CN111842771B

CN111842771B - Method for producing a hollow shaft

Info

Publication number: CN111842771B
Application number: CN202010355348.8A
Authority: CN
Inventors: S.吕施; M.雅布隆基; G.吕尔斯
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2019-04-29
Filing date: 2020-04-29
Publication date: 2022-08-05
Anticipated expiration: 2040-04-29
Also published as: CN111842771A; DE102019111048A1

Abstract

The invention relates to a method for producing a hollow shaft having a first and a second axial section between which a radially outwardly projecting flange is arranged, comprising the steps of: providing a metal blank with an axial through hole; heating and clamping the blank into a radial forming machine; the blank is forged in a radial forming machine for establishing the first and second axial sections. The invention is characterized in that the first and second axial sections are built up in different radial forming steps, between which the partially machined blank is removed from the radial forming machine and is clamped back in the opposite axial orientation, wherein the heating of the blank is carried out selectively for each of the radial forming steps, in particular for the respective axial section to be built up, and directly before the respective clamping.

Description

Method for producing a hollow shaft

Technical Field

The invention relates to a method for producing a hollow shaft (Hohlwelle) having a first and a second axial section, between which a radially outwardly projecting flange is arranged, comprising the following steps:

-providing a metal blank with an axial through hole (Rohling),

heating and clamping the blank into a radial forming machine (radia lumeformamaschine),

radially shaping the blank in a radial shaping machine by forging technique for establishing the first and second axial sections.

Background

Such a method is known from document DE 102017212989 a 1.

The shaft is primarily used to transmit torque. Hollow shafts have a significantly lower weight with approximately the same strength as solid shafts and are therefore increasingly being used in automobile construction (so-called lightweight shafts). Flanged shafts, that is to say shafts, in particular hollow shafts (which have a flange projecting radially outward in the center, which divides the hollow shaft into two different axial sections), are used in particular as rotor shafts of electric machines, which are increasingly used as drive devices in the manufacture of motor vehicles. Such flanged hollow shafts are often joined from a plurality of individual pieces (Einzelteil). However, this is complicated and requires a particular precision of the individual parts to be joined. The joined flanged hollow shaft is therefore relatively expensive to manufacture.

The document of the type mentioned above discloses the production of a hollow flanged shaft as a pure molded part (Umformteil) from a metal blank. A hollow cylindrical element made of steel is provided as a blank, which is heated and clamped into a radial forming machine. The two ends of the blank are then extended by radial forging, which is to be done explicitly in one process step. An outwardly projecting flange is formed between two blank regions (i.e. axial sections of the hollow shaft) which extend in different directions. Such a production method is mechanically very complex, since the clamping tool for holding the blank and the forging tool for shaping it must be precisely coordinated with one another in terms of space and time and must be equipped with a complex kinematics (Motorik). Such radial forming machines are expensive and fragile.

Disclosure of Invention

The object of the invention is to improve a manufacturing method of this type such that it can be performed with a simpler and more durable radial forming machine.

This object is achieved in that the first and second axial sections are established in different radial forming steps, between which the partially processed blank is removed from the radial forming machine and is clamped back in the opposite axial orientation, wherein the heating of the blank is carried out for each of the radial forming steps, in particular (getondert), selectively for the respective axial section to be formed and directly before the respective clamping.

The invention combines various aspects which, in the interaction of their functions, lead to a particularly simple and efficient production method for flanged hollow shafts. According to a first aspect, the two axial sections are established on both sides of the flange to be constructed in different forming steps. This means that the respective regions of the (partially machined) blank which are not to be formed can be used for their reliable clamping. I.e. the molding is performed only in the free, non-sandwiched region (one side of which is extended). The method of forming such a side is well known to those skilled in the art.

In order to achieve the desired double-sided lengthening of the blank, according to a second aspect of the invention, the blank (partially machined on one side) is temporarily released and clamped back into the radial forming machine in the opposite axial direction, wherein the axial section established in the preceding forming step is now used as the clamping region for the clamping tool (einspan powerkzeug) of the radial forming machine.

