Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Reexamination Certificate
1997-05-30
2001-05-15
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
Reexamination Certificate
active
06230672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a two-cycle internal combustion engine capable of preventing a blow-by phenomenon of a mixture in a combustion chamber thereby improving fuel economy and attaining better exhaust gas purifying performance.
2. Description of Background Art
In a related art, fuel supplied by a carburetor to a two-cycle internal combustion engine is mixed with intake air and the resulting mixture is sucked into a crank chamber and is then supplied into a combustion chamber through a scavenging port. In this case, since the timing of the opening an exhaust port is set earlier than that of the scavenging port (an upper edge of the exhaust port is higher than that of the scavenging port), the mixture fed into the combustion chamber is discharged into an exhaust passage, thus easily causing a so-called blow-by phenomenon.
Although the blow-by phenomenon is suppressed by an exhaust pulsating effect in an exhaust chamber, it is difficult for the suppression to cover the whole operation range, resulting in that both the fuel economy and exhaust purifying performance are affected.
In an effort to solve the above-mentioned problem, two-cycle internal combustion engines have been proposed in Japanese Patent Laid-open Nos. Hei 3-100318 and Hei 5-302521.
In the two-cycle internal combustion engine disclosed in Japanese Patent Laid-open No. Hei 3-100318, a high pressure chamber is connected to a crank chamber through a check valve, the high pressure chamber is connected to the combustion chamber through an air passage, a solenoid valve is disposed in the lower end of the air passage, and a fuel injection valve capable of injecting fuel towards the combustion chamber is provided at the upper end of the air passage.
In the two-cycle internal combustion engine disclosed in Japanese Patent Laid-open No. Hei 5-302521, a chamber is formed in a position adjacent to both the crankcase and the cylinder block, an intake control valve is interposed between a crank chamber and said chamber, a scavenging control valve is interposed between said chamber and a combustion chamber in a cylinder, and a fuel injection valve is provided for injection of fuel toward said chamber.
In the two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 3-100318, with respect to the fuel injected from the fuel injection valve, part of the fuel deposited in the air passage falls by gravity, entering the crank chamber through a check valve disposed at the bottom of the air passage, and flows in a state wherein the fuel is atomized into the combustion chamber from the crank chamber through another scavenging port. As a result, it is difficult to sufficiently prevent the blow-by phenomenon and to obtain a stable combustion. Further, it is difficult to suitably control the amount of fuel fed into the combustion chamber, resulting in degraded responsiveness.
In the two-cycle internal combustion engine described in Japanese Patent Laid-open No. Hei 5-302521, all of the intake air in the crank chamber is introduced through the intake control valve and is mixed with the fuel introduced into the chamber through the fuel injection valve. The resulting mixture flows into the combustion chamber through the scavenging control valve. Accordingly, the two-cycle internal combustion engine is not configured so as to permit only air to flow from the crank chamber into the combustion chamber through a scavenging port, and hence the blow-by phenomenon is unavoidable. Further, although an upstream side of the scavenging control valve is opened to the lower portion of said chamber, the opening position thereof is not the lowest, so that the fuel injected into said chamber remains at the bottom of said chamber, thus giving rise to a problem that the amount of fuel fed into the combustion chamber cannot be accurately proportional to the amount of fuel injected from the fuel injection valve, resulting in degraded responsiveness.
SUMMARY AND OBJECTS OF THE INVENTION
To provide an improved two-cycle internal combustion engine capable of solving the above-described problems, the present invention has been made wherein a two-cycle internal combustion engine is provided in which a control valve for operably controlling a communication passage which communicates a combustion chamber to a chamber contiguous to a fuel injection device is disposed in the communication passage and fuel is fed into said combustion chamber via said communication passage. The chamber contiguous to said fuel injection device is juxtaposed on a side of said combustion chamber and at least a control portion of said control valve is positioned lower than a communicating portion through which said communication passage is communicated to said chamber contiguous to said fuel injection device.
In the present invention, fuel is supplied into the combustion chamber through the communication passage, so that at the scavenging stroke, a burned gas in the combustion chamber can be positively discharged from the exhaust port by introducing air not mixed with fuel into the combustion chamber through the scavenging passage. As a result, it is possible to prevent blow-by of the mixture in the combustion chamber and to improve a scavenging efficiency due to air scavenging upon low load running.
Since at least the control portion of the control valve is positioned lower than the communicating portion at which the communication passage is communicated to the chamber contiguous to the fuel injection device, even if the fuel supplied from the fuel injection device into said chamber remains at a bottom portion of said chamber and/or at lower portions of both the communication passage communicated to said chamber and the control valve, the remaining fuel can be almost positively discharged into the combustion chamber. As a result, it is possible to suitably, responsively control the amount of the fuel supplied into the combustion chamber and hence to obtain a stable combustion state.
Further, since the chamber contiguous to the fuel injection device is juxtaposed on a side of the combustion chamber, the entire engine can be compactly formed into a substantially square shape in a side view, and thereby the vertical length of the entire engine can be shortened as compared with the case where said chamber is disposed over the combustion chamber. As a result, in the case of mounting the engine on a vehicle, it is possible to increase the degree of freedom in layout, and particularly, in the case of mounting the engine on a motorcycle, it is possible to eliminate an inconvenience in which the vehicular height and the minimum ground clearance become higher.
According to the present invention, the fuel supplied into the combustion chamber scavenges the remaining burned gas without occurrence of the blow-by thereof, with a result that the fuel can be positively fed into the combustion chamber.
According to the present invention, it is possible to easily control opening/closing of the control valve in synchronization with rotation of the crank shaft of the engine.
According to the present invention, a relatively small amount of air to be mixed with fuel supplied to the combustion chamber through the communication passage between the combustion chamber and the chamber contiguous to the fuel injection device can be positively sucked in said chamber, and also a pressure sufficient to feed the mixture into the combustion chamber through the communication passage can be obtained.
Further, the mixture becomes rich and the resulting rich mixture flows into the combustion chamber which has been sufficiently scavenged by the air (not mixed with fuel) passing another scavenging passage, so that it is possible to suitably adjust the concentration of the mixture in the combustion chamber and hence to obtain a desirable combustion state. This makes it possible to improve fuel economy and attain a high exhaust gas purifying performance.
In addition, at the beginning of scavenging, the valves (gate valve and control valve) at th
Asai Masahiro
Ishibashi Yoichi
Isomura Shinichi
Nishida Kenji
Noritake Hideki
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
McMahon Marguerite
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