Piston and internal combustion engine system

Abstract

The present disclosure relates to a piston (3) for an internal combustion engine ICE, said piston extending in an axial direction (A) and a radial direction (R) and having an axial tip (16) comprising a piston bowl (6) intended to form part of a combustion chamber, the piston bowl has an axial bottom plate portion (11) with a bottom plate surface (11a), a circumferential rim portion (20) extending in the axial direction (A) between the bottom plate surface and a top end surface (5) of the axial top end, the piston bowl further having an axial depth (H) defined by an axial distance between the bottom plate surface and the top end surface, the piston bowl further includes a plurality of spaced apart projections (40) circumferentially distributed around the circumferential rim portion (20), each of the spaced apart projections having opposing radial side sections (41, 42) and further having a flat surface (43, 43a) or a concave surface (43, 43b) extending between the opposing radial side sections. The disclosure also relates to an internal combustion engine system.

Description

Technical Field

[0001] The present disclosure relates to a piston for an internal combustion engine. The present disclosure also relates to an internal combustion engine system for a vehicle, wherein the internal combustion engine includes a piston. The present disclosure is applicable to vehicles, in particular heavy vehicles, such as, for example, trucks. However, although the present disclosure will be described primarily with respect to trucks, the internal combustion engine system may also be applicable to other types of vehicles propelled by an internal combustion engine. In particular, the present disclosure may be applied to heavy vehicles, such as trucks, buses, and construction equipment, but may also be applied to cars and other light vehicles, etc. In addition, the internal combustion engine is typically a diesel internal combustion engine, but other fuels, such as hydrogen and natural gas, may also be used in combination with the piston. The present disclosure may also be applied to other machines, such as generators and construction equipment. The present disclosure may also be applied to marine vessels, etc. Background Art

[0002] In the field of internal combustion engine devices, many efforts are made to achieve efficient combustion which is also satisfactory with regard to residual products, in particular soot particles and NOx emissions, but naturally also carbon monoxide emissions from diesel fuels and hydrocarbon emissions can be taken into account.

[0003] The combustion process in which, for example, diesel fuel is injected directly into the cylinder and ignited by the increased temperature and pressure in the cylinder is generally referred to as a compression ignition combustion process. Another type of ignition process for some gaseous fuels is a spark ignition combustion process. When the fuel is ignited in the cylinder, the combustion gases present in the cylinder mix turbulently with the burning fuel, so that a diffusion flame controlled by the mixture is formed. The combustion of the fuel / gas mixture in the cylinder causes heat generation, which causes the gas in the cylinder to expand. The expansion of the gas then causes the piston to move in the cylinder. Depending on several parameters, such as the type of fuel, the injection pressure of the fuel, the amount of exhaust gas recirculated to the cylinder, the injection time of the fuel and the turbulence present in the cylinder, different engine efficiency and emission values ​​are obtained.

[0004] In order to control and in particular to reduce emissions from the combustion process in a combustion engine, it has been proposed to utilize the shape of the piston bowl surface facing the combustion chamber. The piston bowl surface is the portion of the piston crown of a reciprocating piston in a cylinder. To this end, the piston bowl surface can be designed to influence various parameters in the combustion chamber, such as flame propagation, mixing energy, kinetic energy distribution and / or swirl.

[0005] It has also been observed that the shape of the piston bowl may affect the combustion and / or mixing of fuel within the cylinder in other types of internal combustion engines, such as gaseous fuel engines, for example, hydrogen internal combustion engines.

[0006] WO 2017 / 108103 A1 discloses an example of a piston crown of a piston, wherein the piston crown comprises a piston bowl surface having a plurality of circumferentially spaced protrusions in a circumferential rim portion.

[0007] Despite activity in this area, there is a desire to further improve pistons of this type for use in internal combustion engine (ICE) systems for heavy vehicles. Summary of the invention

[0008] The object of the present disclosure is to provide an enhanced piston design for a reciprocating piston intended to operate in an internal combustion engine system. This object is achieved at least in part by a piston according to claim 1. This object is also achieved at least in part by a piston according to claim 18. This object is also achieved at least in part by other independent claims. Dependent claims relate to advantageous embodiments.

[0009] According to a first aspect of the present disclosure, a piston for an internal combustion engine (ICE) is provided. The piston extends in an axial direction and in a radial direction. The piston has an axial top end including a piston bowl intended to form a portion of a combustion chamber. The piston bowl has an axial bottom plate portion with a bottom plate surface, a circumferential edge portion extending in an axial direction between the bottom plate surface and the top end surface of the axial top end. The piston bowl also has an axial depth defined by an axial distance between the bottom plate surface and the top end surface. In addition, the piston bowl includes a plurality of spaced protrusions distributed circumferentially around the circumferential edge portion. Each of the spaced protrusions extends a considerable portion in a radial direction toward a central axis, and also extends a considerable portion in an axial direction from the bottom plate surface toward the top end surface, and each of the spaced protrusions has opposite radial side segments. In addition, each of the spaced protrusions includes a flat surface or a concave surface extending between the opposite radial side segments. The flat surface or concave surface has a first circumferential extension at the intersection between the flat surface or concave surface and the bottom plate surface, and also has a second circumferential extension at an axial distance from the bottom plate surface that is one quarter of the axial depth of the piston bowl. In addition, a ratio between the second circumferential extension and the first circumferential extension is 0.4 or less.

[0010] Hence, the first circumferential extension is greater than the second circumferential extension.

[0011] Here, the proposed piston provides an improved design of a protrusion at the lower region of the piston bowl, which then generally intersects with the dome portion of the piston bowl.

[0012] The present disclosure is based, at least in part, on the insight that it is a challenge to simultaneously achieve reductions in fuel consumption and emissions without sacrificing the durability of the piston. For example, some dimensions of a protrusion contribute to good combustion performance, while other dimensions may directly affect the durability of the piston. That is, when a protrusion is used on a piston bowl of a piston intended for a diesel ICE system, stress concentrations are also typically introduced on or in the piston. In this context, it has been observed that the lower region of the protrusion, i.e., the region proximate the floor portion of the piston bowl, is one of many regions where the impact on combustion performance is relatively low but the impact on durability is relatively high.

[0013] Therefore, the proposed piston aims to improve the protrusion of the piston bowl of the piston to provide sufficiently reliable durability in terms of fatigue life without compromising any function related to the protrusion and the combustion of fuel in the combustion chamber of the cylinder.

[0014] By having a protrusion arrangement, the design of the piston helps to enhance the combustion process of fuels (such as diesel fuel), and / or for other types of fuels (such as hydrogen fuel), helps to enhance the mixing of air and fuel. The protrusion can also provide an abrupt change in the side profile of the protrusion to achieve a well-defined flow release position.

[0015] Furthermore, by making the protrusion comprise a flat surface or a concave surface extending between opposite radial side segments, in combination with an arrangement in which the ratio between the second circumferential extension and the first circumferential extension is 0.4 or less, the proposed piston provides a design in which the protrusion is less sensitive in terms of required fatigue life and required durability. In this way, the piston can better withstand critical fatigue conditions occurring during ordinary use of the piston in heavy vehicles.

[0016] More specifically, through the above configuration of the protrusion, the portion of the protrusion in which the influence on the combustion performance is low is designed to minimize the compressive stress (i.e., the compressive stress in the radial direction) in the lower region of the protrusion toward the dome (the center of the piston) for the temperature load, while separating the position of the maximum compressive stress due to the temperature load from the position of the maximum tensile stress due to the pressure load. The piston bowl having the protrusion in which the maximum stress areas are separated from each other helps to increase the fatigue life of the protrusion and the piston.

[0017] The proposed protrusions are generally provided to enhance the interaction of the fuel flame with the surface forming the piston bowl and the adjacent flame. However, while the proposed piston can be incorporated into a variety of different types of ICE systems, the proposed piston can be particularly suitable for ICE systems that are fueled by high pressure injection of fuels containing liquid diesel or pressure injection of gaseous fuels (such as hydrogen fuel), where the fuel injection duration occurs near top dead center (TDC). In hydrogen ICE systems, the proposed piston design with the above-mentioned protrusion segmentation can improve the mixing of hydrogen with compressed air before the ignition event.

[0018] The protrusions may be provided in several different geometries, shapes and disposed at various locations along the side segments. For example, the ratio between the sum of the first circumferential extension of all spaced protrusions along the circumferential edge portion and the circumferential extension of the circumferential edge portion may be at least 30%, preferably at least 45%, and most preferably at least 60%. Such an arrangement of the protrusions relative to the circumferential extension will also improve the properties of the piston design in terms of desired durability, etc.

[0019] A first radial side segment of the opposing radial side segments may intersect with the flat surface or the concave surface along an intersection edge. Similarly, a second radial side segment of the opposing radial side segments may intersect with the flat surface or the concave surface along another opposing intersection edge.

[0020] The intersecting edge in combination with the first circumferential extension and the second circumferential extension may define an extension of a flat surface or a concave surface.

