1. Field of the Invention
The present invention is generally related to a cooling system for a marine propulsion engine and, more specifically, to a cooling system which incorporates a pressure responsive valve in a first cooling system and a temperature responsive valve in a second cooling system, wherein the first and second cooling systems are connected in parallel with each other.
2. Description of the Related Art
Many different types of engine cooling systems are known to those skilled in the art. More specifically, many different types of cooling systems for marine engines are known.
U.S. Pat. No. 5,769,038, which issued to Takahashi et al. on Jun. 23, 1998, describes a liquid cooling system for an engine. The liquid cooling arrangement for an internal combustion engine has a cylinder block with a cylinder head connected thereto and defines at least one combustion chamber, a common exhaust passage extending through the cylinder block, and an exhaust passage leading from each combustion chamber to the common exhaust passage. The liquid cooling arrangement includes a pump for pumping cooling liquid from a cooling liquid source first through at least one passage extending through the cylinder head generally adjacent the exhaust passages leading from the combustion chambers, and through at least one passage extending through the cylinder block generally adjacent the common exhaust passage. Once the cooling liquid has passed through these passages, the cooling liquid is delivered to one or more passages extending through the cylinder head or block generally adjacent to combustion chambers. The cooling liquid then selectively passes a thermostat into a cooling liquid return line through which the cooling liquid is drained from the engine.
U.S. Pat. No. 5,904,605, which issued to Kawasaki et al. on May 18, 1999, describes a cooling apparatus for an outboard motor. The outboard motor is provided with a water cooling engine in a vertical alignment. A crankshaft is vertically disposed. The engine comprises a cylinder block, a cylinder head and an exhaust manifold into which water jackets are formed respectively and the water jackets are supplied with cooling water from a water pump disposed below the engine in a state mounted to a hull. The cooling apparatus comprises a cylinder cooling water passage for supplying cooling water from the water pump to the water jackets of the cylinder block and the cylinder head, an exhaust cooling water passage for supplying cooling water from the water pump to the water jacket of the exhaust manifold, the cylinder cooling water passage and the exhaust cooling water passage being independently disposed from each other and being joined together at downstream portions thereof. A thermostat is provided for the water jacket of the cylinder block and a sensor for detecting the temperature of a cylinder surface is provided for the water jacket of the cylinder block at a portion between the water jacket thereof and the thermostat.
U.S. Pat. No. 5,937,802, which issued to Bethel et al. on Aug. 17, 1999, discloses an engine cooling system for an internal combustion engine. It is provided with coolant paths through the cylinder block and cylinder head which are connected in serial fluid communication with each other. In parallel with the cooling path through the cylinder head, a first drain is connected in serial fluid communication with a pressure responsive valve and the path through the cylinder block. A temperature responsive valve is connected in serial fluid communication with the cylinder head path and in parallel fluid communication with the first drain. A pump is provided to induce fluid flow through the first and second coolant conduits and the first and second drains, depending on the status of the pressure responsive valve and the temperature responsive valve.
U.S. Pat. No. 5,937,801, which issued to Davis on Aug. 17, 1999, discloses an oil temperature moderator for an internal combustion engine. A cooling system is provided for an outboard motor or other marine propulsion system which causes cooling water to flow in intimate thermal communication with the oil pan of the engine by providing a controlled volume of cooling water at the downstream portion of the water path. As cooling water flows from the outlet of the internal combustion engine, it is caused to pass in thermal communication with the oil pan. Certain embodiments also provide a pressure activated valve which restricts the flow from the outlet of the internal combustion engine to the space near the oil pan. One embodiment of the cooling system also provides a dam within the space adjacent to the outer surface of the oil pan to divide that space into first and second portions. The dam further slows the flow of water as it passes in thermal communication with the oil pan.
U.S. Pat. No. 5,970,926, which issued to Tsunoda et al. on Oct. 26, 1999, describes an engine cooling system for an outboard motor. An engine includes first exhaust passages formed in a cylinder head, a second exhaust passage formed in a cylinder block and communicating with the first exhaust passages, and a cooling water passage having water jacket portions formed around the combustion chambers. The cooling water passage includes a first water jacket and a second water jacket. The cylinder head and the cylinder block are fixedly connected together by bolts. The second exhaust passage opens at a joining surface of the cylinder block along cylinders, which opening is surrounded by the bolts.
