U.S. patent application number 09/683283 was filed with the patent office on 2002-06-13 for internal combustion engine.
This patent application is currently assigned to Volvo Personvagnar AB. Invention is credited to Marcil, Jean-Pierre.
Application Number | 20020069860 09/683283 |
Document ID | / |
Family ID | 20415944 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020069860 |
Kind Code |
A1 |
Marcil, Jean-Pierre |
June 13, 2002 |
Internal combustion engine
Abstract
The invention relates to an internal combustion engine,
comprising a cylinder block with at least one cylinder barrel, a
cylinder head with at least one inlet channel and exhaust channel
with related inlet and exhaust valves to a combustion chamber
situated above a piston moveable in the cylinder barrel and a crank
case for lubricating oil situated below the piston, wherein the
piston has at least two grooves situated at a distance from each
other, each having a piston ring and a piston collection chamber
contained between the rings. The engine has an expansion chamber
commonly connected to each cylinder barrel via an individual
evacuation port, said port opening out into the respective cylinder
barrel, the expansion chamber forming a communicating connection
between the cylinder barrel and the inlet channel via the
evacuation port and an evacuation channel, said evacuation channel
opening out into at least one inlet channel or inlet manifold. The
evacuation port and the piston are so adapted to each other that
the piston holds the evacuation port open in order to maintain the
connection between the crank case and the inlet channel during the
piston's movement from its top dead center to a position at a
predetermined distance from the top dead center and thereafter
breaks the connection of the evacuation port with the crank case
during its continued movement down to bottom dead center, and that
the collection chamber is connected to the evacuation port when the
piston is near the bottom dead center.
Inventors: |
Marcil, Jean-Pierre;
(Quebec, CA) |
Correspondence
Address: |
KILPATRICK STOCKTON LLP
607 14th STREET, NW
SUITE 900
WASHINGTON
DC
20005
US
|
Assignee: |
Volvo Personvagnar AB
31 SE
Goteborg
SE
SE-405
|
Family ID: |
20415944 |
Appl. No.: |
09/683283 |
Filed: |
December 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09683283 |
Dec 7, 2001 |
|
|
|
PCT/SE00/01166 |
Jun 6, 2000 |
|
|
|
Current U.S.
Class: |
123/568.11 ;
123/672 |
Current CPC
Class: |
F02M 25/06 20130101;
Y02T 10/121 20130101; Y02T 10/12 20130101; F01M 13/00 20130101 |
Class at
Publication: |
123/568.11 ;
123/672 |
International
Class: |
F02M 025/07 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 1999 |
SE |
9902113-1 |
Claims
1. An internal combustion engine comprising: a cylinder block
having at least one cylinder barrel, a piston moveable in the
cylinder barrel, wherein the piston is further comprised of at
least two peripheral grooves situated at a distance from each
other, each having a piston ring, and a piston collection chamber
contained between the rings, a combustion chamber situated above
the piston, a cylinder head having at least one inlet channel and
exhaust channel with related inlet and exhaust valves to the
combustion chamber, a crank case for lubricating oil situated below
the piston, an expansion chamber in the engine, at least one
evacuation port for connecting the expansion chamber to at least
one cylinder barrel, the port opening out into the cylinder barrel,
an evacuation channel opening out into at least one inlet channel
or inlet manifold, wherein the expansion chamber forms a
communicating connection between the cylinder barrel and the inlet
channel via the evacuation port and evacuation channel, and wherein
the piston holds the evacuation port open in order to maintain the
connection between the crank case and the inlet channel during the
piston's movement from its top dead center to a position at a
predetermined distance from the top dead center and thereafter
breaks the connection of the evacuation port with the crank case
during its continued movement down to bottom dead center, and
wherein the collection chamber is connected to the evacuation port
when the piston is near the bottom dead center.
2. The internal combustion engine according to claim 1 further
comprising a cyclone tube arranged into the expansion chamber for
causing the blow-by gases to circulate, thereby centrifugally
forcing oil particles in the blow-by gases into contact with a
surface of the cyclone tube so as to separate the oil from the
gas.
3. The internal combustion engine according to claim 1, wherein the
expansion chamber is arranged on the outside of the cylinder block
with the outside of the cylinder block comprises an inner wall of a
space defining the expansion chamber.
