U.S. patent application number 17/213008 was filed with the patent office on 2021-08-05 for parent bore cylinder block of an opposed-piston engine.
This patent application is currently assigned to ACHATES POWER, INC.. The applicant listed for this patent is ACHATES POWER, INC.. Invention is credited to John J. Koszewnik, Andrew P. Perr, Gary A. Vrsek.
Application Number | 20210239070 17/213008 |
Document ID | / |
Family ID | 1000005525100 |
Filed Date | 2021-08-05 |
United States Patent
Application |
20210239070 |
Kind Code |
A1 |
Perr; Andrew P. ; et
al. |
August 5, 2021 |
PARENT BORE CYLINDER BLOCK OF AN OPPOSED-PISTON ENGINE
Abstract
A parent bore cylinder block of an internal combustion,
opposed-piston engine includes cooling passages that are formed
using a 3-D printed casting core. The casting core can include
portions that are ceramic. The parent bore cylinder block can
include multiple cylinders, each cylinder with cooling passages and
turbulence inducing features in those cooling passages,
particularly surrounding the central portions of the cylinders.
Inventors: |
Perr; Andrew P.; (Columbus,
IN) ; Koszewnik; John J.; (Colorado Springs, CO)
; Vrsek; Gary A.; (Howell, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ACHATES POWER, INC. |
San Diego |
CA |
US |
|
|
Assignee: |
ACHATES POWER, INC.
San Diego
CA
|
Family ID: |
1000005525100 |
Appl. No.: |
17/213008 |
Filed: |
March 25, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16189129 |
Nov 13, 2018 |
10989136 |
|
|
17213008 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 10/00 20141201;
F02F 1/14 20130101; B33Y 70/00 20141201; B22D 29/002 20130101; F01P
2003/021 20130101; B28B 1/001 20130101; B33Y 80/00 20141201; F02F
1/10 20130101; B22C 9/10 20130101; F02F 2200/06 20130101; F01P 3/02
20130101; F02B 75/28 20130101 |
International
Class: |
F02F 1/10 20060101
F02F001/10; B22C 9/10 20060101 B22C009/10; B22D 29/00 20060101
B22D029/00; B28B 1/00 20060101 B28B001/00; B33Y 10/00 20060101
B33Y010/00; F01P 3/02 20060101 F01P003/02; F02B 75/28 20060101
F02B075/28; F02F 1/14 20060101 F02F001/14; B33Y 80/00 20060101
B33Y080/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] This Project Agreement Holder (PAH) invention was made with
U.S. Government support under Agreement No. W15KQN-14-9-1002
awarded by the U.S. Army Contracting Command-New Jersey (ACC-NJ) to
the National Advanced Mobility Consortium. The Government has
certain rights in the invention.
Claims
1. A method of making a cylinder block of an opposed-piston engine,
the method comprising: making a printed casting core for a cylinder
block with at least one cylinder having a bore, the cylinder being
configured to receive a pair of pistons disposed in opposition in
the bore; creating a molding assembly for the cylinder block using
the printed casting core; casting metal into the cylinder block
using the molding assembly; and removing the molding assembly.
2. The method of claim 1, wherein the cylinder comprises intake and
exhaust ports separated along a longitudinal axis of the cylinder,
each port comprising an array of circumferentially-spaced adjacent
port openings in the cylinder block from the cylinder bore to an
intake plenum of the engine and to an exhaust plenum of the engine,
respectively, and a port bridge between each pair of adjacent port
openings.
3. The method of claim 1, wherein making a casting core comprises
using a 3-D printing technique.
4. The method of claim 1, wherein the molding assembly comprises a
ceramic core portion and one or more sand core components.
5. The method of claim 4, further wherein removing the molding
assembly comprises using caustic or an acid to dissolve the ceramic
core portion.
6. The method of claim 4, wherein the ceramic core portion of the
casting core comprises features near an intermediate portion of the
cylinder which form cooling channels in the metal cylinder
block.
7. The method of claim 1, wherein the casting core forms an
interior surface of the cylinder block defining an annular cooling
jacket with cooling features.
8. The method of claim 7, wherein the cooling features comprise
turbulence-inducing features.
9. The method of claim 8, wherein the turbulence-inducing features
comprise pegs to create turbulent coolant flow of liquid coolant
along and around an intermediate portion of the at least one
cylinder.
10. The method of claim 7, wherein the cooling features comprise
ridges or lands formed to define coolant flow paths
11. The method of claim 1, wherein the casting core forms an intake
air plenum.
12. The method of claim 1, wherein the casting core forms exhaust
ports and intake ports of the at least one cylinder.
13. The method of claim 1, wherein the cylinder block is a parent
bore cylinder block of the opposed-piston engine.
14. The method of claim 1, wherein casting metal into the cylinder
block using the molding assembly comprises casting a parent bore
cylinder block comprising a crank case portion for an intake side
of the opposed-piston engine and a crank case portion for an
exhaust side of the opposed-piston engine.
