阅读说明：本技术 用于往复活塞式内燃机的往复活塞以及往复活塞在往复活塞式内燃机中的用途 (Reciprocating piston for a reciprocating piston internal combustion engine and use of a reciprocating piston in a reciprocating piston internal combustion engine ) 是由 P·I·乌尔祖亚托雷斯 M·比尔 A·勒宁 于 2019-01-23 设计创作，主要内容包括：本发明涉及一种带有基体(12)和燃烧室面(16)的用于往复活塞式内燃机的往复活塞,其中,在基体(12)内设置有至少一个冷却通道网络(32),其中,冷却通道网络(32)具有-在基体(12)的径向上观察-布置在内侧的至少一个流入区域(34)和-从流入区域(34)出发-在径向上相应地向外延伸的大量微型冷却通道(42),其中,微型冷却通道(42)具有3mm的最大横截面宽度。本发明还涉及往复活塞(10)在往复活塞式内燃机中的用途。(The invention relates to a reciprocating piston for a reciprocating piston internal combustion engine, comprising a main body (12) and a combustion chamber surface (16), wherein at least one cooling channel network (32) is provided in the main body (12), wherein the cooling channel network (32) comprises at least one inflow region (34) arranged on the inside, viewed in the radial direction of the main body (12), and a plurality of micro cooling channels (42) extending radially outward from the inflow region (34), wherein the micro cooling channels (42) have a maximum cross-sectional width of 3 mm. The invention also relates to the use of a reciprocating piston (10) in a reciprocating piston internal combustion engine.)

1. Reciprocating piston for a reciprocating piston internal combustion engine, having a main body (12) and a combustion chamber surface (16), wherein at least one cooling channel network (32) is arranged in the main body (12),

it is characterized in that the preparation method is characterized in that,

the cooling channel network (32) has-viewed in the radial direction of the base body (12) -at least one inflow region (34) arranged on the inside and-proceeding from the inflow region (34) -a plurality of micro cooling channels (42) extending radially correspondingly outwards, wherein the micro cooling channels (42) have a maximum cross-sectional width of 3 mm.

2. The reciprocating piston of the preceding claim, wherein the cooling channel (42) opens into one outflow opening (44) arranged radially outside or into a plurality of outflow openings (44) arranged radially outside, wherein the outflow opening (44) or the outflow openings (44) are at least partially oriented such that the cooling liquid exiting through the outflow opening (44) directly or indirectly reaches on the outside of the piston skirt (22).

3. The reciprocating piston as claimed in one of the preceding claims, characterized in that a gap (30) between a radially outer section of the piston skirt (22) and a radially outer section of the piston bottom (14) is formed at the base body (12) at least over a part of the circumference, and at least one cooling channel (42) opens into the region of the gap (30) between the piston skirt (22) and the piston bottom (20).

4. A reciprocating piston as claimed in any one of the preceding claims, characterized in that at least eight radially extending cooling channels (42) are configured in the basic body (12).

5. A reciprocating piston according to any of the preceding claims, characterized in that the inflow region (34) comprises an annular channel (40) or a central reservoir and the cooling channel (42) extends outwards seen in radial direction from the annular channel (40) or the central reservoir.

6. The reciprocating piston as claimed in any of the preceding claims, wherein at least two cooling channel networks (32) which are connected to one another in a fluid-tight manner are formed in the basic body (12).

7. The reciprocating piston according to any of the preceding claims, characterized in that the at least one inflow region (34) extends from an inflow opening (36) which is configured in a side face (54) of the piston pin bushing (24).

8. The reciprocating piston of any preceding claim, wherein the inflow region (34) extends from a region of the piston bottom (14) spaced from the piston pin bushing (24).

9. A reciprocating piston according to any of the preceding claims, wherein the contour of the cooling channel (42) is at least partially adapted to the contour of the combustion chamber face (16) such that the axial spacing of the cooling channel (42) relative to the combustion chamber face (16) is within a predefined tolerance window.

10. Use of a reciprocating piston (10) in a reciprocating piston internal combustion engine according to any of the preceding claims 1-9, characterized in that coolant is introduced into the reciprocating piston (12) via an inflow region (34) arranged radially inside and is conducted out radially outwards through a number of radially extending cooling channels (42).

Technical Field

The present invention relates to a reciprocating piston for a reciprocating piston 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 piston internal combustion engine.

