DE102018208898A1 - Reciprocating piston for a reciprocating internal combustion engine and use of a reciprocating piston in a reciprocating internal combustion engine - Google Patents

Abstract

The invention relates to a reciprocating piston for a reciprocating internal combustion engine having a base body (12) and a combustion chamber surface (16), wherein within the base body (12) at least one cooling duct network (32) is provided, wherein the cooling duct network (32) at least one - in the radial direction of the Viewed base body (12) - arranged on the inside inflow region (34) and a plurality of - starting from the inflow region (34) - in the radial direction in each case outwardly extending mini-cooling channels (42), wherein the mini-cooling channels (42) a maximum cross-sectional width of 3 mm. In this case, the inflow region (34) comprises an annular channel (40) or a central reservoir and the mini-cooling channels (42) extend outwardly from this annular channel (40) or the central reservoir in the radial direction, wherein the annular channel (40) or the central reservoir is designed in the manner of a coolant collecting space and has a cross-sectional area corresponding to at least 1.5 times the largest cross-sectional area of the largest mini-cooling channel (42).

Description

The invention relates to a reciprocating piston for a reciprocating internal combustion engine according to the preamble of claim 1. The invention also relates to the use of such a reciprocating piston in a reciprocating internal combustion engine.

Out DE 34 44 661 A1 a liquid-cooled piston for an internal combustion engine is known, wherein the piston in the region below a piston crown arranged in a star shape, has substantially radially extending cooling channels. The cooling channels are connected to a ring channel disposed radially on the outer circumference of the piston, radially behind a piston skirt, with coolant entering the cooling channels by means of a coolant injection nozzle via a coolant supply and the annular channel. For discharging the coolant, a piston-axial coolant discharge is provided, wherein the coolant discharge discharges directly into the crank chamber arranged below the piston crown.

Out US 2017/0298862 A1 a piston is known, which has an annular cooling channel. Coolant is fed into the piston via a connecting rod and a bolt connecting the connecting rod and the piston in the area of the piston pin hub. The annular cooling passage is connected to the piston pin hub via a connecting passage extending in the axial direction. Furthermore, an outflow channel is provided, via which the coolant can flow out into the region immediately below a piston crown.

From the not yet published patent application DE 10 2018 201 556.2 is a reciprocating piston according to the preamble of claim 1 is known. Experiments have shown that such a reciprocating piston can not be used with a standard oil supply, because it can happen that in certain operating conditions, the amount of coolant for sufficient flow through all the cooling channels is insufficient.

The invention has for its object to provide a reciprocating piston for a reciprocating internal combustion engine available that allow improved cooling of reciprocating and cooling further improving use in a reciprocating internal combustion engine, especially when this reciprocating piston to be cooled by means of a standard oil supply.

The object is achieved according to the invention with the features of the independent claims. Further practical embodiments and advantages of the invention are described in connection with the dependent claims.

An inventive reciprocating piston for a reciprocating internal combustion engine has a base body with a combustion chamber surface. As a combustion chamber surface that surface is referred to, which is oriented in the arrangement of such a reciprocating piston in a reciprocating internal combustion engine to a combustion chamber and the combustion chamber viewed in the axial direction in one direction (usually down) dynamically limited. The combustion chamber surface is sometimes referred to as upper piston crown. In most cases, the combustion chamber surface has a piston recess in the form of a depression in a middle region, viewed in the radial direction of the piston. Within the base body of the reciprocating piston is provided in the reciprocating piston according to the invention at least one cooling duct network, i. such a cooling duct network is arranged either as a separately formed element and / or formed in one piece. If both variants are realized, i. the "and" combination of the above sentence is realized, the cooling duct network is partially formed separately and arranged in the reciprocating piston and partially formed integrally in the reciprocating piston. A cooling duct network in the sense of the invention is understood to mean a design of cooling ducts in which, starting from an entry region into the cooling duct network, all the ducts belonging to this cooling duct network are connected to one another in a flow-conducting manner. About a cooling duct network so far flowed liquid is distributed within the "network". The cooling duct network has at least one inflow region, which is arranged on the inside in the radial direction of the main body, and a multiplicity of mini-cooling passages extending outwardly in the radial direction, starting from the inflow region. The mini-cooling channels have a maximum cross-sectional width of 3 mm. In this case, the inflow region comprises an annular channel or a central reservoir, and the mini-cooling channels extend outwardly from this annular channel or the central reservoir in the radial direction, wherein the annular channel or the central reservoir is designed in the manner of a coolant collecting space and a cross-sectional area which is at least 1.5 times the largest cross-sectional area of the largest mini-cooling channel. Preferably, the cross-sectional area is 1.8 times, 2.0 times, 2.5 times, 3.0 times or more compared to the largest cross-sectional area of the largest mini-cooling channel. In other words, the annular channel or the central reservoir is designed so that regardless of the operating condition of an internal combustion engine always a sufficient amount of coolant, in particular oil, can be kept in the annular channel or the central reservoir to the mini-cooling channels in all directions sufficient to supply with coolant or oil or to flow through.