15. The method of claim 1, wherein casting metal into the cylinder
block using the molding assembly comprises casting a parent bore
cylinder block of an opposed-piston engine comprising one
cylinder.
16. The method of claim 1, wherein casting metal into the cylinder
block using the molding assembly comprises casting a parent bore
cylinder block of an opposed-piston engine comprising three
cylinders.
17. The method of claim 1, wherein casting metal into the cylinder
block using the molding assembly comprises casting a parent bore
cylinder block comprising four cylinders.
Description
PRIORITY
[0001] This application is a divisional of U.S. application Ser.
No. 16/189,129, filed Nov. 13, 2018, and published as US Pub.
2020/0149493, published May 14, 2020.
TECHNICAL FIELD
[0003] The technical field includes opposed-piston internal
combustion engines. More specifically the technical field relates
to the construction of a parent bore cylinder block of an
opposed-piston engine in which one or more cylinders are cast as an
integral unit with a cylinder block. More particularly, the field
concerns casting a parent bore cylinder block of an opposed-piston
engine using a casting core fabricated by 3-D printing. The field
may include use of a core combination including one or more ceramic
casting cores with which to form features of the cylinders.
BACKGROUND
[0004] In a two-stroke cycle, opposed-piston internal combustion
engine, there is at least one ported cylinder with a pair of
pistons disposed for counter-moving operation in the cylinder bore.
To-and-fro sliding motion of the pistons in the cylinder is guided
by the bore.
[0005] The pistons reciprocate in mutually opposing directions in
the bore, between respective top center (TC) and bottom center (BC)
locations. In one stroke, the pistons approach each other to form a
combustion chamber between their end surfaces in an intermediate
portion of the bore. In a following stroke, the pistons move apart
in response to combustion. The combustion chamber in the
intermediate portion is defined between the end surfaces of the
pistons when the pistons move through their TC locations of the
cylinder, with the piston end surfaces and bore surface providing
the combustion chamber boundaries. This intermediate portion bears
the highest levels of combustion temperature and pressure that
occur during engine operation, and the presence of openings for
devices such as fuel injectors, valves, and/or sensors in the
intermediate portion diminish its strength and make it vulnerable
to cracking, particularly through the fuel and valve openings.
[0006] In uniflow-scavenged, opposed-piston engines, cylinder
construction can include an intake port in the vicinity of a first
end of the cylinder and an exhaust port in the vicinity of a second
end of the cylinder. Each port may comprise an array of openings,
typically arranged along a circumference of the cylinder, with a
bridge (also called a "bar") separating adjacent port openings.
Because exhaust gases leaving a cylinder are much hotter than
incoming air, the temperatures experienced by the exhaust port of a
cylinder in an opposed-piston engine are typically greater than
those experienced by an intake port of the same cylinder. Thus,
areas adjacent to the exhaust port and the bridges in the exhaust
port warrant additional cooling measures as compared with areas
adjacent the intake port.
[0007] Current opposed-piston constructions for cylinders with
cooling systems include wet liners with one or more sleeves that
guide cooling fluid ("coolant") along an outside surface of the
cylinder, as well as machined channels along or through exhaust
port bridges through which the coolant flows. Representative
cylinder constructions embodying a liner/sleeve assembly are taught
in U.S. Pat. No. 8,485,147.
[0008] Presently, a cylinder block of an opposed-piston engine is
manufactured by casting and machining block portions that are
assembled into an integrated support structure with cylinder
tunnels in which cylinder liners are held. Typically, such a
cylinder block comprises multiple portions which are separated to
allow cylinder liners, with sleeves attached, to be inserted into
the tunnels. Fluid seals, such as O-rings, are fitted to the liners
to confine coolant flow. With the liner/sleeve assemblies and fluid
seals in place, the cylinder block portions are joined, typically
by means of threaded fasteners. Such a cylinder block construction
is taught in U.S. Pat. No. 9,435,290. Manifestly, it is desirable
to provide a monolithic cylinder block of an opposed-piston engine
formed as a single piece so as to reduce component count, minimize
manufacturing steps, and reduce manufacturing costs. These and
other desirable objectives are realized by construction of a parent
bore cylinder block of an opposed-piston engine that includes
cylinders cast in the block with features defining coolant paths
that ensure effective thermal management of the cylinders when the
engine operates. Parent bore cylinder block constructions do not
comprise cylinder liners or cylinder sleeves.
SUMMARY
[0009] A parent bore cylinder block of an opposed-piston engine may
be made using a 3-D printed casting core for part or all of the
cylinder block components, thus minimizing the number of parts and
the portions that must be joined while allowing for complex shapes
and potentially reducing manufacturing costs. Methods for producing
a parent bore cylinder block, as well as for producing the 3-D
printed casting core, are also presented. Preferably, the parent
bore cylinder block is cast from a single type of metal or metal
alloy.
