WO2024036547A1

WO2024036547A1 - Internal combustion engine cast iron piston

Info

Publication number: WO2024036547A1
Application number: PCT/CN2022/113184
Authority: WO
Inventors: Zhenyu LUO; Zhen Zhang
Original assignee: Cummins Inc.
Priority date: 2022-08-18
Filing date: 2022-08-18
Publication date: 2024-02-22

Abstract

A piston for an internal combustion engine includes a top portion including a bowl and a bottom portion that is integrally formed with the top portion. The piston also includes an oil gallery structured to facilitate cooling of the bowl, where the oil gallery is disposed circumferentially about the top portion below the bowl and has at three ports disposed therein.

Description

INTERNAL COMBUSTION ENGINE CAST IRON PISTON

TECHNICAL FIELD

The present disclosure relates generally to the field of pistons for internal combustion engines.

BACKGROUND

Generally, pistons are integral to reciprocating engine systems that have multiple cylinders in which fuel is combusted and power is generated. The piston, which is attached to a crankshaft via a connecting rod and a piston pin, forms an air-tight seal within the engine cylinder. Combustion and exhaust process occurs above the piston within the engine cylinder head, displacing the piston within the cylinder (e.g., up/down, in/out) and causing the crankshaft to turn, which results in conversion of vertical movement of the pistons to horizontal rotational motion. The horizontal rotational motion drives vehicular motion (i.e., through the wheels) via a gearbox.

Pistons can be made from a variety of materials, including cast iron. However, various existing cast iron pistons are ill-suited for use in on-highway diesel engines due to an inability to withstand high power density and peak cylinder pressures.

SUMMARY

One aspect of the disclosure relates to a piston for an internal combustion engine. The piston includes a top portion including a bowl and a bottom portion that is integrally formed with the top portion. The piston also includes an oil gallery structured to facilitate cooling of the bowl, where the oil gallery is disposed circumferentially about the top portion below the bowl and has at least three ports disposed therein.

In various embodiments, the bowl is defined by a wall having a substantially uniform thickness. In some embodiments, the top portion includes one or more circumferentially disposed grooves, where each of the one or more grooves is structured to receive at least one of an oil ring or a compression ring. In other embodiments, the at least three ports are three ports that each correspond to one of three fluid pathways extending downward toward the bottom portion, the three fluid pathways being structured to facilitate flow of oil into and out of the oil gallery. In yet other embodiments, a surface within the oil gallery forms a coherent surface with each of the three fluid pathways. In various embodiments, the piston also includes a piston boss disposed through the bottom portion. In some embodiments, a first of the three fluid pathways is disposed on a first side of the piston boss and a second of the three fluid pathways is disposed on a second side of the piston boss, the first side being disposed radially opposite the second side. In other embodiments, a first of the three fluid pathways is disposed at a first end of the piston boss and a second of the three fluid pathways is disposed at a second end of the piston boss, the first end being disposed longitudinally opposite the second end. In yet other embodiments, the oil gallery includes an upper portion and a plurality of ridges disposed within the upper portion, where the plurality of ridges are structured to increase turbulence of oil flowing within the oil gallery. In some embodiments, the piston is made of cast iron.

Another aspect of the disclosure relates to a method of forming a piston for an internal combustion engine. The method includes selecting a material for casting and selecting at least one datum, where the at least one datum defines at least one geometric dimension or tolerance of the piston. The method also includes forming a mold based on the at least one datum, and casting the material to form the piston. The piston includes a top portion and a bottom portion that is integrally formed with the top portion. The piston also includes an oil gallery structured to facilitate cooling of the bowl, where the oil gallery is disposed circumferentially about the top portion below the bowl and having at least three ports disposed therein, and where the at least one datum is a surface within the oil gallery.

In various embodiments, the surface is an outer surface within the oil gallery. In other embodiments, the at least one datum includes a first datum and a second datum, the first datum being an outer surface within the oil gallery and the second datum being a height corresponding to a distance between an upper portion of the oil gallery and a bottom edge of the bottom portion. In some embodiments, the at least one datum further includes a third datum, the third datum being a diametrical distance between an outermost wall of the bottom portion. In yet other embodiments, the at least one datum includes a position corresponding to each of the three ports.

