INTERNALLY COOLED VALVE FOR INTERNAL COMBUSTION ENGINES, AS WELL AS METHOD AND DEVICE FOR THE PRODUCTION THEREOF

Abstract

A method and a device for the production of an internally cooled inlet or outlet valve for internal combustion engines, together with the resultant valve includes provision of a workpiece, which has a cylindrical stem and a cylindrical hole and, extends in the axial direction from one end of the valve stem. The method includes reshaping the end of the valve stern by form rolling of the cylindrical stem to a smaller diameter, wherein a diameter of the cylindrical hole is reduced, wherein the cylindrical hole remains. The method further includes reshaping by form rolling the section of the workpiece that is adjacent to the valve stem to form the valve head.

Claims

1. A method for the production of an internally cooled valve (4) for internal combustion engines, comprising: provision of a workpiece (14, 16), which comprises a stem and a cylindrical hole (26, 28), which extends from one end of the valve stem (36) in the axial direction, reshaping of the valve stem end (36) by form rolling of the stem to a smaller diameter, wherein a diameter of the cylindrical hole is reduced, wherein the hole (26, 28) remains, and reshaping by form rolling of a section of the workpiece (14, 16) that is adjacent to the valve stem (8) to form the valve head.

2. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with claim 1, wherein prior to the form rolling process the workpiece (14, 16) comprises a diameter of at least that of the valve disk (6) of the finished valve, and further comprising: form rolling of a transition section between the valve head and the valve stem (8) to form a concave fillet.

3. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with claim 1 or 2, wherein the workpiece (16) is cup-shaped, wherein the cup-shaped workpiece (14, 16) has a diameter at a base of the workpiece (16) that corresponds at least to that of the valve disk (6), wherein the cylindrical hole is a blind hole (26), which extends from one end of the valve stem (36) in the direction of the base of the cup-shaped workpiece (16), and wherein the form rolling process comprises a reshaping of the stem and a shaping of the valve body.

4. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with claim 3, wherein an outer surface of the base of the workpiece (16) already has the shape of the valve disk (6).

5. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with claim 3 or 4, wherein the workpiece (16) is cup-shaped, and wherein the cup-shaped workpiece (16) has a larger diameter at a base of the workpiece (16) than in the area of the cylindrical stem.

6. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, wherein the workpiece (14, 16) is held between the rollers by means of guides.

7. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, wherein the workpiece (14, 16) is hot rolled.

8. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, further comprising: axial movement of the workpiece (14, 16) in the direction of the stem end (36) during the rolling process.

9. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, further comprising: rotation of the workpiece (14, 16) during the rolling process.

10. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, further comprising: turning of the valve stem (8) to a desired outer diameter, after a desired inner diameter of the valve stem (8) has been achieved by rolling.

11. The method for the production of an internally cooled valve (4) for internal combustion engines, in accordance with one of the preceding claims, wherein the provision of the workpiece (14, 16) comprises a provision of the workpiece (14, 16) with a non-cylindrical stem with an outer contour (70) and the cylindrical hole (26, 28), wherein the reshaping of the valve stem end (36) by form rolling comprises a reshaping of the valve stem end (36) by form rolling of the stem to a smaller diameter, wherein a diameter of the cylindrical hole is reduced, and a non-cylindrical hole with an inner contour (72) remains.

12. A device for the production of an internally cooled valve (4) for internal combustion engines, from a workpiece (14, 16), comprising: a rolling mill for purposes of round cross rolling or skewed rolling, wherein at least two forming rollers (42, 44) have a profile of an outlet valve.

13. The device for the production of an internally cooled valve (4) in accordance with claim 12, further comprising: a mandrel, which can be inserted into a hole (26, 28) of a workpiece (14, 16) so as to guide the workpiece (14, 16) during the rolling process.

14. The device for the production of an internally cooled valve (4) in accordance with claim 12, further comprising: at least one guide so as to hold and guide the workpiece (14, 16) between the rollers, wherein the at least one guide comprises a sliding member, or one or a plurality of rollers, which abut against an outer surface of the workpiece (14, 16).