The term central reservoir should be interpreted broadly in this context. In this respect, not only a tank-like cavity is to be understood, but also kreisbogenförrmige or geometrically differently shaped channels with sufficiently large cross-sectional area, by means of which the fluidly connected thereto mini-cooling channels can be sufficiently supplied with coolant, which extend in different radial directions. Preferably, a reservoir is designed and fluidly connected directly to mini-cooling channels that a mini-channel duct extending like an umbrella can be supplied from this reservoir.

When a cooling fluid in the form of oil is used as the coolant, the term coolant-collecting space can also be replaced by oil-collecting space.

When using reciprocating piston in reciprocating internal combustion engines, the base body of the reciprocating heated, in particular the combustion chamber side strong, the highest temperature viewed in the radial direction centrally or centrally of the combustion chamber surface occurs, i. where, in many cases, a piston recess is formed. The temperature of the combustion chamber surface or the body decreases - in particular in uncooled piston - viewed in the radial direction from radially inward to outside. In the case of the reciprocating piston according to the invention, it is provided to convey coolant through a inflow region arranged on the inside as directly as possible to the region of the main body with the maximum temperature and to convey it radially outward therefrom. By a plurality of outwardly extending in the radial direction mini-cooling channels, the cooling liquid is also finely ramified and passed the surface to be cooled with many individual channels penetrating radially outwards, to cool even more radially outward portions of the body , The cooling liquid thus flows from a radially inner region in the direction of a radially outer region. Thus, the cooling liquid can be used optimally for cooling, because the flow direction of the cooling liquid is thus adapted to the temperature gradient of the base body during operation of a reciprocating internal combustion engine.

The formation of mini-cooling channels with a maximum cross-sectional width of 3 mm, makes it possible to provide a particularly large, available for cooling surface, so that there is a particularly efficient cooling of the body. As the cross-sectional width of the mini-cooling channels, the largest distance perpendicular to the main flow direction of the cooling liquid is designated by the mini-cooling channels. In particular, the mini-cooling channels have a maximum cross-sectional width of 2.5 mm and preferably the cross-sectional width of the mini-cooling channels is at least 1 mm. The mini-cooling channels are formed in cross-section, in particular circular. Alternatively, the mini-cooling channels may also be polygonal in cross-section or have a different cross-sectional shape.

Due to the formation of mini-cooling channels and cooling channels extending from the inside to the outside, the formation of so-called "hot spots", i. particularly hot areas, are targeted and efficiently counteracted on the base body of the reciprocating piston, in particular by arranging the mini-cooling channels so that at full load or other defined load condition results in a uniform temperature Temperarturverteilung on the combustion chamber surface. This also reduces the risk of pre-ignition - especially in gasoline engines.

In a practical embodiment of a reciprocating piston according to the invention, a backflow safety device is provided in the inflow region, in the annular channel and / or in the central reservoir. Under such a backflow are generally all means to understand, which completely or at least partially counteract a backflow of coolant, which is once directly in front of or in the annular channel or directly before or in the central reservoir.

By way of example only, reference will be made to the formation of a vertical jump (e.g., by means of a step-like, vertical and / or oblique dam wall), a valve, and an upwardly curved passageway (reverse siphon).

It should be noted that an upwardly curved channel course is often due to a limited height of the piston crown not only to a small extent feasible.

The use of a valve is associated with additional costs and weight.

It is particularly preferred in this respect to provide a vertical jump such that a return flow is possible only after overcoming a certain height level and only if temporarily no further coolant or only coolant flows with a not sufficiently large pressure in the inflow region.

In a further practical embodiment of a reciprocating piston according to the invention, the cross-sectional width and / or the cross-sectional shape and / or the cross-sectional area of the mini-cooling channels is formed differently depending on their distance from the inflow region - viewed in the flow direction. This design variant can be particularly advantageously used to control the mass flow or volume flow through the individual mini-cooling channels in a desired manner, for example, to strive for a uniform flow through all mini-cooling channels and / or by design of the corresponding partial flows a uniform temperature distribution in the piston crown to reach.

Alternatively or in addition to the above-mentioned design possibility individual mini-cooling channels, the connection height level of the mini-cooling channels to the annular channel or the central reservoir depending on their distance from the inflow - viewed in the direction of flow - be chosen differently high. For example, the port height level may be set to zero by extending a mini-cooling channel from the lowest level of an annular channel or central reservoir. Or, the height level may be raised to a higher connection height level by a step of height H to reduce the amount of refrigerant flowing into a mini-cooling channel, and as the connection height level increases, the amount of air flowing into the corresponding mini-cooling channel Coolant is reduced.

Alternatively or in addition, in at least one mini-cooling channel in an adjoining the annular channel or the central reservoir initial portion may be provided a height jump to the amount of inflowing coolant in this mini-cooling channel with respect to another mini-cooling channel without a jump or with a lower height jump and / or height connection level to reduce.

