Piston of an internal combustion engine having a valve sleeve step for slowing the flow of combustion gases

Abstract

A piston for an internal combustion engine includes a plurality of valve sleeves formed in the piston rim, the valve sleeves forming fluid flow paths through the piston rim. Each valve sleeve includes a central step projecting from the sleeve bottom plate to restrict the fluid flow area through the sleeve and the flow of combustion gases slowed from the combustion bowl towards the cylinder liner, thereby reducing the displacement of the engine oil film thereon.

Description

Technical Field

[0001] The present invention generally relates to a piston for an internal combustion engine and, more particularly, to a valve sleeve in a piston edge configured to slow the flow of combustion gases from a combustion bowl to a cylinder liner. Background Art

[0002] A variety of operating strategies and component geometries are known in the field of internal combustion engines. For decades, engineers have been experimenting with different ways of operating the fuel supply, exhaust, intake, and other engine systems, as well as changing the shape and proportions of engine components for various purposes. One of the motivations behind this experimentation is to balance the often competing interests of reducing certain emissions in the engine exhaust and optimizing efficiency. The exhaust produced by the combustion of fuel and air in an internal combustion engine includes various compounds such as soot, ash, unburned hydrocarbons, water, carbon dioxide, and carbon monoxide, as well as other organic and inorganic substances.

[0003] Certain internal combustion engine configurations attempt to tightly control the functional and spatial relationships between components at various points during the engine cycle. For example, when the piston is at the top dead center position in the engine cycle, a volume generally referred to as "squeeze" extends between the top surface of the piston edge and the hearth surface of the engine head. For various reasons, it is desirable for the squeeze volume in the engine to be very small. Since the piston can be close to the engine valves at the top dead center position and, in some cases, there is a risk of collision with the engine valves at the top dead center position by design or otherwise, some pistons are formed with valve sleeves in the piston edge. The valve sleeve can accommodate an engine valve that is open or partially open at the top dead center position of the piston without the risk of actual collision. Since the presence or absence of the valve sleeve and the specific valve sleeve configuration can affect factors such as the geometric compression ratio and the squeeze volume, changes in the piston design that surround or affect the valve sleeve geometry can sometimes have a significant impact on engine performance or emissions, or these effects may be unpredictable. A known piston with a valve sleeve is proposed in U.S. Patent Application Publication No. 2013 / 0319372A1 to Gladden et al. Summary of the Invention

[0004] In one aspect, an engine includes a cylinder block having a cylinder liner positioned therein and forming a combustion cylinder. The engine further includes: a cylinder head having gas exchange passages formed therein; and a fuel injector supported in the cylinder head and including a fuel spray hole positioned within the combustion cylinder. The engine further includes an engine valve supported for reciprocation in the cylinder head and movable from a closed position to an open position to fluidly connect the gas exchange passages to the combustion cylinder. A piston is positioned within the combustion cylinder and movable between a bottom dead center position and a top dead center position to increase fluid pressure within the combustion cylinder to an autoignition threshold. The piston includes a piston crown having a bowl surface forming a combustion bowl and a piston rim positioned radially outward of the combustion bowl and extending circumferentially about a piston central axis. A valve sleeve is formed in the piston rim and positioned to receive the engine valve when the engine valve is in the open position. The valve sleeve forms a fluid flow path through the piston rim and includes a valve sleeve bottom plate, and a central step that projects from the valve sleeve bottom plate and is positioned in the fluid flow path to slow the flow of combustion gases from the combustion bowl to the cylinder liner.

[0005] In another aspect, a piston for an internal combustion engine includes a piston body having a piston skirt and a piston crown attached to the piston skirt. The piston crown has a bowl surface forming a combustion bowl, and a piston rim positioned radially outward of the combustion bowl and extending circumferentially about a piston central axis and radially between the combustion bowl and an outer peripheral surface of the piston crown. A plurality of valve sleeves are formed in the piston rim. The plurality of valve sleeves form a fluid flow path through the piston rim, and each valve sleeve includes a valve sleeve bottom plate, a valve sleeve wall extending between the combustion bowl and the outer peripheral surface, and a central step. The central step projects from the valve sleeve bottom plate to limit a fluid flow area of a corresponding fluid flow path and includes an inner step wall and an outer step wall that is spaced from the valve sleeve wall and from the outer peripheral surface of the piston crown.