15. The device for the production of an internally cooled valve (4) in accordance with claim 11, 12, 13, or 14, further comprising: at least one load cell on the at lease one guide, together with individually driven forming rollers (42, 44), and a controller that controls the rotational speed of the forming rollers (42, 44) such that the force on the guides is minimised.

16. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 15, characterised in that the axes of the rollers are arranged skewed relative to one another at an angle of 1 to 12, preferably of 2 to 10, and more preferably of 3 to 8.

17. The device for the production of an internally cooled valve (4) in accordance with claim 16, characterised in that the axis of the workpiece (14, 16) and the axes of the forming rollers (42, 44) are in each case arranged skewed relative to one another at an angle of 0.5 to 6, preferably of 1 to 5, and more preferably of 1.5 to 4.

18. The device for the production of an internally cooled valve (4) in accordance with one of the claims 16 or 17, wherein at least one of the forming rollers (44) has a hyperboloidal outer surface.

19. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 18, wherein at least one of the forming rollers (42, 44) has a surface structure, which causes a transport of the material of the workpiece in the axial direction.

20. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 19, further comprising: an axial guide or a clamping chuck, so as to guide and/or hold the workpiece (14, 16) from the disk face.

21. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 20, further comprising: an actuator, so as to move the workpiece (14, 16) axially, from the base in the direction of the valve stem end (36).

22. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 21, further comprising: a drive, so as to rotate the workpiece (14, 16) during the rolling process at a predetermined rotational speed.

23. The device for the production of an internally cooled valve (4) in accordance with one of the claims 12 to 22, further comprising: a heating element, so as to heat the workpiece (14, 16) during the rolling process.

24. An internally cooled valve (4) for internal combustion engines, characterised in that it has been reshaped from a workpiece (14, 16) using one of the methods of claims 1 to 10, or using a device according to any one of claims 12 to 23, wherein the workpiece (14, 16) comprises a stem, wherein the workpiece (14, 16) also comprises a cylindrical hole, which extends from one end of the valve stem (36) in the axial direction, wherein at least one stem has been reshaped by form rolling of the stem to a smaller diameter.

25. An internally cooled valve (4) for internal combustion engines in accordance with claim 24, characterised in that prior to the form rolling process the workpiece (14, 16) comprises a diameter of at least that of the valve disk (6), and in that a valve head is produced with a concave fillet by means of form rolling.

26. An internally cooled valve (4) for internal combustion engines in accordance with claim 24 or 25, characterised in that the workpiece (16) is cup-shaped, wherein the cup-shaped workpiece (16) has a diameter at a base of the workpiece (16) that corresponds at least to that of the valve disk (6), wherein the cylindrical hole is a blind hole (26), which extends from one end of the valve stem (36) in the direction of the base of the cup-shaped workpiece (16).

27. An internally cooled valve (4) for internal combustion engines in accordance with claim 26, characterised in that the workpiece (16) is cup-shaped, wherein the cup-shaped workpiece (16) has a larger diameter at a base of the workpiece (16) than in the area of the cylindrical stem.

28. An internally cooled valve (4) for internal combustion engines in accordance with one of the claims 24 to 27, characterised in that after the reshaping process the cylindrical hole (26, 28) forms a cavity (10) that extends within the valve stem (8) and the valve disk (6), which cavity is partially filled with sodium (12) and sealed.

29. An internally cooled valve (4) for internal combustion engines in accordance with one of the claims 24 to 28, characterised in that prior to the rolling process the workpiece (14, 16) has a non-cylindrical stem with an outer contour (70) and with a cylindrical hole (26, 28), wherein as a result of the reshaping of the valve stem end (36) by form rolling the valve has a cylindrical valve stem and a non-cylindrical hole with an inner contour (72).

Description

[0046] In what follows the present invention will be explained by way of illustrations of exemplary embodiments. The figures represent purely schematic illustrations.

