Aluminium piston

Abstract

The invention relates to an aluminium piston (8) for an internal combustion engine (7), having a piston head (11) and a piston skirt (10) connected to the piston head (11), wherein the aluminium piston (8) has a nominal piston diameter (37), wherein the nominal piston diameter (37) is 8.5 cm to 14 cm, and wherein a ratio of the magnitude of a piston mass (m) in grams of the aluminium piston (8) to the cube of the magnitude of the nominal piston diameter (37) in centimetres is 0.7 to 0.95.

Description

[0001] RKS24003PWO APQ24001 WO

[0002] Kolbenschmidt Pistons Germany GmbH

[0003] 1 ALUMINUM PISTON

[0004] The present invention relates to an aluminum piston for an internal combustion engine.

[0005] To reduce carbon dioxide and hydrocarbon emissions from internal combustion engines, as well as to improve fuel consumption, it is necessary, on the one hand, to reduce the mass of such an aluminum piston and, on the other hand, to lower sliding friction during the piston's up-and-down movement in the cylinder by reducing the size of the load-bearing skirt wall sections. Aluminum pistons with a box-type design generally meet these requirements, but there is still room for improvement.

[0006] Against this background, one object of the present invention is to provide an improved aluminum piston for an internal combustion engine.

[0007] Accordingly, an aluminum piston for an internal combustion engine is proposed, comprising a piston head and a piston skirt connected to the piston head. The aluminum piston has a nominal piston diameter of 8.5 cm to 14 cm. Furthermore, the ratio of the piston mass, expressed in grams, to the cube of the nominal piston diameter, expressed in centimeters, is 0.7 to 0.95.

[0008] The internal combustion engine can be a gasoline or diesel engine. It can consist of an engine block and several aluminum pistons housed in piston bores within the engine block. The internal combustion engine RKS24003PWO APQ24001 WO

[0009] Kolbenschmidt Pistons Germany GmbH

[0010] 2 can be powered by diesel fuel, hydrogen, gasoline or other fuels.

[0011] The aluminum piston can, in particular, be assigned an axis of symmetry, central axis, or piston stroke axis, with respect to which the aluminum piston can be essentially rotationally symmetrical. In the present context, the terms axis of symmetry, central axis of the aluminum piston, or piston stroke axis can be interchanged as appropriate. The aforementioned piston stroke axis can, in particular, be formed by the central axis of a cylinder that encloses surfaces of the piston skirt of the aluminum piston and has a minimum diameter, wherein the central axis of this cylinder is arranged perpendicular to a piston pin bore of the aluminum piston, in particular to a pin bore axis or the central axis of the piston pin bore.

[0012] The aluminum piston can also be assigned a coordinate system with a width direction (x-direction), a depth direction (y-direction), and a height direction (z-direction). The z-direction can also be referred to as the axial direction. The terms "z-direction" and "axial direction" are therefore interchangeable. The directions are perpendicular to each other. The piston stroke axis coincides with the z-direction or is oriented parallel to it. The aluminum piston also has a radial direction. The radial direction is perpendicular to the piston stroke axis and points away from it.

[0013] The piston head and piston skirt can be two separate components that are joined together to form the aluminum piston. For example, the piston head and piston skirt can be bonded together using a material-bonded connection. Material-bonded connections are permanent bonds that can only be separated by destroying the bonding agent and / or the bonded parts. RKS24003PWO APQ24001 WO can be material-bonded.

[0014] Kolbenschmidt Pistons Germany GmbH

[0015] 3. For example, they can be joined by welding. For instance, the piston head and the piston shaft are welded together.

[0016] The aluminum piston is preferably made of an aluminum alloy. Other elements besides aluminum can also be used as alloying components. The aluminum piston can be machined, for example, from a solid piece of material, or cast.

[0017] The nominal piston diameter is defined, in particular, as the diameter of the smallest possible cylinder that encloses a so-called piston skirt of the aluminum piston, i.e., sections of the piston skirt wall of the aluminum piston. This cylinder is oriented perpendicular to the pin bore axis of the piston pin bore of the aluminum piston. In other words, the nominal piston diameter is the minimum diameter of the cylinder whose central axis coincides with the piston stroke axis and which encloses the surfaces of the piston skirt of the aluminum piston, wherein the central axis of this cylinder is arranged perpendicular to the piston pin bore of the aluminum piston, in particular to a pin bore axis or the central axis of the piston pin bore. The nominal piston diameter can therefore, in particular, be associated with the piston skirt.The nominal piston diameter is the inner diameter of the cylinder that guides the aluminum piston precisely along the piston stroke axis. The nominal piston diameter can also be referred to as the nominal piston diameter. Specifically, a first skirt wall section and a second skirt wall section are provided. These skirt wall sections together form the piston skirt of the aluminum piston. The skirt wall sections can be connected to each other by means of box wall sections. The nominal piston diameter is preferably specified in centimeters (cm). RKS24003PWO APQ24001 WO.

[0018] Kolbenschmidt Pistons Germany GmbH

[0019] 4

[0020] The piston mass of an aluminum piston is defined as the total mass of the aluminum piston, i.e., the total mass formed by the material of the aluminum piston. The piston mass can be determined, for example, using a CAD (Computer Aided Design) model of the aluminum piston or calculated by taking into account the average density of the aluminum piston. The piston mass is preferably given in grams (g).

[0021] When calculating the ratio of piston mass to nominal piston diameter, the piston mass is given in grams (g) and the nominal piston diameter in centimeters (cm), with the nominal piston diameter in centimeters being cubed in the calculation. The ratio of the absolute value of the aluminum piston mass in grams to the cube of the absolute value of the nominal piston diameter in centimeters is therefore between 0.7 and 0.95. In other words, there is a relationship between the nominal piston diameter [DK] given in centimeters (cm), the piston mass [MK] given in grams (g), and a scalar factor [F] such that MK = DK. 3 * F * g / cm 3 , where the factor [F] is between 0.7 and 0.95.

[0022] By means of the geometric design of the aluminum piston described above, taking into account the above ratios, the aluminum piston can be reduced both in terms of piston mass and in terms of the size, in particular the surface area, of the shaft wall sections, so that reduced friction occurs during the operation of the internal combustion engine.

[0023] According to one embodiment, the nominal piston diameter is 9 cm to 11 cm. RKS24003PWO APQ24001 WO

[0024] Kolbenschmidt Pistons Germany GmbH

[0025] 5

[0026] This allows the aluminum piston to be further improved with regard to its piston mass and / or with regard to the size of the friction-generating shaft wall sections.

[0027] According to another embodiment, the ratio of the amount of the piston mass of the aluminum piston, specified in grams, to the third power of the amount of the nominal piston diameter, specified in centimeters, is 0.77 to 0.86.