[0006] In yet another aspect, a piston crown for a piston in an internal combustion engine includes a piston crown body that defines a piston center axis extending between a first piston crown axial end and a second piston crown axial end that includes a combustion surface. The combustion surface includes a bowl surface that forms a combustion bowl, and a piston rim that is positioned radially outward of the combustion bowl and extends circumferentially about the piston center axis and radially between the combustion bowl and the outer peripheral surface of the piston crown. A plurality of valve sleeves are formed in the piston rim and are circumferentially distributed about the piston center axis to receive a plurality of engine valves in the internal combustion engine. The plurality of valve sleeves form a fluid flow path through the piston rim, and each valve sleeve includes a valve sleeve bottom plate and a valve sleeve wall that extends between the combustion bowl and the outer peripheral surface. At least one of the plurality of valve sleeves further includes a central step that is configured to restrict a fluid flow area of a corresponding fluid flow path. The central step protrudes from the valve sleeve bottom plate and includes a step top surface that is recessed relative to the piston rim. The central step further includes an inner step wall adjacent to the combustion bowl and an outer step wall that is spaced apart from the valve sleeve wall and from the outer peripheral surface of the piston crown. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a partial cross-sectional schematic view of an internal combustion engine system according to one embodiment;

[0008] Figure 2 is a cross-sectional side view schematic of a portion through an internal combustion engine according to one embodiment;

[0009] Figure 3 is a perspective view of a piston according to one embodiment;

[0010] Figure 4 is a cross-section through Figure 3 a portion of the piston;

[0011] Figure 5 is a perspective view of a piston according to another embodiment;

[0012] Figure 6 is a cross-section through Figure 3 and Figure 4 a portion of the piston;

[0013] Figure 7 is a perspective view of a piston according to another embodiment;

[0014] Figure 8 is a cross-section through Figure 7 a portion of the piston;

[0015] Figure 9 is a cross-section through Figure 7 and Figure 8 a portion of the piston;

[0016] Figure 10 is a schematic cross-sectional side view of a portion passing through a piston and an engine valve according to one embodiment;

[0017] Figure 11 is a schematic cross-sectional side view of a portion passing through a piston and an engine valve according to another embodiment; and

[0018] Figure 12 is a comparison chart of an internal combustion engine according to one embodiment compared to a known engine configuration. DETAILED DESCRIPTION

[0019] Referring to Figure 1 , an internal combustion engine system 10 is shown according to one embodiment. The internal combustion engine system 10 includes an engine 12 having a cylinder block 14 with a cylinder liner 16 positioned therein and forming a combustion cylinder 18. The engine 12 also includes a cylinder head 20 in which a plurality of gas exchange ducts 22 and 24 are formed. Both the gas exchange duct 22 and the gas exchange duct 24 may include an exhaust duct, an intake duct, or one of them. In the illustrated embodiment, the gas exchange duct 22 is an intake duct and the gas exchange duct 24 is an exhaust duct. A fuel injector 26 is supported in the cylinder head 20 and includes a fuel spray hole 28 positioned within the combustion cylinder 18 for direct fuel injection.

[0020] In an actual implementation strategy, the engine 12 includes a compression ignition diesel engine, where the cylinder liner 16 is one of a plurality of cylinder liners forming a plurality of combustion cylinders in any suitable arrangement. Thus, the description herein of the singular form of the combustion cylinder 18 and components associated with the singular form of the combustion cylinder 18 will be understood in a similar manner to refer to any one of the plurality of combustion cylinders or associated components that may be provided in the engine 12. The engine system 10 also includes an intake system 34, and the intake system 34 includes an intake inlet 36 configured to deliver intake air to an intake manifold 38. The engine system 10 may be turbocharged and may include Figure 1 a conventional turbocharger device not shown in

[0021] The engine 12 also includes a first engine valve 30 and a second engine valve 32, which are supported for reciprocating movement in the cylinder head 20 and are each movable from a closed position to an open position to fluidly connect the respective gas exchange ducts 22 and 24 to the combustion cylinder 18. The piston 48 is shown positioned in the combustion cylinder 18 and is movable between a bottom dead center position and a top dead center position generally as shown to increase the fluid pressure in the combustion cylinder 18 to an autoignition threshold. As further discussed herein, the piston 48 includes a valve sleeve 78 formed therein and configured to slow the flow of combustion gases to the cylinder liner 16 to limit displacement of the oil film on the inner wall of the cylinder liner 16 and thus limit unwanted heat transfer into the material of the cylinder liner 16.

