EP1231374A2 - Piston for an internal combustion engine - Google Patents

Abstract

Piston (1) comprises a piston head (2), a piston shaft (3) having a pair of piston pin hubs (4, 5) and set back in the region of the piston pin hubs so that the piston head protrudes in a radial direction over the piston shaft in the region of the piston pin hubs, an inner piston chamber defined by the piston shaft and the piston head and having an oil-guiding wall forming an oil jet impact zone (10), and at least one through channel (16, 17, 22) leading outward from the inner piston chamber so that oil flowing through the through channel flows against the piston head in its region protruding over the piston shaft. Preferred Features: The oil-guiding wall changes into the inner wall of the through channel.

Description

The invention relates to a piston, in particular for an internal combustion engine a piston head, a piston skirt, which comprises piston pin hubs and in Area of these piston pin hubs is in each case set back in such a way that a segment portion of the piston head has the recessed piston skirt area overhangs.

Such a piston is known from DE 197 47 746 C1. This piston is in an oil injection opening in the area of the piston head projecting over the piston skirt educated. The introduction of the oil into this oil injection opening takes place by means of an oil jet which is directed towards the oil injection opening and which extends in an intermediate space between the piston skirt and the cylinder wall. The oil injected into the oil injection opening flows through an annular channel which extends in the area of the piston ring grooves, and thereby comes to a Outlet. The manufacture of this piston proves to be a technical one Considerations as comparatively complex.

The object of the invention is to produce an inexpensive one To create pistons, especially for an internal combustion engine, in which one Sufficient heat dissipation guaranteed with a favorable temperature profile is.

This object is achieved by a piston with a Piston head, a piston skirt that includes a pair of piston pin hubs and in Area of the piston pin hubs is formed so that the Piston head the recessed piston skirt in the area of the piston pin hubs cantilevered in the radial direction, one of the piston skirt and the piston head limited piston interior with an oil guide wall provided therein, the includes an oil jet impact zone and at least one through channel that starting from the interior of the piston extends in such a way that the Through-channel oil flowing into the piston head in its over the piston skirt outflowing area.

This makes it possible in an advantageous manner in terms of production technology mechanically and thermally highly resilient and comparatively light pistons create reliable cooling in the edge area of the piston head, especially in the area of the piston ring balcony referred to below Protrusion over the piston skirt is guaranteed. In view of that Oil supplied to the piston ring balconies immediately after impact the jet impact zone is an inner wall zone of the piston rings adjacent to the Piston sweeps and also in the through-channels close to the piston ring is guided, there is a more uniform in the area of the piston head Temperature profile.

In view of the improved temperature profile of the piston can be higher Compression ratios are allowed. Also with a view to an increase the service life of an internal combustion engine proves to be the invention Oil guidance as particularly advantageous.

According to a particularly preferred embodiment of the invention Oil guide wall formed such that this in the region of an oil flow path merges into the inner wall of the through-channel. This will in addition to an effective feed of the deflected oil jet into the through-channel an improved heat transfer to the oil is also achieved. The The entrance area of the through-channel is preferably widened like a funnel formed and arranged in an inner corner area.

A particularly high mechanical strength of the piston is advantageous Way achieved by the through-channel on the piston pin hubs is passed. This will weaken the transition area avoided between the hub area of the piston skirt and the piston head.

For this purpose, the passage channel preferably extends to the piston edge area Bulging sideways, crescent-like past the piston pin hubs.

A particularly effective heat transfer to the oil is preferred achieved in that the through-channel through the piston skirt through the Piston head runs through. Here, in particular in the area of Wall of the piston head near the combustion chamber, its thermal load be reduced effectively.

The oil guide surface is advantageously through the inner wall of the Piston shaft in interaction with the underside of the piston head and preferably comprises a channel zone which extends from the jet impact zone in extends into the through channel. This makes it possible to spray the Lead the oil almost completely into the through-channel.

For each one, the one projecting radially above the piston skirt is preferred Sections of the piston head provided at least one through channel. This makes it possible to use the piston head provided on both sides cool evenly formed piston ring balconies. In a particularly advantageous way However, two through-channels are assigned to each piston pin hub, bulging out to the side of the piston rim, the piston pin hub through the Run around the piston skirt and / or the piston head.