[0028] According to a further embodiment, the piston shaft has a first shaft wall section, a second shaft wall section opposite the first shaft wall section, a first box wall section, and a second box wall section opposite the first box wall section. The first box wall section and the second box wall section connect the first shaft wall section to the second shaft wall section.

[0029] The first cylinder wall section, the second cylinder wall section, the first shaft wall section, and the second shaft wall section form four outer surfaces of the piston shaft, arranged around the piston stroke axis. The first cylinder wall section and the second cylinder wall section can be mirror images of each other. Likewise, the first shaft wall section and the second shaft wall section can be mirror images of each other. However, it is also conceivable that the first shaft wall section and the second shaft wall section have different designs. The shaft wall sections can be rotationally symmetrical about the piston stroke axis, at least in sections. In particular, the shaft wall sections do not form a complete cylinder. The first shaft wall section forms a pressure side of the aluminum piston, while the second shaft wall section forms a counter-pressure side of the aluminum piston.RKS24003PWO APQ24001 WO.

[0030] Kolbenschmidt Pistons Germany GmbH

[0031] 6

[0032] This relationship can also be reversed. For example, differently designed piston skirt sections can accommodate the fact that different maximum lateral forces can occur on the pressure and back pressure sides during operation of the internal combustion engine. Furthermore, the reduced piston mass and / or reduced stiffness of the aluminum piston, combined with an asymmetrically crowned running clearance achieved through the differently designed piston skirt sections, can reduce piston noise during operation. In particular, piston noise can be further reduced by combining a less stiff and therefore more flexible design of the aluminum piston with a running clearance adapted to the different lateral forces on the pressure and back pressure sides, featuring asymmetric crowning curves.The piston pin bore penetrates the cylinder wall sections. A pin bore axis is assigned to the piston pin bore, representing its axis of symmetry or center. The cylinder wall sections and the cylinder wall sections enclose an interior space within the piston skirt. This interior space is open in a direction away from the piston head. A bolt for connecting the aluminum piston to a connecting rod of the internal combustion engine can pass through this interior space along the pin bore axis.

[0033] According to a further embodiment, the ratio of a first shaft width of the first shaft wall section and / or a second shaft width of the second shaft wall section to the nominal piston diameter is 0.5 to 0.7, in particular 0.55 to 0.65.

[0034] The following refers to a bolt cutting plane oriented perpendicular to the piston stroke axis. Furthermore, the bolt cutting plane, starting from the bolt bore axis, is ten percent of an RKS24003PWO APQ24001 WO.

[0035] Kolbenschmidt Pistons Germany GmbH

[0036] 7

[0037] The piston pin bore diameter is offset towards the piston head. The piston pin bore diameter represents either the inner diameter of the piston pin bore or the outer diameter of the pin. Furthermore, the first and second shaft wall sections each have an outer edge on both sides. Each outer edge separates one of the shaft wall sections from one of the cylinder wall sections. The first shaft width is then defined as the shortest distance between two points, one of which is formed by an intersection of the bolt section plane with the outer edge that separates the first shaft wall section from the first cylinder wall section, and the other point is formed by an intersection of the bolt section plane with the outer edge that separates the first shaft wall section from the second cylinder wall section.The second shaft width is defined as the shortest distance between two further points, one of which is formed by an intersection of the bolt cutting plane with the outer edge that separates the second shaft wall section from the first box wall section, and the other further point is formed by an intersection of the bolt cutting plane with the outer edge that separates the second shaft wall section from the second box wall section. The first shaft width can be smaller, larger, or equal to the second shaft width.

[0038] According to another embodiment, the ratio of the box wall distance between the first box wall section and the second box wall section to the nominal piston diameter is 0.8 to 0.95, in particular 0.81 to 0.91.

[0039] The box wall distance is defined as the shortest distance between a first point of a first section line, formed by a section of the first box wall segment or a first bore reinforcement with an RKS24003PWO APQ24001 WO

[0040] Kolbenschmidt Pistons Germany GmbH

[0041] 8. The distance between the piston and cylinder walls is defined by a plane spanned by the piston stroke axis and the pin bore axis, and a second point on a second section line formed by a section of the second cylinder wall segment or a second bore reinforcement with the aforementioned plane. Here, the first point is the point on the first section line furthest from the piston stroke axis, and the second point is the point on the second section line furthest from the piston stroke axis. In other words, the cylinder wall distance corresponds to the distance that would be measured if the piston skirt were measured radially outwards on both sides along the pin bore axis within the aforementioned plane.

[0042] According to a further embodiment, the piston skirt has a first hub wall section, which is at least partially enclosed by the first box wall section, and a second hub wall section, which is at least partially enclosed by the second box wall section. A piston pin bore extends through both the first hub wall section and the second hub wall section. In particular, the first hub wall section is recessed behind, projects beyond, or is flush with the first box wall section, and the second hub wall section is recessed behind, projects beyond, or is flush with the second box wall section.

[0043] The first hub wall section and the second hub wall section are preferably arranged parallel to each other. In particular, areas of the first hub wall section and the second hub wall section that are adjacent to the piston pin bore are arranged parallel to each other. In contrast, the first box wall section and the second box wall section are arranged in a V-shape relative to each other. In particular, the first box wall section and the second box wall section converge in the z-direction, i.e., with increasing proximity to the piston head. The RKS24003PWO APQ24001 WO

[0044] Kolbenschmidt Pistons Germany GmbH

[0045] 9

[0046] The shaft wall sections, the box wall sections and the hub wall sections refer in particular to radially outer surfaces of the piston shaft, i.e., surfaces facing away from the piston stroke axis.

[0047] According to a further embodiment, the first hub wall section and the second hub wall section each have convex and concave regions, wherein the convex regions adjoin the piston pin bore and the concave regions are located outside the convex regions with respect to the piston pin bore and adjoin the convex regions. In particular, the first box wall section adjoins the concave regions of the first hub wall section, while the second box wall section adjoins the concave regions of the second hub wall section.

[0048] In particular, the hub wall sections each consist exclusively of two convex areas arranged on both sides of the piston pin bore and two concave areas arranged on both sides of the piston pin bore, wherein the areas described above together form the entire first hub wall section or the entire second hub wall section.

[0049] According to a further embodiment, the first box wall section and the second box wall section are convexly shaped. In particular, the first box wall section and the second box wall section form arc lines circumferentially around a piston stroke axis within a bolt cutting plane, wherein the piston head is shaped circumferentially around the piston stroke axis and the bolt cutting plane is arranged perpendicular to the piston stroke axis and intersects the piston pin bore.

[0050] In particular, the box wall sections each consist exclusively of two convex areas arranged on either side of the piston pin bore. RKS24003PWO APQ24001 WO

[0051] Kolbenschmidt Pistons Germany GmbH

[0052] 10

[0053] According to a further embodiment, the connecting lines along which the first box wall section is joined to the first hub wall section, or along which the second box wall section is joined to the second hub wall section, are inclined radially inwards. Thus, the connecting lines continuously approach the piston stroke axis as they get closer to the piston head.

