WO2001058616A1

WO2001058616A1 - Method and a press cylinder device for producing a hollow body

Info

Publication number: WO2001058616A1
Application number: PCT/EP2001/000435
Authority: WO
Inventors: Bernhard Rolf
Original assignee: Leico Gmbh & Co. Werkzeugmaschinenbau
Priority date: 2000-02-09
Filing date: 2001-01-16
Publication date: 2001-08-16
Also published as: DE10005578C2; ATE251511T1; US20030019269A1; EP1253984A1; EP1253984B1; DE10005578A1; DE50100755D1

Abstract

The invention relates to a method and a press cylinder device for producing a hollow body consisting of a tubular workpiece (10) comprising a step (20). A conical area (12) is embodied on the tubular workpiece. Said area is heated in a specific manner. An axial compressing force (f) is subsequently exerted on the workpiece in such a way that the heated conical area (12) is compressed and shaped to form the step (20). Shaping of the conical area and compressing can be carried out on a press cylinder device.

Description

Method and pressure rolling device for producing a hollow body

The invention relates to a method for producing a hollow body, in particular a hollow shaft, with at least one step-shaped shoulder from a tubular workpiece according to the preamble of claim 1. Furthermore, the invention relates to a pressure rolling device according to the preamble of claim 8.

Such a pressure rolling device comprises a spindle which can be driven in rotation, a holding device attached to it for holding a tubular workpiece on the spindle in a rotationally fixed manner, a pressing mandrel with an outer contour which is matched to an inner contour of the workpiece, and a step-up element which is axially adjustable relative to the spindle ,

A generic method and a generic device can be seen, for example, from DE 195 11 963 AI. Here, a tubular starting workpiece is clamped in a press-rolling machine and drawn in radially by the radial feed of a press roller. This method is particularly efficient for simple parts. When a section of the tubular starting workpiece is drawn in radially, step-shaped shoulders with radially extending walls are formed. Under certain circumstances, these radially extending walls can be exposed to strong forming forces, which on the one hand are too dilution of the walls and, on the other hand, if the forming capacity is exceeded, can lead to embrittlement and cracking.

A similar problem can arise in the method for producing a shaft according to DE 197 25 453 AI. In this known method, the shaft is designed as a hollow shaft which has step-shaped shoulders in order to reduce weight. In the case of hollow shafts, relatively high loads can occur on the step-shaped shoulders during operation, which require a correspondingly large dimensioning of the entire hollow shaft wall. However, this contradicts the need for a light shaft with a low moment of inertia.

The invention is based on the object of specifying a method and a device with which a hollow body, in particular a hollow shaft, with a step-shaped heel can be produced in an economical and weight-saving manner, with high strength being ensured in the area of the step-shaped heel.

The object is achieved on the one hand by a method with the features of claim 1 and on the other hand by a pressure rolling device with the features of claim 8. Preferred embodiments of the invention are specified in the dependent claims.

Starting from a generic method, the invention is characterized in that a conical area is formed on the tubular workpiece, which constricts a first workpiece section with a larger diameter. Knife connects with a second workpiece section with a smaller diameter that the conical area is specifically heated, that an axial compressive force is exerted on the workpiece, and that the heated conical area is compressed and formed into the step-shaped shoulder. Due to the axial upsetting, the tubular starting workpiece collapses in a targeted manner in the heated conical area, a step-shaped shoulder with a high wall thickness and thus a high strength being formed by the material resulting from the upsetting. The targeted heating in the conical area influences the material of the workpiece in such a way that it can be plastically deformed with respect to adjacent workpiece areas at a desired axial force. This ensures that even with relatively long workpieces, compression occurs only at the desired workpiece area. The heating can be carried out by a heating device or by friction due to the presence of pressure rollers. In the latter case, because of the three-dimensional state of tension generated by the pressure rollers, a relatively slight heating can be sufficient for the upsetting and wall thickening.

