Piston of an internal combustion engine

Abstract

A piston of an internal combustion engine includes a piston head including a ring belt having a firing land and a plurality of ring grooves for receiving piston rings. A first ring groove of the plurality of ring grooves that is arranged directly adjacent to the firing land has a ring groove axis that runs coaxially to a piston axis of the piston. The first ring groove has an upper groove flank and a lower groove flank arranged away from the firing land relative to the upper groove flank. At least the lower groove flank of at least the first ring groove is inclined by an inclination angle with respect to an orthogonal plane relative to the piston axis, and the inclination angle of at least the lower groove flank varies in a circumferential direction of the piston axis.

Claims

1. A piston of an internal combustion engine, comprising: a piston head including a ring belt having a firing land and a plurality of ring grooves for receiving piston rings; a first ring groove of the plurality of ring grooves arranged directly adjacent to the firing land, and having an upper groove flank and a lower groove flank arranged away from the firing land relative to the upper groove flank; at least the first ring groove having a ring groove axis that runs coaxially to a piston axis; wherein at least the lower groove flank of at least the first ring groove is inclined radially outwards by an inclination angle with respect to an orthogonal plane relative to the piston axis; and wherein the inclination angle of at least the lower groove flank varies in a circumferential direction of the piston axis.

2. The piston according to claim 1, wherein the upper groove flank of at least the first ring groove is inclined by a further inclination angle with respect to the orthogonal plane, and wherein the further inclination angle of at least the upper groove flank varies in the circumferential direction.

3. The piston according to claim 1, wherein the inclination angle of the lower groove flank has at least two maxima and at least two minima in the circumferential direction.

4. The piston according to claim 1, wherein the inclination angle of the lower groove flank lies in a range 1+1.

5. The piston according to claim 4, wherein at least the lower groove flank rises or falls radially outwardly from the piston axis.

6. The piston according to claim 4, wherein the lower groove flank rises toward the firing land in a radially outward direction, and wherein the lower groove flank has a further location in the circumferential direction at which the inclination angle is =0.

7. The piston according to claim 4, wherein the lower groove flank falls away from the firing land in a radially outward direction, and wherein the lower groove flank has a further location in the circumferential direction at which the inclination angle is =0.

8. The piston according to claim 1, wherein at least the lower groove flank of the first ring groove has a location, at which the inclination angle is =0.

9. The piston according to claim 1, wherein at least the lower groove flank of the first ring groove is corrugated in the circumferential direction.

10. The piston according to claim 9, wherein the lower groove flank has at least two corrugation peaks and at least two corrugation troughs in the circumferential direction.

11. The piston according to claim 1, wherein the lower groove flank extends inclined to the orthogonal plane over a full circumference of the first ring groove, and wherein the inclination angle of the lower groove flank varies between a maximum value and a minimum value in the circumferential direction.

12. An internal combustion engine, comprising: at least one piston having a piston axis, the at least one piston including: a piston head including a ring belt having a firing land and a plurality of ring grooves for receiving piston rings; the plurality of ring grooves including a first ring groove arranged directly adjacent to the firing land and having a ring groove axis disposed coaxially to the piston axis; and the first ring groove having an upper groove flank and a lower groove flank arranged away from the firing land relative to the upper groove flank; wherein at least the lower groove flank of the first ring groove is inclined radially outwards by an inclination angle with respect to an orthogonal plane relative to the piston axis, and wherein the inclination angle of the lower groove flank varies in a circumferential direction of the piston axis.

13. The internal combustion engine according to claim 12, wherein the upper groove flank of the first ring groove is inclined by a further inclination angle with respect to the orthogonal plane, and wherein the further inclination angle of the upper groove flank varies in the circumferential direction.

14. The internal combustion engine according to claim 13, wherein at least one of the inclination angle of the lower groove flank and the further inclination angle of the upper groove flank lies in a range of 1 with respect to the orthogonal plane.

15. The internal combustion engine according to claim 13, wherein at least one of the lower groove flank and the upper groove flank rises or falls radially outwardly from the piston axis.