[0047] FIGS. 1A to 1D illustrate an embodiment of an inventive device for the production of an internally cooled valve from a tubular workpiece, and the associated production method.

[0048] FIGS. 2A to 2C show a further embodiment of an inventive device for the production of an internally cooled valve from a cup-shaped workpiece, and the associated method.

[0049] FIGS. 3A to 3C illustrate a further embodiment of an inventive device for the production of an internally cooled valve from a short cup-shaped workpiece, and the associated method.

[0050] FIGS. 4A to 4B show an additional embodiment of an inventive device for the production of an internally cooled valve from a short cup-shaped workpiece by means of skewed rolling.

[0051] FIGS. 5A and 5B illustrate a further additional embodiment of an inventive device for the production of an internally cooled valve from a short cup-shaped workpiece, and the associated method.

[0052] FIGS. 6A and 6B illustrate a further additional embodiment of a workpiece and an internally cooled valve

[0053] In both the description and the figures, the same or similar reference symbols are used to refer to the same or similar components and elements. In order to avoid a description of unnecessary length, elements that have already been described in one figure are not separately mentioned in further figures.

[0054] In order not to make the drawings unnecessarily complicated, the parts of the rolling device that serve to carry, mount, or drive the rollers, or to move them at right angles to a roller axis, or in the direction of a workpiece axis, have not been illustrated. Any mountings or suspensions of guides and axial guides have also been omitted from the illustrations.

[0055] FIG. 1A shows an inventive rolling device with two forming rollers 42. The forming rollers are provided with stub axles 64, with which they can be accommodated in a housing of a rolling device. The forming rollers 42 can also be driven together or individually via the stub axles.

[0056] At the top of FIG. 1A, the axes are shown in a plan view, wherein the plane of the drawing extends essentially through the axes 48 of the rollers 42, and the axis 46 of the workpiece 14. The outer contour of the forming rollers 42 corresponds to the negative profile of an inlet or outlet valve that is to be rolled. Between the forming rollers 42 is arranged a tubular workpiece 14 with a through-opening or through-hole 28. The axis 46 of the workpiece 14 and the axes 46 of the rollers 42 are aligned in parallel. At the bottom of FIG. 1A the rollers 42 and the workpiece 14 are shown in a view in the axial direction. In FIGS. 1A and 1B the rollers are designed for a round cross rolling process. The rollers are designed as forming rollers 42. The respective directions of rotation of the rollers and the workpiece are indicated by the arrows 60. In round cross rolling, the workpiece 14 rotates about the axis 46 of the workpiece 14 in the opposite direction to the forming rollers 42 between two forming rollers rotating in the same direction. By the infeed of at least one tool, that is to say, one forming roller 42, the work piece 14 is reshaped. Here it is shown that both rollers are moved towards the workpiece 14 in the direction of movement and force application 62. However, it is also possible to move just one of the rollers 42 in the direction of the workpiece 14, i.e. to move it towards the other roller, wherein the axis of rotation of the workpiece 14 is displaced. Here the workpiece 14 is held in the axial direction by a clamping chuck 56, whose clamping jaws are shown. Here the clamping chuck 56 serves as an axial guide 54 so as to prevent the workpiece 14 from moving during the rolling process in the direction of what will later be the valve disk; such movement is brought about by the axial component of the rolling forces in the area of the rear face of the valve disk.

[0057] The form rolling process has, inter alia, the advantage that the molecular chain structure in the workpiece 14 is retained, which generates an undisturbed orientation of the fibres. As a result it can also be established on the basis of the crystal structure using metallurgical methods on the finished valve as to whether it has been produced, that is to say, formed, by forming rollers.

[0058] The axes 48 of the forming rollers 42 define a plane, and while the axis of the workpiece 14 lies parallel to this plane, it is not in this plane; instead in the drawing it is below this plane. In a rolling process, the workpiece 14 would be pushed downwards as soon as the forming rollers 42 initiate the rolling process. The workpiece 14 is therefore supported in the figure from below by a guide, more particularly, a radial guide 52, which serves as a radial guide. From an application of the force parallelogram it becomes clear that the force acting on the guide can be much lower than the rolling forces that arise as the forming rollers 42 move towards one another. A sliding friction can therefore be generated in the area of the support, even if strong rolling forces are generated by the rollers in the movement/rolling pressure direction.