The cooling of a reciprocating piston according to the invention can be further improved if the mini-cooling channels lead to a radially outwardly arranged outflow opening or to a plurality of radially outwardly arranged outflow openings. In this case, this one outflow opening or the plurality of outflow openings are in particular at least partially aligned such that coolant exiting through the outflow opening passes directly or indirectly on an outer side of a piston skirt. In this context, a piston skirt is understood to mean, in particular, a section of the base body which is spaced apart-in particular below-a piston crown and the combustion chamber surface and generally has one or more guide surfaces for guiding the piston along a cylinder wall. The cooling liquid thus reaches - if at all - only indirectly (i.e., not directly) into the crankcase below the piston skirt. By reaching from the outside of the piston skirt cooling liquid, the piston skirt is cooled on the outside. Also, a formation of oil deposits and corking on the piston skirt by excessive temperatures can be counteracted so effectively. The coolant also improves the lubrication of the piston skirt and reduces its friction with the cylinder wall.

The outflow openings are in particular aligned such that the cooling liquid flows directly and thus directly from above onto the radial outer side of the piston skirt. Alternatively, the outflow openings can also be aligned such that the cooling liquid initially collides against the cylinder wall and rebounds from there in the direction of the piston skirt. Preferably, the mini-cooling channels or the at least one mini-cooling channel in the region immediately adjacent to the outflow opening extend predominantly horizontally, i. essentially at an angle to the horizontal of at most 30 ° and preferably of not more than 20 ° and more preferably of not more than 10 °. In this context, the horizontal plane is the direction perpendicular to the cylinder axis, along which the piston moves in the reciprocating internal combustion engine.

It is also possible to orient the outflow openings in the inner piston area downwards or otherwise orientated so that the escaping oil does not additionally lubricate and / or cool the cylinder wall, in particular in order to avoid excessive oil supply.

In a further practical embodiment of a reciprocating piston according to the invention, a gap between a radially outer portion of the piston skirt and a radially outer portion of a piston crown formed on the body at least over part of the circumference, and at least one mini-cooling channel leads into the region of the gap between the Piston shirt and the piston crown. By the above-mentioned range is meant that in the axial direction on the one side by the piston skirt and on the other side by the lower piston crown limited area. In the above-mentioned design of a reciprocating piston with a gap between the piston skirt and the piston crown, thermal decoupling of the piston skirt from the piston crown is realized. This design is particularly suitable for constructive aspects to direct the coolant directly to the piston skirt.

A particularly efficient cooling of the piston according to the invention is achieved if in the base body at least eight (and preferably at least nine, at least ten or more) are formed in the radial direction extending mini-cooling channels, because then there is already a relatively close-meshed distribution network with good area penetration. In particular, the mini-cooling channels extend from the inflow region to eight, nine, ten or more corresponding outflow openings. It is also possible to design the mini-cooling channels in such a way that they additionally branch out one or more times radially outwards, for example by initially being located from a region arranged radially inward 10 Mini-cooling channels radially outward extend into a radially central region and then branch out these mini-cooling channels, starting from this central region in each case two or more further channels. In this case, the cross-sectional width can be adjusted so that the flow velocity in the region of the branches does not change as much as possible.

The smaller the maximum cross-sectional width is selected, the finer the "branches" of the cooling duct network can be formed. Conversely, the resulting pressure losses in the "branches" or mini-cooling channels increase with decreasing cross-sectional width. For this reason, the maximum cross-sectional width is between 1 mm and 4 mm, preferably between 1 mm and 3 mm.

It is preferred if the projected area of the cooling channels, based on the cross-sectional area of the piston, is at least 20 percent, preferably at least 25 percent and more preferably at least 30 percent.

In a further practical embodiment of a reciprocating piston according to the invention, the inflow region comprises an annular channel or a central reservoir, and the cooling channels extend outwardly from this annular channel or the central reservoir in the radial direction. By "ring" is meant in this context preferably a closed, but also only part-ring-shaped designs, i. also semi-annular or other arcuate annular channel designs. By means of such, preferably at least semicircular trained annular channels a good and homogeneous distribution of the cooling liquid can be achieved in the individual cooling channels, which allows a - considered in the circumferential direction - uniform piston crown cooling. By a central reservoir, for example, hollow-spherical or otherwise shaped hollow-shaped, chamber-like structures are meant, from the outer sides of which the mini-cooling channels extend in the radial direction outwards.

A structurally particularly simple design results if at least two, flow-conducting not - or at least only up to a radially inwardly disposed network distribution point - interconnected cooling channel networks are formed in the body.

In particular, two or more cooling duct nets can be arranged so that the piston crown is largely penetrated evenly by channels of the cooling duct nets. For example, a first cooling duct network and a second cooling duct network may extend over two halves of the cross-sectional area of the main body.