This second aspect is problematic in that, however, the initially completely heated blank cools during the first forming step and the subsequent loosening and renewed clamping, so that the second axial section has to be built up at a lower forming temperature. A third aspect of the invention is prepared here, the heating of the blank according to which is carried out specifically for each of the two radial forming steps. In other words, the blank is not only heated before the first radial forming step but is also reheated before the second radial forming step.

The invention however also relates to a further, fourth aspect, according to which, in the two aforementioned heating steps, the blank does not have to be heated completely to a uniform processing temperature, but rather the heating is carried out selectively for each of the two axial sections to be produced, that is to say for each of the blank regions. In other words, only the region of the blank to be processed in the subsequent forming step is correspondingly heated completely to the necessary processing temperature, wherein the region serving as the clamped-in region in this forming step can be kept cooler. This region is heated to the processing temperature just before its "own" shaping step. This aspect on the one hand leads to particularly high energy efficiency and time saving. On the other hand, this measure also makes it possible to use clamping and clamping tools that are not resistant to high temperatures, since they are only in contact with the still cold or cooled region of the workpiece. This saves on costs of manufacture and maintenance of the radial forming machine.

This advantage works particularly strongly in the case of blanks held during clamping and heating by means of a gripper (Greifer) of a handling robot (handlabungsborber), as is customary in the modern automotive industry. The gripping jaws of a handling robot are delicate structures which can only be designed to withstand high temperatures with high additional effort. However, this additional expenditure is eliminated when using the method according to the invention.

The heating of the blank is preferably carried out outside the radial forming machine, i.e. in an unclamped state. For this purpose, an external induction furnace (industrissofen) can be used in particular. In the case of such a spatially separated arrangement of heating and machining, the use of a handling robot is particularly advantageous, whereby the effect of the invention, as explained above, works particularly well.

The advantages made possible by the method according to the invention are achieved by the (as preferably provided) gripping of the blank by the jaws outside the region in which the respective axial section is established in the respective subsequent radial forming step, that is to say the jaws preferably grip the blank at the respective cooler ends.

The production of the blank by means of a forging method proves particularly advantageous. The through-hole of the blank can preferably have an axially locally different diameter, so that the shape of the blank is already adapted to the rear shape of the hollow shaft. In this way, the forming (umforming) to be performed during the radial forming step is less than in the case with through holes of uniform diameter. Thereby saving time and energy costs. Through-holes with locally different diameters in the axial direction can be established in the context of the forging method used for producing the blank; alternatively, it is also conceivable to produce the through-hole afterwards by machining, for example by drilling. However, it is preferred to forge only the blank.

Drawings

Further details and advantages of the invention emerge from the following description and the accompanying drawings. Wherein:

figure 1 shows a first step of the manufacturing method according to the invention,

figure 2 shows a second step of the manufacturing method according to the invention,

figure 3 shows a third step of the manufacturing method according to the invention,

figure 4 shows a fourth step of the manufacturing method according to the invention,

figure 5 shows a fifth step of the manufacturing method according to the invention,

FIG. 6 shows a sixth step of the manufacturing method according to the invention and

fig. 7 shows the resulting flanged hollow shaft.

Detailed Description

In the drawings, like reference characters designate the same or similar elements.

Fig. 1 shows a first step of the manufacturing method according to the invention, namely the preparation of a blank 10. The blank 10 is preferably manufactured as a forging from steel. In the illustrated embodiment, the blank 10 has three axial regions in a generally hollow cylindrical configuration. The first axial region 12 (on the left in fig. 1) has a constant outer diameter and a constant inner diameter, i.e. is formed exactly in the form of a hollow cylinder. The second axial region 14 (on the right in fig. 1) has an likewise constant, larger outer diameter. The inner diameter is likewise greater than the inner diameter of the first axial region 12, but varies over the length of the region, which increases linearly, in particular toward its free (right) end, i.e., in the embodiment shown. Between the first and second

axial regions

12, 14 there is a transition region 16 for adapting to different diameters between the first and second

axial regions

12, 14. The shape of the blank 10 is adapted in particular to the shape of the hollow shaft to be produced. It is of course freely possible for the expert to use other blank shapes within the meaning of the invention, in particular for producing other hollow shaft shapes.

