Piston for internal combustion engine

Abstract

The present invention relates to a piston 16 for an internal combustion engine 10, particularly a V-engine, including an oil discharge groove 54 disposed in an outer peripheral surface of the piston 16 between a ring belt 26 of the piston 16 and a piston skirt 24, the piston skirt 24 having two recessed pin boss portions 42 on opposite sides of the piston 16, and the piston skirt 24 further including at least one oil discharge duct 56 disposed between the two recessed pin boss portions 42 on the outer surface of the piston skirt 24 and configured to fluidly connect the oil discharge groove 54 to the recessed pin boss portions 42.

Description

[Technical field]

[0001] The present invention relates to a piston for use in an internal combustion engine, and to an internal combustion engine, in particular a V-engine, equipped with at least one such piston. [Background technology]

[0002] It is known in internal combustion engines, such as diesel engines, to employ pistons in a structural arrangement including a piston head and a piston skirt, the piston head including an outer ring belt on its circumferential outer surface which defines a plurality of circumferentially continuous ring grooves for receiving corresponding piston rings which abut the inner wall of the engine's cylinder through which the piston reciprocates during operation.

[0003] Piston rings function to seal the combustion chamber from the engine's crankcase, and are further intended and designed to regulate engine oil consumption by maintaining the proper amount of oil between the piston and cylinder wall and by scraping oil from the cylinder wall back into an oil sump contained in the crankcase.

[0004] To do so, the lowest part of the ring groove, i.e. the one located closest to the piston skirt, usually houses a so-called oil scraper ring, which is configured to scrape oil off the cylinder wall so as to limit and regulate the amount of oil passing the further piston rings. In this way, the scraper ring aims to minimize the so-called "blow-by" effect, where oil slides past the piston rings into the combustion chamber. This unintended release of oil into the combustion chamber, commonly also called "oil slide", can lead to reduced engine performance, reduced life of engine components, and undesirable hydrocarbon emissions of the engine.

[0005] Specifically, the oil scraper ring is designed to accumulate oil scraped off the cylinder wall in front of it during the piston's downstroke. Therefore, to ensure proper functioning of the oil scraper ring, the oil accumulated in front of the ring must be adequately drained to ensure that a sufficient amount of oil can be scraped off the cylinder wall. Thus, known piston configurations include an oil drainage path designed to guide oil accumulated in front of the ring belt during the piston's downstroke movement back to the crankcase.

[0006] In one known piston design, the bottom ring groove, which houses the oil scraper ring, is connected to a limited number of oil drain holes in the piston skirt and configured to guide oil accumulated in the bottom ring groove to the inside of the piston skirt, from where the oil then flows back through the open bottom of the piston skirt into the crankcase.

[0007] Further piston configurations are known, for example from US Pat. No. 6,557,514 B1, in which oil accumulated in front of the ring belt during the piston's downstroke movement is received in a circumferential oil drain groove arranged adjacent to the lowest piston ring groove and then guided across the outer surface of the piston skirt to be discharged into the crankcase. In particular, on opposing sides, the piston skirt is provided with a concave pin boss that opens into the oil drain groove. With such a configuration, the oil received in the oil drain groove is guided across the outer surface of the concave pin boss back down into the crankcase and discharged.

[0008] However, when applying known piston configurations to V-engines, the angulation of the piston can affect the oil flow across and through the piston skirt. In this way, the expelled oil can experience increased flow resistance when flowing through the oil return path formed by the piston. For example, this can be caused by oil splashing or by the oil deflecting upwards against gravity. As a result, a sufficiently high oil return flow rate from the ring belt into the piston skirt can not be ensured, which can lead to oil sliding into the combustion chamber during operation. Summary of the Invention

[0009] Starting from the prior art, it is an object to provide an improved piston for an internal combustion engine, which effectively prevents oil sliding into the combustion chamber of the engine, in particular when applied to a V-engine. It is therefore an object to provide an internal combustion engine, in particular a V-engine, with at least one such piston.

[0010] These objects are solved by the subject matter of the independent claims. Preferred embodiments are set out in the description, the drawings, as well as in the dependent claims.

[0011] Thus, there is provided a piston for an internal combustion engine, in particular a V-engine, comprising an oil drainage groove in an outer peripheral surface of the piston between a ring belt of the piston and a piston skirt, the piston skirt comprising two concave pin boss portions on opposite sides of the piston and at least one oil drainage duct located between the two concave pin boss portions on the outer surface of the piston skirt, the oil drainage duct being configured to fluidly connect the oil drainage groove with the concave pin boss portions.

