(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)(19) World Intellectual Property Organization
International Bureau

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111(10) International Publication Number(43) International Publication Date

14 October 2010 (14.10.2010)

PCT(51) International Patent Classification:

F02B 3/06 (2006.01)(21) International Application Number:
PCT/US2010/029029(22) International Filing Date:

WO 2010/117713 A1(71) Applicant (for all designated States except US): SCUDERI GROUP, LLC [US/US]; llll Elm Street, Suite 33,
West Springfield, MA 01089 (US).
(72) Inventor: PHILLIPS, Ford; 9303 Strong Box Way, San
Antonio, TX 78254 (US).

(74) Agents: FILDES, Christopher, J. et al.; Fildes & Outland, P.C., 20916 Mack Avenue, Suite 2, Grosse Pointe
EnglishWoods, MI 48236 (US).

29 March 2010 (29.03.2010)(25) Filing Language:(26) Publication Language:(30) Priority Data:
61/167,270
61/169,395
12/722,500

7 April2009 (07.04.2009)15 April2009 (15.04.2009)
II March 2010 (11.03.2010)

English (81) Designated States (unless otherwise indicated, for every
kind of national protection available): AE, AG, AL, AM,
US
AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ,
CA,CH,CL,CN,CO,CR,CU,CZ,DE,DK,DM,DO,
US
US
DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT,
HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP,
KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD,[Continued on next page](54) Title: CRESCENT-SHAPED RECESS IN PISTON OF A SPLIT-CYCLE ENGINE-

FIG. 3

26---

iiiiiiiiiiii-

iiiiiiiiiiii
iiiiiiiiiiii----

iiiiiiiiiiii

33

41

22
40

iiiiiiiiiiii
iiiiiiiiiiii
iiiiiiiiiiii--- 'l""""i<~'l""""ir--r---'l""""i'l""""i.........
~'l""""i
~

f"'l

0
~

I~
I

(57) Abstract: The present invention provides a recess in the
top (or crown) of the expansion piston of a split-cycle engine
for improving the distribution of fuel in the expansion/powercylinder and improving the air/fuel ratios over the spark
plugs.

W 0 2010/11 7713 A 1 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI,
NO, NZ, OM, PE, PG, PH, PL, PT, RO, RS, RU, SC, SD,
SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR,
TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW.

TM), European (AT, BE, BG, CH, CY, CZ, DE, DK, EE,
ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV,
MC, MK, MT, NL, NO, PL, PT, RO, SE, SI, SK, SM,TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW,
ML, MR, NE, SN, TD, TG).

(84) Designated States (unless otherwise indicated, for every
kind of regional protection available): ARIPO (BW, GH, Published:
GM, KE, LR, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, with international search report (Art. 21 (3))
ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ,

wo 2010/117713

PCT/US2010/029029

1

CRESCENT-SHAPED RECESS IN PISTON OF A SPLIT-CYCLE ENGINETECHNICAL FIELD

The present invention generally relates to a recess in
the

top

of

a

piston.

Moreparticularly,

thepresent

invention relates to a crescent-shaped recess in the top of
5

an expansion piston of a split-cycle engine.

BACKGROUND OF THE INVENTION

For purposes of clarity, the term "conventional engine"
as
10

used

in

applicationreferstoaninternal

combustion engine wherein all four strokes of the well known
Otto cycle
strokes)15

the present(the intake,compression,

expansion and exhaustare contained in each piston/cylinder combinationof the engine.

Each stroke requires one half revolution of

the crankshaft(180 degrees crank angle(CA)),and two full

revolutions of the crankshaft(720 degrees CA)

are required

to

cycle

completetheentire

Otto

in

each

cylinderofaconventional engine.
Also, for purposes of clarity, the following definitionis20

offeredapplied

to

for

the

enginesterm"split-cycle

disclosedintheengine"

as

may

be

prior

art

and

as

withinatothereferred to in the present application.
A split-cycle engine comprises:
a crankshaft rotatable about a crankshaft axis;a25

compression

compression
crankshaft

cylinder
such

that

pistonslidablyandoperatively

thecompression

received
connected
pistonreciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft;an expansion (power) piston slidably received within an
30

expansion

cylinderandoperatively

connected

tothewo 2010/117713

PCT/US201 0/029029

2

crankshaft

such

that

the

expansion

pistonreciprocatesthrough an expansion stroke and an exhaust stroke during asingle rotation of the crankshaft; anda crossover passage interconnecting the compression and5expansion

cylinders,thecrossovercompression

expansion(XovrE)crossover(XovrC)valve

passagevalve

defining

including

and

a

a

a

crossoverpressurechamber

therebetween.
United States patent 6,543,225 granted April 8, 2003 to
10

15

Carmelo J.

Scuderi(theScuderi patent)

patent

6,952,923

grantedBranyon

et

(the

al.

extensive

discussion

engines.

In

October

Branyonof

addition

11,

2005

patent)split-cycle
theand United States

Scuderi

to

each
and

and

David

P.

containansimilarBranyontype

patents

disclose details of prior versions of engines of which thepresent invention comprises a further development.

Both theScuderi patent and Branyon patent are incorporated herein byreference in their entirety.
Referring to FIG. 1, a prior art split-cycle engine of
20

the

type

similartothosedescribed

intheBranyonScuderi patents is shown generally by numeral 8.
cycle

engineconventional

8

replaces

engine with atwoadjacent

combination ofcylinder 12 and one expansion cylinder 14.
25

The split-

cylinders
one

and

of

a

compression

A cylinder head

33 is typically disposed over an open end of the expansion
andcompression

cylinders

12,

14

to

cover

and

seal

the

cylinders.
The four strokes of the Otto cycle are "split" over thetwo cylinders 12 and 14 such that the compression cylinder
30

12,

together

with

its

associatedcompression

piston20,

perform the intake and compression strokes and the expansion
cylinder 14,
30,

together with its associated expansion piston

perform the

expansionand exhauststrokes.

The

Otto

wo 2010/117713

PCT/US201 0/029029

3
cycle istherefore completed in these two cylinders 12,

once

crankshaft

perrevolution

16

degrees

(360

CA)

14

about

crankshaft axis 17.
During the intake stroke,
5

compression cylinder 12
inthethrough an intake port

cylinderhead

inwardintocylinder)fluid

communication

theintake air is drawn into the
19 disposedAn

inwardlypoppetintakevalve

18controls

intake

port

19

and

33.

betweentheopening(opening

thecompression cylinder 12.
During10

thecompression

stroke,thecompression piston

20 pressurizes the air charge and drives the air charge intothecrossoverdisposedincompression
15

sourceofpassage

the

port)

cylindercylinder
high

(or

head

which

22,

This

33.

12

and

compression

pressure

gas

to

the

is

typicallymeans
pistoncrossover

that

the

are

20

passagea22,which acts as the intake passage for the expansion cylinder
In some embodiments two or more crossover passages 22

14.

interconnect

thecompression cylinder

12

and theexpansion

cylinder 14.
The20

volumetriccompression

cylinder12ofengineslngeneral)"compression

split-cycleisratio"

ofratio

engineherein

the

8

of

the

compression

(and

for

split-cyclereferred

split-cycletoasengine.

theThevolumetric compression ratio of the expansion cylinder 14 of
25

split-cycle
general)engine(and8is herein referred to as

the split-cycle engine.
acylinderenclosed
30

for

is

well

(or trapped)

recesses)

when

a

in

the "expansion ratio" of

in

the

art

as

the

volume in the cylinder
reciprocating(including all

therein
the

the

is

its

clearance volume)in the cylinder when said piston is

at

top

(TDC)

position.

enclosedat(i.e.,

center

to

of

dead

dead

positionratio

bottomits(BDC)

engines

The volumetric compression ratio ofknown

pistoncentersplit-cycle

volumeSpecificallyforwo 2010/117713

PCT/US201 0/029029

4
split-cycle engines as defined herein, the compression ratioof a compression cylinder is determined when the XovrC valve
isclosed.

