Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
2000-03-10
2001-02-13
Avila, Stephen (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
Reexamination Certificate
active
06186846
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust passage structure for an outboard motor.
2. Description of the Related Art Among engines for outboard motors, there is one that has a cylinder block comprising a plurality of cylinders arranged vertically. A cylinder head joined with the cylinder block has an intake port and an exhaust port being formed for each of the cylinders. Exhaust gas from each exhaust port is collected into a common exhaust passage, and is discharged out of the outboard motor.
A conventional means for collecting the exhaust gas discharged from each of the exhaust ports, for example, is disclosed in Japanese Laid-open Patent Publication No. Hei-6-16187, wherein the exhaust passages communicating to the exhaust ports in the cylinder head are formed integrally in the cylinder block. Another typical means for collecting exhaust gas discharged from respective exhaust ports is disclosed in Japanese Laid-open Utility Model Application No. Hei-4-134626, wherein a separate exhaust manifold is disposed between a cylinder head and an oil pan having exhaust passages formed therein.
However, forming the exhaust passages integrally in the cylinder block increases the size and weight of the cylinder block, and makes the configuration more complicated, thus leading to higher manufacturing cost. Also, since the exhaust passages are formed in greater proximity to the cylinder, the cylinder may be subjected to thermal deformation due to exhaust heat which should be avoided. Moreover, since the cylinder and the exhaust passage use a common coolant water jacket, it is impossible to control the temperature of the exhaust passage independently, thus resulting in lower cooling efficiency of the exhaust passage.
Although these problems may be solved by using an exhaust manifold, it is difficult to control the accuracy of assembly unless the top end and bottom end of the exhaust manifold lie on the same plane. Consequently, there may occur such undesirable effects as a lower yield in the machining processes.
In the case of a four-cylinder engine, for example, exhaust passages are arranged in such an order in the exhaust manifold where cylinder No.
1
may be at the top, followed by No.
2
, No.
3
, and No.
4
, downward, while combustion in a four-cycle, four-cylinder engine generally occurs in the order of cylinder No.
1
, No.
3
, No.
4
, and No.
2
. As a result, exhaust emission interference occurs when the exhaust passages from cylinders No.
3
and No.
4
, where combustion occurs consecutively are disposed adjacent to each other, and the exhaust passages from cylinders No.
2
and No.
1
, where combustion occurs consecutively are disposed adjacent to each other, thus giving rise to a possibility of lowering engine performance.
Although these problems, for example, may be solved by a method extending the exhaust passages to below the engine and joining them at this position as disclosed in Japanese Laid-open Patent Publication No. Hei-9-49425, this makes the exhaust passages too long, resulting in a large size of the engine. Also the number of component parts increases and the construction becomes complex, while making it difficult to form the coolant water jacket and the coolant water passage.
SUMMARY OF THE INVENTION
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
The present invention is made in consideration of the above-mentioned problems, and an exemplary object thereof is to provide an exhaust passage structure for an outboard motor that makes it possible to prevent exhaust emission interference from occurring with a simple configuration without increasing the engine size.
Another exemplary object of the present invention is to provide an exhaust passage structure for an outboard motor that simplifies the configuration of component parts of the engine and of the exhaust manifold, while improving the productivity of these component parts.
A further exemplary object of the present invention is to provide an exhaust passage structure for an outboard motor that improves the cooling performance of the exhaust passages.
In order to solve the problems described above, an embodiment of the present invention provides an exhaust passage structure for an outboard motor that is equipped with an engine having a cylinder block comprising a plurality of cylinders arranged in parallel to each other, with an exhaust port for each of the cylinders being formed in a cylinder head that is joined with the cylinder block, wherein exhaust passages are formed in an exhaust manifold for connecting the exhaust ports and an exhaust discharge path formed on the outboard motor side, while all the exhaust passages are joined after separating joining the exhaust passages from the cylinders where combustion takes place in odd-numbered cycles and the exhaust passages from the cylinders where combustion takes place in even-numbered cycles, with the exhaust passages that are joined separately being disposed in parallel to each other in the longitudinal direction of the outboard motor.
To further solve the problems described above, one exemplary embodiment of the present invention includes joining all of the exhaust passages in the exhaust manifold before the exhaust discharge path.
Moreover, another embodiment of the present invention includes providing the exhaust manifold separately from the cylinder block and the cylinder head.
Yet another embodiment of the present invention includes a joining surface of the exhaust manifold with the engine is formed in a single plane.
A further embodiment of the present invention includes a water inlet provided in the outboard motor with such a configuration so that coolant water for cooling the exhaust passages of the exhaust manifold is introduced through a point midway in a coolant water passage running from the water inlet to the engine.
The above and other objects, features and advantages of the present invention will become apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4914911 (1990-04-01), Bertram
patent: 4965997 (1990-10-01), Suzuki et al.
patent: 5134851 (1992-08-01), Davis
patent: 5494467 (1996-02-01), Sohgawa et al.
patent: 5803036 (1998-09-01), Takahashi et al.
patent: 4-134626 (1992-12-01), None
patent: 06016187 (1994-01-01), None
Avila Stephen
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Suzuki Motor Corporation
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