WORKING PISTON FOR A RECIPROCATING PISTON INTERNAL COMBUSTION ENGINE AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A working piston for a reciprocating internal combustion engine having a piston head. In order to further reduce pollutant emissions, soot particle emissions and the fuel consumption of the reciprocating piston internal combustion engine, the piston head has a wave-like structure which is circular and which is arranged concentric to the longitudinal central axis of the working piston and has nanostructuring at least in regions.

Claims

1. A working piston for a reciprocating-piston internal combustion engine, comprising a piston crown, wherein the piston crown comprises an undulation structure which is of circular form and which is arranged concentrically with respect to the longitudinal central axis of the working piston and which is equipped at least in certain regions with a nanostructuring.

2. The working piston as claimed in claim 1, wherein a radial spacing of adjacent undulation peaks of the undulation structure amounts to between 0.8 and 1.2% of a diameter of the working piston.

3. The working piston as claimed in claim 1, wherein adjacent undulation peaks of the undulation structure are arranged with a radial spacing of between 5 and 150 m to one another.

4. The working piston as claimed in claim 1, wherein side flanks of at least one undulation peak of the undulation structure run at an angle () of approximately 50 to 65 with respect to one another.

5. The working piston as claimed in claim 1, wherein the nanostructuring is of undulating form and has a period which lies in a range from approximately 500 nm to approximately 1000 nm, in particular is approximately 700 nm.

6. The working piston as claimed in claim 1, wherein the undulation structure (4, 8, 16, 17, 21, 25) is of hydrophilic form at least in certain regions.

7. The working piston as claimed in claim 1, wherein at least one undulation peak of the undulation structure is of rounded or flattened form in cross section.

8. The working piston as claimed in claim 1, wherein a rounding of the rounded undulation structure has a radius of between 20 and 30 m.

9. The working piston as claimed in claim 1, wherein a height of at least one undulation peak of the undulation structure periodically varies along the annular profile of the undulation peak.

10. The working piston as claimed in claim 1, wherein an elevation of an undulation peak is arranged so as to be circumferentially offset in relation to an elevation of the adjacent undulation peak.

11. The working piston as claimed in claim 1, wherein at least one undulation peak of the undulation structure is formed by an encircling row of pyramid-shaped elevations.

12. The working piston as claimed in claim 10, wherein at least one undulation peak of the undulation structure is formed by an encircling row of rounded elevations which are arranged spaced apart from one another in encircling fashion.

13. The working piston as claimed in claim 1, wherein the working piston is of monolithic form, or in that the working piston comprises a piston main body and a separately produced piston component which is arranged on the piston main body and which forms the piston crown.

14. A method for producing a working piston of a reciprocating-piston internal combustion engine, comprising the following steps: providing a piston crown of a working piston, and equipping the piston crown with an at least regionally nanostructured undulation structure which is of circular form and which is arranged concentrically with respect to the longitudinal central axis of the working piston.

15. The method as claimed in claim 1, wherein the undulation structure and the nanostructuring of the undulation structure are produced using laser radiation with different wavelengths.

Description

[0033] The invention will be discussed by way of example below with reference to the appended figures and on the basis of preferred embodiments, wherein the features presented below may, in each case individually and in various technically expedient combinations of at least two of said features with one another, constitute a refining or advantageous aspect of the invention. In the figures:

[0034] FIG. 1 shows a schematic plan view of a piston crown of an exemplary embodiment of a working piston according to the invention;

[0035] FIG. 2 is a schematic sectional illustration of a portion of a further exemplary embodiment of a working piston according to the invention;

[0036] FIG. 3 is a schematic sectional illustration of a portion of a further exemplary embodiment of a working piston according to the invention;

[0037] FIG. 4 is a schematic and perspective illustration of a portion of a circular undulation structure of a piston crown of a further exemplary embodiment of a working piston according to the invention;

[0038] FIG. 5 is a schematic and perspective illustration of a portion of a circular undulation structure of a piston crown of a further exemplary embodiment of a working piston according to the invention; and

[0039] FIG. 6 is a schematic and perspective illustration of a portion of a circular undulation structure of a piston crown of a further exemplary embodiment of a working piston according to the invention.

