U.S. patent application number 10/997443 was filed with the patent office on 2005-07-07 for single-ended barrel engine with double-ended, double roller pistons.
Invention is credited to Branyon, David P., Hauser, Bret R., Thomas, Charles Russell.
Application Number | 20050145207 10/997443 |
Document ID | / |
Family ID | 34714786 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050145207 |
Kind Code |
A1 |
Thomas, Charles Russell ; et
al. |
July 7, 2005 |
Single-ended barrel engine with double-ended, double roller
pistons
Abstract
An internal combustion barrel engine includes an engine housing
with a first and second end. An elongated power shaft is
longitudinally disposed in the engine housing and defines a
longitudinal axis. A combustion cylinder and a guide cylinder are
spaced apart and disposed on a common cylinder axis that is
generally parallel to the central axis. The cylinders each have an
inner end and an outer end, with the inner ends being closer to
each other. The outer end of the combustion cylinder is closed. An
intake system is operable to introduce a mixture of air and/or fuel
into the combustion cylinder. A track is supported between the
inner ends of the cylinders and has an undulating cam surface. The
track is moveable such that the portion of the cam surface most
directly between the cylinders undulates toward and away from the
inner end of the combustion cylinder. A double-ended piston
includes a combustion end disposed in the combustion cylinder so as
to define a combustion chamber between the combustion end and the
closed end of the combustion cylinder. A guide end is disposed in
the guide cylinder. A midportion extends between the combustion end
and the guide end and is in mechanical communication with the guide
surface of the track. A variable compression ratio device is
operable to move the track axially towards and away from the inner
end of the combustion cylinder so as to adjust the compression
ratio. Combustion occurs only in the combustion cylinder and does
not occur in the guide cylinder.
Inventors: |
Thomas, Charles Russell;
(Covington, LA) ; Hauser, Bret R.; (Flower Mound,
TX) ; Branyon, David P.; (San Antonio, TX) |
Correspondence
Address: |
Douglas L. Wathen
Gifford, Krass, Groh, Sprinkle,
Anderson & Citkowski, P.C.
280 N. Old Woodward Ave., Suite 400
Birmingham
MI
48009-5394
US
|
Family ID: |
34714786 |
Appl. No.: |
10/997443 |
Filed: |
November 24, 2004 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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10997443 |
Nov 24, 2004 |
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10426547 |
Apr 29, 2003 |
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6834636 |
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10997443 |
Nov 24, 2004 |
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10021192 |
Oct 30, 2001 |
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6698394 |
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10997443 |
Nov 24, 2004 |
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09937543 |
Sep 26, 2001 |
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09937543 |
Sep 26, 2001 |
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PCT/US00/07743 |
Mar 22, 2000 |
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10426547 |
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10263264 |
Oct 2, 2002 |
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6662775 |
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10426547 |
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09937543 |
Sep 26, 2001 |
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09937543 |
Sep 26, 2001 |
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PCT/US00/07743 |
Mar 22, 2000 |
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60377011 |
Apr 30, 2002 |
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60377072 |
Apr 30, 2002 |
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60377053 |
Apr 30, 2002 |
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60376638 |
Apr 30, 2002 |
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60244349 |
Oct 30, 2000 |
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60252280 |
Nov 21, 2000 |
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60260256 |
Jan 8, 2001 |
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60261060 |
Jan 11, 2001 |
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60267958 |
Feb 8, 2001 |
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60125798 |
Mar 23, 1999 |
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60134457 |
May 17, 1999 |
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60141166 |
Jun 25, 1999 |
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60147584 |
Aug 6, 1999 |
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60326857 |
Oct 3, 2001 |
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60125798 |
Mar 23, 1999 |
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60134457 |
May 17, 1999 |
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60141166 |
Jun 25, 1999 |
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60147584 |
Aug 6, 1999 |
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Current U.S.
Class: |
123/48R |
Current CPC
Class: |
F01B 3/0035 20130101;
F02B 47/02 20130101; F05C 2253/16 20130101; Y02T 10/126 20130101;
F02B 75/26 20130101; F01B 3/0085 20130101; F02F 7/0087 20130101;
Y02T 10/121 20130101; F04B 41/04 20130101; F01B 3/0005 20130101;
F04B 39/1073 20130101; F02B 57/08 20130101; F02B 75/02 20130101;
F02B 2075/027 20130101; F02B 41/04 20130101; F02B 51/04 20130101;
F02B 75/36 20130101; F02B 1/12 20130101; Y02T 10/12 20130101; F02B
75/04 20130101; F01B 3/04 20130101; F02B 3/06 20130101; F02B
2075/025 20130101 |
Class at
Publication: |
123/048.00R |
International
Class: |
F02B 075/04 |
Claims
I claim:
1-23. (canceled)
24. An internal combustion engine comprising: a combustion cylinder
and a pumping cylinder spaced apart and disposed on a common
cylinder axis, the cylinders each having an inner end and a outer
end with the inner ends being closer to each other; an intake
system operable to introduce a mixture of air and/or fuel into the
combustion cylinder; and a double-ended piston comprising: a
combustion end movable within the combustion cylinder and operable
to compress the mixture of air and/or fuel; a pumping end movable
within the pumping cylinder; a track supported between the inner
ends of the combustion cylinder and the pumping cylinder, the track
having an undulating surface, the track being movable such that the
portion of the surface most directly between the inner ends of the
cylinders undulates toward and away from the inner ends of the
cylinders; the double-ended piston further comprising a midportion
extending between the combustion end and the pumping end, the
midportion being in mechanical communication with the surface of
the track such that as the track moves, the midportion urges the
combustion end of the piston outwardly within the combustion
cylinder to compress the mixture and allows the combustion piston
to move inwardly within the combustion cylinder as the mixture
expands, the pumping end moving with the midportion such that as
the combustion end moves outwardly, the pumping end moves inwardly
in the pumping cylinder and as the combustion end moves inwardly
the pumping end moves outwardly, the pumping end and the pumping
cylinder cooperating to compress a gas; and a variable compression
device operable to move the track axially towards and away from the
inner end of the combustion cylinder so as to adjust the
compression ratio.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of the following
patent applications: U.S. patent application Ser. No. 10/021,192,
filed Oct. 30, 2001, and U.S. patent application Ser. No.
10/263,264, filed Oct. 2, 2002. This application also claims
priority from U.S. Provisional Patent Application Ser. No.
60/377,011, filed Apr. 30, 2002; No. 60/377,072, filed Apr. 30,
2002; No. 60/377,053, filed Apr. 30, 2002; and No. 60/376,638,
filed Apr. 30, 2002.
