnitt ist mit einer Innenverzahnung ausgebildet, wobei die Innenverzahnung durch Radialumformung erzeugt wurde;
• – wenigstens ein Bohrungsabschnitt ist als Leichtbauhinterschnitt ausgebildet, wie nachfolgend noch näher erläutert, wobei dieser Leichtbauhinterschnitt durch Radialumformung erzeugt wurde;
• – wenigstens ein Bohrungsabschnitt ist als Lagerstelle mit hoher Passungsgüte ausgebildet, wobei diese Lagerstelle durch Radialumformung erzeugt wurde und insbesondere nachbearbeitungsfrei ist;
• – die Außenform weist wenigstens einen massiven Bund auf, wie nachfolgend noch näher erläutert;
• – die Bohrung ist an einem axialen Ende verschlossen.

A hollow shaft produced with the method according to the invention and / or with the device according to the invention has a bore with several and in particular with at least three bore sections differing in cross section. Furthermore, the hollow shaft produced according to the invention may be characterized by at least two and preferably at least three or four of the following features:

• The (defined) wall thicknesses in the region of at least two adjacent bore sections are different, whereby there is a wall thickness jump between the respective bore sections;
• The (defined) wall thicknesses in the region of at least two adjacent bore sections are identical, so that there is no wall thickness jump between the respective bore sections;
• - At least one bore portion is formed with an internal toothing, wherein the internal toothing was generated by radial deformation;
• - At least one bore section is formed as a lightweight rear section, as explained in more detail below, this lightweight rear section was generated by radial deformation;
• - At least one bore portion is formed as a bearing with high quality of fit, this bearing was generated by radial deformation and in particular is post-processing free;
• - The outer shape has at least one solid collar, as explained in more detail below;
• - The hole is closed at one axial end.

• – wirtschaftliches Verfahren zur Herstellung einer einstückigen, gewichtsoptimierten und vorzugsweise auch belastungsoptimierten Hohlwelle;
• – Eignung zur Herstellung großer Stückzahlen (Großserienfertigung);
• – kurze Prozesskette und geringer Vorrichtungsaufwand;
• – hohes Leichtbaupotential für die herzustellende Hohlwelle wird geschaffen und genutzt;
• – kein Materialverlust beim Radialumformen und somit optimale Materialausbeute;
• – hohes Maß an Formhaltigkeit und nur geringe Fertigungstoleranzen (keine Rundlaufprobleme);
• – die Hohlwelle ist nach dem Radialumformen fertig geformt, weitere Umformschritte sind nicht erforderlich;
• – Nutzbarmachung von Freiheitsgraden und von potentiell hohen Umformgraden beim Radialumformen;
• – der Vorformling kann kostengünstig hergestellt und/oder bereitgestellt werden;
• – vorteiliger Materialfaserverlauf in der Hohlwelle und/oder hohe Oberflächengüte (kerben- und riefenfrei), wobei die Bohrungsinnenfläche ohne Nachbearbeitung, d. h. nachbearbeitungsfrei, verbleiben kann;
• – vergleichsweise geringer Energieeinsatz zum Herstellen der Hohlwelle und/oder hoher energetischer Wirkungsgrad der aufgewendeten Energie.

In summary, the invention provides the following advantages (no exhaustive list):

• - Economic process for producing a one-piece, weight-optimized and preferably also load-optimized hollow shaft;
• - Suitability for the production of large quantities (mass production);
• - short process chain and low device overhead;
• - High lightweight construction potential for the hollow shaft to be produced is created and used;
• - no loss of material during radial forming and thus optimal material yield;
• - high degree of dimensional stability and only low manufacturing tolerances (no concentricity problems);
• - The hollow shaft is finished after the radial forming, further forming steps are not required;
• - Utilization of degrees of freedom and potentially high degrees of deformation during radial forming;
• The preform can be produced and / or provided at low cost;
• - Advantageous material fiber flow in the hollow shaft and / or high surface quality (notch and scoring free), the bore inner surface without post-processing, ie post-processing, may remain;
• - Comparatively low energy consumption for producing the hollow shaft and / or high energy efficiency of the energy used.

The invention is explained in more detail below by way of example and not by way of limitation with reference to the schematic figures. The features shown in the figures and / or explained below may, regardless of specific feature combinations, be general features of the invention. The directions used refer to the representations shown in the figures. The features of the illustrated and / or illustrated embodiments are combined with one another within the scope of the invention.

1 shows in two sectional views of a preform and the hollow shaft produced therefrom.

2 shows in two sectional views of another preform and the hollow shaft produced therefrom.

3 illustrates in a sectional view the radial forming for producing a hollow shaft.

