PISTON OF AN INTERNAL COMBUSTION ENGINE

Abstract

A piston of an internal combustion engine is disclosed. The piston includes a piston head with a piston bowl, a ring part and an annular cooling channel arranged between the ring part and the piston bowl. A closure element is provided to close the cooling channel in a direction away from the piston bowl. At least one guiding element is arranged in the cooling channel. The at least one guiding element provides a lug facing in a direction of an inner cooling channel wall and disposed at least partially circumferentially. The lug of the at least one guiding element is structured and arranged to direct cooling oil present in the cooling channel towards an upper region of the inner cooling channel wall relative to the closure element to facilitate cooling the upper region.

Claims

1. A piston of an internal combustion engine, comprising: a piston head including a piston bowl, a ring part and an annular cooling channel arranged between the ring part and the piston bowl, wherein the cooling channel is closed in a direction away from the piston bowl by a closure element; and at least one guiding element arranged in the cooling channel, the at least one guiding element providing a lug facing in a direction of an inner cooling channel wall and disposed at least partially circumferentially, wherein the lug of the at least one guiding element is structured and arranged to direct cooling oil present in the cooling channel towards an upper region of the inner cooling channel wall relative to the closure element to facilitate cooling the upper region.

2. The piston as claimed in claim 1, wherein the at least one guiding element is clamped and held between an underside of the ring part and the closure element.

3. The piston as claimed in claim 1, wherein the at least one guiding element is clamped and held between an upper cooling channel wall and the closure element.

4. The piston as claimed in claim 1, wherein the at least one guiding element provides a wall inclined in relation to a piston axis, and wherein the wall together with an outer cooling channel wall defines a funnel-shaped cross section and in a lower region has outlet openings for cooling oil, the lower region disposed between the lug and the closure element.

5. The piston as claimed in claim 1, wherein the lug has interruptions in a circumferential direction of the cooling channel, structured and arranged to facilitate selective cooling of defined circumferential segments of the inner cooling channel wall.

6. The piston as claimed in claim 5, wherein the lug has folded edges on the interruptions.

7. The piston as claimed in claim 1, wherein the at least one guiding element is composed of a steel sheet or a plastic.

8. The piston as claimed in claim 1, further comprising a catch funnel for catching a jet of cooling oil molded onto the at least one guiding element.

9. The piston as claimed in claim 1, further comprising a jet splitter for splitting a jet of cooling oil arranged on the at least one guiding element.

10. The piston as claimed in claim 9, wherein the jet splitter has at least one guide contour facing in a circumferential direction of the cooling channel.

11. The piston as claimed in claim 10, wherein the at least one guide contour of the jet splitter includes two guide contours positioned opposite to one another and facing in the circumferential direction of the cooling channel.

12. The piston as claimed in claim 11, wherein the two guide contours are arranged at a distance from one another to provide a passage therebetween for a jet of cooling oil.

13. The piston as claimed in claim 10, wherein at least one of the jet splitter and the at least one guide contour is glued, welded or soldered to the at least one guiding element.

14. An internal combustion engine, comprising: at least one piston including: a piston head including a piston bowl, a ring part and an annular cooling channel arranged between the ring part and the piston bowl; a closure element structured and arranged to close the cooling channel in a direction away from the piston bowl; and at least one guiding element arranged in the cooling channel, the at least one guiding element providing a lug facing in a direction of an inner cooling channel wall and disposed at least partially circumferentially, wherein the lug of the at least one guiding element is structured and arranged to direct cooling oil present in the cooling channel towards an upper region of the inner cooling channel wall relative to the closure element to facilitate cooling the upper region.

15. The internal combustion engine as claimed in claim 14, wherein the lug of the at least one guiding element is interrupted in a circumferential direction of the cooling channel, and wherein an injection jet of fuel in an associated cylinder is aimed at the lug via a circumferential interruption in the lug.

16. The internal combustion engine as claimed in claim 14, wherein the at least one guiding element provides a wall inclined in relation to a piston axis, and wherein the wall together with an outer cooling channel wall of the cooling channel defines a funnel-shaped cross section and has at least one outlet opening for cooling oil in a lower region between the lug and the closure element.

17. The internal combustion engine as claimed in claim 14, wherein the at least one guiding element is clamped and held between an underside of the ring part and the closure element.