Background

DE 3444661 a1 discloses a liquid-cooled piston for an internal combustion engine, wherein the piston has cooling channels which extend substantially radially and are arranged in a star shape in the region below the piston base. The cooling channel is connected to an annular channel (Ringkanl) arranged radially behind the piston skirt at the outer periphery of the piston, wherein the coolant is passed into the cooling channel by means of a coolant nozzle via a coolant supply and the annular channel. For the removal of the coolant, a coolant removal device is provided in the axial direction of the piston, wherein the coolant removal device opens directly into a crankcase arranged below the piston bottom.

A piston with an annular cooling channel is known from US 2017/0298862 a 1. The coolant is conducted into the piston in the region of the piston pin bushing (Kolbenbolzennabe) via the connecting rod and the pin (Bolzen) connecting the connecting rod and the piston. The annular cooling channel is connected to the piston pin bushing via a connecting channel extending in the axial direction. Furthermore, an outflow channel is provided, via which the coolant can flow out into a region directly below the piston bottom.

Disclosure of Invention

The object of the invention is to provide a reciprocating piston for a reciprocating piston internal combustion engine, which achieves improved cooling of the reciprocating piston in the reciprocating piston internal combustion engine and the use of the cooling is further improved.

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

A reciprocating piston for a reciprocating piston internal combustion engine according to the invention has a basic body with a combustion chamber face. Such a face which, in the case of such a reciprocating piston arrangement in a reciprocating piston internal combustion engine, is oriented towards the combustion chamber and which, viewed in the axial direction, dynamically defines the combustion chamber in a certain direction (generally downwards) is referred to as combustion chamber face. The combustion chamber face is sometimes also referred to as the upper piston bottom. In most cases, the combustion chamber face has-viewed in the radial direction of the piston-a piston recess in the form of a recess (Kolbenmulde) in the middle region. In the reciprocating piston according to the invention, at least one cooling channel network is provided in the basic body of the reciprocating piston, i.e. such a cooling channel network is arranged as a separately constructed element and/or is constructed in one piece. If both variants are implemented, that is to say the "and" combination of the preceding sentence, the cooling channel network sections are constructed separately and arranged in the reciprocating piston and the sections are constructed in one piece in the reciprocating piston. A cooling channel network in the sense of the present invention is understood to be a configuration of the cooling channel in which, starting from an entry region into the cooling channel network, all channels belonging to the cooling channel network are connected to one another in a flow-conducting manner. In this regard, the incoming liquid is distributed within the "network" via a network of cooling channels. The cooling channel network has-viewed in the radial direction of the base body-at least one inflow region arranged on the inside and-proceeding from the inflow region-a multiplicity of miniature cooling channels extending correspondingly outward in the radial direction. The micro cooling channels here have a maximum cross-sectional width of 3 mm.

In the case of the use of reciprocating pistons in reciprocating piston internal combustion engines, the base body of the reciprocating piston heats up strongly, in particular on the combustion chamber side, with the highest temperatures occurring in the center or in the middle of the combustion chamber surface, as viewed in the radial direction, i.e. in many cases, the piston recess is formed. The temperature of the combustion chamber surface or of the base body, in particular in the case of an uncooled piston, decreases radially from the inside to the outside as viewed radially. In the case of the reciprocating piston according to the invention, it is provided that the cooling water is conveyed as directly as possible via the inflow region arranged on the inside to the region of the basic body with the greatest temperature and from there onwards radially to the outside. The cooling liquid is additionally branched off by a large number of micro cooling channels extending radially outward, and the surface to be cooled is guided radially outward in a plurality of individual channels in a penetrating manner, in order to likewise cool the section of the substrate that is located further outward, viewed in the radial direction. Thereby, the coolant flows from the radially inner region toward the radially outer region. The coolant can thus be used optimally for cooling, since the flow direction of the coolant is thereby adapted to the temperature gradient of the basic body during operation of the reciprocating piston internal combustion engine.

The design of the micro-cooling channels with a maximum cross-sectional width of 3mm makes it possible to provide a particularly large surface available for cooling, so that particularly effective cooling of the substrate takes place. Herein, the maximum width passing through the micro cooling channel perpendicular to the main flow direction of the cooling liquid is referred to as a cross-sectional width of the micro cooling channel. The micro cooling channels in particular have a maximum cross-sectional width of 2.5mm and preferably the cooling channel cross-sectional width is at least 1 mm. The cooling channel is in particular of circular configuration in cross section. Alternatively, the cooling channels may also be of polygonal configuration in cross section or have other cross-sectional shapes.