1 shows a cylindrical preform 100 , which is an internal bore 110 having. In the preform 100 it may, for example, be a separate piece of pipe or a machined turned part. From the preform 100 is by radial forming the hollow shaft shown 200 made a hole 210 with a plurality of bore sections differing in cross section 211 to 217 having. Transitions are provided between adjacent bore sections so that there are no abrupt cross-sectional changes. Both the preform 100 as well as the hollow shaft 200 are axially symmetrical with respect to the longitudinal or rotational axis L.

The hollow shaft 200 is subsequently further processed by machining to a gear shaft, including, for example, in the massive collar 201 On the outer circumference a running gear is milled. There may be several such massive bundles provided. At other axial points can be running gears or splines in the outer periphery of the hollow shaft 200 are milled. Due to the hollow design is the hollow shaft 200 or the gear shaft made therefrom relatively easy, but very resilient because of the reshaping production.

The bore of the hollow shaft 200 exemplifies seven axial bore sections 211 to 217 whose cross-sections differ in their cross-sectional size and shape. The individual bore sections 211 to 217 can be considered as separate functional units. In the left side bore section 213 it is a bearing, which is designed with a high degree of fit. Through the outer diameter larger bore sections 211 and 212 can in the bore section 213 a rolling bearing can be used. The serving as a bearing hole section 213 close to the right three larger diameter bore sections 214 . 215 and 216 at the bore section 213 have in the radial direction an undercut contour and serve as lightweight undercuts. The hollow shaft 200 Thus, several directly in the axial direction of successive functional units of the same kind, but different design, on. The bore section 216 closes to the right in the bore diameter smaller hole section 217 at the right end of the hole 210 forms. The left-side end of the hole 210 forming bore section 211 is formed with an internal spline. To the open end of the hole 210 are the teeth 218 the internal spline with Einfädelfasen 219 formed, as can be seen from the enlarged detail. The radially inward pointing teeth 218 are thus shaped sharpened in the axial direction to the left-side hole opening. The inner walls of the bore sections 211 and 213 represent functional surfaces.

In the 1 shown hollow shaft 200 points in the bore sections 211 to 217 different wall thicknesses or thicknesses, wherein the wall thickness within a bore portion may also vary (see, for example, bore sections 215 and 216 ). The wall thickness in adjacent bore sections may thus differ. Likewise, individual bore sections or even all bore sections can be formed with identical wall thickness. The respective wall thickness results, for example, by a compromise of required strength and desired lightweight construction, possibly also taking into account an advantageous mass distribution.

The hollow shaft 200 is starting from the preform 100 Radial forming by means of a multi-functional mandrel having a plurality of different in cross-section mandrel sections, prepared as described below with reference to 3 exemplified.

3 shows an already partially formed preform 100 ' (hereinafter also referred to as workpiece), in its inner bore 110 ' an axisymmetric multifunction mandrel 410 with several spine sections 411 . 412 , and 413 is plugged in. By means of radially effective hammers or radial hammers 420 becomes the material of the workpiece clamped in a workpiece holder (eg a chuck) 100 ' in the radial direction on the multifunction mandrel 410 shaped, with the workpiece 100 ' is only partially transformed at an axial point. The respective outer shape of the mandrel portion defines the inner shape of the bore portion to be created. By axial relative movement of the workpiece 100 ' (including multifunctional mandrel 410 ) to the hammers 420 is successively reshaped each axial point, wherein the material in the axial direction along the multi-function mandrel 410 defined flows. The material of the workpiece 100 ' When Radialumformen in the axial direction, so to speak, about the inner mandrel 410 drawn. The shown multifunctional mandrel 410 is in the spine section 412 formed with a Verzahnungsgeometrie for generating an internal spline. The multifunction mandrel is preferred 410 formed from a quenched steel material.

According to this procedure, the in 1 shown hollow shaft 200 prepared as follows. After a corresponding to the bore sections to be produced 214 . 215 . 216 and 217 trained multifunction mandrel in the inner bore 110 of the heated preform 100 was positioned (with a defined axial relative position) in a first forming process, the right of the solid collar 201 formed sections, wherein successively the outer contour and the inner contour of the hollow shaft to be produced 200 be generated simultaneously or at once. The respective inner contour is determined by the mandrel sections and the respective outer contour is determined by adjusting the radial hammer positions. Optionally, the hole can be closed by radial forming on the right side. Subsequently, the area is left of the massive fret 201 to the left-hand axial end of the bore portion 214 shaped. Thereafter, the multifunction mandrel is pulled out to the left out of the partially manufactured hollow shaft and through another multifunction mandrel, which corresponds to the bore sections to be produced 211 . 212 and 213 is formed, replaced and the partially manufactured hollow shaft is re-clamped. In a second forming process is now by forming the left of the massive collar 201 located portions of the hollow shaft 200 preformed, including a precisely shaped internal spline with Einfädelfasen in the bore section 211 ,

The method steps explained above are carried out automatically by the radial forming machine used. By manufacturing the design of the hollow shaft 200 if necessary, this can be produced with only one multifunctional mandrel. The inner surface of the hole 210 does not need to be post-processed after radial forming. This is especially true for the internal splines in the bore section 211 ,

