U.S. patent application number 09/681937 was filed with the patent office on 2001-12-27 for piston.
Invention is credited to Marcil, Jean-Pierre.
Application Number | 20010054408 09/681937 |
Document ID | / |
Family ID | 20413896 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054408 |
Kind Code |
A1 |
Marcil, Jean-Pierre |
December 27, 2001 |
Piston
Abstract
A piston for reciprocal movement in a cylinder in an internal
combustion engine is disclosed. The piston has a lateral surface
that is provided with at least two spaced peripheral piston ring
grooves for individual piston rings. A collection chamber is
arranged between the piston ring grooves. This collection chamber
is made of a peripheral groove arranged in the lateral surface and
at least one space, which communicates with the collection chamber,
is arranged in the piston. The collection chamber and the space are
made to take up uncombusted air-fuel mixture and combustion gases
that have passed one of the piston rings.
Inventors: |
Marcil, Jean-Pierre;
(Quebec, CA) |
Correspondence
Address: |
TRACY W. DRUCE
KILPATRICK STOCKTON LLP
11130 SUNRISE VALLEY DRIVE
SUITE 300
RESTON
VA
20191-4329
US
|
Family ID: |
20413896 |
Appl. No.: |
09/681937 |
Filed: |
June 28, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09681937 |
Jun 28, 2001 |
|
|
|
PCT/SE99/02217 |
Nov 29, 1999 |
|
|
|
Current U.S.
Class: |
123/193.6 ;
123/193.4 |
Current CPC
Class: |
F01M 13/00 20130101;
F16J 9/12 20130101 |
Class at
Publication: |
123/193.6 ;
123/193.4 |
International
Class: |
F02F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 1998 |
SE |
SE9804585-9 |
Claims
1. A piston designed for reciprocating movement in a cylinder in an
internal combustion engine, said piston comprising: a lateral
surface provided with at least two peripherally spaced piston ring
grooves for individual piston rings, a collection chamber arranged
between said piston ring grooves, said collection chamber further
comprising a peripheral groove in said lateral surface, and at
least one space arranged in the piston for communicating with said
collection chamber, wherein said collection chamber and said at
least one space collect uncombusted air-fuel mixture and combustion
gases that have passed one of said piston rings.
2. The piston according to claim 1 wherein said space further
comprises at least one elongated channel having a first opening
opening into said collection chamber.
3. The piston according to claim 2 wherein said channel extends
through the piston and further comprises a second opening opening
into said collection chamber.
4. The piston according to claim 1 wherein said space further
comprises a plurality of channels extending through the piston.
5. The piston according to claim 4 wherein said plurality of
channels are essentially parallel.
6. The piston according to claim 4 wherein said plurality of
channels are interconnected.
7. The piston according to claim 2 wherein said at least one
channel is further comprised of at least one bore through the
piston.
8. The piston according to claim 1 wherein said peripheral groove
is further comprised of a width substantially equal to the height
of an opening formed in the cylinder of an evacuation channel
arranged for uncombusted air-fuel mixture and combustion gases.
9. The piston according to claim 8 wherein the height of said
lateral surface of the piston between said collection chamber and
said at least first piston ring groove and said lateral surface
between said collection chamber and said at least second piston
ring groove are at least equal to the height of the opening of said
evacuation channel.
Description
Cross Reference to Related Applications
[0001] This is a continuation patent application of International
Application Number PCT/SE99/0221 7 filed Nov. 29, 1999 that
designates the United States. The full disclosure of said
application, in its entirety, is hereby expressly incorporated by
reference into the present application.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to a piston designed for
reciprocating movement in a cylinder in an internal combustion
engine. More specifically, the present invention relates to a
piston having a lateral surface that is provided with at least two
spaced peripheral piston ring grooves for individual piston
rings.
