PISTON AND ENGINE SYSTEM USING IT

Abstract

A piston (22) for an internal combustion engine (12) comprises a piston skirt (64) and a piston crown (66) attached to the piston skirt. The piston crown includes a combustion surface (68) forming a piston rim (70) extending circumferentially around a piston central axis, and a combustion bowl (74). The combustion surface further forms a bowl rim (80) defining an overlap between the combustion bowl and the piston rim, and has a re-entrant surface (82) extending between the bowl rim and the bowl outer wall. The ratio between the maximum bowl dimension and the bowl opening dimension is approximately 1.10 to approximately 1.15.

Description

Technical field

[0001] The present disclosure relates generally to a piston for an internal combustion engine and in particular to a piston with combustion chamber bowl surfaces designed for highly efficient operation. State of the art

[0002] Internal combustion engines are used extensively worldwide for a variety of purposes, from powering vehicles and driving pumps and compressors to generating electrical power. Conventional internal combustion engines use a number of pistons that move back and forth within cylinder bores to rotate a crankshaft in response to a controlled combustion reaction, which creates a rapid rise in pressure and temperature to drive the pistons. For decades, engineers have explored a wide range of fuels, exhaust aftertreatment devices and technologies, and operating strategies in efforts to improve engine operation, reliability, and performance.

[0003] In recent years, research and development efforts have increasingly focused on developing pistons optimized for various applications.

[0004] Depending on the type of engine, a piston is typically designed with a specific combustion surface geometry intended to interact with flows of fuel, air, and / or exhaust gases during operation for various purposes, including optimizing emissions and / or efficiency, mitigating cylinder temperatures, and / or reducing mechanical wear or corrosion, and for various other purposes. It has been observed that seemingly minor changes in piston geometry can often have disproportionate effects on engine operation and performance, and that the results of varying any parameter related to piston geometry can often be quite unpredictable.Furthermore, adding or removing piston volume, particularly on the combustion surface, complicates piston design optimization and affects the geometric compression ratio, often necessitating further modifications to the piston or overall engine system design to maintain the desired compression ratio. Depending on the fuel type and a variety of operating parameters and performance targets, optimized piston designs can exhibit highly diverse geometries. One well-known piston is described in U.S. Patent No. 9,670,829 by Bowing et al. Brief description

[0005] In one aspect, a piston for an internal combustion engine comprises a piston skirt and a piston crown attached to the piston skirt. The piston crown includes a combustion surface, forming a piston rim that extends circumferentially around a piston central axis, and a combustion chamber bowl with a bowl base that extends radially outward from the piston central axis to a bowl outer wall. The combustion surface further forms a bowl rim that defines an overlap between the combustion chamber bowl and the piston rim, and has a re-entrant area that extends between the bowl rim and the bowl outer wall. The piston defines a bowl opening dimension at a first axial position of the bowl rim and a maximum bowl dimension at a second axial position of the bowl outer wall. The ratio of the maximum bowl dimension to the bowl opening dimension is approximately 1.10 to approximately 1.15.

[0006] In another aspect, a piston for an internal combustion engine comprises a crown section having a first axial end with a combustion surface, a second axial end with an oil channel surface, and an outer crown surface extending between the first and second axial ends, which has a plurality of annular grooves formed therein. The combustion surface forms a piston rim extending circumferentially around a piston central axis, a combustion chamber bowl with a bowl outer wall, a bowl bottom, and a bowl rim that defines an overlap between the piston rim and the combustion chamber bowl. The piston defines a bowl opening dimension at a first axial position of the bowl rim and a maximum bowl dimension at a second axial position of the bowl outer wall. The ratio of the maximum bowl dimension to the bowl opening dimension is approximately 1.10 to approximately 1.15.

[0007] In another aspect, an internal combustion engine system comprises an engine block with a cylinder bore formed within it, a cylinder head, and a piston that moves within the cylinder bore between bottom dead center (BDC) and top dead center (TDC) positions. The piston includes a piston crown with a combustion surface forming a piston skirt that extends circumferentially around a piston axis, and a re-enclosing combustion bowl. The piston defines a bowl opening dimension and a maximum bowl dimension, and the ratio of the maximum bowl dimension to the bowl opening dimension is between approximately 1.10 and approximately 1.15. Brief description of the drawings Fig. Figure 1 is a schematic view of an internal combustion engine system according to one embodiment; and Fig. Figure 2 is a cutaway, schematic side view of a piston according to one embodiment. Detailed description