In various embodiments, the mold is an expendable mold. In some embodiments, casting the material to form the piston includes controlling a rate of pouring of molten iron into the mold. In other embodiments, controlling the rate of pouring of molten iron includes controlling a pressure within the mold. In yet other embodiments, the method also includes machining at least one portion of the piston. In some embodiments, the at least three ports are three ports each corresponding to one of three fluid pathways extending downward toward the bottom portion, the three fluid pathways structured to facilitate flow of oil into and out of the oil gallery.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which:

FIG. 1 is a bottom view of a piston for an internal combustion engine, according to an example embodiment.

FIG. 2 is a side cross-sectional view of the piston of FIG. 1, taken along line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a three-dimensional rendering of an oil gallery within the piston of FIG. 1.

FIG. 4 is a side cross-sectional view of a top portion of the piston of FIG. 1, taken along line 2-2 of FIG. 1.

FIG. 5 is an alternate side cross-sectional view of the piston of FIG. 1, taken along line 5-5 of FIG. 1.

FIG. 6 is a partial section view of the piston of FIG. 1, taken along line 6-6 of FIG. 1.

FIG. 7 is a flow diagram illustrating a method of forming the piston of FIG. 1.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate certain example embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.

Referring to FIGS. 1 and 2, a piston 100 for an internal combustion engine is shown, according to an example embodiment. In various embodiments, the piston 100 is made entirely or in part of cast iron (e.g., gray cast iron) . In various embodiments, the internal combustion engine may be a diesel engine. As shown, the piston 100 includes a top portion 101 (i.e., “crown” ) and a bottom portion 102, where the bottom portion 102 is integrally formed with the top portion 101. The top portion 101 includes a bowl 105 (i.e., combustion bowl) which is recessed below an uppermost rim portion 107 of the piston 100. The bowl 105 is structured to influence movement of air and fuel during a compression stroke of the piston 100 and forms a portion of a combustion chamber within the internal combustion engine. The bowl 105 includes a substantially centrally located peak 110, which may be surrounded by a valley or concentric recess within the bowl 105. The peak 110 may be axially aligned with the piston 110 and is structured to facilitate swirling of air to improve homogenous burning and combustion.

The top portion 101 also includes an oil gallery 115 disposed within a circumferentially outermost region of the top portion 101 below the uppermost rim portion 107. The oil gallery 115 includes one or more fluidic channels to enable flow of oil through the piston, which facilitates heat exchange during operation of the piston 100 within the engine. The oil gallery 115 is separated from the bowl 105 by a wall 117, which is substantially uniform in thickness and sufficiently thin to allow and optimize heat extraction from the bowl 105 by oil flowing through the oil gallery 115, and to withstand heat and pressure during combustion and enhance thermal fatigue strength of the piston 100. In various embodiments, the thickness of the wall 117 may be approximately 4 mm. In various embodiments, a cross-section of the oil gallery 115 may be substantially circular, elliptical, or oblong in shape. In yet other embodiments, the cross-section of the oil gallery 115 may be complementary to a contour of the bowl 105 (e.g., such as shown in FIG. 2) .

The oil gallery 115 may receive or expel oil through one or more ports. As shown in FIG. 1, the piston 100 may include a first port 120, a second port 125, and a third port 130 which are disposed within a bottom surface 133 of the bottom portion 102. In various embodiments, the first port 120, the second port 125, and the third port 130 may be arranged on opposing sides of a piston boss 140-configured to receive a piston pin-disposed through the bottom portion 133. The piston boss 140 may be disposed within the bottom portion 102 such that a wall of the bottom portion 102 (e.g., skirt) surrounds or substantially surrounds the piston boss 140. For example, as shown in FIG. 1, the first port 120 may be disposed on a radially opposite side of the piston boss 140 as the second port 125, and the third port 130 may be disposed on a longitudinally oppose end of the piston boss 140 as the second port 125. In various embodiments, at least one of the first port 120, the second port 125, or the third port 130 is an oil inlet configured to facilitate oil flow into the oil gallery 115. In some embodiments, at least one of the first port 120, the second port 125, or the third port 130 is an oil outlet configured to facilitate oil flow out of the oil gallery 115. In other embodiments, at least two of the first port 120, the second port 125, or the third port 130 are oil inlets. In yet other embodiments, at least two of the first port 120, the second port 125, or the third port 130 are oil outlets.

