The invention relates to outboard marine drives, including cooling systems therefor.
Outboard marine drives are known in the prior art and typically include a powerhead having an internal combustion engine, and a downwardly extending driveshaft housing having a lower gearcase driving a propulsor. The engine has a cylinder block and a cylinder head and expels exhaust through an exhaust system having an exhaust manifold, and in some cases a catalyst housing, and an exhaust tube, with the latter extending in the driveshaft housing. A cooling system draws cooling water from a body of water in which the outboard marine drive is operating, and supplies the cooling water through cooling passages to various of the noted components of the outboard marine drive.
The present invention arose during continuing development efforts in the above technology.
Cooling water flows sequentially in the following order through the cooling passages in exhaust tube 106 then catalyst housing 104 then exhaust manifold 102. The cooling water flows to cylinder head 32 after leaving exhaust manifold 102. Exhaust flows sequentially in the following order through exhaust passages in exhaust manifold 102 then catalyst housing 104 then exhaust tube 106 in driveshaft housing 26. The cooling water and the exhaust flow in opposite directions in at least two, and in various embodiments in all three of, the exhaust tube, the catalyst housing, and the exhaust manifold. The sequential direction of flow of cooling water through the exhaust tube, the catalyst housing, and the exhaust manifold is a first sequential direction. The sequential direction of flow of exhaust through the exhaust manifold, the catalyst housing, and the exhaust tube is a second sequential direction. The noted second sequential direction is opposite to the noted first sequential direction.
In one embodiment, a cooling water control valve 110 is coupled to cylinder head 32 and controls the amount of added cooling water flow that the downstream components get over the flow going through the head and the block. In one embodiment, cooling water flow control valve 110 is a valve controlling the flow split between first and second paths, with the first path supplying cooling water through the cylinder head and the cylinder block as shown at arrow 112, and the second path diverting the cooling water as shown at arrow 114 away from the cylinder head and the cylinder block and returning the cooling water as shown at 111 back to the body of water 34 in which the outboard marine drive is operating. In
The system provides a method for preventing condensate formation in the cylinder head, catalyst housing, and exhaust manifold of the internal combustion engine of the powerhead in an outboard marine drive. The method includes providing a cooling system drawing cooling water from the body of water 34 in which the outboard marine drive is operating, and pre-heating the cooling water prior to passing the cooling water through cooling passages in the cylinder head sufficiently to avoid overcooling the exhaust and concomitant condensate formation. A further embodiment includes pre-heating the cooling water prior to passing the cooling water through cooling passages in the catalyst housing sufficiently to avoid overcooling the exhaust and concomitant condensate formation in the catalyst housing. A further embodiment includes pre-heating the cooling water prior to passing the cooling water through cooling passages in the exhaust manifold sufficiently to avoid overcooling the exhaust and concomitant condensate formation in the exhaust manifold. The method includes passing the cooling water through the cooling system in an opposite flow direction to exhaust flowing through the exhaust system in heat transfer relation with the cooling system. The method includes providing the exhaust system with an exhaust manifold, in some embodiments a catalyst housing, and an exhaust tube extending in the driveshaft housing, and passing the cooling water from the body of water 34 through cooling passages in exhaust tube 106, catalyst housing 104, and exhaust manifold 102 prior to passing the cooling water through cooling passages in cylinder head 32 and cylinder block 30. The method includes reducing transient overshoot in cooling water temperature by controlling the amount of pre-heated cooling water passed through the cylinder head. The method includes controlling the amount of pre-heated cooling water passed through the cylinder head by divertingly re-directing some of the pre-heated cooling water as shown at arrow 114 back to the body of water 34 in which the outboard marine drive is operating.
Outboard marine drive engines require special attention when designing a cooling system due to the open-loop nature of the cooling system. An outboard engine with a catalyst requires even more attention to ensure proper operation of the catalyst. It is important to maintain proper heat rejection from the exhaust gas to the cooling water in order to maintain the catalyst material at the appropriate operating temperature. Catalyst material that is too cold will not have optimum chemical conversion or treatment of the exhaust gas. Catalyst material that is too hot may dramatically and unnecessarily degrade the life of the catalyst. In open-loop cooling systems where cooling water from the body of water 34 can range from −2° C. to 38° C. (28° F. to 100° F.). The cooling system used for catalyzed outboard engines must be designed with exhaust gas heat rejection in mind. Further, the additional heat rejected to the cooling water in the exhaust system cooling system must be handled in such a way as to not degrade the transient response of the cooling system. The present system desirably addresses these concerns.
In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different configurations, systems, and method steps described herein may be used alone or in combination with other configurations, systems and method steps. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims. Each limitation in the appended claims is intended to invoke interpretation under 35 U.S.C. §112, sixth paragraph, only if the terms “means for” or “step for” are explicitly recited in the respective limitation.
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Cooling water flow diagram for prior art two-stroke and four-stroke marine engines (undated). This arrangement is hereby admitted prior art, prior to Jun. 11, 2011. |