EP3682981B1 - Method and device for pressure rolling - Google Patents

Description

The invention relates to a method for flow-forming a vehicle wheel, wherein a workpiece is set in rotation about an axis of rotation by means of a spindle and at least one outer roller is fed by means of an outer support on an outside of the workpiece, with an axially extending jacket area of the workpiece being formed with material thinning , according to the preamble of claim 1.

The invention also relates to a device for flow-forming with a spindle which can be driven by a drive to rotate about an axis of rotation and is designed to hold a workpiece, at least one outer roller which is rotatably mounted on an outer support which is used to feed the workpiece axially and radially can be moved relative to the axis of rotation, and at least one inner roller which can be advanced to an inner side of the workpiece opposite the outer roller, according to the preamble of claim 8.

Vehicle wheels in particular, preferably made of an aluminum material, are spin-formed against a central spinning chuck. The spinning chuck, also known as a spinning tool, represents the negative form of the inner geometry of the rim of a vehicle wheel. A change in the rim usually also requires a change in the spinning chuck, which is expensive. Manufacturing vehicle wheels or other pressed parts with an inner contour is therefore often only economical for large quantities. Such a generic method with a pressure chuck is from DE 10 2011 117 034 A1 known. In addition to external forming rollers, axial limiting rollers are provided to limit an axial flow of material.

A method for flow-forming with increased flexibility in shaping is from EP 2 210 682 B1 known. In this known method, a variable spinning mandrel with a conical outer contour is provided as the spinning chuck. The The spinning mandrel is arranged concentrically to the axis of rotation. By axially adjusting the spinning mandrel, a variable inner diameter can be provided at the respective forming zone. However, this method is limited to certain inner contours.

From the DE 35 45 506 A1 a tool for flow-forming hollow-cylindrical workpieces is known. At the same time as the delivery of outer rollers to an outer contour of the tubular workpiece, inner rollers are delivered to an outer contour with an inner roller carrier. A fixed distance is predetermined between the outer roller and the inner roller, which distance predetermines the extent of flow-ironing and the wall thickness of the tubular workpiece to be formed.

A similar procedure is from U.S. 3,287,951 known. An outer roller and an associated inner roller are arranged on a common roller carrier. The outer roller can be adjusted via a mechanical adjustment mechanism so that the distance between the inner roller and the outer roller can be adjusted at the beginning of the forming process.

The invention is based on the object of specifying a method and a device for flow-forming with which a particularly large variety of vehicle wheel shapes can be produced flexibly and efficiently.

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

The method according to the invention is characterized in that at least one inner roller is fed to an inner side of the workpiece by means of an inner support, which can be moved axially and radially to the axis of rotation independently of the outer support, and that the inner support with the inner roller and the The outer support can be moved individually with the outer roller, with a defined wall thickness profile having different wall thicknesses being formed between the at least one outer roller and the at least one inner roller on the casing area.

A basic idea of the invention is to move away from a specified spinning tool, which specifies a negative shape of an inner contour of the workpiece, and to provide at least one inner roller for shaping the inner contour. The inner roller is not moved in a straight line parallel to the outer roller, but the inner roller is mounted on an inner support, which can be moved axially and radially to the axis of rotation independently of the outer support. In this way, an almost unlimited variety of shapes can be produced without converting a spinning tool.

Furthermore, according to the invention, a CNC control is provided and preferably additional programming support software, which is used in particular offline on a PC. With the control, the inner support with the inner roller and the outer support with the outer roller can be moved independently of one another. A free contour course can thus be set on the inside and outside of the workpiece. Furthermore, by adjusting the outer roller relative to the associated inner roller, the effective shaping gap and thus a wall thickness profile in the axial jacket region of the workpiece to be shaped can be formed with a high degree of shaping freedom. The term flow-forming is to be understood broadly within the meaning of the invention and includes not only forming with a change in wall thickness but also pressing with the wall thickness remaining the same.

With the method, workpieces can be produced efficiently, even in small quantities or even individual workpieces, since a complex production of a rigid spinning mandrel is not necessary. Rather, the contour is freely adjusted to one another by appropriate control of the rollers.

