Piston of an Internal Combustion Engine Having Alkali Metal Cooling and Method for Production Thereof

Abstract

The invention discloses a method for producing an internal combustion engine piston having at least one cavity which is filled with an alkali metal cooling medium and is subsequently closed. The at least one cavity longitudinally extends from a central point into the piston body toward the piston circumference. The invention further discloses a piston produced according to the method.

Claims

1. A method for the production of a piston (1) of an internal combustion engine, wherein at least one cavity (2) is formed in the piston (1), wherein the at least one cavity (2) is filled with a cooling medium alkali metal, and is subsequently closed, wherein the at least one cavity comprises forming at least two cavities (2) from a central point (10) of the piston (1); and closing the cavities (2); after filling in of the cooling medium alkali metal in the region of the central point (10).

2. The method as claimed in claim 1, wherein the central point (10) is formed in a region of a subsequently formed combustion chamber bowl (5).

3. The method of claim 1 wherein the central point (10) is formed through one of boring a hole or milling.

4. The method claim 2 wherein the at least two cavities (2) each comprise an axis that intersect at a common point in a central region.

5. The method of claim 1 wherein the central point (10) is closed with a closure element (3) having corresponding geometry to the central point.

6. The method of claim 5 wherein each of the central point (10) and the closure element (3) comprises a lateral surface of a truncated cone.

7. The method of claim 6 wherein the central point (10) is closed through friction welding of the closure element (3) lateral surface to the central point lateral surface.

8. A piston (1) of an internal combustion engine, wherein the piston (1) has at least one closed cavity (2) which is filled with a cooling medium alkali metal, and subsequently closed, wherein the at least one closed cavity comprises at least two cavities (2) each extending into the piston (1) from a central point (10) of the piston (1); and the at least two cavities (2) are closed in a region of the central point (10) after filling in of the cooling medium alkali metal.

9. The piston of claim 8 wherein the at least two cavities (2) do not penetrate through an outer surface of a piston shaft of the piston (1).

10. The piston (1) of claim 8 wherein each of the at least two cavities (2) comprise an axis, the axes intersecting at a common point in a central region.

11. The piston (1) of claim 8 wherein the central point (10) is closed by a closure element (3) having a corresponding geometry to the central point.

12. A method for the production of a piston for use in an internal combustion engine, the method comprising: forming a central point defining a central bore in a piston blank; forming at least two cavities in communication with the central bore, each of the at least two cavities having an axis, each of the at least two cavity respective axis intersecting at a common point positioned in a central region; filling the at least two cavities with an alkali metal cooling medium; and closing the central bore with a single closure element thereby preventing the alkali metal cooling medium in each of the at least two cavities from exiting the respective cavity.

13. The method of claim 12 wherein forming the central point further comprises forming the central bore having truncated cone lateral side walls, the closure element having corresponding truncated cone lateral side walls.

14. The method of claim 13 wherein closing the central bore with the closure element comprises friction welding the closure element lateral sidewalls to the central bore lateral side walls.

15. The method of claim 12 wherein the filling of the at least two cavities comprises simultaneously filling the at least two cavities with the alkali metal cooling medium from the central point.

16. The method of claim 12 wherein forming the at least two cavities further comprises: forming the at least two cavities as elongate cylindrical cavities starting from a cavity opening at the central point and extending the cavities toward an outer circumference of the piston, the cavity having a closed end opposite the cavity opening at the central point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a lower view of a piston with a deep drill hole for receiving alkali metal from the prior art;

[0033] FIG. 2 shows a sectional view of a piston with a deep drill hole which is closed according to the prior art for receiving alkali metal;

[0034] FIGS. 3A to 3C show the sequence for incorporation of the cavity according to the invention for alkali metal into a piston;

[0035] FIGS. 4A and 4B show the creation of a closure according to the invention for the cavity for receiving alkali metals; and

[0036] FIG. 5 shows a cut-out of the piston with a closed cavity for alkali metals.

[0037] FIG. 1 shows a lower view of a piston 101 with a deep drill hole 102 for receiving alkali metal from the prior art. Each individual deep drill hole 102 must be countersunk and deep bored (to be carried out in the case of each individual bore). A bore 102 rotated in two directions in the region of forging skin 105 of a shaft 109 is represented.

[0038] FIG. 2 shows a deep drill hole 102 closed according to the prior art for receiving alkali metal. Deep drill hole 102 is closed by a closure plug 103 in a piston 101 from the prior art, which closure plug is fixed by a weld seam 104. Piston 101 furthermore has a combustion chamber bowl 106 as well as a cooling duct 107 and a bolt bore 108. Deep drill hole 102 is not connected to cooling duct 107. The deep drill hole is incorporated into piston 101 from the direction of shaft 109.

[0039] FIGS. 3A to 3C show the sequence for incorporating a cavity 2 according to the invention for receiving alkali metals into a piston 1.