The formation of what are known as "hot spots", that is to say particularly hot regions, can also be effectively suppressed at the base body of the reciprocating piston by the configuration of the micro cooling ducts and the cooling ducts extending from the inside to the outside, in particular by arranging the micro cooling ducts in such a way that, in the case of full load or another defined load state, a temperature distribution over the combustion chamber surface which is as uniform as possible is produced. The risk of pre-ignition can thus also be reduced, especially in the case of gasoline engines.

The cooling of the reciprocating piston according to the invention can be further improved if the cooling channel opens to one outflow opening arranged radially outside or to a plurality of outflow openings arranged radially outside. In this case, the outflow opening or the outflow openings are at least partially oriented in such a way that the coolant leaving through the outflow openings reaches directly or indirectly on the outside of the piston skirt. In this context, a piston skirt is to be understood to mean, in particular, a section of the basic body which, viewed in the axial direction, is arranged at a distance, in particular below the piston bottom and the combustion chamber surface, and which generally has one or more guide surfaces for guiding the reciprocating piston along the cylinder wall. In this way, the coolant reaches the crankcase below the piston skirt only indirectly (i.e., not directly), if at all. The piston skirt is cooled on the outside by the coolant that reaches the piston skirt from the outside. Likewise, the formation of engine oil deposits and slugs (Verkorkung) on the piston skirt due to excessive temperatures can be effectively suppressed in this way. The coolant also improves the lubrication of the piston skirt and reduces its friction against the cylinder wall.

The outflow openings are in particular oriented such that the coolant flows straight through and thus directly from above onto the radial outer side of the piston skirt. Alternatively, the outflow opening can also be oriented such that the coolant first impinges against the cylinder wall and from there rebounds in the direction of the piston skirt. Preferably, the cooling channel or at least one cooling channel extends mainly horizontally in the region directly adjacent to the outflow opening, that is to say approximately at an angle of at most 30 °, preferably at most 20 °, and further preferably at most 10 °, to the horizontal. In this connection, the direction perpendicular to the cylinder axis, along which the piston moves in a reciprocating piston internal combustion engine, is referred to as the horizontal plane.

In a further practical embodiment of the reciprocating piston according to the invention, a gap between the radially outer section of the piston skirt and the radially outer section of the piston bottom is formed at the base body at least over a part of the circumference, and the at least one cooling channel opens into the region of the gap between the piston skirt and the piston bottom. The above-mentioned region refers to a region defined by the piston skirt on one of the sides and by the lower piston bottom on the other side in the axial direction. In the above-described embodiments of the reciprocating piston with a gap between the piston skirt and the piston bottom, thermal decoupling of the piston skirt from the piston bottom is achieved. This embodiment is particularly suitable from a structural point of view for the direct supply of coolant to the piston skirt.

A particularly effective cooling of the piston according to the invention is achieved if at least eight (and preferably at least nine, at least ten or more) radially extending cooling channels are formed in the basic body, since then a relatively tight-meshed distribution network with good face penetration is already produced. In particular, the cooling channels extend from the inflow region to eight, nine, ten or more corresponding outflow openings. It is also possible to configure the cooling channels such that they also branch off one or more times radially outward, for example, first of all from the 10 cooling channels arranged radially inward in the radially inner region radially outward up to the radially intermediate region and then branch off from this intermediate region into two or more further channels. Here, the cross-sectional width can be adapted such that the flow velocity does not vary as much as possible in the region of the branching.

The smaller the maximum cross-sectional width is selected, the thinner the "branches" of the cooling channel network are configured. Conversely, the pressure losses that occur in "branches" or micro-cooling channels increase with decreasing cross-sectional width. For this reason, the maximum cross-sectional width is between 1mm and 4mm, preferably between 1mm and 3mm, according to current knowledge.

It is preferred if the projected area of the cooling channel with respect to the cross-sectional area of the piston is at least 20 percent, preferably at least 25 percent and further preferably at least 30 percent.