[0054] In particular, the connecting lines approach the piston stroke axis continuously as they get closer to the piston head. These connecting lines can be straight or curved.

[0055] According to a further embodiment, within the plane of the bolt section, the first hub wall section and the first box wall section together form a double S-curve on both sides of the piston pin bore. In particular, within the plane of the bolt section, the second hub wall section and the second box wall section together form another double S-curve on both sides of the piston pin bore.

[0056] In particular, the first hub wall section and the first box wall section together form a double S-curve on both sides of the piston pin bore within the plane of the bolt section. Likewise, the second hub wall section and the second box wall section together form a double S-curve on both sides of the piston pin bore within the plane of the bolt section.

[0057] According to a further embodiment, the first box wall section has a first bore reinforcement and the second box wall section has a second bore reinforcement. Here, the bore reinforcements reinforce cross-sectional areas of the first box wall section and RKS24003PWO APQ24001 WO

[0058] Kolbenschmidt Pistons Germany GmbH

[0059] 11

[0060] Cross-sectional areas of the second box wall section both along the piston stroke axis and radially outwards.

[0061] The bore reinforcements can also be referred to as bulges or bearing reinforcements for the piston pin. These reinforcements serve to mechanically strengthen the cylinder wall sections and / or the hub wall sections in the area of ​​the piston pin bore. This helps prevent the pin from breaking out and / or the cylinder wall sections and / or the hub wall sections from fracturing.

[0062] According to another embodiment, the first box wall section and the second box wall section together form an undercut.

[0063] According to a further embodiment, the outer edges of the first shaft wall section and the outer edges of the second shaft wall section each run along a straight line. In particular, all outer edges run parallel to each other.

[0064] In particular, all outer edges can run parallel to the piston stroke axis.

[0065] According to a further embodiment, the widths of a development of the first shaft wall section and / or a development of the second shaft wall section decrease continuously distal to the piston head.

[0066] The developments here refer to surfaces formed by an imaginary unrolling of the first and / or second shaft wall sections onto a plane parallel to the piston stroke axis and parallel to the bolt bore axis. The widths of these developments denote dimensions of the developments along the y-direction, i.e., parallel to the y-axis.

[0067] Kolbenschmidt Pistons Germany GmbH

[0068] 12 to the bolt bore axis, at a specific position along the z-direction, i.e., along the piston stroke axis. In this context, "distal to the piston head" can be understood as a direction away from the piston head, starting from the piston skirt, along the piston stroke axis.

[0069] According to another embodiment, the aluminum piston has at least one oil nozzle recess.

[0070] The at least one oil nozzle recess can be located at the ends of the piston skirt sections furthest from the piston head. In particular, the at least one oil nozzle recess is located at an end of one of the outer edges furthest from the piston head. In other words, the at least one oil nozzle recess is located at a transition between one of the skirt sections and one of the cylinder wall sections. However, the at least one oil nozzle recess can also be located elsewhere. In particular, the at least one oil nozzle recess can be located on the pressure side and / or on the counter-pressure side of the aluminum piston. The at least one oil nozzle recess represents a round or arc-shaped reduction. The at least one oil nozzle recess can have the shape of a circular segment.The at least one oil jet recess provides a free space within at least one of the piston bores of the internal combustion engine's engine block for the integration of at least one oil jet (not shown) within the piston bores of the engine block. Furthermore, the piston mass can also be further reduced.

[0071] Furthermore, an internal combustion engine with at least one such aluminum piston is proposed.

[0072] The internal combustion engine can be a diesel engine or a gasoline engine, in particular a hydrogen-powered gasoline engine. The internal combustion engine can be an RKS24003PWO APQ24001 WO.

[0073] Kolbenschmidt Pistons Germany GmbH

[0074] 13

[0075] The engine block comprises several aluminum pistons housed in piston bores within the engine block. For example, the internal combustion engine can have three, four, five, six, or more than six aluminum pistons. "Hydrogen-powered" in this context means that the internal combustion engine burns gaseous hydrogen with the addition of atmospheric oxygen. Through the combustion of the hydrogen, chemical energy is converted into mechanical work by the internal combustion engine.

[0076] The embodiments and features described for the proposed aluminium piston apply accordingly to the proposed internal combustion engine and vice versa.

[0077] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other numerical term used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise indicated.

[0078] Other possible implementations of the aluminum piston and / or the internal combustion engine also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the aluminum piston and / or the internal combustion engine.

[0079] Further advantageous embodiments and aspects of the aluminum piston and / or the internal combustion engine are the subject of the dependent claims and the exemplary embodiments of the aluminum piston and / or the internal combustion engine described below. The aluminum piston RKS24003PWO APQ24001 WO is further described below.

[0080] Kolbenschmidt Pistons Germany GmbH

[0081] 14 and / or the internal combustion engine is explained in more detail with reference to preferred embodiments and the accompanying figures.

[0082] Fig. 1 shows a schematic side view of an embodiment of a vehicle!

[0083] Fig. 2 shows a schematic perspective view of an embodiment of an aluminum piston for an internal combustion engine of the vehicle according to Fig. 1;

[0084] Fig. 3 shows another schematic perspective view of the aluminum piston according to Fig. 2;

[0085] Fig. 4 shows a schematic sectional view of the aluminum piston according to Fig. 2;

[0086] Fig. 5 shows another schematic sectional view of the aluminum piston according to Fig. 2;

[0087] Fig. 6 shows another schematic sectional view of the aluminum piston according to Fig. 2;

[0088] Fig. 7 shows a schematic side view of the aluminum piston according to Fig. 2;

[0089] Fig. 8 shows another schematic side view of the aluminum piston according to Fig. 2; and

[0090] Fig. 9 shows another schematic perspective view of the aluminum piston according to Fig. 2. RKS24003PWO APQ24001 WO

[0091] Kolbenschmidt Pistons Germany GmbH

[0092] 15

[0093] In the figures, identical or functionally equivalent elements have been given the same reference symbols, unless otherwise indicated.

[0094] Figure 1 shows a schematic side view of an embodiment of a vehicle 1. The vehicle 1 is a motor vehicle, in particular a passenger car. The vehicle 1 can also be a commercial vehicle, for example a truck, a harvester, or a construction machine. Furthermore, the vehicle 1 can also be a military vehicle. In addition, the vehicle 1 can also be an aircraft, a watercraft, or a rail vehicle.

[0095] The vehicle 1 comprises a body 2, which encloses a passenger compartment or vehicle interior 3 of the vehicle 1. A driver and passengers can be located in the vehicle interior 3. The body 2 separates a surrounding area 4 of the vehicle 1 from the vehicle interior 3. The vehicle interior 3 is accessible from the surrounding area 4 by means of doors.