[0040] FIG. 3A shows the preprocessed blank in the supplied state.

[0041] FIG. 3B shows a preprocessed central point 10 (in particular bored or milled). Said central point 10 is incorporated into a central region 8 (which penetrates through the piston stroke axis) of piston 1. Central region 8 lies within a later combustion chamber bowl 5. Central point 10 can have, for example, the configuration of a truncated cone, other geometrical forms also, however, being conceivable. The rotationally symmetrical surface which delimits central point 10 is embodied here as a lateral surface of a truncated cone.

[0042] FIG. 3C shows cooling bores incorporated at a right angle to preprocessed point 10 for formation of a cavity 2 which serves to receive alkali metal. It forms a reservoir for alkali metal.

[0043] FIGS. 4A and 4B show the creation of a closure according to the invention of cavity 2 for alkali metals. The closure of the at least one cavity 2 is carried out by a closure element 3. Said closure element 3 can be embodied as a truncated cone. It is important that closure element 3 has a corresponding geometry to central point 10. It is advantageous if both central point 10 and closure element 3 have a rotationally symmetrical configuration since this significantly simplifies jointing. For example, a friction welding method can be provided as a firmly bonded jointing method. Closure element 3 is fixed to the piston in a firmly bonded and/or non-positive and/or positive manner. Fixing of closure element 3 is preferably carried out in the region of central point 10. A lateral surface 11 in the lower region of closure element 3 is integrated positively into the lateral surface of central point 10. A covering surface 12 of the truncated cone-shaped portion of closure element 3 adjoins facing away from combustion chamber bowl 5. Its base surface is located at that end of the truncated cone-shaped portion of closure element 3 which is opposite covering surface 12. The upper region of closure element 3 which has a plurality of handling surfaces 13 on its circumference adjoins this base surface. Said handling surfaces 13 serve to securely receive closure element 3 in tools. If, for example, a friction welding process is used in order to fix closure element 3 undetachably in central point 10, the necessary torque can be transmitted via handling surfaces 13. In the case of later completion of piston 1, these handling surfaces 13 can be removed. Six handling surfaces 13 are preferably distributed evenly on the circumference of the upper region of closure element 3. In this case, a hexagonal bolt drive can be used to actuate closure element 3. It is, however, also conceivable to provide fewer handling surfaces 13 on closure element 3, for example, three or four or more handling surfaces 13 on closure element 3, for example, eight.

[0044] The jointing of central closure element 3 by friction welding is shown in FIG. 4A. A possible friction welding bead is formed on the circumference of the truncated cone-shaped portion of closure element 3 in the region of its base surface and/or its covering surface. In the region of the base surface of the truncated cone-shaped portion, the friction welding bead can be removed during completion of combustion chamber bowl 5, for example, by machining methods. In the same method step, the upper region of closure element 3 with handling surfaces 13 can also be changed in terms of its geometrical configuration or entirely removed.

[0045] FIG. 4B in turn shows the jointing of central closure element 3 by soldering, gluing, welding or the like. It is also conceivable to embody a thread between closure element 3 and central point 10. In this case, threads are machined into lateral surface 11 of closure element 3 and into the lateral surface of central point 10. The handling surfaces in the upper region of closure element 3 then serve to actuate this screw connection.

[0046] A cut-out of piston 1 with a closed cavity 2 for alkali metals is shown in FIG. 5. The multiple complex closure of individual deep drill holes is dispensed with as a result of the central closure with closure element 3. A forging skin 5A, which, however, does not have to be penetrated for production of the at least one cavity 2 is formed in the region of combustion chamber bowl 6. A radially circumferential cooling duct 7 is furthermore represented. Said cooling duct 7 receives a different cooling medium than is used in the at least one cavity 2. As a result of the spatial separation, it is ensured that no mixing through of the at least two cooling media (in particular oil and sodium) takes place.

[0047] The at least one cavity 2 is generated by a bore into a processed surface defined at a right angle to the bore axis (no separate spot facing required). The complex preparation for deep drill holes is dispensed with. No boring through a forged blank contour is furthermore required.

LIST OF REFERENCE NUMBERS

[0048] 1 Piston [0049] 2 Cavity [0050] 3 Closure element [0051] 4 Weld seam [0052] 5 Forging skin [0053] 6 Combustion chamber bowl [0054] 7 Cooling duct [0055] 8 Central region [0056] 9 Piston base body [0057] 10 Central point [0058] 11 Lateral surface [0059] 12 Covering surface [0060] 13 Handling surface [0061] 101 Piston from the prior art [0062] 102 Deep drill hole [0063] 103 Closure plug [0064] 104 Weld seam [0065] 105 Forging skin [0066] 106 Combustion chamber bowl [0067] 107 Cooling duct [0068] 108 Bolt bore [0069] 109 Shaft