The jet impact zone is preferably on the thermally higher loaded piston side. With even thermal load on the piston top the beam impact zone is preferably in the interior half of the Piston skirt of the piston skirt wall that is on a working stroke on a Supports the cylinder wall.

A particularly high cooling effect is according to a special aspect of Present invention achieved in that in the interior of the piston skirt a second beam impact zone is formed. Overall, preferably four through channels are provided, which extend around the piston pin hubs extend towards the center of the piston ring balconies.

The cross section of the through channels is preferably at least 15% of the Cross-sectional area of the piston pin bore. A particularly effective one Heat transfer is achieved when the cross-section of the through channels is such is dimensioned so that this is at least the quotient from the side of one Oil spray nozzle hosed oil flow and an average oil jet velocity, equivalent.

The piston is preferably made as a cast piston. Here, the through channel be trained in a technically favorable manner. The The surface of the through-channel can be essentially cast-gray. It is also possible to manufacture the piston by a forging process. The through channel is then preferably in the context of machining post-processing educated.

The oil jet impact zone is preferably designed such that this one Division of the oil jet into at least two partial flows. Preferably one of the two partial flows to one of the two piston head protrusions directed.

According to a particularly preferred embodiment, the piston head protrusion the invention seen from the axial direction essentially one Circular segment-like shape, with the through channel directed in this way that the piston head protrusion from one of the segment tips adjacent area, directed towards the segment axis, loaded with oil.

The oil guide wall, the passage channel and the deflection zone in the area of the Piston head protrusion, preferably form an oil route with a large Oil contact surface. The oil contact is preferably by multiple deflection of the Oil intensifies especially with deflection zones with increasing curvature.

Fig. 1

eine perspektivische Ansicht des Innenbereiches eines Kolbens gemäß einer ersten Ausführungsform der Erfindung mit angedeutetem Ölführungsweg;

Fig.2

eine perspektivische Ansicht eines Kolbens gemäß einem zweiten Ausführungsbeispiel - ebenfalls von unten;

Fig.3

eine perspektivische Ansicht eines Kolbens gemäß einer dritten Ausführungsform der Erfindung von unten, mit einem wannenartig ausgebildeten Ölauslassbereich;

Fig.4

eine perspektivische Detailansicht der Ölstrahlauftreffzone gemäß einer vierten Ausführungsform der Erfindung mit einer rinnenartig gewölbten und bogenförmig zum Kolbenrand ausbauchenden, zu den Durchgangskanälen führenden Ölführungswandung;

Fig.5

eine perspektivische Ansicht des Kolbenbolzen-Nabenbereiches des Kolbenschaftes von außen gemäß einer fünften Ausführungsform der Erfindung;

Fig.6

eine perspektivische Ansicht des Kolbenringbalkons einer sechsten Ausführungsform eines erfindungsgemäßen Kolbens;

Fig.7

eine Axialschnittansicht einer siebten Ausführungsform eines erfindungsgemäßen Kolbens mit angedeutetem, schräg in den Kolbeninnenbereich gerichtetem, Ölstrahl;

Fig. 8

eine Radialschnittansicht des Kolbens nach Fig.7 auf Höhe der Kolbenbolzenachse;

Further advantageous details of the invention emerge from the following description in conjunction with the drawing. It shows:

Fig. 1

a perspective view of the interior of a piston according to a first embodiment of the invention with indicated oil route;

Fig.2

a perspective view of a piston according to a second embodiment - also from below;

Figure 3

a perspective view of a piston according to a third embodiment of the invention from below, with a trough-shaped oil outlet area;

Figure 4

a detailed perspective view of the oil jet impact zone according to a fourth embodiment of the invention with a channel-like arched and bulging to the piston rim bulging, leading to the through channels oil guide wall;

Figure 5

a perspective view of the piston pin hub area of the piston skirt from the outside according to a fifth embodiment of the invention;

Figure 6

a perspective view of the piston ring balcony of a sixth embodiment of a piston according to the invention;

Figure 7

an axial sectional view of a seventh embodiment of a piston according to the invention with indicated, obliquely directed into the piston interior, oil jet;

Fig. 8

a radial sectional view of the piston of Figure 7 at the level of the piston pin axis;

The piston 1 shown in sections in FIG. 1 from below comprises one, here only visible with regard to its underside, piston head 2 and one hereby integral piston skirt 3.