Also

specificallyfor

split-cycle

enginesasdefined herein, the expansion ratio of an expansion cylinder
5

is determined when the XovrE valve is closed.
Due to very high compression ratios
to

1,

or

greater),an(e.g.,

outwardly opening

40 to 1,

(opening

80

outwardaway from the cylinder) poppet crossover compression (XovrC)
valve
10

24

control

at

the

flow

from

crossover passage(e.g.,

40 to 1,crossoverthepassagecompression

22.

Due

80 to 1,

to

inlet

25

is

used

to

cylinder

12

into

the

very high expansion

or greater),ratiosan outwardly opening

poppet crossover expansion (XovrE) valve 26 at the outlet 27of the crossover passage 22 controls flow from the crossover
15

passage

22

into

the

expansion

cylinder

14.

As

will

be

discussed in greater detail, the actuation rates and phasingof the XovrC and XovrE valves 24,

20

pressure

inthecrossoverpressure(typically 20

26 are timed to maintainpassage

22

at

a

high

minimumbar absolute or higher during fullload operation) during all four strokes of the Otto cycle.
At

least

one

fuel

injector

2 8 injects

fuel

into

the

pressurized air at the exit end of the crossover passage 22
incorrespondence

occurs
25

with

the

XovrE

valve

26

shortly before expansion piston 30
The air I fueldead center position.

opening,reaches

which

its

top

charge usually entersthe expansion cylinder 14 shortly after expansion piston 30
reaches its top dead center position(TDC),

although it may

begin

under

some

entering

conditions.
30

slightly

beforeTDC

operatingAs piston 30 begins its descent from its top

dead center position,

and while the XovrE valve 26 is still

open, spark plug 32, which includes a spark plug tip 39 that
protrudes into cylinder 14,

is fired to initiate combustionin the region around the spark plug tip 39.

Combustion can

wo 2010/117713

PCT/US201 0/029029

5
be initiated while the expansion piston is between 1 and 30
degrees CA past its top dead center
preferably,

5

(TDC)

position.

combustion can be initiated while the expansion

pistoniscenter(TDC)

between5

and 25

position.

can be initiated while

degrees

CA pastpreferably,its

Still more preferably,

top

dead

combustion

the expansion piston is between 10

and 25 degrees CA past its top dead center
Most

More

combustion

can

be

(TDC)

initiated

position.
while

the

expansion piston is between 10 and 20 degrees CA past its
10

top

dead center

may

be

(TDC)

initiated

position.

through

Additionally,

otherignition

combustion

devices

and/ormethods, such as with glow plugs, microwave ignition devices
or through compression ignition methods.
The
15

XovrE

valve

26

is

but

beforetheresultinginitiatedclosedenter the crossover passage 22.

after

combustion

combustion

event

is
can

The combustion event drives

the expansion piston 30 downward in a power stroke.
During the exhaust stroke exhaust gases are pumped out
of
20

the

expansion

cylinder14disposed in cylinder head 33.
exhaust valve 34,
port 35,

through

25

port

35

An inwardly opening poppet

disposed in the inlet 31 of the exhaust

controls fluid communication between the expansion

cylinder 14 and the exhaust port 35.
andexhausttheexhaustpassage 22.

port

35

are

The exhaust valve 34

separate

from

the

crossoverThat is, exhaust valve 34 and the exhaust port

35 do not make contact with the crossover passage 22.
With
enginelength,30

thesplit-cycle

parameters

12

concept,

bore,

stroke,connecting

rodcompression

ratio,

etc.)

the(i.e.,

volumetriccompression

engineandexpansion

14cylinders

the

are

geometricofgenerally

independent from one another.

For example, the crank throws

36,

cylinder

38

for

the

compression

12

and

expansion

cylinder 14 respectively may have different radii and may bewo 2010/117713

PCT/US201 0/029029

6phased
(TDC)

apart

from

one

another

that

top

dead

centerof the expansion piston 30 occurs prior to TDC of thecompression piston 20.
cycle
5

such

engine8

toThis independence enables the split-

potentiallyachievehigherefficiency

levels and greater torques than typical four stroke engines.
The geometric independence of engine parameters in the
split-cycle engine

10

8 is

also

one of the main

reasons whypressure can be maintained in the crossover passage 22

asdiscussed earlier.

30

reaches

its

Specifically,

top

dead

centertheexpansion piston

position

prior

to

the

compression piston reaching its top dead center position bya discreet phase angle(typically between 10 and 30 crank

angle

phase

degrees).

This

angle,

togetherwithpropertiming of the XovrC valve 24 and the XovrE valve 26, enables
15

thesplit-cycle

engine8tomaintainpressurecrossover passage 22 at a high minimum pressure

in

the

(typically

20 bar absolute or higher during full load operation) during
all four strokes of its pressure/volume cycle.

That is, thesplit-cycle engine 8 is operable to time the XovrC valve 24
20

and the XovrE valve 26 such that the XovrC and XovrE valves
are both open for a substantial period of time (or period of
crankshaft

rotation)

during whichtheexpansion piston

30

descends from its TDC position towards its BDC position andthe25

compression piston

2 0 simultaneously ascends

BDC position towards its TDC position.
time
26(or crankshaft rotation)

are

both

transferred

open,
( 1)

a

crossover passage 22 and
30

to

the

period,from

expansion

During the period of

equal

mass

of

compression cylinder 12(2)cylinderitsthat the crossover valves 24,

substantiallyfrom the

from

gas

is

into

the

from the crossover passage 22
14.

Accordingly,

duringthisthe pressure in the crossover passage is prevented

dropping(typically

20,

below

a

predetermined

minimum

30,

40

bar

duringorabsolutepressure
full

load

wo 2010/117713

PCT/US201 0/029029

7

operation) .
intakeMoreover,andexhaustduring a substantial portion of thestrokes(typicallyintake and exhaust strokes or greater),

90%

of

the

entirethe XovrC valve 24

and XovrE valve 26 are both closed to maintain the mass of5

trapped gas in the crossover passage 22 at a substantiallyconstant level.

As a result,the pressure in the crossover

passage 22 is maintained at a predetermined minimum pressureduringallfourstrokesoftheengine'spressure/volume

cycle.
10

For purposes herein, the method of opening the XovrC 24
and

XovrE

26

descending

valves

from

while

TDC

and

the

the

expansion

piston30

iscompression

piston20

isascending toward TDC in order to simultaneously transfer a
substantially
15

equal

mass

of

gas

into

and

out

of

the

crossover passage 22 is referred to herein as the Push-Pullmethod of gas
enablesthetransfer.

pressure

in

It

is

the

Push-Pull method thatthecrossoverpassage

22

of

the

split-cycle engine 8 to be maintained at typically 20 bar or
higher during all
20

four

strokes of the engine's cycle whenthe engine is operating at full load.
As discussed earlier,the exhaust valve 34 is disposedln the exhaust port 35 of the cylinder head 33 separate fromthe crossover passage 22.

The structural arrangement of theexhaust valve 34 not being disposed in the crossover passage
25

22, and therefore the exhaust port 35 not sharing any common
portion with the crossover passage 22, is preferred in orderto maintain the trapped mass of gas in the crossover passage
22

duringtheexhauststroke.

