Pistons for an internal combustion engine as well as internal combustion engine

Abstract

Piston (10) for an internal combustion engine (100), comprising: - a piston housing (1) which forms a radially inner combustion chamber (A0) and into which a radially outer cooling channel (5) surrounding the combustion chamber (A0) is enclosed for guiding a cooling fluid (KF), - a radially outer first cooling fin (8) which extends with a first axial length (LA1) from an inner surface of a piston crown (3) facing the cooling channel (5) into the cooling channel (5) and at least partially in circumferential direction (U) through the cooling channel (5), - a radially inner second cooling fin (9) which extends with a second axial length (LA2) from the inner surface of the piston crown (3) facing the cooling channel (5) into the cooling channel (5) and at least partially in the circumferential direction (U) through the cooling channel (5), - a number of separation sections (6B) which separate the piston housing (1) into an upper housing part (1A) and a lower housing part (1B), wherein the separation sections (6B) are arranged at a minimum distance (a) from the inner surface of the piston crown (3) facing the cooling channel (5), which is greater than the axial length (LA1, LA2) of at least the cooling fin (8, 9) arranged adjacent to the respective separation section (6B), preferably greater than the axial length (LA1, LA2) of both cooling fins (8, 9), wherein the second cooling fin (9) runs adjacent to a bowl-side wall (6) of the piston housing (1) and separates a radially inner cooling channel (5c).

Description

[0001] The invention relates to a piston for an internal combustion engine and to an internal combustion engine with such a piston.

[0002] A piston of the type mentioned above typically has a piston housing that forms a radially inner combustion chamber and into which a radially outer cooling channel, surrounding the combustion chamber completely, is integrated for conveying a cooling fluid. The combustion chamber is generally formed by a so-called combustion bowl. The combustion reaction of the internal combustion engine takes place in this combustion chamber. The efficiency of the combustion reaction depends, among other things, on how the injected fuel mixes and distributes with the air in the combustion chamber, as well as on the compression ratio of the supplied air. The aim is always to ensure efficient and complete combustion.

[0003] Various piston geometries with a combustion chamber-forming bowl have become established. For example, pistons with a so-called stepped bowl are known, characterized by a stepped recess on the piston crown. In contrast to other piston geometries with a simple, round combustion chamber bowl, stepped bowl pistons have a more complex geometry that often extends over several levels or steps. This special design is intended to optimize air turbulence and fuel injection in the piston during air compression and the combustion reaction. The optimized air movement ensures a more homogeneous mixing of air and fuel. Other more complex piston geometries include so-called W-shaped and W-torus bowl pistons, which offer similar advantages during air compression and the combustion reaction.

[0004] Due to the high thermal loads in the area of ​​the piston resulting from the combustion reaction, it has a cooling channel through which cooling fluid flows in order to optimize its service life and the engine performance of a corresponding internal combustion engine with such pistons.

[0005] The primary function of the cooling channel is to efficiently dissipate excess heat generated during combustion in the combustion chamber near the piston crown. The piston's oscillating motion during operation intensively circulates and moves the cooling fluid within the channel, maximizing heat transfer from the piston housing to the cooling fluid. This cooling is essential to reduce localized overheating, which can lead to material fatigue, cracking, or piston seizure.

[0006] Pistons of this type for internal combustion engines with a radially inner combustion chamber and a cooling channel surrounding this combustion chamber are known in the prior art. To increase the cooling performance of such pistons, efforts are being made to optimize the geometry of the cooling channel, as shown, for example, in DE 10 2021 210 626 A1. This document shows a subdivision extending axially from the piston crown into the cooling channel, which runs circumferentially through the cooling channel. The subdivision extends along at least 20% to 75% of the axial extent of the cooling channel and, together with a projection on an outer wall of the cooling channel beyond which the subdivision extends, forms a partitioned cavity. The narrowed access to this cavity is intended to retain the coolant for a particularly long time.Other concepts, as shown in US 10,247,133 B2, provide for a large number of cooling fins extending completely through the cooling channel to increase the surface area and optimize heat exchange between the cooling fluid and the piston housing.

[0007] While cooling channels known from the prior art do, in principle, allow for cooling of the piston housing, they only provide insufficient cooling of the areas subjected to particularly high thermal stress. During operation, the highest temperature typically occurs in the center of the piston crown in the area of ​​the combustion chamber bowl, stepped bowl, or W- or W-torus bowl. As the efficiency of the combustion reaction increases, the thermal stress in this area continues to rise, and insufficient cooling leads to local overheating, which causes material fatigue, cracking, or piston seizure, thus reducing the service life of the pistons and the internal combustion engine.

[0008] This is where the invention comes in, the object of which is to overcome at least one of the disadvantages known from the prior art. In particular, the object of the present invention is to increase the service life of pistons of the aforementioned type as well as of internal combustion engines equipped with such pistons.

[0009] The invention solves this problem in a first aspect by means of a piston according to claim 1.

[0010] The invention proposes a piston for an internal combustion engine, comprising a piston housing that forms a radially inner combustion chamber and into which a radially outer cooling channel, surrounding the combustion chamber, is enclosed for guiding a cooling fluid. The piston further comprises a radially outer first cooling fin, extending with a first axial length from an inner surface of the piston crown facing the cooling channel into the cooling channel and running at least partially circumferentially through the cooling channel, and a radially inner second cooling fin, extending with a second axial length from the inner surface of the piston crown facing the cooling channel and running at least partially circumferentially through the cooling channel.The piston further comprises a number of separation sections that divide the piston housing into an upper housing part and a lower housing part. These separation sections are arranged at a minimum distance from the inner surface of the piston crown facing the cooling channel, a distance which is greater than the axial length of at least the cooling fin adjacent to the respective separation section. Preferably, the minimum distance is greater than the axial length of each of the two cooling fins. The second cooling fin extends adjacent to a bowl-side wall of the piston housing and separates a radially inner cooling channel. In other words, in addition to the first radially outer cooling fin, the piston includes a second cooling fin offset radially inwards. The second cooling fin extends from the inner surface of the piston crown facing the cooling channel, adjacent to a bowl-side wall of the cooling channel, and forms a cooling channel.The cooling fins are integrally formed with the piston crown and terminate with a free end within the cooling channel. It should be understood that the bowl-side wall can simultaneously form a bottom section of the cooling channel, so that the cooling fin extends into the cooling channel from a bottom section formed by the bowl-side wall.