[0010] In some implementations, a parent bore cylinder block of an
opposed-piston engine includes at least one cylinder with a bore
that has a bore surface and a longitudinal axis, an intermediate
portion situated between exhaust and intake ports of the cylinder
and extending along the longitudinal axis, and a cooling jacket
surrounding a combustion zone in the intermediate portion of the
cylinder. When used herein, the term "combustion zone" refers to an
annular portion of the cylinder where a mixture of fuel and air
combusts. A combustion chamber is defined or formed between the end
surfaces of the pistons as the pistons move through their TC
locations within the combustion zone. Provision is made in the
construction of the combustion zone to enable it to withstand the
pressure of combustion and to effectively remove heat of combustion
that escapes from the combustion chamber.
[0011] The following features can be present in a cylinder of the
parent bore cylinder block in any suitable combination. The
cylinder may include longitudinally separated intake and exhaust
ports. The intake and exhaust ports may include port openings
positioned respectively in an intake plenum and an exhaust plenum
of the parent bore cylinder block. In each port, a port bridge
separates each port opening from an adjacent port opening. A
cooling passage may be provided through at least one port bridge of
the exhaust port. The parent bore cylinder block can be made of a
single metal casting in which the port openings are cast features.
Other cooling features of the cylinder may include any of pegs,
walls, ridges, ribs, and other protrusions from an outer wall of
the cylinder. These cooling features can be configured to create a
coolant flow path for cooling fluid. Spacing between the cooling
features can range from 1.5 mm to 10 mm, such as about 5 mm. The
parent bore cylinder block can further include one or more machined
features. In some implementations, the parent bore cylinder block
may include an intake gas plenum chamber into which all the intake
port openings of a cylinder open from the interior of the cylinder
and an exhaust gas plenum chamber into which all the exhaust port
openings of a cylinder open from the interior of the cylinder. In
some implementations, a parent bore cylinder block for an
opposed-piston internal combustion engine may include multiple
cylinders.
[0012] In related aspects, an opposed-piston engine includes a
parent bore cylinder block which is cast from a single type of
metal or metal alloy. The parent bore cylinder block includes at
least one cylinder with a cylinder bore, a bore surface, and a
longitudinal axis. A combustion zone of the cylinder block is
located an intermediate portion of the at least one cylinder, along
the longitudinal axis of the cylinder bore. The parent bore
cylinder block includes a cooling jacket surrounding the combustion
zone. Cooling features of the cylinder are enclosed by the cooling
jacket. An intake port of the cylinder is longitudinally separated
from an exhaust port of the cylinder. The intake port includes
openings in the parent bore cylinder block to an intake plenum of
the parent bore cylinder block and the exhaust port includes
openings in the parent bore cylinder block to an exhaust plenum of
the parent bore cylinder block.
[0013] In another related aspect, a method of making a parent bore
cylinder block of an opposed-piston engine is described herein. The
method includes making a casting core for a parent bore cylinder
block, creating a molding assembly for the parent bore cylinder
block using the casting core, casting metal into the molding
assembly, and, once the metal parent bore cylinder block is ready,
removing the molding assembly. The method can apply to a parent
bore cylinder block for an opposed-piston, two-stroke,
uniflow-scavenged internal combustion engine.
[0014] Making a casting core for the method may include using a 3-D
printing technique. In the method, the casting core can include a
ceramic core portion and one or more sand core components. Removing
the molding assembly in the method can include using caustic or an
acid to dissolve the ceramic core portion. In some implementations
of the method, the ceramic core portion of the casting core can
include features near an intermediate portion of the cylinder that
form cooling channels in the metal cylinder block.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows a portion of an opposed-piston engine,
partially cut away to show a cylinder, and is properly labeled
"PRIOR ART".
[0016] FIG. 2 is a side elevational view of a cylinder liner
assembly of the opposed-piston engine of FIG. 1, with a portion of
a sleeve cut away from a liner, and is properly labeled "PRIOR
ART".
[0017] FIG. 3A is an exploded view of the cylinder liner assembly
of FIG. 2 showing sleeve and liner separated, and is properly
labeled "PRIOR ART".
[0018] FIG. 3B is a cross-sectional view of the cylinder liner
assembly of FIG. 2, and is properly labeled "PRIOR ART".
[0019] FIG. 4A shows an exemplary cylinder construction for an
opposed-piston engine that is made using a 3-D printed casting
core.
[0020] FIG. 4B is a view of part of the cylinder of FIG. 4A showing
certain cooling features, and FIG. 4C is a view of a casting core
portion that shapes some of the cooling features.
[0021] FIGS. 5A and 5B show views of a parent bore cylinder block
with multiple opposed-piston engine cylinders with cooling
features.