U.S. Pat. No. 6,135,833, which issued to Tsunoda on Oct. 24, 2000, describes an engine cooling system for an outboard engine. The system includes a thermostat mounted on an upper surface of a cylinder block to open and close a cooling water passage depending on the temperature of cooling water inside the cooling water passage and a relief valve mounted on the upper portion of the side wall of the cylinder block and located adjacent to the thermostat to open and close the cooling water passage depending on the pressure of cooling water inside the cooling water passage.
U.S. Pat. No. 6,331,127, which issued to Suzuki on Dec. 18, 2001, describes a marine engine for a watercraft. It includes a cooling system having a coolant supply. The coolant supply supplies an engine coolant jacket with a flow of coolant that is controlled by a temperature dependent flow control valve. The coolant supply also supplies an exhaust conduit coolant jacket independently of the engine coolant jacket.
U.S. Pat. No. 6,394,057, which issued to Fukuoka et al. on May 28, 2002, describes an arrangement of components for an engine. An exhaust system of the engine has an exhaust manifold extending along a cylinder body. At least a part of the air induction system of the engine exists to overlap with the exhaust manifold in a view along an extending axis of the exhaust manifold. A cooling system having at least two coolant passages is further provided. A coolant flow control mechanism is arranged to prevent only the coolant within one of the passages from flowing therethrough when temperature of the coolant is lower than a predetermined temperature.
U.S. Pat. No. 6,682,380, which issued to Irwin et al. on Jan. 27, 2004, describes a marine engine cooling system. The cooling system includes cylinder cooling jackets, cylinder head cooling jackets and thermostatic and pressure controls which facilitate safely operating the engine with low water flow rates.
U.S. Pat. No. 6,821,171, which issued to Wynveen et al. on Nov. 23, 2004, discloses a cooling system for a four cycle outboard engine. The system conducts water from a coolant pump through a cylinder head and exhaust conduit prior to conducting the cooling water through the cylinder block. This raises the temperature of the water prior to its entering the cooling passages of the cylinder block.
U.S. Pat. No. 6,561,140, which issued to Nagashima on May 13, 2003, describes a water cooling system for an engine. A housing unit defines a water delivery passage and a water discharge passage. Both the passages communicate with each other through a lower opening. The water delivery passage is arranged to deliver cooling water to the engine. The water discharge passage is arranged to discharge the cooling water from the engine. The discharge passage communicates with a location out of the housing unit through an upper opening. A pressure relief valve unit extends through the lower and upper openings. The pressure relief valve unit allows the cooling water in the delivery passage to move to the discharge passage when a pressure of the delivery passage becomes greater than a preset pressure.
U.S. patent application Ser. No. 10/674,815, which was filed by Tawa et al. on Oct. 1, 2003, describes a water cooled vertical engine and an outboard motor equipped therewith. Provided in a chain cover are thermostats for controlling the flow of cooling water in a cylinder block cooling water jacket and cylinder head cooling water jacket. Therefore, the thermostats can be accessed from the top of the engine for maintenance without being obstructed by the timing chain, and moreover it is easy to manipulate a drain pipe for discharging cooling water from the thermostats.
U.S. patent application Ser. No. 10/674,813, which was filed by Tawa et al. on Oct. 1, 2003, describes a water cooled vertical engine and an outboard motor equipped therewith. The engine includes an exhaust guide cooling water jacket and an exhaust manifold cooling water jacket which are formed in an engine compartment. A cylinder block cooling water jacket is formed in a cylinder block. A cylinder head cooling water jacket is formed in a cylinder head. Cooling water from a cooling water pump is supplied in parallel to an upper part and lower part of the cylinder block cooling water jacket through the exhaust guide cooling water jacket and the exhaust manifold cooling water jacket.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be beneficial if a cooling system for a marine engine could be provided in which different cooling circuits of the cooling system could be individually temperature controlled so that they are not all dependent on a common thermostat. This would allow certain heat emitting portions of the engine to be cooled more rapidly under certain dynamic conditions even though other portions of the engine, and their respective cooling circuits, experience more slowly rising coolant temperatures.