[0008] With reference to Fig. Figure 1 shows an internal combustion engine system 10 according to one embodiment. The engine system 10 comprises an internal combustion engine 12 with an engine housing or cylinder block 14 and an engine head 16 attached to the cylinder block 14. An internal combustion cylinder 18 is formed in the cylinder block 14, which can be one of a plurality of internal combustion cylinders formed therein. Although in Fig. Since only a single cylinder and the associated hardware are shown in Figure 1, it is understood that the internal combustion engine system 10 is generally a multi-cylinder engine, and the present description and discussion of any single component of the engine system 10 is to be understood as referring by analogy to other similar components of the engine system 10. Internal combustion cylinders in cylinder block 14 can comprise any number of cylinders in a suitable arrangement, such as an inline arrangement, a V-arrangement, or any other.

[0009] A cylinder liner 20 is arranged within the cylinder block 14, and a piston 22 is movable within the cylinder 18 in a generally accepted manner between a bottom dead center (BDC) position and a top dead center (TDC) position. Engine 12 is typically, but not necessarily, configured for operation in a four-stroke engine cycle. Piston 22 is coupled to a connecting rod 24, which in turn is coupled to a crankshaft 26. An oil sprayer 28 may be positioned to spray cooling and lubricating oil onto the underside of piston 22 and into an oil passage located therein, also in a generally accepted manner.

[0010] Engine system 10 also includes an intake system 30. Intake system 30 includes an intake duct 32, which is configured to direct intake air for combustion to cylinder 18. Intake system 30 also includes an intake manifold 40 and an intake port 41, which extends from intake manifold 40 to an intake port 43 that supplies cylinder 18. Experts in the field will understand that an intake manifold would normally be coupled to a plurality of intake ports, each extending to one of a plurality of cylinders. Engine system 10 also includes a turbocharger 34 with a compressor 36, which is arranged to pressurize an incoming intake airflow in response to the rotation of a turbine 38. Engine system 10 also includes an exhaust manifold 42, which is configured to receive an exhaust flow from cylinder 18 and direct it via an exhaust port 44 to turbine 38.

[0011] Engine system 10 also includes a fuel inlet valve 48 arranged to allow a fuel flow from a fuel supply 46 to intake port 32. The illustrated arrangement will be recognized as a premixed fuel inlet arrangement. In other cases, engine system 10 may have indirect injection, including a fuel injector extending into or near the intake port 43, or port fuel injection. It is assumed that engine system 10 is typically operated with a gaseous fuel, such as natural gas. Natural gas or other gaseous fuels may be supplied from a pressurized fuel tank, a gas pipeline, a mine, or various other sources.Engine system 10 can also be operated with various fuel mixtures, including natural gas and gaseous molecular hydrogen, or with various other gaseous hydrocarbon fuels and mixtures such as methane, ethane, biogas, landfill gas or others.

[0012] An intake valve 52 is mounted in the engine head 16 and is shown to be movable, opening or closing a fluid connection between the intake port 43 and the cylinder 18. Similarly, an exhaust valve 54 selectively connects the cylinder 18 to the exhaust manifold 42. In a typical application, a total of two intake valves and two exhaust valves can be provided for each cylinder of an engine. The engine system 10 can also be spark-ignited and includes a spark plug 56, which is arranged to extend through the engine head 16 into the cylinder 18 to generate an electric spark for igniting a fuel-air mixture in the cylinder 18. The spark plug 56 can be electrically connected to an electronic control unit 58 or another suitable electrical or magnetic device for generating a spark at a spark gap in the cylinder 18.In other implementations, a pre-chamber spark plug could be used, which provides a pre-chamber within cylinder 18 or in fluid communication with it to ignite a pre-chamber charge that ignites a main charge of fuel and air in cylinder 18 according to known principles. With reference now also made to... Fig. 2. Features of piston 22 are described in more detail below. Piston 22 comprises a piston skirt 64 formed on a piston skirt section 65, and a piston crown 66 or crown section (hereinafter referred to as "piston crown 66") attached to the piston skirt 64. Piston crown 66 comprises a combustion surface 68, forming a piston rim extending circumferentially around a piston central axis 72, and a combustion chamber recess 74. The combustion chamber recess 74 comprises a recess base 76 extending radially outward from a piston central axis 72 to a recess outer wall 78. The piston crown 66 further comprises a first axial end 88 with a combustion surface 68 and a second axial end 90 with an oil channel surface 92. The oil channel surface 92 forms an oil channel 93, which is arranged partly within the shaft piece 65 and partly within the piston crown 66, lies radially outside the combustion chamber recess 74 and extends circumferentially around the piston central axis 72.Piston base 66 further comprises an outer crown surface 94, which extends between first axial end 88 and second axial end 90 and has a plurality of piston ring grooves 96 formed therein, which extend circumferentially around piston central axis 72.