[0096] Vehicle 1 comprises a chassis with several wheels 5, 6. The number of wheels 5, 6 is arbitrary. Preferably, vehicle 1 has four wheels 5, 6. However, vehicle 1 can, for example, have six wheels 5, 6. The wheels 5, 6 are part of the chassis of vehicle 1. Only two wheels 5, 6 can be driven. However, all wheels 5, 6 can also be driven. In this case, vehicle 1 is an all-wheel-drive vehicle.

[0097] Vehicle 1 comprises an internal combustion engine 7. The internal combustion engine 7 can be a diesel or gasoline engine. Vehicle 1 can be powered solely by the internal combustion engine 7. However, vehicle 1 can also be a hybrid vehicle. In this case, vehicle 1 has at least one electric motor in addition to the internal combustion engine 7. RKS24003PWO APQ24001 WO

[0098] Kolbenschmidt Pistons Germany GmbH

[0099] 16

[0100] The internal combustion engine 7 comprises an engine block and several aluminum pistons housed in piston bores of the engine block. For example, the internal combustion engine 7 can have three, four, five, six, or more than six aluminum pistons.

[0101] Fig. 2 shows a schematic perspective view of an embodiment of an aluminum piston 8 for the internal combustion engine 7. Fig. 3 shows another schematic perspective view of the aluminum piston 8. Fig. 4 shows a schematic sectional view of the aluminum piston 8. Fig. 5 shows another schematic sectional view of the aluminum piston 8. Fig. 6 shows another schematic sectional view of the aluminum piston 8. Fig. 7 shows a schematic side view of the aluminum piston 8. Fig. 8 shows another schematic side view of the aluminum piston 8.

[0102] Figure 9 shows another schematic perspective view of the aluminum piston 8. Reference is subsequently made to Figures 2 to 9 simultaneously.

[0103] The aluminum piston 8 can be part of the vehicle 1 described above, in particular the internal combustion engine 7. However, it is especially preferred that the aluminum piston 8 be part of a commercial vehicle. In this case, the vehicle 1 is a commercial vehicle. The internal combustion engine 7, and thus the aluminum piston 8, can be used in any vehicle, ship, machine, or the like. Furthermore, the internal combustion engine 7, or the aluminum piston 8, can also be used for stationary applications, such as generators, power, heat, or the like.

[0104] The aluminum piston 8 can be composed of several sub-components that are bonded together by metallurgical forces. In metallurgical bonds, the bonding partners are held together by atomic or molecular forces. Metallurgical bonds are inseparable connections that can only be broken by destroying the bonding agents and / or the RKS24003PWO APQ24001 WO

[0105] Kolbenschmidt Pistons Germany GmbH

[0106] 17. The connecting partners can be separated again. Material bonding can be achieved, for example, by gluing, soldering, or welding. For example, the previously mentioned sub-components of the aluminum piston 8 are welded together, in particular friction welded.

[0107] The aluminum piston 8 can have an axis of symmetry, central axis, or piston stroke axis 9, with respect to which the aluminum piston 8 can be essentially rotationally symmetric. The aluminum piston 8 is associated with a coordinate system with a horizontal direction or x-direction x, a vertical direction or y-direction y, and a vertical direction or z-direction z. The z-direction z can also be referred to as the axial direction. The terms "z-direction" and "axial direction" are therefore interchangeable. The directions x, y, and z are oriented perpendicular to each other. The piston stroke axis 9 coincides with the z-direction z or is oriented parallel to it. The aluminum piston 8 is also associated with a radial direction R. The radial direction R is oriented perpendicular to the piston stroke axis 9 and points away from it.

[0108] The aluminum piston 8 has a piston base or piston skirt 10 and a piston head 11. Viewed along the piston stroke axis 9, the piston skirt 10 is located below the piston head 11. The piston skirt 10 has a piston hub with a piston pin bore 12, in which a pin (not shown) for coupling the aluminum piston 8 to a connecting rod (not shown) of the internal combustion engine 7 can be received. A pin bore axis 13, which represents a symmetry or central axis of the piston pin bore 12, intersects the piston stroke axis 9. Furthermore, the pin bore axis 13 is oriented perpendicular to the piston stroke axis 9. The pin bore axis 13 coincides with or is oriented parallel to the y-direction y. RKS24003PWO APQ24001 WO

[0109] Kolbenschmidt Pistons Germany GmbH 18

[0110] In the orientation shown in Fig. 5, a shaft wall section 14, 15 is provided on both sides of the piston pin bore 12. A first shaft wall section 14 and a second shaft wall section 15 are provided. The shaft wall sections 14, 15 can be partially cylindrical. In other words, the shaft wall sections 14, 15 can form parts of a cylinder that is rotationally symmetrical about the piston stroke axis 9. The shaft wall sections 14, 15 together form a so-called piston skirt of the aluminum piston 8. The shaft wall sections 14, 15 can be partially rotationally symmetrical about the piston stroke axis 9. However, the shaft wall sections 14, 15 do not form a complete cylinder. One of the shaft wall sections 14, 15 forms a pressure side of the aluminium piston 8, while the other of the shaft wall sections 14, 15 forms a counter-pressure side of the aluminium piston 8.

[0111] The shaft wall sections 14, 15 are connected to each other by means of box wall sections 16, 17. A first box wall section 16 and a second box wall section 17 are provided. The radial direction R points outwards from the piston stroke axis 9 in the direction of the shaft wall sections 14, 15. The piston pin bore 12 penetrates the box wall sections 16, 17. The shaft wall sections 14, 15 and the box wall sections 16, 17 enclose an interior space 18 of the piston shaft 10. The interior space 18 is open downwards in the orientation shown in Figures 2 to 5, 7 and 8. The previously mentioned bolt for coupling the aluminum piston 8 to the connecting rod runs through the interior space 18 along the bolt bore axis 13.

[0112] Furthermore, the piston skirt 10 has a hub wall section 19, 20 on both sides of the interior 18, which at least partially encloses the piston pin bore 12. The piston pin bore 12 therefore passes through the hub wall sections 19, 20. A first hub wall section 19 and a second hub wall section 20 are provided. The first RKS24003PWO APQ24001 WO

[0113] Kolbenschmidt Pistons Germany GmbH 19

[0114] Hub wall section 19 is at least partially enclosed by the first box wall section 16, and the second hub wall section 20 is at least partially enclosed by the second box wall section 17. The first hub wall section 19 and the second hub wall section 20 are arranged parallel to each other. In particular, those areas of the first hub wall section 19 and the second hub wall section 20 that are adjacent to the piston pin bore 12 are arranged parallel to each other. In contrast, the first box wall section 16 and the second box wall section 17 are arranged in a V-shape relative to each other. Specifically, the first box wall section 16 and the second box wall section 17 converge in the z-direction, i.e., from the piston skirt 10 towards the piston head 11; consequently, their distance from each other decreases continuously in this direction.The shaft wall sections 14, 15, the box wall sections 16, 17 and the hub wall sections 19, 20 here refer in particular to radially outer surfaces of the piston shaft 10, i.e., surfaces facing away from the piston stroke axis 9.