In another practical embodiment of the reciprocating piston according to the invention, the inflow region comprises an annular channel or a central Reservoir (Reservoir), and the cooling channel extends from the annular channel or the central Reservoir, viewed radially outward. "annular" in this context preferably means a closed, but only partially annular shape, that is to say also a semi-annular or otherwise arched annular channel structure. By means of such an annular channel, which is preferably of at least semi-circular configuration, a good and more uniform distribution of the cooling liquid into the individual cooling channels is obtained, which makes it possible to achieve a uniform cooling of the piston bottom, viewed in the circumferential direction. By central reservoir is meant a cavity-like structure, for example in the shape of a hollow sphere or other shaped hollow, from the outside of which the micro-cooling channels extend radially outwards.

A structurally particularly simple design results if at least two cooling channel networks which are connected to one another are formed in the base body, not in a flow-conducting manner, or at least only up to the network distribution points arranged radially inside.

In particular, two or more cooling channel networks may be arranged such that the piston bottom is penetrated to the greatest possible extent uniformly by the channels of the cooling channel networks. For example, the first cooling channel network and the second cooling channel network may extend over two halves of the cross-sectional area of the base.

In a particularly practical embodiment, the cooling channel networks are configured as mirror images of one another. The two cooling channel networks which are connected to one another in a fluid-tight manner further preferably have two inflow regions which are separate from one another and can be supplied independently of one another. Such a separate inflow region and the formation of the cooling channel network are particularly advantageous if the formation of the inflow region in the central position in the main body, i.e. in the radial middle of the combustion chamber surface (in the region of the cylinder center axis), is technically and/or structurally not possible or can only be achieved with great effort. This is the case in particular if the injection takes place via a piston nozzle (which will be explained in more detail below), since this piston nozzle cannot be arranged in the middle below the piston base on account of the connecting rod.

In a further practical embodiment, the at least one inflow region can extend from an inflow opening formed in the side of the piston pin bushing. This embodiment of the reciprocating piston according to the invention is particularly suitable for supplying a cooling channel network with a cooling fluid via a connecting rod functionally connected to the reciprocating piston. In particular, it is then provided that two cooling channel networks are formed which are connected to one another in a fluid-tight manner, wherein the inflow openings are formed in the side faces of the piston pin bushing on different side faces of the connecting rod. If the connecting rod is hollow, the coolant can be guided in the connecting rod in the direction of the reciprocating piston. The reciprocating piston and the connecting rod are preferably connected by means of a pin, wherein the pin is in particular designed such that the coolant can be conveyed to the at least one inflow opening via the pin. For this purpose, in particular at least one, in particular funnel-shaped, channel can be formed in the pin such that the coolant can be continuously and sufficiently conveyed in the direction of the piston independently of the pivoting movement between the connecting rod, the pin and the piston.

For this purpose, the at least one inflow opening extends in particular over an angular extent of the periphery of the side face of the piston pin bushing. The angular range corresponds at least to the angular range over which the pin oscillates during movement of the connecting rod relative to the reciprocating piston. The pin is connected to the connecting rod, in particular by means of a press fit, and rotates relative to the reciprocating piston. In particular, the inflow opening extends over at least 20 °, preferably at least 30 °, of the circumference of the side face of the piston pin bushing.

In order to feed the cooling liquid through the connecting rod into the basic body of the reciprocating piston, a pump can optionally be provided in a variant of the reciprocating piston according to the invention, with which a sufficiently high pressure is produced so that at least 20 percent of the cooling channel network can be filled with cooling liquid during operation of the reciprocating piston internal combustion engine. As such a pump, a standard oil pump of a reciprocating piston internal combustion engine can also be provided which is also used for other purposes, but an additional pump for one or more reciprocating pistons according to the invention can also be provided which is used only or mainly for supplying the cooling channel network. It is likewise possible to ensure the supply of the cooling channel network in any other way and manner.

Preferably, at least 25 percent, at least 30 percent, or at least 40 percent, 50 percent, or even 75 percent of the cooling channel network is filled with cooling fluid. The cooling channel network can also be completely filled (that is to say up to 100 percent) with cooling liquid, so that particularly effective cooling results due to the maximum flow of cooling liquid through the cooling channel network. By increasing the pressure and thus the flow rate produced with the pump, the cooling power can then be adapted as desired, provided that the pump is controllable and/or adjustable. If the cooling liquid is introduced into the base body via the connecting rod, the cooling liquid can be actively fed into the base body of the reciprocating piston continuously, at a higher pressure and optionally also flow-controlled or flow-regulated.