[0022] Now also referring to Figures 2 - 4 , the features of the engine system 10 and the piston 48 are shown in more detail. The piston 48 includes a piston body 54 having a piston skirt 56 in which a wrist pin hole 57 is formed. As Figure 1 shown, the wrist pin hole 57 is configured to receive a wrist pin to couple the piston 48 to the crankshaft 50 via a connecting rod 52. The piston body 54 also includes a piston crown 58, which includes a crown body 61 attached to the piston skirt 56. The crown body 61 of the piston crown 58 defines a piston center axis 66 extending between a first piston crown axial end 70 and a second piston crown axial end 72, the first piston crown axial end 70 being attached to the piston skirt 56, for example, by friction welding, and the second piston crown axial end 72 including a combustion surface 59. The combustion surface 59 includes a bowl surface 60 forming a combustion bowl 62, and a piston edge 64 positioned radially outward of the combustion bowl 62 and extending circumferentially about the piston center axis 66. The piston edge 64 also extends radially between the combustion bowl 62 and the piston crown outer peripheral surface 68. A plurality of valve sleeves 78 and 79 are formed in the piston edge 64 and are configured to receive a plurality of engine valves 32 and 30 in the engine 12. The piston 48 also includes a central cone 74 formed by the bowl surface 60, and a plurality of ring grooves 76 formed in the piston crown outer peripheral surface 68. A plurality of separate top surface regions 81 of the piston edge 64 are alternately arranged with the valve sleeves 78 and 79 circumferentially distributed about the piston center axis 66.

[0023] In the illustrated embodiment, valve sleeve 78 includes an intake valve sleeve and valve sleeve 79 includes an exhaust valve sleeve. Embodiments can be envisioned where the intake and exhaust valve sleeves are the same within the piston. However, in other embodiments, there may be certain differences between the intake and exhaust valve sleeves, or even potentially between intake valve sleeves or between exhaust valve sleeves. Valve sleeves 78 and 79 form a fluid flow path through piston edge 64. Thus, it should be understood that any description and discussion herein of any one valve sleeve or its features is to be understood in a similar manner as referring to any other valve sleeve, unless otherwise specified or obvious from the context. Each valve sleeve 78 includes a valve sleeve base plate 80, a valve sleeve wall 82 extending between combustion bowl 62 and outer peripheral surface 68, and a central step 84. Valve sleeve 79 will be similarly understood to include a valve sleeve wall and a valve sleeve base plate (not numbered), and each valve sleeve includes a central step 85. In accordance with principles further discussed herein, each of central step 84 and central step 85 projects from the respective sleeve base plate 80 to limit and aerodynamically affect the fluid flow area of the respective fluid flow path. The effect on the fluid flow area can contribute to slowing the flow of combustion gases from combustion bowl 62 to cylinder liner 16.

[0024] Now also referring to Figure 4 , central step 84 includes an inner step wall 90 adjacent to combustion bowl 62, and an outer step wall 92 spaced from sleeve wall 82 and outer peripheral surface 68. Central step 84 further includes a step top surface 94 that is recessed in the axial direction relative to piston edge 64, particularly in the top surface area 81. As best shown in Figure 4 , piston edge 64 can have a curved profile that rises in the direction of outer peripheral surface 68 relative to sleeve base plate 80 in top surface area 81. Thus, step top surface 94 may not be recessed relative to all of piston edge 64, but rather is generally recessed relative to top surface area 81 at least in the radially outward region of combustion bowl 62.