A preferred embodiment of the invention consists in the fact that the at least one inner roller and the at least one associated outer roller are moved radially and axially with respect to one another in order to shape the jacket region. As a result, an individual course of the inner contour and outer contour as well as a wall thickness course arranged between them can be set almost as desired. According to one finding of the invention, the wall thickness is not only determined by a radial distance between the inner roller and the outer roller. Particularly in the case of flow-ironing, in which the mantle area is compared to an original starting thickness is reduced, the inner roller or the outer roller can advance or lag behind the other roller in a targeted manner in the axial direction. As a result, an abutment function is also created in an axial direction, which can be essential for ironing with a precise shape.

According to the invention, it is provided that the workpiece is clamped on the spindle, with a free space remaining in a central area radially inside the jacket area. This jacket area is designed so large that at least one inner roller can be advanced to an inner contour of the jacket area. For this purpose, the workpiece is preferably clamped on one side on the spindle, for example by means of a three-jaw or multi-jaw chuck. Other clamping mechanisms may be used, including an axial clamping element or back-up element that attaches to or through a central opening at a hub portion of the workpiece.

It is also according to the invention that the workpiece is clamped in a partial area of the outer circumference. The workpiece can be held centered on the spindle from the outside using appropriate clamping jaws.

According to a development of the invention, it is preferred that the workpiece is provided with a clamping and/or centering aid before flow-forming. In the case of the chuck used, a centering for centering the workpiece during the clamping process is preferably provided. For this purpose, a corresponding centering aid can also be attached to the workpiece, which is cast on, in particular in the case of cast wheels. This can be designed in such a way, for example by means of projections or stop edges, that they support the transmission of torque from the chuck to the workpiece.

According to a preferred development, the invention provides for the clamping and/or centering aid to be removed from the workpiece after flow-forming. This can be done in particular by simple machining. This can also be done with a separate machine, such as a lathe, or the flow-forming device itself with a cutting additional tool.

For particularly gentle clamping, a preferred embodiment of the invention provides for an internal clamping device to be provided, by which a hub area of the workpiece is covered. This is because the forming of the wheel preferably begins in the immediate vicinity of a radially running hub region of the workpiece. On certain vehicle rims, this can be a star or rim spokes. The clamping device has a relatively large, plate-like clamping surface, which covers and protects the specially designed and preformed hub area.

In principle, the method according to the invention can be used to form any desired workpiece with an axially running, tubular casing area. According to a development of the invention, it is particularly preferred that the casing area is designed as a rim base of a vehicle wheel with at least one hump, which is formed as a thickening in the wall thickness profile. Also preferred is the forming of a cast preform into a rim blank, which is then further processed into the finished wheel, in particular by machining.

With the method according to the invention, a largely weight-optimized vehicle wheel can be produced in which the course of the wall thickness of the rim well is adapted to the actual load on the vehicle wheel during operation. In this case, areas with low loads are formed with a small wall thickness, while heavily loaded areas are formed with a correspondingly large wall thickening. In addition, a hump, that is to say a bead for fixing the tire to the rim base, can also be formed in a simple manner by thickening the wall along the rim base. The hump represents an annular elevation on the rim base that protrudes radially outwards.

It is particularly advantageous here that, in order to form a hump and/or horn region, the inner roller and the outer roller are simultaneously moved relative to one another in the radial and axial directions. The side rim flanges can also be shaped in a corresponding manner. Additional and different inner rollers with a modified and adapted outer contour can also be used to shape the rim flanges. The same applies to the use of contoured outer rollers to form the rim flanges. Thanks to the freely programmable interior and In addition, external rollers enable a gradual reshaping of the rim contour so that higher strain hardening and/or structural changes are brought about in specific areas of the rim. As a result, increases in stability and/or weight reductions on the workpiece are possible.

The flow-forming device according to the invention is characterized in that the at least one inner roller is rotatably mounted on an inner support, which is mounted so that it can be moved axially and radially to the axis of rotation independently of the outer support, and that a CNC control for individually moving the at least one inner support with the inner roller and the at least one outer support is provided with the outer roller, a wall thickness profile of the workpiece being adjustable between the inner roller and the outer roller.

The device according to the invention can be used in particular to carry out the method described above. The advantages described above can be achieved in this way.