[0011] An adjacent arrangement means that no further cooling fin or other component projecting into the cooling channel is located between the cooling fin and the respective separation section or wall. An adjacent arrangement, therefore, refers to an arrangement of two components directly next to each other, without them necessarily being in direct contact.

[0012] Within the scope of the present invention, separation sections are understood to be connection or joining sections, in particular also joining seams, of the two housing parts, which separate the piston housing into the upper housing part and the lower housing part in such a way that it is recognizable that the piston housing comprises an upper housing part and a lower housing part. Depending on the joining method, the separation sections formed by connection or joining sections, in particular also joining seams, may also include a weld bead or a brazed seam. Such a weld bead then, for example, creates a projection that extends into the cooling channel adjacent to the actual separation section – i.e., in the case of a weld seam.

[0013] The bowl-side wall of the cooling channel runs adjacent to the part of the piston housing that forms the combustion bowl, stepped bowl, or W- or W-torus bowl. This means that the additional second cooling fin is located near the area of ​​the piston housing that is subject to the highest thermal stress. The fluid deflection area of ​​the second cooling fin directs cooling fluid specifically towards this bowl-side wall. For this purpose, the second cooling fin forms a fluid inflow aid that, at a specific position and / or movement of the piston, facilitates the flow of cooling fluid into the cooling channel inflow area.

[0014] Furthermore, the axial length of the two cooling fins, in relation to the arrangement of any separating sections on adjacent walls, ensures that the cooling fluid directed into the radially inner cooling channel is not obstructed or deflected by separating sections and any resulting protrusions or the like. In other words, a narrowing of the cooling channel in the immediate vicinity between the separating section and the respective cooling fin is prevented. Thus, according to the invention, it is taken into account that the two-part piston of the type mentioned above has manufacturing-related separating sections that, due to the manufacturing process, result in protrusions or other features that can influence the fluid flow. This is particularly crucial in the area of ​​the bowl-side wall, since this area is exposed to particularly high thermal loads due to the bowl.

[0015] The two cooling fins ensure a uniform distribution of the cooling fluid within the cooling channel, thus guaranteeing sufficient cooling even in the radially outer area. Furthermore, the increased surface area provided by the two cooling fins is advantageous, as it improves heat conduction between the piston housing and the cooling fluid.

[0016] Advantageous further developments of the invention can be found in the dependent claims and specify in detail advantageous possibilities for realizing the concept explained above within the scope of the task and with regard to further advantages.

[0017] According to a preferred embodiment, the radially inner cooling channel has a fluid deflection area for directing the cooling fluid towards the trough-side wall. In particular, a cooling channel inlet area is formed between the second cooling fin and the trough-side wall, through which the cooling fluid enters the radially inner cooling channel. Furthermore, the second cooling fin has a fluid inlet aid which—particularly in the cooling channel inlet area—is arranged and designed to facilitate the flow of the cooling fluid into the radially inner cooling channel and towards the fluid deflection area.Forming a radially inner cooling channel through the second cooling fin with a cooling channel inlet area, combined with a fluid inlet aid and positioning the cooling channel inlet area at a distance from any flow-influencing features in the area of ​​the inner wall's separation section, maximizes the proportion of fluid flow directed into the cooling channel and, via its fluid deflection area, onto the trough-side wall. This ensures sufficient cooling, particularly in this area, thereby preventing local overheating and resulting damage.

[0018] Within the scope of the present invention, the cooling channel inflow area is considered to be, in particular, the area which extends from a distal end section of the second cooling fin to the opposite trough-side wall.

[0019] Within the scope of the present invention, a fluid deflection zone is understood to be a region that influences the flow of the cooling fluid in such a way that the flow lines of the cooling fluid are deflected. The fluid deflection zone is arranged and oriented towards the wall facing the bowl such that at least a predominant proportion of the cooling fluid introduced into the radially inner cooling channel by means of the fluid inlet aid exhibits flow lines that converge steeply towards the fluid deflection zone. In this context, this means that the flow lines converge at an angle of 90° ± 45° towards the fluid deflection zone. As a result, this portion of the flow impacts the fluid deflection zone and, due to its orientation towards the wall facing the bowl, rebounds in the direction of that wall, thereby generating more turbulent flow.

[0020] This increases the proportion of the flow directed onto the trough-side wall, compared to split cooling channels with two cooling fins without a fluid deflection area, by means of the fluid deflection area.

[0021] The fluid inlet aid constitutes a functional area of ​​the second cooling fin, which also includes its distal end section. This area directs increased fluid flow into the cooling section channel and thus to the fluid deflection area. The fluid inlet aid projects into the cooling section channel in such a way that—compared to the adjacent cooling section channel—a larger portion of the cooling fluid flow lines are directed into the cooling section channel inlet area. To achieve this effect, various exemplary embodiments of the structural design of the fluid inlet aid are described below within the scope of the invention.