[0002] U.S. patent application Ser. No. 10/021,192, in turn, claims
priority from U.S. Provisional Patent Application Ser. No.
60/244,349, filed Oct. 30, 2000; No. 60/252,280, filed Nov. 21,
2000; No. 60/260,256, filed Jan. 8, 2001; No. 60/261,060, filed
Jan. 11, 2001; and No. 60/267,958, filed Feb. 9, 2001; and is a
continuation-in-part of U.S. patent application Ser. No.
09/937,543, filed Sep. 26, 2001, which is a U.S. National Phase of
PCT/US00/07743, filed Mar. 22, 2000, which claims priority from
U.S. Provisional Patent Application Ser. No. 60/125,798, filed Mar.
23, 1999; No. 60/134,457, filed May 17, 1999; No. 60/141,166, filed
Jun. 25, 1999, and No. 60/147,584, filed Aug. 6, 1999.
[0003] U.S. patent application Ser. No. 10/263,264, in turn, claims
priority from U.S. Provisional Patent Application Ser. No.
60/326,857, filed Oct. 3, 2001, and is a continuation-in-part of
U.S. patent application Ser. No. 09/937,543, filed Sep. 26, 2001,
which is a U.S. National Phase of PCT/US00/07743, filed Mar. 22,
2000, which claims priority from U.S. Provisional Patent
Application Ser. No. 60/125,798, filed Mar. 23, 1999, No.
60/134,457, filed May 17, 1999, No. 60/141,166, filed Jun. 25,
1999, and No. 60/147,584, filed Aug. 6, 1999.
[0004] The content of all of the above-identified U.S., PCT and
provisional patent applications are incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0005] The present invention relates to the use of double-ended,
double roller pistons in single-ended barrel engines.
BACKGROUND OF THE INVENTION
[0006] An engine with the ability to vary its compression ratio
during operation can significantly improve efficiency and power
density for compression-ignited (CI), stoichiometric spark-ignited
(SSI), homogeneous charge compression-ignited (HCCI) and lean
combustion spark-ignited (LCSI) applications. Variable compression
ratio (VCR) abilities allow an engine's compression ratio to be
lowered during high load conditions to prevent detonation or to
limit peak cylinder pressure and allow the compression ratio to be
raised to improve thermal efficiency at lower load conditions.
Variable compression ratio can also be used to phase or supplement
the phasing of combustion in homogeneous charge compression engines
and to broaden the range of air-fuel ratio that can be used in lean
combustion spark-ignited engines. In nearly all engine
applications, variable compression ratio is especially beneficial
when used in combination with supercharging, where the combination
of variable compression ratio and supercharging substantially
multiplies the benefits of both features.
[0007] In spite of their benefit and applications, engines with
variable compression ratio abilities have not been used in
commercial applications due to issues of extreme complexity, lack
of long-term durability and prohibitively high costs. Several
approaches to varying compression ratio in conventional
slider-crank engines have been proposed and in some cases have been
implemented. One type of variable compression ratio device for use
in slider-crank engines is shown in the following publications: PCT
Publication No. WO 92/09798, PCT Publication No. WO 92/09799, U.S.
Pat. No. 5,329,893; and U.S. Pat. No. 5,443,043, all of which are
assigned to Saab. The Saab design includes a traditional in-line
slider-crank engine in which the head and cylinder bank are tilted
to vary compression ratio. The design preferably also includes an
external supercharger for providing boost air to the engine. Using
stoichiometric spark-ignition, the Saab variable compression ratio
engine has demonstrated a 30% improvement in fuel economy in
combined city and highway driving cycles. In spite of its benefits,
Saab's pivoting head design is cumbersome and complex, has
potential sealing issues and is prohibitively expensive. Other
attempts to vary compression ratio in conventional slider-crank
engines are generally inferior to the Saab technique for various
reasons.
[0008] Another means of varying compression ratio in slider-crank
engines is achieved through variable valve timing. Variable valve
timing is a very good technology for extending an engine's torque
curve over a broad range of engine speed and for some Miller cycle
variable compression ratio applications. However, the usefulness of
variable valve timing for other variable compression ratio
applications is very limited. Varying compression ratio with
variable valve timing relies on decreasing the effective stroke of
the engine to lower compression ratio. This results in significant
penalties in the effective displacement of the engine as
compression ratio is lowered. In nearly all variable compression
ratio applications, compression ratio must be lowered when peak
power is needed. A reduction in the effective engine displacement
at this time significantly reduces the peak power capability of the
engine and usually offsets any benefits that can be gained by a
varying compression ratio.
[0009] In contrast to conventional slider-crank engines,
single-ended barrel engines by nature provide a structure that is
better suited to utilize a simple and effective means of varying
compression ratio. The engine structure of a single-ended barrel
engine allows the engine's compression ratio to be easily and
simply varied by axially changing the position of the engine's
central track or cam drive mechanism. By moving the track axially,
the pistons can be brought closer to or further away from top dead
center (TDC), thus, varying the engine's compression ratio. This
method of varying compression ratio is both durable and inexpensive
and is more effective than variable valve timing methods of varying
compression ratio in most applications.
[0010] A single-ended barrel engine design is also advantageous
because it allows piston motion to be independently optimized for
the intake, compression, combustion and exhaust cycles. This level
of optimized piston motion is not possible in slider-crank engines,
which are restricted to sinusoidal piston motion or in double-ended
barrel engines, which cannot independently optimize piston motion
for each cycle.
[0011] While single-ended barrel engines provide a simple and
inexpensive means of varying compression ratio and the ability
independently optimize piston motion for various engine cycles,
prior art single-ended barrel engines with these abilities have yet
to demonstrate a piston structure that is both structurally and
kinematically feasible at normal engine speeds. Prior art
single-ended barrel engines employ single-ended or double-ended,
single roller piston designs that lack critical crosshead and
roller support qualities needed for a feasible design.
SUMMARY OF THE INVENTION
[0012] The present invention provides improvements to barrel
engines by mating the simplified variable compression ratio and
optimized piston motion abilities of a single-ended barrel engine
with a rigid and durable crosshead piston design. A unique
double-ended, double roller piston is employed that uses one end
for combustion and the other end as a crosshead guide means to
reduce side loading on the piston. In some embodiments, the barrel
engine includes a variable compression ratio device, while in other
embodiments it includes an integral supercharger. In still other
embodiments, the engine includes a non-sinusoidal cam surface,
which causes the combustion ends of the pistons to move
non-sinusoidally. In some embodiments, these features are used in
combination with one another.