[0021] Each of the intersecting edges may be inclined from the first circumferential extension to the second circumferential extension in a linear manner or in a non-linear manner (such as in a curved manner). Typically, the intersecting edges may be inclined towards a central area located on the second circumferential extension. For example, the intersecting edges may be inclined from the first circumferential extension to the second circumferential extension in a curved manner, as can be seen in the circumferential direction and in the radial direction.

[0022] The intersecting edges in conjunction with the first circumferential extension and the second circumferential extension may define a surface shaped like a trapezoid or triangle.Such a shape may also improve the properties of the protrusion in terms of required durability.

[0023] The concave surface extending substantially in the circumferential direction helps to improve the configuration of the protrusion. The concave surface of the protrusion may generally be the surface of the protrusion arranged to face the axial center of the piston bowl. Generally, although not strictly required, the radius of curvature of the concave surface may always be substantially perpendicular to the axial center of the piston bowl.

[0024] The extension of the flat surface or concave surface from the first circumferential extension to the second circumferential extension may further include an axially extending concave region.

[0025] One advantage of having a concave surface in the axial direction is that the protrusion portion that intersects the floor surface provides a smooth transition between the protrusion and the floor portion.

[0026] The extension of the flat surface extending from the first circumferential direction to the second circumferential direction may be defined by a flat surface profile. That is, in the axial direction, the flat surface extending from the first circumferential direction to the second circumferential direction may be defined by a flat surface profile.

[0027] The radial side segments may generally be curved convex side segments respectively.Each of the opposing radial side segments may comprise a plurality of different convexly curved contour areas.

[0028] The radial side segment may generally extend in a radial direction. Thus, the radial side segment is a radially extending side segment. The radial side segment may generally extend from a circumferential edge portion. The radial side segment may generally extend from a circumferential edge portion toward a central axis. The radial side segment may also generally extend substantially in an axial direction.

[0029] The spaced apart protrusions may be evenly distributed circumferentially along the circumferential edge portion.

[0030] The spaced apart protrusions may be non-uniformly distributed circumferentially along the circumferential edge portion.

[0031] Each of the spaced protrusions may extend in an axial direction from the bottom plate surface to the top surface of the piston top. In another example, each of the spaced protrusions may extend in an axial direction from the bottom plate surface to a second circumferential extension. As mentioned above, the second circumferential extension is axially located at a certain axial distance from the bottom plate surface. The axial distance is one quarter of the depth of the piston bowl. In other examples, each of the spaced protrusions may extend in an axial direction from the bottom plate surface to a given intermediate axial distance greater than one quarter of the depth of the piston bowl but less than the depth of the piston bowl. In other words, each of the spaced protrusions may extend in an axial direction from the bottom plate surface to a distance in an axial direction between one quarter of the depth of the piston bowl but less than the depth of the piston bowl.

[0032] Additionally or alternatively, the flat surface or concave surface may extend in an axial direction from an intersection between the flat surface or concave surface and the bottom plate surface toward a top end surface of the piston top end.

[0033] In some examples, the flat surface or concave surface can extend in an axial direction from the intersection between the flat surface or concave surface and the bottom plate surface to the top surface of the piston top. In another example, the flat surface or concave surface can extend in an axial direction from the bottom plate surface to a second circumferential extension. For example, the flat surface or concave surface extends in an axial direction from the intersection between the flat surface or concave surface and the bottom plate surface to a second circumferential extension.

[0034] As mentioned above, the second circumferential extension is axially located at a certain axial distance from the bottom plate surface. The axial distance is one quarter of the depth of the piston bowl. In other examples, the flat surface or concave surface can extend in the axial direction from the bottom plate surface to a given intermediate axial distance greater than one quarter of the depth of the piston bowl but less than the depth of the piston bowl. In other words, the flat surface or concave surface can extend in the axial direction from the bottom plate surface to a distance between one quarter of the depth of the piston bowl but less than the depth of the piston bowl in the axial direction.

[0035] Each of the spaced apart protrusions may extend at least partially in a radial direction above the floor portion.

[0036] The first circumferential extension may generally be the maximum circumferential extension of the extension of the flat surface or the concave surface, as measured along the circumferential direction. The first circumferential extension is therefore the maximum circumferential extension of the flat surface or the concave surface. Therefore, the first circumferential extension may generally be referred to as the first maximum circumferential extension. One advantage of having a protrusion having its maximum circumferential extension at the lowermost part (close to the floor surface of the piston bowl design) is that tensile stresses in the radial direction may be reduced compared to hitherto known designs of piston bowl protrusions. In other words, a wider circumferential extension of the flat surface or the concave surface at the intersection with the floor surface may generally contribute to reducing the level of tensile stresses in the radial direction.

[0037] Each of the protrusions may extend a substantial portion in the axial direction from the bottom plate surface to the piston top end surface.

[0038] The flat or concave surface may generally extend in a circumferential direction between the opposing radially extending side segments.

[0039] According to a second aspect of the present disclosure, a piston for an internal combustion engine (ICE) is provided, the piston extending in an axial direction and in a radial direction and having an axial top end including a piston bowl intended to form a portion of a combustion chamber. The piston bowl has an axial bottom plate portion with a bottom plate surface, a circumferential edge portion extending in an axial direction between the bottom plate surface and the top end surface of the axial top end. The piston bowl also has an axial depth defined by an axial distance between the bottom plate surface and the top end surface. The piston bowl also includes a plurality of spaced-apart protrusions distributed circumferentially around the circumferential edge portion, each of the spaced-apart protrusions extending a considerable portion in a radial direction toward a central axis, and also extending a considerable portion in an axial direction from the bottom plate surface toward the top end surface. Each of the spaced-apart protrusions has opposite radial side segments, and also has a flat surface or a concave surface extending between the opposite radial side segments. The flat surface or the concave surface has a first circumferential extension at the intersection between the flat surface or the concave surface and the bottom plate surface. Furthermore, the ratio between the sum of the first circumferential extension of all spaced-apart protrusions along the circumferential rim portion and the circumferential extension of the circumferential rim portion is at least 30%, preferably at least 45% and most preferably at least 60%.

[0040] The effects and features of this second aspect of the disclosure are largely similar to those described above in conjunction with the first aspect of the disclosure. The embodiments mentioned in relation to the first aspect of the disclosure are largely compatible with the second aspect of the disclosure.

[0041] According to a third aspect of the present disclosure, an internal combustion engine (ICE) system is provided, the ICE system comprising an internal combustion engine for combustion of a fuel and having a combustion chamber at least partially defined by a cylinder and a reciprocating piston according to any one of the first and second aspects. The reciprocating piston is movable within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), wherein the piston top is arranged to form a portion of the combustion chamber.

[0042] The effects and features of the third aspect of the present disclosure are largely similar to those described above in conjunction with the first and second aspects of the present disclosure. The embodiments mentioned with respect to the third aspect of the present disclosure are largely compatible with the first and second aspects of the present disclosure.

[0043] Although the present disclosure can be used in any type of ICE system including the proposed piston, the present disclosure is particularly useful for diesel internal combustion systems. Therefore, according to at least one embodiment, the ICE system is a diesel ICE system. However, the proposed piston can also be used in a hydrogen ICE system. Therefore, according to at least one embodiment, the ICE system is a hydrogen ICE system.

[0044] According to a fourth aspect of the present disclosure, a vehicle is provided, the vehicle comprising a piston according to any one of the first and second aspects and / or an internal engine combustion system according to the third aspect. Therefore, the vehicle comprises a piston according to the first aspect of the present disclosure. Additionally or alternatively, the vehicle comprises a piston according to the second aspect of the present disclosure. Additionally or alternatively, the vehicle comprises an internal combustion engine system according to the third aspect of the present disclosure.

[0045] The effects and features of the fourth aspect of the present disclosure are largely similar to those described above in conjunction with the first, second and third aspects of the present disclosure. The embodiments mentioned in relation to the fourth aspect of the present disclosure are largely compatible with the first, second and third aspects of the present disclosure.

[0046] Further advantages and advantageous features of the present disclosure are disclosed in the following description and in the dependent claims.It will also be readily understood that different features can be combined to create embodiments other than those described below, without departing from the scope of the present disclosure.

[0047] The terms used herein are only used for the purpose of describing specific examples and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" also include the plural forms. It should also be understood that when used herein, the terms "comprises, comprising, includes and / or including" indicate the presence of the features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0048] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It should also be understood that, unless otherwise clearly defined herein, the terms used herein should be interpreted as meanings consistent with their meanings in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The foregoing, as well as additional objects, features and advantages of the present disclosure, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present disclosure, in which:

[0050] Figure 1 is a side view of a vehicle including an internal combustion engine (ICE) system according to an example embodiment of the present disclosure;

[0051] Figure 2is a side view of a cylinder and a reciprocating piston of an ICE system according to an example embodiment of the present disclosure;

[0052] FIG. 3A to FIG. 3E The present invention is conceptually shown Figure 2 An example embodiment of a piston design for an ICE system in;

[0053] FIG. 4A to FIG. 4C conceptually illustrates another example embodiment of a piston design for an ICE system according to the present disclosure;

[0054] FIG. 5A to FIG. 5C conceptually illustrates yet another example embodiment of a piston design for an ICE system according to the present disclosure; and

[0055] Figure 6 Yet another example embodiment of a piston design for an ICE system according to the present disclosure is conceptually illustrated. DETAILED DESCRIPTION

[0056] The present disclosure will now be described more fully below with reference to the accompanying drawings, in which exemplary embodiments of the present disclosure are shown. However, the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided for the sake of thoroughness and completeness. Throughout this specification, like reference numerals refer to like elements.