[0022] According to a preferred embodiment, the fluid inlet aid comprises a distal end section projecting into the cooling channel relative to the first cooling fin. This distal end section is thus associated with the second cooling fin. In other words, the axial length of the second cooling fin is greater than the axial length of the first cooling fin, so that the distal end section of the second cooling fin projects axially and forms the fluid inlet aid. The fluid inlet aid transitions into the fluid deflection area of ​​the radially inner cooling fin, which is also formed by the radially inner cooling fin. The distally projecting end section provides an increased surface area adjacent to the inner wall and thus improved heat dissipation from the thermally stressed area near the recess.Furthermore, the axially projecting distal end section acts as a fluid inflow aid and, due to its increased surface area, can direct more cooling fluid into the radially inner cooling channel. This fluid is then guided towards the wall on the trough side by the fluid deflection area. Additionally, the cross-sectional narrowing in the cooling channel inflow area caused by the distal end section creates turbulence and eddies, further improving the cooling effect. The asymmetry in the length of the cooling fins resulting from the projecting distal end section provides an overall increase in surface area as required and minimizes the weight increase caused by the relatively shorter first cooling fin.

[0023] Preferably, the distal end section, extending from the inner surface of the piston crown facing the cooling channel, projects at least 70%, and in particular at least 80%, further into the cooling channel than a distal end of the first cooling fin. This provides a sufficiently large surface area adjacent to the thermally stressed inner wall of the piston housing. The radially outer first cooling fin is, however, sufficiently large to direct a sufficient quantity of cooling fluid to the less thermally stressed area of ​​the outer wall as well. The resulting significant asymmetry of the two cooling fins with respect to their length thus optimizes the distribution of the surface area cooled by the cooling fluid as required, thereby optimizing the weight of the piston housing.

[0024] According to a further preferred embodiment, the fluid inlet aid comprises a radially inwardly facing surface of the second cooling fin, which extends at least partially towards the bowl-side wall. In particular, at least a section of this inwardly facing surface forms the fluid deflection zone, at least partially. In other words, a radially inner surface of the second cooling fin extends towards the inner wall of the piston housing. This orientation creates a cross-sectional narrowing between the distal end of the second cooling fin and the bowl-side wall, which leads to an acceleration of the cooling fluid and thus to turbulence. This improves the heat transfer between the bowl-side wall of the piston housing and the cooling fluid. Preferably, the radially inwardly facing surface of the second cooling fin is inclined relative to an axial direction of the piston.Particularly preferred is the radially inwardly facing surface inclined at an angle of 2° to 5°, especially 3° to 4°. Such a shallow inclination ensures sufficient acceleration of the cooling fluid without impeding its flow into a radially inner part of the cooling channel adjacent to the trough-side wall.

[0025] Alternatively or additionally, the radially inward-facing surface of the second cooling fin is concave. Preferably, the concave radially inward-facing surface has a radius of curvature in the range of 50 mm to 70 mm, particularly 55 mm to 65 mm, and most preferably 57.5 mm to 62.5 mm. The concave design deflects the cooling fluid towards the inner wall of the cooling channel. Furthermore, the concave design, particularly in the range of the proposed radii of curvature, promotes a slight reduction in cross-sectional area at the inlet of a section of the cooling channel formed between the second cooling fin and the inner wall, thus accelerating the inflowing cooling fluid.At the same time, however, it is ensured that sufficient cooling fluid can flow into this area so that a sufficient amount of accelerated cooling fluid hits the inner wall and thus this thermally stressed area is cooled to a special degree.

[0026] According to a preferred embodiment, the first and second cooling fins are asymmetrically designed. This asymmetrical design accommodates the different thermal loads on the radially inner and outer walls. The second cooling fin is located on the wall facing the bowl, and the first cooling fin is located on the radially outer wall. The design of the cooling fins is essential for heat dissipation from the respective wall of the cooling channel. This asymmetry allows for the consideration that the radially outer wall is generally subject to lower thermal loads than the wall facing the bowl.

[0027] The asymmetrically designed cooling fins differ primarily in their axial length. In particular, the second cooling fin is longer in the axial direction, and the axially projecting distal end section of the second cooling fin forms the fluid inflow aid.

[0028] Alternatively or additionally, the cooling fins differ in the angle of inclination of a radially inward-facing surface of each cooling fin relative to the axial direction of the piston. Preferably, at least the radially inward-facing surface of the second cooling fin is inclined relative to the axial direction and forms the fluid inflow aid and, preferably, at least partially, the fluid deflection zone through which cooling fluid is directed towards the inner wall. In contrast, the first cooling fin can have an opposite inclination, no inclination at all, or a smaller angle of inclination. An opposite inclination allows for increased flow of cooling fluid towards the outer wall. The absence of an inclination, however, means that the first cooling fin primarily provides an increase in surface area and hardly influences the flow direction of the cooling fluid.An inclination towards the inner wall - possibly at an angle different from the inclination angle of the second cooling fin - avoids excessive cross-sectional expansion at the entrance of an inner cooling channel bordered by the two cooling fins, which would otherwise potentially slow down the cooling fluid.

[0029] Alternatively or additionally, the cooling fins differ in the radius of curvature of one or more of the radially inward-facing surfaces of each cooling fin compared to the axial direction. Preferably, at least the radially inward-facing surface of the second cooling fin is concave with a specific radius of curvature, forming the fluid inflow aid and, preferably, at least partially, the fluid deflection zone through which cooling fluid is directed towards the wall facing the recess. In contrast, the first cooling fin can have a counter-curvature, no curvature at all, or a smaller radius of curvature. A counter-curvature allows for increased flow of cooling fluid towards the outer wall. The absence of curvature, however, primarily results in the first cooling fin providing an increased surface area.A curvature in the direction of the inner wall - possibly with a radius of curvature that differs from the radius of curvature of the second cooling fin - avoids an excessive widening of the cross-sectional area at the entrance of an inner cooling channel bordered by the two cooling fins, which would otherwise potentially slow down the cooling fluid.

[0030] Alternatively or additionally, the two cooling fins differ in their proximal width at the piston crown and / or their distal width. A reduced distal width facilitates the flow of coolant into the cooling channel partitioned by the respective cooling fin, i.e., the separated portion of the cooling channel. A greater proximal width facilitates manufacturing and heat conduction between the cooling fin and the piston crown.