[0059] It is also possible to lubricate the surface of the radial guide 52 so as to reduce the wear of the contact surface with the radial guide 52. During the rolling process, the guide can be tracked upward in the direction of the axis 46 of the workpiece 14, so as to reduce the load on the radial guide 52. It is also envisaged chat a multi-part guide can be used, which can adapt to the various stages of the reshaping process, in particular in the area of the valve head. It is also envisaged that instead of a rigid guide, a series of rollers can be used, which can be operated with less wear. The rollers can be moved in the axial direction in order to avoid local deformation of the workpiece by the guide rollers.

[0060] Above the workpiece, a heating element can be mounted opposite the radial guide 52, which heats the workpiece 14 by flame, radiation or induction, so as to ensure that hot rolling occurs throughout the whole of the reshaping process.

[0061] In the rolling method used, the workpiece 14, before the rolling process in the axial direction, can be displaced upwards until it is flush with the upper edge of the forming rollers. However, it is also possible to move the workpiece 14 upwards in the direction of the valve stem end during the rolling process, until the valve stem end is flush with the upper edge of the forming rollers.

[0062] Provision can also be made to drive the workpiece 14 by means of the clamping chuck, so as to achieve a slippage between the forming rollers 42 and the workpiece 14, in particular in the area of the valve disk, more particularly, the rear face of the valve disk. Since the rear face of the valve disk has a smaller surface area than the outer surface area of the valve stem, it seems advisable to generate a slippage between the rear face of the valve disk and the corresponding sections of the forming rollers 42, since otherwise the valve could be destroyed as a result of the torsional forces between the rear face of the valve disk and the valve stem. The angular velocity ratios between stem and valve disk are here at least as large as the corresponding radii ratios between valve stem and valve disk. With a ratio of the valve disk to valve stem diameter of about 5, in each case a ratio of the angular velocities for the average diameter of the valve disk to the stem diameter of about 2.5 ensues, which in a normal rolling process would be sufficient to turn or tear off the valve disk from the stem. Therefore, provision can be made to drive the workpiece 14 during form rolling at a higher speed in order to produce a slippage in the area of the valve disk, which significantly offloads the transition section from the valve disk to the valve stem and can thus prevent destruction of the workpiece 14 during form rolling. For this purpose the clamping chuck can set into rotation by a separate drive, not shown, if the latter is provided.

[0063] Furthermore, the rolling device can be provided with a single-roller rotational speed control, which is shown in detail in FIG. 1B, so as to reduce the wear on the radial guide 52. This is shown in detail in FIG. 1B. In order not to make FIG. 1A too confusing, the controller is not shown in the latter.

[0064] FIG. 1B shows the same elements as FIG. 1A, namely the forming rollers 42 and a finished form-rolled workpiece 14A, wherein the forming rollers 42 are shown in a position at the end of the rolling process. The depiction is purely schematic. The forming rollers 42 have reshaped the workpiece 14 into a reshaped workpiece 14A. The reshaped workpiece 14A still has a through-hole 28, which extends through the whole of the valve stem.

[0065] The form rolling device of FIG. 1B is provided with a load cell 66 for at least one radial guide 52, so as to measure the force with which the workpiece is pressed by the forming rollers 42 against the radial guide 52. The form rolling device of FIG. 1B is also provided with individually driven forming rollers 42 which can be activated individually at a selected rotational speed. The load cell or force sensor 66 is connected to a controller 68, which controls at least the rotational speed, that is to say, the drive, of one of the forming rollers 42, so as to limit the force that the workpiece 14/14A exerts on the radial guide 52 during the rolling process. Provision can also be made for the controller to control a rotational speed, more particularly, that of the workpiece, in order to reduce or at least limit the load on the radial guide 52.