Alternatively or in addition to the previously described embodiment, in a further embodiment the inflow region can extend from a region of the lower piston bottom which is spaced apart from the piston pin bushing. Such a region is arranged in particular adjacent to the piston pin bushing and is arranged in particular as centrally as possible-viewed in the radial direction-in the basic body, for example within a radius corresponding at most to half the radius of the piston. In this embodiment, the cooling channel network is realized with the supply of the cooling liquid, in particular via at least one piston nozzle. The piston nozzles are preferably arranged below the bottom of the lower piston in such a way that the cooling liquid can be sprayed upwards into the cooling channel network. In this embodiment, it is also preferred if two or more cooling channel networks which are connected to one another in a fluid-tight manner are formed in the base body. In this case, it is also preferred to provide at least one individual piston nozzle per cooling channel network. The introduction of the cooling fluid into the main body via the piston nozzle can be realized very simply in terms of construction, in particular since the cooling fluid does not have to be guided through elements which are moved relative to one another.

In a further practical embodiment, the contour of the cooling channel is adapted at least partially to the contour of the combustion chamber surface such that the maximum distance of the cooling channel from the combustion chamber surface lies within a predetermined tolerance window (Toleranzfenster). In particular, the contour of the cooling channel is adapted to the combustion chamber surface with the piston recess, so that the cooling channel likewise has a recess-like contour.

Preferably, the axial distance of the cooling channel both to the combustion chamber surface and to the lower piston bottom lies within a predetermined tolerance window. "within a predetermined tolerance window" means here, in particular, that the spacing deviation between the combustion chamber surface and/or the lower piston base is not more than 20 percent, preferably not more than 15 percent and particularly preferably not more than 10 percent. The cooling channel preferably extends substantially horizontally over at least 50 percent, preferably at least 65 percent and in particular at least 80 percent of the diameter of the piston base. This means, in particular, the radially inner region of the piston base. In addition, the cooling channel is preferably adapted at least partially to the contour of the combustion chamber surface, i.e. the distance between the combustion chamber surface and the respective cooling channel is approximately constant over at least a partial region, preferably over the entire radial extent of the cooling channel.

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. The micro cooling channels extend radially outward from the annular channel, wherein the cooling channels have a contour adapted to the contour of the combustion chamber surface with the piston recess. In the radially outer region, the cooling channel first extends approximately in the axial direction in the axial section and then opens horizontally in the horizontal section into the region between the piston bottom and the piston skirt.

The present aspect also relates to the use of a reciprocating piston as described previously in a reciprocating piston internal combustion engine. In this case, the coolant is introduced into the reciprocating piston via an inflow region arranged radially on the inside and is conducted radially outward through a large number of radially extending cooling channels. A particularly effective cooling of the reciprocating piston is brought about by this use, since the coolant first cools a particularly hot, radially central region of the combustion chamber surface and flows from there outwards to the cooler edge region.

As already mentioned above, the cooling liquid is preferably introduced such that at least one cooling channel network is filled with cooling liquid by at least 20 percent. Preferably, the cooling channel network is filled with cooling liquid by at least 30 percent or at least 40 percent, 50 percent or even at least 75 percent and particularly preferably by 100 percent. That is, the cooling fluid is introduced into the substrate at a sufficiently high pressure and/or a sufficiently high velocity to facilitate complete transport of the cooling fluid through the micro-cooling channels. Overall, efficient cooling independent of the stirring action is thus obtained.

Drawings

Further practical embodiments of the invention are described below in connection with the figures. Wherein:

Figure 1 shows a first embodiment of a reciprocating piston according to the invention in a side view,

figure 2 shows the reciprocating piston of figure 1 in a top view,

figure 3 shows half of the reciprocating piston of figures 1 and 2 in a perspective view from obliquely above,

fig. 4 shows the reciprocating piston of fig. 1 to 3, wherein the piston skirt is shown in longitudinal section according to the line IV-IV of fig. 2, and the area designated B in fig. 4 is partially cut away,

figure 5 shows the reciprocating piston of figures 1 to 4 in a longitudinal section according to line V-V of figure 3,

figure 6 shows the cooling channel network in perspective view shown in isolation,

figure 7 shows the reciprocating piston of figures 1 to 5 with connecting rods and pins in a longitudinal section similar to line VII-VII of figure 2,

figure 8 shows a further embodiment with the cooling channel network of figure 6 and with a piston nozzle in a schematic view,

FIG. 9 shows a further embodiment of a reciprocating piston according to the invention in a perspective view from obliquely above, an

FIG. 10 shows the reciprocating piston of FIG. 9 from an oblique upper perspective view without the piston bottom.