[0022] FIGS. 5C and 5D show a casting core for the parent bore
cylinder block of FIGS. 5A and 5B.
[0023] FIG. 5E is an exploded view of the casting core shown in
FIGS. 5C and 5D.
[0024] FIG. 5F shows the casting core for certain cooling features
of the parent bore cylinder block shown in FIGS. 5A and 5B.
[0025] FIG. 6 shows a method for making a parent bore cylinder
block or a parent bore engine block of an opposed-piston
engine.
DETAILED DESCRIPTION
[0026] The parent bore cylinder blocks described and illustrated
herein provide improved opposed-piston engines. Other aspects
include engine embodiments for opposed-piston engines which are
possible through use of the novel means and methods of fabrication
described below.
[0027] FIG. 1 shows a prior-art opposed-piston engine 10 with a
cylinder block 12 with three identically-constructed cylinders 14,
15, and 16. A portion of the cylinder block 12 is removed to show
the construction of the cylinder 16 which includes a cylinder
tunnel 18 formed in the block in which a cylinder liner 20 is
supported. The engine 10 includes two crankshafts 22 and 23. The
cylinder liner 20 includes an intake port 25 near a first liner end
27, exhaust port 29 near a second liner end 31, and an intermediate
portion 34 situated between the intake and exhaust ports. The
intake port 25 and exhaust port 29 open into an intake plenum and
exhaust plenum, respectively. The exhaust plenum may be an exhaust
chamber that receives all the exhaust gas from the exhaust ports of
all of the cylinders in the cylinder block.
[0028] FIGS. 2, 3A, and 3B illustrate a prior art cylinder
structure for opposed-piston engines that includes a liner with a
bore and longitudinally displaced intake and exhaust ports near
respective ends thereof. As per FIGS. 1 and 3A, a compression
sleeve 40 is received over the liner 20. A fuel injector 45 is
supported in a boss 46 through the sidewall of the cylinder for
direct injection of fuel into the combustion chamber.
[0029] FIGS. 2, 3A, and 3B, show details of the structure of the
prior art cylinder 16 which includes the liner 20 with the
compression sleeve 40 closely encircling and reinforcing the
portion of the liner 20 that extends from the intake port 25 to the
intermediate portion 34. As seen in FIG. 2 and FIG. 3B, the
intermediate portion 34 contains a top ring reversal zone 41 where
a combustion chamber is formed when the end surfaces of the pair of
pistons disposed in opposition in the bore are in close mutual
proximity. The compression sleeve 40 is formed to define a
generally annular jacket between itself and the external surface 42
of the liner through which a liquid coolant may flow in an axial
direction from near the intake port toward the exhaust port. The
strength of the intermediate portion 34 is reinforced by an annular
grid 50 of pegs 52 that extend between the intermediate portion 34
and the compression sleeve 40. The grid 50 closely encircles the
intermediate portion 34, which is subjected to the high pressures
and temperatures of combustion. The pegs 52 support the liner
intermediate portion 34 against the compression sleeve 40. The grid
50 also defines an annular turbulent liquid coolant flow path
extending across the intermediate portion 34.
[0030] A generally annular space 55 is formed between the external
surface 42 of the liner and the compression sleeve 40. This space
surrounds the side of the liner intermediate portion 34 that is
nearest the intake port 25. Another generally annular space 59 is
formed between the external surface 42 of the liner and the
compression sleeve 40. This space abuts the side of the liner
intermediate portion 34 that is nearest the exhaust port 29. These
spaces 55 and 59 are in fluid communication with each other via a
coolant flow path defined by the grid 50. One or more coolant entry
ports 61 formed in the compression sleeve 40 are positioned over
and in fluid communication with the annular space 55 and one or
more coolant exit ports 63 formed in the compression sleeve are
positioned over and in fluid communication with the annular space
59.
[0031] As per FIGS. 2 and 3A, the grid pegs 52 may be provided in
enough density to closely surround and reinforce those sectors of
the intermediate portion where bosses 46 locate and support
injector nozzles, valves, and the like. Advantageously, the maze of
interstices among the grid pegs 52 affords access of liquid coolant
to the entirety of the outside surface of each boss 46 and to the
external surface area of the liner immediately adjacent to the
boss.
[0032] During operation of the opposed-piston engine 10, the
cylinder 16 is cooled by introducing a liquid coolant (such as a
water-based mixture) into the jacket defined between the
compression sleeve 40 and the external surface 42 of the liner. The
coolant is pumped through a coolant channel in the cylinder block
12 that is in fluid communication with the annular space 55. The
pumped coolant enters the annular space 55 via the coolant entry
ports 61, which causes the coolant to flow on the external surface
42, along the intermediate portion 34 of the liner 20. The pump
pressure causes the liquid coolant to flow through the grid 50
wherein the pegs 52 act as an annular maze of turbulators (devices
that turn laminar flow into turbulent flow) that encircles the
intermediate portion 34 and generates turbulent flow of the coolant
across the intermediate portion. The turbulent flow increases the
heat transfer efficiency into the liquid coolant flowing over the
intermediate portion 34. The pressure of coolant flowing through
the grid 50 causes the liquid coolant to flow from the intermediate
portion 34 toward the exhaust port 29 and into the annular space
59. From the annular space 59, the coolant flows to and through a
return channel formed in the cylinder block 12. In some instances,
coolant may be routed from the annular space 59 through channels 69
(e.g., cooling passage) that pass on, over, or through the exhaust
port bridges 70.
