JPH0456696A - Exhaust device for four-cycle outboard motor - Google Patents

Abstract

PURPOSE:To prevent an oil pan from being heated by exhaust effectively by isolating the wall surface of an exhaust passage from that of the oil pan, and also isolating exhaust reaching an exhaust port from the exhaust passage so as not to be in contact with the wall surface of the oil pan. CONSTITUTION:An engine 10 placed on the upper casing 12 of a propulsion unit is covered with a cowling 14. An oil pan 34 is enclosed at an upper part in the upper casing 12, and an exhaust pipe 35 from the engine 10 passes in the vicinity of the oil pan and is extended downward so as to be communicated with an exhaust expansion chamber 38. The expansion chamber 38 passes a lower casing 16 and is communicated with an exhaust port 40 formed at the boss part of a propeller 22. In this case, the wall surface of the exhaust pipe 36 is isolated by the specified distance from the wall surface of the oil pan 34, and an air layer is formed between both of them. The lower end part of the exhaust pipe 36 is supported on the way in the liquid-tight state by a seal member provided between a lid body and the exhaust pipe 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust system for a four-stroke outboard motor, and particularly to a structure around an oil pan housed in a casing.

[Conventional technology]

Generally, a four-stroke engine requires an oil pan to store engine oil. When such a four-stroke engine is used as an outboard motor, the oil pan is housed in the upper part of the upper casing of the propulsion unit, as described in, for example, Japanese Utility Model Publication No. 47-27113. The engine is mounted on this casing, and the exhaust gas from the engine is discharged through an exhaust passage that passes near the oil pan, an exhaust expansion chamber that houses the oil pan, and an exhaust outlet that opens into the water at the bottom of the casing. . In addition, in order to cool the exhaust gas in the exhaust passage, the cooling water after cooling the engine is passed through the outer wall of the exhaust passage and the exhaust expansion chamber, and in order to also cool the oil pan, the cooling water pumped up by the pump is passed through the oil pan. It is installed along the outer wall.

[Problem to be solved by the invention]

In this structure, where the oil pan is housed in the exhaust expansion chamber, the exhaust gas entering the exhaust expansion chamber from the exhaust pipe comes into contact with the outer wall of the oil pan, and the oil pan is heated by the heat of the exhaust gas. It turns out. Therefore, it is still not possible to reliably prevent the oil in the oil pan from deteriorating due to heat.

In addition, with this conventional structure, droplets of cooling drainage introduced into the exhaust expansion chamber adhere to the outer wall of the oil pan, and are heated by the exhaust gas in contact with the outer wall of the oil pan, crystallizing the salt. There is a problem in that this crystallized salt absorbs moisture in the air due to its deliquescent action, and also comes into contact with the air, receives the supply of oxygen, and corrodes the outer wall of the oil pan.

The present invention was made in view of the problems of the prior art, and its purpose is to prevent the oil pan from being heated by the exhaust gas passing through the exhaust pipe and exhaust expansion chamber that constitute the exhaust passage. An object of the present invention is to provide an exhaust system for a four-stroke outboard motor that effectively prevents air pollution.

[Means to solve the problem]

In order to achieve such an object, the present invention provides an engine mounted on the casing of the propulsion unit. In a four-stroke outboard motor, an oil pan is housed near the top of the casing, an exhaust outlet opening into the water is formed at the bottom of the casing, and the engine and this exhaust outlet are communicated through an exhaust passage near the oil pan. , the wall surface of the exhaust passage and the wall surface of the oil pan are separated from each other, and the exhaust gas from the exhaust passage to the exhaust outlet is isolated so as not to come into contact with the wall surface of the oil pan.

[Effect]

Since the wall surface of the exhaust passage and the wall surface of the oil pan are spaced apart, the exhaust gas passing through the exhaust passage does not directly heat the outer wall of the oil pan. The exhaust gas that reaches the exhaust outlet from the exhaust passage is muffled, for example, by an exhaust expansion chamber, but since this exhaust gas is isolated from the oil pan, the exhaust gas does not come into direct contact with the oil pan. This also prevents the oil pan from heating up.