18. The internal combustion engine as claimed in claim 14, wherein the at least one guiding element is clamped and held between an upper cooling channel wall and the closure element.

19. The internal combustion engine as claimed in claim 14, wherein the at least one piston includes a catch funnel for catching a jet of cooling oil molded onto the at least one guiding element.

20. A piston of an internal combustion engine, comprising: a piston head including a piston bowl, a ring part and an annular cooling channel arranged between the ring part and the piston bowl; a closure element structured and arranged to close the cooling channel in a direction away from the piston bowl; at least one guiding element arranged in the cooling channel, the at least one guiding element providing a lug facing in a direction of an inner cooling channel wall and disposed at least partially circumferentially, wherein the lug of the at least one guiding element is structured and arranged to direct cooling oil present in the cooling channel towards an upper region of the inner cooling channel wall relative to the closure element to facilitate cooling the upper region; wherein the at least one guiding element provides a wall inclined in relation to a piston axis; and wherein the at least one guiding element is clamped and held between an underside of the ring part and the closure element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the figures, in each case schematically,

[0019] FIG. 1 depicts a sectioned view through an inventive piston of an internal combustion engine having an inventive guiding element corresponding to a first embodiment,

[0020] FIGS. 2 and 3 depict a representation as in FIG. 1, although with further possible embodiments of the inventive guiding element,

[0021] FIG. 4 depicts a sectioned view through an inventive piston in the region of a cooling channel and a lug of the guiding element,

[0022] FIG. 5 depicts a flow path of cooling oil along the lug,

[0023] FIG. 6 depicts a sectioned view through an inventive piston in the region of an interruption,

[0024] FIG. 7 depicts a representation as in FIG. 5, although with a flow path of the cooling oil in the interruption,

[0025] FIGS. 8 and 9 depict further representations of a guiding element, as in FIG. 1,

[0026] FIG. 10 depicts an annularly closed guiding element having lugs that are interrupted in the circumferential direction and a catch funnel formed thereon,

[0027] FIG. 11 depicts a representation as in FIG. 10, although without interruptions,

[0028] FIG. 12 depicts a sectioned view through an inventive piston of an internal combustion engine having a guiding element according to FIG. 11,

[0029] FIG. 13 depicts a sectioned view through an inventive piston, in which a closure element is configured integrally with the piston,

[0030] FIG. 14 depicts a sectioned view through an inventive piston having a jet splitter with two guide contours.

DETAILED DESCRIPTION

[0031] According to FIGS. 1 to 9 and 12 to 14, an inventive piston 1 of an internal combustion engine 2 exhibits a piston head 3 having a piston bowl 4 and a ring part 5. Circumferential grooves for accommodating piston rings (not depicted) are provided in this case in the region of the ring part 5. A substantially annular cooling channel 6, which is closed at the bottom by a closure element 7, is arranged between the ring part 5 and the piston bowl 4. In FIG. 13, the closure element 7 in this case is configured integrally with the piston 1, whereas it is configured as a separate component in the other representations. According to the invention, there is arranged in the cooling channel 6 at least one guiding element 8, which has a lug 10 facing in the direction of an inner cooling channel wall 9 and disposed at least partially circumferentially, which is oriented in such a way that cooling oil 11 present in the cooling channel 6 is directed in the direction of an upper region 12 of the inner cooling channel wall 9 and thus provides enhanced cooling of said region 12.

[0032] The region 12 here is subjected to the greatest temperature loading during operation of the internal combustion engine 2, for which reason the latent risk is always present in this region 12 of any cooling oil 11 impinging there being carbonized and, for example, adhering in the manner of a carbonizing oil film to the inner cooling channel wall 9 in the region 12 and even forming a thermally insulating film there, which impairs any heat transfer and thus any cooling of the piston 1.

[0033] With regard to the guiding elements 8 according to FIGS. 1, 2 and 4 to 9, 12 and 13, it can be appreciated that the respective guiding element 8 depicted there is clamped between an underside of the ring part 5 and the at least one closure element 7 and is secured thereby in position in the cooling channel 6. For this purpose, the guiding element 8 exhibits a flange 22, via which it is clamped between the closure element 7 and the underside of the ring part 5. Of course, the guiding element 8 can also be connected, for example welded, soldered or glued, with its lower flange 22 to the closure element 7 or to the underside of the ring part 5.