[0057] Special References Figure 1 , a vehicle 1 in the form of a truck is provided. The vehicle 1 includes an internal combustion engine (ICE) system 100 for providing power to the vehicle 1 and driving the vehicle. Figure 1 The ICE system 100 in the embodiment also includes an ICE 10. The ICE 10 is intended for the combustion of diesel fuel. However, in other examples, the ICE 10 can also be provided in the form of a hydrogen internal combustion engine (i.e., an ICE intended to burn hydrogen gaseous fuel). In particular, the ICE system 100 is a piston ICE system. The truck is here a vehicle 1 with a single propulsion system, in which the traction power is provided by the ICE system 100. However, the truck can also be a hybrid electric vehicle. For example, a hybrid electric vehicle includes a propulsion system that supports electric power with at least one high-voltage battery and at least one motor, and also includes an ICE system 100.

[0058] like Figure 1As depicted in FIG. 1 , the ICE system 100 further includes a control unit 90, also denoted herein as a controller. The controller 90 is herein a component of a main electronic control unit for controlling the vehicle and various parts of the vehicle. The controller 90 is arranged to communicate with components of the ICE system 100 (specifically, the ICE 10). For example, the controller 90 is configured to control a controllable fuel injector to spray at least one gaseous fuel jet toward the piston during a fuel injection period. The controller 90 may also be a separate part of the vehicle 1 and communicate with the main electronic control unit to control the vehicle and various parts of the vehicle.

[0059] Now turn to Figure 2 , depicting the incorporation of Figure 1 An example embodiment of an ICE system 100 in a vehicle 1 is described. Specifically, Figure 2 is a perspective cross-sectional view of a portion of an ICE according to an example embodiment of the present disclosure. Figure 2 As shown in FIG. 1 , the ICE 10 includes at least one cylinder 2. In addition, the ICE 10 has at least one combustion chamber 7 at least partially defined by the cylinder 2. In addition, the ICE 10 includes a piston 3 as disclosed herein, for example, Figure 2 and FIG. 3A to FIG. 3E About FIG. 4A to FIG. 4C , FIG. 5A to FIG. 5C and Figure 6 Description incorporated in Figure 2 1 and 100. The piston 3 is arranged and configured to reciprocate in the cylinder 2. The piston 3 is arranged to reciprocate in the cylinder 2 so that the ICE 10 is operated to combust fuel (e.g., diesel), whereby the reciprocating motion of the piston 3 in the cylinder 2 is transmitted to the rotational movement of the crankshaft 4, such as Figure 2 Therefore, the ICE system 100 includes a crankshaft 4 .

[0060] It should be noted that although Figure 2 Only a single cylinder 2 in which a combustion chamber 7 and a reciprocating piston 3 are arranged is depicted, but the ICE 10 generally includes a plurality of cylinders 2 operating to burn a fuel (e.g., diesel), whereby the reciprocating motion of the piston 3 in the cylinder 2 is transmitted to the rotational movement of the crankshaft 4. The crankshaft 4 is also coupled to a transmission (not shown) to provide torque to a drive element. In the case of a heavy vehicle (such as a truck), the drive element is a wheel; however, the ICE system 10 may also be used for other equipment, such as for construction equipment, for marine applications, as a generator, etc.

[0061] Typically, each cylinder 2 is provided with a corresponding piston 3 connected to a crankshaft 4 of the ICE 10. Figure 2 As shown in FIG. 1 , the piston 3 is arranged in the cylinder 2 for moving along the central axis A.C The piston 3 is mechanically connected to the crankshaft 4 of the ICE 10 so that the piston 3 can move between the top dead center position and the bottom dead center position in the cylinder 2. The piston 3 thus reciprocates in the cylinder 2 and is connected to the crankshaft 4 so that the piston 3 is arranged to reverse between the top dead center position and the bottom dead center position in the cylinder 2. The top dead center position is denoted as the top dead center (TDC), and the bottom dead center position is denoted as the bottom dead center (BDC), as shown in FIG. Figure 2 As indicated by the arrow in .

[0062] For example, Figure 2 and further in other figures (such as FIG. 3A to FIG. 3E ), the piston 3 extends in the axial direction A and the radial direction R. The piston 3 has a diameter smaller than the inner diameter CD of the cylinder, as shown in FIG. Figure 2 As shown. Furthermore, the piston 3 has a circumferential extension along a circumferential direction C. The piston 3 also has a longitudinal center axis Ac, which is generally indicated as the axial center axis in the following. The axial center axis Ac of the piston 3 is usually (although strictly speaking not necessarily) arranged coaxially with the axial center axis of the gas injector 13, as shown in FIG. Figure 2 However, in some examples, the axial center axis of the fuel gas injector 13 may be slightly offset from the axial center axis Ac of the piston 3 .

[0063] As used herein, the term "radial" or "radially" refers to a relative direction that is substantially perpendicular to the axial centerline of a particular component. In addition, the term "longitudinal", "longitudinally", "axially" or "axially" refers to a relative direction that is substantially parallel and / or coaxially aligned with the axial centerline of a particular component. In addition, the term "longitudinal", "longitudinally", "axially" or "axially" refers to a direction extending at least between the axial ends of a particular component, typically extending along the device or its component in the longest extension direction of the device and / or component. The terms "vertical" and "vertically" typically correspond to an axial direction. The axial direction is typically the same direction as the movement of the piston in the cylinder. In addition, the term "peripheral", "circumferential" or "circumferentially" refers to a peripheral or circumferential direction relative to an axis, which is typically a central axis extending along the longest extension direction of the device and / or component.

[0064] As used herein, the terms "upstream" and "downstream" refer to relative directions relative to the flow of a fluid in a fluid path. For example, "upstream" refers to the direction in which a fluid is flowing out, while "downstream" refers to the direction in which a fluid is flowing in. Thus, in this context, the terms upstream and downstream are generally defined relative to the flow of fuel from a fuel tank to a combustion chamber 7 of a cylinder 2, such as Figure 2 as shown in .

[0065] Similarly, terms such as “upper,” “above,” and “top,” as well as “floor,” “lower,” “bottom,” and “below,” generally refer to the relative position of parts or components with respect to the axial direction A.

[0066] Each of the cylinders 2 at least partially defines a combustion chamber 7. Each of the cylinders 2 comprises a cavity 2a defining an internal volume. One end of the cylinder cavity is closed by a cylinder head 14. Furthermore, each of the cylinders 2 has an inner circumferential side wall 29. Similarly, the cylinder head 14 has an inner surface 21. These parts together with the combustion chamber-facing part of the piston 3 generally define the combustion chamber 7. It should be noted that the cylinder head can be provided in several different shapes and is therefore not necessarily in the form of a so-called roof type, such as Figure 2 As shown in . For example, the cylinder head 14 can have a substantially flat bottom inner surface 21. Other examples of cylinder heads are also possible. In addition, the inner wall of the cylinder can be provided by a so-called cylinder liner, as is known in the art.

[0067] As in Figure 2 and further in e.g. FIG. 3A to FIG. 3E As shown in FIG. 1 , the reciprocating piston 3 comprises a piston top, which is indicated herein as the axial top end 16 of the piston 3. The piston axial top end is here the so-called piston crown. The piston axial top end 16 comprises a piston bowl 6. Thus, the piston bowl 6 is arranged at the upper axial end portion of the piston 3, as shown in FIG. Figure 2 The piston bowl 6 is arranged and intended to form part of the combustion chamber 7. Thus, the piston bowl 6 is here the part of the piston 3 that faces the combustion chamber. Figure 2 , an example is depicted of providing a piston 3 with a piston bowl 6 at its axial top end 16, wherein a surface 6a of the piston bowl 6 is arranged to define a combustion chamber 7 together with a cavity 2a of a cylinder 2. Figure 2 As depicted in , the piston bowl surface 6 a forms a combustion chamber 7 together with the inner surface 21 of the cylinder head 14 and the circumferential side wall 29 of the cylinder 2 .

[0068] Similar to the piston 3, the piston bowl 6 extends in the axial direction A, in the radial direction R, and has a circumferential extension in the circumferential direction C. In this example, the longitudinal center axis Ac (i.e., the axial center axis) of the piston 3 is coaxial with the axial center axis of the piston bowl 6, as shown in FIG. Figure 2 as shown in .

[0069] Each cylinder 2 may also include at its vertical top end at least one and typically multiple inlet passages having at least one inlet valve 70 for controlling the inlet air flow into the combustion chamber 7, and at least one and typically multiple exhaust passages having at least one exhaust valve 60 for controlling the discharge of exhaust gas produced by the fuel combustion process occurring in the cylinder 2.