[0031] Overall, the asymmetry with respect to the above characteristics takes into account the locally different thermal loads on the piston.

[0032] According to a further preferred embodiment, at least the second cooling fin is wedge-shaped, particularly with an angle of 2° to 4°, and especially preferably 2.75° to 3.75°, relative to the axial direction of the piston. This ensures improved heat transfer between the piston crown and the second cooling fin by means of a wider proximal section. A reduced width of the wedge-shaped cooling fin in the region of the distal end section further facilitates the flow of cooling fluid. The first cooling fin is also particularly preferably wedge-shaped, particularly preferably with an angle of 2° to 4°, and especially preferably 2.75° to 3.75°, relative to the axial direction of the piston.

[0033] According to a further preferred embodiment, the second cooling fin is arranged within the radially inner half of the cooling channel with respect to its radial extent. This ensures sufficient proximity of the second cooling fin, and thus of the fluid inlet aid and the adjoining fluid deflection area, to the bowl-side wall of the piston housing. This allows sufficient cooling fluid to be directed towards the inner wall by the fluid inlet aid and the fluid deflection area, ensuring adequate cooling of this thermally stressed area.Preferably, the first and second cooling fins are arranged uniformly relative to each other and to at least a section of the adjacent piston housing wall in the radial direction, so that the cooling channel is divided into three cooling channels, which have a uniform channel width in the radial direction, at least in some sections. This ensures a uniform distribution of the cooling fluid to the three cooling channels, while the fluid inlet aid of the second cooling fin further ensures that more cooling fluid is directed towards the inner wall. This ensures sufficient cooling of the piston housing overall, and especially in the thermally highly stressed radial inner region near the piston crown.

[0034] According to a further preferred embodiment, the piston crown and the first and second cooling fins extending from the piston crown are part of an upper housing section of the piston housing. Advantageously, the upper housing section is designed as a single piece. In particular, the upper housing section is manufactured very simply by a machining process, especially a grooving and turning process.

[0035] The piston is preferably made of steel. More preferably, it is a stepped-dish piston, i.e., a piston in which the combustion chamber is formed by a stepped dish. Even more preferably, the pistons are so-called W- or W-torus-dish pistons. A W-dish piston is a piston with a W-shaped recess in the piston crown, which forms the combustion chamber and precisely directs the air-fuel mixture. A W-torus-dish piston is a further development of the W-dish piston, in which the dish is arranged in a ring-shaped (torus-shaped) form around a central protrusion.

[0036] The invention solves the aforementioned problem in a second aspect by means of an internal combustion engine with a piston according to the first aspect of the invention, wherein the piston forms a combustion chamber for a combustion reaction of the internal combustion engine. By means of a piston according to the first aspect of the invention, the internal combustion engine according to the second aspect of the invention benefits from the advantages mentioned above. Advantages and preferred embodiments described with regard to the first aspect of the invention are therefore also advantages and preferred embodiments of the internal combustion engine according to the second aspect of the invention.

[0037] Embodiments of the invention are now described below with reference to the drawings and comparison with the prior art, some of which is also shown. These drawings are not necessarily to scale; rather, where explanatory, they are presented in a schematic and / or slightly distorted form. For further details regarding the teachings directly apparent from the drawings, reference is made to the relevant prior art. It should be noted that numerous modifications and changes concerning the form and details of an embodiment can be made without deviating from the general idea of ​​the invention. The features of the invention disclosed in the description, the drawings, and the claims can be essential for the further development of the invention, both individually and in any combination.Furthermore, the invention encompasses all combinations of at least two of the features disclosed in the description, the drawings, and / or the claims. The general idea of ​​the invention is not limited to the exact shape or detail of the preferred embodiments shown and described below, nor is it limited to an object that would be restricted compared to the object claimed in the claims. Where specified dimensioning ranges are given, values ​​lying within the stated limits are also disclosed as limit values ​​and may be used and claimed as desired.

[0038] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings; these show in: Fig. 1. A schematic representation of a section of an internal combustion engine with one piston; Fig. 2 a section of a piston for an internal combustion engine with a recess forming the combustion chamber in a first variant according to a first embodiment; Fig. 3 a section of a piston for an internal combustion engine with a recess forming the combustion chamber in a first variant according to a second embodiment; and Fig. 4 a section of a piston for an internal combustion engine with a recess forming the combustion chamber in a second variant according to a third embodiment; Fig. 5 a section of a piston for an internal combustion engine with a recess forming the combustion chamber in a first variant according to a fourth embodiment; Fig. 6 a section of a piston for an internal combustion engine with the combustion chamber forming recess in a second variant according to a fifth embodiment.

[0039] Fig. Figure 1 schematically shows a section of an internal combustion engine 100. The internal combustion engine 100 comprises a piston 10 with a piston housing 1, which forms a radially internal combustion chamber A0. The piston housing 1 includes an upper housing part 1A with a piston crown 3. The piston 10 has a combustion chamber bowl formed by the upper housing part 1A, which forms the bowl-shaped combustion chamber A0. The bowl is formed by a curved surface and has a curvature change region 7A, in which this surface undergoes a change in curvature and which, in stepped-bowl pistons, is referred to as a radiation splitter. Particularly high thermal loads occur in the immediate vicinity of this curvature change region 7A for the piston housing 1. Exemplary designs of the piston 10 as a stepped-bowl piston with a stepped bowl are shown in Fig. 2, Fig. 3 and Fig. 5 shown and designs of the piston 10 with a shallower bowl geometry are in Fig. 4 and Fig. 6 shown.

[0040] A radially outer cooling channel 5, surrounding the combustion chamber A0, is integrated into the piston housing 1 and is designed to guide a cooling fluid KF. The cooling channel 5 is bounded on the combustion chamber A0 side by a bowl-side wall 6, which here is formed by a radially inner wall 6 of the piston housing 1. The bowl-side wall 6 is preferably shaped to correspond to the bowl-shaped combustion chamber A0.