[0040] Functionally identical or identical constituent parts are denoted in the figures by the same reference designations.

[0041] FIG. 1 shows a schematic plan view of a piston crown 1 of an exemplary embodiment of a working piston 2 according to the invention for a reciprocating-piston internal combustion engine (not shown).

[0042] The piston crown 1 comprises an undulation structure 4 which is of circular form and which is arranged concentrically with respect to the longitudinal central axis 3 of the working piston 2 and which is equipped at least in certain regions with a nanostructuring (not shown).

[0043] The undulation structure 4 comprises five undulation peaks 5, between which there are formed undulation troughs (not shown). Adjacent undulation peaks 5 of the undulation structure 4 may be arranged with a radial spacing of approximately 100 m to one another. The side flanks (not shown) of each undulation peak 5 of the undulation structure 4 may run at an angle of approximately 60 with respect to one another. Furthermore, the undulation structure 4 may be of hydrophilic form at least in certain regions.

[0044] The nanostructuring of the undulation structure 4 may be of undulating form and have a period which lies in a range from approximately 500 nm to approximately 1000 nm, in particular is approximately 700 nm.

[0045] At least one undulation peak 5 of the undulation structure 4 may be of rounded or flattened form in cross section. A height of at least one undulation peak 5 of the undulation structure 4 may periodically vary along the annular profile of the undulation peak 5. In particular, the undulation peak 5 may be formed by an encircling row of pyramid-shaped elevations (not shown) or of rounded elevations (not shown) which are arranged spaced apart from one another in encircling fashion.

[0046] The working piston 2 may be of monolithic form. Alternatively, the working piston 2 may have a piston main body (not shown) and a separately produced piston component (not shown) which is arranged on the piston main body and which forms the piston crown 1.

[0047] FIG. 2 is a schematic sectional illustration of a portion of a further exemplary embodiment of a working piston 6 according to the invention for a reciprocating-piston internal combustion engine (not shown).

[0048] The working piston 6 comprises a piston crown 7, which piston crown comprises an undulation structure 8 which is of circular form and which is arranged concentrically with respect to the longitudinal central axis (not shown) of the working piston 6 and which is equipped at least in certain regions with a nanostructuring (not shown).

[0049] The undulation structure 8 comprises multiple undulation peaks 9, between which undulation troughs 10 are formed. Adjacent undulation peaks 9 of the undulation structure 8 may be arranged with a radial spacing of approximately 100 m to one another. The side flanks 11 and 12 of each undulation peak 9 of the undulation structure 8 may run at an angle of approximately 60 with respect to one another. The undulation structure 8, in particular the side flanks 11 and 12 thereof, may be of hydrophilic form at least in certain regions.

[0050] The nanostructuring may be of undulating form and may have a period which lies in a range from approximately 500 nm to approximately 1000 nm, in particular is approximately 700 nm.

[0051] A height of at least one undulation peak 9 of the undulation structure 8 may periodically vary along the annular profile of the undulation peak 9. In particular, the undulation peak 9 may be formed by an encircling row of pyramid-shaped elevations (not shown) or of rounded elevations (not shown) which are arranged spaced apart from one another in encircling fashion.

[0052] The working piston 6 may be of monolithic form. Alternatively, the working piston 6 may have a piston main body (not shown) and a separately produced piston component (not shown) which is arranged on the piston main body and which forms the piston crown 7.

[0053] FIG. 3 is a schematic sectional illustration of a portion of a further exemplary embodiment of a working piston 13 according to the invention for a reciprocating-piston internal combustion engine (not shown). The working piston 13 differs from the exemplary embodiment shown in FIG. 2 in that the undulation peaks 14 and the undulation troughs 15 of the undulation structure 16 are of rounded form in cross section. The respective rounding has a radius which may lie in a range from approximately m to approximately 30 m. To avoid repetitions, reference is otherwise made to the above description relating to FIG. 2.