4. The internal combustion engine according to claim 3, wherein the
expansion chamber further comprises a primary and a secondary
chamber.
5. The internal combustion engine according to claim 4, wherein the
expansion chamber further comprises a baffle for separating the
primary and secondary chamber, the baffle being provided with an
aperture for connection between the chambers.
6. The internal combustion engine according to claim 1, further
comprising: at least two expansion chambers arranged at the engine,
and at least two evacuation ports arranged in each cylinder barrel,
each port leading to respective expansion chamber.
7. The internal combustion engine according to claim 1, wherein the
at least one evacuation port further comprises at least two
orifices in order to provide sufficient flow area for the blow-by
gases.
8. The internal combustion engine according to claim 1, wherein the
expansion chamber in its lowermost portion further comprises a
vapor separator for connecting the expansion chamber with the crank
case.
9. The internal combustion engine according to claim 1, further
comprising a check valve arranged in the evacuation channel for
preventing the mixture of air and fuel in the inlet channel from
entering into the expansion chamber.
10. The internal combustion engine according to claim 5, further
comprising a check valve arranged in the aperture.
11. The internal combustion engine according to claim 1, wherein
the piston further comprises: a collecting chamber between the
piston ring grooves for collecting unburned fuel-air mixture and
combustion gases that pass the upper piston ring, and a
communicating connection between the collecting chamber and the
inlet channel via the evacuation port, expansion chamber and
evacuation channel that is created due to the orientation of the
evacuation port in relation to the collecting chamber after a
predetermined movement of the piston from its top and bottom dead
center.
12. The internal combustion engine according to claim 11, wherein
the collecting chamber further comprises a peripheral groove
between the piston ring grooves.
13. The internal combustion engine according to claim 12, wherein
the peripheral groove is wider and deeper than the piston ring
grooves.
14. The internal combustion engine according to claim 13, wherein
the width of the peripheral groove is substantially equal to the
height of the evacuation port.
15. The internal combustion engine according to claim 1, wherein
the cylinder block further comprises one or more cooling jackets
for cooling fluid, and wherein the expansion chamber is situated
adjacent to a wall of at least one cooling jacket.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of International
Application No. PCT/SE00/01166, filed Jun. 6, 2000, which claims
priority to Swedish Application No. 9902113-1, filed Jun. 7,
1999.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to internal combustion
engines. More specifically, the present invention relates to
reducing or eliminating the combination of combustion gases and oil
in the crankcase of an internal combustion engine.
[0004] 2. Background Information
[0005] In an internal combustion engine, providing a piston ring
seal between the pistons and the surrounding cylinder walls that
completely seals off the combustion chambers from the crank case of
the engine has yet to be done. A certain small quantity of
combustion gases, or blow-by, flows past the piston ring down into
the crankcase of the engine. In order to avoid a high overpressure
in the crankcase at least partially due to the blow-by gases, the
crankcase must be ventilated. The more effective the ventilation
is, the lower the overpressure in the crank case and, therefore,
the lower the engine pumping losses become. On the other hand, if
there is a loss in crankcase pressure, oil consumption can increase
due to oil vapor carried by the blow-by being evacuated by the
positive crankcase ventilation system.
[0006] In modern engines, closed crankcase ventilation is used in
order to minimize environmental effects. Normally, any blow-by
gases and water vapor present are allowed to enter the crankcase
where they are mixed vigorously with and become trapped within the
oil droplets suspended in the crankcase. Afterwards, the oil
droplets are led out from the crankcase via a hose to the inlet
manifold of the engine before the throttle, where they are mixed
with the intake air. In order to separate oil out of the oil mist
unavoidably mixed with the blow-by gases, different types of
filters and oil traps are used in the crankcase ventilation.
Typically, crankcase ventilation systems separate oil from blow-by
after they have been mixed together. Also, overpressure in the
crankcase that increases with power demand is minimized by adding a
pressure regulator.
[0007] Accordingly, there is a need for an internal combustion
engine that reduces or eliminates overpressure in the crankcase
that occurs with an increase in power demand. Further, there is a
need for an internal combustion engine that minimizes or avoids the
mixing of blow-by gases and oil.