A preferred embodiment of the device according to the invention consists in the fact that several inner rollers and outer rollers are provided, with one inner roller each being assigned to an outer roller. A plurality of inner rollers, preferably three inner rollers, are preferably arranged on a common roller carrier. Compared to this common roller carrier or inner support, the individual inner rollers can be pivotally adjustable relative to the axis of rotation. In this way, a targeted shaping of the various contour areas of the workpiece can be achieved. Depending on the application, inner rollers or inner supports that can be adjusted axially and/or radially with respect to one another can be provided separately in a further preferred embodiment.

According to a further development of the device according to the invention, it is preferred that a clamping device for clamping the workpiece is arranged on the spindle, with a free space remaining in a central area radially inside the jacket area of the workpiece. The at least one inner support can be moved into this free space, so that an inner contour of the jacket area of the workpiece can be formed by the at least one inner roller.

For highly efficient production, it is preferred according to one embodiment of the invention that a control device is provided with a data memory in which data sets for moving the inner roller and the outer roller are stored for different workpiece shapes. In this way, the desired data set for a specific workpiece design can be called up by a machine operator. Different workpieces can be efficiently produced on one flow-forming device without any complex conversion work. The device with the control device is provided with a long-distance data connection, in particular an Internet connection. In this way, new or updated data records for existing or new workpieces can be transferred to the machine's data memory. The device according to the invention can thus be provided for highly flexible use in Industry 4.0 projects.

Furthermore, according to a development of the invention, particularly good contouring can be achieved in that at least one of the rollers is provided with an auxiliary drive for driving the roller in rotation. Both the inner rollers and the outer rollers can be provided with a respective roller drive. As a result, the inner and/or outer rollers can be accelerated before they come into contact with the rotating workpiece material to be formed. This counteracts caking on the rollers and/or increased wear on the rollers. In a preferred embodiment, the roller drive is designed with a freewheel or speed control device that enables automatic adjustment of the peripheral speed of the roller to the component.

An ejector, in particular an axially adjustable ejector, can be used for ejection from the clamping device. The ejection is preferably performed as a controlled movement. The device for flow-forming is preferably designed as a vertical machine with a suspended or alternatively standing spindle, so that the workpiece centering is facilitated. In the version with a vertically suspended spindle, the counterholder of the clamping device can also assume the function of loading and unloading.

The inner and/or outer supports are preferably designed as independently controllable supports that are only electrically synchronized. The outer roller is preferably employed at an angle of 0 to 15 ° to the axis of rotation while the inner rollers are preferably set at an angle of 0 to 45° and contribute to the forming process via a preferably significantly larger roller radius. The infeed of the outer and inner rollers is preferably carried out via two linear working cross slides. Alternatively, the use of at least two inner rollers on the cross support can be dispensed with by simultaneously shifting or adjusting the rollers using wedge slides.

Fig. 1:

eine Teilquerschnittsansicht einer erfindungsgemäßen Vorrichtung beim Formen eines Fahrzeugrades in einem Anfangsstadium;

Fig.2:

eine Teilquerschnittsansicht der Vorrichtung von Fig. 1 beim Herstellen eines Fahrzeugrades in einem Endstadium;

Fig. 3:

eine Teilquerschnittsansicht einer weiteren Vorrichtung beim Herstellen eines Fahrzeugrades in einem Anfangsstadium und

Fig. 4:

eine Teilquerschnittsansicht der Vorrichtung von Fig. 3 beim Herstellen eines Fahrzeugrades in einem Endstadium.

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

Figure 1:

a partial cross-sectional view of an apparatus according to the invention when forming a vehicle wheel in an initial stage;

Fig.2:

a partial cross-sectional view of the device of FIG 1 in manufacturing a vehicle wheel in a final stage;

Figure 3:

a partial cross-sectional view of a further device in the manufacture of a vehicle wheel in an initial stage and

Figure 4:

a partial cross-sectional view of the device of FIG 3 when manufacturing a vehicle wheel in a final stage.

A device 10 according to the invention for flow-forming according to FIG 1 has a spindle 12 driven in rotation via a drive, not shown. The spindle 12 rotates about a central axis of rotation 13, which runs horizontally in the illustrated example. In the same way, the spindle 12 can be oriented vertically with the axis of rotation 13, with a workpiece 5 then resting on the spindle 12 or, in the case of a hanging spindle arrangement, being clamped on a spindle 12 lying at the top.