[0066] Here the workpiece is held centrally between the two rollers by means of a differential activation of the forming rollers, or in another position, such that the load and the wear on the guides 52 can be minimised. The system can also be used in the case of rolling devices with two guides. By means of an appropriate controller, the service life of the rolling device can also be increased, since the intervals at which the guides must be replaced can be extended.

[0067] Although the controller for limiting the load on the radial guide 52 is described only in conjunction with FIG. 1B, it is explicitly emphasised here that the said controller should also be regarded as disclosed in the case of the other embodiments that are shown in the figures. The controller has been described only in FIG. 1B, as redundant repetition would only have increased the length of the description unnecessarily.

[0068] FIG. 1C shows the finished reshaped workpiece 14A, which comprises a part that essentially forms a valve body. The valve body has a valve stem 8, which at a lower end runs out into a valve disk 6, more particularly, the rear face 24 of a valve disk. The valve body does not yet comprise a valve disk face. The upper part of the valve stem 8 terminates in the stern end 36, with which the valve can later be activated. As illustrated, the stem end can be produced in the course of the form rolling process; however, it is also possible to shape the stem end 36 at a later stage.

[0069] The through-hole 28 has been reshaped into the cavity 10 in the valve disk 6 and the valve stem 8. It is also possible to produce just the cavity 10 by reshaping and later to bring the valve stem to a final diameter by a machining process, should it not be possible to achieve the parameters of the diameter of the through-hole 28, or blind hole, and the wall thickness of the workpiece, before and after the form rolling process.

[0070] The workpiece can be separated from the tubular remnant along the dotted line that forms the separation line 30. On the valve disk face there is still an opening 18, which can be closed at a later stage with a cover so as to form a finished valve.

[0071] FIG. 1D shows the finished valve 4 produced by means of reshaping. The valve body has a valve stem 8, which at a lower end runs out into a valve disk 6, more particularly, the rear face 24 of a valve disk. The opening 18 on the valve disk face 22 is closed by a cover 20, which has been bonded to the valve by friction welding, resistance welding, electron beam welding, or laser welding on a joint line 32.

[0072] The cavity 10 is filled with a sodium coolant 12. The coolant used is usually sodium, which is in a liquid state at the operating temperatures of the internal combustion engine. Usually it is not the entire cavity 10, but only , , , to of the cavity of the valve that is filled with sodium. In operation, the sodium in the valve stem 8, that is to say, in the cavity 10 of the valve stem 8, moves up and down and thereby transports heat from the valve disk 6 in the direction of the cooled valve stem S (shaker cooling). The sodium moves within the valve 2 during each opening and closing operation. The cavity 10 has been produced in the valve 2 in that the valve disk 6 has been provided on the valve disk face 22 with an opening 18.

[0073] FIG. 2A corresponds essentially to FIG. 1A. A description of reference symbols and elements that have already been described in connection with FIG. 1A will not be repeated here. Instead of a tubular workpiece 14, a cup-shaped workpiece 16 is now used, in which a base already forms the valve disk 6, that is to say, the valve disk face 22. Instead of a through-hole a blind hole 26 is used.

[0074] The diameter of the workpiece 16 is larger in the area of what is later the valve disk than in the area of what is later the valve stem 8. The workpiece already has, either essentially or precisely, the height of the later valve. Here the valve stem is formed essentially by form rolling. The valve disk can already be shaped to a large extent by a machining process. The cup-shaped workpiece 16 is held in the axial direction by an axial guide 54 so as to be able to form the rear face of the valve disk. Provision is also made to provide the cup-shaped workpiece 16 with a shoulder on which a clamping chuck can engage, so as to be able to rotate the cup-shaped workpiece during form rolling at a speed that can be selected. This was already explained in the description of FIGS. 1A and 1B. With a shoulder that is held in a clamping chuck, a slippage between the valve disk and the forming rollers can be achieved. The shoulder can be removed after the form rolling by a machining process.

