JP2978535B2 - Exhaust system for 4-cycle outboard motor - Google Patents

Description

The present invention relates to an exhaust system for a four-stroke outboard motor, and more particularly to a structure around an oil pan housed in a casing.

[Conventional technology]

Generally, a four-stroke engine requires an oil pan for storing engine oil. When such a four-stroke engine is used for an outboard motor, the oil pan is, for example, as described in Japanese Utility Model Publication No. 47-27113.
It is housed in the upper part of the upper casing of the propulsion unit.
An engine is mounted on the casing, and exhaust gas from the engine is discharged from an exhaust outlet that opens into water at a lower portion of the casing via an exhaust passage passing near the oil pan and an exhaust expansion chamber that houses the oil pan. . Also, in order to cool the exhaust gas in the exhaust passage, the cooling water drained after cooling the engine is passed through the outer wall of the exhaust passage and the exhaust expansion chamber, and the cooling water pumped by the pump is also cooled in the oil pan to cool the oil pan. Introduced along the outer wall.

[Problems to be Solved by the Invention] As described above, in the structure in which the oil pan is housed in the exhaust expansion chamber, the exhaust gas that enters the exhaust expansion chamber from the exhaust pipe comes into contact with the oil pan outer wall, The oil pan is heated by the heat of the exhaust gas. Therefore, it is still not possible to reliably prevent the oil in the oil pan from deteriorating due to heat.

Further, in this conventional structure, droplets of the cooling water introduced into the exhaust expansion chamber adhere to the outer wall of the oil pan, and are heated by the exhaust in contact with the outer wall of the oil pan, and the salt crystallizes.
When the outboard motor is not used, the crystallized salt absorbs moisture in the air by deliquescent and comes into contact with the air, which causes the supply of oxygen to corrode the outer wall of the oil pan. There is.

The present invention has been made in view of such problems of the related art, and an object of the present invention is to heat an oil pan by exhaust gas passing through an exhaust pipe and an exhaust expansion chamber that constitute an exhaust passage. It is an object of the present invention to provide a four-cycle outboard motor exhaust system which is effectively prevented.

[Means for solving the problem]

In order to achieve such an object, the present invention has an engine mounted on a casing of a propulsion unit, an oil pan is housed near an upper part of the casing, and an exhaust outlet that opens into water is formed at a lower part of the casing, In a four-stroke outboard motor in which the engine and the exhaust outlet are connected by an exhaust passage near the oil pan, the cross section of the oil pan has a concave portion, and the exhaust passage is arranged in the concave portion.
Each of the oil pan and the exhaust passage is provided separately from the casing.

[Action]

Since the wall surface of the exhaust passage is loosened from the wall surface of the oil pan, the exhaust gas passing through the exhaust passage does not directly heat the outer wall of the oil pan. The exhaust from the exhaust passage to the exhaust outlet is
For example, the sound is silenced in an exhaust expansion chamber or the like. However, since the exhaust is isolated from the oil pan, the exhaust does not directly contact the oil pan, thereby preventing the oil pan from being heated by the exhaust. it can. Further, since the oil pan has a cross-sectional shape and the exhaust passage is arranged in the concave portion, the size of the outboard motor can be reduced in size.

〔Example〕

Hereinafter, the present invention will be described based on embodiments shown in the drawings.

FIG. 1 shows the entire structure of a general outboard motor. The engine 10 is mounted on an upper casing 12 of the propulsion unit and is covered by a cowling 14. The output of the engine 10 is transmitted to a drive shaft 18 extending through the upper casing 12 to the lower casing 16, and transmitted to a propeller 22 provided on the lower casing 16 via a shift mechanism 20. The upper casing 12 is supported by a swivel bracket 24 and a swivel shaft 25 (second
(See FIG.). Swivel bracket 24 is a clamp bracket fixed to the stern plate 30 of the hull
The propulsion unit is attached to the hull so as to be rotatable up, down, left and right with respect to the hull. Reference numeral 32 denotes a steering bracket.

Reference numeral 34 denotes an oil pan described later, which is housed in the upper part of the upper casing 12, and an exhaust pipe 36 from the engine 10 extends downward near the oil pan 34, and the exhaust pipe 36 is connected to an exhaust expansion chamber 38. It is connected. The expansion chamber 38 passes through the lower casing 16 and communicates with an exhaust outlet 40 formed at the boss of the propeller 22.