[0115] The first cylinder wall section 16 has a first bore reinforcement 21, which, in the illustrations of Figures 2 to 5 and 7 to 9, is arranged below the piston pin bore 12 and reinforces a cross-sectional area of ​​the first cylinder wall section 16 (not shown) at this location or in this area. Viewed along the z-direction z, the first bore reinforcement 21 forms a convex bulge of the first cylinder wall section 16 downwards, i.e., opposite to the y-direction y. The first bore reinforcement 21 contributes to a mechanical strengthening of the first cylinder wall section 16 in the area of ​​the piston pin bore 12, for example, to prevent the first cylinder wall section 16 and / or the first hub wall section 19 from breaking due to the loads introduced via the connecting rod. The second box wall section 17 has a second bore reinforcement 22, which is designed analogously to the first bore reinforcement 21.The RKS24003PWO APQ24001 WO.

[0116] Kolbenschmidt Pistons Germany GmbH

[0117] 20

[0118] The statements regarding the first bore reinforcement 21 apply accordingly to the second bore reinforcement 22 and vice versa.

[0119] The first shaft wall section 14 and the second shaft wall section 15 each have an outer edge 23, 24, 25, 26 on both sides. A first outer edge 23 separates the first shaft wall section 14 from the first box wall section 16. A second outer edge 24 separates the first shaft wall section 14 from the second box wall section 17. A third outer edge 25 separates the second shaft wall section 15 from the first box wall section 16. A fourth outer edge 26 separates the second shaft wall section 15 from the second box wall section 17. The outer edges 23, 24, 25, 26 each run along a straight line. Furthermore, the outer edges 23, 24, 25, 26 are each oriented parallel to the y-direction y.

[0120] In the following, reference is made to a bolt section plane 27, which is oriented perpendicular to the piston stroke axis 9. Furthermore, the bolt section plane 27 is offset from the bolt bore axis 13 by ten percent of a bolt bore diameter 28 of the piston pin bore 12 in the direction of the piston head 11. The bolt bore diameter 28 here represents an inner diameter of the piston pin bore 12 or an outer diameter of the bolt (not shown).

[0121] Within the bolt section plane 27, the first box wall section 16 and the first hub wall section 19 together form a double S-curve 29, 30 on both sides of the piston pin bore 12. Furthermore, the second box wall section 17 and the second hub wall section 20 together form another double S-curve 31, 32 on both sides of the piston pin bore 12. The first hub wall section 19 and the second hub wall section 20 therefore each have convex regions Bl (Fig. 9) and concave regions B2 (Fig. 9), with the convex regions Bl bordering the piston pin bore 12.

[0122] Kolbenschmidt Pistons Germany GmbH 21 and the concave areas B2 are arranged outside the convex areas B1 with respect to the bolt bore axis 13 and adjoin the convex areas Bl. The first box wall section 16 adjoins the concave areas B2 of the first hub wall section 19, while the second box wall section 17 adjoins the concave areas B2 of the second hub wall section 20. In other words, the first hub wall section 19 projects beyond the first box wall section 16, and the second hub wall section 20 projects beyond the second box wall section 17. Thus, the first hub wall section 19 and the second hub wall section 20 are arranged radially outward, i.e., away from the piston stroke axis 9, with respect to the first box wall section 16 and the second box wall section 17, respectively.

[0123] However, it is also possible that within the bolt section plane 27, the first hub wall section 19 and the second hub wall section 20 each form straight lines and are oriented, for example, parallel to the x-direction x. In other words, it is conceivable that the first box wall section 16 transitions flush into the first hub wall section 19 and the second box wall section 17 transitions flush into the second hub wall section 20. Finally, it is also conceivable that the first hub wall section 19 can be recessed behind the first box wall section 16 and the second hub wall section 20 behind the second box wall section 17, i.e., that the first hub wall section 19 and the second hub wall section 20 are arranged radially inward with respect to the first box wall section 16 and the second box wall section 17, respectively, i.e., facing the piston stroke axis 9.

[0124] The box wall sections 16 and 17 are each convex. In particular, the box wall sections 16 and 17 are exclusively convex. Consequently, the box wall sections 16 and 17 form a plane within the bolt section plane RKS24003PWO APQ24001 WO

[0125] Kolbenschmidt Pistons Germany GmbH

[0126] 22

[0127] 27 represents an arc line circumscribing the piston stroke axis 9, the ends of which point towards the piston stroke axis 9 and whose arc points radially outwards, i.e. away from the piston stroke axis 9.

[0128] Here, connecting lines 33, 34, along which the first box wall section 16 is joined to the first hub wall section 19, and connecting lines 35, 36, along which the second box wall section 17 is joined to the second hub wall section 20, are inclined radially inwards. Thus, connecting lines 33, 34, 35, 36 continuously approach the piston stroke axis 9 as they get closer to the piston head 11, and their distance from each other decreases. In other words, the first box wall section 16 and the second box wall section 17 together form an undercut.

[0129] The aluminum piston 8 has a nominal piston diameter 37. The nominal piston diameter 37 is defined as the diameter of the smallest possible cylinder that includes the piston skirt, i.e., the skirt wall sections 14, 15. This cylinder is oriented perpendicular to the pin bore axis 13. The nominal piston diameter 37 is 8.5 to 14 centimeters (cm), in particular 9 to 11 centimeters (cm).

[0130] The first bore reinforcement 21 and the second bore reinforcement 22, in addition to widening downwards (i.e., opposite to the z-direction z), also extend radially outwards (i.e., away from the piston stroke axis 9). In other words, at the locations of the first bore reinforcement 21 and the second bore reinforcement 22, the piston shaft 10 is also widened or reinforced along or opposite to the y-direction y. The piston shaft 10 thus has a box wall distance 38, which is defined as the shortest distance between a first point 39 of a first section line (not shown), formed by a section of the first RKS24003PWO APQ24001 WO

[0131] Kolbenschmidt Pistons Germany GmbH 23

[0132] The section view is formed by a section of the second box wall section 17 or a second bore reinforcement 21 with a plane (not shown) spanned by the piston stroke axis 9 and the bolt bore axis 13 (see Fig. 4). The section view according to Fig. 4 lies within the plane mentioned above. Here, the first point 39 is the point of the first section line furthest from the piston stroke axis 9, and the second point 40 is the point of the second section line furthest from the piston stroke axis 9.In other words, the cylinder wall distance 38 corresponds to the distance that would be measured if the piston skirt 10 were measured radially outwards on both sides along the pin bore axis 13 within the previously mentioned plane. The ratio of the cylinder wall distance 38 to the nominal piston diameter 37 is 0.8 to 0.95, in particular 0.81 to 0.91.

