Piston for an internal combustion engine

Abstract

A piston for an internal combustion engine including a piston crown and a combustion chamber recess recessed therein, the combustion chamber recess including a recess edge. The piston may also include a ring groove for receiving a piston ring. The piston may further include a cooling duct having a smaller spacing from the piston crown than that of a flank of the ring groove, the cooling duct defining a minimum spacing from the piston crown at a first location, and a minimum spacing from the combustion chamber recess at a second location. The cooling duct may have a rounded portion between the first location and the second location. The cooling duct may have a maximum spacing from the recess edge at a third location. The rounded portion may have a rounding radius defined at least at the third location that is greater than 4% of a piston diameter.

Claims

1. A piston for an internal combustion engine, comprising: a piston crown and a combustion chamber recess recessed therein, the combustion chamber recess including a recess edge; a ring groove for receiving a piston ring; a cooling duct having a smaller spacing from the piston crown than that of a flank of the ring groove, the cooling duct defining a minimum spacing from the piston crown at a first location and a minimum spacing from the combustion chamber recess at a second location, wherein the cooling duct has a rounded portion between the first location and the second location; wherein the cooling duct, as measured at a right angle with respect to a surface of the cooling duct, has a maximum spacing from the recess edge at a third location facing towards the recess edge, and wherein the rounded portion has a rounding radius defined at least at the third location that is greater than 4% of a piston diameter; wherein the rounded portion is defined by at least three adjoining radii including a first radius, a second radius, and a third radius; and wherein the first radius, the second radius, and the third radius are each greater than 4% of the piston diameter.

2. The piston as claimed in claim 1, wherein the rounding radius at the third location is greater than 5% of the piston diameter.

3. The piston as claimed in claim 1, wherein the rounding radius of greater than 4% of the piston diameter is provided continuously between the second location and the third location.

4. The piston as claimed in claim 1, wherein at least one of: the first radius is greater than the second radius; the first radius is smaller than the third radius; and the second radius is smaller than the third radius.

5. The piston as claimed in claim 1, wherein the first radius is approximately 3.7 mm and the second radius is approximately 3.6 mm.

6. The piston as claimed in claim 1, wherein the third radius is approximately 4.4 mm.

7. The piston as claimed in claim 1, wherein the at least three radii further include a fourth radius adjoining the third radius, and extending as far as the first location, wherein the forth radius is smaller than the first radius and the second radius.

8. The piston as claimed in claim 7, wherein the fourth radius is approximately 1.3 mm.

9. The piston as claimed in claim 1, wherein the piston diameter is approximately 83 mm.

10. The piston as claimed in claim 1, wherein at least one of: the minimum spacing from the piston crown is approximately 3.0 mm; the minimum spacing from the combustion chamber recess is at least 2.6 mm; and the maximum spacing from the recess edge is approximately 7.1 mm.

11. The piston as claimed in claim 1, wherein a ratio of a height of the cooling duct to the third radius is 0.6.

12. The piston as claimed in claim 11, wherein the height of the cooling duct is approximately 6.6 mm.

13. The piston as claimed in claim 1, wherein the flank is a distal flank of the ring groove disposed remote from the piston crown in relation to a proximal flank of the ring groove, and wherein the cooling duct defines an axial extent disposed axially between the piston crown and the proximal flank relative to a piston axis extending perpendicular to the piston crown.

