Marine propulsion – Means for accomodating or moving engine fluids – Cooling for engine
Reexamination Certificate
1999-11-22
2001-10-16
Sotelo, Jesus D. (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Cooling for engine
C440S08900C, C060S323000, C123S1950HC
Reexamination Certificate
active
06302754
ABSTRACT:
PRIORITY INFORMATION
This application is based on and claims priority to Japanese Patent Application Nos. 10-338,279, filed Nov. 20, 1998, the entire contents of which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention principally relates to four-cycle engines for powering. outboard motors. More particularly, the present invention relates to cooling and exhaust systems for such engines associated with outboard motors.
2. Description of the Related Art
Outboard motors are often used to power watercraft. The engines are attached to the back of the watercraft and serve to propel as well as push the watercraft. The engines include powerheads that often extend above a transom of the water. Because the engines are not substantially shielded from the front, the engines can be a large source of wind drag. Accordingly, efforts have been made to decrease the size of the outboard motors while not sacrificing engine performance. One way of decreasing the size of outboard motors employing v-type engines is to decrease the spread of the cylinder banks or to decrease the length of the cylinder banks.
A limitation on narrowing the cylinder banks involves the construction of most exhaust systems. The v-type engines currently used in outboard motors often include an exhaust system that routes the exhaust gases through the powerhead and into the drive shaft housing prior to expelling the gases to either the atmosphere or the body of water in which the watercraft is operating. These exhaust systems often include a pair of exhaust manifolds that separately funnel the exhaust gases from selected cylinders through an exhaust guide plate and into the balance of the exhaust system. The manifolds must be properly sized to allow sufficient exhaust gases to flow through the manifolds such that exhaust gas blow down removes sufficient exhaust gases from the combustion chamber. Accordingly, narrowing the valley between the cylinder banks on v-type engines could adversely affect performance due to the decrease in the exhaust manifold cross section.
Additionally, a seal must be maintained between the cylinder block and the exhaust guide plate to avoid gas leakage. Forming a proper seal, however, proves difficult if the sealed surface area becomes too large. Additionally, the cost of materials increases with the increases in the surface area to be sealed. The increase in materials cost is disadvantageous both upon initial sale as well as while completing repair work.
SUMMARY OF THE INVENTION
Accordingly, an improved exhaust and cooling system is desired whereby the engine size can be reduced without substantially sacrificing performance. In addition, the exhaust system should be designed for an efficient and cost effective manufacture of the outboard motors.
Thus, one aspect of the present invention involves an outboard motor comprising an engine. The engine having a cylinder block and at least one cylinder head with at least one cylinder being defined within the cylinder block. The cylinder block is mounted generally above an exhaust guide. A cylinder head exhaust passage extends from the cylinder through the cylinder head. The exhaust guide includes an exhaust guide passage. The cylinder block includes a cylinder block exhaust passage and the exhaust guide passage and the cylinder head exhaust passage are in communication with each other through the cylinder block exhaust passage.
Another aspect of the present invention involves an outboard motor comprising an internal combustion engine with an exhaust guide plate being positioned generally below the internal combustion engine and including an exhaust guide passage. The internal combustion engine comprises a generally vertically extending crankshaft and a cylinder block having a pair of cylinder banks inclined relative to one another. Each of the pair of cylinder banks includes at least one cylinder. A cylinder head assembly encloses the cylinder. The cylinder head assembly comprises at least one exhaust port and at least one corresponding exhaust runner. The exhaust runner is in selective communication with the exhaust port and is formed between the exhaust port and an exhaust manifold such that the engine includes two exhaust manifolds that extend in generally vertical directions. A pair of connecting exhaust conduits communicates with the exhaust manifolds and extending toward the cylinder block. The cylinder block also has a pair of passages formed therein that are in registry with the connecting exhaust conduits. The passages merge within the cylinder block into an exhaust discharge that is coupled to the exhaust guide passage.
A further aspect of the present invention involves an outboard motor comprising a first cylinder bank and a second cylinder bank. The first cylinder bank and the second cylinder bank are inclined relative to one another and jointly form at least a portion of a cylinder block. A crankcase cover is connected to a portion of the cylinder block and defines a crankcase chamber. A generally vertically extending crankshaft extends through the crankcase chamber between the crankcase cover and the cylinder block. A first cylinder head assembly is attached to the first cylinder bank and a second cylinder head assembly is attached to the second cylinder bank. A first exhaust manifold is connected to the first cylinder head assembly. A second exhaust manifold is connected to the second cylinder head assembly. An exhaust passage is formed in the cylinder block and comprises a first branch, a second branch and a convergent portion that combines the first branch and the second branch. The first and second exhaust manifolds separately communicate with the first and second branches respectively.
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Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
Sotelo Jesus D.
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