SUMMARY OF INVENTION
[0008] The present invention includes a cylinder block with at
least one cylinder barrel, a cylinder head with at least one inlet
channel and exhaust channel with associated inlet and output valves
for a combustion chamber. The combustion chamber is located above a
piston moveable in the cylinder barrel. Below the piston is a crank
case wherein lubricating oil is found. The piston is shaped with at
least two peripheral grooves situated at a distance from each
other, each having its own piston ring. A piston collection chamber
is contained between the rings.
[0009] The present invention provides a means of avoiding the
mixing of blow-by and oil. This is achieved by evacuating unburned
blow-by mixture and combustion gases directly into an expansion
chamber via an evacuation port in the cylinder wall, instead of
letting them expand in the crankcase. Therefore, the gases do not
mix intimately with the oil in the crankcase, facilitating the
separation and oil trap operation. When expanding, the gases lose
much of the flow rate energy that could otherwise allow them to
carry and mix with oil droplets present in or near the evacuation
port.
[0010] Even with a pressure regulator provided, engines are
inclined to have a much higher pressure in the crankcase than in
the combustion chamber during intake stroke. This pressure tends to
press both the oil film on the cylinder wall and the oil mist in
the crankcase past the oil scraper ring of the piston and into the
combustion chamber of the engine. In order to prevent to as best
possible this oil flow to the combustion chamber, the ring tension
must be high for the oil scraper ring. The oil scraper ring is the
component that causes the greatest internal friction in the
engine.
[0011] The oil that penetrates into the combustion chamber of the
engine does not just cause pollution in the engine exhaust gases,
with consequential strain on the catalyzer. It also lowers the
octane number of the fuel. In modern engines with knock sensors and
automatic ignition advance, this leads to a retarding of the
ignition with consequential increased fuel consumption. Further,
engine oil consumption and the costs of replacing used oil are
directly dependent on the amount of oil that penetrates into the
combustion chamber due to the pressure difference between the crank
case and the cylinder space above the piston.
[0012] Oil combustion also contributes to deposits in and around
the piston rings. These deposits can interfere with the proper
operation of the rings, and may eventually immobilize the rings,
along with deteriorating their function.
[0013] The present invention provides an engine wherein the
pressure difference between the engine crankcase and its air intake
is maintained as low as possible. This pressure difference forces
the lubricating oil past the piston rings and into the combustion
chamber during the intake stroke of the engine. In other words, the
pressure due to the pressure difference between the crankcase and
the air intake during all operating conditions is lowered, thereby
minimizing oil consumption, as well as pumping, windage and
friction losses. Further, the present invention eliminates the need
for a colder oil trap for condensing and recovering oil, and also
prevents the system from freezing.
[0014] In the present invention, the cylinder block has been
designed with an evacuation port for each cylinder. The channel
opening into the cylinder barrel forms a communicating connection
between the cylinder barrel and the intake channel, preferably in
close proximity to an engine coolant passage. The evacuation
channel outlet and the piston are adapted to each other such that
the piston holds the evacuation channel open during movement of the
piston from its top dead center to a position at a predetermined
distance from top dead center (TDC), thereby maintaining the
connection between the crankcase and the intake channel.
Thereafter, the piston breaks the connection between the evacuation
channel and the crankcase by its continued movement down to bottom
dead center (BDC).
[0015] Also, the cylinder outlet port of the evacuation channel is
adapted to provide communication with the piston collection chamber
during the movement of the piston from TDC to a position at a
predetermined distance from TDC. However, since the crankcase
pressure in previously known engines is relatively high, and the
volume and the rate of blow-by gases intended to flow into the
evacuation channel is relatively high, the flow resistance in the
evacuation channel becomes relatively high.
[0016] An oil trap is arranged in the evacuation channel to prevent
oil particles in the blow-by gases flowing into the evacuation
channel from reaching the intake channel and burning in the
combustion chamber. However, since the flow rate of the blow-by
gases in the evacuation channel is relatively high, it is difficult
to prevent all oil particles from reaching the inlet channel.
[0017] The present invention provides an engine wherein the
pressure pulses and the flow rate of blow-by gases in the
evacuation channel is lower than in previously known engines,
minimizing the flow velocity of the blow-by gases and preventing
oil particles from reaching the inlet channel, while evacuating
blow-by to the air inlet.