[0041] The housing parts 1A, 1B of the piston housing 1 are connected along a dividing line T by a separation section 6B. The separation section 6B can, for example, be formed by a weld seam, such that a number of projections extend from the bowl-side wall 6 into the cooling channel 5 adjacent to the actual separation section 6B. Only a single circumferentially extending projection 6A is shown here. Alternatively, the housing parts 1A, 1B of the piston housing 1 can also be joined by other means, for example, by soldering.

[0042] The piston 10 further comprises a radially outer first cooling fin 8 and a radially inner second cooling fin 9, which extend from the piston crown 3, specifically from an inner surface of the piston crown 3 facing the cooling channel 5, into the cooling channel 5. The cooling fins 8 and 9 are spaced apart from each other. The first cooling fin 8 has a first axial length LA1, and the second cooling fin 9 has a second axial length LA2. In this case, the cooling fins 8 and 9 are of equal length.

[0043] The separating section 6B is arranged at a minimum distance a from the piston crown 3. The minimum distance a is greater than the second axial length LA2 of the adjacent second cooling fin 9. In this case, the minimum distance a is also greater than the first axial length LA1 of the first cooling fin 8. Both cooling fins 8, 9 thus terminate before the separating section 6B or the projection 6A on the bowl-side wall 6.

[0044] The second cooling fin 9 has a cooling channel inlet area KE into a radially inner cooling channel 5c, which is formed between a preferably provided fluid inlet aid 90 and the bowl-side wall 6. A fluid deflection area 90A, preferably designed as a flow obstruction, is preferably connected to the optional fluid inlet aid 90 and is arranged and designed adjacent to the bowl-side wall 6 of the piston housing 1 in such a way as to direct the cooling fluid KF towards the bowl-side wall 6.

[0045] As in Fig. As schematically indicated in Figure 1, the fluid inlet aid 90 is specifically arranged and designed to direct and accelerate the cooling fluid KF into the cooling section inlet area KE by dividing the cooling channel 5. The fluid deflection area 90A generates turbulence in the area of ​​the thermally highly stressed trough-side wall 6 due to the impacting flow and directs the fluid onto the trough-side wall 6.

[0046] Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. Figure 6 shows various embodiments of the piston 10, which is designed as a stepped bowl piston with a stepped bowl that has a radiation splitter 7 at its base, thus forming the bowl-shaped combustion chamber A0. The in Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. The embodiments shown in Figure 6 differ in particular in the design of the cooling fins 8, 9 and the design of the piston crown 3 and the combustion chamber A0. For the sake of clarity, the same reference numerals are used in the following description for identical or analogous features or features with the same or analogous function. Furthermore, the following description focuses primarily on those features of the embodiments that differentiate them from one another.

[0047] The piston 10 according to Fig. 2 includes in the from Fig. 1. A piston housing 1, which forms a radially inner combustion chamber A0, is known. The combustion chamber A0 is trough-shaped, and a jet splitter 7 extends into the trough-shaped combustion chamber A0.

[0048] The piston housing 1 comprises an upper housing part 1A and a lower housing part 1B, with a piston crown 3 being assigned to the upper housing part 1A.

[0049] A radially outer cooling channel 5, surrounding the combustion chamber A0, is integrated into the piston housing 1 for the purpose of conveying a cooling fluid KF. The cooling channel 5 is bounded by the bowl-side wall 6 and a radially outer wall 16 of the piston housing 1. Furthermore, the piston housing 1 forms a number of annular grooves A1, A2, A3, which extend annularly along an outer surface of the piston housing 1 in the region of the cooling channel 5. The annular grooves A1, A2, A3 primarily serve to accommodate piston rings.

[0050] The upper housing part 1A and the lower housing part 1B are connected to form the piston housing 1. It should be understood that the arrangement of the housing parts 1A and 1B as upper and lower housing parts is not fixed, and a different orientation is also possible. In this case, the housing parts 1A and 1B are connected by a weld. Alternatively, a soldered joint, for example, is also possible. In any case, the upper housing part 1A and the lower housing part 1B each form a separation section 6B at their correspondingly adapted connecting surfaces. After the two housing parts are joined to form the piston housing 1, this separation section divides the piston housing 1 into the upper housing part 1A and the lower housing part 1B, such that it is evident that the piston housing comprises an upper housing part 1A and a lower housing part 1B.Adjacent to the connection points between the upper housing part 1A and the lower housing part 1B, weld beads 2 are formed. A radially inner weld bead 2 in the region of the bowl-side wall 6 forms a radially inner projection 6A, which extends from the bowl-side wall 6 into the cooling channel 5. A radially outer weld bead 2 in the region of the radially outer wall 16 further forms a radially outer projection 16A, which extends from the radially outer wall 16 into the cooling channel 5. The separation section 6B and preferably also the projections 6A, 16A are each arranged at a minimum distance a1, a2 from an inner surface of the piston crown 3 facing the cooling channel 5. As an alternative to the weld beads 2 shown here, the lower housing part 1B and the upper housing part 1A can be joined to each other, for example, by brazing seams formed by the separation sections 6B.

[0051] The piston 10 has a radially outer first cooling fin 8, which extends with a first axial length LA1 from the piston crown 3, specifically from an inner surface of the piston crown 3 facing the cooling channel 5, into the cooling channel 5. Furthermore, the piston 10 has a radially inner second cooling fin 9, which extends with a second axial length LA2 from the piston crown 3, specifically from an inner surface of the piston crown 3 facing the cooling channel 5, in axial direction A into the cooling channel 5. As shown in the sectional view according to Fig. As can be seen in Figure 2, the cooling fins 8, 9 extend at least partially in the circumferential direction U through the cooling channel 5.