A workpiece 5 can be connected to the spindle 12 in a detachable and non-rotatable manner and centrically to the axis of rotation 13 via a plate-shaped clamping device 14 attached to the spindle 12 with axially acting clamping claws 16 . In the exemplary embodiment shown, the workpiece 5 is a preform of a vehicle wheel. The preform is preferably made of metal material by casting or forging manufactured. The rotationally symmetrical workpiece 5 has an essentially radially extending hub area 6 with a central opening 4 and an essentially axially extending drum-shaped casing area 7 . With the clamping claws 16, the workpiece 5 is fastened on one side on its outer circumference to the spindle 12.

After clamping, the spindle 12 with the workpiece 5 is rotated. Preferably three outer rollers 20, of which only one outer roller 20 is shown, are fed radially onto the outside of the jacket region 7 of the workpiece 5 by means of outer supports (not shown). At the same time, an inner support 40 with three inner rollers 30 arranged offset from one another by 120° is fed into a central free space within the drum-shaped casing area 7 . In this case, the inner rollers 30 are initially placed adjacent to the radial hub area 6 on an inside of the casing area 7 .

The inner support 40 has a centric and conical middle support 42, on the outside of which linear guides 44 for carriages 46 are arranged. Roller holders 48 are pivotably mounted on the linearly movable carriage 46 . In the pot-like roller holders 48, the inner rollers 30 are rotatably mounted on roller bearings. The inner rollers 30 can be pivoted via the pivotable roller holders 48 during the flow-forming process and can be moved radially and/or axially by means of the carriage 46 and the inner support 40 . In a corresponding manner, the outer rollers 20 can be pivoted on an outer support (not shown) and can be moved radially and axially.

The outer roller 20 and the inner roller 30 are moved via a CNC controller (not shown) and actuators using stored data for forming the desired workpiece 5. As shown in FIG 2 As can be seen, the casing area 7 of the workpiece 5 can be formed into a rim well with a hump 8 which represents a thickening in the course of the wall thickness of the casing area 7 . The finally shaped jacket area 7 is lengthened compared to the jacket area 7 of the starting workpiece 5 and thinned in terms of wall thickness. Almost any outer contour as well as an inner contour can be produced with the device 10 according to the invention.

The second embodiment according to Figures 3 and 4 essentially corresponds to the structure of the first device 10 according to the invention according to FIG figures 1 and 2 .

In contrast to the first embodiment, the device 10 according to FIG 3 a modified inner roller 30 is provided with an annular radial projection 32 and an abutment section 34 adjacent in the front area. The radially protruding radial projection 32 on the inner roller 30 can be used to form an inner contour along the inside of a jacket region 7 of the workpiece 5 in interaction with the outer roller 20 acting radially on the outside. The front abutment section 34 can be used to form a rim flange at the free end of the formed rim base, as illustrated in FIG 4 is shown. The abutment section 34 can in particular be designed as a negative shape of the inner contour of the rim flange and for absorbing the forming forces of the outer roller 20 . In a corresponding manner, different outer rollers 20 with an adapted outer contour can be placed on the jacket area 7 . In particular, an outer roller 20 can have an outer contour corresponding to the desired shape of the rim flange to be formed.

In addition, in the second embodiment according to FIGS Figures 3 and 4 for clamping the workpiece 5, in addition to the previously described clamping device 14 with axially movable clamping claws 16 for clamping the workpiece 5, an axially movable counter-holder 18 is also provided on the radial outside. In particular, after an initial contouring of the jacket area 7 , the counter-holder 18 can be pressed axially against the hub area 6 of the workpiece 5 in the central free space of the drum-shaped jacket area 7 . As a result, an additional axial clamping and centering of the workpiece can take place at least during a final stage of the flow-forming process. The counter-holder 18 can have a plate-shaped contact element 19 which is adapted to a contouring of the hub area 6 of the workpiece 5 .

With the device 10 according to the invention and the method that can be carried out on it, workpieces 5 with a large variety of shapes of a wall area 7 can be formed without any conversion measures.