[0075] In contrast to the embodiment of FIG. 1A, the wall thickness of that part of the cup-shaped workpiece 16, which later forms the valve stem, can be made thinner, which at a later stage results in a smaller wall thickness for the valve stem. Furthermore, in this design, the cup-shaped workpiece 15 is less strongly reshaped than the workpiece of FIGS. 1A/1B.

[0076] In FIG. 2B, the valve is already finished to a large extent after the form rolling. The cavity 10 has a large diameter in the area of the valve disk, which can be expected to result in improved cooling properties. The stem has a smaller wall thickness than in the case of FIG. 1B. By virtue of the lower degree of reshaping it is possible to roll the stem without it becoming necessary to reduce the outer diameter of the valve stem in a further machining process step.

[0077] FIG. 2C illustrates an internally cooled valve 4 in accordance with the invention, which has a valve stem that terminates at its lower end in a valve disk. The upper part of the valve stem 8 terminates in a stem end 36. Internally the valve is provided with a cavity 10, which is filled with a coolant 12. The cavity can, for example, be filled with the coolant through an opening or bore in the valve stem. In the area of the valve disk the inventive valve has a cavity with a large diameter, which can exceed the diameter of the valve stem. Here the valve disk, with the valve disk face 22, the rear of the valve disk 24, and the valve stem, are formed from one piece. The finished valve therefore has no joint lines, either in the area of the valve disk or in the area of the lower valve stem. It is possible to close the cavity 10 by means of a valve stem end attached, for example, by means of friction welding, after it has been filled with coolant.

[0078] FIG. 3A illustrates essentially the form rolling device of FIG. 2A. A description of reference symbols and elements that have already been described in connection with FIGS. 1A or 2A will not be repeated here. In contrast to the forming rollers of FIG. 2A, the forming rollers of FIGS. 3A are provided with a surface structure 58, which, during the forming rolling process, causes a transport of the workpiece material in the axial direction. The surface structure 58, which causes a transport of the workpiece material in the axial direction, is designed here as a thread pattern, which, with the rotation of the forming rollers 42, generates an axial force in the direction of what is later a valve stem end. With the surface structure, it is possible to use a shorter cup-shaped workpiece 16. In the form rolling process, a force is also exerted in the axial direction onto the cup-shaped workpiece, as a result of which the material during the rolling process can spread not only in the radial direction but also in the axial direction.

[0079] Here the surface structure 58 is embodied as a thread pattern. The thread pattern is designed with a small flank height and a small pitch, which only exerts forces, and does not roll a screw thread into the valve stem.

[0080] When the forming rollers exert a pressure on the cup-shaped workpiece 16, the material can flow not only in the circumferential and radial directions, but also, as a result of the axial forces, is able to flow, that is to say, to deform, in the axial direction. In overall terms this effect results in an ability to start with a cup-shaped workpiece with a larger wall thickness, which can significantly increase the process reliability of the method.

[0081] It is, of course, also possible to provide only one of the forming rollers with the surface structure 58, which causes transport of the workpiece material in the axial direction, or generates an axial force in the workpiece.

[0082] FIG. 3B illustrates the rolling process for the cup-shaped workpiece 16 in the direction of the valve stem end, wherein the material displacement is indicated by thin arrows.

[0083] FIGS. 3A and 3B can operate without an axial guide if the surface structure 58 generates a sufficiently large axial force to deform the rear of the valve disk face 24 by form rolling.

[0084] FIG. 3C shows a valve 4 that has been produced with the form rolling device of FIGS. 3A and 3B. It differs from the valve of FIG. 2C only in terms of the crystal structure of the material.

[0085] FIG. 4A corresponds essentially to FIGS. 1A to 3A. A description of reference symbols and elements that have already been described in connection with FIGS. 1A to 3A will not be repeated here.