[0070] In particular, one or more intake ports with corresponding inlet valves 70 are arranged in the cylinder head 14. Figure 2 As depicted in FIG. 1 , the ICE system 100 further includes an intake manifold 72 forming one or more intake guides arranged to direct air to the cylinders 2. Similarly, one or more exhaust ports having corresponding exhaust valves 60 are arranged in the cylinder head 14. Thus, as shown in FIG. Figure 2 As depicted in , the ICE system 100 further includes an exhaust guide 62 arranged to guide gases from the cylinders 2 .

[0071] The cylinder configuration may be, for example, in-line, V-type, or any other suitable type. ICE system 100 may also include additional engine components and system components.

[0072] Furthermore, at least one fuel injector 13 is provided in the cylinder head 14, through which fuel is injected into the cylinder 2 as a fuel spray 51. The fuel is diesel fuel here. In other examples, the fuel is hydrogen fuel. Thus, the fuel injector 13 is arranged vertically in the center of the top of the combustion chamber 7.

[0073] For diesel ICE systems, the fuel is preferably injected at a pressure in the range of 600 bar to 3000 bar. Typically, for engine systems using EGR, about 1000 bar to 2500 bar may be preferred, while in the absence of EGR, about 800 bar to 1400 bar may be preferred. For hydrogen ICE systems, hydrogen fuel may be injected into the combustion chamber 7 and toward the piston bowl 6 at a low injection pressure between 15 bar and 60 bar. However, for other gaseous ICE systems, the controllable fuel injector may be controllable to inject the gaseous fuel into the combustion chamber at an injection pressure of up to about 500 bar.

[0074] The ignited fuel spray may form a plume, for example, in the combustion chamber 7 .

[0075] The injector 13 may be any suitable type of injector capable of injecting fuel. Typically, the fuel injector 13 is arranged in the cylinder 2 and axially above the piston 3. The fuel injector 13 is typically centrally disposed in the cylinder head 14 so that the geometric center axis A of the fuel injector 13 coincides with the geometric center axis of the cylinder 2, which is also the axis of reciprocating motion of the piston 3 and is hereby denoted by reference numeral A. C Therefore, the geometric center axis of the cylinder 2 and the center axis of the piston 3 can be collectively indicated by the reference numeral A C instruct.

[0076] The ICE 10 may advantageously be a four-stroke ICE comprising a plurality of cylinders 2, each provided with a piston 3, wherein each piston 3 may for example be connected to a common crankshaft 4. An ICE operable according to a conventional four-stroke process performs an intake stroke, a compression stroke, a combustion stroke and an exhaust stroke.

[0077] The fuel injector 13 is capable of injecting fuel directly into the combustion chamber 7 and towards the piston 3. The fuel injector 13 comprises at least one, preferably a plurality of injection orifices 46 for allowing the pressurized fuel to flow into the combustion chamber 7. Thus, the injected fuel will provide kinetic energy to the combustion chamber 7 so as to cause a thorough mixing of the fuel with the air contained therein. In order to enhance the combustion of the fuel and the air in the combustion chamber 7, the piston 3 also comprises a FIG. 3A to FIG. 3E , FIG. 4A to FIG. 4C , FIG. 5A to FIG. 5C and Figure 6 The piston bowl 6 of any of the examples shown in FIG. The piston 3 and its piston bowl design will be described in more detail below.

[0078] The fuel injector 13 is configured to be controlled by the controller 90 ( Figure 1 ) control. Therefore, the fuel injector is a controllable fuel injector 13. The fuel injector 13 can be controlled by several different types of actuators, including but not limited to pneumatic actuation control, electronic actuation control, electromechanical actuation control, hydraulic actuation control, and combinations thereof.

[0079] The fuel injectors 13 are connected to a fuel tank (not shown) and are in fluid communication. The number of the fuel gas injectors 13 may be equal to the number of the cylinders 2 of the ICE 10. The fuel gas injectors 13 are each arranged in fluid communication with the fuel tank.

[0080] For a hydrogen ICE system, the ICE 10 may include an ignition source, such as a spark plug (not shown).

[0081] Now we turn again to the design of the piston 3 of the ICE system 100. FIG. 3A to FIG. 3E , an example embodiment of a piston and piston crown desired for ICE 10 and ICE system 100 is shown, as described above with respect to Figure 1 and Figure 2 described. In particular, Figure 3A is a perspective top view of the axial top end 16 of the piston with the piston bowl 6 according to an example embodiment, Figure 3B yes Figure 3A The top view of the piston in Figure 3C According to an example implementation Figure 3A A perspective cross-sectional view of the axial top end 16 of the piston in FIG. Figure 3D 3 is a cross-sectional view of the piston 3 and its top end 16 along the axial direction A and the radial direction R. Figure 3E is a perspective axial cross-sectional view of the piston 3 along a given axial distance (height) of the piston bowl and along the radial direction R and the circumferential direction C.

[0082] In the embodiment shown, the piston axial top end 16 forms an integral part of the piston 3. However, it is also conceivable to arrange the piston axial top end 16 as a separate unit attached to one or more piston bases in order to form a complete piston 3. The piston axial top end 16 usually corresponds to the so-called piston crown. The piston axial top end 16 usually has an axial top surface 5, i.e. an upper surface, facing the combustion chamber 7 of the cylinder 2 when the piston is arranged in the cylinder. The axial top surface 5 is here the uppermost surface part of the piston 3. For ease of reference, the axial top surface can be denoted as top surface 5.

[0083] FIG. 3A to FIG. 3E The piston axial top end 16 is shown in more detail. Figure 3C As shown in FIG. 1 , the piston bowl surface 6 a faces the combustion chamber 7 when arranged in the ICE 10 . Figure 2 The piston bowl surface 6a includes a circumferential rim portion 20 and a bottom plate portion 11 connected to and surrounded by the circumferential rim portion 20. In other words, the piston bowl 6 includes a circumferential rim portion 20 and an axial bottom plate portion 11 connected to and surrounded by the circumferential rim portion 20. The axial bottom plate portion 11 includes a bottom plate surface 11a.

[0084] The piston bowl 6 can be provided in several different ways. FIG. 3A to FIG. 3E As shown, the bottom plate portion 11 is at least partially defined by the piston bowl surface 6a. The bottom plate portion 11 generally has a bottom plate surface 11a that is a portion of the piston bowl surface 6a. Figure 2 As shown in FIG. 3A to FIG. 3E The piston bowl 6 is defined here by a peripheral edge portion 20, a central apex 18 and a middle section 19. FIG. 3A to FIG. 3E As can be seen in the figure, the bottom plate portion 11 can be generally dome-shaped, wherein the central vertex 18 coincides with the central axis Ac of the piston 3. The bottom plate portion 11 can form a dome side surface, thereby forming part of the middle section 19 and extending circumferentially from the dome shape, and forming a dome angle between them. In this way, the bottom plate portion 11 can generally have a dome-shaped geometry that is at least partially defined by the central vertex 18. The bottom plate portion 11 here extends from the circumferential edge portion 20 to the central axis Ac in the center at the central vertex 18. The bottom plate portion 11 can be aligned with the circumferential edge portion 20, such as for example Figure 3A and Figure 3E as shown in .

[0085] Typically, although not strictly required, the middle section 19 extends between the peripheral rim portion 20 and the central apex 18, thereby together forming the piston bowl surface 6a. For example, at least the middle section 19 and the central apex 18 together define the bottom plate surface 11a. In other examples, part of the rim portion 20, the middle section 19 and the central apex 18 together define the bottom plate surface 11a, and thus together define the piston bowl surface 6a.

[0086] The circumferential rim portion 20 here also extends in the axial direction A. The circumferential rim portion 20 extends in the axial direction A between the bottom plate surface 11a and the top surface 5 of the axial top end 16. The circumferential rim portion 20 is here the radially outermost portion of the piston bowl 6, while the central apex 18 is the radially innermost portion of the piston bowl 6. The circumferential rim portion 20, the intermediate section 19 and the central apex 18 together form a cavity that is open to the outside, such as, for example Figure 3A In other piston bowl designs where the top surface may be an integral part of the piston bowl, the top surface 5 may be the radially outermost portion of the piston bowl 6.

[0087] The piston bowl 6 has an axial depth H, such as Figure 3C , Figure 3D and Figure 3E The axial depth H of the piston bowl 6 is defined by the axial distance between the bottom plate surface 11a and the top end surface 5, as shown in FIG. Figure 3D As shown in , and also for example Figure 3C and Figure 3E Indicated in FIG. 1 . Typically, the axial depth H defines the maximum axial distance between the bottom plate surface 11a and the top end surface 5. The axial depth H is thus defined as the distance between the lowermost surface portion of the bottom plate portion of the piston bowl 6 and the top end surface 5, as shown in FIG. Figure 3D as shown in .

[0088] In addition, the piston bowl 6 includes a plurality of spaced-apart protrusions 40, such as FIG. 3A to FIG. 3E As shown in . The protrusions 40 are arranged on the circumferential edge portion 20 here. The spaced protrusions 40 are distributed circumferentially around the central axis Ac. In particular, the protrusions 40 are distributed circumferentially around the circumferential edge portion 20 in a circumferential direction C spaced from each other. Therefore, a plurality of spaced protrusions 40 are distributed circumferentially around the circumferential edge portion 20.