In a particularly practical embodiment, the cooling channel networks are mirror images of each other. The two cooling channel networks which are not connected to one another in a flow-conducting manner preferably further comprise two inflow regions which are separated from one another and which can be fed independently of one another. The formation of such separated inflow regions and cooling channel networks is particularly advantageous if the formation of the inflow region in the main body in a central position, i. radially center of the combustion chamber surface (in the region of the cylinder center axis) space engineering and / or constructive not or only with great effort to realize. This is the case, in particular, when the injection takes place via a piston injection nozzle (this will be explained in more detail below), since it can not be arranged centrally below the piston crown due to the connecting rod.

In particular, in conjunction with an injection of coolant via a piston nozzle, it may also be advantageous to provide only an annular channel or a central reservoir, which has a diameter in relation to the piston diameter or a large maximum cross-sectional width, for example at least 20 percent. at least 30 percent at least 40 percent or even at least 50 percent of the piston diameter. In this case, the mini-cooling channels can, starting from such a relatively large annular channel or central reservoir accordingly only within the remaining area outside the annular channel or central reservoir, i. For example, over a radially measured range of a maximum of 50 percent of the piston diameter, if the central reservoir or the annular channel already extends over about 5p percent.

In a further practical embodiment, the at least one inflow region can extend starting from an inflow opening which is formed in the lateral surface of a piston pin hub. Such an embodiment of a reciprocating piston according to the invention is particularly suitable for supplying the cooling duct network with cooling liquid via a connecting rod functionally connected to the piston. In particular, it is provided to form two flow channels not interconnected cooling channel networks, wherein the inflow openings are formed on different sides of the connecting rod in the lateral surface of the piston pin hub. If the connecting rod is hollow inside, cooling fluid can be guided within the connecting rod in the direction of the reciprocating piston. The reciprocating piston and the connecting rod are preferably connected by means of a bolt, wherein the bolt is in particular designed such that cooling fluid can be conveyed through the bolt to the at least one inflow opening. For this purpose, in particular at least one - in particular funnel-like - channel in the bolt be designed so that regardless of a pivotal movement between the connecting rod, pin and piston permanently sufficient coolant can be conveyed in the direction of the piston.

The at least one inflow opening extends in particular over an angular range of the circumference of the lateral surface of the piston pin hub. The angular range corresponds at least to the angular range over which the bolt is pivoted during movement of the connecting rod relative to the reciprocating piston. The bolt is connected in particular by means of press fit with the connecting rod and rotates relative to the reciprocating piston. In particular, the inflow opening extends over at least 20 ° and preferably over at least 30 ° of the circumference of the lateral surface of the piston pin hub.

To promote the cooling liquid through the connecting rod in the base body of the reciprocating piston, a pump may optionally be provided in a variant of the reciprocating piston according to the invention, with which a sufficiently high pressure is generated to fill at least 20 percent of the cooling duct network with cooling liquid during operation of the reciprocating internal combustion engine , As such a pump, a standard oil pump used for other purposes of a reciprocating internal combustion engine may be provided, but it may also be provided an additional pump for one or more reciprocating piston according to the invention, which is used exclusively or primarily for the supply of the cooling duct network. It is also possible to ensure the supply of the cooling duct network in any other way.

Preferably, at least 25 percent, at least 30 percent or at least 40 percent, 50 percent or even 75 percent of the cooling duct network is filled with coolant. The cooling duct network can also be completely (i.e., 100 percent) filled with cooling fluid, resulting in particularly efficient cooling due to maximum flow through the cooling duct network with cooling fluid. By increasing the pressure generated by the pump and the resulting flow rate, the cooling capacity can then be adjusted as needed, provided that the pump is controllable and / or regulated. If cooling liquid is introduced into the main body via a connecting rod, cooling liquid can be conveyed continuously, with high pressure and optionally also flow-controlled or flow-controlled active into the main body of the reciprocating piston. The present invention, however, primarily relates to applications in which the cooling fluid reaches the reciprocating piston at ambient pressure but applied with kinetic energy.

In this respect, the invention relates in particular to those embodiments in which the inflow region extends from a region of the lower piston crown, which is spaced from the piston pin hub. Such an area is provided in particular adjacent to the piston pin hub and in particular as possible - as viewed in the radial direction - arranged centrally in the body, for example within a radius corresponding to a maximum of half the radius of the piston. In this embodiment, the supply of the cooling duct network with coolant takes place in particular via at least one piston injection nozzle. In this case, the piston injection nozzle is preferably arranged below the lower piston crown in such a way that cooling liquid can be injected upwards into the cooling duct network. It is also preferred in this embodiment if two or more cooling channel networks, which are not connected to one another in terms of flow, are formed in the base body. More preferably, at least one separate piston spray nozzle is provided per cooling channel network. The introduction of cooling liquid into the base body via a piston injection nozzle is structurally very easy to implement, in particular because the cooling liquid does not have to be guided by elements moving relative to one another.