[0133] Furthermore, the piston skirt 10 has a hub distance 41, which is defined as the shortest distance between a third point 42 of a section line formed by a section of the first hub wall section 19 with the bolt section plane 27, which is furthest from the piston stroke axis 9, and a fourth point 43 of another section line formed by a further section of the second hub wall section 20 with the bolt section plane 27, which is furthest from the piston stroke axis 9 (see Fig. 6). In other words, the hub distance 41 corresponds to the distance that would be measured if the piston skirt 10 were measured radially outwards on both sides within the bolt section plane 27 along the bolt bore axis 13.

[0134] Finally, the piston shaft 10 has a first shaft width 44 (Fig. 7) of the first shaft wall section 14. The first shaft width 44 is defined as RKS24003PWO APQ24001 WO

[0135] Kolbenschmidt Pistons Germany GmbH 24 the shortest distance between a fifth point 45, which is formed by a section of the first outer edge 23 and the bolt cutting plane 27, and a sixth point 46, which is formed by a section of the second outer edge 24 and the bolt cutting plane 27. Additionally, the piston shank 10 also has a second shank width 47 of the second shank wall section 15 (Fig. 8). The second shank width 47 is defined as the shortest distance between a seventh point 48, which is formed by a section of the third outer edge 25 and the bolt cutting plane 27, and an eighth point 49, which is formed by a section of the fourth outer edge 26 and the bolt cutting plane 27. The first shank width 44 can be smaller, larger, or equal to the second shank width 47.Furthermore, the ratio of the first shaft width 44 of the first shaft wall section 14 and / or the second shaft width 47 of the second shaft wall section 15 to the nominal piston diameter 37 is 0.5 to 0.7, in particular 0.55 to 0.65.

[0136] Furthermore, the aluminum piston 8 has a piston mass m (not shown), where the ratio of the magnitude of the piston mass m of the aluminum piston 8, given in grams (g), to the cube of the magnitude of the nominal piston diameter 37, given in centimeters (cm), is 0.7 to 0.95, in particular 0.77 to 0.86. In other words, there is a relationship between the nominal piston diameter [DK] 37, given in centimeters (cm), the piston mass [MK] m, given in grams (g), and a scalar factor [F] according to MK = DK. 3 * F * gjcm 3, where the factor [F] lies between 0.7 and 0.95, in particular between 0.77 and 0.86. The design of the hub wall sections 19, 20 and the box wall sections 16, 17 serves to reduce the piston mass m as well as a reduction of the frictional force acting on the aluminum piston 8 during operation of the internal combustion engine 7. The choice of piston mass m represents a particularly favorable compromise for maintaining strength against mechanical and / or thermal loads in RKS24003PWO APQ24001 WO

[0137] Kolbenschmidt Pistons Germany GmbH 25 an application of the aluminium piston 8 in the internal combustion engine 7 as well as a targeted lightweight design to reduce the fuel requirement of the internal combustion engine 7.

[0138] The aluminum piston 8 has a cooling channel 50 that completely surrounds the piston stroke axis 9 and is preferably rotationally symmetrical to it. The cooling channel 50 is particularly torus-shaped. A cooling oil, in particular engine oil, can be guided through the cooling channel 50 to dissipate heat generated in the aluminum piston 8 during operation. For this purpose, the cooling oil can be injected into the cooling channel 50 by means of an injection nozzle arranged below the aluminum piston 8 in the orientation shown in Figures 2 to 5 and 7 to 9. The cooling channel 50 can, for example, be incorporated into the aluminum piston 8 during its manufacture using a purgeable salt core. Alternatively, the cooling channel 50 can also be incorporated into the aluminum piston 8 during the assembly of the aforementioned sub-components.

[0139] The cooling channel 50 can be in fluid communication with the interior 18 by means of several bores (not shown). The number of bores is generally arbitrary. Preferably, several bores are provided, which can be arranged evenly distributed around the piston stroke axis 9. The bores can also be arranged unevenly distributed around the piston stroke axis 9. For example, when the aluminum piston 8 is operating in the orientation shown in Figures 2 to 5 and 7 to 9, cooling oil can be injected into the interior 18 from below using the aforementioned injection nozzle. At least some of the cooling oil passes through the bores into the cooling channel 50 and back out again. The cooling oil then conducts heat away from the aluminum piston 8. RKS24003PWO APQ24001 WO

[0140] Kolbenschmidt Pistons Germany GmbH 26

[0141] The piston head 11 has a piston crown 51, which faces a cylinder head of the internal combustion engine 7. A large portion of the heat is also transferred to the piston crown 51. The piston crown 51 is specifically oriented towards a combustion chamber 52 of the internal combustion engine 7. The piston crown 51 comprises an annular piston crown section 53, which spans a plane 54 oriented perpendicular to the piston stroke axis 9.

[0142] Furthermore, the piston crown 51 has a combustion chamber recess 55, which is recessed relative to the piston crown section 53. Viewed along the piston stroke axis 9, or along the z-direction z, the combustion chamber recess 55 is thus offset or recessed relative to the piston crown section 53. In the orientation of Figures 4 and 5, the combustion chamber recess 55 is bounded upwards by the plane 54. Viewed along the piston stroke axis 9, the combustion chamber recess 55 extends at least to the level of the cooling channel 50.

[0143] The combustion chamber bowl 55 has a combustion chamber bowl surface 56, which can have any geometry. The combustion chamber bowl surface 56 is rotationally symmetrical about the piston stroke axis 9. In cross-section, the combustion chamber bowl surface 56 essentially has a W-shaped geometry with a central section 57 extending obliquely downwards from the piston stroke axis 9 in the opposite direction z, a first wall section 58 adjoining the central section 57 in the form of an arc or circular arc section opening in the z direction, and a second wall section 59 adjoining the first wall section 58 and extending obliquely upwards along the z direction z. The second wall section 59 terminates at the plane 54.

[0144] The combustion chamber bowl surface 56 widens continuously from the central section 57 along the z-direction. This means, in particular, that the diameter of the combustion chamber bowl 55, starting from the RKS24003PWO APQ24001 WO

[0145] Kolbenschmidt Pistons Germany GmbH

[0146] 27

[0147] The central section 57 increases in size along the z-direction towards the plane 54. Therefore, no cross-sectional constrictions, undercuts, steps, or the like are provided on the combustion chamber bowl surface 56. The combustion chamber bowl surface 56 is thus edgeless. In particular, the central section 57 and the wall sections 58 and 59 transition seamlessly into one another with rounded edges.