[0054] FIG. 4 shows a schematic and perspective illustration of a portion of a circular undulation structure 17 of a piston crown 18 of a further exemplary embodiment of a working piston according to the invention (not shown in any more detail) of a reciprocating-piston internal combustion engine (not shown).

[0055] The undulation structure 17 is arranged concentrically with respect to the longitudinal central axis (not shown) of the working piston and is equipped at least in certain regions with a nanostructuring (not shown). The undulation structure 17 comprises multiple undulation peaks 19, between which there are formed undulation troughs (not shown). Adjacent undulation peaks 19 of the undulation structure 17 may be arranged with a radial spacing of approximately 100 m to one another. Side flanks (not shown) of each undulation peak 19 may run at an angle of approximately 60 with respect to one another. The undulation structure 8, in particular the side flanks 11 and 12 thereof, may be of hydrophilic form at least in certain regions.

[0056] The nanostructuring may be of undulating form and have a period which lies in a range from approximately 500 nm to approximately 1000 nm, in particular is approximately 700 nm.

[0057] The height of each undulation peak 19 periodically varies along the annular profile of the undulation peak 19. In particular, each undulation peak 19 is formed by an encircling row of rounded elevations 20 which are arranged spaced apart from one another in encircling fashion. The elevations of one undulation peak 19 are arranged so as to be circumferentially offset relative to the elevations 20 of an adjacent undulation peak 19. At least one undulation peak 19 may be of rounded or flattened form in cross section.

[0058] The working piston may be of monolithic form. Alternatively, the working piston may have a piston main body (not shown) and a separately produced piston component (not shown) which is arranged on the piston main body and which forms the piston crown 18.

[0059] FIG. 5 is a schematic and perspective illustration of a portion of a circular undulation structure 21 of a piston crown 22 of a further exemplary embodiment of a working piston according to the invention (not shown in any more detail) of a reciprocating-piston internal combustion engine (not shown). The undulation structure 21 differs from the exemplary embodiment shown in figure in that each undulation peak 23 is formed by an encircling row of pyramid-shaped elevations 24. Each pyramid-shaped elevation 24 comprises a rhomboidal base area (not shown) with diagonals of different length, wherein the longer diagonal is oriented tangentially with respect to the annular profile of the respective undulation peak 23. To avoid repetitions, reference is otherwise made to the above description relating to FIG. 4.

[0060] FIG. 6 is a schematic and perspective illustration of a portion of a circular undulation structure 25 of a piston crown 26 of a further exemplary embodiment of a working piston according to the invention (not shown in any more detail) of a reciprocating-piston internal combustion engine (not shown). The undulation structure 25 differs from the exemplary embodiment shown in FIG. 4 in particular in that each undulation peak 27 is of flattened form. To avoid repetitions, reference is otherwise made to the above description relating to FIG. 4.

LIST OF REFERENCE DESIGNATIONS

[0061] 1 Piston crown [0062] 2 Working piston [0063] 3 Longitudinal central axis [0064] 4 Undulation structure [0065] 5 Undulation peak [0066] 6 Working piston [0067] 7 Piston crown [0068] 8 Undulation structure [0069] 9 Undulation peak [0070] 10 Undulation trough [0071] 11 Side flank [0072] 12 Side flank [0073] 13 Working piston [0074] 14 Undulation peak [0075] 15 Undulation trough [0076] 16 Undulation structure [0077] 17 Undulation structure [0078] 18 Piston crown [0079] 19 Undulation peak [0080] 20 Rounded elevation [0081] 21 Undulation structure [0082] 22 Piston crown [0083] 23 Undulation peak [0084] 24 Pyramid-shaped elevation [0085] 25 Undulation structure [0086] 26 Piston crown [0087] 27 Undulation peak