[0012] Furthermore, there is provided an internal combustion engine, in particular a V-engine, comprising at least one piston as described above. [Brief description of the drawings]

[0013] The present disclosure will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: [Figure 1] 1 shows a schematic cross-sectional view of an internal combustion engine. [Diagram 2] 2 shows an enlarged view of the internal combustion engine shown in FIG. [Diagram 3] FIG. 3 is a schematic front view of a piston used in the engine shown in FIGS. 1 and 2. [Figure 4] FIG. 4 shows a schematic side view of the piston shown in FIG. 3. [Diagram 5] FIG. 13 shows a schematic perspective view of a piston according to another configuration. [Figure 6] 6 shows a further schematic perspective view of the piston shown in FIG. 5; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In the following, the invention will be described in more detail with reference to the accompanying drawings, in which similar elements are indicated with the same reference numerals and in which repeated description thereof may be omitted to avoid redundancy, in which:

[0015] FIG. 1 shows diagrammatically an internal combustion engine 10, hereafter also referred to as "engine". The engine may be implemented in a vehicle, such as a ship or a construction vehicle, as a main or auxiliary engine. In the configuration shown, the engine 10 is provided in the form of a V-engine, comprising a number of cylinders 12, for example 8, 12 or 18 cylinders, arranged in a V-shape. Specifically, as can be inferred from FIG. 1, the cylinders 12 are arranged in two rows parallel to a crankshaft 14 of the engine 10. Each line of cylinders 12 is also referred to as a cylinder bank. The angle between the cylinder banks, also referred to as the "bank angle", is 40° in the configuration shown, but is not limited thereto. Rather, the engine 10 may comprise any suitable bank angle, for example in the range of 20° to 120°, specifically a bank angle of 50°.

[0016] Each cylinder 12 houses a piston 16 having a head portion that defines a combustion chamber 18 within the cylinder 12. Specifically, the piston 16 is configured for reciprocating and axial movement within the cylinder 12 and is connected to a crankshaft 14 of the engine 10 via a connecting rod 20.

[0017] The engine 10 further includes a control system (not shown) for controlling operation of an intake system (not shown) for selectively supplying an air-fuel mixture to the combustion chamber 18, an ignition system (not shown) for selectively igniting the air-fuel mixture received in the combustion chamber 18, and an exhaust system (not shown) for selectively exhausting combustion gases from the combustion chamber 18.

[0018] With such an arrangement, i.e., upon ignition of the air-fuel mixture within the combustion chamber 18, hot, high-pressure gases are generated within the combustion chamber 18 which exert a force on the piston 16, moving it axially, thereby rotating the crankshaft 18. In this manner, chemical energy is converted into mechanical energy.

[0019] The basic structure and mode of operation of engine 10 and its components are well known to those skilled in the art and therefore will not be further specified. Rather, those characteristics of piston 16 employed in engine 10 that are interrelated with the present invention are addressed below.

[0020] Figure 2 shows an enlarged view of the piston 16 in a mounted state, i.e., installed in the cylinder 12 of the engine 10. Figures 3 and 4 therefore show the piston 16 shown in Figures 1 and 2 in an unmounted state, i.e., disassembled from the engine 10.

[0021] The piston 16 preferably has a multi-part design, for example a two-part design, in which the piston head 22 and the piston skirt 24 constitute separate parts of the piston 16. Alternatively, the piston 16 may have a one-piece design, also referred to as a monoblock construction or monoblock piston, in which the piston 16 is a single-piece casting.

[0022] The piston head 22 is provided at its circumferential outer surface with a cylindrical ring belt 26 spaced from the front surface of the piston head 22 which defines the combustion chamber 18 of the cylinder 12. The ring belt 26 is formed with a number of piston ring grooves 28, 30, 32 in the outer surface of the ring belt 26, each of which is designed to receive a piston ring 34, 36, 38, also called oil control ring, as can be inferred from FIG. 2. In particular, the piston rings 34-38 are configured to seal the combustion chamber 18 from the crankcase of the engine 10 and at the same time to maintain an appropriate amount of oil between the piston 16 and the cylinder wall 40 during the operation of the engine 10. The piston rings 34-38 therefore limit and regulate the consumption of engine oil by scraping it from the cylinder wall 40 back to the oil sump contained in the crankcase, as described below.