The piston skirt 3 comprises two piston pin hubs 4, 5 with aligned ones Piston pin bores 6. The piston shaft 3 is in the area of the piston pin hubs 4, 5 formed so reset that the piston head 2 the Piston shaft 3 protrudes outwards in the radial direction. The piston skirt 3 projecting area of the piston head 2 has, seen from the axial direction essentially circular segment shape. A corresponding one in this View of the piston pin axis X is largely symmetrical, circular segment is here shown as a sketch.

The region of the piston head 2 which projects radially beyond the piston skirt 3 a piston ring balcony 7. This piston ring balcony 7 comprises in its Piston pin axis X facing, lower area one of the cooling oil Cooling zone 8.

The cooling oil is supplied to the cooling zone 8 through one, into one Interior of the piston skirt 3 directed oil jet 9. This oil jet 9 is aligned in such a way that it is in the inner region of the piston skirt 3 formed beam impact zone 10 hits.

The jet impact zone 10 is located here near the edge region of the piston 1 and is through an inner surface portion of the piston skirt 3 and through lower inner surface of the piston head 2 is formed. In the area of the beam impact zone 10, the oil jet is deflected and divided into at least two Partial streams 11, 12, 13. The two partial streams 11, 12 are by the as Inner wall of the piston 1 acting on the oil guide surface to inlet openings 14, 15 guided by through channels 16, 17. The contact between the flowing Oil and the wall of the piston are maintained by the oil path is so curved that the oil becomes effective due to the radial forces is pushed against the oil guide wall.

The through channels 16, 17 extend in a crescent shape at the root region of the Piston pin hubs 4, 5 pass into a heat exchange zone K (see circle segment sketch) of the piston ring balcony 7. The loading of the lower area of the Piston ring balconies 7 take place from the area of the circular segment tips S1, S2 Piston pin axis X directed towards.

In the area of the heat exchange zone K there are a number of outlet openings 18, 19, 20, 21 intended. By webs formed between the outlet openings 18, 19, 20, 21 the area available for heat exchange is increased. The Outlet openings 18, 19 serve to discharge the oil of the partial oil flow 12. Die Outlet openings 20, 21 are used to discharge oil through another Through channel 22 is supplied by a second oil jet (not shown).

The passage channel 17 is guided such that it passes through the piston skirt 3 passes under the piston head 2. The curvature is chosen that the oil is primarily the hotter wall zones of the through-channel sweeps.

In the area of the piston ring balcony 7, this is via the through channels 17, 22nd supplied oil deflected such that this is essentially parallel to Piston stroke axis or towards the recessed wall of the piston skirt 3 is emitted. It is possible to change the geometry of the oil-affected zone of the To coordinate the piston ring balconies 7 - and thus the radiation characteristics - in such a way that a defined lubrication of the cylinder wall is achieved.

2 shows a bottom view of a second embodiment of a piston 1 shown. In this embodiment too, the piston skirt 3 is in the region of the Piston pin hubs 4, 5 reset to form piston ring balconies 7 educated.

In the piston interior jointly delimited by piston skirt 3 and piston head 2 are two in the transition area between piston skirt 3 and piston head 2 Beam impact zones 12, 24 are formed. Through these beam impact zones 12, 24, the oil jets 9, 9 'directed in pairs into the inner area of the piston divided and as corresponding partial flows to the through channels 17, 16, 22, 22 'performed. The through channels 17, 16, 22, 22 'also run around this Embodiment the respective hub area of the piston skirt 3 sickle-like and in a laterally bulging manner.