[0018] This is achieved according to the invention by providing the
engine with an expansion chamber commonly connected to each
cylinder via an individual evacuation port. The port opens out into
the respective cylinder barrel. The expansion chamber forms a
communicating connection between the cylinder barrel and the inlet
channel via the evacuation port and an evacuation channel. The
evacuation channel opens out into at least one inlet channel or
inlet manifold, and the evacuation port and piston are so adapted
to each other that the piston holds the evacuation port open,
thereby maintaining the connection between the crankcase and the
inlet channel during the piston's movement from its top dead center
to a position at a predetermined distance from the top dead center.
Thereafter, the piston breaks the connection of the evacuation port
with the crankcase during its continued movement down to bottom
dead center. The collection chamber is connected to the evacuation
port when the piston is near the bottom dead center. This allows
better pressure equalization between the inlet channel or manifold
and the crankcase, while providing necessary communication and
reducing the amount of oil splashes which could reach the port.
[0019] By providing a chamber having a large cross section between
the evacuation port in the cylinder barrel and the inlet channel,
blow-by gases coming from the evacuation port can expand, thereby
reducing the pressure pulse magnitude and slowing down the flow of
blow-by to a less turbulent state, resulting in more oil particles
settling and being trapped. This expansion chamber is also provided
with a return for permitting the oil to return to the crankcase
from a less turbulent area of the chamber.
[0020] In a preferred embodiment, a cyclone tube is arranged in the
expansion chamber in proximity to the evacuation ports. The cyclone
tube, which can be double open ended, causes the blow-by gases to
circulate so that oil particles in the blow-by are centrifugally
forced into contact with a surface. Also, baffles can be arranged
in the expansion chamber for increasing the contact area for the
oil to cling to, and for reducing the pressure and speed of the
circulating blow-by gas. By maintaining a negative pressure, water
vapor will vaporize easily while oil droplets will cling to the
cyclone surface due to its higher viscosity.
[0021] The piston is a conventional cylindrical piston that,
according to the invention, can be provided with a shield on the
side facing the opening of the evacuation port, which forms a
screening-off towards the opening of the evacuation port thereby
limiting the intrusion of oil splashes. The screen has a greater
clearance towards the cylinder barrel wall than the piston cylinder
so that the crank case, via the gap formed through the greater
clearance, and the evacuation port are joined with the inlet
channel, via the expansion chamber and the evacuation channel
during a predetermined part of the path of movement of the
piston.
[0022] Preferably, each piston has a collection chamber between the
piston ring grooves for collecting unburned fuel-air mixture and
combustion gases that pass the upper piston ring. The cylinder
preferably has an evacuation port so orientated in relation to the
collecting chamber that, after a predetermined movement of the
piston from its top or bottom dead center portion, a communicating
connection is established between the piston collection chamber and
the inlet channel via the evacuation channel and the expansion
chamber. In this way, unburned fuel-air mixture and combustion
gases are prevented from reaching the crankcase. Instead they are
ventilated out through the evacuation channel into the expansion
chamber. They then flow to the inlet channel due to an overpressure
that occurs in the collection chamber, while an underpressure
occurs in the cylinder evacuation channel. Otherwise, unburned
fuel-air mixture trapped under the first piston ring would flow
back into the combustion chamber during the expansion stroke as
soon as the cylinder pressure fell below the pressure of the
mixture. However, this would occur too late for the mixture to be
able to be burnt. To reduce pressure due to the volume of unburned
fuel-air mixture and combustion gases in the collection chamber,
the piston can be provided with a space, such as plurality of
bores, communicating with the collection chamber. In doing so, the
total volume of the collection chamber is increased, leading to a
reduction in pressure of the gases taken up in the collection
chamber.
BRIEF DESCRIPTION OF DRAWINGS
[0023] The invention is described more closely with reference to
the embodiments shown on the accompanying drawings, where:
[0024] FIG. 1 illustrates a cross sectional view through a cylinder
block of one embodiment of an engine according to the
invention,
[0025] FIG. 2 illustrate a cross sectional view through a cylinder
head of one embodiment of an engine according to the invention,
[0026] FIG. 3 illustrates a cross sectional detail view of piston
ring grooves and a collection chamber of a piston of one embodiment
of an engine according to the invention,
[0027] FIG. 4 illustrates a cross sectional schematic
representation of another embodiment of an engine according to the
invention,
[0028] FIG. 5 illustrates a cross sectional schematic
representation of a third embodiment of an engine according to the
invention, and
[0029] FIG. 6 illustrates a perspective view of a cylinder block of
one embodiment of an engine according to the invention.