Detailed Description

A first embodiment of a reciprocating piston 10 according to the invention is explained in connection with fig. 1 to 7. The reciprocating piston 10 is used in a known arrangement in a reciprocating piston internal combustion engine, not shown. In such a reciprocating piston internal combustion engine, the reciprocating piston 10, viewed in the axial direction, moves up and down in the combustion chamber along the double arrow shown in fig. 1, in order to vary the volume of the combustion chamber separated by the reciprocating piston and thus in particular to make possible a compression phase and a decompression phase.

The reciprocating piston 10 includes a base 12 with a piston bottom 14. The surface pointing towards the combustion chamber is referred to below as the combustion chamber surface 16 and may also be referred to as the upper piston bottom. In the embodiment shown, the combustion chamber surface 16 comprises a radially centrally arranged piston recess 18. The side of the piston bottom 14 facing away from the combustion chamber is subsequently referred to as the lower piston bottom 20.

Furthermore, the main body 12 comprises a piston skirt 22, which is arranged, as viewed in the axial direction, below the piston bottom 14. The piston skirt 22 is now connected to the piston bottom 14 via a piston pin bushing 24. The piston pin bushing 24 serves to swingably connect the reciprocating piston 10 with a connecting rod 26 by means of a pin 28 (see fig. 7). In the radially outer region, an axially extending gap 30 (see fig. 1 and 4) is formed between the lower piston bottom 20 and the piston skirt 22, so that the piston skirt 22 is thermally decoupled to the greatest possible extent from the piston bottom 14. The gap 30 extends over the entire region between the upper piston bottom 20 and the piston skirt 22.

As can be clearly seen in fig. 2, two cooling channel networks 32 which are connected to one another in a fluid-tight manner are formed in the base body 12 of the reciprocating piston 10, wherein the cooling channel networks 32 extend in each case over half of the piston base 14.

The cooling channel network 32 accordingly comprises-viewed in the radial direction-an inflow region 34 arranged on the inside. The inflow region 34 is formed, as can be seen in fig. 4 and 6, by an inflow opening 36 and a connecting channel 38 extending axially upward from the inflow opening 36 and a substantially horizontally extending annular channel 40. A plurality of micro cooling channels 42 extend radially outward from the annular channel 40. Each cooling channel network 32 is currently constructed with ten radially extending micro cooling channels 42 (see fig. 2 and 3). The cross-sectional width of the micro cooling channels 42 is 2.5mm in the illustrated embodiment.

As can be clearly seen in fig. 1 and 5, the cooling channel 42 extends to an outflow opening 44 arranged radially on the outside. The outflow opening 44 is arranged, as viewed in the axial direction, in the region of the gap 30 between the piston skirt 22 and the lower piston bottom 20, i.e. the cooling channel 42 opens into the region of the gap 30 between the lower piston bottom 20 and the piston skirt 22. The coolant flowing through the cooling channel 42 is thereby guided such that it passes through the outflow opening 44 directly onto the outer side of the piston skirt 22.

The respective geometry and the respective direction of the individual cooling channels 42 can be clearly seen in particular in fig. 5 and 6. Starting from the annular channel 40, the cooling channel 42 first extends horizontally to the greatest extent. The cooling channel 42 is contoured to the combustion chamber surface 16 with the piston recess 18. In particular, the distance between the cooling duct 42 and the combustion chamber face 16 with the piston recess 18 is constant in the radially inner region (in which the cooling duct 42 extends radially outward), since the cooling duct 24 extends radially outward and upward with the same low curvature as the combustion chamber face 16.

In this embodiment, the distance of the cooling duct 42 from the lower piston bottom 20 is also constant in its radially inner region extending parallel to the combustion chamber face 16.

In the embodiment shown, the cooling duct 42 extends, as viewed in the radial direction, over approximately 80 percent of the radially extending width (i.e., diameter) of the combustion chamber 16. If one only observes a region in which the cooling channel 42 extends approximately parallel to the combustion chamber face 16 in a predominantly radial direction, the cooling channel 42 extends in the radial direction over approximately 60 percent of the width of the combustion chamber face 16.

In the region of the coupling to the predominantly radially outwardly directed section of the cooling channel 42, the cooling channel 42 is predominantly axially directed in an axial section 46, before it transitions into a further horizontal section 48 above the piston skirt 22 and is here respectively open on the outside to the outflow opening 44.