[0013] In one embodiment, the internal combustion barrel engine
includes an engine housing with a first end and a second end. An
elongated power shaft is longitudinally disposed in the engine
housing and defines a longitudinal axis of the engine. A combustion
cylinder and a guide cylinder are spaced apart and disposed on a
common cylinder axis that is generally parallel to the central
axis. The cylinders each have an inner end and an outer end, with
the inner ends being closer to each other. The outer end of the
combustion cylinder is closed. An intake system is operable to
introduce a mixture of air and/or fuel into the combustion
cylinder. A track is supported between the inner ends of the
combustion cylinder and the guide cylinder. The track has an
undulating cam surface. The track is moveable such that the portion
of the cam surface most directly between the inner ends of the
cylinders undulates toward and away from the inner end of the
combustion cylinder. A double-ended piston includes a combustion
end moveably disposed in the combustion cylinder such that a
combustion chamber is defined between the combustion end of the
piston and the closed end of the combustion cylinder. A guide end
of the piston is moveably disposed in the guide cylinder. A
midportion of the piston extends between the combustion end and the
guide end. The midportion is in mechanical communication with the
guide surface of the track such that as the track moves, the
midportion urges the combustion end of the piston outwardly within
the combustion cylinder to compress the mixture in the combustion
chamber and allows the combustion end of the piston to move
inwardly within the combustion chamber as the mixture within the
combustion chamber expands. The guide end moves with the midportion
such that as the combustion end moves outwardly, the guide end
moves inwardly in the guide cylinder, and as the combustion end
moves inwardly, the guide end moves outwardly. The guide end and
the guide cylinder cooperate to guide the motion of the
double-ended piston. A variable compression device is operable to
move the track axially towards and away from the inner end of the
combustion cylinder so as to adjust the compression ratio.
Combustion occurs only in the combustion cylinder and does not
occur in the guide cylinder.
[0014] In one alternative embodiment, the guide end of the piston
is a pumping end and the guide cylinder is a pumping cylinder with
a closed outer end. The pumping end and the pumping cylinder
cooperate to compress a gas. The engine further includes a valve
assembly for providing the gas to the pumping cylinder and venting
compressed gas from the pumping cylinder. A compressed gas conduit
is in fluid communication with the valve assembly and the intake
system such that the compressed gas from the pumping cylinder is
provided to the combustion chamber so as to supercharge the
engine.
[0015] In another embodiment of the present invention, a barrel
engine includes an engine housing with a first end and a second
end. An elongated power shaft is longitudinally disposed in the
engine housing and defines a longitudinal axis of the engine. A
combustion cylinder and a guide cylinder are spaced apart and
disposed on a common cylinder axis that is generally parallel to
the central axis. The cylinders each have an inner end and an outer
end with the inner ends being closer to each other. The outer end
of the combustion cylinder is closed. An intake system is operable
to introduce a mixture of air and/or fuel into the combustion
cylinder. A track is supported between the inner ends of the
combustion cylinder and the guide cylinder. The track has an
undulating cam surface. The track is moveable such that the portion
of the cam surface most directly between the inner ends of the
cylinders undulates toward and away from the inner end of the
combustion cylinder. The undulating cam surface defines a
non-sinusoidal shape. A double-ended piston includes a combustion
end moveably disposed in the combustion cylinder such that a
combustion chamber is defined between the combustion end of the
piston and the closed end of the combustion cylinder. A guide end
of the double-ended piston is moveably disposed in the guide
cylinder; A midportion extends between the combustion end and the
guide end. The midportion is in mechanical communication with the
cam surface of the tracks such that as the track moves, the
midportion urges the combustion end of the piston outwardly within
the combustion cylinder to compress the mixture in the combustion
chamber and allows the combustion end of the piston to move
inwardly within the combustion cylinder as the mixture within the
combustion chamber expands. The motion of the piston is
non-sinusoidal. The guide end moves with the midportion such that
as the combustion end moves outwardly, the guide end moves inwardly
in the guide cylinder and as the combustion end moves inwardly, the
guide end moves outwardly. The guide end and the guide cylinder
cooperate to guide the motion of the double-ended piston.
Combustion occurs only in the combustion cylinder and does not
occur in the guide cylinder.
[0016] In an alternative embodiment, the engine further includes a
variable compression ratio device operable to move the track
axially towards and away from the inner end of the combustion
cylinder so as to adjust the compression ratio. In yet a further
alternative embodiment, the guide end of the piston comprises a
pumping end and the guide cylinder comprises a pumping end and the
guide cylinder comprises a pumping cylinder with a closed outer
end. The pumping end and the pumping cylinder cooperate to compress
a gas. The engine further comprises a valve assembly for providing
a gas to the pumping cylinder and venting compressed gas from the
pumping cylinder. A compressed gas conduit is in fluid
communication with the valve assembly and the intake system such
that the compressed gas from the pumping cylinder is provided to
the combustion chamber so as to supercharge the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a cross-sectional view of a prior art single-ended
barrel engine;
[0018] FIG. 2 is a cross-sectional view of a prior art double-ended
barrel engine;
[0019] FIG. 3 is a perspective view of a first embodiment of a
double-ended piston for use with the present invention;
[0020] FIG. 4 is a side view of the piston of FIG. 3;
[0021] FIG. 5 is a cross-sectional view of the piston of FIG. 3,
taken along lines 5-5;
[0022] FIG. 6 is a cross-sectional view of a first embodiment of a
single-ended barrel engine according to the present invention;
[0023] FIG. 7 is a perspective view of a second embodiment of a
double-ended piston for use with the present invention;
[0024] FIG. 8 is a cross-sectional view of a second embodiment of a
barrel engine according to the present invention;
[0025] FIG. 9 is a graph showing one version of a non-sinusoidal
piston motion profile for use with the present invention; and
[0026] FIG. 10 is a graph comparing two piston motion profiles at
top dead center.
DETAILED DESCRIPTION OF THE INVENTION
[0027] A single-ended barrel engine design presents a unique
opportunity to vary compression ratio by simple and inexpensive
means, and to optimize piston motion. A single-ended barrel engine
is one that contains only one central track for driving piston
motion, with the combustion event occurring on only one side of the
track and one end of the engine. This configuration is less
complicated than opposing piston and double-ended barrel engine
designs and provides an engine structure that allows the engine's
compression ratio to be easily and simply varied by axially
changing the position of the track. A single-ended barrel engine
design also allows piston motion to be independently optimized for
the intake, compression, combustion and exhaust cycles because
power is produced on only one side of the track. FIG. 1 illustrates
an example of a single-ended barrel engine.
