JPS6157491A - Muffler for outboard motor - Google Patents

Abstract

PURPOSE:To kill a radiant noise in a specific frequency range without fail, by installing an enclosed-form resonance chamber, having an intake port of the engine radiant noise, in a part at the more suction upperstream side than a suction intake port of a carburetor in an internal empty space of a cowling covering the engine and the carburetor. CONSTITUTION:A suction manifold 15, a carburetor 16 and a suction box 17 are all connected to an engine 14 of an outboard motor 10, and these constituent parts are covered with a cowling 18. In this case, a resonant type muffler 24 is installed at both sides of the suction box 17 in an internal empty space of the cowling 18. And, the muffer 24 is constituted of an intake pipe 25 to be interconnected to the inside of the suction box 17 and an enclosed-form resonance chamber 27 to be interconnected to the intake pipe 25 via an intake port 26. With this constitution, in time of driving the outboard motor 10, a radiant noisd out of the engine 14 radiated out of a suction intake port 21 of the carburetor 16 is muffled at a extensive frequency range in cooperation with an expansion- contraction type muffling effect in the suction box 17 and afterward it is killed in a specific frequency range in cooperation with a resonant type muffling effect at the resonance chamber 27.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a muffler for an outboard motor.

['il! Conventionally, in outboard motors in which the engine is housed inside the cowling, methods of muffling engine noise, particularly noise emitted from the intake port of a carburetor connected to the engine, have been proposed. The noise reduction method uses a cowling sound insulation method, and an expansion/contraction type noise reduction method using an intake box connected to the intake inlet of the carburetor.

However, with the above-mentioned conventional silencer, it is not possible to muffle engine radiated sound in a predetermined frequency range,
In particular, it is difficult to muffle the radiated sound in the low frequency range emitted from the intake port of the carburetor.

The present applicant has already proposed ``a muffler for an outboard motor in which a resonance chamber is formed between the inner surface of the cowling and the outer surface of the engine'' in Japanese Patent Application No. 58-179298. According to this already proposed muffler, the resonance chamber formed inside the cowling makes it possible to muffle the engine's radiated sound in a specific frequency range.

However, the previously proposed mufflers do not form a closed resonant chamber, and cannot provide complete resonant muffling to the sound radiated from the engine.

[Object of the Invention] It is an object of the present invention to perform complete resonance-type muffling of the radiated sound of an engine with a relatively simple structure, thereby making it possible to reliably muffle the radiated sound in a specific frequency range.

[Structure of the Invention] In order to achieve the above object, the present invention provides a silencer for an outboard motor in which a carburetor is connected to an engine and the engine and carburetor are covered by a cowling, in which: A closed resonance chamber having an inlet for introducing engine radiated sound is provided upstream of the intake inlet of the carburetor.

[Detailed Description of the Invention] Figure 1 shows an outboard motor to which the first embodiment of the present invention is applied.
FIG. 2 is a side view showing O, and FIG. 2 is a sectional view taken along the line ■-■ in FIG.

The outboard motor 10 allows a propulsion unit 13 to be attached to the hull 11 via a bracket 12.

The propulsion unit 13 has a V-type six-cylinder two-stroke engine 14 mounted on the top. An intake manifold 15, a carburetor 16, and an intake box 17 are connected to the engine 14.

Furthermore, a cowling 18 that covers the engine 14, the intake manifold 15, the carburetor 16, and the intake box 17 is removably disposed above the propulsion unit 13. The cowling 18 can protect the engine 14 and the like from splashing seawater and the like. The cowling 18 is provided with an opening 19, and the combustion air of the engine 14 is routed through the opening 19 as shown by the arrow in FIG. It can be inhaled into the engine 14 through the inlet 21. Here, the intake box 17 is
Engine 1 radiated from intake inlet 21 of carburetor 16
The cowling 18 has the function of an expansion/contraction type silencer for the radiated sound of the propulsion unit 1.
The lower cowling 18A fixed to 3 and the lower cowling'
It consists of an upper cowling 18B attached to the upper part of the cowling 18A, and a rubber seal 1 is attached to the joint surface of the lower cowling 18A and the upper cowling '18B to ensure sound insulation and watertightness.
0a is provided. .

Further, in FIG. 1, 22 is a lubricating oil tank, and 23 is a lubricating oil pump, and the lubricating oil pump 23 is capable of supplying lubricating oil to each part of the engine 14 via the intake manifold 5.

Thus, the outboard motor 10 has resonance-type mufflers 24 mounted on the left and right sides of the intake box 17 in the interior space of the cowling 18.
It is equipped with The muffler 24 includes an introduction pipe 25 that communicates with the inside of the intake box 17, and a sealed resonance chamber 27 that communicates with the introduction pipe 25 through an introduction port 26. That is, the radiated sound of the engine 14 emitted from the intake port 21 of the carburetor 16 is transmitted from the intake box 17 to the intake pipe 25. It can be introduced into the resonance chamber 27 through the introduction port 26. The silencer 24 has the length of the introduction L325 and the diameter of the introduction port 26.