DETAILED DESCRIPTION
[0030] In FIG. 1, reference number 1 denotes a cylinder block and
reference number 2 a cylinder barrel in which a piston 3 is
displaceably mounted. The piston 3 is connected with a crank shaft
5 by a connecting rod 4 rotatably mounted in the crankcase 6 of the
cylinder block 1. A lower frame bearing bridge and an oil pan,
which together close the crank case, are omitted from FIG. 1. An
evacuation port 9 is arranged in the cylinder block 1. The port 9
opens out into an expansion chamber 8 arranged on the outside of,
preferably adjacent to, the engine block 1. Each port 9 can include
one or more orifices (not shown) for providing sufficient flow area
for the blow-by gases. An evacuation channel 10 opens out from the
expansion chamber 8 into an inlet channel 11 in the cylinder head
12 of the engine (see FIG. 2). As seen from FIG. 2, the evacuation
channel opens out into the inlet channel 11 relatively close to the
inlet valve 13 in the combustion chamber 14. An exhaust channel 15
with an exhaust valve 16 also opens out into the combustion chamber
14.
[0031] The piston 3 preferably has a first and second piston ring
groove 17, 18, respectively, for a first and second compression
ring (not shown), and a third piston ring groove 19 for an oil
scraper or control ring. A collection chamber 20, in the form of a
groove, the width and depth of which may be considerably greater
than the width and depth of the piston ring groove, is found in the
part of the piston between the piston ring grooves 17, 18. This is
illustrated in FIG. 3.
[0032] In order to optimize the time-area (the period in which the
port 9 communicates with the collection chamber 20 and the
cross-section of the evacuation port 9) and reduce the piston deck
height (the distance between the top of the piston and the wrist
pin axis. 3a), the height H.sub.p of the port 9 should be smaller
than, or preferably equal to, the height H.sub.G of the collection
chamber groove 20. This will allow maximum flow capacity with
minimum piston deck height. At the same time, the distance H.sub.U
between the lower edge of the first, upper compression ring 17 and
the upper edge of the collection chamber groove 20 must be equal or
larger than the height H.sub.p of the port 9. This will maximize
the duration and the timing of the gas flow between the collection
chamber 20 and the port, while minimizing the deck height, as the
time the piston spends near the BDC is relatively long.
[0033] Similarly, the distance H.sub.L between the upper edge of
the second, lower compression ring 18 and the lower edge of the
collection chamber groove 20, must also be equal to or larger than
the height H.sub.p of the port 9. This is necessary in order to
prevent blow-by from entering the crankcase. This achieved by
avoiding communication between the collection chamber 20 and the
crankcase 6 when the port 9 is overlapping the second compression
ring 18.
[0034] The height H.sub.G of the collection chamber groove 20 must
be equal to or smaller than either of the heights H.sub.U or
H.sub.L between the upper or lower compression rings 17, 18 and the
upper or lower edges of the collection chamber groove 20,
respectively. Also, the lower edge of the first compression ring 17
must always be level with or above the upper edge of the port 9 at
BDC in order to prevent pressurized gas flow from the combustion
chamber into the port 9, through the expansion chamber 8 and into
the crankcase 6.
[0035] In a preferred embodiment, the heights H.sub.G, H.sub.U and
H.sub.L are equal, or near equal within the parameters stated
above.
[0036] In a further embodiment the piston 3 can be designed with a
shield 21 on the side which faces the opening of the evacuation
port 9. The axial extent of the shield 21 is approximately the same
as the length of the piston 3 from the lower edge of the oil
scraper groove to the lower edge of the piston. The smallest width
of the shield 21 at the lower part 21 a is approximately four times
the diameter of the evacuation port 9.
[0037] The width of the lower part may be chosen up to the greatest
width of the upper part 21b, which may be up to approximately one
sixth of the circumference of the piston. As seen in FIG. 1, the
relationship between the shield 21 and the piston is such that a
gap 22 is formed between the wall of the cylinder barrel 2 and the
shield wall 21c. The width of the gap 22 should preferably be about
a fourth of the diameter of the opening of the evacuation port 9.