[0028] The engine 10 in FIG. 1 is merely representative of the
general configuration of an engine referred to herein as a barrel
engine. It includes a drive or power shaft 12 with a plurality of
cylinders 22 arranged about the power shaft 12. Single cylinder
variations are also possible. The central axis of each of the
cylinders 14 may be generally parallel to the power shaft 12.
Alternatively, the axes of the cylinders 14 may be tilted slightly
outwardly or inwardly with respect to the power shaft 12. A track
or cam plate 16 is preferably connected to the power shaft 12 such
that the two rotate in unison. The track 16 surrounds and extends
outwardly from the power shaft 12 and has an undulating cam surface
18. As the power shaft 12 is rotated about its longitudinal axis,
the surface 18 of the track 16 undulates closer to and farther from
the cylinders 14. Pistons 20 are moveably positioned in the
cylinders 14 and define a combustion chamber 22 between each piston
and the upper end of its respective cylinder 14. The pistons 20 are
interconnected with the track 16 such that as the track rotates,
the pistons are caused to reciprocate within the cylinders 14. In
the embodiment illustrated in FIG. 1, the pistons have a crown
portion that faces the combustion chamber and a lower end with
rollers 26 that ride on the undulating surface 18 of the track
16.
[0029] As will be clear to those of skill in the art, as the power
shaft 12 rotates and the pistons 20 reciprocate within their
respective cylinders, the various strokes of a combustion cycle can
be defined. The cam surface 18 of the track 16 may have a generally
sinusoidal shape, thereby corresponding to the standard sinusoidal
reciprocal motion typical of a crank driven piston. Alternatively,
the surface of the track may be non-sinusoidal in order to optimize
piston motion for the intake, compression, combustion and exhaust
strokes. The track is generally disposed in a plane perpendicular
to the power shaft and the cam surface is generally disposed at a
constant distance from the axis of the power shaft.
[0030] In the field of single-ended barrel engines, there are a few
designs in which one or more pistons are attached to one another by
a rigid or hinged means. It should be noted that this application
refers to single-ended barrel engines in which each piston unit is
free to reciprocate independently from other pistons within the
engine. It should also be noted that the single-ended barrel
engines discussed are assumed to include a drive means consisting
of a wobble, swash, wave-cam, or similar lobed cam or angled plate
device. One type of engine within this class of single-ended barrel
engines is the type illustrated in FIG. 1.
[0031] In the development of the present invention it was found
that double-ended, double roller pistons are preferred in order to
accept the side load from the roller to cam surface interface while
also keeping reciprocating mass to a minimum. Double-ended pistons
are advantageous in that they provide a rigid crosshead guide
mechanism that is lighter than other types of guide strategies used
in barrel engines. In barrel engines, extremely careful design
considerations must be made to minimize piston mass in order to
limit Hertzian contact stress at the roller to cam surface
interface. In the development of the present invention it was
determined that double-ended, double roller pistons were the
preferred type of piston design that is both rigid enough and light
enough to provide a competitive engine speed range in a barrel
engine.
[0032] FIG. 2 illustrates a double-ended barrel engine utilizing
double-ended, double roller pistons 30. This type of double-ended
piston includes upper 32 and lower 34 rollers that interface with a
cam track 36. Double-ended barrel engines differ from single ended
barrel engines because they have firing events on both ends of the
engine and to both sides of the cam track. Unlike prior art
single-ended barrel engines, in order to allow firing events on
both ends of the engine, double-ended barrel engines typically
employ double-ended pistons. Another double-ended barrel engine,
using double-ended, double roller pistons, is shown in U.S. Pat.
No. 4,492,188 to Palmer et al.
[0033] U.S. Pat. No. 1,867,504 to Franklin illustrates a barrel
engine using an alternative type of double-ended piston design in
which a single roller travels within a cam-like grove in the drive
means. While this type of double-ended piston provides desirable
crosshead features, it does riot provide sufficient support for
both ends of the roller. In the extreme environment of an internal
combustion engine, variations of this single-roller design will not
be capable of sustaining normal engine speeds. The design of the
double-ended, double roller pistons illustrated in FIG. 2, however,
has been proven in running double-ended barrel engines and in a
multitude of double-ended compressors. The success of these devices
serves as testimony to the benefit of double-ended, double roller
piston designs.
[0034] Double-ended pistons work well in double-ended barrel
engines. However, because double-ended barrel engines must consider
firing events on both ends of the engine, they cannot vary
compression ratio by axially changing the position of the central
cam drive means. If this method of varying compression ratio is
attempted in a double-ended barrel engine, as compression ratio is
increased on one end of the engine by moving the drive means
axially toward that end, it is reduced on the other end, and vice
versa. What is beneficial to one end of the engine is detrimental
to the other. This relationship prevents the most simplified means
of varying compression ratio from being used in double-ended barrel
engines, making it equally difficult to vary compression ratio in
double-ended barrel engines as it is to vary compression ratio in
slider-crank engines.
[0035] Problems are also encountered when attempts are made to
independently optimize piston motion for the intake, compression,
combustion and exhaust cycles in a double-ended barrel engine.
These problems again result from the need to consider firing events
on opposite ends of the engine. In a double-ended barrel engine
with double-ended pistons, when one end of a piston is traveling
away from its respective top dead center (TDC), the other end is
traveling toward its respective top dead center. Therefore, for
example, when one end of the piston is traveling away from top dead
center during a power cycle, the other end must be traveling toward
its respective top dead center during either a compression or an
exhaust cycle. This is true for each of the operating cycles such
that it is not possible to optimize each cycle independently for
both ends the engine.
[0036] The present invention is unique in part because it uses
double-ended, double roller pistons of the general type illustrated
in FIG. 2, but only uses one end of the pistons for combustion and
the other end to provide a rigid crosshead guide means. Since
combustion only occurs on one side of the piston, the engine does
not have to consider firing on an opposite end of the engine. This
allows the present invention to mate the simplified variable
compression ratio and optimized piston motion abilities of a
single-ended barrel engine with a rigid and durable double-ended,
double roller crosshead piston design.
[0037] FIGS. 3-5 illustrate a double-ended, double roller piston,
as modified in the present invention to operate in a single-ended
barrel engine with combustion acting on only one end of the piston.
The piston 50 has a combustion end 52, which would be received in a
combustion cylinder, and an opposite guide end 54, which would be
received in a guide cylinder. As shown, the combustion end 52 is
configured like a typical piston, with a closed upper crown portion
that includes piston ring grooves for receiving rings. The guide
end 54 may be open, as shown, or configured in other ways. The
piston 50 has a midportion 56 interconnecting the combustion end 52
and guide end 54. The midportion 56 has a pair of opposed rollers
58 and 60, which engage upper and lower cam surfaces of a track in
a barrel engine. The mid portion may be constructed such that it is
in sliding contact with the outer edge of the track in order to
prevent undesired rotation of the piston about its longitudinal
axis. Other anti-rotation designs may also be utilized. In some
designs, oil galleries may be included to provide pressurized
lubrication to the roller pins. The rollers 58 and 60 are
illustrated as hollow rollers with a pin extending therethrough.