[0023] Specifically, to do so, the bottom piston ring 38, i.e., received in the bottom ring groove 32, is provided in the form of a so-called oil scraper ring. As such, the piston ring 38 received in the bottom ring groove 32 is configured to scrape oil off the cylinder wall 40 during the downstroke movement of the piston 16 within the cylinder 12.

[0024] In the context of this disclosure, the term “lower piston ring” 38 refers to one of the multiple piston rings 34 - 38 that is located closest to the piston skirt 24 .

[0025] The piston head 22 further includes an internally cooled galley (not shown) through which cooling oil circulates to cool the piston 16, i.e., the head portion thereof, during operation. The basic structure and operation of such an internally cooled galley is well known to those skilled in the art and therefore will not be further specified.

[0026] The piston skirt 24 includes two concave pin boss portions 42 disposed on opposite sides of the piston skirt 24. In other words, the pin boss portions 42 are disposed opposite each other with respect to the longitudinal axis L of the piston 16.

[0027] In the context of this disclosure, the term “longitudinal axis” L refers to the axis of the piston 16 that is parallel to the direction of reciprocating movement of the piston within the cylinder 12 .

[0028] Each of the recessed pin boss portions 42 includes a pin boss 44 that receives a wrist pin 46 for pivotally coupling the piston 16 to the connecting rod 20. As such, the wrist pin 46 extends through the interior of the piston skirt 24 and is coupled to a pin bore 48 formed in the pin boss 44. The pin bore 48 is thus aligned along a pin bore axis P of the piston.

[0029] In the context of this disclosure, the term “pin bore axis” P refers to the axis of the piston 16 that is perpendicular to the longitudinal axis L of the piston 16 and parallel to the longitudinal axis of the wrist pin 46 .

[0030] In the illustrated configuration, the recessed pin boss portion 42 is disposed adjacent to a cylindrical portion 50 of the piston skirt 24. The recessed pin boss portion 42 together with the cylindrical portion 50 define a shell surface, i.e., an outer surface, of the piston skirt 24.

[0031] More specifically, the piston skirt 24 is provided such that, in the mounted state of the piston 16, the outer surface of the cylindrical portion 50 of the piston skirt 24 is arranged adjacent to the cylinder wall 40 and substantially follows its shape, while the outer surface 52 of the concave pin boss portion 42 is spaced from the cylinder wall 40. In other words, in the region of the pin boss portion 42, a part of the shell surface of the piston skirt 24 is intentionally recessed compared to the cylindrical shell surface, while the other part of the shell surface of the piston skirt formed by the cylindrical portion 50 is designed to substantially follow the cylindrical shell surface. In this way, when received in the cylinder 12, a gap is formed, i.e. in the radial direction, between the concave pin boss portion 42 and the cylinder wall 40. This gap is substantially larger than the gap formed between the cylindrical portion 50 of the piston skirt 24 and the cylinder wall 40.

[0032] 1-4, the outer surface 52 of the concave pin boss portion 42, which forms the outer surface of the piston 16, is planar. Alternatively, the outer surface 52 may include a number of radially inwardly extending recesses, particularly in the area about the pin bore 48, as shown in the further configuration of the piston 16 shown in Figures 5 and 6.

[0033] Furthermore, the piston 16 includes an oil drainage groove 54 disposed on the outer circumferential surface of the piston between the ring belt 26 and the piston skirt 24 of the piston 16. In the configuration shown, the oil drainage groove 54 constitutes a circumferentially continuous ring groove in the outer surface, i.e., shell surface, of the piston 24. The oil drainage groove 54 separates the piston head 22 and the piston skirt 24 from each other. In other words, the ring belt 26, the oil drainage groove 54 and the piston skirt 24 are arranged in succession, i.e., one after the other, below the piston 26 or in the direction of downstroke movement, i.e., along the longitudinal axis L.

[0034] In the context of this disclosure, the term "downward or downstroke movement direction" of piston 16 refers to the direction of movement of piston 16 along its longitudinal axis L, which, in the mounted state of piston 16, faces crankshaft 14 or crankcase of engine 10.

[0035] The oil drain groove 54 is configured to receive and collect oil that accumulates forward or in front of the ring belt 26 during operation of the piston 16. In short, as described above, the bottom piston ring 38 received in the bottom ring groove 32 is configured to scrape oil off the cylinder wall 40 during the downstroke movement of the piston 16 within the cylinder 12. In other words, when moving the piston 16 axially downward within the cylinder 12, i.e., in the direction of downstroke movement, the bottom ring groove 32 scrapes the oil that is then received in the oil drain groove 54 off the cylinder wall 40.