[0025] It should be remembered that valve sleeves 78 and 79 can be the same, but can be different in some embodiments. Continuing to refer to Figure 3 , piston configurations can be envisioned in accordance with the present invention where multiple valve sleeves (including a first valve sleeve and a second valve sleeve) within the piston are constructed such that both the sleeve width and the central step width of the first valve sleeve are greater than the sleeve width and the central step width of the second valve sleeve. In Figure 3Among them, the first sleeve width of one of the valve sleeves 78 is shown at 86. The second valve sleeve width of one of the valve sleeves 79 is shown at 88. The first step width of one of the valve sleeves 78 is shown at 87. The second step width of one of the valve sleeves 79 is shown at 89. Although the differences in dimensions may be relatively small, for example, differing by about 5 millimeters or less, relevant different functions of the intake and exhaust exchange pipes can be achieved by accommodating the different dimensions and / or differences between the exhaust valve and the intake valve. In one exemplary embodiment, the sleeve width 86 of the valve sleeve 78 for the intake valve can be greater than the sleeve width 88 of the valve sleeve 79 for the exhaust valve. Similarly, the step width 87 can be greater than the step width 89. Those skilled in the art will recognize other possibilities of variations between and within the intake valve sleeve and the exhaust valve sleeve according to the present invention.

[0026] Now referring to Figure 5 , a piston 148 according to another embodiment is shown, which has certain similarities with the piston 48 but also has certain differences. The piston 148 includes a piston skirt 156 and a piston edge 164, in which two valve sleeves 178 and two other valve sleeves 179 are formed. Each of the valve sleeves 178 includes a sleeve bottom plate 180 and a central step 184. Each of the valve sleeves 179 includes a sleeve bottom plate 181 but no central step. In other words, the valve sleeve 179 can be stepless. The sleeve bottom plate 180 can be planar and interrupted by the central step 184. The sleeve bottom plate 181 can be uniformly planar and uninterrupted. Other embodiments can include a total of two valve sleeves, where one valve sleeve with a central step is formed in the piston edge, and one stepless valve sleeve is also formed in the piston edge. In the illustrated embodiment, the piston 148 is understood to have two stepless valve sleeves. The stepless valve sleeve 179 can be an exhaust valve sleeve, and the stepped valve sleeve 178 can be an intake valve sleeve. However, the present invention is not limited thereto and the opposite arrangement can be used.

[0027] Referring again to Figures 2 - 4 And now also referring to Figure 6 which shows additional details of the valve sleeve 78, the valve sleeve 78 can further include a first sleeve wall 82 and a second sleeve wall 83 having a mirror profile with respect to a radius line of a circle defined by the piston central axis 66. The mirror profile can be formed by a radially inward concave wall section 102 and a radially outward wall section 104 respectively. The radially outward wall section 104 can be convex, and the two radially outward wall sections 104 can together form an open throat 106 at the outer peripheral surface 68. An arc transition portion 108 is shown generally where the concave inner wall section 102 transitions to the outer wall section 104. The first sleeve wall 82 and the second sleeve wall 83 can further define an outer circle 110. The central step 84 further includes an outer step wall 92, which defines an inner circle 112 concentric with the outer circle 110. It can also be noted that as Figure 6As best shown, the sleeve walls 82 and 83 have a relatively smooth curved transition with the sleeve bottom plate 80 and a relatively sharp transition with the top surface region 81. As Figure 3 and Figure 6 shown, the first sleeve wall 82 can intersect the sleeve bottom plate 80 at the first contour line 118. In Figure 6 not visible but shown in Figure 3 the second sleeve wall 83 intersects the sleeve bottom plate 80 at the second contour line 120. The outer step wall 92 intersects the sleeve bottom plate 80 at the third contour line 122. The first contour line 118 and the second contour line 120 form an arc section of the outer circle 110. The third contour line 122 forms an arc section of the inner circle 112.

