EP2591866A1 - Method for manufacturing a rotationally symmetrical hollow part and hollow part produced according to the method - Google Patents

Abstract

The method involves heating a rod (1) made of solid material, to a forging temperature. The cross-wedge rolling of rod is performed using a cross wedge-rolling machine so as to form cross wedge-rolled structure whose outer region (4) is hardened and inner core (3) is weakened. The rotating mandrels (5,6) are inserted along the central axis of cross wedge-rolled structure to produce the through-hole (9).

Description

The invention relates to a method for producing a rotationally symmetrical hollow part, in particular shaft and a cross-wedge-rolled rotationally symmetrical hollow part.

The production of rotationally symmetrical hollow parts, which can also serve as a preform for further forming, for example. Settled waves, in particular transmission shafts by cross wedge rolling is increasingly common. It is carried out on flat baking or round baking machines. The cross-corrugated waves are solidified due to the rolling process in their outer area. The use of solid material results in a high weight, which is undesirable in particular in the application of such waves in the automotive industry. Gear shafts are therefore also made with swivel machines from hollow shafts consuming and welded or waves mechanically processed (deep hole drilled).

• Vorlegen von stangenförmigem Vollmaterial
• Erwärmen des Vollmaterials im wstl. auf Schmiedetemperatur;
• Querkeilwalzen des Vollmaterials unter Herstellung von Schwächungen im Kernbereich des Vollmaterials; und
• Einschieben mindestens eines Dorns im wesentlichen entlang der Mittelachse des querkeilgewalzten Vollmaterials unter Herstellung einer Durchgangsbohrung, durchgeführt wird.

From the DE 102006031564 A1 a method has become known in which for producing a hollow rotationally symmetric part

• Presentation of bar-shaped solid material
• Heating the solid material in the wstl. at forging temperature;
• Cross wedge rolling of the solid material to produce weakenings in the core area of the solid material; and
• Insertion of at least one mandrel substantially along the central axis of the cross-wedge-rolled solid material to produce a through-hole is performed.

However, the hollow parts thus produced, in particular shafts, still had the disadvantage that the inner bore had steps or helical threads, which came about through the use of the spinning mandrel. The reworking of the inner contour of the hollow waves is complex and also leads to weakening of the fiber flow of the shaft. A weakening of a wave It also means that more material is needed for the same strength - meaning a higher weight of the shaft. This is undesirable in view of the lightweight construction requirements. A non-circular inner contour also leads to significant problems when centering the shaft, elaborate reworking and prevents unproblematic running around.

It is an object of the invention to provide a method for producing a rotationally symmetrical hollow part, which produces such hollow parts with a smoother inner contour.

The object is achieved according to the invention by using rotating mandrels which can be driven accordingly and thus a relative movement between mandrel and solid material to be thorn is controlled so that the inner contour is substantially smooth and the wall thicknesses over the cross sections are substantially constant. Thus, a round running hollow part can be made which requires little or no balancing work.

Further, it also relates the invention to a cross-corrugated rotationally symmetric hollow part produced thereafter, in particular shaft, which may be a gear shaft, camshaft, drive shaft, output shaft, starter shaft, hollow shaft, camshaft or a preform for further formed parts.

The fact that now is weakened by the insertion of the driven rotating mandrels in weakened by the rolling inner area in which due to the flexing the crystal lattice of the forgeable material, a smoothed through hole can be achieved, thereby easily a rotationally symmetrical hollow part, such as hollow shaft, can be produced with high precision. This weakening of the rod core during cross wedge rolling is also known as the Mannesmann effect. Due to the high Outer rutting on the bar during cross-wedge rolling solidifies the outer layer of the bar-shaped material, thereby facilitating the widening of the walls. By inserting the at least one driven rotating mandrel high workpiece accuracy is achieved because the material remains molded by the outer molds, while the solidification occurring through the rolling leads to waves with corresponding load capacity.

The at least one mandrel can have any desired shape, such as a tooth form, a hexagon, a swirl profile, etc. It is also advantageous, if it is rounded in the front region, to achieve a smoother inner contour of the hollow part. A rotary drive for the mandrel, which is preferably controllable, is familiar to the person skilled in the art.

The method is thus feasible for high volumes in a simple manner, which is achieved due to the molding process practically final shape and the workpieces thus produced in wstl. do not need to be reworked and require little or no balancing work.

