PISTON FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A piston for an internal combustion engine may include at least one oil ring groove configured to receive an oil scraper ring. The at least one oil ring groove may have an upper groove flank, a lower groove flank, and a groove base. The at least one oil ring groove may be structured to be asymmetrical and deeper in a radial direction in a region of the lower groove flank. The piston may also include an oil outflow channel structured and arranged to fluidically communicate with an oil collecting chamber disposed in a spine of the oil scraper ring. A connecting point between at least one of (i) the at least one oil ring groove and the oil outflow channel, and (ii) the oil collecting chamber and the oil outflow channel may be disposed exclusively in the lower groove flank.

Claims

1. A piston for an internal combustion engine, comprising: having at least one oil ring groove configured to receive an oil scraper ring, the at least one oil ring groove having an upper groove flank facing toward a piston crown, a lower groove flank averted from the piston crown, and a groove bases; the at least one oil ring groove structured to be asymmetrical and deeper in a radial direction in a region of the lower groove flank; an oil outflow channel structured and arranged to fluidically communicate with an oil collecting chamber, disposed in a spine of the oil scraper ring; and wherein a connecting point between at least one of (i) the at least one oil ring groove and the oil outflow channel, and (ii) the oil collecting chamber and the oil outflow channel is disposed exclusively in the lower groove flank.

2. The piston according to claim 1, wherein the oil outflow channel extends parallel to a piston axis.

3. The piston according to claim 1, wherein the oil outflow channel extends obliquely with respect to a piston axis and is obliquely connected to the lower groove flank.

4. The piston according to claim 1, wherein the oil outflow channel extends orthogonally with respect to a piston axis.

5. The piston according to claim 1, wherein the upper groove flank includes a shoulder projecting into the at least one oil ring groove, the shoulder structured and arranged as a stop which limits a protrusion depth of the oil scraper ring into the at least one oil ring groove.

6. The piston according to claim 1, wherein: the upper groove flank and the lower groove flank each include a finish-machined surface disposed only in a region which comes into contact with the oil scraper ring when the oil scraper ring is received in the at least one oil ring groove; and the upper groove flank, the lower groove flank, and the groove base each have a pre-machined surface in a region of the oil collecting chamber.

7. The piston according to claim 1, wherein the groove base extends obliquely with respect to a piston axis.

8. The piston according to claim 1, wherein the groove base includes, in a lower inner region, a radially inwardly directed depression.

9. A method for producing a piston, comprising: drilling an oil outflow channel into a body of the piston; forming an asymmetrical oil ring groove in the body of the piston, the oil ring groove configured to receive an oil scraper ring, the oil ring groove having a groove base, an upper grove flank and a lower groove flank, the upper groove flank facing toward a piston crown, the lower groove flank averted from the piston crown, the oil ring groove configured to receive an oil scraper ring and to be deeper in a radial direction in a region of the lower groove flank; providing, exclusively in the lower groove flank, at least one of (i) a communicating connecting point between the oil ring groove and the oil outflow channel, and (ii) a communicating connecting point between the oil outflow channel and an oil collecting chamber disposed in a spine of the oil scraper ring; and wherein the oil outflow channel is structured and arranged to fluidically communicate with the oil collecting chamber of the oil scraper ring.

10. The method according to claim 9, further comprising finish-machining the upper groove flank and the lower groove flank such that (i) the upper groove flank and the lower groove flank have a finish-machined surface only in a region which comes into contact with the oil scraper ring when the oil scraper ring is received in the oil ring groove, and (ii) the upper groove flank, the lower groove flank, and the groove base have a surface in a region of the oil collecting chamber that remains pre-machined.

11. The method according to claim 9, wherein forming the oil ring groove includes cutting the oil ring groove into the body of the piston.

12. The piston according to claim 1, wherein: the oil outflow channel extends parallel to a piston axis; and the oil outflow channel extends orthogonally with respect to the lower groove flank.