In a further practical embodiment, the contour of the mini-cooling channels is at least partially adapted to the contour of the combustion chamber surface such that the axial distance of the mini-cooling channels to the combustion chamber surface is within a predetermined tolerance window. In particular, the contour of the mini-cooling channels is adapted to a combustion chamber surface with a piston recess, so that the mini-cooling channels also have a trough-like contour. Preferably, both the axial distance of the mini-cooling channels to the combustion chamber surface and to the lower piston crown within a predetermined tolerance window. "Within the specified tolerance window" means here in particular that the distance deviation between the combustion chamber surface and / or the lower piston crown is not more than 20 percent, preferably not more than 15 percent and particularly preferably not more than 10 percent. The mini-cooling channels preferably extend over at least 20 percent, preferably at least 25 percent and in particular at least 30 percent of the diameter of the piston head substantially horizontally. As a range, a radial extension of the mini-cooling channels between 20 and 70 percent of the piston diameter is particularly suitable, in particular a range between 20 and 50 percent. This means in particular the radially inward regions of the piston crown. More preferably, the mini-cooling channels are at least partially adapted to the contour of the combustion chamber surface, ie, the distance between the combustion chamber surface and the respective mini-cooling channels is approximately constant over at least a partial area, preferably over the entire radial extent of the mini-cooling channels.

In particular, the inflow region is formed by an inflow opening, which is connected to the annular channel via a connecting channel extending in the axial direction. Starting from the annular channel, the mini-cooling channels extend in the radial direction to the outside, wherein the contour of the cooling channels is adapted to the contour of the combustion chamber surface with a piston recess. In a radially outer region, the mini-cooling passages initially extend in an axial section substantially in the axial direction and then in particular lead predominantly horizontally in a horizontal section into a region between the piston crown and the piston skirt. Alternatively, the mini-cooling channels may extend only partially horizontally or in sections in the purely axial direction of the piston. The orientation can be arbitrarily adapted to the cooling requirements and the respective geometry of the piston, in particular in the region of the piston crown.

The invention also relates to the use of a reciprocating piston as described above in a reciprocating internal combustion engine. In this case, the cooling liquid is introduced into the lifting piston via an inflow region arranged radially on the inside and is discharged outward in the radial direction through a multiplicity of cooling channels extending in the radial direction. It is caused by this use a particularly efficient cooling of the reciprocating piston, since the cooling liquid first cools the particularly hot, radially central region of the combustion chamber surface and flows from there to the outside to the colder edge regions.

As already mentioned above, the cooling liquid is preferably introduced such that the at least one cooling channel network is filled to at least 20 percent with cooling liquid. Preferably, the cooling duct network is at least 30 percent or at least 40 percent, 50 percent or even at least 75 percent, and more preferably 100 percent filled with coolant. That is, the cooling liquid is introduced into the body at a sufficiently high pressure and / or speed to completely convey the cooling fluid through the mini-cooling channels. Overall, such an efficient cooling is achieved independently of a shaker effect.

• 1 eine erste Ausführungsform eines erfindungsgemäßen Hubkolbens in einer Seitenansicht,
• 2 den Hubkolben aus 1 in einer Draufsicht,
• 3 eine Hälfte des Hubkolbens aus 1 und 2 in einer perspektivischen Ansicht von schräg oben,
• 4 den Hubkolben aus den 1 bis 3, wobei ein Kolbenhemd in einem Längsschnitt gemäß Linie IV-IV aus 2 dargestellt ist, und der in 4 mit B gekennzeichnete Bereich teilweise weggeschnitten ist,
• 5 den Hubkolben aus den 1 bis 4 in einem Längsschnitt gemäß Linie V-V aus 3,
• 6 nur das isoliert dargestellte Kühlkanalnetz des Hubkolbens gemäß den 1 bis 5 in einer perspektivischen Ansicht,
• 7 eine schematische Darstellung der Kühlmittelversorgung des Kühlkanalnetzes aus 6 mit einer Kolbenspritzdüse,
• 8 das Kühlkanalnetz aus 6 in einer Ansicht von oben mit Strömungspfeilen,
• 9 nur einen Teil des Kühlkanalnetzes aus 6 mit einer Detaildarstellung des Einströmbereichs mit Strömungspfeilen in einer Seitenansicht,
• 10 eine weitere Ausführungsform eines erfindungsgemäßen Hubkolbens in einer perspektivischen Ansicht von schräg oben und
• 11 den Hubkolben aus 10 ohne den Kolbenboden in einer perspektivischen Ansicht von schräg oben.