Both the workpiece itself can be achieved by saving material as well as in the production costs a significant savings - even by simplifying the complex balancing - which previously required elaborate post-processing steps necessary.

The hollow shaft reduces the weight of the conventional solid shaft but maintains its strength. By inserting a driven and controlled rotating mandrel, the material in the core is selectively displaced outward, with a high workpiece accuracy is obtained because the material is pressed against external molds.

It may be advantageous to have two controlled driven rotating mandrels be inserted along the end faces of the rod-like solid material. This shortens the path of a mandrel and achieves a longer cycle time. The mandrels are only inserted so far that they just do not touch. In the further course of a mandrel is moved back and pushed the second mandrel on an overlap area on.

Conveniently, the mandrels can be inserted simultaneously rotating by means of a rotary drive. But it is also possible that the mandrels are pushed in a time-shifted rotating.

A typical inventive shaft, which is used as a transmission main shaft, countershaft, has a diameter of about 30 to 200 mm, preferably from 60 to 150 mm - of course, diameter can be realized, which are above or below. The shaft advantageously consists of a ductile wrought alloy, such as a 16MnCrS4, 20MnCr5, 20MoCrS4 steel, an aluminum or magnesium alloy, precipitation hardened steels or all common steels, as known to those skilled in the art.

• Fig. 1 einen Querschnitt durch ein vorgelegtes stangenförmiges Vollmaterial
• Fig. 2 einen Querschnitt des querkeilgewalzten Vollmaterials beim Querkeilwalzen;
• Fig. 3 einen Querschnitt einer Welle beim Querkeilwalzen;
• Fig. 4 einen Querschnitt durch eine Welle mit zwei Sacklochbohrungen während des Einbringens der drehenden Dorne
• Fig. 5 einen Querschnitt durch eine Welle mit einer Durchgangsbohrung
• Fig. 6 eine schematische Ansicht eines Querschnitts durch eine Querkeilwalzmaschine; am Beispiel einer Flachbeckenmaschine mit Materialführung zur Lagesicherung für das Aufdornen;
• Fig. 7 schematisch eine Vorderansicht der Querkeilwalzmaschine der Fig. 6; und
• Fig. 8 eine schematische Darstellung eines Querkeilwalzschrittes, bei dem die Dorne rotierend in das Vollmaterial eingebracht sind

The invention will be explained in more detail with reference to an embodiment of a hollow shaft, to which it is by no means limited, as well as the accompanying drawings. It shows:

• Fig. 1 a cross section through a presented rod-shaped solid material
• Fig. 2 a cross section of the cross wedge-rolled solid material in cross wedge rolling;
• Fig. 3 a cross section of a shaft during cross wedge rolling;
• Fig. 4 a cross section through a shaft with two blind holes during insertion of the rotating mandrels
• Fig. 5 a cross section through a shaft with a through hole
• Fig. 6 a schematic view of a cross section through a cross wedge rolling machine; the example of a flat-bed machine with material guide for securing the position for thorns;
• Fig. 7 schematically a front view of the cross wedge rolling machine of Fig. 6 ; and
• Fig. 8 a schematic representation of a cross wedge rolling step, in which the mandrels are rotatingly introduced into the solid material

Fig. 1 shows a bar 1 of solid material which is heated to forging temperature. In Fig. 2 is shown schematically how it is transformed into a cross-corrugated shaft with different diameters. During rolling, the rod 1 is moved with high forces via tools 12, 14, so that the material solidifies in the outer region 4 and the core 3 becomes brittle and ruptures. The tool 12, 14 forms the exterior of the shaft 2 already close to the final shape.

Fig. 3 shows how from two end faces of the shaft 2, two driven rotating mandrels 5, 6 are inserted centrally into the shaft 2 along the weakened by the Mannesmann effect core 3 in the axial direction. The spines 5, 6 are advanced until shortly before the meeting. As a result, the shaft material is pressed to the outside against the moving tools 12, 14 and receives a precise outer contour.

Fig. 4 shows a cross section through the cross-rolled shaft 2 in the first form. On both end faces a blind hole 8, 8 has been generated by the mandrels.

Fig. 2 shows a cross section through a cross-rolled shaft 2, a through Overlay the insertion of the mandrels has 5, 6 produced final shape. In order to produce this through-hole, a mandrel 5, 6 is withdrawn from an overlapping area of the mandrel paths, while the corresponding other mandrel is rotated and inserted over the overlapping area, so that a smooth through-hole 9 is created. Thus, the through hole is smooth, in a further step, the through-hole generating mandrel 5 can be withdrawn again and the first retracted mandrel is moved over the overlap region.

