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.

Description

BACKGROUND

1. Technical Field

The present invention relates to a manufacturing method for manufacturing an internally cooled valve, a cooling structure being mounted in a cavity of the valve, on the valve base. The present method further relates to a valve that has been manufactured using the method according to the invention.

2. Related Art

Internally cooled valves have been known for quite some time, in which a cavity extends in the valve stem, and in which via so-called “shaker cooling,” sodium transports heat from a valve head in the direction of the valve stem, which is cooled by the engine head.

It is likewise known to arrange cooling structures, via insertable valve bases, inside the cavity to improve heat transfer from the valve base to the coolant in the cavity. However, due to the fact that the material of the valve is weakened by a weld seam that joins a separate valve base to the valve head, valve failure and significant engine damage may occur when the weld seam fails and coolant escapes into the combustion chamber, or the entire valve base falls into the combustion chamber. In addition, welding represents a technically complicated and costly processing step.

A method is known from Japanese Patent application JP 2016084725 A in which a valve blank is produced by rotary swaging, wherein a structure may be mounted on an inner side of a disk surface beforehand.

A method is known from European Patent application EP 2811126 A1 in which a valve blank is formed from a semifinished product by drop forging, the stem of the semifinished product being tapered in subsequent steps.

A method is disclosed in U.S. Pat. No. 2,328,512 A, with which a valve base of an internally cooled valve may be provided with a structure by means of a stamping operation.

U.S. Pat. No. 2,280,758 relates to an internally cooled valve having a structure on an inner side of the valve disk which is intended to divert the coolant in the direction of an outer side of the valve,

Patent documents CN 202645663 U and DE 102015116009 B3 relate to internally cooled valves having a cavity that is closed by a cover on the valve disk surface.

German Patent application DE 102015118495 A1 discloses a method for forming disk-shaped blanks by deep drawing and pressing to form a valve.

SUMMARY

Therefore, it is desirable to have a method with which a cooling structure may be mounted on an inner side of a coolant cavity in the area of the valve base, without the need for separate weld seams in the area of the valve base or the valve head.

According to the present invention, a manufacturing method for an internally cooled valve is provided which encompasses providing a semifinished product having an at least partially cylindrical exterior, and creating or deepening an at least partially cylindrical cavity in the semifinished product by heat forming, using a stamp, thus producing a valve blank. According to the invention, the method is characterized in that the end face of the stamp is provided with at least one recess via which a structure is formed on a base of the cavity during the forming. The cooling structure is thus impressed into the inner side of a valve base from above, through an area that is subsequently formed into a valve stem. At a later time, the portion that subsequently forms the valve stem is reduced in diameter, so that a cavity is present in the subsequent valve, which has a larger diameter in the valve head than in the valve stem. By use of this method, any type of weld seam in the area of the valve head or the valve base may be dispensed with. In brief, the method may be described as impressing a structure into the cavity in the area of the valve base, followed by a step of forming a portion of the valve blank into a valve stem, without substantially changing the structure in the valve base.

This initial step may be directly applied during forming from a disk-shaped or cylindrical semifinished product, the disk-shaped or cylindrical semifinished product being formed into a bowl-shaped valve blank. However, for a semifinished product that is already bowl-shaped, it is also possible in a further machining step to impress the cooling structure into the valve base, and likewise to at least partially deepen the depression.

In one exemplary embodiment of the manufacturing method for an internally cooled valve, the forming encompasses backward extrusion. In such a design, a valve blank may be pressed from an essentially cylindrical or disk-shaped semifinished product in a single step. Further machining steps are then used to form a valve or disk valve from the valve blank, and a coolant such as sodium is introduced into the cavity of the valve or disk valve.

In another exemplary embodiment of the manufacturing method, the forming encompasses forging. A valve disk may likewise be integrally formed by forging as well as by backward extrusion.

In an additional embodiment of the manufacturing method, the structure includes cooling ribs that extend in a circular or star shape. The cooling ribs extend in a circular or star shape from an axis of the valve blank.

Another embodiment of the manufacturing method uses a stamp which presses a structure, in the form of pins, cones, or truncated cones, into the cavity at the valve base, which act as cooling elements. In particular cooling elements having the shape of a rod, cone, or truncated cone may allow high heat transfer due to their large surface area. It is likewise provided to preferentially use truncated cones at an edge of the piston base, and to use conical cooling elements in the middle. A conical cooling element situated on the axis of symmetry of the valve or valve blank may also achieve rerouting of the coolant flow from a movement in an axial direction to a movement in a radial direction, toward the disk edge, to improve the cooling of the valve head.

In another embodiment of the manufacturing method, the structure includes guide blades which can set a coolant in the valve, moving in the cavity, into rotation about an axis of symmetry of the valve. The guide blades may be arranged similarly as with a radial compressor turbine.

In another embodiment, the method may also include integral forming of a valve head onto the valve blank during or after the forming. A lower portion of the semifinished product or valve blank is hereby broadened and shaped into a valve disk or valve disk edge.

In another embodiment of the manufacturing method for an internally cooled valve, after the valve head is formed, a diameter of the valve blank next to the valve head is reduced in the axial direction, thus forming a valve stem. The bowl-shaped valve blank must undergo further forming in order to be used as a disk valve. The invention is based on the fact that a depression having a large diameter, larger than the subsequent valve stem diameter, is pressed into a semifinished product, wherein a structure that improves cooling of a subsequent valve base is pressed in at the base of the depression. It is particularly advantageous when the subsequent cavity in the valve has a particularly large diameter to allow a particularly large amount of heat to be absorbed by the valve base. Due to the large diameter of the depression, the proposed method allows cooling structures to be mounted or impressed on the inner side of the valve base, since at this location a small ratio of diameter to height of the stamp allows a large transmission of force. This is not possible with conventional hollow valves, since the stamp that is necessary for this purpose has a length-to-diameter ratio that is too unfavorable, and during a stamping operation could yield to the side.

In another embodiment of the manufacturing method for an internally cooled [valve,] the valve stem is formed by section rolling or rotary swaging, preferably by hot hammering or cold hammering on a mandrel. The forging tool imparts radial blows to the workpiece, resulting in a smaller cross section of the machined workpiece. Elongation of the material results in higher quality than with machining. By using mandrels, it can be ensured that a cavity in the interior of the workpiece has a desired inner diameter.

In another embodiment, the manufacturing method includes rolling or cross wedge rolling on a mandrel, the valve stem being formed by the rolling.

According to another aspect of the present invention, an internally cooled valve is provided that has been manufactured using one of the above methods.

THE DRAWINGS

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

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

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

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

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.

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

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.

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.

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.

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.

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.

The claims define the scope of protection.

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.