Further practical embodiments of the invention are described below in conjunction with the drawings. Show it:

• 1 A first embodiment of a reciprocating piston according to the invention in a side view,
• 2 the reciprocating piston 1 in a plan view,
• 3 one half of the reciprocating 1 and 2 in a perspective view obliquely from above,
• 4 the piston from the 1 to 3 , wherein a piston skirt in a longitudinal section along line IV-IV out 2 is shown, and the in 4 Part B is partially cut away,
• 5 the piston from the 1 to 4 in a longitudinal section along the line VV out 3 .
• 6 only the isolated cooling duct network of the reciprocating piston according to the 1 to 5 in a perspective view,
• 7 a schematic representation of the coolant supply of the cooling duct network 6 with a piston nozzle,
• 8th the cooling duct network off 6 in a top view with flow arrows,
• 9 only a part of the cooling duct network 6 with a detailed representation of the inflow region with flow arrows in a side view,
• 10 a further embodiment of a reciprocating piston according to the invention in a perspective view obliquely from above and
• 11 the reciprocating piston 10 without the piston crown in a perspective view obliquely from above.

In conjunction with the 1 to 9 is an embodiment of a reciprocating piston according to the invention 10 exemplified. Here are the most relevant to the invention details in the 6 . 8th and 9 and will be explained in connection with these figures.

The reciprocating piston 10 serves the known arrangement in a reciprocating internal combustion engine, not shown. In reciprocating internal combustion engines, the reciprocating piston moves 10 viewed in the axial direction in the combustion chamber along the in 1 shown double arrow up and down to the volume of one with the reciprocating piston 10 To change the bounded combustion chamber and thus in particular to enable compression phases and decompression phases.

The reciprocating piston 10 includes a main body 12 with a piston bottom 14 , The surface directed towards the combustion chamber subsequently becomes the combustion chamber surface 16 called and can also as upper piston crown 16 be designated. In this illustrated embodiment, the combustion chamber surface comprises 16 a radially centrally arranged piston recess 18 , The side facing away from the combustion chamber of the piston crown 14 is hereinafter referred to as the lower piston crown 20 designated.

Furthermore, the basic body comprises 12 a piston shirt 22 which viewed in the axial direction below the piston crown 14 is arranged. In the present case is the piston skirt 22 via a piston pin hub 24 with the piston bottom 14 connected. The piston pin hub 24 serves for the pivotable connection of the reciprocating piston 10 with a connecting rod (not shown) by means of a bolt (also not shown). In a radially outer region is an axially extending gap 30 between the lower piston crown 20 and the piston shirt 22 trained (cf. 1 and 4 ), so the piston shirt 22 largely thermally from the piston crown 14 is decoupled. The gap 30 In this case extends over the entire area between the upper piston crown 16 and the piston shirt 22 ,

As in 2 are clearly recognizable, are in the main body 12 of the reciprocating piston 10 two flow channel non-interconnected cooling duct networks 32 formed, wherein the cooling channel networks 32 each over half of the piston crown 14 extend.

A cooling duct network 32 each includes a - viewed in the radial direction - arranged on the inside inflow 34 ,

7 shows a schematic representation of the supply of the cooling duct network 32 with coolant by means of a piston spray nozzle 52 , about which the cooling liquid in the main body 12 is introduced. The piston nozzle 52 is spaced from the respective inflow opening 36 arranged so that cooling liquid as a jet in the direction of the inflow opening 36 is directed. The coolant accordingly emerges from the piston nozzle 52 that they at least partially - as predominantly or even completely - in the inflow opening 36 is encouraged.

For such an embodiment with piston spray nozzle 52 can the cooling duct nets 32 opposite the in 2 shown cooling channel networks 32 Alternatively, be arranged rotated by 90 ° about the cylinder axis, so that an injection from below the lower piston crown 20 viewed in the radial direction further outward and spaced from the piston pin hub 24 he follows. It is accepted that the injection is spaced from the center of the combustion chamber surface 16 he follows. Optionally, the geometry of the cooling duct network 32 be adjusted so that cooling fluid from a radially slightly further inlet opening 36 first into a central area of the combustion chamber surface 16 and from there - possibly after further promotion towards the combustion chamber area 16 - via the mini cooling channels 42 flows in the radial direction to the outside.

The inflow area 34 the cooling duct nets 32 is in each case via an inflow opening 36 and a from the inflow opening 36 in the axial direction upwardly extending connecting channel 38 and a substantially horizontally extending annular channel 40 educated. Starting from the ring channel 40 extends radially outward a plurality of mini-cooling channels 42 , In the present case are per cooling duct network 32 ten, extending in the radial direction mini-cooling channels 42 trained (cf. 2 and 3 ). The cross-sectional width of the mini-cooling channels 42 is 2.5 mm in the embodiment shown.

As if from a synopsis of 1 . 2 . 5 and 6 clearly visible, extend the mini-cooling channels 42 to radially outwardly arranged outflow openings 44 , The outflow openings 44 are in the present case viewed in the axial direction in the region of the gap 30 between the piston skirt 22 and the lower piston crown 20 arranged, ie the mini-cooling channels 42 open into the area of the gap 30 between the lower piston crown 20 and the piston shirt 22 , The through the mini-cooling channels 42 flowing cooling liquid is thereby guided such that they pass through the outflow openings 44 directly on the outside of the piston skirt 22 arrives.