〔Example〕

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

FIG. 1 shows the overall structure of an outboard motor for boat fishing. The engine 10 is an upper casing 12 of the propulsion unit.
It is placed on top and covered by a cowling 14. The output of the engine 10 is transmitted to a drive shaft 18 that passes through the upper casing 12 and extends to the lower casing 16, and is transmitted to the lower casing 16 via a shift mechanism 20.
is transmitted to a propeller 22 provided at The upper casing 12 is supported by a swivel bracket 24 and is rotatable left and right around a swivel shaft 25 (FIG. 2). The swivel bracket 24 has a tilt axis 28 relative to a clamp bracket 26 fixed to the stern plate 30 of the hull.
The propulsion unit is connected to be rotatable up and down around the hull, and thereby the propulsion unit is attached to be rotatable up and down and left and right with respect to the hull.

Reference numeral 32 is a steering bracket.

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

As shown in detail in FIGS. 2 to 4, the engine 10
is firmly attached to the support plate 42 attached to the upper end of the upper casing 12, and
2 is connected to the steering bracket 32 via an upper support mount 43. This support plate 42
The oil pan 34 is suspended and fixed to the support plate 42 while being sandwiched between the upper casing 12 and the upper casing 12 .

The oil pan 34 has a substantially bottomed box shape, and the exhaust pipe 3
As shown in FIG. 4, the central portion thereof is recessed when viewed from the plane in order to allow the rod 6 to pass up and down. and,
The wall surface of the exhaust pipe 36 is separated from the wall surface of the depressed portion of the oil pan 34 by a certain distance, and there is a space between the two to prevent heat from the exhaust pipe 36 from being directly transmitted to the oil pan 34. Air Fi35 is formed.

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

The upper end of the exhaust pipe 36 communicates with an exhaust boat (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 downward than the bottom wall of the oil pan 34, and is fluid-tightly supported in the middle by a sealing member 50 between it and a lid 48, which will be described later. It extends and ends. Reference numeral 52 designates a water passage that is integrally formed with the exhaust pipe 36 and is divided around the exhaust pipe 36. As shown in FIG. It communicates with the formed water reservoir 54 as well as with the expansion chamber 38 . The upper openings of the expansion chamber 38 and the water reservoir 54 are closed by a lid 48 and isolated from the oil pan 34. A drain hole 55 is formed at the lower end of the water reservoir 54.

A throttle passage 56 for discharging exhaust gas at low speed from the expansion chamber 38 is formed in the upper part of the wall defining the expansion chamber 38, and the throttle passage 56 is connected to 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 of the upper casing 12 via a sub-expansion chamber 58 formed between the upper casing 12 and the upper casing 12 . Here, this sub-expansion chamber 58 is also isolated from the outer wall of the oil pan 34.

The cooling water is seawater around the outboard motor sucked in 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 1o via a cooling water suction pipe 63, and the engine cooling water after cooling the engine 10 is introduced to the waterway 52 via the support plate 42. There is.

According to such a configuration, the engine oil that has become hot after lubricating each part of the engine 10 is returned to the oil pan 34, and this oil is again forced to be sent to the engine 10 from the screen 44 via the oil suction pipe 45. be done.

Exhaust from the engine 10 passes through the exhaust pipe 36 and expands into the expansion chamber 3.
8 will be introduced. Since the exhaust pipe 36 faces the wall surface of the oil pan 34 through the air layer 35, the heat of the exhaust gas is not directly transmitted to the oil pan 34 and does not heat the oil pan. The exhaust gas is expanded and muffled within the expansion chamber 38. At high speeds, the air is discharged into the sea from the lower outlet of the expansion chamber 38, through the passage of the lower casing 16, and from the 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 exhaust gas released into the expansion chamber 38 does not touch the oil pan 34 and heat the oil pan. At low speeds, the air passes from the expansion chamber 38 through the throttle passage 56 and is discharged into the air from the exhaust outlet 60 via the sub-expansion chamber 58. Also here, the sub-expansion chamber 58 is separated from the oil pan 34 by the partition wall 57.

The water sucked in as cooling water is pumped upward from the cooling water suction pipe 63 to the engine 10 to cool the engine.