On the underside of the circular piston ring balcony 7 is the Heat exchange zone K. The heat exchange zone K comprises three outlet openings 18, 19 'and 21. The outlet openings 18, 19' and 21 essentially have one circular cross section and communicate with both neighboring ones Through channels 17, 22 so that in particular through the central outlet opening 19 'Oil can escape through the through channel 17 or the through channel 22 is supplied. The course of the through channels 17, 22 is through Dashed lines indicated. Through the arched here and into the Piston head 2 penetrating course of the through channels 17, 22 is next to one Cooling the piston ring balconies 7 also dissipates heat from the adjacent ones Piston ring zones reached.

The inlet openings 14, 15 are placed in a corner area through the Inner wall of the piston skirt 3, its inwardly projecting hub areas 4, 5 and the underside of the piston head 2 is defined. This will create a Funnel effect achieved. This funnel effect is achieved in the assembled state further supports the upper area of a connecting rod.

The piston 1 also shown in sections from below in FIG. 3 corresponds with regard to the design of the piston skirt 3 and piston head 2 limited Inner area, essentially the piston according to Fig. 2. The comments on Fig. 2 apply, apart from the differences set out below, analogous.

With the piston acc. 3 is a trough-like in the area of the piston ring balcony 7 recessed and downwardly open oil track 25 provided. This oil track 25 will Oil is applied to both sides of the corner area of the heat exchange zone K. that through the passage channels 17, 22 from the inner piston area to the Piston pin hub 4, 5 is passed around.

The geometry of the oil track 25, in particular an outer peripheral edge 26 of the trough-like depression is set such that the oil supplied in the thrown down essentially parallel to the direction of oscillation of the piston becomes. It is possible to make this oil track so large in terms of volume dimensioned that a drop of the oil - at least for the most part - only in a bottom dead center position of the piston.

In the embodiment shown here, the depth of the oil track 25 is approximately 8 mm. The width of the oil path measured in the radial direction of the piston lies preferably in the range of 4 to 6mm. This information relates to one Piston with a diameter of approx. 80mm. The measured in the circumferential direction The length of the oil path 25 essentially corresponds to at least the width b of the Piston pin hub 4.

In Figure 4 is a detailed view of a piston interior with a particular designed beam impact zone 10 shown. The beam impact zone 10 is located in a transition area between the inner wall of the piston skirt 3 and the Bottom of the piston head 2. The wall sections that come into contact with the oil form an oil guide surface G which is formed like a channel and merges into the inner surface of the through channels 17, 16. The oil guide surface G causes not only a guidance of the oil but also a heat transfer to the oil and enables cooling of the adjacent piston edge area.

The channel effect of the oil guide surface G is defined by a bead zone 27 supported. The oil guiding surface G shown here means that it hits the jet impact zone 10 incident beam on the inner edges of the piston pin bosses 4, 5 led past to a funnel-like corner area.

5 shows a further embodiment of the heat exchange zone K of the piston ring balcony 7 shown. In this embodiment, there is only one-sided Inflow to the heat exchange zone K through one from the through-channel 17 'emitted in a directional direction - indicated here by an arrow symbol - Oil flow. In the heat exchange zone K is also in this embodiment Oil path 25 bulging slightly towards the side of the piston. This Oil path 25 ends in a deflection zone 30 in which the incoming oil flow to Crankshaft of an internal combustion engine is deflected. The through channel 17 is in this embodiment in one, a piston pressure side 31 facing piston half. This will result in an improved lubricating film build-up reached during an expansion stroke.

In Figure 6 is another embodiment of a piston with one side a through-flow channel 17 ', the underside of a piston ring balcony 7, shown. In this embodiment, the oil jet 32 is in the Piston shaft 3 molded in recess 33 past the piston pin bore 6 diverted. The deflection trough 33 is designed such that the deflected Oil jet 32, essentially parallel to the cylinder wall, to the crankshaft bearing is radiated out. The oil is fed into the passage 17 ' is also carried out in this embodiment by an inside of the Piston shaft 3 provided oil guide wall, as in the previous described embodiments.

Another exemplary embodiment of a piston 1 is shown in FIGS. 7 and 8 a piston shaft 3 shown in the area of the piston pin hubs 4, 5 is laterally retracted. The piston head 2 of the piston 1 overhangs here the piston skirt 3 in the radial direction. In the area of the thus formed Piston ring balconies 7 are bulging outwards and open at the bottom Oil tracks 25 formed. The combustion chamber, which is strongly profiled here facing piston head surface is shown rotated by 90 °.