The respective geometric design and the respective directions of the individual mini-cooling channels 42 are in particular in 5 and 6 good to see. Starting from the ring channel 40 extend the mini-cooling channels 42 initially largely horizontally outward. The contour of the mini-cooling channels 42 is the contour of the combustion chamber surface 16 with the piston recess 18 customized. In particular, the distance between the mini-cooling channels 42 and the combustion chamber area 16 with the piston recess 18 within a radially inner region in which the mini-cooling channels 42 radially to outside extend constantly because of the mini-cooling channels 42 in the same small curvature radially outward and upward as the combustion chamber surface 16 ,

In this embodiment, the distance of the mini-cooling channels 42 to the lower piston crown 20 in a radially inner region constant, where this parallel to the combustion chamber surface 16 runs.

In the embodiment shown, the mini-cooling channels extend 42 viewed in the radial direction about 80 percent of the radially extending width (ie, the diameter) of the combustion chamber surface 16 , Looking only at the area in which the mini-cooling channels 42 approximately parallel to the combustion chamber surface 16 extend in a predominantly radial direction, extend the mini-cooling channels 42 in the radial direction over about 60 percent of the width of the combustion chamber surface 16 ,

In one of the predominantly radially outwardly oriented portion of the mini-cooling channels 42 subsequent area are the mini-cooling channels 42 in an axial section 46 oriented predominantly in the axial direction, before moving into a further horizontal section 48 above the piston skirt 22 go over there and on the outside each to a discharge opening 44 to lead.

The inflow openings 36 are preferably each funnel-shaped, ie, the cross-sectional area increases in the direction of the piston injection nozzle 52 ,

As if from a synopsis of 6 . 8th and 9 can be seen, the cross-sectional area of the annular channel (annular channel cross-sectional area) A _R recognizable larger than the cross-sectional area of the mini-cooling channels A _K (Mini cooling channel cross-sectional area). The annular channel cross-sectional area A _R here corresponds approximately to 5 times the mini-cooling channel cross-sectional area A _K ,

In 9 It can be seen that in the radial direction to the annular channel 40 leading inflow area 34 as a backflow protection 28 a height jump 56 in the form of a stowage wall 58 is trained. The stowage wall 58 has an obliquely rising course and extends over the height h (see. 9 ). With this dam wall 58 prevents coolant that in the marked with the arrow E inflow 34 has passed, flows back according to the dashed arrow R, as long as the cooling liquid in the inflow 34 does not reach a height level that is above the height h.

To a sufficiently large flow of coolant in the annular channel 40 to initiate, is the cross-sectional area of the inflow 34 chosen to be significantly larger than the largest mini-cooling channel cross-sectional area A _K ,

As in 8th is clearly recognizable, the flow is proceeding over the inflow area 34 in the ring channel 40 and there in the direction of the arrows R ₁ . R ₂ and R ₃ directed. The flow velocity in the direction of the arrows R ₁ . R ₂ and R ₃ can be used as a control parameter for the amount of each in the mini-cooling channels 42 inflowing coolant can be used. It should be noted that the flow velocity increases with increasing distance in the direction of the arrows R ₁ . R ₂ and R ₃ decreases.

1. a) Die Querschnittsweite und/oder die Querschnittsform und/oder die Querschnittsfläche der Mini-Kühlkanäle 42 ist abhängig von deren Abstand vom Einströmbereich 34 (d.h. einer Mündungsstelle 60 in einen Ringkanal 40 oder ein zentrales Reservoir) unterschiedlich groß ausgebildet, wobei vorzugsweise die Querschnittsfläche mit zunehmendem Abstand von einer Mündungsstelle 60 zunimmt.
2. b) Das Anschluss-Höhenniveau der Mini-Kühlkanäle 42 an den Ringkanal 40 oder an das zentrale Reservoir ist abhängig von dem Abstand einer Mündungsstelle 60 unterschiedlich hoch gewählt, wobei vorzugsweise das Anschluss-Höhenniveau mit zunehmendem Abstand von einer Mündungsstelle 60 abnimmt.
3. c) In mindestens einem Mini-Kühlkanal 42 ist in einem sich an den Ringkanal 40 oder das zentrale Reservoir anschließenden Anfangsabschnitt ein Höhensprung vorgesehen, wobei insbesondere die Höhe solcher Höhensprünge mit zunehmendem Abstand von einer Mündungsstelle 60 abnimmt.

Nevertheless, a uniform flow and in particular a uniform mass flow and / or flow through the mini-cooling channels 42 In the radial direction outwards and thus to achieve a uniform heat dissipation, one or more of the following configurations are optionally implemented:

1. a) The cross-sectional width and / or the cross-sectional shape and / or the cross-sectional area of the mini-cooling channels 42 depends on their distance from the inflow area 34 (ie an estuarine site 60 in a ring channel 40 or a central reservoir) of different sizes, wherein preferably the cross-sectional area with increasing distance from an orifice 60 increases.
2. b) The connection height level of the mini-cooling channels 42 to the ring channel 40 or to the central reservoir is dependent on the distance of a confluence point 60 chosen different high, preferably the connection height level with increasing distance from an orifice 60 decreases.
3. c) In at least one mini cooling channel 42 is in a to the ring channel 40 or the central reservoir subsequent initial section provided a height jump, in particular the height of such height jumps with increasing distance from an orifice 60 decreases.

