METHOD FOR PRODUCING A COOLING CHANNEL PISTON AND COOLING CHANNEL PISTON PRODUCED BY SUCH A METHOD

Abstract

A method for producing a cooling channel piston may include producing a salt core blank by pressing and sintering a pure salt material having a surface roughness R.sub.z of at most 60 μm. The method may also include one of immersing the salt core blank into a saturated solution of the salt material, or spraying the salt core blank with a saturated solution of the salt material. The method may also include drying the salt core blank to form a salt core having a surface roughness R.sub.z of at least 200 μm. The method may further include placing the salt core in a casting mold, and casting the cooling channel piston from a metallic casting material.

Claims

1. A method for producing a cooling channel piston, comprising: producing a salt core blank by pressing and sintering a pure salt material having a surface roughness R.sub.z of at most 60 μm; one of: immersing the salt core blank into a saturated solution of the salt material, or spraying the salt core blank with the saturated solution of the salt material; drying the salt core blank to form a salt core having a surface roughness R.sub.z of at least 200 μm; placing the salt core in a casting mold; and casting a cooling channel piston from a metallic casting material.

2. A method for producing a cooling channel piston, comprising: producing a salt core blank by pressing and sintering a pure salt material having a surface roughness R.sub.z of at most 60 μm; one of: immersing the salt core blank into one of a solvent and a solution of the salt material, or spraying the salt core blank with the one of a solvent and a solution of the salt material; sprinkling the salt core blank with a salt material having at least one of a defined grain size distribution and a defined grain diameter distribution; drying the salt core blank to form a salt core having a surface roughness R.sub.z of at least 200 μm; placing the salt core in a casting mold; and casting a cooling channel piston from a metallic casting material.

3. The method as claimed in claim 1, wherein the salt material is sodium chloride.

4. The method as claimed in claim 1, wherein producing the salt core blank includes subjecting the soft core blank to mechanical finishing.

5. The method as claimed in claim 1, wherein the saturated solution includes at least one of solvent water and at least one polar organic solvent from a group including methanol, ethanol, isopropanol, diethyl ether, and acetone.

6. The method as claimed in claim 5, wherein the at least one polar organic solvent includes at least one crown ether.

7. The method as claimed in claim 1, wherein drying the salt core blank is done in agitated air.

8. The method as claimed in claim 1, wherein drying the salt core blank occurs at a temperature of at most 200° C.

9. The method as claimed in claim 7, wherein drying the salt core blank occurs at room temperature.

10. The method as claimed in claim 1, wherein the surface roughness R.sub.z of the salt core is up to 1 mm.

11. The method as claimed in claim 1, further comprising heating the salt core blank to a temperature of 80° C. to 100° C. after producing the salt core blank.

12. The method as claimed in claim 1, further comprising heating the salt core to a temperature of 300° C. to 500° C. before placing the salt core in the casting mold.

13. The method as claimed in claim 1 wherein the casting material is aluminum-based.

14. A cooling channel piston produced by a process comprising: producing a salt core blank by pressing and sintering a pure salt material having a surface roughness R.sub.z of at most 60 μm; one of: immersing the salt core blank into one of a solvent and a solution of the salt material, or spraying the salt core blank with the one of a solvent and a solution of the salt material; drying the salt core blank to form a salt core having a surface roughness R.sub.z of at least 200 μm; placing the salt core in a casting mold; and casting the cooling channel piston from a metallic casting material.

15. A cooling channel piston comprising a circulating cooling channel accommodated in a piston head, wherein a surface of the cooling channel has a surface roughness R.sub.z of at least 200 μm.

16. The cooling channel piston as claimed in claim 15, the surface roughness R.sub.z of the surface of the cooling channel is up to 1 mm.

17. The method as claimed in claim 2, wherein the salt material is sodium chloride.

18. The method as claimed in claim 2, wherein producing the salt core blank includes subjecting the soft core blank to mechanical finishing.

19. The method as claimed in claim 2, wherein the one of a solvent and a solution saturated solution includes at least one of solvent water and at least one polar organic solvent from a group including methanol, ethanol, isopropanol, diethyl ether, and acetone.