[0086] FIG. 4A utilises the same short cup-shaped workpiece 16 as is shown in FIGS. 3A and 3B. Instead of cylindrical rollers, the axes of which are aligned parallel to one another, the embodiment of FIG. 4A and FIG. 4B uses hyperboloidal forming rollers 44, whose axes are skewed relative to one another. The rolling method represents an skewed rolling method, because the axis of at least one of the forming rollers is inclined with respect to the axis of the cup-shaped workpiece. Technically, the axes of the rollers are skewed relative to one another, wherein an angle between the axes can be specified as the angle in an orthogonal projection of the axes. Here the axes 48 of the forming rollers are each inclined at the same angle to the axis 46 of the cup-shaped workpiece 16. As a result of the inclination and rotation an axial force is generated in the direction of what is later the valve stem end during the rolling process. Thus a similar effect, can be produced as with the surface structure 58 in FIGS. 3A and 3B. It is also possible, of course, to equip the forming rollers of FIGS. 4A and 4B with an appropriate surface structure 58, such as was disclosed in FIGS. 3A and 3B. The forming rollers 44 form single-shell rotational hyperboloids, whose generators are not straight lines, but the profile of an inlet or outlet valve. Cylindrical rollers would not produce a cylindrical product, but rather a single-shell hyperboloid, since the separation distance between the axes of the rollers increases with the distance from the smallest separation distance. To compensate for this effect, the rollers themselves must have the shape of a single-shell hyperboloid. In skewed form rolling the rollers must also have the profiling of the final product, and thus form profiled single-shell hyperboloidal surfaces.

[0087] In contrast to the embodiments of FIGS. 1A to 3B, the workpiece is here guided by two opposing radial guides 52, which guide the cup-shaped workpiece 16 between the hyperboloidal skewed rollers 44. The guides must also be tracked during the form rolling process. Here it is also in particular possible to use the single-roller controller of FIG. 4B in the rolling device of FIGS. 4A and 4B.

[0088] The workpiece can be guided by an axial guide 54, but can also be held, guided and/or rotated, by a clamping chuck via a shoulder.

[0089] As in FIG. 1B, both radial guides 52 can each be provided with at least one load cell 66, each of which is connected to a controller 68, which in turn controls the rotational speed, that is to say, the drive, of at least one of the forming rollers 44. Here again, the controller can be used for the purpose of holding the workpiece 16 accurately between the rollers 44 and/or reducing the wear on the radial guides 52.

[0090] FIG. 4A illustrates the hyperboloidal forming rollers 44 in a final position after the form rolling process. When using hyperbolic forming rollers, torsional forces are generated in the stem, which are smaller at lower roller axis angles.

[0091] The larger the angle between the roller axes 48, the greater is the axial force generated.

[0092] The embodiment of FIGS. 4A and 5B can also operate without an axial guide, since a sufficiently large axial force is generated by the skewed rollers. It is also possible to deploy the surface structure 58 of FIGS. 3A and 3B in order to increase further the axial force generated during the rolling process.

[0093] FIG. 5A illustrates a combination of FIGS. 1A, 2A, 3A and 4A. As in FIG. 1A, the cup-shaped workpiece is only guided from one side by means of a radial guide 52. The left-hand forming roller 42 has the same shape as in FIGS. 1A and 2A, and the axis of the left-hand forming roller 42 is aligned parallel with the axis of the cup-shaped workpiece 16. The left-hand forming roller is designed as a hyperbolic forming roller 44, as in FIG. 4A. The hyperbolic forming roller 44 is also provided with the surface structure 58 of FIGS. 3A and 3B. The axis 50 of the hyperbolic forming roller 44 is inclined relative to the axis 48 of the left-hand forming roller 42 and the axis 46 of the cup-shaped workpiece. Thus, during the form rolling process the right-hand hyperbolic forming roller 44 generates a strong axial force in the direction of what is later the valve stem end. With a suitable design this axial force is sufficient to elongate a short cup-shaped workpiece 16 in the axial direction during the form rolling process.