As shown in FIG. 2, the top portion 101 of the piston 100 may include one or more grooves 135 disposed circumferentially about the top portion 101. Each of the one or more grooves 135 may be structured to receive one or more oil rings and/or compression rings. As shown, an uppermost groove 135 may be disposed a distance below the uppermost rim portion 107.

Referring now to FIGS. 3 and 4, the oil gallery 115 may be structured to increase oil turbulence within the oil gallery 115, which may facilitate efficient cooling of the bowl 105. As shown in FIG. 3, which depicts a three-dimensional rendering of just the oil gallery 115, the oil gallery 115 is structured to be circumferentially disposed within the upper portion 101 such that it surrounds the bowl 105. As shown, the oil gallery 115 is formed between an outer surface 150 and an inner surface 153, where the outer surface 150 is disposed radially outward of the inner surface 153 and is integrally formed with an outermost wall 167 of the top portion 101. The inner surface 153 is integrally formed with the wall 117 which separates the bowl 105 from the oil gallery 115. Accordingly, as shown in FIG. 3, the inner surface 153 has a contour 163 that is complementary to a shape of the bowl 105 to facilitate efficient thermal exchange (e.g., cooling) therebetween.

To facilitate turbulence, the oil gallery 115 may include a plurality of ribs or ridges 160 disposed within a surface and extending into an interior of the oil gallery 115. In various embodiments, the ridges 160 may be disposed along at least one of the inner surface 153 or the outer surface 150. In other embodiments, such as shown in FIG. 3, the ridges 160 may be disposed within an upper portion 165 of the oil gallery 115, in a region where the outer surface 150 meets the inner surface 153. Although FIG. 3 shows eight ridges 160, the oil gallery 115 may be structured to include any number of ridges 160 (e.g., 2, 4, 5, 7, 24, etc. ) . In various embodiments, the ridges 160 may be disposed equidistantly about a circumference of the oil gallery 115. In other embodiments, the ridges 160 may be disposed adjacent to or near one or more of the first port 120, the second port 125, or the third port 130.

As shown in both FIGS. 3 and 4, each of the first port 120, the second port 125, and the third port 130 respectively correspond to a first fluid pathway 155, a second fluid pathway 157, and a third fluid pathway 159, where each of the fluid pathways extend downward away from the wall 117 and the uppermost rim portion 107. As illustrated in FIG. 4, each of the first fluid pathway 155, second fluid pathway 157, and third fluid pathway 159 are joined with the outer surface 150 to form a coherent surface within the oil gallery 115. The coherent surface formed by each of the first fluid pathway 155, second fluid pathway 157, and third fluid pathway 159 facilitate uninhibited flow of oil into and out of the oil gallery 115.

Referring now to FIGS. 5-7, the piston 100 is formed out of a single continuous piece of material (e.g., cast iron) , having no joint or weld. A method 200 of forming the piston 100 is depicted in FIG. 7. To form the piston 100 via casting, material may be selected (e.g., grey cast iron) and melted in an operation 205. To form a mold or core for the casting, one or more datums may be selected to facilitate casting in an operation 210, where the one or more datums define reference frames to determine geometric dimensioning and tolerancing of the piston 100.