[0028] It has been found that the desired favorable fluid flow characteristics can be obtained, including slowing down the combustion gas flow without overly blocking its passage through the fluid flow path formed by the valve sleeve 78 and other valve sleeves discussed herein, where the ratio of certain features of the valve sleeve to the central step is within a general range. In one implementation, the diameter 114 of the inner circle 112 is from about 39% to about 80% of the diameter 116 of the outer circle 110. In Figure 6 the embodiment of, including the case where the sleeve bottom plate 80 is planar from the third contour line 122 to each of the first contour line 118 and the second contour line 120, the diameter 114 of the inner circle 112 can be from 60% to 64% of the diameter 116 of the outer circle 110. In a specific example, the diameter 116 can be about 45 millimeters, more specifically about 44.5 millimeters. The diameter 114 can be about 27 millimeters, more specifically about 27.0 millimeters. In another specific example, the diameter 116 can be 47 millimeters, more specifically about 47.0 millimeters, and the diameter 144 can be about 30 millimeters, more specifically 30.0 millimeters. The first specific example can be an exhaust valve, and the second specific example can be an intake valve. In other embodiments discussed below, the same general ratio has been found to be desirable.

[0029] Now referring to Figures 7 - 9 , a piston 248 according to another embodiment is shown. The piston 248 has many similarities with the above embodiment while having several differences. The piston 248 includes a piston skirt 256 and a piston top 258 including a piston edge 264. Two valve sleeves 278 are formed in the piston edge 264 and can include intake valve sleeves, each intake valve sleeve having a central step 284. Two additional valve sleeves 279 are formed in the piston edge 264 and can include exhaust valve sleeves, each exhaust valve sleeve having a central step 285. While in the above embodiment, the valve sleeve bottom plate can be uniformly planar, but for the central step, in Figures 6 - 9In an embodiment, the valve sleeve bottom plate 280 may have different configurations, for example, as further discussed herein, to accommodate engine valves of different shapes.

[0030] As Figure 9 shown, the valve sleeve 278 includes a sleeve wall 282 defining an outer circle 310 ( Figure 9 one of those shown in), wherein the central step 284 has an outer step wall defining an inner circle 312, hereinafter referred to as the descending ramp 298. The sleeve wall 282 intersects the sleeve bottom plate 280 at the contour line 318, and the step wall / ramp 298 intersects the sleeve bottom plate 280 at the contour line 322. The contour lines 318 and 322 respectively form arc segments of the outer circle 310 and the inner circle 312, generally similar to the above-described embodiments. The outer circle 310 has a diameter 316, and the inner circle 312 has a diameter 314. The outer circle 310 and the inner circle 312 may be concentric. The diameter 314 may be from about 39% to about 80% of the diameter 316. More specifically, the diameter 314 may be from 39% to 43% of the diameter 316. And in Figures 2 - 4 and the embodiments of 6, and in Figure 5 the embodiments of, the valve sleeve bottom plate may be planar from the third contour line to each of the first and second contour lines, including an inner planar region 285 defined by the third contour line 322 in the piston 248 of the bottom plate 280, an outer planar region 287 defined by the first contour line 318 (and Figure 9 similar defined contour lines of the sleeve wall not shown in), and a downwardly inclined region 289 extending between the inner planar region 285 and the outer planar region 287. The contour of the valve sleeve 278 may be such that the ascending ramp 296 extends radially outward from the combustion bowl 262 to the top 299, while the descending ramp 298 extends radially outward from the top 299 to the inner planar region 285. The valve sleeve 278 and other features of the valve sleeve 279 may generally be similar or identical to the features of the valve sleeve 278 and the other valve sleeves described above, including the contour of the sleeve wall 282 and the mirror image relationship of the sleeve wall.

[0031] In one specific example, diameter 316 can be approximately 48 millimeters, more specifically approximately 47.5 millimeters. Diameter 314 can be approximately 19 millimeters, more specifically approximately 18.7 millimeters. In another specific example, diameter 316 can be approximately 50 millimeters, more specifically approximately 50.0 millimeters, and diameter 314 can be approximately 29 millimeters, more specifically approximately 20.8 millimeters. The first specific example can be an exhaust valve and the second specific example can be an intake valve. In cases where the term "approximately" is used, the quantity concerned can be understood as generally or roughly equal to the value listed, for example such that "approximately 18.7" means 18.65 to 18.74 within the measurement error through conventional rounding. In other cases, depending on the context, the term "approximately" can have a broader or different meaning than conventional rounding. When the term "approximately" is not used, the quantity can be understood as equal to the value listed within the measurement error.