[0089] exist FIG. 3A to FIG. 3E In the embodiment, the peripheral edge portion 20 includes a plurality of spaced apart protrusions 40. The spaced apart protrusions 40 surround the peripheral edge portion 20 and are arranged around the central axis A. C Circumferential distribution. In this way, a plurality of spaced-apart protrusions 40 are circumferentially distributed around the circumferential rim portion 20.

[0090] As can be gathered from the term “protrusion”, the protrusion section must have a certain axial extension in the axial direction A, a certain radial extension in the radial direction R and a certain circumferential extension in the circumferential direction C.

[0091] As such, each of the spaced apart protrusions 40 extends a substantial portion in the axial direction A from the bottom plate surface 11a toward the top end surface 5. FIG. 3A to FIG. 3E , each of the spaced apart protrusions 40 extends from the bottom plate surface 11a to the top end surface 5 of the piston top end 16 along the axial direction A. As such, each of the spaced apart protrusions 40 extends from the bottom plate surface 11a to the piston top end surface 15 in a continuous manner along the axial direction A. Other extensions are also contemplated, as further described below.

[0092] In addition, such as Figure 3A As shown in FIG. 1 , each of the spaced apart protrusions 40 extends a considerable portion toward the central axis AC in the radial direction R. Each protrusion 40 extends toward the central axis Ac of the piston 3 from the adjacent side of the circumferential rim portion 20, thereby forming an apex toward the central axis Ac. Each of the protrusions 40 thus faces the central axis Ac of the piston 3. The protrusions 40 are provided on the circumferential rim portion 20.

[0093] Each of the spaced apart protrusions comprises opposite radial side sections 41, 42, such as for example Figure 3A As shown in . Each of the radial side segments 41, 42 extends from the circumferential edge portion 20 in the radial direction R. One of the radial side segments is a first radial side segment 41, and the other of the radial side segments is a second radial side segment 42. Each of the first radial side segment 41 and the second radial side segment 42 extends in the radial direction. Therefore, the radial side segments may also be expressed herein as radially extending side segments or radially extending radial side segments. The first radial side segment 41 and the second radial side segment 42 are arranged opposite to each other in the circumferential direction C, such as, for example Figure 3A and Figure 3C Described in.

[0094] like FIG. 3A to FIG. 3E As shown in , the radially extending side segments 41, 42 are curved convex side segments. In other examples, the radially extending side segments 41, 42 can be curved concave side segments. In still other examples, the radially extending side segments 41, 42 can be flat side segments.

[0095] In addition, FIG. 3A to FIG. 3E In the embodiment, each of the opposing radial side segments 41, 42 comprises a plurality of regions of different convex curved profiles. Figure 3C, an example of a protrusion 40 is shown, wherein the first radially extending side segment 41 has a first convex curved profile 41a and a second convex curved profile 41b with different curved convex profiles, and the second radially extending side segment 42 has a first convex curved profile 42a and a second convex curved profile 42b with different curved convex profiles. In other examples, the first radially extending side segment 41 has a uniform curved convex profile, and the second radially extending side segment 42 has a uniform curved convex profile.

[0096] Each of the spaced apart protrusions 40 here extends at least partially over the floor portion 11 in the radial direction R. Furthermore, each of the spaced apart protrusions 40 extends in the radial direction R to be aligned with the floor surface 11 a of the floor portion 11 .

[0097] exist FIG. 3A to FIG. 3E In the illustrated embodiment of FIG, the piston bowl 6 comprises a total of six protrusions 40 equally distributed around the circumference of the piston bowl 40. However, other numbers of protrusions 40 are conceivable, such as eight protrusions.

[0098] The protrusions 40 may be distributed at 45 degree intervals around the central axis AC. Other intervals are also contemplated.

[0099] exist Figure 3A In the embodiment shown in FIG. 1 , the spaced-apart protrusions 40 are evenly distributed circumferentially around the circumferential rib portion 20 . In other design variations, although not shown, the spaced-apart protrusions 40 may be unevenly distributed circumferentially on the circumferential rib portion 20 .

[0100] like FIG. 3A to FIG. 3E As shown in FIG. 1 , each of the spaced apart protrusions 40 further includes a surface 43 extending between opposing radially extending side sections 41 , 42 . FIG. 3A to FIG. 3E In the embodiment, the surface 43 extends in the circumferential direction C between the opposite radially extending side segments 41b, 42b. FIG. 3A to FIG. 3E , the surface 43 is a concave surface 43b. Figure 3E is a cross-sectional view of the concave surface 43b, showing the concave profile of the concave surface 43b in more detail. The radius of the concave profile of the concave surface 43b is selected depending on the intended use of the piston 3. For example, the radius of the concave profile of the concave surface 43b follows the radius of the curvature of the circumferential edge portion 20. That is, the radius of the concave curvature of the concave surface 43b corresponds to the radius of the concave curvature of the circumferential edge portion 20. In such examples, the radius of curvature of the concave surface is substantially perpendicular to the axial center of the piston bowl 6. However, it should be readily understood that the radius of the concave profile of the concave surface 43b may have a concave curvature that is different from the concave curvature of the circumferential edge portion 20. For example, Figure 3CA design is shown in which the radius of the concave curvature of the concave surface 43b is different from the radius of the concave curvature of the circumferential edge portion 20. When defining and designing the concaveness of the concave surface 43b, the concaveness of the concave surface is usually determined with respect to a Cartesian coordinate system (rather than a cylindrical coordinate system), which is also well known in the art. In other words, for the concave surface 43b, the radius of curvature is the radius of the circle that best fits the normal cross section or a combination thereof. The radius of curvature of the concave surface 43b can be constant in size along the circumferential direction C, or slightly changed in size along the circumferential direction C.

[0101] In other examples, the surface may be a flat surface. Figure 6 One example of a surface 43 in the form of a flat surface 43a is shown in more detail.

[0102] For ease of reference, the following description of surface 43 will be provided with reference to concave surface 43b, such as FIG. 3A to FIG. 3E However, this description will also apply to surfaces in the form of flat surfaces 43a, such as Figure 6 as shown in .

[0103] The concave surface 43b extends for a considerable portion in the circumferential direction C. As mentioned above, the concave surface 43b here extends between the opposite radially extending radial side segments 41, 42. More specifically, the concave surface 43b extends in the circumferential direction C between the opposite radially extending radial side segments 41, 42. Figure 3E , the first radial side segment 41 of the opposite radial side segments intersects the concave surface 43b along an intersection edge 45. Similarly, the second radial side segment 42 of the opposite radial side segments intersects the concave surface 43b along another opposite intersection edge 46.

[0104] The concave surface 43 b is thus arranged to form a bridging surface between the opposing radial side sections 41 , 42 .

[0105] The concave surface 43 b is also arranged to face the center axis Ac of the piston 3 .

[0106] In other words, by providing a flat surface 43a or a concave surface 43b between the opposite radial side segments 41, 42, the surface 43, 43a, 43b between the opposite radial side segments is a non-convex surface. As used herein, the term "non-convex" means that the surface 43 does not face the central axis A of the piston 3. C Instead, the surfaces 43, 43a, 43b are straight or recessed toward the radially outer circumferential surface of the piston 3, such as from e.g. Figure 3E It can be seen in.

[0107] In some examples, such as from Figure 3EAs can be seen in FIG. 4 , the radial cross-sectional profile through the protrusion 40 resembles a truncated triangle or the like, wherein the truncated side forms a flat surface 43 a or a concave surface 43 b.

[0108] The piston bowl 6 is usually obtained by forging. For example, the surfaces 43, 43a, 43b of the piston bowl 6 are forged.

[0109] Furthermore, the concave surface 43b extends over a considerable portion in the axial direction A. As shown, for example, in FIG. 3 and also in FIG. Figure 3E As shown in , the concave surface 43b extends substantially along the axial direction A from the intersection 44 between the concave surface 43b and the bottom plate surface 11a to the top surface 5 of the piston top end 16. The intersection 44 defines the difference between the concave surface 43b and the bottom plate surface 11a. As such, the intersection 44 also defines the difference between the protrusion 40 and the bottom plate surface 11a. The intersection 44 extends along the circumferential direction C. In addition, the intersection 44 can generally be an imaginary line showing the circumferential extension of the concave surface 43b at its maximum circumferential extension, which is shown in FIG. Figure 3C Indicated by reference numeral a.

[0110] exist FIG. 3A to FIG. 3E , the concave surface 43b has an extension between at least a first circumferential extension a at the intersection 44 and a second circumferential extension b at an axial distance h from the intersection 44. In this example, the first circumferential extension a is greater than the second circumferential extension b. The first circumferential extension a is greater in the circumferential direction C than the second circumferential extension b.

[0111] Typically, the first circumferential extension a is the maximum circumferential extension of the concave surface 43b in the circumferential direction C. That is, the first circumferential extension a defines the maximum circumferential extension of the concave surface 43b in the circumferential direction C. In the following description, the first circumferential extension therefore typically refers to the first maximum circumferential extension a.