13. The piston according to claim 1, wherein: the oil outflow channel extends obliquely with respect to a piston axis; the oil outflow channel extends obliquely with respect to the lower groove flank; and the oil outflow channel is obliquely connected to the lower groove flank.

14. The piston according to claim 1, wherein: the oil outflow channel extends orthogonally with respect to a piston axis; and the oil outflow channel extends outward in the radial direction in the lower groove flank.

15. A piston for an internal combustion engine, comprising: a piston crown; an upper groove flank; a lower groove flank disposed further from the piston crown than the upper groove flank; a groove base extending between and connecting the upper groove flank and the lower groove flank; a circumferentially extending oil ring groove defined by the upper groove flank, the lower groove flank, and the groove base, the oil ring groove opening in a radially outward direction; the oil ring groove having a greater radial depth in a region of the lower groove flank than in a region of the upper groove flank such that the oil ring groove is asymmetrical; an oil outflow channel structured and arranged to fluidically communicate with an oil collecting chamber disposed in a spine of an oil scraper ring arrangeable within the oil ring groove; and wherein a connecting point between the oil ring groove and the oil outflow channel is disposed exclusively in the lower groove flank.

16. The piston according to claim 15, wherein the lower groove flank extends further in a radially inward direction than the upper groove flank such that the groove base extends transversely relative to a piston axis.

17. The piston according to claim 15, wherein the groove base includes a radially inward protruding depression.

18. The piston according to claim 15, further comprising a piston body, wherein: the oil ring groove is disposed in an outer circumferential surface of the piston body; and the oil outflow channel extends from the lower groove flank to the outer circumferential surface of the piston body.

19. The piston according to claim 15, wherein: the oil outflow channel extends parallel to a piston axis; and the oil outflow channel extends orthogonally with respect to the lower groove flank.

20. The piston according to claim 15, wherein: the oil outflow channel extends obliquely with respect to a piston axis; and the oil outflow channel extends obliquely with respect to the lower groove flank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the drawing, in each case schematically:

[0021] FIG. 1 is a sectional illustration through a piston according to the invention in the region of an oil ring groove,

[0022] FIG. 2 is an illustration as in FIG. 1, but with a differently formed oil ring groove and differently formed oil outflow channel,

[0023] FIG. 3 is an alternative illustration in relation to FIGS. 1 and 2.

DETAILED DESCRIPTION

[0024] Correspondingly to FIGS. 1 to 3, a piston 1 according to the invention for an internal combustion engine 2 (not otherwise shown), in particular in a motor vehicle, has at least one oil ring groove 3 for receiving an oil scraper ring 4, which oil ring groove has an upper groove flank 6, facing toward a piston crown 5, and a lower groove flank 7, averted from the piston crown 5, and a groove base 8. It is self-evidently also possible for yet further piston rings 9 (cf. FIGS. 2 and 3), such as for example compression rings, to be arranged in other ring grooves 10. The oil ring groove 3 is now of asymmetrical form and is formed so as to be deeper in a radial direction 11, that is to say orthogonally with respect to a piston axis 12, in the region of the lower groove flank 7. The groove base 8 thus extends radially further outward in the region of the upper groove flank 6 than in the region of the lower groove flank 7. In the spine of the oil scraper ring 4, that is to say radially within the latter, there is provided an oil collecting chamber 13 via which oil which has been scraped off a cylinder wall (not illustrated) by the oil scraper ring 4 can be collected and discharged via an oil outflow channel 14 which has a communicating connection to the oil collecting chamber 13. According to the invention, it is now the case that a connecting point 15 via which the oil collecting chamber 13 communicates with the oil outflow channel 14 is provided exclusively in the region of the lower groove flank 7, such that the connecting point 15 does not at any point project for example into the groove base 8, whereby the connecting point 15 is of substantially planar form and forms no three-dimensional edge structure.