[0004] 2. Background Information
[0005] It is known that it is not possible in an internal
combustion engine to provide piston ring sealing between pistons
and their surrounding cylinder walls that completely seals off the
combustion chambers from the crankcase of the engine. A certain
small quantity of combustion gases, referred to as blow-by, always
flows past the piston ring and down into the crankcase of the
engine. In order to prevent excessive overpressure, partially
caused by the blow-by gases, from occurring in the crankcase, the
crankcase must be ventilated. The more effective the ventilation is
the lower the overpressure in the crankcase will be and, therefore,
the lower the engine pumping losses will be.
[0006] In modern engines, closed crankcase ventilation minimizes
environmental effects. Normally, the blow-by gases are led out from
the crankcase via a hose to the inlet manifold of the engine before
the throttle and mix with the intake air. In order to separate oil
unavoidably mixed with blow-by out of the oil mist, different types
of filters and oil traps are used in the crankcase ventilation. All
previously known crankcase ventilation systems have not made it
possible to minimize a certain overpressure in the crankcase that
increases as power demand increases. This means that a much higher
pressure exists in the crankcase of the engine than in the
combustion chamber during the intake stroke. This crankcase
pressure tends to press 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 minimize oil flow to the combustion chamber,
the ring tension must be high for the oil scraper ring. The oil
scraper ring is the one component that causes the greatest internal
friction in the engine. The oil that nevertheless penetrates into
the combustion chamber of the engine not only causes pollution in
the engine exhaust gases, but also places strain on the catalytic
converter. Further, it lowers the octane rating of the fuel, which
in modern engines with knock sensors and automatic ignition advance
leads to a retarding of the ignition and thus increased fuel
consumption. Last but not least, the oil consumption of the engine
itself and the cost of replacing used oil are directly dependent on
how much oil penetrates into the combustion chamber because of the
pressure difference between the crankcase and the cylinder space
above the piston.
SUMMARY OF INVENTION
[0007] The present invention provides a piston that can both take
up at least a portion of the volume of combusted and/or uncombusted
air-fuel mixture which, during the combustion stroke, is pressed
past the piston rings, and obtain a reduction in the pressure of
the volume of combusted and/or uncombusted air-fuel mixture taken
up in the piston. This is accomplished by arranging a collection
chamber between the piston ring grooves. The collection chamber has
a peripheral groove in the lateral surface and at least one space
arranged in the piston that communicates with the collection
chamber. The collection chamber and space collect uncombusted
air-fuel mixture and combustion gases that have passed at least one
of the piston rings.
[0008] The design according to the invention makes it possible to
maintain substantially near equilibrium pressure between the
combustion chamber and the crankcase. This means that an
underpressure is present in the crankcase during the inlet stroke.
The pressure difference over the piston rings becomes so negligible
that ring tension in the oil scraping ring is reduced to a fraction
of what is normal without the risk of oil penetration from the
crankcase to the combustion chamber.
[0009] In addition to the direct effects that the pressure
balancing gives in the shape of lower oil and fuel consumption,
important secondary effects are attained. Lower ring tension,
producing a lower internal friction with consequential lower fuel
consumption, leads to lower starting power for the starting motor,
i.e., smaller starting motor and starting battery. A smaller
quantity of pollution in the exhaust gases caused by oil in the
combustion chamber means a lower load on the catalytic converter,
which can be made smaller. Finally, the need for external
components such as heating arrangements for preventing blow-by from
freezing, oil traps, and hoses with associated connection parts can
be eliminated, leading to cost savings.
[0010] Unavoidably, a small quantity of blow-by, unburnt fuel and
other pollutants that reach the crankcase cannot be ventilated out.
This quantity remains as a suspension in the oil in the crankcase,
contributing to an accelerated ageing process of the oil and
impairing its lubricating qualities. This, in turn, influences the
life span of the engine.
[0011] Preferably, the cylinder in which the piston is designed for
reciprocating motion is provided with an evacuation channel
oriented relative to the collection chamber so that, after a
predetermined movement of the piston from its upper or lower dead
point, a communication is established between the collection
chamber and the evacuation channel. This channel, in turn
advantageously communicates with an intake channel of the internal
combustion engine.