16. The internal combustion engine according to claim 12, wherein the inclination angle of the lower groove flank has two maxima and two minima in the circumferential direction.

17. The internal combustion engine according to claim 16, wherein the inclination angle of the lower groove flank is in a range of 1+1.

18. The internal combustion engine according to claim 12, wherein the lower groove flank has a location which the inclination angle is =0.

19. The internal combustion engine according to claim 12, wherein the lower groove flank is corrugated in the circumferential direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 shows a piston according to the invention of an internal combustion engine in the region of a ring belt of a piston head with an outwardly rising lower groove flank,

(3) FIG. 2 shows an illustration as in FIG. 1, but with an outwardly falling lower groove flank,

(4) FIG. 3 shows an illustration as in FIG. 2, but with an additionally corrugated course of the lower groove flank, and

(5) FIG. 4 shows a piston according to another example in the region of the ring belt with an upper groove flank that is inclined by an inclination angle that varies in the circumferential direction.

DETAILED DESCRIPTION

(6) In accordance with FIGS. 1 to 3, a piston 1 according to the invention of an internal combustion engine 2 which is otherwise not shown has a piston head 3 with a ring belt 4 with a firing land 5 and at least one ring groove 6, 6 for receiving a piston ring (not shown). Here, a first ring groove 6 is arranged directly adjacently with respect to the firing land 5, and has an upper groove flank 7 and a lower groove flank 8.

(7) Here, at least one ring groove 6, 6 is of radially circumferential configuration with a radius which runs orthogonally with respect to the piston axis 10. The ring groove 6, 6 therefore lies at least substantially in a plane which runs orthogonally with respect to the piston axis 10. A groove bottom 16 usually runs parallel to the piston axis 10. The ring groove 6, 6 also usually runs parallel to a piston crown 18. Here, at least two, preferably all, ring grooves 6, 6 run parallel to one another and parallel to the piston crown 18.

(8) At least the first ring groove 6 has a ring groove axis 10 which runs coaxially, that is to say identically, with respect to the piston axis 10.

(9) According to the invention, at least the lower groove flank 8 of the ring groove 6 which is directly adjacent with respect to the firing land 5, that is to say of the first ring groove 6, is then inclined by an inclination angle with respect to an orthogonal 9 with respect to the piston axis 10, the inclination of at least the lower groove flank 8 varying in the circumferential direction. An optimum compensation of a thermal/mechanical load can be achieved by way of the variation of the inclination in the circumferential direction, that is to say by way of the variation of the inclination angle of the groove flank 8. As a result, it is possible, in particular, to compensate for non-rotationally symmetrical deformations of the piston 1 during operation, in particular also on account of a differing flexural stiffness in the orthogonal direction, thermal conductivity, cooling and/or temperature distribution. By way of the variation of the inclination, that is to say of the inclination angle as viewed over the circumference, moreover, considerably improved contact of a piston ring which is arranged in at least the first ring groove 6 can be achieved, as a result of which the said piston ring can be supported in an improved manner and, as a result, slides in an improved manner along the cylinder wall and, as a result, contributes to reducing an oil consumption of the internal combustion engine 2. As a result of the inclination angle which varies in the circumferential direction, a conical bearing face for the piston ring can be provided together with the non-rotationally symmetrical deformations of the piston 1 during operation, the said conical bearing face, that is to say the lower groove flank 8 in the present case, providing flat, homogeneous contact for the piston ring.

(10) In the case of the pistons 1 which are shown in accordance with FIGS. 1 to 3, a pin axis runs perpendicularly with respect to the piston axis 10 and perpendicularly with respect to the orthogonal 9, that is to say perpendicularly with respect to the plane of the drawing in the present case.

(11) If the first ring groove 6 in accordance with FIG. 1 is considered further, it can be seen that the lower groove flank 8 thereof rises on the right and on the left to the outside, whereas it is horizontal in the region of a location 11, that is to say is parallel to the pin axis. At the said location 11, the inclination angle is therefore =0.