[0036] Furthermore, the piston 16 includes two oil drain ducts 56 designed and configured to drain the oil collected in the oil drain groove 54 to the crankcase. Specifically, the piston skirt 24 includes the oil drain ducts 56 on its outer surface, whereby each of the oil drain ducts 56 is disposed between the concave pin boss portions 42. In other words, in the circumferential direction of the piston 16, i.e., around its longitudinal axis L, each of the oil drain ducts 56 is disposed between the concave pin boss portions 42. The oil drain ducts 56 are configured to fluidly connect the oil drain groove 54 to the concave pin boss portion 42. More specifically, the oil drain ducts 56 are designed and configured to guide the oil received in the oil drain groove 54 toward the concave pin boss portion 42, i.e., toward the gap formed between the concave pin boss portion 42 and the cylinder wall 40, during the operation of the piston 16. In other words, the oil drain duct 56 is configured and designed to drain oil from the oil drain groove 54 to the crankcase of the engine 10 as it guides the oil collected in the oil drain groove 54 through the oil drain duct 56 and then along the outer surface 52 of the concave pin boss portion 42 before being discharged into the crankcase.

[0037] By providing the oil discharge duct 56, the proposed piston 16 ensures that the flow cross section of the flow passage for discharging the oil collected in front of the belt ring 26 to the crankcase is high enough along the entire flow passage, thus ensuring proper removal of the oil from the ring belt 24. In this way, the oil collected in front of the ring belt 26 is prevented from being subjected to high flow resistance and therefore to excessive pressures that could cause oil sliding into the combustion chamber 18.

[0038] In the two configurations of the piston 16 shown in Figures 1-6, the piston 16 includes two oil exhaust ducts 56 disposed between the two concave pin boss portions 42. Alternatively, the piston 16 may include more or less than two oil exhaust ducts 56. Alternatively or additionally, the oil exhaust ducts 56 shown may be separated such that each oil exhaust duct 56 is divided into two separate oil exhaust ducts which may be spaced apart from each other along the circumferential direction of the piston 16.

[0039] As can be gathered from figure 2, the two oil exhaust ducts 56 are arranged on opposite sides of the piston 16. In particular, the two oil exhaust ducts 56 are arranged opposite each other with respect to both the longitudinal axis L and the pin bore axis P of the piston 16.

[0040] Each of the oil drain ducts 56 is formed by a recess provided in the outer surface of the piston skirt 24. In other words, the oil drain ducts 56 are machined, in particular cut, into the outer surface of the piston skirt 24, in particular into the cylindrical portion 50 located adjacent the concave pin boss portion 42 of the piston skirt 24.

[0041] The oil discharge duct 56 is designed such that its flow cross section tapers along the flow direction of the oil in the oil discharge duct 56. In Figures 2 to 6 the flow direction of the oil guided through the oil discharge duct 56 is indicated by the arrow A. As can be deduced from the indicated flow direction, the flow path of the oil guided through the oil discharge duct 56 can be smoothly deflected downwards, i.e. in the direction of the downward movement direction.

[0042] In short, in the proposed configuration of the piston 16, the flow direction of the oil discharged along the outer surface of the piston skirt is smoothly deflected downward when flowing through the oil discharge duct 56. Specifically, by locating the oil discharge duct 56 between the concave pin boss portions 42, the oil discharge duct 56 has a certain length that can contribute to smoothly deflect the oil flow when passing through the oil discharge duct 56, thereby improving the return flow of the oil, especially when the piston 16 is adopted in a V-type engine.

[0043] Specifically, to ensure an adequate length for the oil drain duct 56 , the oil drain duct 56 extends along the entire circumferential length of the cylindrical portion 50 of the piston skirt 24 .

[0044] The structural arrangement and characteristics of the oil drain duct 56 are further defined below.

[0045] 2 to 4, each of the oil drain ducts 56 comprises a lower edge 58 arranged on the outer surface of the piston skirt 24. The lower edge 58 extends between the two concave pin boss portions 42, whereby the associated oil drain duct 56 opens into the concave pin boss portion 42. As can be gathered from FIG. 2, the lower edge 58 is designed such that in the flow direction of the oil guided through the oil drain duct 56, the lower edge 58 is curved, i.e. smoothly curved, downwards, i.e. in the downward movement direction.