[0112] In particular, if FIG. 3A to FIG. 3E As shown in , the concave surface 43b has a first maximum circumferential extension a at the intersection 44 between the concave surface 43b and the bottom plate surface 11. FIG. 3A to FIG. 3E As shown in , the concave surface 43b has a second circumferential extension b at an axial distance h from the bottom plate surface 11a. The axial distance h is one quarter of the piston bowl depth H. The axial distance h and the depth H refer to the distance along the axial direction A. In addition, the axial distance h and the depth H refer to the distance along the axial direction A, as measured in the direction from the bottom plate surface 11a toward the top end surface 5.

[0113] For example Figure 3A As shown in Figure 3E The intersecting edges 45 , 46 define the extension of the concave surface 43 b in conjunction with the first maximum circumferential extension a and the second circumferential extension b.

[0114] In addition, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less. Here, the protrusion 40 is designed to improve the durability and fatigue properties of the protrusion during normal operation of the piston 3. Compared with other designs of piston bowl protrusions, the protrusion 40 has an improved design that withstands higher fatigue levels. The ratio between the second circumferential extension b and the first maximum circumferential extension is also expressed herein as a relative circumferential width ratio.

[0115] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4.

[0116] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is zero.

[0117] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.26. By way of example, the second circumferential extension b is 2.4 mm and the first maximum circumferential extension a is 9.3 mm. In this example, the depth H is 18.6 mm.

[0118] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.25. By way of example, the second circumferential extension b is 4.2 mm and the first maximum circumferential extension a is 16.8 mm. In this example, the depth H is 19.4 mm.

[0119] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.17. By way of example, the second circumferential extension b is 2.9 mm and the first maximum circumferential extension a is 17.5 mm. In this example, the depth H is 18.5 mm.

[0120] In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.4 and 0. In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less, but greater than 0. Therefore, in one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.4 and 0.05. In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.4 and 0.1. In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.3 and 0.15. In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.26 and 0.17. In one example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is between 0.25 and 0.17.

[0121] The above-mentioned relative circumferential width ratio, combined with the configuration of the surface 43 in the form of a flat surface 43a or a concave surface 43b, provides an improved design of the protrusion at the lower region of the protrusion and thus at the lower part of the piston bowl 6. More specifically, by having the protrusion 40 comprise a flat surface 43a or a concave surface 43b extending between the opposite radial side sections 41, 42, combined with the configuration that the ratio between the second circumferential extension b and the first circumferential extension a is 0.4 or less, the piston 3 has a design that is less sensitive in terms of required durability. Such a design can also better withstand critical fatigue conditions occurring during ordinary use of the piston 3 in heavy vehicles.

[0122] The above configuration of the protrusion is based in part on the observation that the piston operates in a "hot state", i.e., the piston 3 is exposed to high temperature loads, generating high compressive stresses at the protrusion. When the magnitude of the compressive stress exceeds a critical level, at a certain temperature, the material in the region of the protrusion may suffer from stress relaxation. Stress relaxation may occur, for example, due to long-term exposure to high stress levels that are still below the yield strength of the material. Then, when the vehicle is parked and the ICE is turned off (i.e., the ICE is not operating) or in the idle state of the ICE, the piston 3 may cool to a "cold state", which causes the stress to change from compressive stress to tensile stress. When the piston 3 is subsequently exposed to cylinder pressure loads, fatigue cracks may start and propagate at more conventional protrusions due to the cycle of maximum tensile stress from cylinder pressure and maximum tensile stress from stress relaxation.

[0123] The above described configuration of flat and concave surfaces allows to avoid or at least reduce the exposure of critical material areas of the protrusions to high tensile stresses.

[0124] In addition, the relative circumferential width ratio, combined with the configuration of the surface 43 in the form of a flat surface 43a or a concave surface 43b, ensures that the portion of the protrusion 40 in which the influence on the combustion performance is low is designed to minimize the compressive stress in the axially lower region of the protrusion for the temperature load occurring during combustion. In addition, the flat surface 43a or the concave surface 43b arranged between the radial side sections 41, 42 helps to separate the position of the maximum compressive stress due to the temperature load from the position of the maximum tensile stress due to the pressure load. The piston bowl 6 having the protrusion 40 in which the maximum stress areas are separated from each other helps to increase the durability and fatigue life of the protrusion 40, and therefore also increases the durability of the piston 3.

[0125] like Figure 3E As shown in , the convex surface 43 b itself provides the bowl-shaped design of the lower part of the protrusion 40.

[0126] It should be noted that the concave surface 43b may also extend further in the axial direction A than the second circumferential extension b. FIG. 3A to FIG. 3EAs shown in , the concave surface 43b generally extends along the axial direction A from the bottom plate surface 11a all the way to the top end surface 5. For example, the concave surface 43b extends completely along the axial direction A from the bottom plate surface 11a to the top end surface 5. However, in other examples, the concave surface 43b extends along the axial direction A from the bottom plate surface 11a to a given intermediate axial distance between one quarter of the depth of the piston bowl 6 and the depth H of the piston bowl 6. Therefore, the concave surface 43b generally extends along the axial direction A from the bottom plate surface 11a toward the top end surface 5. For example, the concave surface 43b generally extends along the axial direction A from the bottom plate surface 11a toward the top end surface 5, and makes the extension along the axial direction A greater than one quarter of the depth of the piston bowl 6, but less than the depth H of the piston bowl 6.

[0127] Therefore, for example Figure 3D As shown in , the extension of the concave surface 43b from the first circumferential extension a to the second circumferential extension b also includes an axially extending concave area. The axially extending concave area also extends from the bottom plate surface 11a toward the top end surface 5. The protrusion 40 also includes an additional upper axially extending convex surface, such as Figure 3D The lower axially extending concave area and the upper axially extending convex surface form an "S" shape, as shown in Figure 3D Described in.

[0128] In other examples, the concave surface 43b extends only from the bottom plate surface 11a to the second circumferential extension b in the axial direction A. As mentioned above, the second circumferential extension b is axially located at an axial distance h from the bottom plate surface 11a. The axial distance h is one quarter of the depth H of the piston bowl 6.

[0129] In the example, as also mentioned above, although not shown, in the case where the ratio between the second circumferential extension b and the first maximum circumferential extension a is zero (0), the concave surface 43b extends only from the bottom plate surface 11a to the second circumferential extension b in the axial direction A. In this way, a concave surface 43b similar to a triangle extending in the axial direction A and in the circumferential direction C is provided.

[0130] Thus, the extension of the concave surface 43b is defined by the axially inclined intersection edges 45 and 46 together with a first circumferential extension a at the intersection 44 and a second circumferential extension b at an axial distance h from the intersection 44. Such extension of the concave surface 43b resembles a trapezoid, i.e. a triangular base shape, with the maximum circumferential width at the intersection 44 and the minimum width at the other axial side, i.e. the second circumferential extension b. In e.g. Figure 3CIn the embodiment of the present invention, the concave surface 43b forming a trapezoidal surface in the axial direction A and in the circumferential direction C can be designed essentially as a duck's foot. It should be understood that the term "triangular base shape" also covers triangles with rounded corners and even triangles whose vertices are cut to form an equilateral trapezoid. Triangles with non-linear circumferential edges are also conceivable.

[0131] like FIG. 3A to FIG. 3E As shown in FIG. 1 , the intersection edges 45, 46 are inclined in a nonlinear manner (curved manner) from the first maximum circumferential extension a to the second circumferential extension b. However, the intersection edges 45, 46 can also be inclined in a linear manner from the first maximum circumferential extension a to the second circumferential extension b. The intersection edges 45, 46 are inclined toward a central area located on the second circumferential extension b (in the circumferential direction), as shown in FIG. FIG. 3A to FIG. 3E The intersecting edges 45, 46 define the overall extension of the concave surface 43, 43a, 43b in conjunction with the first circumferential extension a and the second circumferential extension b.

[0132] Similar to the concave surface 43b, the spaced apart protrusions 40 can extend in the axial direction A in several different ways. As mentioned above, and as FIG. 3A to FIG. 3E As shown in FIG. 1 , each of the spaced protrusions 40 extends between the bottom plate surface 11a of the bottom plate portion 11 and the top surface 5 toward the piston top 16 in the axial direction A. In particular, each of the spaced protrusions 40 extends between the bottom plate surface 11a of the bottom plate portion 11 and the top surface 5 toward the piston top 16 in the axial direction A. It should be noted that FIG. 3A to FIG. 3B The intersecting edges 45 , 46 in the bottom plate portion 11 may generally extend in the axial direction A between the bottom plate surface 11 a and the top end surface 5 of the bottom plate portion 11 .