Accordingly

large

cyclicdrops in pressure are prevented which may force the pressure
30

in

the

crossoverpassage

below

the

predetermined minimumpressure.
The high compression ratio within compression cylinder
12 and the high expansion ratio within expansion cylinder 14

wo 2010/117713

PCT/US201 0/029029

8
areachieved using,piston20

andrespectively.
the tops
5

inter

a

That

is,

towardflat surfaces.

theflat-topped

compression

expansion

pistonin prior art(or top surfaces)

face

a

flat-topped

and expansion piston 30
that

alia,

30,

split-cycle engines,of each of compression piston 20(i.e.,

the generally circular sides

cylinder

head

33)

are

substantially

Cylinder head 33 also typically has a flatbottom surface (i.e., a surface of the cylinder head 33 that
faces
10

towardthetopsurfacesofthecompression

andexpansion pistons)

facing toward each of the compression 12

andcylinders,

expansion

14

so

that

the

volumecylinders is minimized when the pistons 20,

in

these

30 are at theirrespective top dead center (TDC) positions.
XovrE
15

piston

30

valve

26

opens

shortly

beforethereaches

its

top dead center position.

expansionAt

thistime the pressure ratio of the pressure in crossover passage
22 to the pressure in expansion cylinder 14 is high, due tothe fact that the minimum pressure in the crossover passage
is typically 20 bar absolute or higher and the pressure in20

theexpansion

cylinderduringtheexhausttypically about one to two bar absolute.

strokeis

In other words,

when XovrE valve 26 opens, the pressure in crossover passage
22

issubstantially higher than the pressure

cylinder 14
25

This

high

and/orin expansion(typically in the order of 20 to 1 or greater).
pressurefuelhigh speeds.

chargeratio
tocausesflow

intoinitialflow

expansionofthecylinder

14

air
at

These high flow speeds can reach the speed ofsound, which is referred to as sonic flow.

This sonic flow

is particularly advantageous to split-cycle engine 8 because30

it causes a rapid combustion event, which enables the splitcycle engine

8 to maintain high combustion pressures eventhough ignition is initiated while the expansion piston 30
is descending from its top dead center position.

wo 2010/117713

PCT/US201 0/029029

9

However,high speed(and particularly sonic)

expansion cylinder 14 creates a pressure wave,
theair/fuel

piston 30.
5and/orchargeacrossthetopflow into

which moves

surfaceof

expansion

The pressure wave can cause a peak in pressure

temperaturecylinder 14.

at

or

near

the

walls

of

expansion

This peak in pressure and/or temperature canhave adverse effects such as causing early detonation of the
air I fuelchargeignition)
10

the

wave

valve

peaks

near

exhaustone

expansion

cylinder14.

Accordingly,

guide

air/fuel

chargean(i.e.,

pre-

of

the

carriedsuch that

valve

34

hottest
there

by

a

becausesurfaces
is

in

a

need

to

pressurewave

in

any peak in pressure and/or

temperature does not cause pre-ignition.

when

25

ignition

has

Referring

20

spark

34

split-cycle engines
15

to

The risk of pre-ignition can be aggravated if

pressure

exhaust

prior

the

to

FIG.

expansionatillustrated.

XovrE

valve

valve

head

head
stem

the position

pistonapproximately

shaped

2,

its

of

top

valve

40
41

30

from

split-cycle

dead
26

extends

centerincludeswhichof XovrEaaengine8

26
ispositionisgenerally

disc

generallyoutwardly.

valve

cylindricalWhenpiston30

reaches its TDC position,

the head 40 of XovrE valve 26 iselevated above its closed(or seated)

position in cylinder

head 33.

Curtain areas 42 and 44 are local minimum cross-sectional

areas

words,

through

which

fluid

can

flow.

In

other

the curtain areas 42 and 44 are the most potentiallyrestrictive

areas

to

the

flow

of

air/fuel

betweenthecrossover passage 22 and the expansion cylinder 14 when the
expansion
30

piston

30

is

at

or

near

its

top

dead

centerposition.
The air I fuelcharge flowing from crossover passage 22

into expansion cylinder

14 must passthrough curtain area

42, which is in the shape of a truncated cone (hereinafter a

wo 2010/117713

PCT/US201 0/029029

10"truncatedconical"shape)

betweenvalve 26 and cylinder head 33.

the

head

40

of

XovrE

Much of the air/fuel charge

flowing from crossover passage 22 into expansion cylinder 14
must also pass through cylindrically shaped curtain area 44
5betweenthe expansion piston30

and thecylinder head 33.

The region between truncated conical curtain area 42 and theoutlet 27 of the crossover passage 22 is known as the valve
pocket 4 6 of XovrE valve 2 6.
pocket10

46

valve 26,

istheregionMore specifically,bounded bycylinder head 33,

the

head

the valve

40

of

XovrE

truncated conical curtain area

42, and the outlet 27 of the crossover passage 22.
When the expansion piston 30 is at or near its top dead15

center position the expansion piston clearance 48(i.e.,

clearance

expansion

depth

betweentop

surface50

piston 30 and the bottom surface(or firedeck)cylinder head 33,

the

0.6 millimeters, or less).
opens

away from its

lift

of

clearance

XovrE
48

XorvE valve(e.g.,

1.0, 0.9,

sea ted position is

valve

2 6.

Notably,

can be comparable
2 6 lift.

to,This means

truncated conical curtain area 42.

30

curtain area

44

reduction

flow.

in

of the

can

cause
In

0.8,

0.7,

or

The distance that XovrE valve 26

aknown as

the

that

pistonthan,cylindricalthecurtainor even smaller than,

Such a small cylindricalsubstantial pressureotherthe valve

expansionor even lessarea 44 can be comparable in area to,25

52

which faces the interior of the expansion

cylinder 14) can be very small

20

of

the

words,

when

the

drop

and

cylindricalcurtain area 44

is comparable in area to truncated conicalcurtain area 42,

the cylindrical curtain area 44 can preventanappropriate

theexpansion

constraints.
theamountofcylinderanair/fuel
14

chargewithinfrom entering

appropriate

timeThis situation is particularly pronounced whencylindricalcurtain

area

44

is

truncated conical curtain area 42 because,

smallerthan

thein this case,thewo 2010/117713

PCT/US201 0/029029

11cylindrical curtain area 44 is the most restrictive area in
the flow of air/fuel from the crossover passage 22 into the
expansion cylinder 14 when the expansion piston 30 is at ornear top dead center.
5

The above mentioned pressure drop and/ or reduction in
flow

are

in

that

efficiency.

Accordingly,

there

size

curtain44

ofpiston10

problematictheand the

area

they

can

reduceengineis a need to increase theformed between

cylinder head ofatheexpansion

split-cycle engine,solong as the increase in efficiency from doing so is greater
than

the

loss

of

efficiency

causedbytheresultingdecreased expansion ratio in the expansion cylinder.
XovrE valve
transfer15

the

26 must achieve

air/fuel

chargecrankshaft 16 rotation
60

degrees CA)

sufficient

in

a

very

lift to

short

fully

periodof(generally in a range of about 30 torelativeto that of a conventional engine,which normally actuates the valves within 180 to 220 degrees
CA.
to
20

This means that XovrE valve 26 must actuate about four
six

times

engine.

fasterthan

thevalvesofaconventional

Fuel is injected into the exit end of the crossover

passage 22 in synchronization with the timing of XovrE valve
26 actuation.

Spark plug 32 is fired to initiate combustion

shortly thereafter
after
25

top

dead

(preferably between 1 tocenteroftheexpansion

30 degrees

piston

30,

CA

more

preferably between 5 to 25 degrees CA after top dead centerof the expansion piston 30, most preferably between 10 to 20
degrees

CA after

top

dead center

of

the

expansion piston

aforementioned constraints,

air/fuel mixing

3 0) .