[0032] Now refer to Figure 10 , which shows an engine valve 32 near a piston 48. The engine valve 32 includes certain features that cooperate with the features of the piston 48. The engine valve 32 includes a valve stem 33 and an attached valve head 35. The valve head 35 includes a valve combustion surface 37. The outer peripheral surface 43 of the valve head 35 extends circumferentially around a valve center axis 39. The valve head 35 also includes a concave arcuate surface 45 that extends circumferentially around the valve center axis 39 and forms a recess 47 located at the center. A seat surface 51 is generally located opposite the valve combustion surface 37. The seat surface 51 can be conical and is configured to mate with a valve seat formed in, for example, a valve seat insert. An intermediate surface 53 extends circumferentially around the concave arcuate surface 45 and can be, for example, planar or conical. The valve head 35 also includes a raised ring 49. In the illustrated embodiment, the raised ring 49 is radially positioned between the concave arcuate surface 45 and the outer peripheral surface 43, centered on the valve center axis 39 and extending circumferentially around the valve center axis 39. The raised ring 49 is located radially outward of the intermediate surface 53. Embodiments can be envisioned where the valve combustion surface is a uniform plane. However, in the engine valve 32, the additional material formed by the raised ring 49 axially extends outwardly on the valve combustion surface 37 and can help obtain the desired thermal fatigue life characteristics of the engine valve 32. In at least some embodiments, the additional material of the raised ring 49 can be received within a valve sleeve 78 at the top dead center position of the piston 48.

[0033] Now refer to Figure 11, shows an engine valve 233 near the piston 248. The engine valve 233 includes certain features that cooperate with the features of the piston 448 and has a valve stem 233 and an attached valve head 235. The valve head 35 includes a combustion surface 237 and an outer peripheral surface 43 that extends circumferentially around the valve center axis 239. The valve head 235 also includes a concave arcuate surface 245 that extends circumferentially around the valve center axis 239 and forms a centrally located recess 247. The seat surface 251 is generally located opposite the valve combustion surface 237, can be conical and is configured to mate with a valve seat formed in, for example, a valve seat insert 253. The radially outward surface 253 extends circumferentially around the valve center axis 239, adjacent to the outer peripheral surface 243, and can be, for example, planar. The valve head 235 also includes a raised ring 249 that partially forms the combustion surface 237. In the illustrated embodiment, the raised ring 249 abuts the arcuate surface 245. In the corresponding Figure 10 and Figure 11 embodiments, the raised ring 49 and the raised ring 249 can have a circular cross-sectional shape, a planar or platform shape, or another shape, and can be positioned adjacent to a centrally located recess (if present), adjacent to the outer peripheral valve head surface, or between these positions.

[0034] Industrial Applicability

[0035] Generally referring to the drawings, but now specifically referring to Figure 12 , on the left hand side is shown an example of the flow of combustion gases through the piston 48 in the engine 12 via the arrow 130, as might occur when the piston 48 is at top dead center position, compared to an example of the flow of combustion gases through a conventional piston 448 in the engine via the arrow 430 on the right hand side, as might also occur at top dead center position. During engine operation, fuel can be injected at relatively high pressures including up to several hundred megapascals (MPa). Depending not only on the injection pressure, but also on factors such as the compression ratio, injection spray angle, injection timing, etc., and other factors, it has been observed that the plume of combusted fuel and air, and combustion products and potentially other gases (such as recirculated exhaust) can impact the cylinder liner in a manner that displaces and / or evaporates the oil film on the inner wall of the cylinder liner. As a result, the loss of the cooling and lubricating effect of the oil at these concentrated locations can lead to damage, degradation, or poor appearance of the cylinder liner.

