JPS6217088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust silencing device for an outboard motor, and more particularly to a device for muffling and discharging the exhaust gas of an outboard motor when the engine is idling.

Conventionally, the main exhaust port 11 of a small outboard motor 10 such as a full-pivot type is formed near the propeller 14 (lower casing) of a casing 13 that houses a drive shaft 12, as shown in FIG. There is. This main exhaust port 11 is usually under water,
Exhaust gas during navigation of the ship is discharged into the water from the main exhaust port 11 through the internal chamber 15 of the casing 13, thereby achieving a noise reduction effect.

However, when the outboard motor 11 is idling, the boat is not sailing, so the outboard motor 11 is submerged in water at a deep depth. In other words, as shown in FIG. When the engine is idling, it becomes the position indicated by reference numeral 16'. Therefore, since the main exhaust port 11 is located considerably below the water surface 16', the exhaust gas is subjected to back pressure due to the water pressure, and smooth exhaustion is not performed. For this reason, the casing 13 has an exhaust hole, or so-called idle hole 17, formed in the upper part of the casing at a position above the water surface 16' to discharge exhaust gas to the atmosphere during idling. However, in a small outboard motor, since the volume inside the casing 13, that is, the internal chamber 15 is small, a silencer is installed to reduce the exhaust pressure of the exhaust gas discharged to the atmosphere through the idle hole 17 to reduce noise. I can't.

Furthermore, if the diameter of the idle hole is made small in order to suppress noise, back pressure increases, causing problems such as poor low-speed rotation of the outboard engine.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an exhaust silencing device for a small outboard motor, which reduces exhaust pressure during idling without increasing back pressure, thereby reducing noise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The exhaust silencer for an outboard motor according to the present invention will be described in more detail below with reference to preferred embodiments shown in the accompanying drawings.

In FIG. 2, a full-pivot type outboard motor equipped with the exhaust silencing device of the present invention is generally designated by the reference numeral 20.

Full pivot type outboard motor 20 like this
Like the conventional outboard motor 10 of the same type shown in FIG. It is covered by a cover 24 disposed on the top surface of the casing. A drive shaft 22 extending from the engine 21 extends through an internal chamber 26 of the casing 23 via an oil seal portion 25 (see FIG. 4) supported by an upper portion of the casing 23 and reaches a lower portion of the casing 23. , is operatively connected to a propeller 27 mounted on this lower portion.

Exhaust gas from the engine 21 is discharged into the internal chamber 26 of the casing 23, and while the ship is sailing, the exhaust gas in the internal chamber 26 is discharged into the water in order to obtain a noise-muffling effect. Therefore, propeller 27
A main exhaust port 28 is formed in the casing 23 in the vicinity of the casing 23 , and the main exhaust port 28 communicates with the internal chamber 26 of the casing 23 .

On the other hand, since the full-pivot type outboard motor 20 is small, the internal chamber 26 of the casing 23 is very narrow, and an idle hole is required to release the exhaust gas during idling into the atmosphere for the reason mentioned above. If it is formed on the casing wall of the internal chamber 26, it is difficult to install a sound deadening mechanism.

By the way, in the outboard motor 20 according to the present invention, the third
As shown in Fig. 4, the casing 2
A passage 29 through which cooling water discharged from the engine 21 flows is formed in the upper part of the engine 3. This passage 2
9 is an external wall 30 of the casing 23 and a partition wall 31
The casing 2 is separated from the internal chamber 26 by
3 is formed in a groove shape on the upper surface of the casing 23, and an engine mounting base plate (bottom cowling) 5 is formed on the upper surface of the casing 23.
0, the inner chamber 26 is completely separated from the inner chamber 26.

Such a passage 29 is formed from the rear side (the right side part in FIG. 3) to the front side (the left side part in the figure) of the casing 23, and there is a part of the partition wall on the front side. An outflow recess 32 is formed with a low upper edge and allows the cooling water to flow down into the internal chamber 26 . An oil seal portion 25 for sealing the drive shaft 22 extending from the engine 21 is disposed in an internal chamber 26 slightly forward of the center of the casing 23, and the housing of the oil seal portion 25 is used to seal the drive shaft 22 extending from the engine 21. Outflow recess 32
A cooling water storage section (hereinafter simply referred to as a storage section) 33, which is a chamber partially partitioned from the internal chamber 26, is formed on the internal chamber 26 side of the partition wall 31 in which the cooling water storage section 33 is partially partitioned from the internal chamber 26. This storage section 33 has a partition wall 3 having an L-shaped cross section.
4, a partition wall 31 in which the outflow recess 32 is formed;
The oil seal portion 25 is formed integrally with the wall portion of the housing so as to cooperate with the inner chamber 26 to form a chamber separated from the inner chamber 26. It goes without saying that this partition wall 34 may be separate and attached to the housing wall of the oil seal section 25. Therefore, this holding portion 33 is also completely separated from the internal chamber 26 when the engine mounting base plate is disposed on the upper surface of the casing 23.

However, the partition wall 34 forming the storage section 33
The bottom wall has an opening 35 to communicate with the internal chamber 26.
is formed. The size of this opening 35 is
The inflow amount is determined to be larger than the outflow amount flowing from the opening 35 into the internal chamber 26 so that a certain amount of cooling water flowing from the outflow recess 32 of the partition wall 31 to the retention portion 33 is always collected in this retention portion. be done.