Given
30

the

and distribution throughout expansion cylinder 14 must take
place

in

a

rotation)
cylinder

very

short

period

of

time

(or

crankshaft

Proper distribution of fuel throughout expansion
14

andoptimalair/fuelratiosoverthespark-

wo 2010/117713

PCT/US201 0/029029

12

plug ( s)32 should resultin improved ignition and more of

the available fuel being burned.

Accordingly,

there

is a

need to guide fuel distribution in a split-cycle engine to
distribute the fuel5cylinderandappropriately throughout

improvetheair/fuelratiosthe expansion

over

the

spark

plugs.

SUMMARY OF THE INVENTION

The
10

present

aforementioned

invention

problems

providesofsolutiona

guidingtopressure

a

the
wave,

increasing the size of a curtain area between the expansion
piston and the cylinder head,in split-cycle engines.

and guiding fuel distribution

In particular the present invention

solves these problems by providing a recess15

in the top of

the expansion piston of a split-cycle engine.
These

and

other

advantages

areaccomplishedinanexemplary embodiment of the present invention by providing
an engine (10), comprising:a20

crankshaft(16)

rotatable

about

a

crankshaft

axis

(17);

an expansion cylinder( 14)

including a centerline axis

( 62) ;

an expansion piston

25

expansion

cylindercrankshaft

(16)

(14)

such

(30)

slidably received within theandoperatively

that

the

connected

tothepiston(30)

isexpansion

operable to reciprocate through an expansion stroke and an
exhauststroke during asingle rotation of the

crankshaft(16), the expansion piston (30) including a top surface (50)
and an outer perimeter (74);30acylinder

head

(33)

cylinder

(14)

such

that

cylinder

head

(33)

faces

expansion piston

(30),

the

a

disposedoverbottomsurface

(52)

of

the

surface

(50)

of

the

the

top

cylinder head

the

(33)

expansion

including a

wo 2010/117713

PCT/US201 0/029029

13crossover passage outlet(27)

disposed

therein,theexhaustcrossoverpassageoutletexpansion cylindera5

anvalve)

inlet

(53)

and

the

each

being

proximatethe(12/20)(22)

sourcehighconnectingato the expansion cylinder

of

(14)

via the(27);

outwardly opening crossover expansion valve(XovrE

(26)

(27),

disposed in the crossover passage outlet

the XovrE valve(26)

operable to allow fluid communication

betweenthecylinder(14) during a portion of the expansion stroke;

an
inlet
15

port

(14);

crossover passage outlet

10

(27)

crossover passage

pressure gas(53)

and an exhaust port inlet

crossoverexhaust

(53),

valve

passage

(34)

(22)

disposed

the exhaust valve

(34)

and

in

the

the

expansion

exhaustport

operable to allow fluid

communication to or from the expansion cylinder(14)

via theexhaustoftheexhaustdisposed in the top surface(50)of the

port

inlet

(31)

duringaportionstroke;a recess

(60)

(30),

expansion piston
20

surfacedistance,

expansion

piston

along

line

the

top

a

the

( 60)

clearance

parallelsurfaceand the bottom surface
25

recessincludingabottom( 64) ;

anbetweenthe

expansion piston

(50)
(52)

(30)

of

( 8 0)

being

atshortest

thecenterline

theexpansion pistonof the cylinder head
is

a

its

axis

( 62),
(30)

(33)

when

top dead center(TDC)

position;a recess depthline parallel thesurface
30

(64)

(82)

being a shortest distance,

centerline axisof the recess

the expansion piston(60)( 62),

along abetween the bottom

and the top surface

(50)

of

(30);

wherein a portion of the recessof the crossover passage outlet

(27);

(60)

overlaps a portion

wo 2010/117713

PCT/US201 0/029029

14

wherein a portion the exhaust port inlet (31) does notoverlap any portion of the recess (60); andwherein the recess

depth

( 82)

is between 1. 0 and 3. 0times the expansion piston clearance (80).
The expansion ratio may be at least 20 to 1, preferably

5

at least 30 to 1, and more preferably at least 40 to 1.
engineinmay be operable to initiate a combustion eventthe expansion cylinder

(30)
10

(10)

is

descending

position,

from

( 14)

its

position,

TDC position

its

BDC

(30)

TDC

position.

No

portionof

theexhaustrecess(60)

mayoverlapany

portionPortionsof

theignitiondevice(32).

(16) past the expansion piston's

(32),

of

preferably

The recess depth

therecess
port

at

at

two

least

(60)

inlet

overlap

may
(31).

least

one

ignition(82) may be between 2.0 and

3.0 times the expansion piston clearance
20

towards

and more preferably between 10 and 20 degrees ofTDC

devices

the expansion piston(16) past the expansion piston'srotation of the crankshaft

15

while

preferably between 10 and 25 degrees of rotationof the crankshaft

(30)

The

(80).

20% or lessof the total area of the exhaust port inlet (31), preferably
10% or less, may overlap the recess (60).
anotherIn

exemplaryembodiment

of

the

present

invention, an engine (10) comprises:a25

crankshaft(16)

rotatable

about

a

crankshaft

axis

(17);

an expansion cylinder( 14)

including a centerline axis

( 62) ;
an expansion piston

30

expansion

cylindercrankshaft

(16)

(14)

such

(30)

slidably received within theandoperatively

that

the

expansionconnected

tothepiston(30)

is

operable to reciprocate through an expansion stroke and an
exhauststroke during asingle rotation of the

crankshaft

wo 2010/117713

PCT/US201 0/029029

15
(16),

the expansion piston

and an outer perimeter(74);

cylinder

( 33)

a

5

head

cylinder

( 14)

such

that

cylinder

head

( 33)

faces

expansion piston

10

(30)

a

over

bottomsurface

(52)

of

the

surface

(50)

of

the

(27)

disposed

therein,theexhaustcrossoverpassageoutleta(12/20)includingand an exhaust port inlet

(27)

a

(53)

port

inlet

(53)

and

the

each

being

proximate

the

(22)

sourcehighconnectingato the expansion cylinder

crossover passage outlet

of

(14)

via the(26)

disposed(27);

a crossover expansion valve
15

expansion(14);

crossover passage

pressure gas( 33)cylinder headcrossover passage outlet

expansion cylinder

top

the

(50)

disposedthethe( 3 0) 'including a top surface

in the crossover passage outlet(XovrE valve)(27),

the XovrE valve(26)

operable to allow fluid communication between the crossover
passage

(22)

and

the

expansion

cylinder(14)duringaportion of the expansion stroke;
an
20

inlet

exhaust

(53),

valve

(34)

disposed

the exhaust valve

(34)

in

the

exhaustport

operable to allow fluid

communication to or from the expansion cylinder(14)

via theexhaustoftheexhaustdisposed in the top surface(50)of the

port

inlet

(31)

duringaportionstroke;a recess
25

expansion piston
surfacedistance,
between

(30),

the

expansion

piston

along

line

the

top

a

(60)

expansion piston

position;clearance

parallelsurfaceand the bottom surface
therecessincludingabottom

(64);

an

30

(60)

(50)
(52)

(30)

of

( 8 0)

being

atshortest

thecenterline

theexpansion pistonof the cylinder head
is

a

its

axis

( 62),
(30)

(33)

when

top dead center(TDC)wo 2010/117713

PCT/US201 0/029029

16

a recess depth(82)

being a shortest distance,line parallel the centerline axis
surface(64)of the recess(60)( 62),

along abetween the bottom

and the top surface

(50)

of

the expansion piston (30);an5expansion

ratio

being

the

ratio

of

the

enclosed

volume in the expansion cylinder when the expansion piston
is at its bottom dead center(BDC) position to the enclosed

volume in the expansion cylinder when the expansion piston
is at its TDC position;
10

wherein the expansion ratio is at least 20 to 1; and( 82)

wherein the recess depth

is greater than or equal

to the expansion piston clearance ( 8 0) .
( 60)

may overlap a portion of

the crossover passage outlet ( 2 7) 'and a portion the exhaustA

15

portion of the recess

port inlet(31)

may not overlap any portion of the recess( 60) .