[0036] From Figure 12As can be seen in the comparative view, the combustion gas flow 430 will generally pass unobstructed through the squeeze 432 between the engine valve 431 and the piston 448, thereby allowing the combustion gas to impact the inner wall of the cylinder liner 16 at a relatively high speed. The squeeze height associated with the piston 448 is shown at 434 and is generally uniform, resulting in a combustion gas velocity sufficient to overly displace the oil film. In contrast, in the case of the piston 48, the squeeze is shown at 132, and it can be noted that a relatively small squeeze height 134 is formed between the engine valve 32 and the center step 184, but a relatively large squeeze height 136 is formed between the engine valve 32 and the sleeve bottom plate 80.

[0037] The combustion of air and fuel in a compression ignition internal combustion engine is a violent and highly dynamic process with temperatures above 400 °C and even exceeding 600 °C, rapid temperature changes, and a relatively fast combustion gas flow velocity. In the case of the piston 48 and other pistons according to the present invention, it is expected that the combustion gas will flow around the center step in the valve sleeve and flow over and through the center step. Initially, when the combustion gas plume advances towards the outside of the combustion bowl, the flow area is blocked or throttled, but subsequently, when the combustion gas passes over the center step and begins to advance towards the outer peripheral surface of the piston, the flow area relatively expands, presumably causing the flow velocity to slow down. As a result, the velocity of the combustion gas flow tends to be less than the extent that would otherwise be expected to cause displacement and / or evaporation of the oil film on the inner wall of the cylinder liner and / or displacement or evaporation not compensated for by the fuel supply in use. The ratios and ranges disclosed herein are expected to provide practical applications where the effect on gas flow is at least sufficient to address oil film displacement and / or evaporation, but does not overly limit or otherwise modify the flow in a manner that affects other combustion objectives.

[0038] This specification is for illustrative purposes only and should not be construed as limiting the scope of the present invention in any way. Accordingly, those skilled in the art will understand that various modifications can be made to the presently disclosed embodiments without departing from the full and reasonable scope and spirit of the present invention. Other aspects, features, and advantages will become apparent by studying the drawings and the appended claims. As used herein, the articles "a" and "an" are intended to include one or more items and can be interchanged with "one or more." When only one item is desired, the term "one" or a similar expression is used. Additionally, as used herein, the terms "has," "have," "having," etc. are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "at least partially based on" unless otherwise expressly stated.

Claims

1. An engine, comprising: A cylinder block having a cylinder liner positioned therein and forming a combustion cylinder; A cylinder head having gas exchange ducts formed therein; A fuel injector supported in the cylinder head and including a fuel spray hole positioned within the combustion cylinder; An engine valve supported to reciprocate in the cylinder head and movable from a closed position to an open position to fluidly connect the gas exchange duct to the combustion cylinder; A piston positioned within the combustion cylinder and movable between a bottom dead center position and a top dead center position to increase the fluid pressure within the combustion cylinder to an auto-ignition threshold; The piston includes a piston crown and a piston rim, the piston crown having a bowl surface forming a combustion bowl, the piston rim positioned radially outward of the combustion bowl and extending circumferentially about a piston central axis; A valve sleeve formed within the piston rim and positioned to receive the engine valve when the engine valve is in the open position; And The valve sleeve forms a fluid flow path through the piston rim and includes a valve sleeve bottom plate, and a central step projecting from the valve sleeve bottom plate and positioned within the fluid flow path to slow the flow of combustion gases from the combustion bowl to the cylinder liner.

2. The engine according to claim 1, wherein: The valve sleeve further includes a first sleeve wall and a second sleeve wall having mirror-image profiles, each mirror-image profile formed by a radially inwardly concave wall section and a radially outwardly wall section; The engine valve includes a valve head having a seat surface and a combustion surface; The combustion surface is partially formed by a concave arcuate surface and a raised ring, the concave arcuate surface forming a centrally positioned recess, the raised ring extending circumferentially about the recess and being received within the valve sleeve when the piston is in the top dead center position; The piston crown includes an outer peripheral surface, the radially outwardly wall section is raised and together forms an open throat at the outer peripheral surface; The first sleeve wall and the second sleeve wall define an outer circle, the central step includes an outer step wall, the outer step wall defining an inner circle concentric with the outer circle; And The diameter of the inner circle is 39% to 80% of the diameter of the outer circle.