For the first time, this process enables multiple, gradual flow-forming until the final end geometry or complete structural change has been achieved.

Preferred flow-forming of cast wheels at temperatures up to 400 °C. The wheels can be heat treated immediately after the flow-forming process.

In addition, the process can also be used for the cold forming of forged aluminum wheels and steel wheels.

The use of a special programming interface or the use of offline programming support software is also preferred in order to be able to create the complex programs more easily and more quickly, and to check and optimize them by simulation before use.

Alternatively, a combination of flexible inner rollers with a partially effective short mandrel is also possible.

Claims (11)

1. Method for flow forming a vehicle wheel,

   wherein a workpiece (5) is set in rotation about an axis of rotation (13) by means of a spindle (12), and at least one outer roller (20) is positioned by means of an outer support at an outer side of the workpiece (5),

   wherein, with material thinning, an axially extending circumferential region (7) of the workpiece (5) is shaped,

   characterized in that

   clamping of the workpiece (5) takes place at a part-region of the outer circumference wherein the workpiece (5) is clamped on the spindle (12), wherein a free space remains in a central region radially inside the circumferential region (7), in that at least one inner roller (30) is positioned in the free space and at an inner side of the workpiece (5) by means of an inner support (40), which is displaceable axially and radially relative to the axis of rotation (13) independently of the outer support,

   in that the inner support (40) with the inner roller (30) and the outer support with the outer roller (20) are displaced individually by means of a CNC control unit, wherein there is formed at the circumferential region (7) a defined wall thickness profile with different wall thicknesses between the at least one outer roller (20) and the at least one inner roller (30).
2. Method according to claim 1
   characterized in that
   the at least one inner roller (30) and the at least one associated outer roller (20) are displaced radially and axially relative to one another in order to shape the circumferential region (7).
3. Method according to any one of claims 1 or 2,
   characterized in that
   the workpiece (5) is provided with a clamping and/or centering aid before flow forming.
4. Method according to claim 3,
   characterized in that
   the clamping and/or centering aid is removed from the workpiece (5) after flow forming.
5. Method according to any one of claims 1 to 4,
   characterized in that
   an internal clamping device (14) is provided, by which a hub region (6) of the workpiece (5) is covered.
6. Method according to any one of claims 1 to 5,
   characterized in that
   the circumferential region (7) is shaped as a rim base of the vehicle wheel with at least one hump (8), which is formed as a thickening in the wall thickness profile.
7. Method according to claim 6,
   characterized in that
   in order to form a hump (8) and/or flange region, the inner roller (30) and the outer roller (20) are simultaneously displaced relative to one another in the radial and in the axial direction.
8. Device for flow forming a vehicle wheel by a method according to any one of claims 1 to 7, having

   - a spindle (12) which can be driven in rotation via a drive about an axis of rotation (13) and is configured to hold a workpiece (5),

   - at least one outer roller (20), which is rotatably mounted on an outer support, which is displaceable axially and radially relative to the axis of rotation (13) in order to position it at the workpiece (5), and

   - at least one inner roller (30), which can be positioned at an inner side of the workpiece (5) opposite the outer roller (20),

   characterized in that

   a clamping device (14) for clamping the workpiece (5) is arranged on the spindle (12) at a part-region of the outer circumference, wherein a free space remains in a central region radially inside the circumferential region (7) of the workpiece (5), in that the at least one inner roller (30) is rotatably mounted on an inner support (40), which is mounted to be displaceable axially and radially to the axis of rotation (13) independently of the outer support, and

   in that a CNC control unit for individually displacing the at least one inner support (40) with the inner roller (30) and the at least one outer support with the outer roller (20) is provided.
9. Device according to claim 8,
   characterized in that
   there are provided several inner rollers (30) and outer rollers (20), wherein respectively an inner roller (30) is assigned to an outer roller (20).
10. Device according to any one of claims 8 or 9,
    characterized in that
    there is provided a control device having a data memory, in which data sets for the displacement of the inner roller (30) and the outer roller (40) for different workpiece shapes are stored.
11. Device according to any one of claims 8 to 10,
    characterized in that
    at least one of the rollers (20, 30) is provided with an auxiliary drive for driving the roller (20, 30) in rotation.

Images