[0012] In this manner, uncombusted air-fuel mixture and combustion
gases are prevented from reaching the crankcase. Instead, they are
ventilated directly into the evacuation channel and flow to the
intake channel, since there is overpressure in the collection
chamber while there is underpressure in the evacuation channel.
Without this structure, uncombusted air-fuel mixture trapped
beneath the first piston ring would flow back into the combustion
chamber during the expansion stroke as soon as the cylinder
pressure drops below the pressure of the mixture. However, this
would occur too late for combustion of the mixture. By arranging a
space in the piston that communicates with the collection chamber,
a relatively large volume is created in the piston. This volume is
so great that the pressure of the air-fuel mixture and the
combustion gases drops in the collection chamber and in the
space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described in more detail with
reference to the accompanying drawings, which show one example,
where:
[0014] FIG. 1 illustrates a side plane view of a piston according
to the invention;
[0015] FIG. 2 illustrates a cross section of the piston along the
line 11-11 in FIG. 1; and
[0016] FIG. 3 illustrates a cross section through a cylinder block
in which a piston according to the invention is disposed.
DETAILED DESCRIPTION
[0017] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale, some features may be exaggerated or
minimized to show details of particular components or processes.
Therefore, specific structural and functional details disclosed
herein are not to be interpreted as limiting, but merely as a basis
for the claims and as a representative basis for teaching one
skilled in the art to variously employ the present invention.
[0018] FIG. 1 shows one example of a piston having a lateral
surface 2 and a piston top surface 3. The lateral surface 2 has at
least two spaced peripheral piston ring grooves 4, 5, each for
holding a piston ring (shown in FIG. 3). A plurality of spaces in
the form of elongated channels 6 is arranged in the piston 1. These
channels 6 open into a collection chamber 7 formed between the
piston ring grooves 4, 5. The piston thus has a first 4 and a
second piston ring groove 5 between which the collection chamber 7
is found. The first and second piston ring grooves 4, 5 are able to
hold a pair of piston rings (not shown in FIG. 1) in the form of
compression rings. A third piston ring groove 8 is also arranged on
the lateral surface 2 of the piston 1 for holding an oil scraper
ring (not shown). The distance between the two piston ring grooves
4, 5 is preferably somewhat greater than what is usual in pistons 1
for a conventional multi-cylinder gasoline engine.
[0019] FIG. 2 illustrates a cross section through the piston 1
along the line II-II in FIG. 1. The channels 6 are made as
through-bores in the piston 1, each opening with a first and a
second opening 9, 10 into the collection chamber. The channels 6
are essentially parallel to each other. However, the channels 6 may
be arranged in different directions in relation to each other. They
may also be interconnected so that they communicate with each
other. It is also possible to make the channels 6 into a single
cavity.
[0020] As can be seen in FIGS. 1 and 2, the collection chamber 7
consists of a peripheral groove arranged on the lateral surface 2.
The groove takes up uncombusted air-fuel mixture and combustion
gases that have passed the piston ring in the first piston ring
groove 4. The peripheral groove, which forms the collection chamber
7, may be broader than the piston ring grooves 4, 5, 8. The width
of the groove is the dimension of the groove in the axial direction
of the piston 1.