In the 10 and 11 is another embodiment of a reciprocating piston 10 shown. This embodiment of the reciprocating piston 10 differs from the first embodiment in particular in that the piston skirt 22 on the outside with the lower piston crown 20 connected is. It is therefore not a gap 30 between the lower piston crown 20 and the piston shirt 22 educated. The outflow openings 44 are formed so that they through the piston skirt 22 Pass the coolant over the outside of the piston skirt 22 can get.

The features of the invention disclosed in the present description, in the drawings and in the claims may be essential both individually and in any desired combinations for the realization of the invention in its various embodiments. The invention may be varied within the scope of the claims and in consideration of the knowledge of the person skilled in the art.

LIST OF REFERENCE NUMBERS

10

reciprocating

12

body

14

piston crown

16

Combustion chamber surface = upper piston crown

18

piston bowl

20

lower piston bottom

22

skirt

24

piston pin

28

return valve

30

gap

32

Cooling channel network

34

inflow

36

inflow

38

connecting channel

40

annular channel

42

Mini cooling channel

44

outflow

46

axial

48

Horizontal section

50

channel

52

piston spray nozzle

54

lateral surface

56

jump in height

58

retaining wall

60

opening point

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3444661 A1 [0002]
• US 2017/0298862 A1 [0003]
• DE 102018201556 [0004]

Claims (10)

Reciprocating piston for a reciprocating internal combustion engine having a base body (12) and a combustion chamber surface (16), wherein inside the base body (12) at least one cooling channel network (32) is provided, wherein the cooling channel network (32) at least one - in the radial direction of the base body (12) considered - arranged on the inside inflow region (34) and a plurality of - starting from the inflow region (34) - in the radial direction in each case outwardly extending mini-cooling channels (42), wherein the mini-cooling channels (42) has a maximum cross-sectional width of mm, wherein the inflow region (34) comprises an annular channel (40) or a central reservoir and the mini-cooling channels (42) extending outwardly from this annular channel (40) or the central reservoir viewed in the radial direction. characterized in that the annular channel (40) or the central reservoir is designed in the manner of a coolant collecting space and has a cross-sectional area corresponding to at least 1.5 times the largest cross-sectional area of the largest mini-cooling channel (42). Reciprocating piston according to the preceding claim, characterized in that in the inflow region (34), in the annular channel (40) and / or in the central reservoir a return flow is provided. Reciprocating piston according to the preceding claim, characterized in that a height jump (56), a valve or an upwardly curved channel course is provided as backflow protection. Lifting piston according to one of the preceding claims, characterized in that the cross-sectional width and / or the cross-sectional shape and / or the cross-sectional area of the mini-cooling channels (42) is designed differently depending on their distance from the inflow region (34). Lifting piston according to one of the preceding claims, characterized in that the connection height level of the mini-cooling channels (42) to the annular channel (40) or the central reservoir depending on their distance from the inflow region (34) is selected to be different. Reciprocating piston according to one of the preceding claims, characterized in that in at least one mini-cooling channel (42) in a subsequent to the annular channel (40) or the central reservoir initial portion of a height jump (56) is provided to the amount of in this mini -Kühlkanal (42) compared to another mini cooling channel without height jump (56) or with a smaller height jump (56) to reduce. Reciprocating piston according to one of the preceding claims, characterized in that the mini-cooling channels (42) lead to a radially outwardly arranged outflow opening (44) or to a plurality of radially outwardly arranged outflow openings (44), this outflow opening (44) or these multiple outflow openings (44). 44) are at least partially aligned such that through the outflow opening (44) exiting cooling fluid passes directly or indirectly on the outside of a piston skirt (22). Lifting piston according to one of the preceding claims, characterized in that on the base body (12) at least over part of the circumference, a gap (30) between a radially outer portion of the piston skirt (22) and a radially outer portion of a piston head (14) is formed and at least one mini-cooling channel (42) in the region of the gap (30) between the piston skirt (22) and the lower piston head (20) leads. Reciprocating piston according to one of the preceding claims, characterized in that in the base body (12) at least eight extending in the radial direction mini-cooling channels (42) are formed and / or that in the base body (12) at least two, not conductively interconnected cooling channel networks (32) are formed. Use of a reciprocating piston (10) according to one of the preceding Claims 1 to 9 in a reciprocating internal combustion engine, characterized in that coolant is introduced via a radially inwardly arranged inflow region (34) in the reciprocating piston (10) and discharged under ambient pressure by a plurality of radially extending mini-cooling channels (42) in the radial direction to the outside becomes.

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