[0094] FIG. 5B illustrates the rolling device at the end of the rolling process. In FIG. 5B the hyperboloidal forming rollers 44 are located in a final position after the form rolling process. As a result of the shape of the rollers, the left-hand hyperbolic forming roller 44 covers the upper valve stem end of the rolled valve. The shape of the rollers also causes the valve disk to cover the lower part of the left-hand hyperbolic forming roller 44. Likewise the right-hand hyperbolic forming roller 44 partially covers the valve disk of the reshaped workpiece 16A. The valve stem end covers the upper part of the line of contact of the right-hand hyperbolic forming roller 44 with the valve stem end.

[0095] With the one-sided guidance by the radial guide 52, the possibility arises of installing a heater opposite the radial guide 52, which heats the cup-shaped workpiece by way of, for example, an induction heater or a gas heater, so as to hold the workpiece 16 within a temperature range in which hot rolling, more particularly, hot skewed form rolling, is possible.

[0096] FIGS. 6A and 6B illustrate a further additional embodiment of a workpiece and an internally cooled valve. The workpiece that is shown in FIG. 6A corresponds essentially to the workpiece of FIG. 2A. In contrast to the workpiece of FIG. 2A the workpiece of FIG. 6A is provided with an outer contour 70. As in FIG. 2A, the blind hole 26 is designed as a cylindrical hole. The outer contour 70 together with the cylindrical blind hole 26 produces a thickness variation of the stem.

[0097] As a result of the reshaping process the outer surface of the stem is reshaped so as to be essentially cylindrical. Here the outer contour 70 is flattened and transferred inwards to the inner face of the blind hole 26, wherein an inner contour is formed internally in the blind hole. The thickness variation of the stem is essentially maintained, wherein the contour after the reshaping process is now formed on the inner face, i.e. in the cavity 10, as an inner contour 72. Here the inner contour is designed such that it forms a Laval nozzle at the transition section between the valve disk 6 and the valve stem 8. It should be understood that other inner contours can be generated using this method. It should likewise be understood that this principle can also be applied to the embodiments in which an elongation of the shank is also achieved during the reshaping process, as for example in FIGS. 3, 4 and 5. A to C respectively. At the same time just a broadening and flattening of the contour in the axial direction must also be considered. By this method it is easily possible to achieve shaped cavities 10 with good flow characteristics, which allow a conical transition between the stem and the valve disk. It can also be desirable to generate nozzle shapes, such as the Laval nozzle illustrated in the cavity 10. With this method, it is possible using very simple technical measures to generate almost any smooth or continuous inner contours 70.

[0098] It should be noted that all combinations of features of FIGS. 1A and 1B, to 5A and 5B, should also be considered as disclosed, inasmuch as they can be technically implemented. This relates in particular to the control or regulation of the individual roller speeds as a function of forces that have been measured on at least one radial guide. Furthermore, configurations are planned with one-sided and two-sided support by means of radial guides for all embodiments.

REFERENCE LIST

[0099] 4 Inventive internally cooled valve [0100] 6 Valve disk [0101] 8 Valve stem [0102] 10 Cavity [0103] 12 Coolant [0104] 14 Tubular workpiece [0105] 14A Reshaped tubular workpiece [0106] 16 Cup-shaped workpiece [0107] 16A Reshaped cup-shaped workpiece [0108] 18 Opening [0109] 20 Cover [0110] 22 Valve disk face [0111] 24 Rear of the valve disk [0112] 26 Blind hole [0113] 28 Through-hole [0114] 30 Separation line [0115] 32 Joint line [0116] 36 Stem end [0117] 42 Forming roller [0118] 44 Hyperbolic forming roller [0119] 46 Workpiece axis [0120] 48 Forming roller axis [0121] 50 Hyperbolic forming roller axis [0122] 52 Guide/radial guide [0123] 54 Axial guide [0124] 56 Clamping chuck [0125] 58 Surface structure that causes a transport of the workpiece material in the axial direction [0126] 60 Direction of rotation [0127] 62 Direction of movement/roller pressure [0128] 64 Stub axle [0129] 66 Load cell [0130] 68 Control of the forming rollers rotational speeds [0131] 70 Outer contour [0132] 72 Inner contour