[0013] The combustion chamber bowl 74 comprises a bowl base 76 extending radially outward from a piston center axis 72 to a bowl outer wall 78. The bowl outer wall 78 may have a curved surface 98. The combustion surface 68 further forms a bowl rim 80, which defines an intersection of the combustion chamber bowl 74 and the piston rim 70, and has a re-entrant surface 82 extending between the bowl rim 80 and the bowl outer wall 78. In a practical implementation, the re-entrant surface 82 extends from the bowl rim 80 to the bowl outer wall 78, and the re-entrant surface 82 and the oil channel 93 may overlap at least partially in axial extent. The re-entrant surface 82 may include a conical re-entrant surface extending from the bowl rim 84 to a first transition 100 with the bowl outer wall 78 at a first axial transition point.The outer wall of the trough 78 can extend from the first transition 100 to a second transition 102, with the bottom of the trough 76 at a second axial transition point.

[0014] In the illustrated embodiment, the bowl base 76 is convex relative to the combustion chamber bowl 74, the bowl outer wall 78 is concave relative to the combustion chamber bowl 74, and the piston edge 70 is flat. The bowl outer wall 78 can define a radius of curvature between the bowl base 76 and the re-entering surface 82. In some embodiments, the radius of curvature defined by the bowl outer wall 78 can be approximately 10 millimeters. Fig. Figure 2 further illustrates a pivot pin bore 104 formed and structured in piston skirt 64 to accommodate a pivot pin in a generally conventional manner. The piston crown 66 and piston skirt 64 may comprise separate parts formed, for example, by a friction welding process such as inertial welding, although the present disclosure is not limited by this. The piston 22 may be formed entirely of steel or another ferrous material, or, in some embodiments, of aluminum.

[0015] Piston 22 further defines a cavity opening dimension 84 at a first axial position of cavity rim 80 and a maximum cavity dimension 86 at a second axial position of cavity outer wall 78. The ratio of maximum cavity dimension (86) to cavity opening dimension (84) can be between approximately 1.10 and approximately 1.15. In a refinement, the ratio of maximum cavity dimension 86 to cavity opening dimension 84 can be between approximately 1.11 and approximately 1.13, particularly approximately 1.12. In a practical implementation strategy, maximum cavity dimension 86 can be approximately 119 millimeters, and cavity opening dimension 84 can be approximately 106 millimeters. As mentioned above, cavity opening dimension 84 is defined at a first axial position of cavity rim 80.The piston rim 70 can extend planarly from the outer surface 94 to the bowl rim 80, such that the piston rim 70 terminates radially inward at the bowl rim 80 and defines a boundary plane perpendicular to the piston central axis 72 at the first axial position, the boundary plane encompassing the bowl opening dimension 84. A first depth dimension 110, coinciding with the piston central axis 72, is defined between the boundary plane and the axial position of the transition 100. A second depth dimension 112, also coinciding with the piston central axis 72, is defined between the axial position of the transition 100 and the bowl floor 76. The first depth dimension 110 can be larger than the second depth dimension 112. In other words, the transition 100 can be located closer to an axially highest point of the bowl floor than to the boundary plane.

[0016] It should also be noted that the maximum bowl dimension 86 is defined at a radially outermost end of the bowl's outer wall 78. A distance 108, which coincides with the piston's central axis 72, but in Fig. Figure 2, shown radially offset from the piston center axis for clarity, is defined between the second axial position of the outer wall of the combustion chamber, 78, where the maximum combustion chamber dimension 86 is defined, and the base of the combustion chamber, 78. In other words, the base of the combustion chamber, 78, although usually convex, is axially spaced below an axial position where the combustion chamber is widest.