However, the sizes should be chosen so that the 22 along with a
stepped shield 21 are dimensioned so as to give the crank case
vapor a constricted passage into the evacuation port 9, as well as
limit oil splashes from reaching the evacuation port 9. When
forming the stepped shield 21, there will be an upper portion with
a small clearance between the shield surface and the cylinder wall
and a lower portion with a larger clearance.
[0038] The piston 3 with the shield 21 functions as a moving valve
element that connects the crank case 6 with the expansion chamber
8, and thereby the inlet channel 11, from the top dead center of
the piston 3 to about half of an effective piston stroke. In this
way, the pressure difference between the crank case 6 and the inlet
channel 11 is reduced. Closing the evacuation port 9 reduces the
inner cyclic pressure pulse effect in the crank case 6 that would
otherwise lead to an increased oil transfer due to the carry-over
of suspended oil to the expansion chamber 8. The relatively low
pressure in the crank case 6 that occurs with a low and medium
throttle opening also leads to reducing the negative effects of
these inner pressure pulses. This makes it possible to dimension
the engine with a small crank case volume, even under heavy
load.
[0039] The expansion chamber 8, evacuation port 9 and evacuation
channel 10 are pre-warmed continuously by the cooling fluid in the
adjacent cooling jacket 23, eliminating the requirement for
expensive heated pipes or tubes. This reduces the costs and risk
for freezing at extremely low temperatures.
[0040] Oil from the oil scraper ring is prevented from being taken
into the inlet channel 11 via the evacuation port 9 through
substantially the same underpressure existing in the crank case
under the piston as in the inlet channel 11. As a result, the
tension in the oil scraper ring can be reduced, reducing friction
between the piston and the cylinder. Oil in the oil mist that
reaches the evacuation port 9 is separated out by means of the
expansion chamber 8, as will be described in more detail according
to a second embodiment illustrated in FIG. 4.
[0041] Blow-by gases that pass the first compression ring in the
groove 17 during the early expansion stroke of the piston 3 are
retained in the collection chamber formed by the collection chamber
20 and the bore 7. Once the piston 3 has completed the main part of
the expansion stroke, the collection chamber 20 and the bore are
connected with the evacuation port 9. Blow-by gases under pressure
can now expand and be evacuated to the inlet channel 11 via the
evacuation port 9, expansion chamber 6 and evacuation channel 10.
No further air or gas is used to push out the blow-by gas. However,
the gas and some oil is evacuated through its own pressure.
[0042] When the piston 3 begins moving upwards during the exhaust
stroke after having passed BDC, any remaining gas is evacuated.
This is possible since the collection chamber 20 is still connected
with the evacuation port 9 at the piston's 3 initial movement
upwards. Should blow-by gas still remain in the collection chamber
20 during the final part of the exhaust stroke and the main part of
the inlet stroke, this gas can be evacuated to the inlet channel 11
when the collection chamber 20 and port 9 are again joined
together.
[0043] Thus, during all working strokes the collection chamber 20
and the bore at times are connected with the evacuation port 9,
ensuring that the collection chamber 20 and bore 7 are properly
emptied of vapor at the beginning of each expansion stroke. This is
important for keeping the collection chamber 20 clean and free of
residue.
[0044] The part of the hydrocarbon ("HC") emission which must be
neutralized in a conventional engine's catalyzer is created from
the unburned fuel-air mixture that is pressed past the first
compression ring during the compression stroke and trapped between
the compression rings. This mixture normally flows back to the
combustion chamber 14 as reverse blow-by when the pressure in the
combustion chamber 14 during the expansion stroke is less than the
pressure in the mixture between the rings. However, this fuel-air
mixture can accumulate and return to the combustion chamber 14 too
late for burning and for contributing to the output of the engine.
With the help of the evacuation port 9 the unburned fuel-air
mixture can be evacuated from the collection chamber 20 before the
pressure in the combustion chamber becomes so low that the mixture
can flow past the first piston ring and back into the combustion
chamber 14. The mixture can then be burned in the next power
stroke, instead of being pulled out with the exhaust or drawn into
the crankcase.