The

recesstimes,

preferably between 2. 0 and 3. 0 times,

piston clearance

depth

(80).

( 82)

may be between

3. 0

the expansion

The expansion ratio may be at least

30 to 1, preferably at least 40 to 1.
20

1. 0 andThe engine

(10)

may

be operable to initiate a combustion event in the expansion
cylinder(14)

while the expansion piston(30)

is descending

from its TDC position towards its BDC position,

preferably

between 10 and 20 degrees of rotation of the crankshaft (16)past the expansion piston's
25of the recess( 60)

port inlet (31).
least

one

TDC position.

No portion

may overlap any portion of the exhaust

Portions of the recess

ignition

ignition devices(30)

device

(32).

(32),

(60) may overlap at

preferably

at

least

two

20% or less of the total area of theexhaust port inlet (31), preferably 10% or less, may overlap
30

the recess (60).
These

and

will be moreotheradvantages

of

the

fully understood from thepresent

invention

following detailed

wo 2010/117713

PCT/US201 0/029029

17

description

of

the

invention

taken

together

with

the

accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
5

FIG.

1

is

a

cross-sectional

view

of

an

exemplarythecrossoverembodiment of a prior art split-cycle engine;
FIG.

2

is

expansion valve

a

cross

(XovrE)

sectionalof FIG.

viewof

1 when the expansion piston

is at its top dead center (TDC) position;
10

FIG.

3 is a perspective partially cut-away view of the

expansion cylinder of a split-cycle engine according to thepresent invention;
FIG.
the
15

that

4 is an orthographic projection of components ofsplit-cycle
isengineof

FIG.

perpendicular

to

the

3

onto

a

projection

centerline

axis

plane

of

the

expansion cylinder of the split-cycle engine; andFIG.

5 is a side view of the expansion cylinder of the

split-cycle engine of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

20
FIGS.
projections

3,

4,

and

5

illustrateofanexemplaryembodimentvarious
of

a

views

or

split-cycle

engine 10 in accordance with the present invention.

Split-

cycle engine 10 is similar to prior art split-cycle engine 825

as illustrated and described in FIGS. 1 and 2.

Accordingly,

for purpose of comparison between split-cycle engines 8 and
10, like reference numbers represent like components.
The

exemplaryinnovative recess
30

split-cycle

engine10

includesan

60 disposed in the top surface 50 of the

expansion

piston30

inaccordance

with

the

present

invention.

As will be discussed in greater detail herein,

recess 60 enhances flow from the crossover passage(s)22 tothe expansion cylinder 14 by relieving the flow restriction

wo 2010/117713

PCT/US201 0/029029

18

therebetween.

Moreoverrecess60

guidestheair/fuel

mixture in the general direction of the spark plug ( s)32,

and substantially directs flow of the air/fuel mixture awayfrom the exhaust valve 34 and away from the cylinder walls
5

of

the

expansion

cylinder14.

increases

cylindricalcurtainexpansion

pistonand30

Additionally,
area

the

44

formedcylinderhead

decreasing the expansion ratio enough totherecess60

betweenthe33

without

outweigh thebenefits of the resulting enhanced flow.
10

FIG. 3 is a perspective partially cut-away view of the
expansion cylinder of the exemplary split-cycle engine 10.
Split-cycle engine

10

includestwocrossover passages

22.

Each of the two crossover passages 22 include a XovrC valve
24
15

of

the

type

seen

in

FIG.

1

that

controls

communication between the compression cylinder 12in FIG. 1)

fluid(best seen

and the crossover passage 22 through a crossover

passage inlet 25(best

seen in FIG.

1)

Each of the twocrossover passages 22 further include a XovrE valve 26 that
controls
20

fluid communication between the crossover passage

22 and the expansion cylinder 14 through a crossover passage
outlet 27.

The

two XovrE valves

26 each include a valve

head 40 and a valve stem 41.
The25

split-cycle engine

10

ignitiondevicescase,disposedinthedevices32

includeportionof each(in

thiscylinder headaninitiate the combustion process.
30

33.

Each

32

and produces

includesa pair of

spark-plugs)

ignition device

ignition device

expansion cylinder 14

further

of

tip

that

32,

the

39,

each

ignition

which isextends

into

a

the

the energy required toMore specifically, in thiscase,the spark plug tip 39 typically includes one or more

side

(or

ground)electrodes.

Thespark-plug

typically further includes a central electrode 43
in FIG. 4)

designed to eject electrons(a cathode)

tip

39

(best seenin orderwo 2010/117713

PCT/US201 0/029029

19

to initiate a combustion event.

Alternative embodiments canutilize ignition methods or devices other than spark-plugs
32.

For example,

plugs,
S

microwave

alternative embodiments can utilize glowignition

devices,

compression

ignition

methods for diesel combustion (wherein no ignition device isrequired), or any other suitable ignition method or device.
Cylinder head 33 includes a single exhaust port 3S withan exhaust valve 34 disposed in an inlet 31 of the single
exhaust port 3S.

10

The generally crescent shaped recess 60 is

disposed in the top surface SO of the expansion piston 30.
The centerline axis 62 of the expansion cylinder 14 extends
vertically through the center of the expansion cylinder 14
and is the line of action through which expansion piston 30
reciprocates.

1S

FIG.

4 is an orthographic projection of components ofthe split-cycle engine 10 onto any projection plane that isperpendicular

to

the

centerline

axis

62

of

the

expansion

cylinder 14.

In the exemplary embodiment such a projection

plane is parallel to or substantially parallel to the top
20

surface SO of the expansion piston 30.
Recess 60 includes a bottom surface 64, which generally
lies along a plane perpendicular to the centerline axis 62.
Recess 60 includes a vertically extending wall 68
in FIG. S).

2S(best seen

Recess 60 includes a curved transition 66 (bestseen in FIG. S)

integrally connecting the bottom surface 64

and the vertically extending wall 68.

Vertically extending

wall 68 includes a concave edge portion 70 and a convex edge
portion 72.
Top surface SO is typically flat and lies along a plane30

substantially perpendicular to the centerline axis 62 of the
expansion cylinder 14.
circularouter

Top surface SO includes a generally

perimeter

74.

Top

surfaceSOfurther

includes a boundary region 76 disposed between (1) the outerwo 2010/117713

PCT/US201 0/029029

20
perimeter 74 of the top surface 50 and(2)

the convex edge

portion 72 of the wall 68 of the recess 60.
For purposes herein,

5

outlet,passage,portion,transition,

like,

10

a first component,

surface,perimeter,wall, valve,(or a portion thereof)e.g.,recess,boundary region,

spark plug,

piston or theand a second component

portion thereof)"overlap" when the first component

portion thereof)

and thethereof)

the

share

second component

same

coordinates

aforementioned projection planes.
details components

It

(or a
(or the(or the portiononfollows(or portions thereof)

edge

any

of

the

that

FIG.

4

of the split-cycle

engine 10 which overlap each other.
Portionsofcrossovercrossover passage 22
15

particularly,
each

of

27

of

each

overlap portions of recess

60.

More

portions

bottomofsurface

Portionsofoutlets

overlap

portionsofoutlets64,

27

passageoutlet27

overlaptransition

66,

portions
and

wall

68.

22

also

of each crossover passage

top

surface

50.