(12) In accordance with FIG. 2, a piston 1 is shown, in the case of which the lower groove flank 8 of the first ring groove 6, that is to say of the ring groove 6 which is directly adjacent with respect to the firing land 5, falls radially to the outside and likewise varies over the circumference with regard to its inclination angle . The said inclination angle is thus at its greatest on the right and on the left between the orthogonal 9 with respect to the piston axis 10, and corresponds to an inclination angle of 0 at the location 11, with the result that the lower groove flank 8 is parallel to the orthogonal 9 in the said region.

(13) Many further embodiments are not shown but are advantageous, which further embodiments compensate for the measurable thermal expansion behaviour of a certain piston. Thus, the rising (FIG. 1) or falling (FIG. 2) lower groove flank 8 can advantageously also run in an inclined manner over the full circumference, without reaching the value zero anywhere, the inclination angle varying between a maximum and minimum value. This case can result by way of thermal expansions alone, but is also present when, for example, a considerable basic inclination of the groove flank is predefined by way of a trapezoidal ring, which basic inclination varies according to the invention only to a relatively small extent. It would also be possible, however, that the inclination changes its sign in the circumferential direction, that is to say, for example, is of rising configuration along the pin axis as in FIG. 1, but is of falling configuration transversely with respect to the said pin axis as in FIG. 2. Furthermore, the grooves according to FIGS. 1-3 and the described modifications might also be realised in relation to the pin axis in the plane of the drawing, instead of perpendicularly with respect thereto. It is conceivable, furthermore, that the upper groove flank 7 of at least the first ring groove 6 (see FIG. 4), but also the lower and/or upper flanks of further ring groove 6 (cf. FIG. 1) are inclined by an inclination angle with respect to the orthogonal 9 with respect to the piston axis 10, the inclination of the upper groove flank 7 likewise varying in the circumferential direction. In the same way, the groove flanks 7, 8 with inclination angles which vary over the circumference can also be used in further ring grooves 6.

(14) If FIGS. 1 to 3 are considered further, it can be seen that at least the lower groove flank 8 has two corrugation peaks 12 and two corrugation troughs 13 in the circumferential direction. Here, according to FIGS. 1 and 3, a corrugation trough 13 is arranged in the region of the location 11, whereas, according to FIG. 2, a corrugation peak 12 is arranged at the location 11. In general, the inclination angle with respect to the orthogonal 9 with respect to the piston axis 10 can lie in a range between 1+1, it being possible for manufacturing tolerances of from 5 to 10 angular minutes to occur.

(15) If the lower groove flank 8 of the first ring groove 6 according to FIG. 3 is considered, it can be seen there that the lower groove flank 8 is corrugated in the circumferential direction. It is not only the angle inclination a of the lower groove flank 8 which varies in the circumferential direction, but rather also the lower edge of the groove bottom 16 runs in a corrugated manner in the axial direction. Once again, two maxima and two minima per 360 are preferably caused by the typical piston geometry. They preferably lie along the pin axis or perpendicularly with respect thereto or vice versa. Other deformations of the piston 1 and therefore also of the lower groove flank 8 which occur during operation of the internal combustion engine 2 can be compensated for via a corrugated course of this type. As a result, a better contact face for a piston ring can be provided than would be possible solely by way of variation of the flank inclination a. The corrugation according to FIG. 3 can also be combined with the described variants of the groove flank 8 which are shown in FIGS. 1 and 2 and build on the former, and can also be applied to upper groove flanks 7 or further groove flanks 6.

(16) Here, at least the lower groove flank 8 can also be curved at least in regions; in particular, a convex curvature is to be preferred, the inclination angle being defined in this case by way of the orthogonal 9 and a straight line which goes through two points, namely a transition 14 from a groove flank 80 to a groove bottom 16 and a transition 15 from the lower groove flank 8 to an outer circumferential face 17.

(17) In general, the embodiment according to the invention of at least the lower groove flank 8 of at least the first ring groove 6 can achieve a situation where operationally induced and temperature-induced deformations of the piston 1 can be compensated for in an improved manner and, as a result, an improved support of the piston ring can be achieved, as a result of which the oil consumption of the internal combustion engine 2 can be reduced.