3. The engine according to claim 2, wherein: The first sleeve wall intersects the sleeve bottom plate at a first contour line and the second sleeve wall intersects the sleeve bottom plate at a second contour line, and the outer step wall intersects the sleeve bottom plate at a third contour line; And The first contour line and the second contour line form an arcuate section of the outer circle, the third contour line forms an arcuate section of the inner circle.

4. A piston for an internal combustion engine, comprising: A piston body including a piston skirt and a piston crown attached to the piston skirt; The piston crown has a bowl surface forming a combustion bowl and a piston rim, the piston rim positioned radially outward of the combustion bowl and extending circumferentially about a piston central axis and extending radially between the combustion bowl and the outer peripheral surface of the piston crown; A plurality of valve sleeves are formed within the piston rim; The plurality of valve sleeves form a fluid flow path through the piston edge and each includes a valve sleeve bottom plate, a valve sleeve wall extending between the combustion bowl and the outer peripheral surface, and a central step; And The central step projects from the valve sleeve bottom plate and is positioned within the respective fluid flow path and includes an inner step wall and an outer step wall which are spaced apart from the valve sleeve wall and from the outer peripheral surface of the piston top.

5. The piston according to claim 4, wherein: The sleeve wall in each of the plurality of valve sleeves includes a first sleeve wall and a second sleeve wall defining an outer circle, and the respective outer step wall defines an inner circle concentric with the outer circle; The first sleeve wall intersects the sleeve bottom plate at a first contour line and the second sleeve wall intersects the sleeve bottom plate at a second contour line, and the outer step wall intersects the sleeve bottom plate at a third contour line; The first contour line and the second contour line form an arc segment of the outer circle, and the third contour line forms an arc segment of the inner circle.

6. The piston according to claim 4 or 5, wherein, A stepless valve sleeve is formed in the piston edge.

7. The piston according to claim 5, wherein, The diameter of the inner circle is 39% to 80% of the diameter of the outer circle.

8. A piston top for a piston in an internal combustion engine, comprising: A piston top body defining a piston central axis extending between a first piston axial end and a second piston axial end including a combustion surface; The combustion surface includes a bowl surface forming a combustion bowl, and a piston edge which is positioned radially outward of the combustion bowl and extends circumferentially around the piston central axis and extends radially between the combustion bowl and the outer peripheral surface of the piston top; A plurality of valve sleeves are formed in the piston edge and are circumferentially distributed around the piston central axis to receive a plurality of engine valves in the internal combustion engine; The plurality of valve sleeves form a fluid flow path through the piston edge, and each includes a valve sleeve bottom plate and a valve sleeve wall extending between the combustion bowl and the outer peripheral surface; At least one of the plurality of valve sleeves further includes a central step positioned within the respective fluid flow path; The central step projects from the valve sleeve bottom plate and includes a step top surface recessed relative to the piston edge, and the central step further includes an inner step wall adjacent to the combustion bowl and an outer step wall spaced apart from the valve sleeve wall and from the outer peripheral surface of the piston top.

9. The piston top according to claim 8, wherein: The valve sleeve wall includes a first sleeve wall and a second sleeve wall defining an outer circle; The outer step wall defines an inner circle concentric with the outer circle; and The diameter of the inner circle is 39% to 80% of the diameter of the outer circle.

10. The piston top according to claim 9, wherein: The first sleeve wall intersects the sleeve bottom plate at a first contour line and the second sleeve wall intersects the sleeve bottom plate at a second contour line, and the outer step wall intersects the sleeve bottom plate at a third contour line; And The first contour line and the second contour line form an arc segment of the outer circle, and the third contour line form an arc segment of the inner circle.

11. The piston top according to claim 10, wherein: The sleeve bottom plate is planar from the third contour line to each of the first contour line and the second contour line; and the diameter of the inner circle is 60% to 64% of the diameter of the outer circle.

12. The piston crown according to claim 10, wherein: the sleeve bottom plate includes an inner planar region defined by the third contour line, an outer planar region defined by the first contour line and the second contour line, and a downwardly inclined region extending between the inner planar region and the outer planar region; and the diameter of the inner circle is 39% to 43% of the diameter of the outer circle.

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