Thus, a cross wedge-rolled hollow shaft is created and larger diameters are conceivable, depending on the size of the machine. Typical mass of the shaft are a diameter of 30 to 200 mm, preferably 60-150 mm. Ductile materials, such as forgeable wrought alloys, can be used as materials. The alloys are by no means limited to iron alloys - it is also possible to use corresponding non-ferrous alloys or alloys with a lower iron content, such as ductile aluminum, titanium or magnesium alloys.

In Fig. 6 a cross wedge rolling machine 10 is shown schematically for understanding the method. A rod 1 is held by opposite material supports 16, 18 like a cage together with two opposing outer tools 12, 14. The outer tools 12, 14 are arranged perpendicular to the material supports 16, 18. A tool 12 with the tool carrier 13 is arranged substantially stationary, while the second tool 14 moves with the tool carrier 15 and the material supports 16, 18 with the rolling rod material 1 up and down or in two linear directions back and forth. The workpiece is acted upon from both sides by the tools 12, 14 with very high forces, so that a cross-wedge-rolled shaft 2 is produced from the rod part 1.

By the forward movement of the tool 14 of the outer shell 4 of the shaft is solidified, while the negative relief of the tool 12, 14 as Positive shape transmits to the shaft 2 and the shaft core is weakened.

Fig. 7 schematically shows a side view of this cross wedge rolling machine 10, wherein a wedge-shaped tool 12 exerts forces on the shaft 2 and the shaft 2 is formed by a material support 16 and the tool 14.

The schematic representation of Fig. 8 a Querkeilwalzschritt, wherein the mandrels are rotatably introduced into the solid material and support the inner contour, while the outer Kontor of the tube is formed into a flange 20. The rotating mandrels, which have a round tip here, support the material during the flow into the flange 20 - the arrows represent the force of the mold on the material to be formed. It can be seen that the mandrels release the material during local pressure application by the mold supported to reduce unwanted flow of material into the bore. The excess material 22 achieved by forming is smoothed by pulling out the mandrels in the further process, thus obtaining a smooth inner bore.

While the invention has been described in detail with reference to preferred embodiments, it will be apparent to those skilled in the art that various alternatives and embodiments for carrying out the invention are possible within the scope of the claims.

LIST OF REFERENCE NUMBERS

1 :

rod-shaped solid material

2:

cross wedge rolled shaft

3:

core

4:

Outside

5:

Mandrel, driven in rotation

6:

Mandrel, driven in rotation

7:

blind

8th :

blind

9:

Through Hole

10:

Cross wedge rolling machine

12:

Tool

13:

tool carrier

14:

Tool

15:

tool carrier

16:

material Support

18:

material Support

20

Flange to 2

22

Material surplus in the hole

Claims (9)

Method for producing a rotationally symmetrical hollow part, in particular a shaft, with: - Presentation of rod-shaped solid material - Heating the solid material in wstl. at forging temperature; - Cross wedge rolling of the solid material to produce weakenings in the core region of the solid material; - Inserting at least one driven at a predetermined speed rotating mandrel substantially along the central axis of the cross-wedge-rolled solid material to produce a through hole. A method according to claim 1, characterized in that two rotating at a predetermined speed mandrels along the end faces of the rod-like solid material are inserted. A method according to claim 2, characterized in that the mandrels are inserted at the same time. A method according to claim 2, characterized in that the mandrels are inserted verschoben time. Cross wedge-rolled rotationally symmetrical hollow part, in particular shaft, produced according to one of the preceding claims, characterized in that it is a transmission shaft, camshaft, drive shaft, output shaft, starter shaft, hollow shaft, camshaft or a preform for further formed parts. Rotationally symmetrical hollow part, in particular shaft, according to claim 5, characterized in that it has a diameter of about 30 to 200 mm, preferably from 60 to 150 mm. Rotationally symmetrical hollow part, in particular shaft, according to claim 5, characterized in that it is made of a ductile wrought alloy. Rotationally symmetrical hollow part, in particular shaft, according to claim 5, characterized in that it is made of a 16MnCrS4, 20MnCr5, 20MoCrS4 steel. Rotationally symmetrical hollow part, in particular shaft, according to claim 5, characterized in that it is made of a non-ferrous alloy, aluminum alloy, titanium alloy, magnesium alloy.

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