Preferably, the rollers and pins may instead be integrally formed.
Alternatively, two or more side-by-side rollers may share a pin, so
as to reduce the scrubbing due to slight variations in linear speed
on the inside and outside of the cam surface.
[0038] The various parts of the piston may be either cast or
forged, either separately or as a single unit, or formed in any
other way known to those of skill in the art. Preferably, the
piston 50 is unitarily formed such that the ends 52 and 54, and
midportion 56, are integrally formed and rigid with respect to one
another. In some designs, it will be preferable for the crown
portions of the piston to be formed separately and welded to the
main body of the piston using an electron beam or attached by
various other means that will be familiar to those of skill in the
art. The diameter of the combustion end 52 and guide end 54 may
differ from one another or may be the same. Also, the ends are not
required to have circular perimeters, but may instead have
different shapes. For purposes of the present invention, a cylinder
that receives a piston may have a shape other than strictly
cylindrical. For example, it may be somewhat rectangular or oval in
shape, and still fall within the meaning of "cylinder," as used
herein.
[0039] Unlike the single-ended pistons or double-ended, single
roller pistons found in prior-art single-ended barrel engines, the
modified double-ended, double roller pistons, used in the present
invention retain the critical crosshead and roller support
qualities of a double-ended, double roller piston, yet still allow
compression ratio to be easily varied and piston motion to be
easily optimized. Therefore, the present invention provides a
better variable compression ratio engine platform and a better
platform for optimizing piston motion.
[0040] FIG. 6 illustrates a cross sectional view of a single-ended
barrel engine 70 which employs the modified double-ended, double
roller piston 50 illustrated in FIG. 3. The modified double-ended,
double roller pistons 50 can be seen with the combustion end 52 in
a combustion cylinder 72 and the guide end 54 in a guide cylinder
74. FIG. 4 also illustrates an example of a variable compression
ratio device 76, with portions disposed below and above the track
78. In this arrangement, the track 78 has been splined or attached
by other means to the central power shaft 80, such that the track
78 is axially slidable along the power shaft 80 while still
rotating in unison with the power shaft. It may also be desirable
to lock or fuse the track to the central power shaft such that both
the track and the power shaft are axially slidable within the
supports for the power shaft. The latter design in which the power
shaft and track are axially slidable as a single unit can help to
prevent side-loading of the piston rollers by preventing spline
tolerances from becoming exaggerated at the outermost ends of the
track.
[0041] In order to raise compression ratio, the lower portion of
the variable compression ratio device 76 is expanded while the
upper portion of the device is simultaneously compacted, causing
the track 78, along with all of the pistons 50, to move towards the
closed ends of the combustion cylinders 72. In some engine
configurations, it may only be necessary to provide a single lower
portion of the variable compression ratio device. As the pistons
are moved closer to the head of the engine, their top dead center
clearance volume (the volume between the upper end of the
combustion cylinder 72 and the combustion end 52 of the piston at
top dead center) is reduced, thereby raising the engine's
compression ratio. In order to lower the engine's compression
ratio, the lower portion of the variable compression ratio device
76 is compacted while the upper portion of the device is
simultaneously expanded, causing the track 78, along with all of
the pistons, to move away from the closed end of the combustion
cylinders 72. This increases the top dead center clearance volume,
thereby lowering the engine's compression ratio.
[0042] As shown, the upper and lower rollers 58 and 60 of the
pistons 50 are in mechanical communication with the track 78 such
that as the track rotates, the pistons are urged upwardly and
downwardly in the cylinders 72 and 74. The track 78 may be said to
have an upper cam surface 82 and a lower cam surface 84 which are
engaged by the rollers of the pistons 50.
[0043] It should be noted that FIG. 6 illustrates the engine 70
without an intake system for introducing a mixture of air and/or
fuel to the combustion chamber, defined between the combustion end
52 of the piston 50 and the closed upper end of the cylinder 72.
Instead, a cylinder head 86 is shown as a block. The present
invention may be practiced with any type of intake system operable
to introduce a mixture of air and/or fuel into the combustion
cylinder. This may include poppet-style valves in the head, ports
in the head, or sidewalls of the cylinder, or any other approach
known to those of skill in the art. Likewise, any type of valve
actuation mechanism may be used. The upper end of the combustion
cylinder 72 is defined as "closed" herein since compression occurs
therein, despite the fact that valves or ports may be provided
which selectively open the upper end of the combustion cylinder 72
to allow the introduction or exhausting of gases from the
cylinders.
[0044] The lower end of the engine 80 is shown as being open to the
guide cylinders 74. Preferably, an engine cover is provided so as
to avoid the introduction of dirt or debris to the guide cylinder
74. It should also be appreciated that an oiling system will be
provided so as to lubricate the engine.
[0045] As will be clear to those of skill in the art, other
approaches to longitudinally moving the track 78 and/or power shaft
80 with respect to the combustion cylinder 72 may be used,
including any approach currently known to those of skill in the
art, or yet to be developed. Variable compression ratio devices
such as disclosed in co-pending U.S. patent application Ser. No.
10/021,192 may also be used herein.
[0046] As discussed in the background, variable compression ratio
is especially beneficial when used in combination with
supercharging, where the combination of variable compression ratio
and supercharging substantially multiplies the benefits of both
features. In U.S. patent application Ser. No. 10/263,264, which is
incorporated herein, the guide end of a double-ended, double roller
piston has been modified to compress boost air in a single-ended
barrel engine. This integral supercharger design retains the
critical crosshead qualities of a double-ended, double roller
piston design while using the guide end of the piston for useful
work. In this case, the guide end of the piston may be referred to
as a pumping end and the guide cylinder may be referred to as a
pumping cylinder.
[0047] FIG. 7 illustrates a double-ended, double roller piston 90
for use in the embodiment of the present invention with an integral
supercharger. The piston 90 has a combustion end 92, a pumping end
94, and a midportion 96 extending therebetween and interconnecting
the combustion end and pumping end. The piston 90 may be assembled
into a barrel engine, according to the present invention, wherein
the guide cylinders have closed outer ends so that the pumping end
94 and pumping cylinder cooperate to compress air. This compressed
air, in turn, may be routed to the intake system for the combustion
end of the engine, so as to supercharge the engine. In alternative
configurations, the pumping cylinder may be used to compress air
for other applications or to compress other types of gases.