Fig. 2 shows a heating step of the blank 10, the heating taking place according to the invention mainly in the region of the second axial region 14 of the blank 10, preferably by means of an external induction furnace 17. Of course, a certain degree of warming of the first axial region 12 of the blank 10 is generally unavoidable here as well. However, this heating is used in particular to bring the second axial region 14 to the processing temperature necessary for the subsequent shaping.

The blank 10 thus heated (as shown in fig. 3) is clamped into a radial forming machine, in particular into its clamping device 18. This takes place in the region of the cooler first axial region 12. The blank 10 is then usually set in a rotational movement and is extended on one side by means of an externally acting forging tool 29. It is also contemplated to rigidly hold blank 10 while forging tool 19 is rotating. A mandrel (Dorn), not shown, can be introduced into the interior space.

As shown in fig. 4, the one-sided elongated blank 10 is then released from the holding device 18 and axially reversed.

In the subsequent reheating step shown in fig. 5, the blank 10 is reheated, i.e., mainly in the region of its not yet machined first axial region 12. The purpose of this heating step is to bring said first axial zone 12 to the processing temperature required in the subsequent radial forming step.

In the last method step shown in fig. 6, the reheated blank 10 is clamped into the radial forming machine again, however this time in the opposite orientation, so that the clamping tool 18 acts on the machined second axial region of the blank 10. The second radial forming step is carried out similarly to the first radial forming step shown in fig. 3, in which the first axial region 12 of the blank 10 is elongated on one side.

The hollow flanged shaft 20 shown in fig. 7 is produced with a first axial section 22, a second axial section 24 and a flange 26 delimiting them from one another. The flanged hollow shaft 20 can have extreme inside-and/or outside diameter differences and significant length. Such a shaft is particularly suitable as a rotor shaft for an electric machine (as a drive for a motor vehicle).

Of course, the embodiments discussed in the specific description and shown in the figures are only illustrative embodiments of the invention. The person skilled in the art is provided with a wide range of variation possibilities in accordance with the present disclosure.

List of reference numerals:

10 blank

1210 first axial region

1410 second axial region

16 transition region

17 induction furnace

18 clamping tool

19 forging tool

20 flange hollow shaft

2220 first axial section

2420 second axial segment

26 flange.

Claims

1. Method for producing a hollow shaft (20) having a first and a second axial section (22, 24), between which a radially outwardly projecting flange (26) is arranged, comprising the following steps:

-providing a metal blank (10) with an axial through hole,

-heating and clamping the blank (10) into a radial forming machine,

radially shaping the blank (10) in the radial shaping machine by forging technology for establishing the first and second axial sections (22, 24),

it is characterized in that the preparation method is characterized in that,

the first and second axial sections (22, 24) are built up in different radial forming steps, between which the partially machined blank (10) is removed from the radial forming machine and is clamped back in the opposite axial orientation, wherein the heating of the blank (10) is carried out selectively and directly before the clamping in each of the radial forming steps, in particular for the axial sections (22, 24) to be built up.

2. Method according to claim 1, characterized in that the blank (10) is held during sandwiching and heating by means of handling the jaws of a robot.

3. Method according to any one of the preceding claims, characterized in that the heating of the blank (10) is carried out outside the radial forming machine.

4. A method as claimed in claim 2, wherein said jaws grip said blank (10) outside the area in which the respective axial region (22, 24) is established in the respective subsequent radial forming step.

5. Method according to claim 1 or 2, characterized in that the blank (10) is manufactured by means of a forging method.

6. A method according to claim 1 or 2, characterized in that the through-holes of the blank (10) have axially locally different diameters.