[0133] In another example, each of the spaced protrusions 40 may extend only in the axial direction A from the bottom plate surface 11a to the second circumferential extension b. As mentioned above, the second circumferential extension b is axially located at an axial distance h from the bottom plate surface 11a. The axial distance h is one quarter of the depth H of the piston bowl 6. In other examples, each of the spaced protrusions 40 may extend in the axial direction A from the bottom plate surface 11a to a given intermediate axial distance that is greater than one quarter of the depth of the piston bowl 6 but less than the depth of the piston bowl 6. In other words, each of the spaced protrusions 40 may extend in the axial direction A from the bottom plate surface 11a toward the top end surface 5 to a distance between one quarter of the depth of the piston bowl 6 but less than the depth H of the piston bowl 6 in the axial direction A. In this example, the concave surface 43b generally extends similarly, i.e., between one quarter of the depth of the piston bowl 6 but less than the depth of the piston bowl H in the axial direction A from the bottom plate surface 11a toward the top end surface 5.

[0134] Optionally, all of the spaced-apart protrusions 40 extend along the first circumferential direction of the circumferential edge portion 20 by a1, a2, a n The ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is at least 30%, preferably at least 45%, and most preferably at least 60%. This ratio can also be called the circumferential extension ratio. The circumferential extension ratio is a ratio defined in percentage. The percentage is a dimensionless number, while the basic unit of extension refers to length.

[0135] In one example, all of the spaced-apart protrusions 40 extend along a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a30, a19 ...0, a30, a19 n The circumferential extension ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is 0.36. By way of example, the first maximum circumferential extension a is 9.3 mm and the circumferential extension E is 26.1 mm. In this example, the second circumferential extension b may be, for example, 2.4 mm.

[0136] In one example, all of the spaced-apart protrusions 40 extend along a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a30, a19 ...0, a30, a19 n The circumferential extension ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is 0.65. By way of example, the first maximum circumferential extension a is 16.8 mm and the circumferential extension E is 26.0 mm. In this example, the second circumferential extension b may be, for example, 4.2 mm.

[0137] In one example, all of the spaced-apart protrusions 40 extend along a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a30, a19 ...0, a30, a19 n The circumferential extension ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is 0.64. By way of example, the first maximum circumferential extension a is 17.5 mm and the circumferential extension E is 27.4 mm. In this example, the second circumferential extension b may be, for example, 2.9 mm.

[0138] In some examples, each of the spaced apart protrusions 40 extends from the circumferential rim portion 20 to at least the middle section 19 in the radial direction R. In addition, the circumferential rim portion 20 extends in the axial direction A between the bottom plate portion 11 and the piston top end 16 (typically between the bottom plate surface 11a of the bottom plate portion 11 and the top end surface 5 of the piston top end 16).

[0139] exist FIG. 4A to FIG. 4C In FIG. 1 , another design of the piston bowl 6 is shown, wherein the piston bowl 6 is FIG. 3A to FIG. 3E Compared to the first maximum circumferential extension a of the concave surface 43b, the concave surface 43b comprises a smaller first maximum circumferential extension a, while FIG. 4A to FIG. 4C The second circumferential extension b of the concave surface 43b is FIG. 3A to FIG. 3EThe second circumferential extension b of the concave surfaces 43b is identical. FIG. 4A to FIG. 4C The piston design in is another example of a concave surface 43b, wherein the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less.

[0140] In addition, FIG. 4A to FIG. 4C , the concave surface 43b extends in the axial direction A from the base plate surface 11a to an axial distance h corresponding to the axial position of the second circumferential extension b. The protrusion 40 here includes an additional surface area 47. The additional surface area 47 extends in the axial direction from an axial distance h corresponding to the axial position of the second circumferential extension b to the top end surface 5. Compared to the surface 43, the additional surface area 47 here has another contour, for example, a convex surface. In this way, compared to the concave surface 43a, the additional surface area 47 here has another contour. The additional surface area 47 can have a curved surface contour similar to the curved contour of the radial side segments 41, 42. The additional surface area 47 can also have a surface contour different from the curved contour of the radial side segments 41, 42. As FIG. 4A to FIG. 4C As shown in FIG. 4 , the additional surface area 47 extends in the circumferential direction C and generally extends between the radial side segments 41 , 42 . The additional surface area 47 also cooperates with the top end surface 5 , as shown in FIG. FIG. 4A to FIG. 4C The additional surface area 47 here cooperates with the top end surface 5 in a convexly curved manner, as can be seen in the radial direction R.

[0141] Thus, as is readily understood from the above, the concave surface 43b extends at least in the axial direction A from the first maximum circumferential extension a to an axial distance h (H / 4) corresponding to the axial position of the second circumferential extension b. Depending on the design of the protrusion 40, the concave surface 43b then ends at the axial distance h (H / 4), i.e. at the second circumferential extension b, or to a given intermediate axial distance between a quarter of the depth H of the piston bowl 6 and the depth H of the piston bowl 6. If the concave surface 43b ends at the axial distance h (H / 4), i.e. at the second circumferential extension b, the rest of the protrusion 40 axially located above the concave surface 43b is typically formed by the additional surface area 47 together with the radial side segments 41, 42. Similarly, if the concave surface 43b ends at a given intermediate axial distance between a quarter of the depth H of the piston bowl 6 and the depth H of the piston bowl 6, the rest of the protrusion 40 axially located above the concave surface 43b is typically formed by the additional surface area 47 together with the radial side segments 41, 42. However, in other examples, such as FIG. 3A to FIG. 3E As shown in FIG. 4 , there is no additional surface area 47. That is, the surface 43 in the form of the concave surface 43 b extends substantially to the top surface 5. Due to the overall design of the protrusion 40, there can generally be a smooth curved transition surface between the concave surface 43 b and the top surface 5, such as from, for example Figure 3CIt can be seen in.

[0142] exist FIG. 5A to FIG. 5C In FIG. 5 , another design of the piston bowl 6 is shown in which each of the spaced apart protrusions 40 extends to an axial distance less than the top end surface 5, as measured from the bottom plate surface 11a. In addition, in this example, the concave surface 43b has the same Figure 4A 4E concave surface 43b of the first maximum circumferential extension a the same as the first maximum circumferential extension a, and in FIG. 5A to FIG. 5C The second circumferential extension b of the concave surface 43b is FIG. 3A to FIG. 3E and FIG. 4A to FIG. 4C The second circumferential extension b of the concave surfaces 43b is identical. FIG. 5A to FIG. 5C The piston design in is another example of a concave surface 43b, wherein the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less. Thus, increased fatigue of the protrusion can be provided by several different concave surfaces 43b.

[0143] Similar to Figure 4a to Figure 4C The design shown in FIG. 5A to FIG. 5C The concave surface 43b in the projection 40 extends only in the axial direction A from the bottom plate surface 11a to an axial distance h corresponding to the axial position of the second circumferential extension b. Therefore, the projection 40 also includes an additional surface area 47 here. The additional surface area 47 extends in the axial direction from the axial distance h corresponding to the axial position of the second circumferential extension b to the top surface 5. The additional surface area 47 is also a convex surface profile here. However, in other examples, FIG. 5A to FIG. 5C The concave surface 43b in FIG. 3A to FIG. 3C The middle part similarly extends to the top surface 5.

[0144] It should be noted that Figure 1 , Figure 2 and FIG. 3A to FIG. 3E Other conditions, examples and features described may be related to FIG. 4A to FIG. 4C and FIG. 5A to FIG. 5C The embodiments, examples and features of the present invention are incorporated and combined unless otherwise limited.

[0145] Figure 6 An example of a protrusion 40 having a flat surface 43a instead of a concave surface is shown. Also in this example, the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less. Therefore, increased fatigue of the protrusion can be provided by the concave surface 43b or the flat surface 43a, provided that the ratio between the second circumferential extension b and the first maximum circumferential extension a is 0.4 or less. Figure 6In the example, the axial extension of the flat surface 43a from the first circumferential extension a to the second circumferential extension b is also defined by the concave surface. However, in other examples, the axial extension of the flat surface 43a from the first circumferential extension a to the second circumferential extension b is also defined by the flat surface.

[0146] It should be noted that Figure 1 , Figure 2 , FIG. 3A to FIG. 3E , FIG. 4A to FIG. 4C and FIG. 5A to FIG. 5C Other conditions, examples and features described may be related to Figure 6 The piston bowl 6 is combined and assembled unless otherwise limited.

[0147] In summary, a piston 3 extending in an axial direction A and a radial direction R is provided. The piston 3 comprises an axial top end 16 having a piston bowl 6 intended to form a part of a combustion chamber 7. The piston bowl 6 comprises an axial bottom plate portion 11 having a bottom plate surface 11a, a circumferential rim portion 20 extending in the axial direction A between the bottom plate surface 11a and the top end surface 5 of the axial top end 16. The piston bowl 6 defines an axial depth H, which is defined by the axial distance between the bottom plate surface 11a and the top end surface 5. Furthermore, the piston bowl 6 comprises a plurality of spaced-apart protrusions 40 distributed circumferentially around the circumferential rim portion 20. Each of the spaced-apart protrusions 40 extends a considerable portion in the radial direction R towards the central axis Ac, and also extends a considerable portion in the axial direction A from the bottom plate surface 11a towards the top end surface 5. Each of the spaced apart protrusions 40 has opposite radial side sections 41, 42, and further includes a flat surface 43, 43a or a concave surface 43, 43b extending between the opposite radial side sections 41, 42. The flat surface 43a or the concave surface 43b includes a first circumferential extension a at an intersection 44 between the flat surface or the concave surface and the bottom plate surface 11a, and further includes a second circumferential extension b at an axial distance h from the bottom plate surface 11a. The axial distance h is one quarter of the piston bowl depth H. In addition, the second circumferential extension b and the first circumferential extension a define a ratio of 0.4 or less.