[0048] FIG. 8 schematically illustrates an alternative embodiment
of a barrel engine, according to the present invention, utilizing a
double-ended piston with a combustion end and a pumping end. FIG. 8
illustrates an alternative piston design, though the design of FIG.
7 is preferred. Referring to FIG. 8, a reciprocating piston
assembly 140 is assembled within two co-axial cylinder bores, a
combustion cylinder 112 and an air compression or pumping cylinder
114. The piston 110 includes a combustion end 116 in the combustion
cylinder 112 and a pumping end 118 in the pumping cylinder 114. The
ends are interconnected by a midportion 120. The ends 116 and 118
and the midportion 120 may be formed as a single piece, or may be
formed of multiple pieces. The midportion 120 of the piston is
connected to a rotating track 122 via rollers 124. The track 122 is
connected to a power shaft 124 such that the track 122 and shaft
124 rotate in unison about the axis of the shaft. The track 122 has
undulating upper and/or lower cam surfaces such that as the track
rotates, the upper and/or lower surfaces move toward and away from
the open ends of the cylinders. As will be clear to those of skill
in the art, the portion of the track between the cylinders will
undulate toward one of the cylinders as it undulates away from the
other. As the track rotates, the ends 116 and 118 are urged
upwardly and downwardly in their cylinders 112 and 114,
respectively. Consequently, combustion in the combustion cylinder
112 results in the track being urged to rotate. Provisions may be
included to allow the track to be axially slidable in order to vary
compression ratio.
[0049] As shown, the outer end of the combustion cylinder 112 is
closed off by a head with traditional poppet style valves for
supplying an intake air or an intake mixture to a combustion
chamber defined in the combustion cylinder 112 between the
combustion end of the piston and the head. The "intake system" may
include one or more intake valves for controlling intake flow as
well as one or more fuel injectors. In whatever configuration, the
intake system is operable to introduce a combustible mixture to the
combustion chamber, whether the combustible mixture is premixed
prior to introduction to the chamber, or whether the mixture is
created within the chamber. One or more traditional poppet style
exhaust valves are also provided for exhausting combustion products
from the combustion chamber. Other types of valves may be provided
for controlling the flow of intake and exhaust to and from the
combustion chamber, including, but not limited to, two-stroke style
ports and rotary valves.
[0050] The combustion end of the engine may be used for two stroke
or four stroke stoichiometric spark-ignition, lean combustion
spark-ignition, diesel or homogenous charge compression ignition
combustion strategies. Additionally, the engine may consist of
multiple combustion and pumping cylinders. In one preferred
embodiment, the combustion end provides a four-stroke spark
ignition combustion strategy, with increased power density and
efficiency due to the supercharging effect of the compression
features of the engine. At the other "end" of the engine, a pumping
or compression chamber is defined within the pumping cylinder 114
between the pumping end 118 of the piston and a valve plate 126
which acts as a "head" for the compression chamber. As will be
clear to those of skill in the art, as the track undulates and ends
of the piston move upwardly and downwardly in their respective
cylinders, the chambers expand and contract.
[0051] In the illustrated embodiment, the valve-plate 126 has
reed/flapper valves for intake 128 and exhaust 130 of air or gas
for the pumping cylinder 114. As shown, a flapper valve 130 covers
an exhaust passage through the valve plate 126, which communicates
with the compression chamber. The flapper valve 130 is preferably
biased to a position wherein it covers and seals the passages. As
will be clear to those of skill in the art, the exhaust flapper
valve 130 is on the "outside" of the valve plate 126 so that the
exhaust flapper valve rests against the surface opposite the piston
120. An intake flapper valve 128 covers an intake passage through
the valve plate 126. The intake flapper valve 128 is biased to a
position where it covers and seals the intake passage. The intake
flapper valve is positioned on the "inside" of the valve plate 126
so that it is facing the piston and may be considered to be
"inside" the compression chamber. The intake flapper valve and the
exhaust flapper valve each act as one way flow valves, with the
intake flapper valve allowing one way flow into the chamber and the
exhaust flapper valve allowing one way flow out of the chamber. As
shown, the valve plate is preferably a flat or substantially flat
plate, which minimizes the volume of the compression chamber and
simplifies production of the valve assembly. However, the valve
plate may alternatively be domed, slanted, or otherwise shaped for
some applications. Also, while the flapper valves are preferably
parallel to the valve plate in their closed positions, they may
also be slanted or positioned differently than shown.
[0052] As will be clear to those of skill in the art, the portion
of the engine illustrated in FIG. 8 preferably is replicated
concentrically about the shaft 124 such that multiple combustion
and pumping cylinders are provided. A circular outer plenum 132,
concentric with the shaft 124, preferably connects the output of
boosted air from all air compression chambers as regulated by
exhaust reed valves. A similar concentric plenum for ambient intake
air is preferably provided inboard of the exhaust plenum. Air is
ducted to this intake plenum from the engine air intake and
filtration system.
[0053] As the reciprocating piston 110 moves to enlarge the volume
of the air in the pumping chamber, the reduced pressure within the
chamber acts to open the intake reed valve 128 and air is received
from the intake air plenum. That is, as the volume in the chamber
is expanded, a vacuum is formed and the relative pressure outside
the engine (typically ambient pressure) acts to press against the
intake flapper valve until the bias of the flapper valve, which
retains it a closed position, is overcome and it flexes away from
the passage. At this point air can flow through the passage into
the compression chamber. The bias of the exhaust reed valve 130
together with the relatively high boost air pressure in the exhaust
plenum keeps the exhaust passage sealed off during this process. As
the piston assembly 110 moves to reduce the volume in the
compression chamber, the increased pressure within the chamber
allows the intake reed valve 128 to return to its closed position.
When the pressure within the cylinder 114 increases to a point
sufficiently above the pressure in the plenum 132, the bias of the
exhaust reed valve is overcome and it is urged open so the
compressed air in the chamber is expelled to the plenum 132. A
valve "backer" 134 may be included to provide structural support to
the exhaust valve 130 during the opening period.
[0054] The compressed or boost air is ducted from the plenum 132 to
an intake plenum 136 for the combustion cylinders. Alternatively,
compressed air from individual compression chambers may be brought
into individual combustion chambers, rather than the shared plenum.