[0046] In particular, as can be gathered from Figures 3 and 4, the oil discharge duct 56 is designed such that it is guided in the downward direction of movement, i.e. parallel to the longitudinal axis L of the piston 16, towards the crankshaft 14, with a middle section 60 of the lower edge 58 being arranged in front of two opposite end sections 62 of the lower edge 58. In other words, when viewed from the downward direction of movement, the middle section 60 is arranged in front of the two opposite end sections.

[0047] More specifically, as can be gathered from Fig. 2, each of the oil discharge ducts 56 is designed such that, in the mounted condition of the piston 16 in the engine 10, a middle section 60 of the lower edge 58 is located in front of two opposing end sections 62 of the lower edge 58 when viewed from below along the vertical axis Z of the engine 10. In other words, the discharge ducts 56 are designed such that, in the mounted condition of the piston 16 in the engine 10, the end sections 62 of the lower edge 58 are located below the middle section 60 of the lower edge 58. For the purposes of illustrating this structural arrangement, a horizontal plane H is shown in Fig. 2 with a dashed line.

[0048] Alternatively, the oil discharge ducts 56 may be designed such that, when viewed from below along the vertical axis Z of the engine 10, the middle section 60 of the lower edge 58 is located at the same level as two opposing end sections 62 of the lower edge 58. Furthermore, in the mounted state, each of the oil discharge ducts 56 is designed such that the lower edge 58 is curved downward relative to the horizontal plane H. Alternatively, the oil discharge ducts 56 may be designed such that the lower edge 58 is located and extends parallel to the horizontal plane H.

[0049] By providing the oil discharge duct 56, the structural arrangement and mounting conditions of the piston 16 in a V-engine are taken into account by the proposed piston configuration. In particular, even if the piston 16 is arranged at an angle to the vertical axis Z of the engine 10, i.e. due to the bank angle of the V-engine, the proposed oil discharge duct 56 can avoid that the oil discharged from the oil discharge groove 54 into the crankcase is deflected upwards, i.e. against gravity, by the lower edge 58 when it is guided across the outer surface of the piston skirt 24.

[0050] As noted above, in an alternative configuration, each of the oil drain ducts 56 may be separated or split into two separate oil drain ducts. In such a configuration, the drain duct may have a lower edge having a first end section opening into the recessed pin boss portion 42 and a second end section opening into the oil drain groove 54. In this configuration, the technical features described in this disclosure in relation to the mid section 60 may also apply to the inner and outer ends, particularly with respect to structural arrangements, and are therefore disclosed. Accordingly, the technical features described above in relation to the end section 62 may also apply to the second end section, and are therefore disclosed.

[0051] Additionally, each of the oil exhaust ducts 56 includes two opposing lateral edges 64 which, together with the lower edge 58, bound the flow path of the oil through the oil exhaust duct 56. The lateral edges 64 are disposed on the outer surface of the piston skirt 24. Specifically, each of the lateral edges 64 extends along the longitudinal axis L of the piston 16 between the oil exhaust groove 54 and one of the recessed pin boss portions 42. In this manner, the flow cross section of the oil exhaust duct 56 tapers in the flow direction A of the oil through the oil exhaust duct 56.

[0052] In the configuration shown, the lower edge 58 has a parabolic shape. Alternatively, the lower edge 58 can have a splint shape, so that the lower edge 58 can lie generally in a plane.

[0053] Specifically, the shape of the lower edge 58 of the oil drain duct 64 is parameterized by the following equation:

number

[0054] It will be apparent to those skilled in the art that these embodiments and items are merely examples illustrating multiple possibilities. Therefore, the embodiments shown herein should not be understood to form limitations on these features and configurations. Any possible combination and configuration of the described features can be selected according to the scope of the present invention.

[0055] This applies in particular with regard to the following optional features, which may be combined with some or all of the above-mentioned embodiments, items and / or features in any combination that is technically feasible.

[0056] There may be provided a piston for an internal combustion engine, in particular a V-engine, comprising an oil drainage groove provided in an outer peripheral surface of the piston between a ring belt of the piston and a piston skirt, the piston skirt comprising two concave pin boss portions on opposing sides of the piston, the piston skirt further comprising at least one oil drainage duct disposed between the two concave pin boss portions on the outer surface of the piston skirt and configured to fluidly connect the oil drainage groove with the concave pin boss portions.