As in 1 illustrated by dashed lines, the inner diameter of the inner bore corresponds 110 in the preform 100 the maximum bore diameter of the hole 210 in the bore section 214 the hollow shaft to be produced 200 and the outside diameter of the preform 100 corresponds to the outside diameter of the solid collar 201 on the hollow shaft to be produced 200 , Radial forming of the preform 100 is thus carried out in the reshaped sections on the outer circumference and / or on the inner circumference, a diameter reduction. In particular, it is envisaged that in the area of the massive federation 201 No radial deformation takes place on the outer circumference and on the inner circumference, and thus no reduction in diameter. The massive bunch 201 thus has the outside of the outer periphery of the preform 100 and inside the inner circumference of the inner bore 110 of the preform 100 ,

2 shows another preform 100a , which is formed T-shaped in the longitudinal section shown, and the hollow shaft made therefrom by radial forming using a multi-function mandrel 200a that a bore 210a with three bore sections 211 . 212a and 213a having. Starting from the particular provided as a forged preform 100a can the hollow shaft 200a in a forming process, analogous to the preceding explanations, be prepared with a multi-functional mandrel. The bore section 212a may deviate from the embodiment shown also be designed as lightweight rear section.

LIST OF REFERENCE NUMBERS

100

Preform (blank)

110

internal bore

200

hollow shaft

201

massive bundle (material accumulation)

210

drilling

211

Bore section (with splines)

212

bore section

213

bore section

214

bore section

215

bore section

216

bore section

217

bore section

218

Teeth (internal spline)

219

Einfädelfasen (sharpening)

400

Device for radial forming

410

Multifunction Dorn

411

core section

412

core section

413

core section

420

radial Hammers

L

Longitudinal axis (rotation axis)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008036226 A1 [0003, 0006]

Claims (10)

Method for the forming production of a hollow shaft ( 200 ), which has a bore ( 210 ) with a plurality of bore sections differing in cross section (US Pat. 211 - 217 ), comprising the following method steps: - providing a rotationally symmetrical preform ( 100 ) with an internal bore ( 110 ); - heating the preform ( 100 ); and - Radial forming of the heated preform ( 100 ) for the simultaneous production of an outer mold and a bore inner mold, wherein the bore inner mold by means of at least one multi-function mandrel ( 410 ), which has a plurality of mandrel sections ( 411 - 413 ) is generated. A method according to claim 1, characterized in that the inner diameter of the inner bore ( 110 ) in the preform ( 100 ) the maximum bore diameter of the bore ( 210 ) in the hollow shaft to be produced ( 200 ) and / or the outer diameter of the preform ( 100 ) the maximum outer diameter of the hollow shaft to be produced ( 200 ) corresponds. Method according to claim 1 or 2, characterized in that the preform ( 100 Radial forming at least twice in the axial direction (L) is elongated. Method according to one of the preceding claims, characterized in that the preform ( 100 ) is elongated during radial forming in both axial directions. Method according to one of the preceding claims, characterized in that during radial forming at least one bore section ( 211 ) is generated with an internal toothing. Method according to claim 5, characterized in that the teeth ( 218 ) of the internal toothing with Einfädelfasen ( 219 ) be formed. Method according to one of the preceding claims, characterized in that the preform ( 100 ) is heated to a temperature between 200 ° C and 800 ° C and in particular to a temperature between 200 ° C and 600 ° C before the radial forming. Method according to one of the preceding claims, characterized in that the preform ( 100 ) is a turned part, a forged part or a cut pipe section. Contraption ( 400 ) for producing a hollow shaft ( 200 ), which has a bore ( 210 ) with a plurality of bore sections differing in cross section (US Pat. 211 - 217 ) by radial forming a heated preform ( 100 ), comprising: - a plurality of radial hammers ( 420 ), the synchronous radial impacts on the preform ( 100 ) can muster; and at least one multifunctional mandrel ( 410 ), the plurality and in particular at least three different in cross-section mandrel sections ( 411 - 413 ) having. Hollow shaft ( 200 ), which has a bore ( 210 ) with a plurality of bore sections differing in cross section (US Pat. 211 - 217 ), this hollow shaft ( 200 ) with a method and / or with a device ( 400 ) according to one of the preceding claims and characterized by at least two of the following features: the wall thicknesses in the region of at least two adjacent bore sections ( 211 - 217 ) are different; The wall thicknesses in the region of at least two adjacent bore sections ( 211 - 217 ) are identical; At least one bore section ( 211 ) is formed with an internal toothing; At least one bore section ( 214 . 215 . 216 ) is designed as a lightweight rear section; At least one bore section ( 213 ) is designed as a bearing with high quality of fit; - the outer shape has at least one massive collar ( 201 ) on; - the hole ( 210 ) is closed at one axial end.

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