As shown in detail in FIGS.
Is firmly mounted on a support plate 42 mounted on the upper end of the upper casing 12, and the support plate 42 is connected to the steering bracket via an upper support mount 43.
Connected to 32. The oil pan 34 is suspended and fixed to the support plate 42 while being sandwiched between the support plate 42 and the upper casing 12.

The oil pan 34 has a substantially bottomed box shape and an exhaust pipe 36.
As shown in FIG. 4, the central portion is depressed when viewed from above so as to pass through vertically. The wall surface of the exhaust pipe 36 is separated from the wall surface of the depressed portion of the oil pan 34 at a certain distance, and the heat of the exhaust pipe 36 is directly transmitted to the oil pan 34 between the two. An air layer 35 is formed to prevent the occurrence of air.

Reference numeral 44 denotes a screen facing the bottom of the oil pan 34, 45 denotes an oil suction pipe, and 46 denotes a relief valve for oil flowing from the engine 10.

The upper end of the exhaust passage 36 communicates with an exhaust port (not shown) of the engine 10 via a passage formed in the support plate 42. The lower end of the exhaust pipe 36 extends further below the bottom wall of the oil pan 34, and is supported in a liquid-tight manner by a seal member 50 between the exhaust pipe 36 and a lid 48, which will be described later. It extends to and terminates. Reference numeral 52 denotes a water passage formed integrally with the exhaust pipe 36 around the exhaust pipe 36,
As shown in FIG. 3, the lower end is formed in the passage 51 of the seal member 50.
Through a water reservoir 54 formed around the expansion chamber 38 and the inside of the expansion chamber 38. The expansion chamber 38 and the water reservoir 54
Is closed by a lid 48 and is isolated from the oil pan 34. Drain hole 55 at the lower end of water reservoir 54
Are formed. On the upper wall defining the expansion chamber 38,
A throttle passage 56 for discharging the exhaust gas at low speed from the expansion chamber 38 is formed. The throttle passage 56 is connected to the upper casing 12 through a sub-expansion chamber 58 formed between the inner wall of the upper casing 12 and the partition wall 57. It communicates with an exhaust outlet 60 provided at the upper part of the outer wall. Here, the sub-expansion chamber 58 is also isolated from the outer wall of the oil pan 34.

The cooling water is obtained by drawing seawater around the outboard motor from a water intake port (not shown) of the lower casing 16 by a cooling water pump 62 driven by the drive shaft 18. This cooling water is introduced upward to the engine 10 through a cooling water suction pipe 63, and the engine cooling water after cooling the engine 10 is discharged through the water passage through the support plate 42.
It is configured to be guided to 52.

According to such a configuration, the engine oil which has lubricated various parts of the engine 10 is returned to the oil pan 34, and the oil is returned to the engine 10 via the oil suction pipe 45 from the screen 44. Is done.

Exhaust gas from the engine 10 is introduced into the expansion chamber 38 through the exhaust pipe 36. The exhaust pipe 36 is connected to the oil pan 34 through the air layer 35.
The exhaust heat is not directly transmitted to the oil pan 34 to heat the oil pan. Exhaust is in the expansion chamber 38
It is expanded and silenced inside. At a high speed, the air is discharged from the outlet below the expansion chamber 38 through the passage of the lower casing 16 to the sea through an exhaust outlet 40 that opens into the water. Since the expansion chamber 38 is isolated from the oil pan 34 by the lid 48, the expansion chamber 38
Exhaust gas released to 38 does not touch oil pan 34 to heat oil pan. At a low speed, the air is discharged from the expansion chamber 38 through the throttle passage 56 to the air from the exhaust outlet 60 through the auxiliary expansion chamber 58. Here, too, the sub-expansion chamber 58 is isolated from the oil pan 34 by a partition wall 57.

The water sucked as the cooling water is pumped upward from the cooling water suction pipe 63 to the engine 10 to cool the engine. After cooling the engine, the cooling wastewater is first introduced into the water passage 52 around the exhaust pipe 36 to cool the exhaust pipe 36 and the exhaust passing therethrough. After that, this cooling drainage is partially
The other part falls into the expansion chamber 38 while falling into the water reservoir 54 around the 38. Thus, the exhaust gas in the expansion chamber 38 is directly and indirectly cooled. The water that has fallen into the expansion chamber 38 returns to seawater from below. Although a small amount of the water that has entered the water reservoir 54 is discharged downward from the drain hole 55, it is retained here because the supply amount is large, and effectively cools the outer wall of the expansion chamber 38. At this time, a notch (not shown) is provided at the upper end of
Water accumulated in 54 overflows and upper casing 12
It is good to return to the sea surface along the inner wall of the building. Even if the water accumulated in the sump 54 jumps off due to external force or exhaust pressure transmitted from the sea surface to the outboard motor, etc., since the upper part is closed by the lid 48, the water containing salt is contained. Water droplets can be prevented from adhering to the oil pan 34,
Therefore, corrosion of the oil pan can be reliably prevented. That is, as in the conventional case, when seawater droplets adhere to the oil pan during use of the engine and the oil pan is heated by the exhaust, the seawater droplets crystallize, and the crystals grow each time the engine is used, and the outboard motor The salt crystallized when not in use absorbs the moisture in the air due to the deliquescence, and comes into contact with the air and receives the supply of oxygen, which corrodes the outer wall of the oil pan. Can be prevented.