[0052] The first cooling fin 8 has a first proximal width bp1 adjacent to the piston crown 3, and the second cooling fin 9 has a second proximal width bp2 adjacent to the piston crown 3. Preferably, the cooling fins 8 and 9 are integrally formed with the upper housing part 1A, in particular with the piston crown 3.

[0053] The cooling channel 5 is subdivided into three cooling channels 5a, 5b, 5c by the cooling fins 8, 9. These comprise a first cooling channel 5a between the radially outer wall 16 and the first cooling fin 8, a second cooling channel 5b between the first cooling fin 8 and the second cooling fin 9, and a third cooling channel 5c, which is a radially inner cooling channel 5c between the second cooling fin 9 and the bowl-side wall 6. The piston crown 3 is further subdivided into three concavely curved bottom regions 4a, 4b, 4c by the two cooling fins 8, 9.

[0054] The second cooling fin 9 is arranged within the radially inner half of the cooling channel 5 with respect to its radial extension direction R. The two cooling fins 8, 9 are spaced at a substantially uniform distance from each other and from the respective adjacent walls 6, 16 of the piston housing 1.

[0055] The cooling fins 8 and 9 are asymmetrically designed and differ in their axial lengths LA1 and LA2. The second cooling fin 9 has a distal end section 92 that projects beyond the distal end 82 of the first cooling fin 8. The distal end section 92 thus projects beyond the distal end 82 of the first cooling fin 8 by the difference between the second axial length LA2 and the first axial length LA1.

[0056] The fluid inlet aid 90 of the second cooling fin 9 here comprises the distal end section 92 of the second cooling fin 9. The fluid inlet aid 90, comprising the distal end section 92, is arranged adjacent to the bowl-side wall 6 of the piston housing 1 and is designed to direct the cooling fluid KF via the cooling section channel inlet area KE into the third cooling section channel 5c and onto the fluid deflection area 90A. The fluid deflection area 90A then directs the cooling fluid KF towards the bowl-side wall 6 (compare Fig. 1) Because the distal end section 92, and thus the fluid inlet aid 90, preferably extends completely along the radially inner wall 6 in the region of the combustion chamber A0, the fluid inlet aid 90 and the subsequent fluid deflection section 90A direct cooling fluid KF onto the bowl-side wall 6 throughout the entire thermally highly stressed area. The defined narrowing of the cooling channel 5 in the cooling section channel inlet area KE between the fluid inlet aid 90 and the bowl-side wall 6 also causes an acceleration of the cooling fluid KF and promotes turbulence in this area without significantly impeding the inflow.

[0057] The axial lengths LA1, LA2 of the cooling fins 8, 9 are selected such that the minimum distance a1 of the radially outer projection 16A is greater than the first axial length LA1 – in this case, even greater than the axial length of both cooling fins 8, 9 – and the minimum distance a2 of the radially inner projection 6A is greater than the second axial length LA2 – in this case, even greater than the axial length of both cooling fins 8, 9. This prevents excessive narrowing of the cooling channel in the cooling section inlet area KE by the respective projection 6A, 16A and the cooling fins 8, 9.

[0058] Fig. Figure 3 shows a further embodiment of the piston 10, which differs from the one in solely by the design of the cooling fins 8, 9. Fig. The embodiment shown in section 2 differs. Identical or similar components have identical reference numerals, and reference is made to the description of piston 10 according to [reference to relevant section]. Fig. 2. Reference was made to the above and only the differences in the embodiments were discussed in detail.

[0059] In a known manner, a radially outer first cooling fin 8 and a radially inner second cooling fin 9 are provided. The fluid inlet aid 90 of the second cooling fin 9 comprises, in addition to the distally projecting end section 92, a radially inwardly facing surface 94 of the second cooling fin 9, which extends at least also in the direction of the bowl-side wall 6. In other words, the inwardly facing surface 94 of the second cooling fin 9 slopes obliquely towards the bowl-side wall 6. This inclination of the inwardly facing surface 94 is achieved by the radially inwardly facing surface 94 being inclined at an angle α2 relative to the axial direction A of the piston 10. The angle of inclination α2 is preferably in the range of 2° to 5°, particularly from 3° to 4°.

[0060] In addition to the second cooling fin 9, the first cooling fin 8 also extends at an angle of inclination α1 relative to the axial direction A with respect to a radially inner surface of the first cooling fin 8. The angle of inclination α1 of the first cooling fin 8 and the angle of inclination α2 of the second cooling fin 9 preferably correspond to each other. The first cooling fin 8 and the second cooling fin 9 extend at least partially in the circumferential direction U.

[0061] The radially outer wall 16 is preferably also provided with a slope in the area of ​​the first cooling fin 8, which is inclined radially inwards, so that the inclined design of the first cooling fin 8 prevents a narrowing of the first cooling section channel 5a and ensures sufficient flow of cooling fluid KF in this area.

[0062] Furthermore, at least the second cooling fin 9 – in this case both the first cooling fin 8 and the second cooling fin 9 – is tapered. The first cooling fin 8 tapers at an angle β1 of 2° to 4°, particularly preferably 2.75° to 3.25°, relative to the axial direction A. Furthermore, the second cooling fin 9 tapers at an angle β2 of 2° to 4°, particularly preferably 2.75° to 3.25°, relative to the axial direction A.

[0063] By inclined both the cooling fins 8, 9, and the radially outer wall 16 in the area of ​​the first cooling fin 8, three cooling channels 5a, 5b, 5c with essentially the same channel width in the radial extension direction R are provided.