[0017] In Fig. Figure 2 shows piston 22 as it might appear in the TDC position near the cylinder head 16. A clearance 120 is defined between piston rim 70 and cylinder head 16, which in a practical application can be approximately 4 millimeters. A dead space 114 is defined between combustion surface 68 and cylinder head 16. In one embodiment, the dead space 114 can be approximately 356 cubic centimeters. The volume of a combustion chamber bowl can be approximately 252 cubic centimeters. As mentioned above, combustion surface 68 defines bowl opening dimension 84. The bowl opening area of ​​a circle having bowl opening dimension 84 as its diameter can be approximately 88 square centimeters. The ratio of bowl opening area to a clearance, defined as the sum of the bowl opening area and the piston rim area defined by piston rim 70, can be between approximately 0.38 and approximately 0.45. In a refinement, the ratio of trough opening area to free space can be approximately 0.39.A similar relationship can exist between the bowl opening area and the cross-sectional area of ​​cylinder bore 18, although the cross-sectional area of ​​cylinder bore 18 may be somewhat larger than the sum of the bowl opening area and the piston skirt area. Fig. Number 1 represents a cylinder bore diameter shown at number 60. Fig. Figure 2 also illustrates an entry angle 106, defined between piston edge 70 and re-entering surface 82. Entry angle 106 can be approximately 70 degrees or less and, in a refinement, is approximately 67 degrees. Commercial applicability

[0018] It has been observed that turbulence in the flow of fluids within a combustion cylinder can be associated with performance improvements in certain engine designs and operating strategies. In the case of engine system 10, which uses piston 22, the relatively small clearance between the piston surface (piston rim 68), in conjunction with the relatively large radial width of the rim, which results at least in part from the maximum diameter of the combustion chamber bowl to the opening diameter, provides a rapid compression rate. In other words, the relatively large but shallow clearance allows for improved acceleration of the gases compared to what might be observed with a relatively large clearance and / or a narrower piston rim.During operation and at top dead center (TDC), the rapidly compressed fuel and air flow over the edge 80 of the combustion chamber bowl and enter the combustion chamber bowl 74 in a turbulent flow. In conjunction with some or all of the other parameters of the piston 22 described herein, depending on the specific embodiment, the described phenomenon can be expected to promote a faster flame velocity and high combustion efficiency. These properties are implemented without any geometric modifications that would undesirably affect the relatively high geometric compression ratio of the engine system 10, which in some embodiments may be greater than 14:1, for example, approximately 14.7:1. Certain dimensions and proportions are described herein using the term "approximately".The term "approximately" can be understood as generally or roughly significant, as it would be understood by an expert in the field of engine and piston design, for example, by approximation, convention, or conventional rounding to a consistent number of significant figures. According to the latter, "approximately 0.3" is understood to be a value between 0.25 and 0.34. "Approximately 0.32" means between 0.315 and 0.324, and so on. A dimension or proportion listed without a preceding relative term can be understood as the dimension or proportion within the margin of error.

[0019] The present description serves only for illustration and should not be interpreted as limiting the scope of this disclosure in any way. Those skilled in the art will therefore appreciate that various modifications to the embodiments disclosed herein could be made without deviating from the intended and appropriate meaning and scope of this disclosure. Other aspects, features, and advantages will become apparent upon examination of the accompanying drawings and attached claims. As used herein, the articles "one" are intended to include one or more elements and can be used interchangeably with "one or more." When only one element is intended, the term "one" or similar language is used. Similarly, the terms "comprising," "incorporating," "comprising," or the like are meant to be open-ended.Furthermore, the expression “based on” shall mean “at least partly based on” unless explicitly stated otherwise. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] US 9,670,829

[0004]

Claims

[1] Piston (22) for an internal combustion engine (12), comprising: a piston shaft (64); a piston base (66) which is attached to the piston stem and comprises a combustion surface (68) which forms a piston rim (70) which extends circumferentially around a piston central axis, and a combustion chamber recess (74) with a recess base (76) which extends radially outwards from the piston central axis to a recess outer wall (78); the combustion surface further forming a bowl edge (80) which defines an overlap of the combustion chamber bowl and the piston edge and having a re-entrant surface (82) which extends between the bowl edge and the bowl outer wall; the piston defining a bowl opening dimension at a first axial position of the bowl edge and a maximum bowl dimension at a second axial position of the bowl outer wall; and a ratio of the maximum trough dimension to the trough opening dimension of approximately 1.10 to approximately 1.

15. [2] Piston according to claim 1, wherein the ratio is about 1.11 to about 1.