[0033] Prior art cylinder liners, such as those shown in FIGS. 2,
3A, and 3B, can be made using conventional casting and/or machining
techniques. A conventional casting process may include creating a
core of sand and a binder, such as an organic material (e.g.,
vegetable oil, cereal), a thermoset polymer, a low-melting
temperature metal or alloy, clay, or an inorganic binder that sets
upon contact with a specific gas or with air. An example of a
binder that sets upon contact with a specific gas is sodium
silicate, which hardens after exposure to carbon dioxide.
Conventional materials can be used to form the outer portion of a
mold for casting cylinder liners and cylinder block portions.
Portions of a cylinder liner or block can be cast as individual
parts that are later joined using known techniques or means to
ultimately assemble a cylinder liner and/or an engine block.
[0034] Casting A Parent Bore Cylinder Block:
[0035] A parent bore cylinder block of an opposed-piston engine may
be cast as a single metal piece from a mold that includes a 3-D
printed casting core. A single-piece, monolithic, or unitary,
parent bore cylinder block can be advantageous over cylinder blocks
that are fabricated from many pieces fitted together because of
fewer junctions and connective parts needed (e.g., o-rings). In
contrast to conventional casting techniques which may not be able
to create the desired turbulators (e.g., turbulent flow creating
features), creating a 3-D printed casting core, particularly a
casting core that uses ceramic in some portions, can allow for the
needed feature size and texture.
[0036] Casting cores that are created using 3-D printing techniques
are particularly suited to the creation of parent bore cylinder
blocks as described herein. The complexity of the arrays of
turbulators, as well as the structures surrounding the intermediate
section and exhaust port of each cylinder (e.g., compression
sleeve, cooling water supply and exit conduits, port bridge cooling
passages) are more suitably formed using 3-D printing techniques.
Casting cores made using 3-D printing techniques are built up one
layer at a time from a computer-aided design file (CAD file) that
is divided into slices. Each slice is composed of a layer of solid
material (e.g., sand or ceramic) and an overlaid layer of binder.
The assembled slices create the completed form. In the case of
casting cores that are ceramic or that have ceramic portions,
excess powder is removed from the ceramic body while it is not yet
set, before firing in a kiln or furnace. The malleable ceramic body
can be fired before being used as part of the greater casting mold
that consists of at least one shell and core components. If the
ceramic body in the unfired state is strong enough, it can be used
as a core or core component after forming. The casting mold shapes
molten metal as it cools after being poured. In some
implementations, the mold can be spun while the metal cools to
influence the materials properties of the finished metal product.
3-D printing techniques can be used to create casting cores that
are sand cores or hybrid cores. Hybrid cores utilize sand for
larger dimensioned volumes and ceramic for portions of the core
with finer features.
[0037] A hybrid core comprising sand and ceramic portions, as
opposed to an entirely sand core, may be better suited to the
formation of a core for a cylinder with an intermediate section, as
described above, with an interior surface of the parent bore
cylinder block in place of a compression sleeve defining an annular
cooling jacket with an array of turbulence-inducing features
through which liquid coolant (e.g., water) flows when the cylinder
is used in an opposed-piston engine. A hybrid core is beneficial
when creating a parent bore cylinder block because a portion of the
hybrid casting core can be made of ceramic (i.e., ceramic core
portion) and finer features can be created. The nature of a ceramic
core makes it more durable than a sand core, so structures with
smaller features, or those spaced more closely together, can be
formed with better dimensional stability, ensuring that a part will
have dimensions closer to those that are intended. With entirely
sand cores, there is a greater risk that fine features will break
once molten metal is introduced into the mold, or that the core
will erode during that process. Additionally, with entirely sand
cores, the cast metal parts can have a surface texturing that
reflects the sand particles or that includes some embedded sand
particles left after the core is removed from the cast part. In
areas where there is little clearance between adjacent features or
where surface texturing can negatively affect fluid flow, such
texturing or surface inclusions can be undesirable. Because ceramic
casting cores (or portions of a casting core that are ceramic) are
eventually removed by leeching with a caustic or acid, the surface
of the cast part is more likely to have a smooth surface that does
not need aggressive post-molding processing.