More

of

particularly,

portions of each outlet 27 overlap portions of the boundary
20

region 76 of top surface 50.
Inlet 31 of exhaust port 35 overlaps a portion of top
surface 50 of expansion piston 30.
the

inlet

31

overlapsany

portionHowever,no portion of

of

60.

recessInalternative embodiments, some small amount of overlap may be
25

allowed between a portion of the recess 60 and a portion of
the inlet 31.

For example, 25%, 20%,

15%, 10%, or less, ofthe total area of the inlet 31 of exhaust port 35,
allowedtoalternative
30

would

overlaptheembodiment,

appreciatetherecess60.

oneordinaryofdesirability

However,skill(e.g.,

may be

in

such

an

in

the

art

avoiding

pre-ignition)of preventing the hottest portions of the exhaust

valve

disposed

35

in

inlet

31

(typicallythecenterofwo 2010/117713

PCT/US201 0/029029

21

exhaust valve

35

and/or thecenter of the

inlet

31)

from

overlapping any portion of the recess 60.
At least a portion of each ignition device 32 overlaps
portions
5ofrecess60.

More preferably,

theentirety ofeach of the ignition device tips 39 overlap the recess 60.
Specifically,

in

this

case,

the

entiretyofspark-plug tips 39 overlap the recess 60.

each

10

recess60.

ignition methods

theMore preferably,

the entirety of each of the central electrodes
theof

43 overlap

Inalternative

embodiments

thatutilizeorandevicethanspark-

ignitionotherplugs, one of ordinary skill in the art would appreciate thedesirability of providing overlap between a portion of therecess 60 and the area where combustion is initiated.
Referring15

cylinder 14

to

FIG.

and some

5,

a

side

of

surrounding components

the two crossover passages 22)

20

view

the

expansion(e.g.,

one ofis shown when the expansion

piston 30

is at

its top dead center

expansion

pistonclearance

distance(measured along a line parallel to the centerline

axis

of

62

the

expansion

80

is

(TDC)

the

cylinderposition.

shortest

14)

The

clearance

betweenthetop

surface 50 of the expansion piston 30 and the bottom surface(or fire deck)

52 of the cylinder head 33 when the expansion

piston

its

is

at

TDC

position.

The

expansion

pistonclearance 80 in the exemplary embodiment is preferably very
25

small (e.g., 1.0, 0.9, 0.8, 0.7, 0.6 millimeters or less).
The recess depth 82 is the shortest distance
along

a

line

paralleltothecenterline

axis(measured
62

of

the

expansion cylinder 14) between the bottom surface 64 of therecess 60 and the top surface 50 of the expansion piston 30.
30

In order to increase the size of cylindrical curtain area 44
and significantly reduce

the

flow

restriction between

crossover passage 22 and expansion cylinder 14,

thethe recess

depth 82 is preferably designed to be equal to or greaterwo 2010/117713

PCT/US201 0/029029

22

than one half times
8 0.

More

(0. 5x)preferably thethe expansion piston clearance
recessdepth

82

greater than one time (1.0x), two times
half
5

times

(2.5x),

or

piston clearance 80.

three

times

is

equal

to

or

(2.0x), two and one(3.0x)

theexpansion

However it is important to note thatthe recess depth 82 must be kept small enough such that any
increaseinefficiency

providedbyincreasing

therecessdepth 82 is greater than the loss of efficiency caused bythe10

resulting decreased expansion

recessdepth

82shouldberatio.

small

enoughPreferably,

the

to

an

provideexpansion ratio of 20 to 1 or greater, more preferably 30 to
1 or greater, and most preferably 40 to 1 or greater.
The combination of having a recess depth 82 that is one
or more times the piston clearance 80 while maintaining an
15

expansion

ratio

of

at

least

20

to

1

or

greaterisonlypossible if the expansion ratio would have been very large
if recess 60 was not disposed in the piston 30,
1,

8 0 to 1,

difficult20

toor greater.
achieve

e.g.

40 to

These large expansion ratios areinaconventional

engine,becauseasubstantial clearance volume must be maintained in order toproperly initiate combustion before a conventional engine's
pistonreaches

TDC.

However,thesplit-cycle

utilizes the Push-Pull method of gas transfer
earlier herein)
25

10(as describedto enable combustion to initiate after the

expansion piston reaches TDC.
large

engineclearance

volumeinAccordingly,

expansion

the need for acylinder

14

is

not

required in split-cycle engine 10 and expansion ratios of 20
to 1,

4 0 to 1,

or greater can therefore be achieved,

evenwith the recess 60 depth is disposed in piston 30.
30

The curved transition 66 and the vertically extending
wall

68

of theAdditionally,
portionsofrecess
the

the

60

are best

previously

outlet27

andshown here

described
variousin FIG.

overlapother5.

betweensplit-cycle

wo 2010/117713

PCT/US201 0/029029

23

engine10components

greater detail.

can

be

seen

in

this

side

view

in

A portion of the boundary region 76 of the

top surface 50 is shown overlapping a portion of outlet 27

5of thecrossover passage 22.

betweenboundary

region76

Advantageously,
andoutlet27

theoverlap

createsaflow

restriction when expansion piston 30 is at or near TDC that
tends

to

direct

flow

away

from

the

walls

cylinder 14 and toward spark plugs 32.

10

Also,

the bottom surface 64,

curved transition 66,

extending wall

the

68

of

recess

60

of

are

expansion

portions ofand verticallyshownoverlapping

portions of outlet 27of the crossover passage.

Notably,theportions

passageoverlap

outlets

between27

and portions

of

of

the

the

crossoverrecess

60

are

shown

here

increasing the size of the cylindrical curtain area 44
15enhance flow into recess 60 and toward spark plugs 32.
During engine operation,
beforetop

dead center(e.g.,

5-20

degreesExhaust
20

valve

34

XovrE valves 26 open shortly(BTDC)

BTDC

of

of

closesthethe

expansion piston

expansion

concurrently,

piston

very

30

30).

slightly

thereafter or shortly before the XovrE valves 26 open (e.g.,
5-45 degrees BTDC of the expansion piston 30)
that the pressure of any gases

25

toIt follows

remaining ln the expansion

cylinder 14

immediately after the exhaust valve

near

substantially

TDC

is

less

than

the

34

pressureclosesoftheair/fuel in the two crossover passages 22.
The air/fuel charge entering the expansion cylinder 14
through the crossover passage outlets 27
expansion piston 30)(near TDC of thefollows the path of least resistance.

The path of least resistance here is into the recess 60 and
30

towards the spark-plugs

32.

crossover passage outlets

27

This is the case because theoverlap both

( 1)

portionsofthe boundary region 76 of top surface 50 and (2) portions oftherecess60.

Accordingly,

the

area

of

overlap

betweenwo 2010/117713

PCT/US201 0/029029

24

recess 60 and outlet 27 provides the least restrictive flow
path toinitially direct

the

flow

of

the

air/fuel

chargeinto the recess 60 and towards the spark-plugs 32 when thepiston 30 is near its top dead center position.
5

No portion of the recess 60 extends to any portion ofthecylinderwalls

Additionally,

no

of

the

portionof

expansion

therecesscylinder14.

overlapsany

60

portion of the inlet 31 of the exhaust port 35. As a result,flow is substantially restricted from traveling toward the10

areas near the cylinder walls and exhaust valve inlets,
air I fuel

the

is

substantially

areas

when

accumulating

in

these

near

It

is

TDC.

air/fuel
15

chargechargeimportant

from

to

the

prevented

frompistonissubstantially prevent

theaccumulating

expansion

and

near

the

walls

of

the

cylinder 14 because such a situation can cause the air/fuelcharge to take too long to ignite,engine efficiency.

which is detrimental to

It is important to substantially preventthe air/fuel charge from accumulating near the inlet 31 of
the exhaust port because the exhaust valve 35 is disposed
20

therein.

