Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
2001-01-17
2002-09-24
Basinger, Sherman (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
C060S312000, C060S313000, C060S320000, C060S321000, C060S323000
Reexamination Certificate
active
06454622
ABSTRACT:
PRIORITY INFORMATION
This invention is based on and claims priority to Japanese Patent Applications No. 2000-007571, filed Jan. 17, 2000, No. 2000-192251, filed Jun. 27, 2000 and No. 2000-204839, filed Jul. 6, 2000, the entire contents of which are hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an engine for a watercraft, and particularly to an improved exhaust system of an engine for a watercraft.
2. Description of Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries a rider and possibly one, two or three passengers. A relatively small hull of the personal watercraft commonly defines a riders' area above an engine compartment. An internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The jet propulsion unit is located within the tunnel and is driven by a drive shaft. The drive shaft usually extends between the engine and the jet propulsion device, through a wall of the hull tunnel.
The rider's area usually includes an elongated seat that extends along a longitudinal center line of the watercraft. The seat has a bench-like shape that the rider and passengers can straddle. Foot wells extend along side the seat. The rider and passengers straddle the seat in a tandem fashion with the rider and passengers' legs positioned on the side of the seat and their feet placed within the foot areas.
Generally, the width of the seat not only provides an ample surface upon which the rider and passengers sit, but also provides space in which to locate an upper portion of the engine, including the engine's exhaust and induction systems. U.S. Pat. No. 5,536,189 illustrates an exemplary engine arrangement beneath the seat with the overall width of the seat generally matching the overall width of the engine. The cylinder head, cylinder block, exhaust manifold, exhaust expansion chamber, carburetors, and air intake are all located between the side walls of the seat and beneath the upper cushion of the seat.
While the position of the rider—with his or her feet positioned wide apart and his or her legs straddling the seat—provides good stability, this stance reduces the ability of the rider to absorb with his or her legs impact forces as the watercraft bounds over wakes. In addition, some smaller riders with less height find it uncomfortable to sit in a position with their feet widely spaced apart when straddling the seat.
Additionally, two-cycle engines commonly power personal watercraft, as these engines have the advantage of being fairly powerful and relatively light and compact. One particular disadvantage of a two-cycle engine though, is emissions content. Two-cycle engines exhaust large quantities of carbon monoxide and various hydrocarbons. However, when steps are taken to reduce the emissions content of a two-cycle engine, other generally undesirable consequences result, such as an increase in the weight of the engine, cost of manufacture, and reduction of its power output.
Thus, four-cycle engines have now been proposed as the power plant for personal watercraft. These engines have the advantage of less hydrocarbon emissions than a two-cycle engine while maintaining a relatively high power output. It is therefore desirable to provide a small watercraft with a four-cycle engine in order to reduce exhaust emissions without significantly impacting the power output of the engine that powers the watercraft, or excessively increasing a width of the engine compartment.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an exhaust manifold for an internal combustion engine includes a first exhaust runner assembly having at least two exhaust runners. Each exhaust runner includes an inlet end configured to engage a corresponding exhaust port defined on one side of the engine. The exhaust manifold also includes a second exhaust runner assembly having an inlet end configured to engage at least one exhaust port defined on the side of the engine.
By constructing the exhaust manifold with two exhaust runner assemblies, the manufacture of the exhaust manifold is made easier. In the design and manufacture of exhaust manifold, a difficultly arises in shaping the exhaust runners so as to have approximately the same length. For example, known exhaust manifolds include a plurality of exhaust runners having inlet ends connected to a plurality of exhaust ports arranged in a substantially linear fashion. However, the outlet ends of the exhaust runners merge to define a single outlet passage of the exhaust manifold. Thus, the exhaust runners desirably are shaped differently from each other so as to have approximately the same length.
An exhaust manifold having exhaust runners with varying shapes is difficult to manufacture. In particular, some exhaust manifolds are monolithically cast from metal to improve a heat-resistant characteristic. Thus, an exhaust manifold having more than two exhaust runners with varying shapes is particularly difficult to manufacture. Further, where the exhaust manifold is water-cooled, the varying shapes of the exhaust runners provides an additional difficulty in manufacturing a cooling jacket disposed thermal communication with the exhaust manifold. For example, due to the high heat environment of the exhaust manifold, an outer wall of such a cooling jacket is also made from a cast metal, monolithically formed with the exhaust manifold.
Thus, by constructing the exhaust manifold, in accordance with the present aspect of the invention, with first and second exhaust runner assemblies, the exhaust runners and any associated cooling jackets can be manufactured more easily.
According to yet another aspect of the present invention, a water vehicle includes an internal combustion engine having an engine body and a plurality of exhaust ports defined along a first side of the engine body. The water vehicle also includes an exhaust system having a plurality of individual exhaust passages extending from the exhaust ports, respectively. The individual exhaust passages terminate in the vicinity of a forward end of the engine.
As noted above, known exhaust manifolds typically include a plurality of exhaust runners having inlet ends attached to a corresponding number of exhaust ports defined in a substantially linear fashion on one side of an engine body. The outlet ends of the exhaust runners merge to define a single outlet passage of the exhaust manifold. In order to provide each of the exhaust runners with approximately the same length, the exhaust runners are shaped differently from one another. For example, an exhaust runner communicating with an exhaust port disposed adjacent a longitudinal end of the engine body can be shaped substantially linearly. An exhaust runner communicating with an exhaust port disposed near the middle of the engine body may be curved such that the overall length of the exhaust runners is approximately equal. However, some applications for internal combustion engines cannot provide large amounts of free space adjacent the desired position of the engine body.
For example, in the art of personal watercraft, the rider's seat is typically positioned directly above the engine compartment, with the rider straddling the engine compartment during operation. While the position of the rider—with his or her feet positioned wide apart and his or her legs straddling the sea —provides good stability, this stance reduces the ability of the rider to absorb with his or her legs impact forces as the watercraft bounds over wakes. In addition, some smaller riders with less height find it uncomfortable to sit in a position with their feet widely spaced apart when straddling the seat. Thus, the overall width available for the engine in such a watercraft is limited.
By providing the exhaust system of the water vehicle with a plurali
Mashiko Tetsuya
Takegami Masaki
Basinger Sherman
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
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