[0038] Cylinder:
[0039] FIG. 4A shows an exemplary cylinder construction for a
parent bore cylinder block of an opposed-piston engine that is made
using a 3-D printed casting core with a ceramic portion to create
cooling features around the middle section of the cylinder. FIG. 4B
shows a portion of a cylinder with certain cooling features visible
in greater detail. FIG. 4C shows a 3-D printed casting core which
may be used to fabricate certain features of the cylinder shown in
FIG. 4A. The cylinder 120 includes an inlet port that is made up of
one or more arrays of inlet port openings 125 through the sidewall
of the cylinder arranged along a circumference of the cylinder near
a first cylinder end 127 (e.g., intake end). An exhaust port
includes one or more arrays of exhaust port openings 129 that are
separated by bridges 130 and that extend through the sidewall of
the cylinder. As per FIGS. 4A and 4B, the exhaust port openings 129
are arranged along a circumference of the cylinder near a second
cylinder end 131 (e.g., exhaust end). An intermediate portion 134
in a midsection of the cylinder 120 lies between the intake 125 and
exhaust port ports. During operation of an engine, when the pistons
are closest to each other, a combustion chamber into which fuel is
injected through fuel injection ports 146 is defined in the
intermediate portion 134, between the adjacent end surfaces of the
pistons.
[0040] The intermediate portion 134 of the cylinder contains the
combustion zone of the cylinder. A cooling jacket wall 140
(corresponding to the compression ring 40 in FIGS. 3A and 3B) is
shown encircling the intermediate portion 134 of the cylinder. The
cooling jacket wall 140 is integral to the parent bore cylinder
block. In the jacket space defined between the cooling jacket wall
140 and the intermediate portion of the cylinder wall are features
that create turbulence in flowing liquid coolant, shown here as
cylindrical pegs. Also visible in FIG. 4A are portions of the
exhaust port bridge cooling channels 169. These cooling channels
169 can also be fabricated by 3-D printed casting cores for the
channels that are used when creating the molding assembly for the
parent bore cylinder block.
[0041] The port bridges 130 separate the openings that make up the
exhaust port, and cooling channels 169 can be present in each port
bridge, between each pair of adjacent port openings, or present
less frequently, for example in every second port bridge. Further,
though the cooling channels 169 are described as being in port
bridges, cooling channels can be formed as passages through, over,
or on bridges, as well as fluid transporting cuts adjacent to
bridges formed in the cylinder cooling jacket wall, and the like.
3-D printed casting cores can accommodate any of these
configurations, including combinations of passages through and
adjacent to bridges.
[0042] The use of a 3-D printed casting core to form the
intermediate portion 134 of the cylinder 120 enables the formation
of fine-pitched features for guiding coolant around the cylinder
hot-spots in the combustion zone.
[0043] In cylinders where the intermediate portion 134 includes
features with dimensions or separations on the order of 1 to 10 mm,
the casting core can be one with ceramic material, instead of sand,
in all or part of the intermediate portion 134. Used herein,
features are structures, distinctive attributes or aspects of the
described cylinders and casting cores. The features on the
intermediate portion 134 of a cylinder can include cooling
features, such as turbulators and passages (e.g., conduits) for
transporting cooling fluid.
[0044] In FIG. 4B, an annular array of pegs 152 through which
coolant flows during engine operation can be seen, as well as
openings 169 to the cooling channels that pass through the port
bridges on the exhaust side of the cylinder 120. During engine
operation, coolant flows around the pegs 152, as well as through
the cooling channels. In FIG. 4C the casting core portion 151 that
shapes the pegs 152 can be seen independent of the cylinder 120.
The casting core portion 151 is shown having two openings 147 that
accommodate fuel injection nozzles (e.g., fuel injection boss 146
in FIG. 4B), an opening 149 to accommodate a valve for a
compression-release braking system or a sensor for a combustion
control mechanization, and openings 153 that shape molten metal
into cylindrical pegs to create turbulent coolant flow of liquid
coolant along and around the intermediate portion 134 of the
cylinder 120 (e.g., pegs 152 in FIG. 4B), as well as features 171
that allow for the connection of this core segment 151 to other
portions of a casting core or casting mold for a parent bore
cylinder block. This casting core portion or segment 151 can be 3-D
printed and may be made using a ceramic material instead of the
relatively coarser sand used in conventional casting core
fabrication.
[0045] Parent Bore Cylinder Block:
[0046] FIGS. 5A and 5B show views of a parent bore cylinder block
500 with multiple opposed-piston engine cylinders 514, 515, 516,
517 with cooling features according to FIGS. 4A and 4B. FIG. 5A
shows a first side of the parent bore cylinder block 500 and FIG.
