Piston With a Low Overall Height

Abstract

The invention relates to a piston for an internal combustion engine having an upper part integrally joined to a lower part having a shaft and at least one pin bore. The upper part including a combustion chamber bowl recess and a piston crown with a crown edge. At least one joint is arranged in the region of a ring zone and in an outer wall of the combustion bowl recess, and the ratio of piston compression height (h.sub.1) and the diameter of the piston (d.sub.1) is less than 0.53.

Claims

1. A piston for an internal combustion engine, having an upper part joined by material bonding to a lower part, wherein the lower part comprises a shaft and at least one pin bore, wherein the upper part comprises a combustion bowl and a piston crown having a crown edge, characterized in that at least one joint is arranged in a region of a ring field and in an outer wall of the combustion bowl and a ratio of piston compression height (h.sub.1) and diameter of the piston (d.sub.1) is smaller than 0.53.

2. The piston of claim 1, wherein the joint in the outer wall of the combustion bowl is positioned above a finished combustion bowl base in a direction of a piston stroke axis.

3. The piston of claim 1, wherein the piston crown defines at least one recess.

4. The piston of claim 3, wherein the at least one recess defines at least one clearance which passes at least partially through the crown edge of the piston crown.

5. The piston of claim 3, wherein the at least one clearance is configured in a circular segment shape.

6. The piston of claim 3, wherein the at least one recess defines a first valve pocket.

7. The piston of claim 6 wherein the at least one recess defines a second valve pocket, wherein a distance (x.sub.1) between a line positioned between a pressure side and counter-pressure side and a center point of the first valve pocket is larger than a distance (x.sub.2) between the line and a center point of the second valve pocket.

8. The piston of claim 7, wherein the distance (x.sub.1) is at least twice as large as the distance (x.sub.2).

9. The piston of claim 1 further comprising a coating positioned on the piston shaft, the coating operable to reduce friction.

10. The piston of claim 1 further comprising a cooling duct.

11. The piston of claim 10, further comprising at least one elongated intake in communication with the cooling duct operable to provide the admission of oil to the cooling duct.

12. The piston of claim 11, wherein the cooling duct defines at least one molded-in recess in a cooling duct contour.

13. The piston of claim 12, wherein the at least one molded-in recess in the cooling duct is positioned at a point of impact of focal rays in the combustion bowl.

14. The piston of claim 1 wherein the upper part comprises a warm forged upper part.

15. A piston for an internal combustion engine comprising: a lower part having a shaft defining at least one pin bore having a pin bore axis, the lower part oriented along a piston stroke axis perpendicular to the pin bore axis; an upper part connected to the lower part at a joint, the upper part further having a top surface and defining a combustion bowl recess extending from the top surface toward the lower part; the connected upper part and lower part further comprising: a ring field extending radially from and longitudinally along the piston stroke axis, the joint positioned in the ring field; a piston compression height (h1) defined between the pin bore axis and the upper part top surface; a piston outer diameter (d1); wherein a ratio of the piston compression height (h1) and the piston outer diameter (d1) is between 0.48 and 0.75.

16. The piston of claim 15 wherein the ratio of the piston compression height (h1) and the piston outer diameter (d1) is less than 0.53.

17. The piston of claim 16, wherein the piston compression height (h1) is between 70 millimeters and 90 millimeters, and the piston outer diameter (d1) is between 100 millimeters and 150 millimeters.

18. The piston of claim 15 wherein the upper part further defines a first recess in the top surface and extending toward the lower part.

19. The piston of claim 18 wherein the upper part further defines a first valve pocket positioned within the first recess.

20. The piston of claim 19, wherein: the recess defines a clearance positioned through an outer edge of the upper part top surface; and the first valve pocket includes a diameter (d4) between 35 millimeters and 55 millimeters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The fundamental idea is explained below on the basis of the figures. Further details of the invention are described in the figures on the basis of schematically represented exemplary embodiments.

[0030] FIG. 1 shows a sectional view of a piston;

[0031] FIG. 2 shows a sectional view of a piston according to line II in FIG. 1;

[0032] FIG. 3 shows an enlarged detail marked by III in FIG. 2;

[0033] FIG. 4 shows an enlarged detail marked by IV from FIG. 2;

[0034] FIG. 5 shows a sectional view of a piston according to line V-V in FIG. 2;

[0035] FIG. 6 shows a sectional view of a piston according to line VI-VI in FIG. 2;

[0036] FIG. 7 shows a sectional view of a piston according to line VII-VII in FIG. 6;

[0037] FIG. 8 shows a sectional view of a piston region according to line VIII-VIII in FIG. 7;

[0038] FIG. 9 shows a top view of a piston crown;

[0039] FIG. 10 shows a cut-out from the piston in the region of a valve pocket provided on the piston crown side in accordance with a sectional guide X-X in FIG. 9;

[0040] FIG. 11 shows a sectional view of a further piston;

[0041] FIGS. 12A and 12B respectively show sectional views of a lower part and an upper part of a piston according to FIG. 11; and

[0042] FIGS. 13A and 13B respectively show sectional views rotated by 90 degrees with respect to FIGS. 12A and 12B of a lower part and an upper part of a piston according to FIG. 11.