[0045] Referring to the embodiment illustrated in FIG. 1, the
expansion chamber 8 in its lowermost portion is provided with a
vapor separator 24 that connects the expansion chamber 8 with the
crank case 6. The volume of the expansion chamber 8 allows the
blow-by gases to expand and slow down to a calmer or less turbulent
condition in the expansion chamber 8, thereby allowing oil to be
trapped. Oil particles in the expansion chamber 8 flow by gravity
down to the lowermost portion. When the oil reaches the vapor
separator 24, the oil returns to the crank case 6. The vapor
separator 24 is situated in a less turbulent area of the expansion
chamber 8. This will make it easy for the oil to pass the vapor
separator 24 without being disturbed by the blow-by gases in the
expansion chamber 8.
[0046] The evacuation channel 10 is preferably arranged in the
uppermost portion of the expansion chamber 8. In this way the
blow-by gases have to pass a relatively long distance through an
area heated by the engine in the expansion chamber 8 before they
reach the evacuation channel 10, so that the blow-by gases are
allowed to expand and slow down as mentioned above. Because the
gases flow through a heated area, the water vapor in the blow-by is
prevented from freezing.
[0047] In another embodiment illustrated in FIG. 4, a cyclone tube
25 is arranged into the expansion chamber 8. The cyclone tube 25
makes the blow-by gases circulate, causing oil particles in the
blow-by gases to cling to surfaces in the cyclone due to the
centrifugal force of the gas. Baffles can be arranged in the
expansion chamber 8 in order to further increase the contact
surface in the chamber 8, as well as reduce the speed of the
circulating oil droplets in the blow-by gases.
[0048] A one-way check valve 27, such as a reed valve, is arranged
in the evacuation channel 10. The check valve 27 prevents a
pressure build-up in the air intake from propagating in the
expansion chamber during sudden acceleration or transient throttle
application. In such cases, the check valve 27 remains closed until
the pressure in the expansion chamber 8 exceeds the pressure in the
air intake. By doing so, a sudden loss of underpressure in the
expansion chamber 8 is avoided. Although the pressure in the
chamber will begin to rise under such conditions, the delay is
sufficient enough to ensure proper operation of the system until
the next opening of the check valve 27.
[0049] Alternatively, in a third embodiment shown in FIG. 5, the
expansion chamber could be divided into a primary 8a and a
secondary 8b chamber. The chambers 8a, 8b can be separated by an
additional baffle, or by placing the check valve 27 between the
chambers. Preferably, the secondary chamber 8b is smaller than the
primary chamber 8a and is in direct communication with the
evacuation channel 10.
[0050] Since the pressure and flow rate of the blow-by gases in the
expansion chamber 8 is lower than in the evacuation channel
mentioned in the introduction, the flow resistance of the blow-by
gases is minimized. The low flow rate of the blow-by gases reduces
the amount of oil particles reaching the inlet channel 11. Also,
the fact that the engine is operated with crankcase underpressure,
water vapor exiting the collection chamber 20 remains in vapor form
and is easily evacuated.
[0051] In the embodiments above, only one expansion chamber 8 on
the outside of the cylinder block 1 is disclosed. However, it is
possible to arrange expansion chambers 8 on either side or several
on one side of the engine, so that if two expansion chambers are
disposed directly on the engine, then at least two expansion
chambers 8 are disposed directly on the engine and so that at least
two evacuation ports 9 are arranged in each cylinder barrel 2, each
port 9 leading to its respective expansion chamber 8. Thus, several
evacuation ports 9 can be arranged in each cylinder barrel 2.
[0052] In FIG. 6, a perspective view of one embodiment of an engine
according to the invention is shown. The expansion chamber 8 is
arranged on the outside of the cylinder block 1 so that the outside
of the cylinder block 1 constitutes an inner wall of the space
defining the expansion chamber 8. Preferably, the side walls 28
defining the space which constitutes the expansion chamber 8 are
integral with the cylinder block
[0053] A plate or cover 29 is arranged hermetically on the side
walls 28 of the expansion chamber 8. The cover 29 can be provided
with a heat insulating layer.
[0054] The expansion chamber 8 is commonly connected to each
cylinder barrel 2 via an evacuation port 9 arranged in each
cylinder barrel 2. However, the expansion chamber 8 can be divided
in compartments, for example, one for each cylinder barrel 2.
[0055] While there has been disclosed effective and efficient
embodiments of the invention using specific terms, it should be
well understood that the invention is not limited to such
embodiments as there might be changes made in the arrangement,
disposition, and form of the parts without departing from the
principle of the present invention as comprehended within the scope
of the accompanying claims.
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