Marine propulsion – Means for accomodating or moving engine fluids – Cooling for engine
Reexamination Certificate
2000-03-30
2001-11-06
Swinehart, Ed (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Cooling for engine
Reexamination Certificate
active
06312300
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a 2-cycle engine and a watercraft having the engine installed therein.
2. Related Art
A conventional 2-cycle engine is operated such that fresh air is sucked into the crank chamber formed by the crank case, and the fresh air is fed into the combustion chamber formed between the cylinder head and the piston through a scavenging passage.
A conventional air-fuel mixture scavenging type sucks only fresh air into the crank chamber. In the air scavenging type, fuel is supplied to the combustion chamber in addition to the fresh air.
Conventional watercraft utilize a jet pump propulsion means driven by a 2-cycle engine as described above. Since a small 2-cycle engine delivers a high output, the engine is particularly useful in a small-sized watercraft.
In the case of the 2-cycle engine, since the fresh air sucked into the crank chamber is fed into the combustion chamber, an increased temperature in the crank chamber (i.e. the crank case) causes the temperature of the fresh air to increase. As the temperature of the fresh air increases, the amount of oxygen per unit volume of the engine is reduced, resulting in reduced combustion efficiency. This reduces the engine output.
Accordingly, a watercraft utilizing a conventional 2-cycle engine does not realize the expected high output from the 2-cycle engine.
It is an object of the present invention to provide a 2-cycle engine and a watercraft having the 2-cycle engine realizing a high engine output.
SUMMARY OF THE INVENTION
In order to attain the above object and other objects not attained by the conventional art, a 2-cycle engine includes a crank case provided with a water jacket for cooling the crank case. The cylinder block is also provided with a water jacket, and the cooling water is supplied to the water jacket of the crank case through a supplying passage separate from another cooling water supplying passage for the water jacket of the cylinder block.
The 2-cycle engine may be an air scavenging type.
The watercraft includes a jet pump propulsion means driven by the engine. Cooling water is supplied from the jet pump to the water jacket.
Since the crank case is provided with the water jacket to cool the crank case, an increase in temperature of the crank case (i.e. the crank chamber) is reduced, which reduces the increase in temperature of the fresh air sucked into the crank chamber.
Since an amount of oxygen of fresh air per unit volume is increased, its combustion efficiency is improved and a high engine output can be attained.
In addition, since the cylinder block is also provided with a water jacket, an increase in temperature of the cylinder block is decreased which further increases engine output.
If the supplying passage for supplying cooling water to the water jacket of the crank case and the supplying passage for supplying cooling water to the water jacket of the cylinder block are formed by a common passage, the water that once cooled the crank case may be supplied to the water jacket of the cylinder block, or, the water that once cooled the cylinder block may be supplied to the water jacket of the crank case, resulting in reduced cooling of the cylinder block and the crank case.
According to the present invention, cooling water may be supplied to the water jacket of the crank case through the supplying passage separate from the cooling water supplying passage for the water jacket of the cylinder block, avoiding the above disadvantage. It thus becomes possible to attain a higher engine output.
Since the 2-cycle engine is an air scavenging type, the fresh air sucked into the crank chamber includes only air, and fuel in addition to the fresh air (air) from the scavenging passage is supplied to the combustion chamber. Accordingly, as compared with that of the air-fuel mixture scavenging type, fuel consumption is reduced.
If the 2-cycle engine of air scavenging type is not cooled, a temperature of the crank chamber is easily increased, decreasing engine output. If both the crank case and the cylinder block are provided with water jackets, fuel consumption is reduced, combustion efficiency is improved, and a high engine output can be attained.
The watercraft according to the present invention can include a jet pump acting as a propulsion means driven by an engine. The 2-cycle engine described can deliver a high output to the jet pump.
In addition, since the cooling water from the jet pump is supplied to the water jacket of the engine, both the crank case and the cylinder block are efficiently cooled.
The jet pump is driven by the engine, so that as the number of rotations of the engine is increased (as the temperature of the engine is increased), a larger amount of cooling water is supplied from the jet pump to each of the water jackets in each of the crank case and the cylinder block through a respective supplying passage (individually). Accordingly, the crank case and the cylinder block are proportionately cooled in response to the rotation of the engine. In addition, it is not necessary to provide a water pump for supplying cooling water to the water jackets.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5109809 (1992-05-01), Fujimoto
patent: 5261356 (1993-11-01), Takahashi et al.
patent: 5752863 (1998-05-01), Baker et al.
patent: 5788547 (1998-08-01), Ozawa et al.
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Swinehart Ed
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