DETAILED DESCRIPTION

[0043] Piston 1 has an identical structure in each case in the Figures and is firstly described in general below. The Figures are subsequently represented in detail in each case. Identical components are designated by identical reference numbers in the Figures and new reference numbers are used in the Figures for different components.

[0044] Piston 1 for an internal combustion engine is produced from a lower part 2 and an upper part 3. At least one joint 4 is formed between lower part 2 and upper part 3. Joint surfaces formed on lower part 2 and on upper part 3 meet one another in the region of joint 4. A joint 4 is formed in the region of a ring field 9. A further joint 4 is additionally formed in the outer wall of a combustion bowl 11. At least one of joints 4 can be embodied as a pipe on plate. In so far as piston 1 has at least one cooling duct 8, the contour of the at least one cooling duct 8 can be formed in lower part 2 or in upper part 3, wherein this design is referred to as a pipe. The mating side is embodied in lower part 2 or in upper part 3 as a circumferential planar or almost planar surface and correspondingly referred to as a plate.

[0045] A piston crown 5 is formed on upper part 3. Piston crown 5 is arranged on the side of upper part 3 facing away from a cooling duct 8. A piston shaft 6 which has pin bores 7 is formed on lower part 2. Piston 1 joined from lower part 2 and upper part 3 has circumferential ring field 9, equipped with annular grooves 10. Combustion bowl 11 is arranged centrally or eccentrically around a piston stroke axis 12 in upper part 3. There is arranged in the region of pin bore 7 a pin bore axis 13 which corresponds to the center axis of the piston pin, not represented. Oil return openings 19 can be, but do not have to be, arranged in the region of ring field 9.

[0046] A piston 1 joined from lower part 2 and upper part 2 is depicted in FIG. 1. In the region of shaft 6, this has a coating 14. Said coating 14 has a low degree of friction. The advantages of said coating 14 are very good durability, outstanding sliding properties and a significant increase in the life span of piston 1.

[0047] The points at which piston compression height h1 and diameter d1 of the piston are measured are represented in FIGS. 1, 6 and 11. Bowl height h2 of the combustion bowl is plotted in FIGS. 6 and 11. Diameter d1 of piston 1 according to FIGS. 1 and 6 can be, for example, between 100 mm and 150 mm. The value for h1 can vary between 70 mm and 90 mm. The ratio of compression height h1 and diameter d1 of piston 1 thus varies between 0.48 and 0.75.

[0048] A burr-free region 15 is arranged in the region of pin bore 7 in FIG. 5. An auxiliary counter bore 16 is furthermore represented centrally.

[0049] An intake 17 with a diameter d2 and an outlet 18 with a diameter d3 are represented in FIG. 7. Oil can enter into the cooling region through intake 17 and the oil can leave this region again through outlet 18.

[0050] FIG. 9 shows two recesses 20 embodied as valve pockets 21, 22 which each have a diameter d4. Diameter d4 can assume a value between 35 mm and 55 mm. Diameter d4 of valve pockets 21, 22 can also assume different values. Any desired number of recesses 20, which are formed, for example, as milled slots, can be provided. At least a part of recesses 20 is preferably formed at least in regions as valve pocket 21, 22, in which gas exchange valves of the reciprocating piston internal combustion engine can be accommodated at least in regions, i.e. dip in, during their operation. A collision of the gas exchange valves with piston 1 can thus be avoided. As a result of this configuration and function of recesses 20, a functional integration is represented which keeps the costs of piston 1, in particular its production costs, low.

[0051] Valve pockets 21, 22 of piston 1 follow on in the radial direction of piston 1, in which valve pockets respective corresponding valve plates of gas exchange valve of the reciprocating piston internal combustion engine can be received. If piston 1 is located at its upper dead center in the combustion chamber of the reciprocating piston machine, valve pockets 21, 22 provide enough space for the respective gas exchange valves, i.e. for corresponding inlet and outlet valves, so that the gas exchange valves can respectively carry out a desirably large valve stroke in order to enable a gas exchange. In other words, the gas exchange valves can open wide enough by means of the spaces provided by valve pockets 21, 22 in order to be able to efficiently bring about an exchange of exhaust gas and air taken in by the reciprocating piston internal combustion engine or a mixture taken in by the reciprocating piston internal combustion engine.

