Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
2001-04-13
2003-10-14
Swinehart, Ed (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
Reexamination Certificate
active
06632110
ABSTRACT:
This application is based on and claims priority to Japanese Patent Application No. 2000-111549, filed Apr. 13, 2000, the entire contents of which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to marine propulsion engines, such as outboard motors, and the exhaust systems therefor.
2. Description of Related Art
Outboard motors present a number of challenges to the designer. One such challenge is the very compact nature of an outboard motor. An outboard motor generally includes a powerhead that consists of a powering internal combustion engine and a surrounding protective cowling. A drive shaft housing and a lower unit depends from the powerhead. The drive shaft housing and lower unit journals a drive shaft that is driven by the engine. A transmission, which drives a propulsion device in the lower unit, thereby propels an associated watercraft.
One of the prime design considerations and problems in connection with outboard motors is the provision of an adequate exhaust system that permits relatively free breathing, good silencing, and also which ensures that excess heat is not generated and transmitted to other components of the outboard motor. Silencing an outboard motor presents a significant problem in that the length of the exhaust system is substantially limited by the compact nature of the structure. Generally, it has been known to utilize one or more expansion chambers formed in the drive shaft housing and lower unit for assisting in the silencing of the exhaust gases.
It is has also been known in outboard motor construction to discharge the exhaust gases to the atmosphere through the body of water in which the watercraft is operating, at least when the engine is operating at higher engine speeds. By utilizing an underwater exhaust gas discharge, the silencing of the exhaust gases can be augmented.
However, the use of the underwater discharge provides certain problems in that there is a concern that water may be ingested into the engine through the exhaust system. This is a particular problem in connection with two-cycle engines because of the firing impulses and the existence of negative pressures in the exhaust under some circumstances during operation. It has been proposed, therefore, to employ a watertrap arrangement that assists in ensuring against ingestion of water into the engine through the exhaust system.
Additionally, in the interest of obtaining good exhaust emission control, catalysts have been proposed for use in the exhaust system. The catalyst, however, causes additional resistance to the flow of exhaust gases through the exhaust system. Additionally, the catalyst should be protected from water so as to avoid damage. This presents other problems in connection with the location of the related components. It has been proposed also to position the catalyst at an upstream location from the watertrap device so as to ensure protection from water.
For example, with reference to
FIGS. 1 and 2
, an outboard motor
10
which includes a known exhaust system
12
is shown therein. As is typical with outboard motor practice, the outboard motor
10
includes a powerhead portion
14
with a drive shaft housing and lower unit portion
16
which depends from the powerhead
14
.
The powerhead
14
includes an internal combustion engine
18
. The engine
18
is surrounded by a protective cowling, which includes an upper cowling portion (not shown) and a lower tray portion
20
.
The engine
18
is mounted in the outboard motor
10
such that its crankshaft
22
rotates about a vertically-extending axis. The crankshaft
22
drives a drive shaft
24
which is journaled within the drive shaft housing and lower unit portion
16
.
The drive shaft
24
depends into the lower unit portion where it drives a propeller
26
via a conventional bevel gear reversing transmission
28
. The propeller
26
is affixed to a propeller shaft
30
which is driven by the transmission
28
. As such, as the drive shaft rotates and drives the transmission
28
, the propeller
26
rotates to thereby propel an associated watercraft through the body of water in which it operates.
The drive shaft housing and lower unit
16
includes an upper case portion
32
which is generally open at its upper end. This open upper end is closed by an exhaust guideplate
34
which also supports the engine
18
.
A pair of damper members
36
support the exhaust guideplate
34
and the upper case
32
, respectively, relative to a steering or “swivel” shaft
38
. The steering shaft is supported by a bracket assembly
40
which, in turn, is connected to the transom of an associated watercraft in a known manner.
The exhaust system
12
of the engine
18
includes an exhaust manifold (not shown) which defines at least a portion of a main exhaust passage that extends from the combustion chambers of the engine
18
into an expansion chamber
42
. The main exhaust passage extends through the exhaust guideplate
34
and through an outlet end
44
thereof. The expansion chamber
42
aids in quieting the noises traveling through the main exhaust passage along with the exhaust gases.
The exhaust system
12
also includes a catalyst device
46
disposed in an outlet
48
of the expansion chamber
42
. The catalyst device
46
is positioned in the outlet
48
such that substantially all of the exhaust gases flowing into the outlet
48
from the expansion chamber
42
passes through the catalyst device
46
. The outlet
48
of the expansion chamber
42
extends through the exhaust guideplate
34
into an upper or a “riser” exhaust passage
50
.
With reference to
FIG. 2
, the riser portion
50
has a generally inverted U-shape. An outlet end
52
of the riser portion
50
connects to a further exhaust passage
54
which extends through the exhaust guideplate
34
. An additional exhaust pipe
56
is connected to the exhaust passage
54
and extends downwardly through the upper case
32
toward the lower case
33
.
With reference to
FIG. 1
, the lower case
33
includes a passage
58
which connects the exhaust pipe
56
with an exhaust discharge
60
which is positioned within the propeller
26
.
Additionally, at least a portion of the exhaust system
12
is cooled by water drawn from the body of water in which the outboard motor
10
is operating. For example, the riser section
50
includes a cooling jacket
62
. Additionally, the outboard motor
10
includes a temperature sensor
64
for sensing a temperature of the coolant flowing through the cooling jacket
62
. The outboard motor
10
can also include an oxygen sensor
66
which includes an inner end exposed to the exhaust gases flowing through the riser pipe
50
. The output from the oxygen sensor can be used to control an engine operating parameter such as those relating to fuel injection duration and timing and/or ignition timing.
In operation, exhaust gases generated in the combustion chambers within the engine
18
are directed downwardly by the main exhaust passage into the outlet end
44
. Exhaust gases from the outlet end
44
flow into the expansion chamber
42
which thereby attenuates some of the noise associated with the exhaust gases.
All of the exhaust gases from the expansion chamber
42
flow through the catalyst device
46
and upwardly into the riser pipe
50
. With reference to
FIG. 2
, exhaust gases flow upwardly into the riser portion
50
and laterally toward the port side of the outboard motor
10
, then downwardly into the exhaust pipe
56
. As shown in
FIG. 1
, exhaust gases from the exhaust pipe
56
flow into the exhaust passage
58
formed in the lower unit housing
33
and through the discharge
60
formed on the propeller
26
. Thus, exhaust gases are further quieted by being discharged below the water surface level of the body of water in which the outboard motor
10
is being operated. Additionally, by directing the exhaust gases upwardly into the riser portion that is disposed above the exhaust guideplate
34
, the riser portion
50
forms a watertrap whic
Knobbe Martens Olson & Bear LLP
Swinehart Ed
Yamaha Marine Kabushiki Kaisha
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