After the engine has been cooled down, the cooling water drains first through the exhaust pipe 36.
is introduced into the waterway 52 around the exhaust pipe 36 and cools the exhaust gas passing therethrough. Thereafter, part of this cooling waste water falls into the water reservoir 54 around the expansion chamber 38, and the other part falls into the expansion chamber 38. Thereby, the exhaust gas in the expansion chamber 38 is directly and indirectly cooled. Expansion chamber 3
Water that falls during the day returns to seawater from below. A small amount of the water that has entered the water reservoir 54 is discharged downward from the drain hole 55, but since the amount of water supplied is large, it stays here and effectively drains the water into the expansion chamber 55.
Cool the outer wall of No.8. Here, it is preferable to provide a notch (not shown) at the upper end of the water reservoir 54 so that the water accumulated in the water reservoir 54 overflows and returns to the sea surface along the inner wall of the upper casing 12. Even if the water accumulated in this water reservoir 54 splashes due to external force transmitted from the sea surface to an outboard motor or exhaust pressure, etc., the upper part of the water is blocked by the lid body 48, so that it does not contain salt. Water droplets can be prevented from adhering to the oil pan 34, and therefore corrosion of the oil pan can be reliably prevented. In other words, as in the past, when seawater spray adheres to the oil pan while the engine is in use and the oil pan is heated by exhaust gas, the seawater spray crystallizes, and the crystals grow each time the engine is used, causing the outboard motor to Salt that crystallizes when not in use absorbs moisture from the air due to its deliquescent action, and when it comes into contact with air, it is supplied with oxygen and corrodes the outer wall of the oil pan. It can be prevented.

In order to prevent the water that has entered the expansion chamber 38 from flowing backward, it is preferable to provide a side hole 65 in one side wall of the portion of the exhaust pipe 36 that extends within three days of the expansion chamber.

Next, FIG. 5 shows a second embodiment of the present invention, and this embodiment differs from the first embodiment described above in that an exhaust pipe 36 and an oil pan 34 are integrally formed, and both are connected by a connecting wall. 70 are points spaced apart from each other at regular intervals. In this case, it is desirable that the connecting wall 70 connects the outer wall of the waterway 52 of the exhaust pipe and the outer wall of the oil pan from the viewpoint of preventing heating of the oil pan.

Next, FIG. 6 shows a third embodiment of the present invention, and this embodiment differs from the first embodiment described above in that the cooling water suction pipe 63
The cooling water introduced into the engine IO from the inside of the upper casing 12 that accommodates the oil pan 34,
This is the point where the lid body 48 is opened upward. According to this embodiment, 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, so the oil pan is actively cooled.
Moreover, the exhaust pipe is also cooled more effectively. Since this cooling water flows during engine operation, it does not crystallize on the outer wall of the oil pan. When the operation is stopped, the cooling water that adheres to the oil pan wall without flowing down may evaporate due to the residual heat of the oil in the oil pan, and the salt may crystallize. Seawater spray crystallizes,
This is negligible compared to when it is growing.

In FIG. 6, reference numeral 72 denotes a bypass hole through which a portion of the cooling water from the cooling water suction pipe 63 is introduced into the water reservoir 54, so that the expansion chamber can be cooled more effectively. Note that the cooling water is made to flow up to the vicinity of the partition wall 57 separating the sub-expansion chamber 58 and the oil pan 34 to cool the exhaust gas of the sub-expansion chamber 58, and this cooling water is used as pilot water formed in the upper part of the upper casing 12. It can also be discharged from the output lower 4. Second
In the illustrated embodiment, the lower part of the air layer 35 and the water reservoir 5 are shown in the figure.
After cooling the engine, the engine cooling water may be introduced into the air layer 35 in the figure to function as a water reservoir.

[Effects] As explained above, according to the present invention, the engine exhaust and the oil pan are separated and the oil pan wall and the exhaust passage wall are separated, so that the oil pan wall is not directly heated by the exhaust gas. This has the excellent effect of preventing oil deterioration and corrosion of the oil pan wall.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the overall structure of a four-stroke outboard motor according to the present invention, and FIG. Figure 3 is a cross-sectional view taken along line ■-■ in Figure 2, and Figure 4 is a cross-sectional view taken along line IV-IV in Figure 2.
FIG. 5 is a cross-sectional view of a main part of the same level as FIG. 4 showing a second embodiment of the present invention, and FIG. 6 is a cross-sectional view of a main part of a 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 body 52 - 111 Water passage 70 - Connecting wall Agent Patent attorney Yoshiyuki Inaba Diagram

Claims (1)

[Claims] (1) An engine is mounted on the casing of the propulsion unit, an oil pan is housed near the top of the casing, and an exhaust outlet opening into the water is formed at the bottom of the casing.
In a four-stroke outboard motor in which the engine and the exhaust outlet are communicated through an exhaust passage near the oil pan, the wall of the exhaust passage is separated from the wall of the oil pan, and the exhaust from the exhaust passage to the exhaust outlet is connected to the oil pan. Exhaust system for a 4-stroke outboard motor isolated to prevent contact with the wall.