14. A piston for an internal combustion engine, comprising: a piston crown; a combustion chamber recess recessed in the piston crown and including a recess edge; a plurality of ring grooves including a first ring groove and further ring grooves disposed further away from the piston crown than the first ring groove, the first ring groove having a flank disposed proximal to the piston crown and a further flank disposed remote from the piston crown in relation to the flank; a cooling duct having a smaller spacing from the piston crown than that of the further flank of the first ring groove, the cooling duct defining a minimum spacing from the piston crown at a first location and a minimum spacing from the combustion chamber recess at a second location, wherein the cooling duct has a rounded portion between the first location and the second location; wherein the cooling duct, as measured at a right angle with respect to a surface of the cooling duct, has a maximum spacing from the recess edge at a third location that faces towards the recess edge, and wherein the rounded portion defines a rounding radius of greater than 4% of a piston diameter at least at the third location; wherein the cooling duct is disposed axially between the piston crown and the further flank of the first ring groove relative to a piston axis extending perpendicular to the piston crown; wherein the rounded portion is defined by at least three adjoining radii including a first radius, a second radius, and a third radius; wherein the first radius, the second radius, and the third radius are each greater than 4% of the piston diameter; wherein the first radius is greater than the second radius and smaller than the third radius, the first radius defines a first section of the rounded portion, the second radius defines a second section of the rounded portion, and the third radius defines a third section of the rounded portion; and wherein the first section is disposed proximal the second location, the third section is disposed proximal the first location, and the second section is disposed between the first section and the third section.

15. The piston as claimed in claim 14, wherein the first location of the cooling duct has an oval shape disposed circumferentially between the rounded portion and a straight section of the cooling duct, and wherein the oval shape of the first location is defined by a radius that is smaller than the rounding radius of the rounded portion.

16. The piston as claimed in claim 1, further comprising a plurality of further ring grooves disposed further away axially from the piston crown than the ring groove relative to a piston axis extending perpendicular to the piston crown; wherein the cooling duct is disposed axially between the piston crown and the flank of the ring groove.

17. The piston as claimed in claim 1, wherein the cooling duct has a straight section disposed opposite to the rounded portion circumferentially between the first location and the second location, the straight section extending toward the piston crown and away from the combustion chamber recess at an 8 angle relative to a piston axis extending perpendicular to the piston crown.

18. The piston as claimed in claim 17, wherein the first location has an oval shape disposed circumferentially between the straight section and the rounded portion, and wherein the oval shape of the first location is defined by a radius that is smaller than the rounding radius of the rounded portion.

19. The piston as claimed in claim 1, wherein: the first radius is greater than the second radius and smaller than the third radius; the first radii defines a first section of the rounded portion the second radii defines a second section of the rounded portion, and the third radii defines a third section of the rounded portion; and the first section is disposed proximal the second location, the third section is disposed proximal the first location, and the second section is disposed between the first section and the third section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings, in each case diagrammatically:

(2) FIG. 1 shows a detailed illustration of a sectional illustration through a piston according to the invention, and

(3) FIG. 2 shows a detailed illustration of the individual radii of the cooling duct of the piston in accordance with FIG. 1.

DETAILED DESCRIPTION

(4) In accordance with FIGS. 1 and 2, a piston 1 according to the invention of an internal combustion engine (not shown otherwise) has a piston crown 2 and a combustion chamber recess 3 which is recessed therein and forms a recess edge 16 in a transition region to the piston crown 2. At least one ring groove 4 (here, a ring groove 4 which is closest to the piston crown) for receiving a piston ring (not shown) is provided on an outer side of the piston 1. The ring groove 4 has a flank 21 which is close to the piston crown and a flank 22 which is remote from the piston crown, which flanks 21, 22 are arranged in an annular manner and substantially at a right angle with respect to the piston axis 11. A substantially cylindrical groove bottom 23 is situated between the flanks 21 and 22. A cooling duct 5 for cooling the piston 1 is likewise provided.