[0148] Advantages associated with improved fatigue may also be provided by the circumferential extension ratio alone, ie, where all spaced-apart protrusions 40 extend along the first circumferential extension a1, a2, a3 of the circumferential edge portion 20. n The ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is at least 30%, preferably at least 45% and most preferably at least 60%.

[0149] Therefore, a piston 3 extending in an axial direction A and a radial direction R is also provided. The piston 3 comprises an axial top end 16 having a piston bowl 6 intended to form a part of a combustion chamber 7. The piston bowl 6 comprises an axial bottom plate portion 11 having a bottom plate surface 11a, a circumferential rim portion 20 extending in the axial direction A between the bottom plate surface 11a and the top end surface 5 of the axial top end 16. The piston bowl 6 defines an axial depth H, which is defined by the axial distance between the bottom plate surface 11a and the top end surface 5. Furthermore, the piston bowl 6 comprises a plurality of spaced-apart protrusions 40 distributed circumferentially around the circumferential rim portion 20. Each of the spaced-apart protrusions 40 extends a considerable portion in the radial direction R towards the central axis Ac, and also extends a considerable portion in the axial direction A from the bottom plate surface 11a towards the top end surface 5. Each of the spaced apart protrusions 40 has opposite radial side sections 41, 42 and further includes a flat surface 43, 43a or a concave surface 43, 43b extending between the opposite radial side sections 41, 42. The flat surface 43a or the concave surface 43b includes a first circumferential extension a at an intersection 44 between the flat surface or the concave surface and the bottom plate surface 11a. In addition, all of the spaced apart protrusions 40 extend from a1 to a1 along the first circumferential extension of the circumferential edge portion 20. n The ratio between the sum of and the circumferential extension E of the circumferential edge portion 20 is at least 30%, preferably at least 45% and most preferably at least 60%.

[0150] The present disclosure also relates to an ICE system 100 including a diesel internal combustion engine, as described herein. The ICE system 100 includes a system for burning fuel and having a cylinder 2 and a combustion chamber according to FIG. 3A to FIG. 3E , FIG. 4A to FIG. 4C , FIG. 5A to FIG. 5C and Figure 6 An internal combustion engine 10 having a combustion chamber 7 defined by a reciprocating piston 3 of any of the above examples. The reciprocating piston is movable within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), wherein the piston top is arranged to form a part of the combustion chamber.

[0151] The present disclosure also relates to an ICE system 100 and an ICE system according to FIG. 3A to FIG. 3E , FIG. 4A to FIG. 4C , FIG. 5A to FIG. 5C and Figure 6 A vehicle 1 having a piston 3 according to any of the above examples.

[0152] Although the present disclosure has been described with reference to specific exemplary embodiments thereof, many different changes, modifications, etc. will be apparent to those skilled in the art. Therefore, it should be understood that the present disclosure is not limited to the embodiments described above and shown in the accompanying drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1. A piston (3) for an internal combustion engine (ICE) (10), the piston extending in an axial direction (A) and in a radial direction (R) and having an axial top end (16) comprising a piston bowl (6) intended to form part of a combustion chamber, The piston bowl has an axial bottom plate portion (11) with a bottom plate surface (11a) and a circumferential edge portion (20) extending in the axial direction (A) between the bottom plate surface and the top end surface (5) of the axial top end, The piston bowl also has an axial depth (H) defined by the axial distance between the bottom plate surface and the top end surface, The piston bowl further comprises a plurality of spaced-apart protrusions (40) circumferentially distributed around the circumferential rim portion (20), Each of the spaced apart protrusions is oriented toward the central axis (A) along the radial direction. C ) extends a considerable portion, and also extends a considerable portion in the axial direction from the bottom plate surface toward the top end surface, Each of the spaced apart protrusions has opposing radial side sections (41, 42) and further has a flat surface or a concave surface extending between the opposing radial side sections, the flat surface (43, 43a) or the concave surface (43, 43b) having a first circumferential extension (a) at an intersection (44) between the flat surface or the concave surface and the bottom plate surface, and further having a second circumferential extension (b) at an axial distance (h) from the bottom plate surface, the axial distance (h) being one quarter of the axial depth (H) of the piston bowl, and Wherein a ratio between the second circumferential extension (b) and the first circumferential extension (a) is 0.4 or less.

2. The piston according to claim 1, wherein all of the spaced-apart protrusions extend along the first circumferential direction of the circumferential edge portion (a1, a2, a n ) to the circumferential extension (E) of the circumferential edge portion (20) is at least 30%, preferably at least 45%, and most preferably at least 60%.

3. A piston according to any one of the preceding claims, wherein a first radial side segment (41) of the opposing radial side segments intersects with the flat surface or concave surface along an intersection edge (45), and a second radial side segment (42) of the opposing radial side segments intersects with the flat surface or concave surface along another opposing intersection edge (46). 4 . The piston of claim 3 , wherein the intersection edge defines an extension of the planar surface or the concave surface in conjunction with the first circumferential extension and the second circumferential extension.

5. A piston according to claim 3 or claim 4, wherein each of the intersecting edges is inclined from the first circumferential extension to the second circumferential extension in a linear manner or in a non-linear manner, such as in a curved manner, respectively.

6. The piston according to any one of claims 3 to 5, wherein the intersecting edge defines in combination with the first circumferential extension and the second circumferential extension a surface similar to a trapezoidal or triangular shape.

7. A piston according to any one of the preceding claims and wherein the extension of the planar surface or the concave surface from the first circumferential extension to the second circumferential extension further comprises an axially extending concave region.

8. A piston according to any one of the preceding claims, wherein the extension of the planar surface from the first circumferential extension to the second circumferential extension is defined by a planar surface profile.

9. A piston according to any one of the preceding claims, wherein each of the opposing radial side sections comprises a plurality of regions of different convexly curved profiles.

10. A piston according to any one of the preceding claims, wherein the spaced apart protrusions are evenly distributed circumferentially along the circumferential rim portion.

11. The piston according to any one of the preceding claims 1 to 9, wherein the spaced apart protrusions are non-uniformly distributed circumferentially along the circumferential rim portion.

12. A piston according to any one of the preceding claims, wherein each of the spaced apart protrusions extends in the axial direction from the base plate surface to the top end surface of the piston top end.

13. A piston according to any one of the preceding claims, wherein the flat or concave surface extends in the axial direction from the intersection between the flat or concave surface and the base plate surface towards the top end surface of the piston top end.

14. The piston of claim 13, wherein the flat or concave surface extends in the axial direction from the intersection between the flat or concave surface and the bottom plate surface to the top end surface of the piston top end.

15. The piston of claim 13, wherein the flat or concave surface extends in the axial direction from the intersection between the flat or concave surface and the base plate surface to the second circumferential extension.

16. A piston according to any one of the preceding claims, wherein each of the spaced apart protrusions extends at least partially above the base plate portion in the radial direction.

17. A piston according to any one of the preceding claims, wherein the first circumferential extension is the maximum circumferential extension of the planar or concave surface.

18. A piston (3) for an internal combustion engine (ICE) (10), the piston extending in an axial direction (A) and in a radial direction (R) and having an axial top end (16) comprising a piston bowl (6) intended to form part of a combustion chamber, The piston bowl has an axial bottom plate portion (11) with a bottom plate surface (11a) and a circumferential edge portion (20) extending in the axial direction (A) between the bottom plate surface and the top end surface (5) of the axial top end, The piston bowl also has an axial depth (H) defined by the axial distance between the bottom plate surface and the top end surface, The piston bowl further comprises a plurality of spaced-apart protrusions (40) circumferentially distributed around the circumferential rim portion (20), Each of the spaced apart protrusions is oriented toward the central axis (A) along the radial direction. C ) extends a considerable portion, and also extends a considerable portion in the axial direction from the bottom plate surface toward the top end surface, Each of the spaced-apart protrusions has opposite radial side sections (41, 42) and further has a flat surface (43a) or a concave surface (43, 43b) extending between the opposite radial side sections, the flat surface (43, 43a) or the concave surface (43, 43b) having a first circumferential extension (a) at an intersection (44) between the flat surface or the concave surface and the base plate surface, wherein all the spaced-apart protrusions extend along the first circumferential extension (a1, a2, a3) of the circumferential edge portion. n ) to the circumferential extension (E) of the circumferential edge portion (20) is at least 30%, preferably at least 45%, and most preferably at least 60%.

19. An internal combustion engine, ICE, system (100), comprising an internal combustion engine (10) for burning fuel and having a combustion chamber (7) at least partially defined by a cylinder (2) and a reciprocating piston (3) according to any one of the preceding claims, the reciprocating piston being movable within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), wherein the piston top is arranged to form a part of the combustion chamber.

20. A vehicle (1) comprising a piston according to any one of claims 1 to 18 and / or an internal engine combustion system according to claim 19.

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