The exhaust valve 35

one of the hottest
which

means

that

(particularly its center)issurfaces in the expansion cylinder 14,
air/fuel

accumulation

near

the

exhaustvalve 35 aggravates the risk of pre-ignition.
For purposes herein,
25

ratio

combustion.

Also"stoichiometric"(often abbreviated "stoich")theor air-fuel(AFR), is the mass ratio of air to fuel present during

the AFR wherein there30

the air/fuel mixture,

air)

for

for

is

conversion

oxidized

products

gasoline

fuel,purposesjust enough oxygenofduring

all

the

fuel

combustion.

the AFR of about

stoichiometric ratio.

herein

14.7

to

the

term

is defined as(contained inintocompletely

Typically,for

1 represents

theA rich AFR is when there is more fuelwo 2010/117713

PCT/US201 0/029029

25
than required for

stoich and alean AFR iswhen thereismore air than required for stoich.
Lambda

is

(A)

an

alternative

way

to

represent

AFR,

wherein the AFR is normalized to the stoichiometric ratio of5

thespecific

fuel.

A lambda

lambda of greater than 1,
lambda

of

less

than

1

of

1 represents

stoich.

A

represents a lean mixture and a

represents

rich

a

mixture.

For

example, if stoich is 14.7 to 1, than:

10

1)

A

1 represents the stoich AFR of 14.70 to 1;

2)

A. 8 represents a rich AFR of 11.76 to 1; and3)A

1.3 represents a lean AFR of 19.11 to 1.

The air/fuel mixture is generally guided by the geometry of15

the recess60

and distributes throughout the recess

stratified

form

distributionisstoichiometric)
spark-plugs
air I fuelmixture,withintotoignition.

provideair/fuel(ignition

mixturesplugs 32.
20

prior

a

in regions

in

32

the

and

further

preferably the

of

0. 6

lambda

the

(or

near

of

the

successively

leaneraway from thespark-

it is preferable that the air I fuelAccordingly,

range

in

of

vicinity

which surrounds the spark plugs 32,
agoal

stoichiometricmixturedevices)

The

60

to

1. 3

prior

to

should be within ahave a lambda

ignition.
range

More

of

0. 7 to1.2, and most preferably the lambda should be within a rangeof 0. 8 to 1. 1.
25

When

the

stoichiometricspark-plugs
(or

near

32

are

stoichiometric)

burns rapidly and acts as a catalyst
ignitetheleanermixtures.

The

activated,
air/fuel

mixture(i.e., pilot flame)
spark-plugs

the

32

to
are

preferably activated between 1 and 30 degrees CA past TDC of30

the expansion piston 30,
degrees

CA past

TDC ofmore preferably between 5 and 25
the expansion piston 30,

and most

wo 2010/117713

PCT/US201 0/029029

26
preferably between

10

and

2 0 degrees

CA past

TDC

of

the

expansion piston 30.
While
herein,5variousembodiments

are

shown

and

described

various modifications and substitutions may be madethereto without departing from the spirit and scope of theinvention.

Accordingly,

it

is

to be

understood thatthepresent invention has been described by way of illustrationand not limitation.

wo 2010/117713

PCT/US201 0/029029

27

CLAIMS

What is claimed is:1.

An engine (10), comprising:a5

crankshaft(16)

rotatable

about

a

crankshaft

axis( 17) ;
an expansion cylinder( 14)

including a centerline axis

( 62) ;
an expansion piston
10

expansion

cylindercrankshaft

(16)

(14)

such

(30)

slidably received within theandoperatively

that

the

connected

tothepiston(30)

isexpansion

operable to reciprocate through an expansion stroke and an
exhauststroke during asingle rotation of the

crankshaft(16), the expansion piston (30) including a top surface (50)15

and an outer perimeter (74);cylinderaheadcylinder

( 14)

such

that

cylinder

head

( 33)

faces

expansion piston
20

( 33)

( 3 0) 'adisposedoverbottomsurface

(52)

of

the

surface

(50)

of

the

the

the

top

cylinder head

the

( 33)

expansion

including acrossover passage outlet(27) and an exhaust port inlet (53)disposed

therein,theexhaustcrossoverpassageoutlet

(27)

port

inlet

(53)

and

the

each

being

proximatetheexpansion cylinder (14);a25crossover passage

pressure gas(12/20)(22)

connecting asource of highto the expansion cylinder(14)

via thecrossover passage outlet (27);a crossover expansion valve (XovrE valve)in the crossover passage outlet(27),(26) disposed

the XovrE valve(26)

operable to allow fluid communication between the crossover
30

passage

(22)

and

the

expansion

cylinder(14)duringaportion of the expansion stroke;
an
inlet

exhaust

(53),

valve

(34)

disposed

the exhaust valve

(34)

in

the

exhaustport

operable to allow fluidwo 2010/117713

PCT/US201 0/029029

28
communication to or from the expansion cylinder(14)

via theexhaustoftheexhaustdisposed in the top surface(50)of the

port

inlet

(31)

duringaportionstroke;a recess
5

expansion piston
surfacedistance,
between

(30),

the

expansion

piston

along

line

the

top

a

(60)

clearance

parallelsurfaceand the bottom surface
therecessincludingabottom

(64);

an

10

(60)

expansion piston

(50)
(52)

(30)

( 8 0)

being

a

the

centerline

theexpansion piston

of

axis

of the cylinder headisatshortest

its( 62),
(30)

(33)

when

top dead center(TDC)

position;a recess depthline parallel the15

surface

(64)

(82)

centerline axisof the recess

the expansion pistonanbeing a shortest distance,

expansion(60)( 62),

along abetween the bottom

and the top surface

(50)

of

(30);

ratio

being

the

ratio

of

the

enclosed

volume in the expansion cylinder when the expansion piston
is at its bottom dead center
20

(BDC)

position to the enclosed

volume in the expansion cylinder when the expansion piston
is at its TDC position;
wherein a portion of the recessof the crossover passage outlet(60)

overlaps a portion(27);

wherein a portion the exhaust port inlet
25

overlap any portion of the recess
whereintherecessdepth

The engine(10)

is at least 20 to 1,
30

does not(60); and( 82)

times the expansion piston clearance
2.

(31)

is

between

1. 0 and

3. 0

(80).

of claim 1, wherein the expansion ratio
preferably at least 30 to 1,

and more

preferably at least 40 to 1.
3.

The engine

operabletocylinder

(14)

(10)

initiateof claim 1, wherein the engineacombustion

(10)

is

event

in

the

expansion

while the expansion piston(30)

is descending

wo 2010/117713

PCT/US201 0/029029

29from its TDC position towards its BDC position,

preferably

between 10 and 25 degrees of rotation of the crankshaft (16)
past

the

expansion

piston's

(30)

10

and

degreespast

thepreferably between
5

( 16)

crankshaft

20

TDC

position,ofexpansionandrotation

piston's

more

of

the

( 3 0)

TDC

position.
4.

The engine

recess

( 60)

( 10)

of claim 1,

wherein no portion of theoverlaps any portion of the exhaust port inlet( 31) .
10

5.

The

recessengine
(60)

( 10)

of

claim 1,

overlap

at

least

wherein portions

one

ignition

preferably at least two ignition devices

15

6.

The engine( 10)

of claim 1,

(82)

is

2.0

and

between3.0

ofdevice

the
(32),

(32).

wherein the recess depth

times

the

expansion

pistonclearance (80).
7.

The engine(10)of claim 1, wherein 20% or less of thetotal area of the exhaust port inlet (31), preferably 10% or
less, overlaps the recess
8.
20

(60).