Further, in the cooling water passage 29 on the upper surface of the casing 23, as shown in FIGS. 3 and 5, there is a weir 36 that rises from the bottom of the passage along its side wall and partially blocks the passage. is provided. A drainage hole 37 for draining a portion of the cooling water is formed in the passage outer wall 30 on the cooling water upstream side of the weir 36 (rear side of the casing) at a position lower than the upper end of the weir 36. Furthermore, the passage outer wall 3 on the downstream side of the cooling water (the front side of the casing) from this weir 36
0, an idle exhaust hole 38 is formed at a position higher than the upper end of the weir 36 in order to discharge exhaust gas during idling introduced into the passage 29 into the atmosphere by a function described later.

According to the silencer for the outboard motor 20 in the above embodiment, the exhaust gas discharged from the engine 21 during idling is discharged into the internal chamber 26 of the casing 23.
introduced into the world. Also, during this period, the cooling water from the engine 21 flows into the passage 2 on the rear side of the casing.
It is discharged into 9. Therefore, this cooling water flows toward the front side of the casing 23 as shown by the arrow 39 in FIG. The cooling water overflowing from the weir 36 further flows through the passage 29 and flows down from the outflow recess 32 of the partition wall into the retention section 33. However, since the amount of cooling water flowing into the storage section 33 is greater than the amount flowing out from the opening 35 into the internal chamber 36, a certain amount of cooling water is always stored in the storage section 33.

The exhaust gas introduced into the internal chamber 26 is caused by the fact that the main exhaust port 28 is relatively deeply submerged in water due to the relative rise of the water level during idling, and the exhaust pressure is low. It will not be ejected from 28. Therefore, the exhaust gas in the sealed internal chamber 26 enters the cooling water pool of the storage section 33 through the opening 35 formed in the bottom wall of the partition wall 34 of the storage section 33 as shown by the arrow 40, and then enters the cooling water pool of the storage section 33. 29 and is exhausted to the atmosphere from the idle hole 38.

In this way, the exhaust during idling is
Since the cooling water passes through the cooling water retention section formed by the engine components and the casing and is exhausted to the atmosphere through the idle hole formed in the cooling water passage, the exhaust pressure is reduced and noise is reduced. be able to. Furthermore, the cooling water storage section having the above-described structure can be formed even in a small-sized outboard motor having a small internal chamber volume, and is therefore particularly suitable for a small-sized outboard motor. Further, in such a silencer, since the idle hole is not made small, back pressure is not applied, and therefore, malfunctions do not occur when the engine rotates at low speed.

Also, during idling, the flow of cooling water flowing through the passage is regulated by a weir formed in the passage, and the cooling water drainage hole is formed at a position lower than the height of the weir, and the idle hole is formed at a position higher than the weir. Since the cooling water is formed in the idle hole, the cooling water does not exit to the atmosphere together with the exhaust gas, and therefore no gurgling noise is generated. At this time, the size of the cooling water drainage hole is such that when the amount of cooling water drained from the engine flows through the passage during idling, the amount of cooling water that exceeds the weir can always retain a certain amount of cooling water in the holding section. It is determined that Of course, in order to retain the cooling water in the retention section, the size of the opening must also be determined in order to adjust the amount of water discharged relative to the amount of water flowing into the retention section, as described above.

Note that when the engine is rotated at high speed, the amount of cooling water increases, and therefore the passage 29 is filled with cooling water. As a result, the idle hole 38 serves as a cooling water drainage hole, similar to the drainage hole 37, and does not discharge exhaust gas. In such a case, the exhaust gas is discharged underwater from the main exhaust port 28 as described above.

As described above, according to the outboard motor exhaust silencing device of the present invention, exhaust silencing during idling can be achieved even in a small outboard motor without causing engine malfunction.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of the exhaust structure of a conventional small outboard motor, Fig. 2 is a side view of a small outboard motor to which the exhaust silencing device of the present invention is applied, and Fig. 3 is a cross-sectional view showing the top surface of the casing of the outboard motor taken along line - in Figure 2, Figure 4 is a fragmentary longitudinal cross-sectional view of the casing taken along line - in Figure 3, and Figure 5 is a cross-sectional view showing the top surface of the casing of the outboard motor taken along line - The figure is a partial cross-sectional view of the casing taken along line - in FIG. 20... Outboard motor, 21... Engine, 22... Drive shaft, 23... Casing, 25... Oil seal portion,
26...internal chamber, 28...main exhaust port, 29...passage, 3
1... Partition wall, 32... Outflow recess, 33... Retention part, 3
5...Opening, 36...Weir, 37...Drain hole, 38...Idle hole.

Claims (1)

[Claims] 1. An exhaust silencing device for a small outboard motor during idling, which accommodates a drive shaft extending through a housing seal, and has a passage through which engine cooling water flows and a chamber from which exhaust gas is discharged. A casing comprising a separated chamber communicating with an opening formed under water near the propeller, a retention section for temporarily retaining the cooling water flowing through the passage, and a casing formed on the wall of the retention section for discharging the An exhaust silencing device for an outboard motor during idling, including a hole communicating with the chamber through which the exhaust gas is discharged, and an idle exhaust hole formed in a wall of the passage. 2. In an exhaust silencing device for an outboard motor during idling, the drive shaft extending through the housing seal is accommodated, and the passageway through which engine cooling water flows and the chamber through which exhaust gas is discharged are formed underwater near the propeller. a casing comprising a separated chamber that communicates with the opening, a retention section for temporarily retaining the cooling water flowing through the passage, and a chamber formed on a wall of the retention section from which the exhaust gas is discharged. A communicating hole, a weir formed in the passageway and partially blocking the passageway, a drainage hole formed in a wall of the upstream passageway of the weir at a position lower than the height of the weir, and a wall in the passageway. An exhaust silencing device for an outboard motor during idling, including an idle exhaust hole formed at a position higher than the weir in the part.