In various implementations, the location of the outside surface 150, as defined circumferentially about the top portion 101, may be selected as a machining rough datum. As shown in FIG. 6, the outside surface 150 may have a known diameter 183 between opposite sides of the top portion 101 (measured from the outside surface 150) . In various implementations, the diameter 183 may have a tolerance ± 0.5 mm. In other implementations, the diameter 183 may have a unilateral tolerance of + 0 and -1.5 mm. Selecting the surface 150 as the rough datum allows for precise control of the thickness of the wall 117, which forms the bowl 105 below the rim 107. In various implementations, the thickness of the wall 117 may have a tolerance ± 1 mm. In various implementations, formation of the piston 100 may include determination of at least three datums. In addition to selecting the surface 150 as a rough datum, the upper portion 165 (i.e., upper surface) of the oil gallery 115 may be used as a second datum. A height 180 may be defined between a bottom edge of the bottom portion 102 and the upper portion 165. In various implementations, the height 180 may have a tolerance ± 1.5 mm. Finally, a wall 188 of the bottom portion 102 may be used as a third datum. A diameter 186 may be defined between opposing sides of the bottom portion 102 (measured from the wall 188) . In various implementations, the diameter 186 may have a tolerance of ± 1 mm. In various implementations, the upper rim 107 may additionally or alternatively be used as a datum. Once each datum is selected, the piston 100 may be formed by casting.

Once the one or more datums have been defined in the operation 210, the casting mold may then be formed in an operation 215 (i.e., using the one or more datums) . In various implementations, sand casting (or other expendable mold casting) may be used to form the piston 100. Accordingly, in addition to defining the datum based on the surface 150 of the oil gallery 115, the upper portion 165 of the oil gallery 115, and the wall 188, each of the first port 120, second port 125, and third port 130 (and the corresponding first fluid pathway 155, second fluid pathway 157, and third fluid pathway 159) may be used to position the sand core during formation of the piston 100 (i.e., be used as datum) . In various embodiments, a rate of pouring of molten iron into the mold may be controlled to enhance precision of the cast (e.g., via controlling pressure within the mold, inducing a vacuum, etc. ) . In various embodiments, one or more surfaces or portions of the piston 100 may be machined to ensure precision of dimensions (e.g., wall 117 thickness, diameter 186, etc. ) in an operation 225. For example, the wall 117 of the piston 100 may be machined to ensure it has a substantially uniform thickness.

In various embodiments, formation of the piston 100 may be carried out (e.g., by a fabrication or manufacturing system) in response to one or more instructions received from at least one controller, where the controller may include a processor and non-transitory computer readable medium (e.g., memory device) having computer-readable instructions stored thereon that, when executed by the processor, cause the at least one controller to carry out the operations called for by the instructions. In various embodiments, the controller may be a computing device or configured as part of a data cloud computing system configured to receive commands from control device and/or remote computing device.

By selecting the datums as outlined above, the piston 100 may be formed to have a uniform thickness of the wall 117, which forms the bowl 105 below the rim 107. The uniform thickness of the wall 117, combined with formed coherent surfaces between the fluid pathways in the oil gallery 115 (i.e., the first fluid pathway 155, second fluid pathway 157, and third fluid pathway 159) and the surface 150, facilitate flow of oil through into and out of the oil gallery 115, which enables efficient cooling of the bowl 105. In addition, the ribs 160, which may be optionally formed in the upper portion 165 (or elsewhere within the oil gallery 115) , increase oil turbulence within the oil gallery to further facilitate cooling of the bowl 105. The efficient cooling allows the piston 100 to be made from a greater variety of materials beyond steel, which may include but are not limited to iron. Use of cast iron may reduce overall cost of production of the piston 100-particularly as the piston 100 may be formed via casting, having no weld or other joint.

Notwithstanding the embodiments described above in reference to FIGS. 1–7, various modifications and inclusions to those embodiments are contemplated and considered within the scope of the present disclosure.

As utilized herein with respect to numerical ranges, the terms “approximately, ” “about, ” “substantially, ” and similar terms generally mean +/-10%of the disclosed values, unless specified otherwise. As utilized herein with respect to structural features (e.g., to describe shape, size, orientation, direction, relative position, etc. ) , the terms “approximately, ” “about, ” “substantially, ” and similar terms are meant to cover minor variations in structure that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

It should be noted that the terms “exemplary, ” “example” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples) .