The same may be true for the intake to the compression chambers. As
shown schematically in FIG. 8, the boost air pressure is preferably
controlled by a wastegate mechanism 138 operable to vent to the
atmosphere. A throttle 140 is preferably provided downstream of the
wastegate 138. Another throttle may be included prior to the
compressor inlet (not shown) depending upon the control strategy
desired. A throttle prior to the compressor inlet, or controlling
the flow of air to the intake plenum, could effectively turn off
the compression stage of the engine or throttle it back. This
allows the compression to effectively be turned on and off.
Alternatively, the waste gate may be used. As yet another
alternative, a disabling feature may be used for disabling the
compressor feature. An example is an opening device that presses
either the intake or exhaust flapper valve open and holds it in
this position so that the piston is not effective at compressing
air. This disabling device, commonly called a valve unloader, may
consist of rods or fingers which hold the flapper valves open or
closed or may be of the sliding leaf type used in MeritorWabco
.RTM. compressors. Common practice in reciprocating compressors
such as the one in this engine is to unload the suction or intake
valve of the compressor, although it may also be beneficial to
unload the exhaust valve instead of the intake or in combination
with the intake to further minimize unloaded pumping losses.
[0055] The present invention provides numerous benefits over a
typical single ended barrel engine design. Boost air is available
to the combustion process in a more compact package than by more
traditional means such as add-on turbochargers or superchargers.
Because the compressor is an integral part of the design of the
engine, the cost is potentially reduced as well. Boost air is
created through the use of proven technology; involving
reciprocating pistons and reed valves as opposed to precision
high-speed turbine machinery. A small amount of piston inertial
force is counteracted by the compression of the boost air. This
results in some reduction of contact force on the piston rollers.
The availability of boost air increases the flexibility of the
barrel engine to include both 2-stroke and 4-stroke engine cycles.
Without boost, a barrel engine has little ability to provide a
fresh air charge to the cylinder during the intake process. This is
particularly important in 2-stroke cycles where the pressure
differential between bore and manifold (or crankcase) is limited.
Typically, unboosted 2-stroke engines are crankcase scavenged for
this reason. Crankcase scavenging is not practical for barrel
engine configurations. This invention provides a relatively simple
way to add boost to the barrel engine and add viability as a
2-stroke machine. Boost air can be used in both 2-stroke and
4-stroke cycles to enhance power density. This feature can be
utilized to achieve higher power ratings, or to reduce bore and
stroke. Reducing bore and stroke for a barrel engine can be very
beneficial in reducing piston speeds and resulting accelerations,
and also in reducing reciprocating mass. Both of these topics are
important due to the internal stresses placed on the reciprocating
components and the cam roller interface when high inertial forces
are present.
[0056] The present method of creating boost is unique to a single
ended barrel engine construction. Because the combustion cylinders
are located only on one end of the engine, the ability exists to
utilize the "bottom" end for air compression. Further, this
arrangement maintains the ability to employ variable compression
ratio mechanisms that are simpler and less complicated than might
be used in double-ended barrel engines or on more traditional
slider-crank mechanisms. The use of the "bottom" of the
single-ended piston as an air compressor combines the purposes of a
lower crosshead and compression piston. The availability of boost
air makes it possible to achieve more power at higher altitudes
than otherwise possible. This is particularly important with aerial
vehicles where high service ceilings are desired.
[0057] As discussed above, an engine according to the present
invention may be constructed with multiple cylinders arranged
around the power shaft with the combustion cylinders all located at
one end of the engine. As an alternative, alternating cylinders may
be flipped end-to-end such that the combustion cylinders alternate
end-to-end. Other arrangements may also be possible, such as two
cylinders one direction and then two cylinders the other direction,
or any other arrangement of cylinders. As would be clear to those
skilled in the art, by varying the arrangement, the vibration
and/or power characteristics may be altered. Also, although the
combustion and compression cylinders are illustrated as being
similar in diameter, they may be of slightly or substantially
different diameter. For example, a compression cylinder
significantly larger than the combustion cylinder may be desirable
for high boost applications. The inverse may be beneficial in other
applications.
[0058] As discussed previously, a single-ended barrel engine has
the ability to deviate from the sinusoidal piston motion profile
typical of a crank driven engine. In traditional crank-driven
engines, the piston motion is unavoidably sinusoidal, as
alterations from a sinusoidal shape are not possible due to the
crank configuration. However, a single-ended barrel engine allows a
designer to choose shapes other than a sinusoid. Certain
non-sinusoidal piston motion profiles can provide significant
advantages over a traditional sinusoidal piston motion profile.
[0059] According to one aspect of the present invention, conditions
near firing top dead center are manipulated to optimize or improve
ignition conditions as compared to a traditional slider crank
design. In one embodiment, the conditions are manipulated to enable
homogenous charge compression ignition combustion by crossing the
ignition threshold at a sharper slope or rate, as compared to the
rate that would occur with a traditional slider crank design. This
preferably provides more consistent and robust control of the
ignition point, as shown schematically in FIG. 10. FIG. 10 includes
a curve for the piston motion profile near top dead center in a
standard slider crank engine (labeled "std. piston motion") and a
curve for the piston motion profile according to one embodiment of
the present invention (labeled "higher acceleration motion"). A
horizontal temperature threshold line is also provided, indicating
where homogenous charge compression ignition combustion may occur.
As shown, the present invention provides a profile wherein the
piston crosses the threshold at a faster rate and a steeper curve.
This may be used as a technology-enabler for homogenous charge
compression ignition combustion by providing more consistent and
robust control of the ignition point.
[0060] According to a further aspect of the present invention, the
piston motion profile may include retracting the piston from top
dead center on the firing stroke more quickly than would a
traditional slider crank design. This quicker retraction preferably
reduces the high pressure-rise rates typically experienced in
homogenous charge compression ignition combustion. This same quick
retraction from firing top dead center may also be used to avoid
end-gas detonation in spark-ignited configurations by controlling
the end-gas temperature via expansion of the bulk gas. These are
only two examples of how this tailoring of firing top dead center
motion may be used to control ignition and combustion processes in
an engine.
[0061] By careful tailoring of the piston motion near firing TDC,
trade-offs can be made between a) reducing the heat loss from the
working fluid to the chamber walls and b) moving towards a more
constant volume (instantaneous with respect to volume change)
combustion event. This offers the prospect of improving the thermal
efficiency (i.e. fuel consumption) of the engine.
[0062] According to another aspect of the present invention,
breathing losses in the engine are reduced or minimized by reducing
the piston velocity during the breathing strokes (intake and/or
exhaust) and reducing piston reversal accelerations in these areas,
as compared to a traditional slider crank design. Reducing piston
reversal acceleration increases the time the piston spends near top
dead center or bottom dead center, which gives more time for the
valve to open or close while the piston velocity is minimal.
