Marine propulsion – Means for accomodating or moving engine fluids – Cooling for engine
Reexamination Certificate
2000-02-08
2001-12-18
Basinger, Sherman (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Cooling for engine
C123S041310
Reexamination Certificate
active
06331127
ABSTRACT:
RELATED APPLICATIONS
This application is based on Japanese Patent Application No. 10-238785, filed Aug. 25, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a marine engine, and more particularly to a cooling system employed in a marine engine.
2. Description of the Related Art
Personal watercraft, like other applications that use internal combustion engines as prime movers, are experiencing considerable public and governmental pressure to improve not only their performance, but also their exhaust emissions level. For example, due to the emissions generated by two-stroke powered watercraft, certain recreational areas have banned the operation of such watercrafts. These bans have decreased the popularity of personal watercraft, and have caused manufacturers of these types of watercraft to consider fuel injected engines to power their watercraft and/or other means to reduce emission levels.
Fuel injected engines are known to provide a significantly enhanced performance, power output, and emissions as compared to carburated engines. All even more significant improvement is achieved through direct cylinder injection. Direct cylinder injection may be accompanied by stratification or lean burning operation to further fuel economy and emission control.
The benefits of fuel injection are further enhanced through the control of the engine block temperature during operation. For example, it has been known to employ a thermostat within the cooling system of a watercraft so as to control the flow of coolant through the cooling system of a watercraft.
SUMMARY OF THE INVENTION
A need therefore exists for a marine engine having a cooling system which can accurately control the temperature of the engine block during operation. Additionally, it is desirable to cool the engine block as well as other components simultaneously, during operation. For example, it is desirable to provide a cooling system for a marine engine which precisely controls the temperature of the engine block during operation, but does not allow the exhaust system to become overheated.
According to one aspect of the present invention, a marine engine for a watercraft includes an engine body defining a combustion chamber and a coolant jacket therein. The watercraft includes an exhaust conduit communicating with the combustion chamber and extending to an exhaust discharge arranged to discharge exhaust gases flowinig through the exhaust conduit to the atmosphere. The exhaust conduit also includes a coolant jacket in thermal communication with at least a portion thereof. The watercraft includes a coolant supply configured to generate pressurized coolant, a cooling system having a first coolant flow path extending from the coolant supply, through the engine coolant jacket and through a temperature dependent flow control valve, and a second coolant flow path extending from at least one of the coolant supply and a portion of the first coolant flow path upstream from the temperature dependent flow control valve.
By providing a first coolant path for supplying coolant to the coolant jacket of the engine body and having a temperature dependent flow control valve, and a second cooling path for supplying coolant to the exhaust conduit coolant jacket, the present aspect of the invention allows the engine body to be controlled to a desired operating temperature while allowing the exhaust system to receive a supply of coolant, independently of the flow of coolant through the temperature dependant flow control valve.
One aspect of the present invention is the realization that when a thermostat is used in a cooling system to maintain a temperature of a component of the engine to a specified range by varying the flow of coolant therethough, other components receiving coolant from the cooling system can be adversely affected by adjustments to the flow rate of the coolant. For example, it has been found that in a watercraft engine that directs coolant flowing out of the engine block coolant jacket through a thermostat, into the exhaust manifold coolant jacket, the fluctuations in the coolant flow rate causes undesirable fluctuations in the temperature of the exhaust system. In fact, it has been found that such exhaust systems have cyclically overheated and cooled under certain operating conditions, due at least in part to the variations in the coolant flow rate caused by the thermostat. Such fluctuations have been found to adversely affect exhaust systems due to the heat cycling. Therefore, by providing the exhaust conduit coolant jacket with a coolant supply path independent from the engine thermostat the present aspect of the invention reduces the effect on the coolant flow rate through the exhaust conduit coolant jacket caused by the thermostat.
Further aspects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiment which follows.
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Basinger Sherman
Knobbe Martens Olson & Bear LLP
Yamaha Hatsudoki Kabushiki Kaisha
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