20. The method as claimed in claim 2, wherein drying the salt core blank is done in agitated air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the drawings, in a schematic representation which is not true to scale:

[0026] FIG. 1 shows an exemplary embodiment of an inventive cooling channel piston in section;

[0027] FIG. 2 shows an exemplary embodiment of a salt core used for producing a cooling channel piston as per FIG. 1, in section.

DETAILED DESCRIPTION

[0028] The method of the invention is suitable for any desired types and designs of cooling channel piston. FIG. 1, for example, shows a one-piece cast cooling channel piston 10. The cooling channel piston 10 has a piston head 11 with a piston crown 12, in which a combustion depression 13 is made. The piston head 11 also has a fire land 14 and also a ring section 15 with ring grooves for accommodating piston rings (not shown). At the level of the ring section 15, the piston is provided with an encircling cooling channel 16. The piston, furthermore, in a conventional way, has a piston shaft 17 with piston bosses 18, which are provided with boss bores 19 for accommodating a piston pin (not shown). The piston bosses 18 are joined to one another in a conventional way via running surfaces 21.

[0029] As indicated schematically in FIG. 1, the encircling cooling channel 16 has a surface having a surface roughness R.sub.z of at least 200 μm, preferably of up to 400 μm, more preferably of up to 1 mm.

[0030] FIG. 2 shows a salt core 30 made of sodium chloride for use in the production of the inventive cooling channel piston 10 in accordance with FIG. 1. The salt core 30 has a salt core blank 31, whose surface 32 is covered with salt crystals 33 of sodium chloride.

[0031] In a first exemplary embodiment, the salt core 30 may be produced as follows:

[0032] The salt core blank 31 is first of all produced in a conventional way by cold pressing and sintering of a salt material such as sodium chloride. Care should be taken here to ensure that the pure salt material is used, i.e., a salt material which contains no extraneous substances or additives. After being sintered, the salt core blank 31 may be mechanically finished on its surface 32 in a known way to give a cross-sectional contour which is an extremely precise match for the cross-sectional contour of the cooling channel to be produced.

[0033] The completed salt core blank 31 is immersed into or sprayed with a saturated aqueous solution of the salt material, sodium chloride in the exemplary embodiment, so that its surface 32 is wetted by the solution. The salt core blank 31 is subsequently dried, in an oven, for example, at a temperature of just below 100° C., e.g. 95° C. to 98° C., until steam no longer emerges from the salt core blank. During the drying process, salt crystals 33 crystallize from the saturated solution and adhere to the surface 32 of the salt core blank 31.

[0034] After the end of the drying process, the resulting, completed salt core 30 is distinguished by a surface roughness R.sub.z of at least 200 μm.

[0035] For the production of the cooling channel piston 10, the salt core 30 is placed in a conventional way into a corresponding casting mold and is cast with a metallic material, based for example on aluminum. After the conclusion of the casting process, the resulting piston blank has a cast-in salt core 30. The piston blank is finished in a known way, and the salt core 30 is rinsed out with water. The result is the cooling channel piston 10 as per FIG. 1.

[0036] In a modification of this method, the salt core blank 31, before being immersed into the saturated solution, is heated to a temperature of 80° C. to 100° C., in order to obtain particularly effective wetting of the surface 32 of the salt core blank 31 by the saturated solution.

[0037] In a second exemplary embodiment, the salt core 30 may be produced as follows:

[0038] First of all, as described above, a salt core blank 31 is produced. This blank is sprayed with a suitable solvent, preferably water, or with a solution of the salt material, preferably sodium chloride, or is immersed into the liquid in question. The surface of the salt core blank 31, which is still wet, is subsequently sprinkled with crystals of the salt material, sodium chloride in the exemplary embodiment, and is subsequently dried and used further as described. The grains used have a defined grain size distribution and/or a defined grain diameter distribution.

[0039] With this measure it is possible to set the surface roughness R.sub.z of the salt core 30 with particular precision. For example, after using salt crystals with an average grain size of 500 μm, it was possible to measure a surface roughness R.sub.z of 200 μm to 400 μm on the surface of the cooling channel 16 of the completed cooling channel piston 10. Salt crystals having an average grain diameter of 1 mm produced a surface roughness R.sub.z of 700 μm to 900 μm on the surface of the cooling channel 16 of the completed cooling channel piston 10.