Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
2000-05-30
2001-10-02
Morano, S. Joseph (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
C440S08800J
Reexamination Certificate
active
06296537
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an outboard motor particularly provided with an improved exhaust structure.
Engines of outboard motors include an engine, generally of water-cooling type, having a cylinder block in which a plurality of cylinders are arranged in a vertical direction. In a cylinder head connected to the cylinder block, intake ports and exhaust ports are formed for the respective cylinders. Exhaust gas discharged from the exhaust ports is collected into a common exhaust passage and then discharged from the outboard motor.
Since the exhaust passage is heated to a very high temperature by the exhaust gas, a cooling water passage is formed around the exhaust passage to cool the exhaust passage by means of cooling water. Such a cooling water passage is provided for members of the engine, such as cylinder block, an engine holder and an oil pan.
However, in a conventional structure of the outboard motor, in some cases, the exhaust gas is not sufficiently cooled even by the location of a cooling water passage to a member (or members) such as cylinder block, engine holder and oil pan through which an exhaust passage passes. When the exhaust gas having a high temperature from the engine is discharged from the discharge passage into the drive shaft housing, an outer wall of the drive shaft housing is heated by the exhaust gas and a temperature thereof is increased and, hence, calcium contained in a sea water, for example, pumped up as cooling water may adhere to the outer wall of the drive shaft housing, thus being inconvenient.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defect or drawback encountered in the prior art mentioned above and to provide an outboard motor having an improved exhaust structure capable of improving cooling efficiency of an exhaust gas.
This and other objects can be achieved according to the present invention by providing an outboard motor comprising:
an engine holder;
an engine disposed above the engine holder in a state of the outboard motor being mounted to a hull;
an oil pan disposed below the engine holder;
a drive shaft housing disposed below the oil pan;
an exhaust passage means formed in the engine, the engine holder and the oil pan and adapted to exhaust an exhaust gas from the engine into the drive shaft housing, the exhaust passage means having a downstream side end opening; and
an exhaust tube provided for a bottom surface portion of the oil pan so as to align with the downstream side end opening of the exhaust passage means, the exhaust tube having a downstream side outlet positioned, in a plan view, at a substantially central portion of the drive shaft housing.
In a preferred embodiment, the exhaust passage means comprises a plurality of exhaust passages including a passage formed to the oil pan which has the downstream side end opening aligned with the exhaust tube.
The outboard motor may further comprises a water pump disposed to a bottom portion of the drive shaft housing for pumping up a cooling water and a cooling water passage means formed in the engine holder and the oil pan, and the cooling water pumped up by the water pump is guided to the engine through the cooling water passage means and the cooling water passage means includes a cooling water passage formed in the oil pan, a relief valve is provided for the cooling water passage and the exhaust tube is disposed in a vicinity of the relief valve. The cooling water passage means comprises a plurality of cooling water passages including a horizontal passage formed to a bottom portion of the oil pan for which the relief valve is provided. The outboard motor may further comprises a cooling water discharge passage means formed in the engine holder and the oil pan for discharging the cooling water after cooling the engine inside the drive shaft housing and a return water guide formed integrally with the exhaust tube, the cooling water discharge passage means having a downstream side end opening with which the return water guide is aligned. The cooling water discharge passage means comprises a plurality of cooling water discharge passages including a passage formed to the oil pan which has the downstream side end opening with which the return water guide is aligned.
The return water guide has a box-shaped cross section having an opened side portion which is disposed so as to face a vertical wall section formed in the drive shaft housing. The return water guide is disposed on one side of the exhaust tube and the relief valve is disposed on another one side of the exhaust tube.
According to the structures and characters of the present invention mentioned above, the exhaust gas is guided to substantially the central portion of the drive shaft housing, in a plan view, by means of the exhaust tube provided for the bottom surface of the oil pan. Therefore, the exhaust gas having a high temperature does not directly collide with the outer wall section of the drive shaft housing, and hence, the temperature increasing of the outer wall section can be prevented and the adhesion of calcium, which may be contained in sea water, for example, to the outer wall section of the drive shaft housing can be also prevented.
Incidentally, the location of the relief valve to the horizontal cooling water passage and the location of the exhaust tube in the vicinity of the relief valve can allow the exhaust gas therein to be effectively cooled.
According to the present invention, the return water, which is discharged in the exhaust chamber, is guided to substantially the central portion of the drive shaft housing, in a plan view, by means of the return water guide integrally formed with the exhaust tube provided for the bottom surface of the oil pan. Therefore, the return water having a high temperature does not directly collide with the outer wall section of the drive shaft housing, and accordingly, the temperature increasing of the outer wall section can be prevented and the adhesion of calcium, which may be contained in sea water, for example, to the outer wall section of the drive shaft housing can be also prevented.
Still furthermore, the return water guide provided for the bottom surface of the oil pan to provide the box-shaped section is arranged so as to face the vertical wall section formed in the drive shaft housing, thus providing a closed sectional structure. Accordingly, the cross sectional area, i.e. effective passage area, of the cooling water discharge passages, through which the cooling water passes can be ensured to be large.
Still furthermore, since the return water guide formed integrally with the exhaust tube is formed so as to have a box-shape section, it is not necessary to use a core in the casting process, thus being advantageous in economical point and structural point and improving the yielding.
According to the present invention, furthermore, since the return water guide and the exhaust tube are formed integrally, the return water having a temperature lower than that of the exhaust gas can be utilized as the cooling water for the exhaust tube. Moreover, the return water guide is disposed on one side of the exhaust tube so as to oppose to the water pressure valve which is disposed on the other side of the exhaust tube, so that the portion of the exhaust tube which has not been cooled by the cooling water discharged from the water pressure valve can be cooled by the return water, thus improving the cooling efficiency of the exhaust tube and the exhaust gas.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.
REFERENCES:
patent: 5916135 (1999-06-01), Yoshida et al.
patent: 5937801 (1999-08-01), Davis
patent: 5984742 (1999-11-01), Kimura et al.
patent: 6012956 (2000-01-01), Mishima et al.
patent: 6053784 (2000-04-01), Takahashi
Isobe Satoshi
Toyama Takeshi
Morano S. Joseph
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Suzuki Kabushiki Kaisha
Wright Andrew
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