PROCESS FOR MANUFACTURNIG AN INTERNALLY COOLED VALVE HAVING A COOLING STRUCTURE, AND VALVE MANUFACTURED BY SAID METHOD

Abstract

The invention relates to a process for manufacturing an internally cooled valve, said process involving providing an externally at least partly cylindrical semifinished product (2), creating or increasing the depth of an at least partly cylindrical cavity in the semifinished product (2) in a hot-working procedure using a male die such that a valve blank is formed; during the hot-working procedure, a recess on an end face of the male die forms a structure on the bottom of the cavity.

Claims

1-11. (canceled)

12. A method for producing a valve blank for an internally cooled valve, comprising providing a semifinished product having an at least partially cylindrical exterior, and creating an at least partially cylindrical cavity in the semifinished product by heat forming, using a stamp, thus producing a valve blank, wherein the hot forming encompasses backward extrusion, wherein a structure is formed on a base of the cavity during the hot forming via a recess at n end face of the stamp.

13. The method for producing a valve blank according to claim 12, wherein the structure includes cooling ribs that extend in a circular or star shape.

14. The method for producing a valve blank according to claim 12, wherein the structure includes pins, cones, or truncated cones that act as cooling elements.

15. The method for producing a valve blank according to claim 12, wherein the structure includes blades that are able to set a coolant in a valve into rotation.

16. The method for producing a valve blank according to claim 12, wherein a valve head is formed onto the valve blank during the hot forming.

17. A method for manufacturing an internally cooled valve, wherein after the valve head is formed according to claim 16, a diameter of the valve blank next to the valve head is reduced in the axial direction in order to form a valve stem.

18. The method for manufacturing an internally cooled valve according to claim 17, wherein the valve stem is formed by rolling or rotary swaging.

19. The method for manufacturing an internally cooled valve according to claim 17, wherein the valve stem is formed by rolling or cross wedge rolling.

20. An internally cooled valve that is manufactured using a method according to claim 12.

21. The method for manufacturing an internally cooled valve according to claim 17, wherein the valve stem is formed by hot hammering or cold hammering on a mandrel.

22. The method for manufacturing an internally cooled valve according to claim 19, wherein the valve stem is formed by rolling on a mandrel.

Description

THE DRAWINGS

[0023] The present invention is explained below with reference to non-limiting, schematic figures.

[0024] FIGS. 1A through 1F illustrate sectional views of various segments for manufacturing an internally cooled valve according to the invention.

[0025] Identical or similar reference numerals are used in the description and in the figures to refer to identical or similar components or elements.

[0026] FIG. 1A shows a sectional view of a cylindrical semifinished product 2 that is used as the starting material for manufacturing an internally cooled disk valve.

DETAILED DESCRIPTION

[0027] FIG. 1B shows a sectional view of a semifinished product 45 that is formed in the shape of a bowl. The bowl-shaped, formed semifinished product 4 has been formed in the shape of a bowl from above by a stamp, not illustrated. The forming may be carried out as hot forming or cold forming. In the present case, backward extrusion has been used, as the result of which the height of the formed semifinished product 4 has increased greatly compared to the unformed semifinished product 2 from FIG. 1. Recesses present on the stamp have been impressed as ribs or elevations on the base of the formed cavity. These ribs or elevations form a cooling structure 6 via which the surface of the depression is significantly increased, with the aim of increasing heat transfer from a subsequent valve base to a coolant.

[0028] A favorable diameter-to-length ratio allows use of backward extrusion without the risk of the stamp undergoing lateral deformation.

[0029] FIG. 1C shows the bowl-shaped, formed semifinished product 4 that has been further formed into a first valve blank 8. A similar stamp may be used to form a valve head 16 by lateral extrusion and backward extrusion, the cooling structures 6 still being situated in the depression. As the result of the lateral extrusion, the diameter of the first valve blank 8 in the area of the valve head 16 may be increased, and in this step the thickness of the valve base 18 is also greatly reduced. Via a backward extrusion component, it is possible at the same time to increase the length of a stem section 20, wherein the diameter of the stem section is not increased.

[0030] It is likewise possible to form the semifinished product from FIG. 1A directly into the first valve blank 8. Thus, the first valve blank 8 may also be formed from an essentially cylindrical semifinished product in a single step, wherein in such a method the step illustrated by FIG. 1B is skipped or omitted.

[0031] FIG. 1D shows the first valve blank 8, which has been further machined by rolling, cross wedge rolling, or hammering in the stem area 22 in order to decrease the diameter of the stem and increase the length of the stem, for which reason a second valve blank 10 has been produced. In this machining step as well, there is little or no deformation of the cooling structures 6.

[0032] FIG. 1E shows the second valve blank 10 from FIG. 1D, which has been further machined by rolling, cross wedge rolling, or hammering in the stem area 24, as the result of which the diameter of the stem 24 has been further decreased, and the length of the stem 24 has been further increased. Due to these work steps, the second valve blank 10 has been formed into a third valve blank 12. In this machining step as well, there is little or no deformation of the cooling structures 6 in the area of the valve base 18 of the cavity 30.

[0033] FIG. 1E shows the third valve blank 12 after further machining by rolling, cross wedge rolling, or hammering in the stem area 24, and in the transition to the valve disk 16. An outer diameter of the valve stem 26 may be brought to, or virtually to, the final dimensions in the last step. The stem or the cavity 32 or the depression may now be filled with a coolant (not illustrated), and the cavity closed. Reducing the diameter of the stem 26 also increases the length of the stem 26 up to or beyond the final dimensions. In addition, the stem and the valve head may undergo final machining or grinding. The cooling structures 6 in the area of the valve base 18 of the cavity 30 have also been easily formed during the last work steps. Overall, however, a fairly large cavity that is additionally provided with cooling structures 6 still remains in the area of the valve head 16, and the cooling structures allow greater heat transfer from the valve base to a coolant in the cavity 32.

[0034] The claims define the scope of protection.