5B is the reverse side elevational view. The parent bore cylinder
block 500 includes crank case portions 510, one 510i that supports
the intake side crank shaft and one 510e that supports the exhaust
side crank shaft, as well as portions of the gear train housing
520. Between the crank case portions 510i, 510e, are shown four
cylinders 514, 515, 516, 517, each cylinder having an intermediate
portion 570 (i.e. combustion zone) which includes the top center
position of each of the opposing pistons within the cylinders. Also
visible in the parent bore cylinder block 500 shown in FIGS. 5A and
5B are portions of an exhaust plenum 530, portions of an intake
plenum 540, openings into the cooling channels 550 on the intake
side of the cylinder block 500, and openings into the cooling
channels 560 on the exhaust side of the cylinder block 500. In
operation, to cool hot spots on the parent bore cylinder block 500,
cooling fluid flows through the intake side openings into the
cooling channels 550, to an array of turbulators in the
intermediate portions 570 of the cylinders 514, 515, 516, 517, over
or through port bridges, and then out through the exhaust side
openings 560.
[0047] The 3-D printed casting core assembly 575 shown in FIGS.
5C-5E allows for the formation of four cylinders 514, 515, 516,
517, each cylinder with a bore, cooling features outside the bore
around hot-spots (e.g., the combustion zone, adjacent to exhaust
port), and a cooling jacket surrounding the cooling features,
allowing for the flow of coolant around the cylinder hot-spots,
optimally in a turbulent manner that efficiently removes heat. Each
cylinder also has intake and exhaust ports formed by the 3-D
printed casting core. The use of a 3-D printed core for forming the
cylinders in a parent bore cylinder block allows for precise
alignment of ports and cooling features, feature size control, and
a surface roughness that allows for use of the resulting casting
as-is, without further machining, in some implementations. That is
to say, port openings, cooling features, and cooling fluid passages
can be cast features (i.e. structures that are cast into finished
or near-finished form) in a parent bore cylinder block made using a
3-D printed core, particularly one with one or more ceramic
portions such as seen in FIG. 4C in areas where the dimensions for
features or passages are relatively fine (e.g., 1 to 10 mm). A
single type of metal or metal alloy can be cast into a
multi-cylinder block using a 3-D printed casting core.
[0048] The ability to create a multi-cylinder parent bore block
using a single 3-D printed core has many potential advantages, some
further discussed here. A multi-cylinder parent bore block can have
the advantage of aligned air handling and coolant transporting
features. The aligned features can include exhaust and intake
ports, cooling channels adjacent to and between the ports (e.g.,
across the port bridges), and cooling features around the
intermediate portion of each cylinder. Another advantage of using a
single 3-D printed core to create a cylinder block can include
improved sealing and fewer leaks. Additionally, uniformity of the
component walls (e.g., cylinder walls, turbulence features,
conduits) can be better controlled using 3-D printed casting
cores.
[0049] FIGS. 5C and 5D show a casting core assembly 575 for the
parent bore cylinder block 500 of FIGS. 5A and 5B. FIG. 5C is an
elevation view showing the casting cores for all four of the
cylinders in the parent bore cylinder block 500. FIG. 5D is a side
elevation view of the casting core assembly 575. The casting core
assembly 575 includes crank case portion cores for the intake side
577i and the exhaust side 577e of the cylinder block, cylinder
barrel (e.g., cylinder bore) cores 578, cores for oil cavities 579
on both the intake and exhaust sides of the cylinder block, and
cores for a cooling assembly 580. The cooling assembly cores 580
include exhaust side cooling channels 583, intake side cooling
channels 584, and cores for cooling features 585 that surround the
intermediate portion of each cylinder. In the cooling features
cores 585 are openings in each turbulator array for fuel injectors
586, as well as additional openings 587 for compression braking
valves, pressure sensors, and the like. Cores for the intake air
plenum 590 and the exhaust gas plenum 592 are also shown in FIGS.
5C and 5D.
[0050] FIG. 5E is an exploded view of the casting core assembly 575
shown in FIGS. 5C and 5D. In addition to cores for the crank case
portions 577i, 577e and cylinder barrel 578, cores for the oil
cavities 579, intake air plenum 590, and cooling assembly 580 can
be seen more completely in FIG. 5E. Additionally, the cores for
exhaust ports 596 and for intake ports 597 are shown. As in FIGS.
5C and 5D, the cooling assembly 580 includes exhaust side cooling
channels 583, intake side cooling channels 584, and cores to form
turbulence-inducing features on the intermediate portion of each
cylinder. FIG. 5E shows the exhaust gas plenum core 592 with the
cooling assembly 580.
[0051] FIG. 5F shows the casting core for the cooling features of
the parent bore cylinder block shown in FIGS. 5A and 5B. The
exhaust gas plenum core 593 and the exhaust port cores 596 are also
shown in FIG. 5F. Below the exhaust gas plenum core 593 are the
core portions 585 for the intermediate portion of each cylinder.
