Internal-combustion engines – Two-cycle – Rear compression
Reexamination Certificate
1999-12-10
2001-09-18
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Two-cycle
Rear compression
Reexamination Certificate
active
06289856
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a stratified scavenging two-cycle engine, and particularly relates to a stratified scavenging two-cycle engine which is configured to take in a mixture and scavenging air separately.
BACKGROUND ART
This type of stratified scavenging two-cycle engine conventionally has a scavenging flow passage for connecting a cylinder chamber to a crank chamber; with a mixture flow passage, for supplying a fuel mixture, being connected to the crank chamber; and with an air flow passage, for supplying air, being connected to the scavenging flow passage. A scavenging port of the scavenging flow passage, and an exhaust port of an exhaust pipe are opened to the cylinder chamber. The aforesaid air flow passage is provided with a lead valve (a check valve)
80
, shown in
FIG. 12
, for only allowing the air to flow toward the scavenging flow passage.
In the stratified scavenging two-cycle engine configured as above, a piston
3
ascends, thereby starting to reduce the pressure inside a crank chamber
20
and to increase the pressure inside the cylinder chamber
10
; and as the piston
3
ascends, a scavenging port
81
and an exhaust port are sequentially closed. In this situation, a mixture flows into the crank chamber
20
with the pressure therein being reduced, and air from an air flow passage
83
pushes the lead valve
80
open to flow therein through a scavenging flow passage
85
.
When the piston
3
reaches the vicinity of the top dead center, the mixture in the cylinder chamber
10
is ignited, and thereafter the piston
3
descends. The piston
3
descends, thereby starting to increase the pressure inside the crank chamber
20
; and while the piston
3
is descending, the exhaust port and the scavenging port
81
are sequentially opened, and combustion gas is exhausted via the exhaust port. Subsequently, when the scavenging port
81
is opened, the air remaining in the scavenging flow passage
85
bursts out into the cylinder chamber
10
due to the pressure inside the crank chamber
20
. As a result, the combustion gas remaining in the cylinder chamber
10
is expelled. Subsequently, the mixture in the crank chamber
20
is charged into the cylinder chamber
10
through the scavenging flow passage
85
. Again, when the piston
3
starts to ascend from the bottom dead center, the pressure inside the crank chamber
20
starts to reduce, and the cycle as described above is repeated once again.
According to the stratified scavenging two-cycle engine configured as above, the inside of the cylinder chamber
10
can be initially scavenged by air, thereby making it possible to prevent the combustible gas from being discharged by the blow-by of the mixture, which provides the advantage that the exhaust gas becomes clean.
However, in the aforesaid stratified scavenging two-cycle engine, as shown in
FIG. 12
, the air flowing into the scavenging flow passage
85
from the lead valve
80
does not flow into a space
81
A in the vicinity of the scavenging port
81
, and therefore mixture remains in this space. There exists a disadvantage in that the mixture, together with the air remaining in the scavenging flow passage
85
, is discharged from the exhaust port into the atmosphere with the combustion gas via the cylinder chamber
10
when the scavenging port
81
opens in the exhaust stroke in which the piston
3
descends. In addition, the lead valve
80
is provided in the air flow passage
83
, thereby causing a disadvantage in that the lead valve
80
becomes intake resistance when air is taken into the scavenging flow passage
85
. Further, the number of components is increased due to the lead valve
80
, and the structure is complicated, thus causing the disadvantage of increased costs.
SUMMARY OF THE INVENTION
The present invention is made in view of the aforesaid disadvantages, and its object is to provide a stratified scavenging two-cycle engine, which takes in a fuel mixture and scavenging air separately, is capable of doing away with emission of the mixture into the atmosphere by filling a scavenging flow passage with air and reducing intake resistance of air, and is less expensive with the number of components being reduced.
In order to attain the above object, a stratified scavenging two-cycle engine according to the present invention is a stratified scavenging two-cycle engine including an air intake port, scavenging ports, and an exhaust port which are connected to a cylindrical chamber of the engine; a mixture intake port which is connected to a crank chamber; and scavenging flow passages for connecting the cylinder chamber to the crank chamber; and is characterized in that the air intake port is provided at a position which is a predetermined distance away from the scavenging ports toward the crank chamber parallel to axial direction of the cylindrical chamber, and the scavenging ports are connected to the air intake port via the piston to thereby supply air to the scavenging flow passages from the air intake port through the scavenging ports at the time of an intake stroke.
According to the above configuration, the air intake port and the mixture intake port are separately connected to the cylinder chamber and the crank chamber, respectively, and air is supplied to the scavenging flow passages for connecting the cylinder chamber to the crank chamber via the piston, thereby making it possible to fill at least the cylinder chamber side of the scavenging flow passage with air at the time of an intake stroke. In addition, since the air intake port is opened at a lower position which is the predetermined distance away from the scavenging ports toward the crank chamber, when the top portion of the piston opens the scavenging ports at the time of a scavenging stroke, the air intake port is already closed, and therefore neither air nor the mixture flows back to the air flow passage, thus making a lead valve unnecessary.
Accordingly, in the scavenging stroke, the combustion gas can be initially scavenged from the cylinder chamber by means of the air in the scavenging flow passage, and thus the mixture does not flow into the atmosphere. Further, the lead valve for taking air into the scavenging flow passage is not needed, thereby making it possible to reduce the intake resistance of air and the number of components.
Further, the stratified scavenging two-cycle engine can be characterized in that the piston has a channel on the outer perimeter thereof, and the channel connects the scavenging ports to the air intake port and disconnects the mixture intake port from the scavenging ports, at the time of intake stroke.
According to the above configuration, in the intake stroke, since the mixture intake port is disconnected from the scavenging ports, the mixture does not stay in the scavenging flow passages, thus making it possible to fill the scavenging flow passages with air.
Accordingly, in the intake stroke, the combustion gas in the cylinder chamber can be scavenged by means of the air in the scavenging flow passages, and thus the mixture does not leak into the atmosphere.
Furthermore, the stratified scavenging two-cycle engine can be characterized in that the mixture intake port can be opened and closed by the piston.
According to the above configuration, in the scavenging stroke, when the top portion of the piston opens the scavenging ports, the mixture intake port is already closed, whereby the mixture does not flow back to the mixture flow passage, and thus the lead valve can be made unnecessary.
In addition, since the lead valve for supplying the mixture to the crank chamber is not needed, the number of components can be reduced.
REFERENCES:
patent: 4711201 (1987-12-01), Ooyama et al.
patent: 4809648 (1989-03-01), Luo
patent: 4829940 (1989-05-01), Okazaki et al.
patent: 4995349 (1991-02-01), Tuckey
patent: 5189995 (1993-03-01), Hooper
patent: 5379732 (1995-01-01), Mavinahally et al.
patent: 5628295 (1997-05-01), Todero et al.
patent: 5857450 (1999-01-01), Staerzl
patent: 6079379 (2000-06-01), Cobb, Jr.
patent: 6101991 (2000-08-01), Glov
Huynh Hai
Kamen Noah P.
Komatsu Zenoah & Co.
Sidley Austin Brown & Wood
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