Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
1999-06-23
2001-03-27
Morano, S. Joseph (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
Reexamination Certificate
active
06206741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust outlet structure for a personal watercraft. More specifically, the present invention relates to an exhaust outlet structure for discharging the exhaust gas of an engine mounted on the personal watercraft.
2. Description of the Related Art
In general, the personal watercraft is provided with an exhaust outlet for discharging an exhaust gas from an engine at a rear portion of a hull. Some personal watercrafts serve to discharge cooling water of an engine and an exhaust system together with the exhaust gas from an exhaust outlet to a rear outside by a pressure (back pressure) of the exhaust gas. However, the personal watercraft is a vehicle to plane along the water surface. Therefore, the exhaust outlet is positioned on the water surface during running and is sometimes positioned below the water surface at the time of stop. Accordingly, if the exhaust outlet is kept open, there is a possibility that the water might flow from the outside to the inside through the exhaust outlet to cause a counterflow when the engine is stopped so as to prevent the discharge of any exhaust gas.
As shown in the prior art configuration of
FIG. 8
, conventionally, exhaust pipes
51
and
52
constituting exhaust passages in a personal watercraft S and a water muffler
53
for noise elimination have formed a maze. First of all, the water muffler
53
is divided into right and left chambers
53
a
and
53
b
by a bulkhead
54
. A communicating pipe
55
for causing the chambers
53
a
and
53
b
to communicate with each other is provided slightly above the center of the bulkhead
54
. The exhaust pipe
51
connected from an engine E to the water muffler
53
has a rear end
51
a
opened in the vicinity of a central portion of the front chamber
53
a
of the water muffler
53
. The exhaust pipe
52
connected from the water muffler
53
to an exhaust outlet
56
provided in a rear portion of a hull of the watercraft S has a front end
52
a
opened in the vicinity of a central portion of the rear chamber
53
b
of the water muffler
53
. Furthermore, the exhaust pipe
52
extends upward from the front end
52
a
thereof through the water muffler
53
, and is then curved downward and extends rearward. Thus, a countermeasure has been taken such that the water stays in the bottom of the water muffler
53
so as not to cause a counterflow to the engine side even if it flows to the inside through the exhaust outlet
56
when the engine is stopped.
Since the cooling water is mixed in the exhaust gas to perform cooling of the exhaust gas, the water muffler
53
promotes a reduction in exhaust sounds. For this reason, a duplex pipe is usually used as the exhaust pipe
51
reaching the water muffler
53
, and a portion between an outer pipe and inner pipe through which the exhaust gas passes, is formed as a passage for the cooling water. A rear end of the exhaust pipe
51
is opened in the water muffler
53
, and the cooling water is mixed with the exhaust gas. The bulkhead
54
has a small communicating hole
58
such that the cooling water and the exhaust gas can flow into the chambers
53
b
from the chambers
53
a.
When the watercraft S planes, a cavity V is generated on a water surface portion in a rear part of the watercraft S as shown in FIG.
8
. Consequently, reflected sounds of the exhaust gas are made by a water surface F. In some cases, a nonreturn valve (also referred to as a bellows valve)
57
having a simple structure is provided on the exhaust outlet
56
for guiding an exhaust flow to the water surface as shown by an arrow A in order to control the reflected sounds.
In the drawing, the reference numeral
59
denotes a steering handlebar, the reference numeral
60
denotes a seat on which a driver sits, and the reference numeral
61
denotes a fuel tank.
Japanese Unexamined Utility Model Applications Nos. Hei 2-134000 and Hei 5-34100 have disclosed the exhaust outlet of the personal watercraft.
The water muffler
53
forms a part of the exhaust passage, and is greatly concerned with the performance of the engine. Accordingly, it is desirable that the exhaust passage provided in the water muffler
53
should have a shape which is as simple as possible in respect of an enhancement in the output performance of the engine and simplification of a performance test in the engine.
Although the nonreturn valve
57
has some effects of controlling the reflected sounds, sealing against the water on the outside is not sufficiently performed.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, it is an object of the present invention to provide an exhaust outlet structure for a personal watercraft capable of effectively preventing outside water from flowing to the inside through an exhaust port of the personal watercraft and of controlling reflected sounds of an exhaust gas.
The present invention provides an exhaust outlet structure for a personal watercraft which serves to discharge an exhaust gas of an engine mounted on the personal watercraft, the exhaust outlet structure comprising a shut-off member provided on a rear end of an exhaust passage and formed of a flexible material, and an exhaust port formed at the shut-off member, which is capable of being elastically shut off and being opened by external force.
Accordingly, when the exhaust gas is not discharged, for example, the engine is stopped, the water can be prevented from flowing into the exhaust passage from the outside because the exhaust port is shut off by elasticity of a flexible material itself. However, when the engine is operated so that the exhaust gas flows through the exhaust passage, for example, a pressure in the exhaust passage becomes higher than an external pressure (usually, an atmospheric pressure). Therefore, the exhaust port is spread out against the elastic force of the flexible material so that the exhaust gas is discharged. The above-mentioned phrase “external force” includes the force caused by exhaust gas pressure.
The shut-off member protruding from a hull rearward and downward has upper and lower side walls which come in contact with each other, and a portion between the upper and lower side walls forms the exhaust port. Consequently, since the exhaust port is disposed obliquely downward, the reflected sounds can be prevented effectively. The shut-off member is formed of a flexible material. Therefore, the exhaust port can be easily formed in various shapes. In case the exhaust port of the shut-off member is formed adjacent to the water surface, the vicinity of the exhaust port of the shut-off member comes in contact with the water when the watercraft planes, the shut-off member is distorted by force of a water flow, thereby promoting opening of the exhaust port.
In the shut-off member, preferably, the upper side wall is extended more greatly than the lower side wall rearward and downward. Consequently, the upper side wall is pushed rearward by utilizing the water flow. As a result, the exhaust port can be forced open.
Furthermore, the shut-off member may have a film portion capable of shutting off the rear end of the exhaust passage, and the film portion is provided with a plurality of cuts which mutually intersect and constitute the exhaust port. Consequently, the exhaust port can be opened more easily by the internal pressure of the shut-off member.
The shut-off member protruding from a hull rearward and downward may have first and second walls, a portion between the first and second walls forms the exhaust port, and both side walls between the first and second walls reaching the exhaust port are formed to be folded so that the exhaust port closes. Thus, even if an exhaust flow rate is great, the opening area of the exhaust port can be increased correspondingly.
In this case, the first and second walls may be upper and lower side walls or right and left side walls, respectively.
Furthermore, it is preferable that a volume portion, such as a bulge, is formed on the upstream side of the exhaust port in
Kawasaki Jukogyo Kabushiki Kaisha
Marshall O'Toole Gerstein Murray & Borun
Morano S. Joseph
Vasudeva Ajay
LandOfFree
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