The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable) . Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled) , the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member) , resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic.

References herein to the positions of elements (e.g., “top, ” “bottom, ” “above, ” “below” ) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other example embodiments, and that such variations are intended to be encompassed by the present disclosure.

Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partial concurrence, unless specified differently above.

It is important to note that any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein. Although only one example of an element from one embodiment that can be incorporated or utilized in another embodiment has been described above, it should be appreciated that other elements of the various embodiments may be incorporated or utilized with any of the other embodiments disclosed herein

Claims

A piston for an internal combustion engine comprising:

a top portion comprising a bowl;

a bottom portion integrally formed with the top portion; and

an oil gallery structured to facilitate cooling of the bowl, the oil gallery being disposed circumferentially about the top portion below the bowl and having at least three ports disposed therein.
The piston of claim 1, wherein the bowl is defined by a wall having a substantially uniform thickness.
The piston of claim 2, wherein the top portion comprises one or more circumferentially disposed grooves, each of the one or more circumferentially disposed grooves is structured to receive at least one of an oil ring or a compression ring.
The piston of claim 1, wherein the at least three ports are three ports each corresponding to one of three fluid pathways extending downward toward the bottom portion, the three fluid pathways structured to facilitate flow of oil into and out of the oil gallery.
The piston of claim 4, wherein a surface within the oil gallery forms a coherent surface with each of the three fluid pathways.
The piston of claim 5, further comprising a piston boss disposed through the bottom portion.
The piston of claim 6, wherein a first of the three fluid pathways is disposed on a first side of the piston boss and a second of the three fluid pathways is disposed on a second side of the piston boss, the first side being disposed radially opposite the second side.
The piston of claim 6, wherein a first of the three fluid pathways is disposed at a first end of the piston boss and a second of the three fluid pathways is disposed at a second end of the piston boss, the first end being disposed longitudinally opposite the second end.
The piston of claim 1, wherein the oil gallery comprises an upper portion and a plurality of ridges disposed within the upper portion, the plurality of ridges structured to increase turbulence of oil flowing within the oil gallery.
The piston of claim 1, wherein the piston is made of cast iron.
A method of forming a piston for an internal combustion engine, the method comprising:

selecting a material for casting;

selecting at least one datum, the at least one datum defining at least one geometric dimension or tolerance of the piston;

forming a mold based on the at least one datum; and

casting the material to form the piston, wherein the piston comprises:

a top portion comprising a bowl;

a bottom portion integrally formed with the top portion; and

an oil gallery structured to facilitate cooling of the bowl, the oil gallery being disposed circumferentially about the top portion below the bowl and having at least three ports disposed therein;

wherein the at least one datum comprises a surface within the oil gallery.
The method of claim 11, wherein the surface is an outer surface within the oil gallery.
The method of claim 11, wherein selecting the at least one datum comprises selecting a first datum and a second datum, the first datum being an outer surface within the oil gallery and the second datum being a height corresponding to a distance between an upper portion of the oil gallery and a bottom edge of the bottom portion.
The method of claim 13, wherein selecting the at least one datum further comprises selecting a third datum, the third datum being a diametrical distance between an outermost wall of the bottom portion.
The method of claim 11, wherein the at least one datum further comprises a position corresponding to each of the three ports.
The method of claim 11, wherein the mold is an expendable mold.
The method of claim 11, wherein casting the material to form the piston comprises controlling a rate of pouring of molten iron into the mold.
The method of claim 17, wherein controlling the rate of pouring of molten iron comprises controlling a pressure within the mold.
The method of claim 11, further comprising machining at least one portion of the piston.
The method of claim 11, wherein the at least three ports are three ports each corresponding to one of three fluid pathways extending downward toward the bottom portion, the three fluid pathways structured to facilitate flow of oil into and out of the oil gallery.