[0064] Fig. Figure 4 shows a further embodiment of the piston 10, which differs from the one in the formation of the recess forming the combustion chamber A0 by the shape of the recess. Fig. 2 shown embodiment differs. The combustion chamber A0 is thereby formed by a design that differs from the one shown. Fig. A shallower recess is formed, which is particularly W-torus-shaped. An inner area of ​​the recess forming the combustion chamber A0 lies radially inside the curvature change area 7A. This area, in particular, is exposed to high thermal loads. The piston crown 3 is also subdivided into three concavely curved bottom areas 4a, 4b, 4c by the two cooling fins 8, 9. The piston crown 3, and thus the bottom areas 4a, 4b, 4c, are formed corresponding to the recess shape of the combustion chamber A0 and are offset both radially and axially. Accordingly, the first cooling fin 8 begins at a first extension distance LB1 with respect to an axially upper end of the piston crown 3, and the second cooling fin begins at a second extension distance LB2 with respect to the axially upper end of the piston crown 3. The first cooling fin 8 extends at least partially in the circumferential direction U.

[0065] The first cooling fin 8 extends from the piston crown 3 with a first proximal width bp1 to its distal end 82 with a first distal width bd1, which is smaller than the first proximal width bp1. The first cooling fin 8 extends either as shown on the left in Fig. 4 shown, completely or partially in axial direction A, or alternatively is completely or partially inclined radially inwards at a first angle of attack γ1 from the piston crown 3, as shown on the right in Fig. 4 illustrates.

[0066] The second, radially inner cooling fin 9 extends from the piston crown 3 with a second proximal width bp2 to its distal end section 92 with a second distal width bd2, which is smaller than the second proximal width bp2. Thus, the cooling fins 8, 9 become distally narrower, as also described in the embodiment according to Fig. 5 described.

[0067] The second cooling fin 9 extends at least partially in the circumferential direction U. Furthermore, the second cooling fin 9 is inclined radially outwards, either completely or partially, at a second angle y2 from the piston crown 3. This radial outward inclination at the second angle γ2 provides an enlarged cooling channel inflow area KE above the projection 6A. The fluid inflow aid 90, as well as the subsequent fluid deflection area 90A (formed here by the distal end section 92 and the radially inward-facing surface 94), directs increased amounts of cooling fluid KF into the radially inner cooling channel 5c and onto the trough-side wall 6, which runs obliquely along the shape of the trough.

[0068] Fig. Figure 5 shows a further embodiment of the piston 10, which differs from the one in solely by the design of the cooling fins 8, 9. Fig. The embodiment shown in section 2 differs. Identical or similar components have identical reference numerals, and reference is made to the description of piston 10 according to [reference to relevant section]. Fig. 2. Reference was made and only the differences were discussed.

[0069] In a known manner, a radially outer first cooling fin 8 and a radially inner second cooling fin 9 are provided. The fluid inlet aid 90 of the second cooling fin 9 comprises, in addition to the distally projecting end section 92, a radially inwardly curved surface 94 of the second cooling fin 9, which transitions into the fluid deflection area 90A and extends at least also in the direction of the bowl-side wall 6. In other words, the inwardly facing surface 94 of the second cooling fin 9 is curved in the direction of the bowl-side wall 6. The concavely shaped, radially inwardly curved surface 94 of the second cooling fin 9 directs an increased amount of cooling fluid KF toward the bowl-side wall 6, thus providing particularly effective cooling of the area of ​​the piston housing 1 around the combustion chamber A0. The first cooling fin 8 has a first radius of curvature r1, which is preferably in a range of 50 mm to 70 mm.The second cooling fin 9 has a second radius of curvature r2, which is preferably also in a range of 50 mm to 70 mm.

[0070] The first cooling fin 8 extends from the piston crown 3 with a first proximal width bp1 to its distal end 82 with a first distal width bd1, which is smaller than the first proximal width bp1. The second cooling fin 9 extends from the piston crown 3 with a second proximal width bp2 to its distal end section 92 with a second distal width bd2, which is smaller than the second proximal width bp2. In other words, the cooling fins 8, 9 become narrower distally, thus facilitating the flow of cooling fluid KF into the cooling channels 5a, 5b, 5c separated by them.

[0071] The first cooling fin 8 and the second cooling fin 9 extend at least partially in the circumferential direction U.

[0072] Fig. Figure 6 shows a further embodiment of the piston 10. The design of the recess forming the combustion chamber A0, including the piston crown 3 and thus the bottom areas 4a, 4b, 4c, corresponds to that shown in Fig. 4 embodiment shown. As already mentioned in connection with the embodiment according to Fig. As described in section 4, the piston crown 3 and thus the bottom areas 4a, 4b, 4c are formed corresponding to the bowl shape of the combustion chamber A0, such that the first cooling fin 8 begins at a first starting distance LB1 with respect to an axially upper end of the piston crown 3 and the second cooling fin begins at a second starting distance LB2 with respect to the axially upper end of the piston crown 3.

[0073] Thus, the one in Fig. 6 embodiment shown, compared to the embodiment according to Fig. 4 primarily through the formation of the cooling fins 8, 9.