In order to prevent the water that has entered the expansion chamber 38 from flowing backward, a side hole 65 is preferably provided on one side wall of the portion of the exhaust pipe 36 that extends into the expansion chamber 38.

Next, FIG. 5 shows a second embodiment of the present invention. This embodiment is different from the first embodiment in that an exhaust pipe 36 and an oil pan 34 are integrally formed, and both are connected with a connecting wall. It is a point that is separated from each other at a certain interval through 70. In this case, it is desirable that the connecting wall 70 connects the outer wall of the water passage 52 of the exhaust pipe and the outer wall of the oil pan from the viewpoint of preventing oil pan heating.

Next, FIG. 6 shows a third embodiment of the present invention. This embodiment is different from the above-described first embodiment in that a cooling water suction pipe 63 is provided.
This is the point that the cooling water introduced into the engine 10 is released in the upper casing 12 containing the oil pan 34 in the middle and above the lid 48. According to this embodiment,
Since the cooling water also flows through the bottom outer wall of the oil pan 34 and between the separated oil pan and the exhaust pipe 36, the oil pan is actively cooled, and the exhaust pipe is also cooled more effectively. You. Here, since the cooling water flows during the operation of the engine, it does not crystallize on the outer wall of the oil pan or the like. When the operation is stopped, the cooling water adhering to the oil pan wall without flowing down evaporates due to the residual heat of the oil in the oil pan,
Although salt content may crystallize, it is negligible compared to the case where seawater droplets are constantly crystallized and growing due to contact with exhaust as in the past.

In FIG. 6, reference numeral 72 denotes a bypass hole for partially introducing cooling water from the cooling water suction pipe 63 into the water reservoir 54, whereby the expansion chamber 38 can be cooled more effectively. The cooling water is allowed to flow to the vicinity of the partition wall 57 that separates the sub-expansion chamber 58 and the oil pan 34, and also cools the exhaust of the sub-expansion chamber 58. Exit
It can also be discharged from 74. In the embodiment of FIG. 2, the lower part of the air layer 35 in the figure and the water reservoir 54 communicate with each other by a small hole, and the engine cooling water after cooling the engine is led to the air layer 35 in the figure so as to function as a water pool. May be.

〔effect〕

As described above, according to the present invention, the sectional shape of the oil pan is concave, and the exhaust passage is arranged in the concave. Therefore, the oil pan wall is not directly heated by the exhaust gas, and the oil pan is not heated. There is an excellent effect that deterioration and corrosion of the oil pan wall can be prevented. Further, with the above configuration, the size of the outboard motor can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a side view showing the overall structure of a four-cycle outboard motor according to the present invention. FIG. 2 is a sectional view of a main part showing a first embodiment of an exhaust system for a four-cycle outboard motor according to the present invention. 3 is a sectional view taken along the line III-III of FIG. 2, FIG. 4 is a sectional view taken along the line IV-IV of FIG. 2, and FIG. 5 is a fourth view showing a second embodiment of the present invention.
FIG. 6 is a cross-sectional view of a main part showing the third embodiment of the present invention. 10 ... Engine 12 ... Upper casing 34 ... Oil pan 35 ... Air layer 36 ... Exhaust pipe 38,58 ... Expansion chamber 40,60 ... Exhaust outlet 48 ... Lid 52 ... Water passage 70 ... … Connecting wall

Claims (1)

(57) [Claims] An engine is mounted on a casing of a propulsion unit, an oil pan is accommodated near an upper portion of the casing, and an exhaust outlet which opens into water is formed at a lower portion of the casing. In the four-stroke outboard motor connected to the exhaust passage near the pan, the cross section of the oil pan is a concave portion, and the exhaust passage is arranged in the concave portion, and each of the oil pan and the exhaust passage is An exhaust device for a four-cycle outboard motor, which is provided separately from a casing.