[0057] In other words, according to such configuration, the proposed oil drain duct is preferably configured to drain oil from the oil drain groove into the crankcase of the engine when the piston operates within the engine, guiding the oil through the oil drain duct and subsequently along the outer surface of the concave pin boss portion.

[0058] By providing the proposed oil drain duct, a proper return of the oil from the ring belt into the crankcase can be ensured. In particular, the proposed configuration makes it possible to provide the oil drain duct with a suitable length for defining a flow path for the oil, which may experience a relatively low flow resistance when flowing through the flow path, for example by reducing oil splashing or by avoiding diverting the oil upwards against gravity.

[0059] The proposed piston is adapted for use in any suitable internal combustion engine, in particular a reciprocating engine, serving as a main or auxiliary engine in a vehicle, ship or power plant. In particular, the proposed piston can be used in a V-engine, but is not limited to this application. Such engines may run on liquid fuels, such as diesel or gasoline, or on gaseous fuels.

[0060] The proposed piston may have a multi-part design, for example a two-part design in which the piston head and the piston skirt, which house the ring belt, constitute separate parts, or alternatively, the piston may have a one-piece design, in which the piston is a single-piece casting.

[0061] As mentioned above, the piston skirt comprises concave pin boss portions arranged on mutually opposing sides of the piston skirt. The concave pin boss portions thus form the shell surface of the piston skirt. Furthermore, the piston skirt comprises two opposing cylindrical portions, each of which is adjacent to and arranged between the concave pin boss portions. When comparing the concave pin boss portion and the cylindrical portion of the piston skirt, the diameter of the piston, i.e. the diameter extending between the concave pin boss portions across its longitudinal axis, is smaller compared to the diameter extending between the cylindrical portions. In this way, when received in the cylinder of the engine, a gap is formed between the pin boss portion and the cylinder wall, into which the oil discharge duct opens, through which the oil flowing through the oil discharge duct is guided into the crankcase of the engine.

[0062] In particular, the outer surface of the pin boss portion, which forms the outer surface of the piston skirt, may be planar. Alternatively or additionally, the outer surface of the pin boss portion may be provided such that it does not extend beyond a plane in the radial direction of the piston, i.e., transverse to its longitudinal axis. The plane may be disposed parallel to the longitudinal axis and may be an imaginary plane. In such a configuration, the outer surface may comprise one or more recesses extending in a direction opposite to the radial direction of the piston.

[0063] The piston skirt may be provided with at least one oil drainage duct. In a further development, the piston skirt may be provided with at least two oil drainage ducts arranged between two concave pin boss portions on mutually opposing sides of the piston.

[0064] In particular, the at least one oil drainage duct may be formed by a recess provided in the outer surface of the piston skirt, in other words the at least one oil drainage duct may be cut into the outer surface of the piston skirt.

[0065] In a further development, the oil exhaust duct can be designed such that its flow cross section tapers along the direction of oil flow in the oil exhaust duct when the piston is mounted and operating in the engine.

[0066] Further, the oil drain duct may be disposed on an outer surface of the piston skirt and may have a lower edge extending between the two recessed pin boss portions such that the oil drain duct opens into at least one of the two recessed pin boss portions.

[0067] For example, the oil drain duct can be designed such that, in the direction of downward movement of the piston along the longitudinal axis of the piston, the middle section of the lower edge is located in front of or at the same level as the two opposing end sections of the lower edge.

[0068] In a further development, in the mounted condition of the piston in the engine, in particular in a V-engine, the oil exhaust duct can be designed in such a way that in the downward direction along the vertical axis of the engine, the middle section of the lower edge is located in front of or at the same level as the two opposing end sections of the lower edge.

[0069] Additionally or alternatively, in the mounted state of the piston in an engine, in particular a V-engine, the oil drain duct may be designed such that its lower edge is curved downwards or runs parallel to a horizontal plane extending through the mid-section of the lower edge.

[0070] In a further development, the oil drain duct may further comprise two opposing lateral edges arranged on the outer surface of the piston skirt, each of which extends along the longitudinal axis of the piston between the oil drain groove and one of the concave pin boss portions.

[0071] Additionally or alternatively, the lower edge of the oil drain duct may have a parabolic or sprint shape.

[0072] In particular, the shape of the lower edge of the oil discharge duct is determined, at least in part, by:

number

[0073] Furthermore, it is possible to provide an internal combustion engine, in particular a V-engine, comprising at least one piston as described above.