[0034] In a preferred embodiment, depicted in FIGS. 1 to 9, the underlying piston 1 is configured, in the manner known from EP 1 372 904 B1, in a single piece with a cooling channel 6 that is open at the bottom, which is closed by an annular steel sheet as a closure element 7. This is preferably supported resiliently under pre-load on protruding parts of the piston 1. However, the present invention can also be used advantageously with welded pistons 1, wherein the closure element 7 in this case, as depicted in FIG. 13, can also be a protruding part of one of the piston parts, here a lower piston part 24, which, after welding at least one contact zone to the other piston part, bears against an upper piston part 25 here. The guiding element 8 can be attached to one of the piston parts 24, 25 before welding, preferably by means of a laser. Apart from materially bonded connections, such as welding, soldering or gluing, the guiding element 8 can also be clamped between the two piston parts 24, 25 if these are in contact with one another under preloading.

[0035] In practical terms, what is more, two or more separated guiding element segments 8a, 8b may, of course, also be necessary and provided, in order for the guiding element 8 to be able to move around the shaft regions as it is being inserted. An even subdivision into two segments 8a, 8b of 180° respectively is preferred and is realized especially if the guiding element 8 exhibits no outlet openings or an even number of outlet openings 17 or interruptions 18 in the circumferential direction. The guiding element 8 in this case is preferably divided by two radial cuts, as depicted in FIG. 11. An uneven division of the guiding element 8, other than 180°, can also be provided, therefore, in particular in the case of an unequal number of fuel jets 19 or outlet openings 17 or interruptions 18. A single, annularly closed guiding element 8 with only a single abutment is likewise conceivable, whereby it can be inserted by bending slightly upwards into the cooling channel 6. Above all, in the case of pistons 1 welded in the region of the cooling channel 6, consisting of an upper part and a lower part 25, 24, a single, annularly closed guiding element 8 can be used entirely without ban abutment, which guiding element is positioned on one of the piston parts 25, 24 before welding in the axial direction.

[0036] Notwithstanding the foregoing, a piston 1 is depicted in FIG. 3, in which the at least one guiding element 8 is clamped between an upper cooling channel wall 13 and the at least one closure element 7 and is held in place in this way. The guiding element 8 depicted according to FIG. 3, like the guiding element 8 depicted in the other figures, can be made of steel sheet or plastic and, as a result, can exhibit only a comparatively low weight, wherein it is also conceivable as an alternative, of course, for the guiding element 8 depicted in each case, in particular in FIG. 3, to be configured as a solid profile. A low weight of the guiding element 8 is of considerable advantage, in particular since the piston 1 is subjected to high accelerations during operation of the internal combustion engine 2 and, for this reason, even small increases in weight have a negative impact on the efficiency of the internal combustion engine 2.

[0037] With regard to the guiding elements 8 according to FIGS. 2 and 4 to 7, 10, 12 and 13, it can be appreciated that the respective at least one guiding element 8 depicted therein forms an inclined and radially inward-facing wall 15 or wall section 15 in relation to a piston axis 14 which corresponds substantially to the lug 10, wherein the wall 15 together with an outer cooling channel wall 16 forms a funnel-shaped cross section and, in a lower region, forms outlet openings 17 for the exit of the collected cooling oil 11. If suchlike outlet openings 17 are arranged in a relatively steep region of the guiding element 8, the oil as it flows in also receives an impulse in the inward direction. As a result, the narrowing of the guiding element 8 from bottom to top causes not only the concentration of an upward-facing oil flow 11 in the particularly hot bowl lip region 12, but also a rotation of the oil flow 11 in its entirety around the guiding element 8 (radially inside-upwards and outside-downwards), which contributes to more uniform heat distribution along the cooling channel surface.

[0038] The outlet openings 17 in this case can also be interruptions 18 arranged in the circumferential direction between the lugs 10. The interruptions 18 interrupt the individual lugs 10 of the guiding element 8 in the circumferential direction, whereby selective cooling of defined regions 12 of the inner cooling channel wall 9 is facilitated. This has a major role to play in particular in the use of the inventive piston 1 in a diesel internal combustion engine, since the diesel fuel is injected into this engine in the form of a jet by a diesel fuel injection nozzle, wherein higher temperature loadings occur in conjunction with the ignition of the mixture, in particular in the region of these individual fuel jets 19. No high temperatures occur between the individual jets 19, when viewed in the circumferential direction, such that temperature stresses may occur in the piston 1. It is consequently of particular advantage, if the individual lugs 10 of the guiding element 8 are oriented in such a way that they are in alignment with a possible fuel injection jet 19 in the radial direction (see FIGS. 2 and 3), whereby the piston bowl 4 can be cooled more effectively, especially in the regions 12 of the inner cooling channel wall 9, in which the highest temperature loading also occurs.