[0148] The combustion chamber cavity 55 is open at the top in the orientation shown in Figures 4 and 5. The combustion chamber cavity 55 has a combustion chamber cavity volume 60. The combustion chamber cavity volume 60 is defined as a volume enclosed or enclosed by the combustion chamber cavity surface 56 and the plane 54. The combustion chamber cavity volume 60 can be determined or calculated, for example, using a CAD (Computer Aided Design) model of the combustion chamber cavity 55.

[0149] In the simplest case, to determine the combustion chamber bowl volume 60, the combustion chamber bowl 55 can be filled with water up to the level 54 or up to the piston head section 53, and the water taken up in the combustion chamber bowl 55 can be poured into a measuring cup in order to determine the combustion chamber bowl volume 60 based on the volume of water read from the measuring cup.

[0150] A wall 61 separates the combustion chamber bowl 55 from the interior 18. On its front side, the wall 61 forms part of the combustion chamber bowl surface 56. On its rear side, i.e., facing the interior 18, the wall 61 forms a so-called inner shape 62 of the aluminum piston 8. The inner shape 62 can be conical or cone-shaped.

[0151] Furthermore, the aluminum piston 8 has a compression height of 63. The compression height 63 is defined as a distance between the pin bore axis RKS24003PWO APQ24001 WO

[0152] Kolbenschmidt Pistons Germany GmbH

[0153] 28

[0154] 13 and an upper edge of the aluminium piston 8, namely the plane 54 or the piston base section 53.

[0155] The piston head 11 has a ring section or ring field 64. The ring field 64 forms, in particular, a substantially cylindrical outer surface of the piston head 11, which can be rotationally symmetrical about the piston stroke axis 9. The ring field 64 has several annular grooves 65 arranged one above the other along the z-direction z, of which only one is labeled in Figures 4 and 5. The annular grooves 65 are suitable for receiving piston rings. For example, two or three such annular grooves 65 are provided.

[0156] Furthermore, the ring field 64 can also have a ring carrier 66. The ring carrier 66 rotates completely around the piston stroke axis 9. In cross-section, the ring carrier 66 can be U-shaped. The ring carrier 66 can accommodate or support a piston ring as previously mentioned. The ring carrier 66 can be made of a different material than the piston head 11 or the aluminum piston 8. For example, the ring carrier 66 can be made of a steel alloy, whereas the aluminum piston 8 can be made of an aluminum alloy. In this case, the ring carrier 66 can be an insert onto which the aluminum piston 8 is cast.

[0157] A fire land 67 adjoining the piston crown section 53 is part of the ring field 64. However, the fire land 67 does not have a ring groove 65 for receiving a piston ring, as mentioned previously. The fire land 67 terminates along the z-direction z at the piston crown section 53 or at the plane 54.

[0158] The aluminium piston 8 has several valve pockets 68, of which in the

[0159] Figures 2, 4, and 5 each show only one figure with a reference numeral. In RKS24003PWO APQ24001 WO

[0160] Kolbenschmidt Pistons Germany GmbH

[0161] 29

[0162] Valve pockets 68 engage the valve tappets 7 during operation of the internal combustion engine. The valve pockets 68 can be evenly distributed around the piston stroke axis 9. However, this is not mandatory. The number of valve pockets 68 preferably corresponds to the number of valves per aluminum piston 8. For example, four valve pockets 68 are provided.

[0163] The valve pockets 68 are preferably provided on the fire bridge 67. The valve pockets 68 do not penetrate the fire bridge 67 along the radial direction R of the aluminum piston 8. The valve pockets 68 are preferably circular or cross-sectional.

[0164] Each valve pocket 68 has a valve pocket volume, the valve pocket volumes of the valve pockets 68 being part of the combustion chamber bowl volume 60.

[0165] The combined volume of all valve pockets 68 can be defined as the volume difference between a piston blank, which is identical in structure to the aluminum piston 8 except for the valve pockets 68 and which does not yet have any valve pockets 68, and the aluminum piston 8 itself, which already has the valve pockets 68. The valve pockets 68 can be milled into the piston blank or formed on a mold that can be used to manufacture the piston blank.

[0166] The aluminum piston 8 further features an oil nozzle recess 69 (Figs. 3, 7 and 9). The oil nozzle recess 69 is located at one end of the shaft wall section 14 opposite the z-direction, in particular at one end of the outer edge 23 opposite the z-direction. In other words, the oil nozzle recess 69 is located at a transition between the shaft wall section 14 and the cylinder wall section 16. However, the oil nozzle recess 69 could also be located elsewhere.

[0167] Kolbenschmidt Pistons Germany GmbH

[0168] 30. In particular, the oil nozzle recess 69 can be arranged on the pressure side and / or on the counter-pressure side of the aluminum piston 8. The oil nozzle recess 69 represents a round or arc-shaped reduction. The oil nozzle recess 69 can have the form of a circular segment. The oil nozzle recess 69 provides a free space within at least one of the piston bores of the engine block of the internal combustion engine 7 for the integration of at least one oil nozzle (not shown) within the piston bores of the engine block. Furthermore, the piston mass m can also be further reduced. Although the present invention has been described with reference to exemplary embodiments, it can be modified in many ways.