These are provided in the region of each piston ring balcony 7 oil tracks 25 Via through channels 16, 17 fed with oil, which on a near the piston rim Beam impact zone 10 through a nozzle 34 in the area of a crankshaft bearing in the interior of the piston skirt 3 is irradiated.

The irradiated oil is supplied to the through-channels 16, 17 here, too, through an oil guide wall that extends up to the through-channels 16, 17 extends. The oil path in the interior of the piston skirt 3 runs in the area near the piston rim so that effective cooling of the entire Edge area of the piston head is reached. The oil path extends radially Bulging sideways, sickle-like around the piston pin hubs 4, 5. Basically, in this embodiment, the entire face downward Inner surface of the piston head a tapering to the through-channels Oil guide surface. Through the piston ring near and - from the sections inside apart from the through-channels - open oil flow results in manufacturing technology advantageously a large heat exchange surface.

The piston according to the invention is suitable because of its improved Temperature profile and its low weight in a particularly advantageous Way for GDI engines.

The invention is not based on the exemplary embodiments described above limited. For example, it is also possible to use the oil guide surface hosed oil from several, with respect to their jet axis oblique to the cylinder axis aligned oil spray nozzles. Depending on the position of the piston can be the distance of the beam impact point relative to the through-channel vary. The oil spray nozzle can also be arranged on the connecting rod itself his.

Claims (12)

Piston with a piston head (2), a piston shaft (3), which is a pair Piston pin hubs (4, 5) and in the area of the piston pin hubs (4, 5), is set back so that the piston head (2) the reset Piston shaft (3) in the area of the piston pin hubs (4, 5) in the radial direction cantilevered, one of the piston skirt (3) and the piston head (2) limited Piston interior with an oil guide wall provided therein, the one Oil jet impact zone (10) forms, and at least one through channel (16, 17, 22, 22 '), which extends from the piston interior in such a way that the oil flowing through the through-channel (16, 17, 22, 22 ') the piston head (2) flows in its area projecting beyond the piston skirt (3). Piston according to claim 1, characterized in that the oil guide wall merges into the inner wall of the through-channel (16, 17, 22, 22 '). Piston according to claim 1 or 2, characterized in that the through channel (16, 17, 22, 22 ') in the piston head (2) or in the piston skirt (3) leads past the piston pin bosses (4, 5) to the side of the piston is. Piston according to at least one of claims 1 to 3, characterized in that in a region offset to a plane which is defined by the piston center axis and the piston pin axis, the through-channel (16, 17, 22, 22 ') the piston skirt (3rd ) through the piston head (2). Piston according to at least one of claims 1 to 4, characterized in that the through-channel (16, 17, 22, 22 ') extends past the piston pin hubs (4, 5) in a sickle-like manner. Piston according to at least one of claims 1 to 5, characterized in that the oil guiding surface is formed by the inner wall of the piston skirt (3) in interaction with the underside of the piston head (2) and comprises a channel zone (G) which extends from the jet impact zone (10 ) extends into the through channel (16, 17, 22, 22 '). Piston according to at least one of claims 1 to 6, characterized in that the oil jet impact zone (10) is designed such that it causes the oil jet (9) to be divided into at least two partial flows (11, 12, 13). Piston according to at least one of claims 1 to 7, characterized in that in each case one of the two partial flows (11, 12) is passed to one of the piston ring balconies (7). Piston according to at least one of claims 1 to 7, characterized in that at least one through channel (16, 17, 22, 22 ') is provided for each of the piston ring balconies (7). Piston according to at least one of claims 1 to 9, characterized in that a second jet impact zone is formed in the inner region of the piston skirt (3). Piston according to at least one of claims 1 to 10, characterized in that a total of four through-channels (16, 17, 22, 22 ') are provided which surround the piston pin hubs (4, 5) to the center of gravity of the underside of the respective piston ring balcony (7) extend there. Piston according to at least one of claims 1 to 11, characterized in that the cross section of the through-channels (16, 17, 22, 22 ') is at least 15% of the cross-sectional area of the piston pin bore (6).

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