These core portions 585 include holes for forming cylindrical
turbulators 588 in arrays and breaks in the turbulator arrays for
fuel injectors 586. With the outer part of a casting or molding
assembly, the casting core shown in FIG. 5F can form a cooling
jacket with turbulators between an outer wall of the cooling jacket
and an outer surface of a cylinder in an intermediate portion of
the cylinder. As described above, the features (e.g., distinctive
structures, holes or orifices that form turbulators, tubes or ruts
that form conduits, channels, joints) of the casting core in FIG.
5F can be made using 3-D printing of ceramics, sand, or a
combination of both ceramic materials and sand to achieve the
required sizes and surface conditions.
[0052] Features described throughout this specification are
structures that are prominent or distinctive attributes, or
aspects, of a parent bore cylinder block or a casting core. These
features may be specified in terms of their size, purpose,
location, or mode of fabrication (i.e., 3-D printing, casting,
machining). Features of casting cores are used to create
complementary features in a cast metal product, and so a small
feature with a fine pitch between rows of features in a cast metal
product (e.g., cylinder block) necessitates a casting core with
small complementary features, including holes to make pegs, or
columns and walls to make holes and channels. Though cooling
features that create turbulence are described herein as cylindrical
pegs, cooling features can include any of pegs, walls, ridges,
ribs, and other protrusions from an outer wall of a cylinder. The
cooling features can be configured to create a coolant flow path
for cooling fluid. The shape of the cooling features can vary,
including being a combination of shapes. Some of the shapes that
could be used for cooling features include cylindrical pegs, pegs
with any of the following cross-sections: oval, ellipse, crescent,
triangle, quatrefoil, parallelogram, square, rectangle, trapezoid,
trapezium, kite, rhombus, pentagon, hexagon, heptagon, octagon,
nonagon, decagon, or a compound shape (i.e., a composite shape that
is two or more simple shapes combined). Further, the coolant flow
path may comprise other configurations than the turbulent flow
path. For example, instead of pegs, ridges or lands may be formed
to define elongate, spiral, helical, wavy, or rectilinear flow
paths. The use of 3-D printed casting cores, including those with
ceramic core portions, for parent bore cylinder blocks as described
above allows for finer spacing between cooling features. In some
implementations, spacing between cooling features can be between
1.5 mm to 10.0 mm, such as about 5 mm. The parent bore cylinder
block described herein can have all as-cast features, or it can
include as-cast features and machined features, particularly in and
around the cylinder bore.
[0053] An exemplary method 600 for making a parent bore cylinder
block for an opposed-piston engine is shown in FIG. 6. Initially in
this method, a 3-D printed casting core for a parent bore cylinder
block for an opposed-piston engine is created, as in 605. The
casting core can be fabricated as described above, using 3-D
printed sand, ceramic, or a combination of sand portions and
ceramic portions for the casting core. The 3-D printed core can be
assembled with cores for runners, risers, and gates, as well as a
drag and cope to form a molding assembly, as in 610. Molten metal
is poured into the molding assembly and cast into a parent bore
cylinder block, as in 615. Once the metal parent bore cylinder
block is ready, the casting core and other mold materials can be
removed, as in 620. Removal of the casting core and other mold
materials can include using a leaching solution to dissolve the
ceramic material, as well as washing away sand core portions.
Flash, runners, and risers can be machined off the final cast part
following removal of the casting core and mold, as in 625.
[0054] Not seen or described herein are many other features that
would be included in the parent bore cylinder block. Such features
typically include, without limitation, various internal channels,
borings, passageways, and so on for transporting fluids such as
lubricant and coolant throughout the block itself. Such features
are matters of design choice and are not part of this
disclosure.
[0055] Manifestly, in instances where the cylinder block of an
opposed-piston engine has cylinders that comprise liners or sleeves
(i.e., a "linered" or "sleeved" cylinder block), a cylinder liner
having the features shown in FIGS. 4A and 4B can be cast as a
single metal piece from a mold that includes a 3-D printed casting
core. A single-piece, or unitary, cylinder liner can be
advantageous over liners that are fabricated from many pieces
fitted together because of fewer junctions and connective parts
needed (e.g., O-rings). In contrast to conventional casting
techniques which may not be able to create the desired turbulators
(e.g., turbulent flow creating features), creating a 3-D printed
casting core, particularly a casting core that uses a ceramic in
some portions, can allow for the needed feature size and
texture.
[0056] Though parent bore cylinder blocks described herein above
are described as having one or more cylinders, it should be
appreciated that a parent bore cylinder block can be made for as
few as one cylinder, as well as for two or more cylinders,
preferably three cylinders. Further, in this disclosure, an engine
block is a component of an engine that includes a parent bore
cylinder block and can further include other components. Skilled
practitioners will comprehend how descriptions of a parent bore
cylinder block or methods pertaining to casting a parent bore
cylinder block can also be applied to an engine block. Those
skilled in the art will appreciate that the specific embodiments
set forth in this specification are merely illustrative and that
various modifications are possible and may be made therein without
departing from the scope of this specification.
* * * * *