In principle, any tubular workpiece which is produced, for example, by casting or forging can be used for the method according to the invention. A particularly reliable design of the conical area is achieved according to one embodiment of the invention in that the conical area of the tubular workpiece is formed by pressure rolling in a pressure rolling machine. For example, a targeted reduction in wall thickness can be set on the conical area, at which the workpiece then buckles in a defined manner during compression. A preferred further development of the invention consists in the fact that the heating and the axial compression of the conical area in the pressure rolling machine are carried out in the same clamping as the pressure rolling. This enables the desired cylindrical hollow body to be produced particularly economically.

In the case of axial upsetting, the shape of the step-like heel can develop freely without additional action from tools. If a particularly exact contour of the stepped shoulder is desired, it is advantageous according to the invention that the workpiece rotates during axial upsetting and when the stepped shoulder is shaped and that the stepped shoulder is shaped under the action of at least one pressure roller. This pressure roller can be a calibration roller which specifies the exact contour of the desired paragraph.

According to a further embodiment of the invention, it is preferred that when the step-shaped heel is formed, a wall thickness reinforcement is specifically formed on the heel. This can be done in particular in that the material obtained during upsetting can freely form a material bead on the inside of the hollow body.

If, on the other hand, an exactly defined inner contour is desired in the hollow body, it is provided according to the invention that when the stepped shoulder is formed, a mandrel is inserted into the workpiece, which mandrel specifies an inner contour of the shoulder. This inner contour can be a cylindrical shape with a right-angled shoulder for receiving a bearing. In this variant with a precisely specified inner contour, a material can preferably be Rialwulst be provided on the outside of the hollow body, which is processed in a subsequent machining, for example to form a bearing seat. In this way, it is reliably ensured that even with subsequent machining, a sufficiently large wall thickness and high strength are available in the graded area.

Furthermore, it is preferred according to the invention that a plurality of step-shaped shoulders are formed on a workpiece. For this purpose, the individual steps can first be formed one after the other, the first conical region first being heated and then the associated step being formed immediately thereafter. These steps are then repeated until all of the paragraphs are formed. In another variant, the different conical areas can be heated at the same time, the shoulders then being formed in a single, common upsetting process.

Starting from a generic pressure rolling device, the object is achieved according to the invention in that a device is provided for the targeted heating of a workpiece area and in that the front end is designed to exert an axial compressive force on the workpiece. With the spinning-rolling device according to the invention, the previously described method can be carried out in one clamping on a spinning-rolling machine.

A suitable device, which is an induction device, a heat radiator, a laser or a burner, etc., can be provided on the pressure-rolling device for heating the workpiece. A preferred embodiment of the invention consists in that the pressing mandrel is arranged on the front cover and that a stop for transmitting the compression force is formed on the front cover. It is possible to set the mandrel on the step-up first to adjust the wall thickness of the workpiece and to form the conical area by spinning rollers in counter-clockwise or synchronous fashion. Subsequently, an axial pressure force can be exerted on the workpiece by moving the presetter over a stop on the presetter in order to form the desired gradation. The mandrel can also remain inside the workpiece in order to ensure a defined inner contour even during upsetting.

This embodiment is preferably further developed in that the pressure mandrel has at its free end a pull-in mandrel section which is arranged on the pressure mandrel to form a step-shaped shoulder which serves as a stop. In this device, after the setting of the wall thickness of the workpiece and the shaping of the conical region, the pressing mandrel is moved out of the tubular workpiece except for the mandrel section. The free end of the workpiece is then drawn in against the mandrel section using a pressure roller, the diameter of the workpiece being reduced at the drawn-in section. In this way, the free end of the workpiece lies opposite the stop, so that the desired compression force for shaping the stepped shoulder can be transferred by axially adjusting the front.

A particularly efficient machining of the workpiece is achieved according to the invention in that the holding device has a driver toothing into which the workpiece can be axially formed in order to produce a rotationally fixed connection. After precentering on the mandrel, the workpiece is pressed against the driver toothing with high axial force by the step-up device and / or the pressure roller, the workpiece being formed in the driver toothing with the formation of a rotationally fixed connection.