[0074] Since the proposed internal combustion engine comprises a piston as described above, the technical features described in relation to the piston above are also relevant and may be applied to the proposed internal combustion engine, and vice versa. [Industrial Applicability]

[0075] With reference to the drawings and the accompanying description, a piston for an internal combustion engine, and an internal combustion engine, in particular a V-engine, equipped with such a piston is proposed. The proposed piston may replace a conventional piston and may function as a replacement part or an off-line installation part.

Claims

1. A piston (16) for an internal combustion engine (10), in particular a V-engine, comprising an oil drain groove (54) provided on an outer peripheral surface of the piston (16) between a ring belt (26) of the piston (16) and a piston skirt (24), the piston skirt (24) comprising two concave pin boss portions (42) on opposite sides of the piston (16); The piston skirt (24) further comprises at least one oil discharge duct (56) disposed between the two concave pin boss portions (42) on an outer surface of the piston skirt (24) and configured to fluidly connect the oil discharge groove (54) to the concave pin boss portion (42), the oil discharge duct (56) having a flow cross-section of the oil discharge duct (56) that tapers in a flow direction A of oil through the oil discharge duct (56).

2. 2. The piston of claim 1, having a multi-part design in which the piston head (22) and the piston skirt (24) constitute separate parts.

3. 3. The piston of claim 1 or 2, wherein the recessed pin boss portion (42) has a planar outer surface (52) that forms an outer surface of the piston (16).

4. 4. The piston of claim 1, wherein the oil exhaust duct is configured to exhaust oil from the oil exhaust groove into a crankcase of the internal combustion engine when the piston is operating within the internal combustion engine, the oil exhaust duct being configured to guide oil through the oil exhaust duct and subsequently along an outer surface of the concave pin boss portion.

5. 5. The piston according to claim 1, wherein the piston comprises at least two oil exhaust ducts (56) arranged between the two concave pin boss portions (42) on opposite sides of the piston (16).

6. A piston according to any one of the preceding claims, wherein the oil drainage duct (56) is formed by a recess in the outer surface of the piston skirt (24).

7. 7. The piston according to claim 1, wherein the oil exhaust duct (56) is arranged on the outer surface of the piston skirt (24) and has a lower edge (58) extending between the two concave pin boss portions (42) such that the oil exhaust duct (56) opens into at least one of the two concave pin boss portions (42).

8. 8. The piston according to claim 7, wherein the oil exhaust duct (56) is designed such that, in the direction of downward movement of the piston (16) along its longitudinal axis (L), a middle section (60) of the lower edge (58) is located in front of or at the same level as two opposing end sections (62) of the lower edge (58).

9. 9. A piston according to claim 8, wherein in a mounted state of the piston (16) in the internal combustion engine (10), the oil exhaust duct (56) is designed such that, in a downward direction along a vertical axis (Z) of the internal combustion engine (10), the intermediate section (60) of the lower edge (58) is located in front of or at the same level as the two opposing end sections (62) of the lower edge (58).

10. 10. The piston of claim 9, wherein in the mounted state of the piston in the internal combustion engine, the oil exhaust duct is designed such that the lower edge is curved downwards or extends parallel to a horizontal plane extending through the middle section of the lower edge.

11. 9. The piston of claim 8, wherein the oil exhaust duct (56) further comprises two opposing lateral edges (64) disposed on the outer surface of the piston skirt (24), each of which extends along the longitudinal axis (L) of the piston (16) between the oil exhaust groove (54) and one of the recessed pin boss portions (42).

12. A piston according to any one of claims 7 to 11, wherein the lower edge (58) of the oil exhaust duct (56) has a parabolic or splint shape.

13. The shape of the lower edge (58) of the oil drain duct (56) is determined, at least in part, by: [0010] 12. The piston of claim 8, wherein x represents a position along a pin boss axis (P) of the piston (16); y represents a position along a transverse axis transverse to the pin boss axis (P); z represents a position along a central longitudinal axis (L) of the piston (16); r represents a radius of the outer circumferential surface of the piston skirt (24) about the central longitudinal axis (L) of the piston; b is a parameter indicative of a height position of the mid section (60) of the lower edge (58) relative to the pin boss axis (P); c represents a coefficient; and i represents an index provided as a natural number.

14. An internal combustion engine (10), in particular a V-engine, comprising at least one piston (16) according to any one of the preceding claims.

Images