Reducing piston velocity during the breathing strokes reduces the
displacement rate and therefore the flow velocity required through
the valve and/or port. A lower velocity of air requires less
driving pressure difference through a given valve/port geometry and
will therefore reduce pumping losses in the engine. This method can
also be used to maximize volumetric efficiency.
[0063] According to yet a further aspect of the present invention,
piston motion profiles may be tuned, particularly with respect to
acceleration levels, such that a good balance is obtained between
inertial and pressure force acting on the piston. For example, just
after firing top dead center, when the gas pressure applies a
highly compressive force to the piston upper piston roller 58,
higher downward acceleration of the piston (as compared to a
traditional slider crank design) may be used to provide an equally
high tensile inertial force. The sum of these opposite forces can
be substantially reduced over a range of operating conditions,
thus, reducing Hertzian contact stress at the roller to cam surface
interface. In the same manner, the acceleration level at breathing
top dead center and at both bottom dead centers can be reduced
since there are minimal offsetting pressure forces on the piston in
those regions. In this way, the capabilities of the engine for
maximum cylinder pressure and for maximum speed may be increased
without any actual change to the components other than those
necessary to achieve the desired acceleration levels. Lower piston
acceleration levels (as compared to a traditional slider crank
design) at bottom dead center and breathing top dead center
(between the exhaust and intake strokes) are desired to reduce the
net force on the midportion 56 of the piston 50 and Hertz stress on
the rollers 58 and 60, as well as for improved breathing
efficiency.
[0064] According to the present invention, the clearance between a
piston and the upper end of its combustion chamber at top dead
center (referred to as top dead center clearance) need not be the
same at breathing top dead center (between the exhaust and intake
strokes) and firing top dead center (between the compression and
expansion strokes) events. In one embodiment, top dead center
clearance at firing is set to provide a desired compression ratio,
and top dead center clearance between the breathing strokes is set
greater than the top dead center clearance at firing. In one
example, this allows for greater valve-to-piston clearance during
the valve overlap process (which occurs at or near top dead center
between the exhaust and intake strokes). The increased available
clearance at breathing top dead center may negate the need for
valve pockets in the piston crown, known to be detrimental to both
performance and structural integrity of the piston. Greater valve
lifts may also be used. Also, the piston motion profile may be
designed to dwell the piston near the breathing top dead center for
a longer period of time (as compared to a traditional slider crank
design) or a shorter period of time.
[0065] Use of a breathing top dead center clearance that is greater
than the firing top dead center clearance promotes an increase in
residual fraction, or the portion of the trapped cylinder charge
that consists of burned gas products. Residual fraction is known to
be beneficial in reducing emissions of oxides of nitrogen
(NO.sub.x). Therefore, the unique piston motion as made possible by
the single acting, cam drive barrel engine can be a beneficial
method of reducing harmful exhaust gas emissions. Increased
residual fraction can also offer benefits to homogenous charge
compression ignition combustion by introducing radical species into
the mixture. Residual fraction can also be used in some cases to
alter the ignition point in homogenous charge compression ignition
engines.
[0066] FIG. 9 illustrates one example of a piston motion profile
150 that is non-sinusoidal. The profile includes a downward intake
slope 152, corresponding to piston travel away from the closed end
of the combustion cylinder and expansion of the combustion chamber.
The intake slope ends with a transition through "intake bottom-dead
center" 154. This is followed by an upward compression-slope 156,
which ends with a transition through "compression top-dead center"
158. Under most conditions, combustion occurs at or near
compression top-dead center 158, and the piston travels downward,
as shown by combustion or expansion slope 160. The piston then
transitions through "expansion bottom-dead center" 162 and begins
upward movement, as indicated by the exhaust slope 164. The exhaust
stroke terminates with a transition through "exhaust
top-dead-center" 166, and the intake stroke 152 is repeated.
[0067] The current profile illustrates slower piston motion at
intake breathing top dead center. Slower piston motion at this time
will help improve volumetric efficiency, as discussed above. The
profile also illustrates the piston position at breathing top dead
center lower than piston position at compression/combustion top
dead center. As discussed above, such a profile can be used to
increase valve to piston clearance to allow higher compression
ratio to be used. A slower transition between intake 152 and
compression 156 is also used. This may be provided to maximize the
intake charge and to reduce inertial forces on the piston and upper
roller 58 at bottom dead center. The compression stroke 156 is
illustrated as occurring over a longer period than the combustion
stroke 160.
[0068] In the profile 150, piston motion is faster at and right
after combustion top dead center. Faster piston motion at this time
can be used to improve combustion in homogenous charge compression
ignition or to prevent end-gas detonation in spark-ignited
applications. The combustion stroke 160 is shown as having more
displacement than the compression stroke 156. This is another
advantage to the barrel engine. A longer expansion stroke may be
used to provide a Miller cycle effect to allow more of the
combustion energy to be captured and to allow a longer transition
to exhaust, as shown. In a crank driven engine, the various strokes
are necessarily identical in displacement, thereby limiting
efficiency. The piston motion profile illustrated in FIG. 9 may be
easily manufactured to best suit stoichiometric spark-ignited, lean
combustion spark-ignited, homogeneous charge compression-ignited,
or diesel applications.
[0069] As further embodiments of the present invention, any of the
teachings herein may be combined with any-of the teachings in
copending U.S. patent application Ser. No. 10/021,192, which is
incorporated herein. For example, the present invention may be
practiced with any combustion strategy, including
homogeneous-charged compression ignition, diesel, spark-ignition,
or any others known to those of skill in the art, or discussed in
the incorporated co-pending applications. Likewise, the present
invention may be practiced with four-stroke or two-stroke engine
designs, as well as other less common designs.
[0070] Also, the various aspects of the present invention may be
combined in various ways depending on the application of the
engine. For example, a barrel engine may be provided with a
double-ended, double-roller piston and utilize a variable
compression ratio device and/or integral supercharging and/or
non-sinusoidal piston motion.
[0071] In addition to others known to those of skill in the art,
all embodiments of the present invention may be adapted for the
following combustion strategies: stoichiometric spark-ignited, lean
combustion spark-ignited, homogeneous charge compression-ignited,
diesel, dual-mode lean combustion spark-ignited/stoichiometric
spark-ignited, dual-mode homogeneous charge
compression-ignited/stoichiometric spark-ignited, dual-mode
homogeneous charge compression-ignited/diesel and tri-mode
homogeneous charge compression-ignited/lean combustion
spark-ignited/stoichiometric spark-ignited.
[0072] Those of skill in the art will recognize that the disclosed
embodiments of the present invention may be altered in various ways
without departing from the scope or teaching of the present
invention.
* * * * *