As is apparent from fig. 4 and 6, the inflow opening 36 is correspondingly funnel-shaped and extends over an angular range of the circumference of the side 54 of the piston pin bushing 24, which angular range allows a continuous inflow even if the connecting rod 26 is swung relative to the reciprocating piston 12. The inflow openings 36 of the two cooling channel networks 32 are formed in the side 54 on the respective different sides of the connecting rod 26 connected to the reciprocating piston 10 (see fig. 2 and 7 for an overview).

In fig. 7 the arrangement of the reciprocating piston 10 according to the invention with the connecting rod 26 and the pin 28 connecting the connecting rod 26 and the reciprocating piston 10 is shown. The pin 28 is designed here as a hollow cylindrical component with a support mandrel (Stuetzdorn) which can be regarded as a partial element of the pin and therefore no separate reference numeral is obtained. The connecting rod 26 is in the present case of hollow design, so that the coolant can be conducted or can be actively pumped through the interior of the connecting rod 26. The pin 28 has two channels 50 extending at least partially in the axial direction, which open into the inflow openings 36 to the respective cooling channel network 32. In the event of the connecting rod 26 and the pin 28 swinging relative to the reciprocating piston 10 (now swinging into and out of the plane of the paper), the pin 28 rotates through approximately 30 ° relative to the piston pin bushing 24. The inflow openings 36 likewise extend over this angular range, so that an inflow of coolant from the connecting rod 26 via the pins 28 into the respective cooling channel network 32 is possible over the entire range of motion.

Overall, a flow of the cooling fluid from the radially inner region through the inflow region 34 and the cooling channel 42 radially outward along the arrow S is achieved. It is therefore conceivable that the combustion chamber surface 16 generally has a higher temperature in the middle than in the radially further outer region.

Fig. 8 shows a further embodiment of a reciprocating piston according to the invention. For the description of this embodiment and further embodiments, the same reference numbers are used next for identical or at least functionally identical elements as for the description of the first embodiment. In the following, essentially only differences from the described embodiments will be discussed.

As shown in fig. 8, cooling fluid can also be introduced into the main body 12 by means of the piston nozzle 52. The piston nozzles 52 are arranged at a distance from the respective inflow opening 36 such that the cooling liquid is guided as a jet in the direction of the inflow opening. The coolant accordingly exits from the piston nozzle 52 in such a way that it is at least partially, as large as possible, or even completely, fed into the inflow opening 36. In the case of this embodiment with the piston nozzle 52, the cooling channel network 32 can be arranged so as to be rotated by 90 ° about the cylinder axis relative to the cooling channel network 32 shown in fig. 2, so that the injection takes place further outward, viewed in the radial direction, below the lower piston bottom 20 and spaced apart from the piston pin bushing 24. In this case, it is conceivable that the injection takes place at a distance from the center of the combustion chamber surface 16. If necessary, the geometry of the cooling channel network 32 can be adapted such that the cooling liquid is initially conveyed from the inflow opening 36, which is located slightly further outward in the radial direction, into the central region of the combustion chamber face 16 and from there-after, if necessary, further conveyance in the direction of the combustion chamber face 16-flows radially outward via the cooling channel 42.

Fig. 9 to 10 show a further embodiment of a reciprocating piston 10. This embodiment of the reciprocating piston 10 differs from the first embodiment in particular in that the piston skirt 22 is connected on the outside to the lower piston bottom 20. The gap 30 between the lower piston bottom 20 and the piston skirt 22 is therefore not formed. The outflow opening 44 is designed such that it leads through the piston skirt 22, so that the coolant can reach the outside of the piston skirt 22.

The features of the invention disclosed in the present description, in the drawings and in the claims can be essential both individually and in any combination for the realization of the invention in its various embodiments. The invention may vary within the scope of the claims and taking into account the knowledge of the person skilled in the art in charge.

List of reference numerals:

10 reciprocating piston

12 base body

14 piston bottom

16 combustion chamber surface

18 piston bowl

Bottom of 20 lower piston

22 piston skirt

24 piston pin bushing

26 connecting rod

28 pin

30 gap

32 cooling channel network

34 inflow region

36 inflow opening

38 connecting channel

40 annular channel

42 micro cooling channel

44 outflow opening

46 axial segment

48 horizontal section

50 channel

52 piston nozzle

54 side surface.