[0074] The first cooling fin 8 extends from the piston crown 3 with a first proximal width bp1 to its distal end 82 with a first distal width bd1, which is smaller than the first proximal width bp1. Furthermore, the first cooling fin 8 is inclined radially inwards from the piston crown 3 at a first angle y1, but can alternatively also extend in the axial direction A. The second, radially inner cooling fin 9 extends from the piston crown 3 with a second proximal width bp2 to its distal end section 92 with a second distal width bd2, which is smaller than the second proximal width bp2. Thus, the cooling fins 8, 9 become narrower distally, as also described in the embodiment according to Fig. 5 described. Furthermore, the second cooling fin 9 is inclined radially outwards from the piston crown 3 at a second angle of attack y2. The second cooling fin 9, as also described in connection with Fig. As described in section 5, a second radius of curvature r2 is provided, preferably in a range of 50 mm to 70 mm. Due to the radial outward inclination at the second angle of attack γ2, an enlarged cooling section channel inflow area KE is provided above the projection 6A, and the fluid inflow aid 90, as well as the subsequent fluid deflection area 90A, here formed by the distal end section 92 and the curved and radially inward-facing surface 94, directs increased amounts of cooling fluid KF into the radially inner cooling section channel 5c and onto the trough-side wall 6, which runs obliquely along the trough shape. The second angle of attack γ2, in combination with the curvature of the radially inward-facing surface 94, thus takes into account the difference compared to the embodiment according to [reference missing]. Fig. 5. Deviating course of the trough-side wall 6. REFERENCE MARK LIST 1 Piston housing 1A upper housing part 1B lower housing part 2 weld beads 3 piston crown 4a first concave curved floor area 4b second concave curved floor area 4c third concave curved floor area 5 Cooling channel 5a first cooling channel 5b second cooling channel 5c third (radial inner) cooling channel 6 trough-side (radially inner) wall 6A radial inner projection 6B Separation section 7A Curvature Change Area 7 beam splitters 8 first cooling fin 9 second cooling fin 16 radial outer wall 16A radial outer projection 10 pistons 82 distal end of the first cooling fin 84 radially inward-facing surface of the first cooling fin 90 Fluid flow aid 90A Fluid deflection range 92 distal end section of the second cooling fin 94 radially inward-facing surface of the second cooling fin 100 internal combustion engine A0 combustion chamber A1-A3 ring-shaped groove A axial direction U circumferential direction R radial direction of extension KF cooling fluid KE cooling channel inlet area T dividing line LA1, LA2 first axial length LB1, LB2 approach distance r1, r2 radius of curvature α1, α2 Inclination angle bp1, bp2 proximal width bd1, bd2 distal width β1, β2 angles γ1, γ2 angle of attack a, a1, a2 Minimum distance QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 210 626 A1

[0006] US 10,247,133 B2

[0006]

Claims

Piston (10) for an internal combustion engine (100), comprising: - a piston housing (1) forming a radially inner combustion chamber (A0) and in which a radially outer cooling channel (5) surrounding the combustion chamber (A0) is enclosed for guiding a cooling fluid (KF), - a radially outer first cooling fin (8) extending with a first axial length (LA1) from an inner surface of a piston crown (3) facing the cooling channel (5) into the cooling channel (5) and at least partially in the circumferential direction (U) through the cooling channel (5), - a radially inner second cooling fin (9) extending with a second axial length (LA2) from the inner surface of the piston crown (3) facing the cooling channel (5) into the cooling channel (5) and at least partially in the circumferential direction (U) through the cooling channel (5), - a number of separating sections (6B) which divide the piston housing (1) into an upper Separate housing part (1A) and a lower housing part (1B),wherein the separation sections (6B) are arranged at a minimum distance (a) from the inner surface of the piston crown (3) facing the cooling channel (5), which is greater than the axial length (LA1, LA2) of at least the cooling fin (8, 9) arranged adjacent to the respective separation section (6B), preferably greater than the axial length (LA1, LA2) of both cooling fins (8, 9), wherein the second cooling fin (9) runs adjacent to a bowl-side wall (6) of the piston housing (1) and separates a radially inner cooling section channel (5c). Piston (10) according to claim 1, wherein the radially inner cooling channel (5c) has a fluid deflection area (90A) for directing the cooling fluid (KF) towards the bowl-side wall (6), and the second cooling fin (9) has a fluid inflow aid (90) arranged and designed to assist the flow of the cooling fluid (KF) into the radially inner cooling channel (5c) and along the fluid deflection area (90A) towards the bowl-side wall (6). Piston (10) according to claim 2, wherein the fluid inflow aid (90) comprises a distal end section (92) of the second cooling rib (9) projecting into the cooling channel (5) opposite the first cooling rib (8). Piston (10) according to claim 3, wherein the distal end section (92) extends from the inner surface of the piston crown (3) facing the cooling channel (5) at least 70%, in particular at least 80%, further into the cooling channel (5) than a distal end (82) of the first cooling fin (8). Piston (10) according to one of claims 2 to 4, wherein the fluid inlet aid (90) at least partially comprises a radially inwardly directed surface (94) of the second cooling fin (9), which extends at least also in the direction of the bowl-side wall (6). Piston (10) according to claim 5, wherein the radially inwardly facing surface (94) of the second cooling fin (9) is inclined relative to an axial direction (A) of the piston (10), in particular at an inclination angle (α2) of 2° to 5°, in particular of 3° to 4°. Piston (10) according to claim 6, wherein the radially inwardly facing surface (94) of the second cooling fin (9) is concave, in particular having a radius of curvature (r1, r2) in a range of 50 mm to 70 mm, in particular from 55 mm to 65 mm, particularly preferably from 57.5 mm to 62.5 mm. Piston (10) according to one of the preceding claims, wherein the first cooling fin (8) and the second cooling fin (9) are asymmetrically designed and differ by at least one of the following: - the axial length (LA1, LA2), - an inclination angle (α1, α2) of a radially inwardly facing surface (84, 94) relative to an axial direction (A), - a radius of curvature (r1, r2) of a radially inwardly facing surface (84, 94) relative to an axial direction (A), - a proximal width (bpl, bp2) at the piston crown (3), - a distal width (bd1, bd2). Piston (10) according to one of the preceding claims, wherein at least the second cooling fin (9) is tapered, in particular with an angle (β1, β2) of 2° to 4°, particularly preferably of 2.75° to 3.25° relative to an axial direction (A) of the piston (10). Piston (10) according to one of the preceding claims, wherein the second cooling fin (9) is arranged within the radially inner half of the cooling channel (5) with respect to a radial extension direction (R) of the cooling channel (5), preferably the first cooling fin (8) and the second cooling fin (9) are arranged uniformly to each other and to at least a section of the respective adjacent wall (6, 16) in the radial extension direction (R), so that the cooling channel (5) is divided into three channel sections (5a, 5b, 5c) which have at least a uniform channel width in the radial extension direction (R). Internal combustion engine with a piston (10) according to one of claims 1 to 10, wherein the piston (10) forms a combustion chamber (A0) for a combustion reaction of the internal combustion engine.

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