[0039] With further regard to the lugs 10, it can be appreciated in particular therefrom that folded edges 20 are provided on the interruptions 18, that is to say laterally on the lugs 10, which likewise support the direction of the jet of cooling oil 11 in the direction of the upper region 12 of the inner cooling channel wall 9.

[0040] With additional regard to the guiding element 8 according to FIG. 10, it can be appreciated therefrom that a catch funnel 21 for catching a jet of cooling oil is formed, in particular being formed integrally therewith. A suchlike catch funnel 21 can be guided in this case through a corresponding opening, for example an inlet opening, in the closure element 7. The single-piece configuration of the catch funnel 21 with the guiding element 8, in particular enables the component diversity and, associated therewith, the assembly, storage and logistics costs to be reduced. In addition, the guiding element 8 can be arranged in a specific positional relationship to the closure element 7 and secured against rotation in the circumferential direction by the catch funnel 21, which engages in the inlet opening. In an advantageous manner, the catch funnel 21 can be arranged on one of the abutments of a guiding element 8, wherein a half catch funnel, which forms the catch funnel 21 engaging over the abutments together with the adjoining half-funnel, can be configured on each side of the abutment by bending up of the steel sheet. This simplifies the forming operation, since no enclosed openings need to be configured in the guiding element 8 in this case. In addition, a suchlike catch funnel engaging over the abutments can serve both of the parts concerned of the guiding element 8 as a protection against rotation, when it engages in the inlet opening of the closure element 7.

[0041] The closure element 7 itself can be fixed in its position in the circumferential direction in a manner known per se by protruding fixing lugs, which engage in recesses in the piston 1. In a similar manner, a guiding element 8 can also be positioned directly in the circumferential direction in its desired positional relationship to the piston 1 and secured against rotation, in which it has its own radially protruding fixing lugs 26, depicted in FIG. 11, which engage in corresponding recesses, for example, a milled recess at the lower end of the ring part 5.

[0042] With the inventive guiding element 8, which, as depicted in FIG. 10, can be configured as a closed ring or can also be assembled from a number of individual guiding element segments, it is possible for the first time to provide the locally restricted and predefined cooling of individual regions 12 of a piston bowl 4 of the piston 1 which are exposed to a particularly high temperature loading. Because of the guiding element 8 and the lugs 10 of same which protrude radially inwards, an annular cross section is maintained in the region of the inner cooling channel wall 9, through which the cooling oil 11 flows along close to the inner cooling channel wall 9, concentrated at the critical point, that is to say in the upper region 12, and cools these intensively before it flows to the outside, for example via a round configuration of the upper cooling channel wall 13. Without the inventive guiding element 8, a purely up-and-down movement would be available for the full width of the channel, but with low cooling intensity.

[0043] With regard to FIG. 14, it can be appreciated that a jet splitter 27 for splitting the jet of cooling oil 11 is arranged on at least one guiding element 8. This can have at least one guide contour 28 facing in the circumferential direction of the cooling channel 6. According to FIG. 14, however, the jet splitter 27 has two guide contours 28 positioned opposite one another and facing in the circumferential direction of the cooling channel 6.

[0044] The two guide contours 28 are arranged at a distance from one another, so that a jet of cooling oil 11 is able to pass between the two. As a result, the region directly above the jet splitter 27 can also be supplied with cooling oil 11 and cooled. The jet splitter 27 and/or the at least one guide contour 28 is/are glued, welded or soldered to the guiding element 8. There is a particular preference here for a single-piece configuration of the guide contours 28 with the guiding element 7. The guiding element 7 could thus be made as a cost-effective sheet metal part.

[0045] Generally, is it also conceivable for the at least one guiding element 8 to have slots 23, which, on the one hand, permit greater flexibility of the guiding element 8 and, on the other hand and under certain circumstances, form outlet openings 17 at the same time.