The invention is described below with reference to preferred exemplary embodiments, which are shown schematically in the drawings. The drawings show:

Fig. 1 shows schematic cross-sectional views of a workpiece machined according to the invention in various processing stages and

2 shows schematic cross-sectional views of a workpiece clamped in a press-rolling device according to the invention in various processing stages.

A tubular workpiece 10 is shown in FIG. 1 a, which is arranged centrally on a pressing mandrel 50. The mandrel 50, which is part of a pressure rolling device, has a first cylinder region 54 and a second cylinder region 56 with a smaller diameter, which are connected to one another via a cone region 52.

A desired outer contour of the workpiece 10 is set in the counter-rotating press rolls by axially and / or radially feeding at least one press roll 40. In order to achieve the shape shown in FIG. 1b, the pressure roller 40 is axially advanced to the rotating workpiece 10, with a corresponding entry angle on the pressure roller 40 Diameter is reduced and the workpiece is axially elongated at the same time. With a defined setting of the forming parameters, in particular the pressure force and the speed of rotation, the counter-rotation pressure rolling can be carried out by the roller at a distance from the mandrel 50. The various diameter ranges in accordance with sections d1 and d2 in FIG. 1b are achieved by changing these forming parameters and / or the radial feed position of the pressure roller 40. The diameter ranges d3 and d4 are achieved by a well-known ironing-press roll, in which the press roll 40 forms the material in direct cooperation with the pressure mandrel 50. Here, in the present embodiment, a conical region 12 is formed with a defined wall thickness, which connects a first workpiece section 14 with a larger diameter to a second workpiece section 16 with a smaller diameter.

A schematically illustrated device 44 is then delivered to the conical region 12, by means of which the conical region 12 is specifically heated. In this case, a temperature of the workpiece is preferably set in this area above the recrystallization temperature, so that the subsequent upsetting process can take place specifically in this area and without strain hardening.

The axial upsetting process, in which a force F is exerted on the workpiece 10, is illustrated in FIG. 1c. The conical region 12 is pushed together by the axial force F to form a step-shaped shoulder 20. In order to achieve a defined outer contour, a calibration roller 42 with a corresponding one stepped contour used, as can be seen from the detail according to Figure ld. The upsetting process results in an accumulation of material, which leads to a thickening of the wall thickness 22 in the area of the step-shaped shoulder 20.

To set a defined inner contour, as can be seen from the upper half of FIG. 1c, the pressing mandrel can be inserted into the workpiece 10. Alternatively, according to the lower half of FIG. 1c, a material bead 24 can be formed in the case of a workpiece 10 that is not supported on the inside, which bead provides additional material reinforcement on the inside of the workpiece 10.

The hollow body shaped in this way with the step-shaped shoulder 20 is shown in FIG. This hollow body can optionally be provided with a further step-shaped shoulder, a further conical region 32 being initially formed according to FIG. 1f by a correspondingly shaped pull-in roller. This further conical region 32 can then be formed in accordance with the preceding method steps by heating and axially compressing the further step-shaped shoulder. In this way, a hollow shaft with an undercut can be formed efficiently and with high accuracy, with a particularly strong material accumulation on the corresponding step-shaped shoulders.

An alternative implementation of the method and a device according to the invention are shown in FIGS. 2a to 2d. A tubular workpiece 10a with a solid base region 11 and a centering hole made therein is provided by three schematically indicated multipurpose pressure rollers 46 which, in a known manner, provide a defined offset in the circumferential, radial and axial directions. have each other, axially pressed against a driver toothing 64 of a holding device 62. The holding device 62 is connected in a rotationally fixed manner to a spindle 60 of a pressure rolling device, the basic structure of which is known from the prior art with regard to the frame, drive and mounting of the pressure rollers. Between the spindle 60 and the holding device 62, a resiliently and axially displaceably mounted centering pin 61 is provided, which engages in the centering opening for the central mounting of the workpiece 10a.

According to FIG. 2a, the multipurpose spinning roller 46 first lengthens the workpiece 10a by means of counter-rotating spinning rollers. The intermediate product produced in this way can be seen in FIG. 2b. At this time, the multipurpose spinning roller 46 is returned to the free end of the workpiece 10a, at the same time the roller is tilted by a tilt angle, for example by 20. As a result of this adjustment of the multipurpose spinning roller 46, it is no longer the infeed area 47 that is used in counter-counter-pressure rolling, but rather the pull-in section 48 that protrudes in a beaded manner from the workpiece 10a.