13. [3] Piston according to claim 1 or 2, wherein the maximum cavity dimension is about 119 millimeters and the cavity opening dimension is about 106 millimeters. [4] Piston according to one of claims 1-3, wherein: the bowl floor is convex compared to the combustion chamber bowl, the bowl outer wall is concave compared to the combustion chamber bowl, and the piston edge is flat; a distance (108) which coincides with the piston center axis is defined between the second axial position and the bottom of the recess. [5] Piston according to any one of claims 1-4, wherein: an oil channel (93) is formed radially outside the combustion chamber recess and extends circumferentially around the piston's central axis; and The re-entering surface and the oil channel overlap in axial extent. [6] Piston according to any one of claims 1 to 5, wherein the re-entrant surface is conical and the outer wall of the bowl defines a radius of curvature between the bowl floor and the re-entrant surface; and wherein an angle of entry of about 70 degrees or less is defined between the re-entrant surface and the piston edge and the total radius of curvature is about 10 millimeters. [7] Piston according to one of the preceding claims, wherein the combustion surface defines a bowl opening area and a piston edge area and the ratio of the bowl opening area to a gap area defined as the sum of the bowl opening area and the piston edge area is approximately 0.38 to approximately 0.

45. [8] Piston according to claim 7, wherein the ratio of the bowl opening area to the gap area is approximately 0.

39. [9] Piston (22) for an internal combustion engine (12), comprising: a crown piece (66) including a first axial end (88) having a combustion surface (68), a second axial end (90) having an oil channel surface (92) and an outer crown surface (94) extending between the first axial end and the second axial end and having a plurality of annular grooves (96) formed therein; the combustion surface forming a piston rim (70) which extends circumferentially around a piston central axis, a combustion chamber bowl (74) with a bowl outer wall (78), a bowl bottom (76) and a bowl rim (80) which defines an overlap of the piston rim and the combustion chamber bowl; the piston defining a bowl opening dimension at a first axial position of the bowl edge and a maximum bowl dimension at a second axial position of the bowl outer wall; and a ratio of the maximum trough dimension to the trough opening dimension of approximately 1.10 to approximately 1.

15. [10] Piston according to one of claim 9, wherein: the combustion surface further comprises a conical, re-entrant surface (82) which extends from the rim of the trough to a transition (100) with the outer wall of the trough, which is arranged axially between the first axial position of the rim of the trough and the second axial position of the outer wall of the trough; a boundary plane perpendicular to the piston central axis is defined by the piston edge and includes the recess opening dimension; a first depth dimension, which coincides with the piston's central axis, is defined between the boundary plane and an axial position of the transition; a second depth dimension, which coincides with the piston's central axis, is defined between the axial position of the transition and the bottom of the recess; and the first depth dimension is larger than the second depth dimension. [11] Piston according to claim 10, wherein the conical re-entrant surface and the oil channel surface overlap in axial extent. [12] Piston according to claim 10 or 11, wherein the ratio is about 1.

12. [13] Piston according to one of claims 10-12, wherein the combustion surface defines a bowl opening area and a piston edge area and the ratio of the bowl opening area to a gap area defined as the sum of the bowl opening area and the piston edge area is approximately 0.38 to approximately 0.

45. [14] Internal combustion engine system (10), comprising: an engine housing (14) with a cylinder bore (18) formed therein; a motor head (16); a piston (22) which is movable within the cylinder bore between a bottom dead center (BDC) position and a top dead center (TDC) position; the piston comprising a piston crown (66) with a combustion surface (68) forming a piston rim (70) extending circumferentially around a piston central axis, and a re-enclosing combustion chamber recess (74); and the piston defining a bowl opening dimension and a maximum bowl dimension and a ratio of the maximum bowl dimension to the bowl opening dimension being between approximately 1.10 and approximately 1.

15. [15] Internal combustion engine system according to claim 14, wherein: A dead space is defined between the combustion surface and the engine head, and the ratio between the combustion chamber bowl volume and the dead space is approximately 0.71; a ratio of combustion chamber opening area to bore area of ​​cylinder bore is approximately 0.39; the combustion surface further comprises a conical, re-entrant surface (82) which extends from the rim of the trough to a transition (100) with the outer wall of the trough, which is arranged axially between the first axial position of the rim of the trough and the second axial position of the outer wall of the trough; a boundary plane perpendicular to the piston central axis is defined by the piston edge and includes the recess opening dimension; a first depth dimension, which coincides with the piston's central axis, is defined between the boundary plane and an axial position of the transition; a second depth dimension, which coincides with the piston's central axis, is defined between the axial position of the transition and the bottom of the recess; and the first depth dimension is larger than the second depth dimension.

Images