[0025] Here, different orientations of the oil outflow channel 14 are illustrated in FIGS. 1 to 3, wherein the oil outflow channel 14 illustrated in FIG. 1 runs parallel to the piston axis 12 and in particular orthogonally with respect to the lower groove flank 7, whereas the oil outflow channel 14 illustrated in FIG. 2 runs obliquely with respect to the piston axis 12 and in particular also obliquely with respect to the lower groove flank 7 and is thus obliquely connected to the latter. The oil outflow channel 14 as per FIG. 3 runs orthogonally with respect to the piston axis 12, in particular in the radial direction 11, within the lower groove flank 7, such that the lower groove flank 7 is hollowed out in the region of the oil outflow channel 14. Here, within the groove flank 7 self-evidently actually means below the latter.

[0026] Considering the embodiment of the piston 1 according to the invention as per FIG. 1, it can be seen that the upper groove flank 6 has a shoulder 16 which projects into the oil ring groove 3 and which forms a stop for the oil scraper ring 4 and which limits a protrusion depth of the oil scraper ring 4 into the oil ring groove 3. In this way, it is possible in particular for a so-called ring pop out, in the case of which the oil scraper ring engages to too deep an extent into the oil ring groove 3 and is lifted out of the oil ring groove 3 on the opposite side, to be avoided. As an alternative to such a shoulder 16, the groove base 8 may also run or be formed obliquely with respect to the piston axis 12, as illustrated in FIG. 2, whereby the oil scraper ring 4 can in turn protrude into the oil ring groove 3 only to such an extent that it abuts against the groove base 8 at the transition between the upper groove flank 6 and said groove base. In the embodiment illustrated in FIG. 3, the groove base 8 has, in a lower, inner region, a radially inwardly directed depression 17, wherein, otherwise, the groove base 8 runs substantially parallel to the piston axis 12. However, all embodiments have in common the fact that the protrusion depth of the oil scraper ring 4 into the ring groove 3 is limited and, even in the case of a maximum protrusion depth, the oil collecting chamber 13 for collecting the oil always remains in the spine of the oil scraper ring. The oil scraper ring 4 may in this case have two oil-scraping lips 18 and a spring element 19 which preloads the oil scraper ring 4 in a radially outward direction and presses it against the cylinder wall in order to prevents a reliable scraping-off of the oil and in particular a passage thereof into a combustion chamber.

[0027] The oil ring groove 3 according to the invention is in this case produced as follows: firstly, a piston blank of the piston 1 is produced, and the oil outflow channel 14 is formed in, for example by drilling. Subsequently, the asymmetrical oil ring groove 3, which is formed so as to be deeper in a radial direction in the region of the lower groove flank 7, is formed in, for example cut in or ground in by means of a chip-removing tool, such that a communicating connecting point 15 between the oil ring groove 3 or the oil collecting chamber 13 and the oil outflow channel 14 lies exclusively in the lower groove flank 7. In this way, it is possible in particular to avoid a three-dimensional edge structure, which can be deburred only with difficulty. The upper and the lower groove flank 6, 7 are in this case also finish-machined or fine-machined, for example ground, preferably only in a regions which comes into contact with the oil scraper ring 4, whereas the upper groove flank, the lower groove flank 7 and the groove base 8 in the region of the oil collecting chamber 16, in which there is no contact with the oil scraper ring 4, remain in a pre-machined state, for example after a process of turning the grooves, whereby the production process is made considerably simpler and less expensive.

[0028] With the piston 1 according to the invention, it is possible, owing to the asymmetrical ring groove 3, for an inadvertent lifting of the oil scraper ring 4 out of the ring groove 3, in particular during installation and transport, to be avoided, and at the same time for an oil collecting chamber 13 to be created which always remains irrespective of the protrusion depth of the oil scraper ring 4 into the oil ring groove 3, which oil collecting chamber communicates via the base-side connecting point 15, which lies exclusively in the region of the lower groove flank 7, with the oil outflow channel 14. By means of the connecting point 15 which lies exclusively in the lower groove flank 7, it is possible in particular to create a planar connecting point 15 without three-dimensional edge structure, whereby in particular the production and also the finish machining are considerably simplified.