According to FIG. 2c, a pressing mandrel 50a introduced into the workpiece 10a during the counter-current rolling is largely moved out of the workpiece 10a, so that only a cylindrical pull-in section 72 arranged at the free end of the pressing mandrel 50a remains in the workpiece 10a. Compared to the diameter of the cylindrical mandrel 50a, the pull-in section 72 is smaller in diameter, with a defined shoulder 74 being formed. This shoulder 74 serves as an axial stop through which on the one hand, an axial elongation of the workpiece 10a can be limited and, on the other hand, an axial compressive force can be transmitted to the workpiece 10a by means of a push-in mandrel 50a.

The free end of the workpiece 10a is pressed radially inward against the cylindrical mandrel portion by the bead-shaped pull-in section 48 of the multipurpose pressure roller 46, a conical region 12a being formed on the workpiece 10a. According to the description of the method in FIG. 1, this conical region 12a can be shaped into a step-shaped shoulder. For further forming operations, the multipurpose pressure roller 46, which is tilted by an angle α with respect to the counter-rotation pressure rolling, is moved along the outer circumference of the workpiece 10a in a generally known manner.

Claims

1. A method for producing a hollow body, in particular a hollow shaft, with at least one stepped shoulder (20) from a tubular workpiece (10), thereby ensuring that

- that on the tubular workpiece (10) a conical area (12) is formed, which connects a first workpiece section (14) with a larger diameter to a second workpiece section (16) with a smaller diameter,

- That the conical area (12) is specifically heated,

- That an axial compression force is exerted on the workpiece (10) and

- That the heated conical area (12) is compressed and formed into the step-shaped shoulder (20).

2. The method according to claim 1, characterized in that the conical region (12) of the tubular workpiece (10) is formed by pressure rolling in a pressure rolling machine.

3. The method according to claim 2, characterized in that the heating and the axial upsetting of the conical region (12) is carried out in the press-rolling machine in the same clamping as the press-rolling.

4. The method according to any one of claims 1 to 3, characterized in that the workpiece (10) rotates during the axial upsetting and shaping of the step-shaped heel (20) and that the shaping of the step-shaped heel (20) under the action of at least one pressure roller (42 ) he follows.

5. The method according to any one of claims 1 to 4, characterized in that when the step-shaped heel (20) is formed, a wall thickness reinforcement is specifically formed on the heel (20).

6. The method according to any one of claims 1 to 5, characterized in that a mandrel (50) is inserted into the workpiece (10) when shaping the step-shaped heel (20), which mandrel specifies an inner contour of the heel (20).

7. The method according to any one of claims 1 to 6, characterized in that a plurality of step-shaped shoulders (20) are formed on a workpiece (10).

8. Press-rolling device, in particular for forming a hollow body according to one of claims 1 to 7, with

- a rotationally drivable spindle (60),

- A holding device (62) attached thereto for the rotationally fixed holding of a tubular workpiece (10) on the spindle (60),

- A pressing mandrel (50) with an outer contour, which is adapted to an inner contour of the workpiece (10), and

a step-up element which can be adjusted axially relative to the spindle (60), thereby ensuring that

- That a device (44) is provided for the targeted heating of a workpiece area and

- That the step-up is designed to exert an axial compressive force on the workpiece.

9. The press-rolling device according to claim 8, characterized in that the pressing mandrel (50) is arranged on the push-in device and that a stop for transmitting the compression force is formed on the push-in device.

10. A press-rolling device according to claim 8 or 9, characterized in that the mandrel (50) has at its free end a mandrel section (72) which is arranged on the mandrel (50) to form a step-shaped shoulder (74) which acts as a stop serves.

1. Press-rolling device according to one of claims 8 to 10, characterized in that the holding device (62) has a driver toothing (64) into which the workpiece (10) can be axially formed to produce a rotationally fixed connection.