[0169] RKS24003PWO APQ24001 WO

[0170] Kolbenschmidt Pistons Germany GmbH

[0171] 31

[0172] REFERENCE MARK LIST

[0173] 1 vehicle

[0174] 2 Bodywork

[0175] 3 Vehicle interior

[0176] 4 Environment

[0177] 5 wheels

[0178] 6 wheels

[0179] 7 Internal combustion engine

[0180] 8 aluminum pistons

[0181] 9 piston stroke axis

[0182] 10 Piston shaft

[0183] 11 Piston head

[0184] 12 piston pin bore

[0185] 13 bolt hole axis

[0186] 14 shaft wall section

[0187] 15 shaft wall section

[0188] 16 Box wall section

[0189] 17 Box wall section

[0190] 18 Interior

[0191] 19 Hub wall section

[0192] 20 Hub wall section

[0193] 21. Bore reinforcement

[0194] 22. Bore reinforcement

[0195] 23 Outer edge

[0196] 24 outer edge

[0197] 25 outer edge

[0198] 26 outer edge

[0199] 27 Bolt section plane

[0200] 28 bolt bore diameter RKS24003PWO APQ24001 WO

[0201] Kolbenschmidt Pistons Germany GmbH

[0202] 32

[0203] 29 Double 'S-curve

[0204] 30 Double 'S-curve

[0205] 31 Double 'S-curve

[0206] 32 Double S-curve

[0207] 33 connecting line

[0208] 34 connecting line

[0209] 35 connecting line

[0210] 36 connecting line

[0211] 37 piston diameter

[0212] 38 Box wall spacing

[0213] 39 points

[0214] 40 points

[0215] 41 Hub spacing

[0216] 42 points

[0217] 43 points

[0218] 44 shaft width

[0219] 45 points

[0220] 46 points

[0221] 47 shaft width

[0222] 48 points

[0223] 49 points

[0224] 50 Cooling channel

[0225] 51 Piston crown

[0226] 52 Combustion chamber

[0227] 53 Piston crown section

[0228] Level 54

[0229] 55 Combustion chamber recess

[0230] 56 Combustion chamber bowl surface

[0231] 57 Middle section

[0232] 58 Wan dab cut RKS24003PWO APQ24001 WO

[0233] Kolbenschmidt Pistons Germany GmbH

[0234] 33

[0235] 59 Wan dab cut

[0236] 60 combustion chamber volume

[0237] 61 wall

[0238] 62 Inner shape

[0239] 63 Compression height

[0240] 64 Ring field

[0241] 65 Ring groove

[0242] 66 ring bearers

[0243] 67 Fire Bridge

[0244] 68 Valve pocket

[0245] 69 Oil nozzle recess

[0246] B1 area

[0247] B2 area m piston mass

[0248] R radial direction x x- direction yy direction z z- direction

Claims

RKS24003PWO APQ24001 WO Kolbenschmidt Pistons Germany GmbH 34 PATENT CLAIMS 1. Aluminium piston (8) for an internal combustion engine (7), comprising a piston head (11) and a piston skirt (10) connected to the piston head (11), wherein the aluminium piston (8) has a nominal piston diameter (37), wherein the nominal piston diameter (37) is 8.5 cm to 14 cm, and wherein the ratio of the magnitude of a piston mass (m) of the aluminium piston (8) expressed in grams to the third power of the magnitude of the nominal piston diameter (37) expressed in centimeters is 0.7 to 0.

95.

2. Aluminium piston according to claim 1, characterized in that the nominal piston diameter (37) is 9 cm to 11 cm.

3. Aluminium piston according to claim 1 or 2, characterized in that the ratio of the amount of the piston mass (m) of the aluminium piston (8) specified in grams to the third power of the amount of the nominal piston diameter (37) specified in centimeters is 0.77 to 0.

86.

4. Aluminium piston according to one of claims 1-3, characterized in that the piston shaft (10) has a first shaft wall section (14), a second shaft wall section (15) opposite the first shaft wall section (14), a first box wall section (16) and a second box wall section (17) opposite the first box wall section (16), wherein the first box wall section (16) and the second box wall section RKS24003PWO APQ24001 WO Kolbenschmidt Pistons Germany GmbH 35 (17) connect the first shaft wall section (14) with the second shaft wall section (15).

5. Aluminium piston according to claim 4, characterized in that the ratio of a first shaft width (44) of the first shaft wall section (14) and / or a second shaft width (47) of the second shaft wall section (15) to the nominal piston diameter (37) is 0.5 to 0.7, in particular 0.55 to 0.

65.

6. Aluminium piston according to claim 4 or 5, characterized in that the ratio of a box wall distance (38) between the first box wall section (16) and the second box wall section (17) to the nominal piston diameter (37) is 0.8 to 0.95, in particular 0.81 to 0.

91.

7. Aluminium piston according to one of claims 4 - 6, characterized in that the piston stem (10) has a first hub wall section (19) which is at least partially enclosed by the first box wall section (16), and a second hub wall section (20) which is at least partially enclosed by the second box wall section (17), wherein a piston pin bore (12) extends through the first hub wall section (19) and the second hub wall section (20), wherein the first hub wall section (19) is set back behind, projects beyond, or is flush with the first box wall section (16), and wherein the second hub wall section (20) is set back behind, projects beyond, or is flush with the second box wall section (17).

8. Aluminum piston according to claim 7, RKS24003PWO APQ24001 WO Kolbenschmidt Pistons Germany GmbH 36 characterized in that the first hub wall section (19) and the second hub wall section (20) each have convex areas (Bl) and concave areas (B2), wherein the convex areas (Bl) adjoin the piston pin bore (12) and the concave areas (B2) are arranged outside the convex areas (B1) with respect to the piston pin bore (12) and adjoin the convex areas (B2), wherein in particular the first box wall section (16) adjoins the concave areas (B2) of the first hub wall section (19), while the second box wall section (17) adjoins the concave areas (B2) of the second hub wall section (20).

9. Aluminium piston according to claim 8, characterized in that the first box wall section (16) and the second box wall section (17) are convexly shaped, wherein the first box wall section (16) and the second box wall section (17) form an arc line circumferentially around a piston stroke axis (9), in particular within a bolt section plane (27), wherein the piston head (11) is shaped circumferentially around the piston stroke axis (9) and the bolt section plane (27) is arranged perpendicular to the piston stroke axis (9) and intersects the piston pin bore (12).

10. Aluminium piston according to claim 9, characterized in that connecting lines (33 - 36), along which the first box wall section (16) is joined to the first hub wall section (19) or the second box wall section (17) is joined to the second hub wall section (20), are inclined radially inwards, i.e. continuously approaching the piston stroke axis (9) as they get closer to the piston head (11).

11. Aluminium piston according to claim 9 or 10, RKS24003PWO APQ24001 WO Kolbenschmidt Pistons Germany GmbH 37 characterized in that within the bolt section plane (27) the first hub wall section (19) and the first box wall section (16) together form a double S-curve (29, 30) on both sides of the piston pin bore (12), wherein within the bolt section plane (27) the second hub wall section (20) and the second box wall section (17) together form, in particular, a further double S-curve (31, 32) on both sides of the piston pin bore (12).

12. Aluminium piston according to claims 9 - 11, characterized in that the first box wall section (16) has a first bore reinforcement (21) and the second box wall section (17) has a second bore reinforcement (22), wherein the bore reinforcements (21, 22) reinforce cross-sectional areas of the first box wall section (16) and cross-sectional areas of the second box wall section (17) both along the piston stroke axis (9) and radially outwards.

13. Aluminium piston according to claims 7 - 12, characterized in that the first box wall section (16) and the second box wall section (17) together form an undercut.

14. Aluminium piston according to one of claims 4 - 13, characterized in that outer edges (23, 24) of the first box wall section (16) and outer edges (25, 26) of the second box wall section (17) each run along a straight line, wherein all outer edges (23, 24, 25, 26) in particular run parallel to each other.

15. Aluminium piston according to one of claims 4 - 14, RKS24003PWO APQ24001 WO Kolbenschmidt Pistons Germany GmbH 38 characterized in that the widths of a development of the first shaft wall section (14) and a development of the second shaft wall section (15) decrease continuously distal to the piston head (11).

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