An engine (10), comprising:acrankshaft(16)

rotatable

about

a

crankshaft

axis( 17) ;

an expansion cylinder(14)

including a centerline axis

( 62) ;
an expansion piston
25

expansion

cylindercrankshaft

(16)

(14)

such

(30)

slidably received within theandoperatively

that

the

connected

tothepiston(30)

isexpansion

operable to reciprocate through an expansion stroke and an
exhauststroke during asinglerotation ofthecrankshaft(16), the expansion piston (30) including a top surface (50)30

and an outer perimeter ( 7 4) ;acylinder

head

( 33)

cylinder

( 14)

such

that

cylinder

head

( 33)

faces

a

disposedoverbottomsurface

(52)

of

the

surface

(50)

of

the

the

top

the

expansion

wo 2010/117713

PCT/US201 0/029029

30
expansion piston

5

(30),

the

cylinder headcrossover passage outlet(27)

disposed

therein,theexhaustcrossoverpassageoutletexpansion cylinder
a

a

(53)

port

inlet

(53)

and

the

each

being

proximatethesource

high

(14);

(12/20)(22)

connectingato the expansion cylinder

crossover passage outlet

of

(14)

via the(26)

disposed(27);

a crossover expansion valve
10

includingand an exhaust port inlet(27)

crossover passage

pressure gas(33)(XovrE valve)in the crossover passage outlet(27),

the XovrE valve(26)

operable to allow fluid communication between the crossover
passage

(22)

and

the

expansion

cylinder(14)duringaportion of the expansion stroke;
an
15

inlet

exhaust

(53),

valve

( 34)

disposed

the exhaust valve

(34)

in

the

exhaustport

operable to allow fluid

communication to or from the expansion cylinder(14)

via theexhaustoftheexhaustdisposed in the top surface(50)of the

port

inlet

(31)

duringaportionstroke;a recess
20

expansion piston
surfacedistance,
between

(30),

the

expansion

piston

along

line

the

top

a

(60)

clearance

parallelsurfaceand the bottom surface
therecessincludingabottom

(64);

an

25

(60)

expansion piston

(50)
(52)

(30)

of

( 8 0)

being

a

the

centerline

axis

the

expansion pistonof the cylinder headisatshortest

its( 62),
(30)

(33)

when

top dead center(TDC)

position;a recess depthline parallel the30

surface

(64)

(82)

centerline axisof the recess

the expansion pistonanbeing a shortest distance,

expansion(60)( 62),

along abetween the bottom

and the top surface

(50)

of

(30);

ratio

being

the

ratio

of

the

enclosed

volume in the expansion cylinder when the expansion pistonwo 2010/117713

PCT/US201 0/029029

31

is at its bottom dead center(BDC) position to the enclosed

volume in the expansion cylinder when the expansion piston
is at its TDC position;
wherein the expansion ratio is at least 20 to 1; andwherein the recess depth

5

(82)

is greater than or equal

to the expansion piston clearance (80).
9.

The engine (10) of claim 8, wherein:a portion of the recess( 60)

overlaps a portion of thecrossover passage outlet (27); and10

a portion the exhaust port inlet
any portion of the recess
( 10)

(31)

does not overlap

(60).

10.

The engine

of claim 8,

wherein the recess depth( 82)

is between 1. 0 and 3. 0 times,

preferably between 2. 0

and 3.0 times, the expansion piston clearance (80).
1511.

The engine(10)of claim 8,

the expansion ratio is atleast 30 to 1, preferably at least 40 to 1.
12.

20

The engine

operabletocylinder

(14)

(10)

initiateof claim 8, wherein the engineacombustion

(10)

is

event

in

the

while the expansion piston(30)

is descending

from its TDC position towards its BDC position,

expansion

preferably

between 10 and 20 degrees of rotation of the crankshaft (16)past the expansion piston's (30) TDC position.
13.

The engine

recess
25

( 60)

( 10)

of claim 8,

wherein no portion of theoverlaps any portion of the exhaust port inlet

(31).
14.

The

recessengine
(60)

( 10)

of

claim 8,overlap

at

least

one

wherein portions
ignitiondevice

of

the
(32),

preferably at least two ignition devices (32).
15.
30

The engine(10)of claim 8, wherein 20% or less of thetotal area of the exhaust port inlet (31), preferably 10% or
less, overlaps the recess(60).

wo 2010/117713

PCT/US201 0/029029

1/5

FIG. 1

Prior Art

wo 2010/117713

PCT/US201 0/029029

2/5

,:-s

FIG. 2

Prior Art
41

~26

22

wo 2010/117713

PCT/US201 0/029029

3/5

FIG. 326

33
41 _j_.----11'---f}~~

I ~
I

II
I I

wo 2010/117713

PCT/US201 0/029029

4/5

FIG. 422~--43

L--h---f---/"-39
43

39

50

wo 2010/117713

PCT/US201 0/029029

5/5

~10

FIG. 5

41

22

26
62

INTERNATIONAL SEARCH REPORTInternational application No.
PCT/US2010/029029

A.

CLASSIFICATION OF SUBJECT MA TIER

IPC(8) • F02B 3/06 (2006.01)
USPC • 123/193.6
According to International Patent Classification (IPC) or to both national classification and IPC
B.

FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)
IPC(8)- F02B 3100, 3126, 3128, 23/06 (2010.01)
USPC ·123165R, 66-68, 72, 193.3, 193.6, 276,306, 307, 661
Documentation searched other than minimum documentation to the extent that such documents are included in the fields searchedElectronic data base consulted during the international search (name of data base and, where practicable, search terms used)
USPTO EAST System (US, USPG-PUB, EPO, DERWENT)c.

DOCUMENTS CONSIDERED TO BE RELEVANT
Citation of document, with indication, where appropriate, of the relevant passages

Category•

Relevant to claim No.

X

US 4,050,420 A (CATALDO) 27 September 1977 (27 .09.1977) entire document

1-15

A

US 1,389,337 A (WOLFARD) 30 August 1921 (30.08.1921) entire document

1-15

A

US 2005/0155344 A1 (KOBAYASHI) 21 July 2005 (21.07.2005) entire document

1-15

A

US 2006/0102141 A1 (NAKAYAMA et al) 18 May 2006 (18.05.2006) entire document

1-15

D

Further documents are listed in the continuation of Box C.

•

DSpecial categories of cited documents:"T' later document published after the international filing date o1eriority
date and not in conflict with the ap~lication but cited to un erstand"A" document defining the general state of the art which is not considered
the principle or theory underlying t e invention
to be of particular relevance"E" earlier application or patent but published on or after the international "X" document of particular relevance; the claimed invention cannot be
filing dateconsidered novel or cannot be considered to involve an inventive
step when the document is taken alone"L" document which may throw doubts on priority claim(s) or which iscited to establish the publication date of another citation or other "Y" document of particular relevance; the claimed invention cannot be
special reason (as specified)considered to involve an inventive step when the document is"0" document referring to an oral disclosure, use, exhibition or othercombined with one or more other such documents, such combination
means
being obvious to a person skilled in the art"P" document published prior to the international filing date but later than "&" document member of the same patent family
the priority date claimed
Date of the actual completion of the international search(17 May 2010)
Name and mailing address of the ISAIUS
Mail Stop PCT, Attn: ISAIUS, Commissioner lor Patents
P.O. Box 1450, Alexandria, Virginia 22313-1450
Facsimile No. 571-273-3201
Form PCT/ISA/21 0 (second sheet) (Apnl 2005)

Date of mailing of the international search report

01 JUN 2010
Authorized officer:
Blaine R. Copenheaver
PCT Hetpdesk: 571·272-4300
PCT OSP: 571·272·7774