[0021] The cooperation of the piston 1 with a cylinder 12 in an
internal combustion engine 11 will be explained with reference to
FIG. 3. Blow-by gases, which during the early expansion stroke of
the piston 1 flow past a first piston ring 13 adjacent the piston
top surface 3, are retained in the collection chamber 7 and
channels 6 by a second piston ring 14 in the second piston ring
groove 5 on the other side of the collection chamber 7. Once the
piston 1 has completed most of its expansion stroke, the collection
chamber 7 is connected to an evacuation channel 15 opening into the
cylinder 12. The evacuation channel 15 is connected to an intake
channel (not shown) of the engine 11. Blow-by, which is under
pressure, can now expand and be evacuated to the intake channel via
the evacuation channel 15. No additional air or gas is used to
press the blow-by gas out. Rather, its own pressure evacuates the
gas. When the piston 1 begins to move upwardly during the exhaust
stroke after having passed the lower dead center point, any
remaining amount of gas can be evacuated. This is because the
collection chamber 7 is still in communication with the evacuation
channel 15 during the initial upward movement of the piston 1. If
blow-by gas still remains in the chamber 7 and channels 6 during
the final portion of the exhaust stroke and during the majority of
the intake stroke, this gas can be evacuated to the intake channel
when the chamber 7 and the evacuation channel 15 are again
connected to each other.
[0022] In all of the operating strokes, the collection chamber 7 is
thus joined with the evacuation channel 15 during certain periods.
This assures that the collection chamber 7 and channels 6 are
emptied at the beginning of each expansion stroke. in order to
assure good communication between the collection chamber 7 and the
evacuation channel 15, the width of the peripheral groove forming
the collection chamber 7 is preferably approximately equal to the
height of the opening 16 of the evacuation channel 15 into the
cylinder 12. Here the height of the opening 16 is the extent of the
opening 16 in the axial direction of the cylinder 12. The height of
the lateral surface 2a of the piston 1 between the collection
chamber 7 and the piston ring groove 4 and the surface 2b between
the chamber 7 and the piston groove 5 are preferable at least
substantially equal to the height of the opening 16 of the
evacuation channel 15. In this way blow-by gases are prevented from
flowing past the lateral surfaces 2a, 2b between the collection
chamber 7 and the piston ring grooves 4, 5.
[0023] One or more channels 6 in the piston 1 provide, together
with the collection chamber 7, a relatively large space in the
piston 1 for collecting a relatively large volume of blow-by gas
during the operating cycle of the engine 11. By virtue of the size
of the space formed in the piston 1, the pressure of the gases in
this space is reduced and leakage of gas past the second piston
ring 14 minimized.
[0024] Part of the hydrocarbon emission that must be neutralized in
the catalytic converter of a conventional engine is found in the
unburnt air-fuel 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 (referred to as reverse blow-by) when the
pressure in the combustion chamber during the expansion stroke is
less than the pressure in the mixture between the rings. However,
this air-fuel mixture can accumulate and come back to the
combustion chamber too late for burning and contributing to the
output of the engine. With the evacuation channel 15, the unburnt
air-fuel mixture can be evacuated from the chamber 7 and channels 6
before pressure in the combustion chamber is so low that the
mixture can flow past the first piston ring 13 and back into the
combustion chamber. By eliminating reverse blow-by, the quantity of
hydrocarbon emission in the exhaust is reduced. This results in the
size, weight and price of the catalytic converter being reduced,
while also increasing its length of life.
[0025] As can be seen from FIG. 3, the piston may be provided with
a shield 17, which functions as a moving valve element, that
connects the crankcase 18 to the intake channel from the upper dead
center point of the piston 1 to approximately halfway through a
piston stroke. In this manner, the pressure differential between
the crankcase 18 and the intake channel is reduced. Closing the
evacuation channel 15 causes a reduction in the inner cyclical
pressure pulse effect in the crankcase 18, which could otherwise
result in increased oil consumption by transferring suspended oil
to the combustion chamber. The relatively low pressure in the
crankcase 18 at low or medium throttle opening contributes to
reducing the negative effects of these inner pressure pulses,
thereby making it possible to dimension the engine 11 with a
smaller crankcase volume than what has previously been
possible.
[0026] Although the present invention has been described and
illustrated in detail, it is to be clearly understood that the same
is by way of illustration and example only, and is not to be taken
as a limitation. The spirit and scope of the present invention are
to be limited only by the terms of any claims presented
hereafter.
* * * * *