[0052] A first circular segment Alpha is located between a first valve pocket 21 and line 24 which is perpendicular to line 23 which connects a pressure side (PS) 25 and a counter-pressure side (CPS) 26. A second circular segment Beta is located between line 24 which is perpendicular to line 23 which connects pressure side 25 and counter-pressure side 26 and a second valve pocket 22. A third circular segment Gamma is located between second valve pocket 22 and line 23 which connects pressure side 25 and counter-pressure side 26. The first circular segment Alpha can assume values between 15 degrees and 30 degrees, preferably between 20 degrees and 25 degrees. The second circular segment Beta can assume values between 55 degrees and 70 degrees, preferably between 60 degrees and 65 degrees. The third circular segment Gamma can assume values between 15 degrees and 35 degrees, preferably between 20 degrees and 30 degrees.

[0053] Piston crown 11 is bounded circumferentially by crown edge 27. Crown edge 27 has, in the region of valve pockets 21, 22, a clearance or circular segment-shaped recesses 28. Length I1 of recess 28 of first valve pocket 21 corresponds to length I2 of recess 28 of second valve pocket 22. Lengths I1 and I2 can assume values between 15 millimeters and 35 millimeters, preferably between 20 mm and 30 mm. According to the exemplary embodiment, I1 and I2 can have identical values, but do not have to have identical values. The dimensions for I1 and I2 can be varied independently of one another.

[0054] Distance x1 between line 23 and the center point of first valve pocket 21 is larger than distance x2 between line 23 and the center point of second valve pocket 22. Distance x1 can be between 30 mm and 45 mm, preferably between 35 mm and 40 mm. Distance x2 can lie between 15 mm and 22.5 mm, preferably between 17.5 mm and 22.5 mm.

[0055] The distance between the center point of first valve pocket 21 and line 24 is designated by x3. The distance between line 24 and the center point of second valve pocket 22 is designated by x4. Distance x3 is smaller than distance x4. Distance x4 can lie between 25 mm and 45 mm, preferably between 30 mm and 40 mm. Distance x3 can lie between 12.5 mm and 22.5 mm, preferably between 15 mm and 20 mm.

[0056] FIG. 11 shows a finished piston 1, in which it is apparent at which points piston compression height h1 and diameter d1 of the piston are measured. Piston 1 shown in FIG. 11 is a two-part piston, comprising upper part 3 and lower part 2 which are joined together. Ready for use, piston 1 is then integral. However, piston 1 can also be formed in one piece. Said piston 1 has a ratio between compression height h1 of piston 1 and diameter d1 of piston 1 of 0.53.

[0057] FIGS. 12A and 12B as well as 13A and 13B show the views of upper part 3 and lower part 2 prior to joining together. This is an example of a constructive configuration of upper part 3 and lower part 2 which are joined together in a suitable manner, preferably by friction welding in order to achieve the desired ratio 0.53, preferably less than 0.53.

LIST OF REFERENCE NUMBERS

[0058] 1 Piston [0059] 2 Piston lower part [0060] 3 Piston upper part [0061] 4 Joint [0062] 5 Piston crown [0063] 6 Piston shaft [0064] 7 Pin bore [0065] 8 Cooling duct [0066] 9 Ring field [0067] 10 Annular groove [0068] 11 Combustion bowl [0069] 12 Piston stroke axis [0070] 13 Pin bore axis/center axis of the pin bore [0071] 14 Coating [0072] 15 Burr-free region [0073] 16 Auxiliary counter bore [0074] 17 Intake [0075] 18 Outlet [0076] 19 Oil return opening [0077] 20 Recess [0078] 21 First valve pocket [0079] 22 Second valve pocket [0080] 23 Line between pressure side (PS) and counter-pressure side (CPS) [0081] 24 Line perpendicular to line 23 [0082] 25 Pressure side (PS) [0083] 26 Counter-pressure side (CPS) [0084] 27 Crown edge [0085] 28 Clearances [0086] h.sub.1 Piston compression height [0087] h.sub.2 Bowl height [0088] l.sub.1 Length of the clearance of the first valve pocket [0089] l.sub.2 Length of the clearance of the second valve pocket [0090] x.sub.1 Distance between line 23 and the center point of first valve pocket 21 [0091] x.sub.2 Distance between line 23 and the center point of second valve pocket 22 [0092] x.sub.3 Distance between the center point of first valve pocket 21 and line 24 [0093] x.sub.4 Distance between line 24 and the center point of second valve pocket 22 [0094] d.sub.1 Diameter of piston [0095] d.sub.2 Diameter of intake [0096] d.sub.3 Diameter of outlet [0097] d.sub.4 Diameter of valve pocket [0098] Alpha first circular segment between first valve pocket and the line which is perpendicular to the line which connects the pressure side and the counter-pressure side [0099] Beta second circular segment between the line which is perpendicular to the line which connects the pressure side and the counter-pressure side and the second valve pocket [0100] Gamma third circular segment between the second valve pocket and the line which connects the pressure side and the counter-pressure side