(5) In order for it then to be possible to increase the thermal load-bearing capability of the piston 1 and therefore also indirectly its service life, the cooling duct 5 has a smaller spacing from the piston crown 2 than the at least one ring groove 4. This means that the cooling duct 5 overall is arranged closer to the piston crown 2 than at least the flank 22, remote from the piston crown, of the one ring groove 4 or the ring groove 4 which is closest to the piston crown. In the preferred exemplary embodiment, the entire cooling duct cross section is closer to the piston crown 2 than that flank 21 of the uppermost ring groove 4 which is close to the piston crown. As a rule, the piston 1 also has further ring grooves (not shown) which are further away from the piston crown. Moreover, the cooling duct 5 has a minimum spacing 6 (cf. FIG. 2) from the piston crown 2 at a first location 8, and has a minimum spacing 7 from the combustion chamber recess 3 at a second location 9. Furthermore, at a third location 18 which faces the recess edge 16 between the first location 8 and the second location 9, the cooling duct 5 has a maximum spacing 17 between the combustion chamber-side piston surface in the region of the recess edge 16 and the cooling duct surface, the spacing 17 being measured at a right angle with respect to the cooling duct surface. Here, the cooling duct 5 is of rounded configuration between the third location 8 and the second location 9, the rounded portion having a radius R3 of more than 5% of the piston diameter at the third location 18. In the region from the second location 9 as far as the third location 18, there is continuously a rounding radius of more than 4% of the piston diameter by way of R3 and a radius R2 which is greater than 4% of the piston diameter d and adjoins R3 without a sharp bend.

(6) In a manner which begins at the second location 9 beyond the third location 18 as far as just before the first location 8, the cooling duct cross section is described by way of at least three radii R1, R2 and R3 which adjoin one another and are in each case greater than 4% of the piston diameter d.

(7) Here, the first radius R1 at, for example, 3.7 mm is greater than the second radius R2 at, for example, 3.6 mm. In addition or as an alternative, the first radius R1 can be smaller than the third radius R3 which can be, for example, 4.4 mm.

(8) If FIG. 2 is considered, it can be seen that a fourth radius R4 is provided which describes a rounded portion of the cooling duct 5, adjoins the third radius R3, reaches as far as the first location 8, and is smaller than the radii R1 and R2 and is also smaller than the radius R3. The fourth radius R4 can be, for example, 1.3 mm. The piston diameter d can have, for example, a value of 83 mm which is customary for passenger car pistons. Here, the abovementioned dimensions are to be protected in particular even in proportion to one another, with the result that pistons 1 having correspondingly enlarged or reduced radii R1, R2, R3, R4 and piston diameters d are also to fall within the invention by way of a positive or negative extrapolation.

(9) If FIG. 2 is once again considered, it can be seen from said figure that the minimum spacing 6 between the first location 8 and the piston crown 2 can be, for example, 3 mm, and the minimum spacing 7 between the second location 9 and the combustion chamber recess 3 can be, for example, 3.3 mm, in particular 3.374 mm, whereas the maximum spacing 17 between the third location 18 and the recess edge 16 can be, for example, 7.1 mm. It goes without saying that said spacings 6, 7 can also be extrapolated correspondingly or adapted and converted in the case of a change in the piston diameter d.

(10) If FIG. 1 is considered, it can be seen that the cooling duct 5 has a height h; a ratio of the height h of the cooling duct 5 to the radius R3 which is present at the third location can be or should be h/R30.6 and particularly preferably h/R30.65, in order for it to be possible to achieve as low a notch effect as possible and therefore a high thermal load-bearing capability and a long service life. Here, the height h of the cooling duct 5 can be, for example, 6.6 mm.

(11) It can be seen from FIGS. 1 and 2 that the cooling duct 5 has a straight section 10, said straight section 10 being inclined by an angle of approximately 8 (cf. FIGS. 1 and 2) with respect to the piston axis 11. The production of the piston 1 can be improved by way of a section 10 of this type.

(12) A particularly advantageous embodiment in relation to the thermal load-bearing capability and the long service life of the piston 1 can therefore be achieved by way of the arrangement according to the invention of the cooling duct 5 in relation to the piston crown 2 and the combustion chamber recess 3 and, in particular, also in relation to the arrangement of the ring groove 4 and generally the selection of the radii R1 to R4.