By selecting the volume of the resonance chamber 27, it is possible to muffle the radiated sound of a specific frequency as shown in FIG.

Next, the operation of the first embodiment will be explained.

When the outboard motor 10 is operating, the engine 14's radiated sound emitted from the intake port 21 of the carburetor 16 is muted in a wide frequency range by an expansion/contraction type silencing effect in the intake box 17. After that, the introduction pipe 25. of the silencer 24 is inserted. Inlet port 26
The sound enters the sealed resonance chamber 27 through the air, and obtains a completely resonant silencing effect, thereby making it possible to reliably muffle radiated sound in a specific frequency range 1, for example, a low frequency range. The solid line in FIG. 4 shows the silencing state before the muffler 24 is installed, and the broken line shows the silencing state where the muffling, particularly in the low frequency range, is achieved by installing the muffler 24.

Note that the muffling frequency by the muffler 24 is determined by the length of the introduction pipe 25, the diameter of the inlet port 26, and the volume of the resonance chamber 27 as described above. It is possible to relatively easily form the muffler 24 in a shape that matches the muffling frequency.

Further, the muffler 24 does not obstruct the combustion air path of the engine 14 as shown by the arrow in FIG. 2, and the installation of the muffler 24 does not cause any turbulence in the flow of intake air.

FIG. 5 is a cutaway plan view showing essential parts of an outboard motor to which a second embodiment of the present invention is applied.

This second embodiment differs from the first embodiment in that, instead of the muffler 24, it is integrated into the main body of the engine 14 on the starboard side of the outboard 4,210 in the interior space of the cowling 18. A resonance type muffler 31 is provided, and the cowling 1
A resonance type muffler 32, which is integrated into the inner surface of the cowling 18, is provided on the port side of the outboard motor 10 in the internal space of the cowling 18. The muffler 31 has a sealed resonance chamber 33.
The intake box 17 has an inlet 34 opposite to the air intake 20 on the right side of the intake box 17, so that the radiated sound of the engine 14 emitted from the air intake 20 can be introduced. Also, silencer 3
2 has an inlet 36 opposite to the air intake 20 on the left side of the intake box 17 in a closed resonance chamber 35, so that the radiated sound of the carrot 14 emitted from the air intake 20 can be introduced. . Therefore, in the second embodiment as well, when the outboard motor 10 is operated, the sound radiated from the engine 14 emitted from the intake port 21 of the carburetor 16 has an expansion and contraction type muffling effect in the intake box 17. After being subjected to sound reduction in a wide frequency range, each inlet 34.36 of the silencer 31.32
The sound enters the sealed resonance chambers 33 and 35 through the air, and obtains a complete resonance-type silencing effect, thereby making it possible to reliably silence radiated sound in a specific frequency range 1, for example, a low frequency range.

Note: The muffling frequency by the muffler 31.32 is determined by the volume of the resonance chamber 33.35 and the diameter of the inlet port 34.36.
8, and it is possible to relatively easily form the muffler 3, 32 having a shape that matches the muffling frequency.

Furthermore, the silencers 31 and 32 do not obstruct the combustion air path of the engine 14 as shown by the arrow in FIG. There is no.

[Effects of the Invention] As described above, one aspect of the present invention is to connect a carrot to a vaporizer,
A silencer for an outboard motor in which the engine and the carburetor are covered by a cowling, the airtight seal having an inlet for introducing engine radiated sound into a portion of the interior space of the cowling upstream of the intake inlet of the carburetor. A resonant chamber of the shape is provided. Therefore, when the outboard motor is operating, the engine noise emitted from the intake port of the carburetor enters the sealed resonance chamber through the intake port of the silencer, obtaining a completely resonant silencing effect. , it is possible to reliably muffle radiated sound in a specific frequency range.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an outboard motor to which the first embodiment of the present invention is applied, FIG. 4 is a diagram showing the silencing characteristics of the outboard motor according to the second embodiment of the present invention, FIG. 4 is a diagram showing the silencing state before and after application of the silencer according to the same embodiment, and FIG. FIG. 3 is a plan view showing a main part cut away. 10... Outboard motor, 14... Engine, 16... Carburization; $, 18... Cowling, 21... Air intake inlet. 24.31.32...Silencer, 26.34.36...
・Inlet, 27.33.35...resonance chamber. Agent Patent Attorney Osamu Shiokawa Figure 1 Figure 2 Figure 3 Figure 4 1-Yo Binku (Hz) -Kusuga (H2J Figure 5)

Claims (1)

[Claims] (1) In an outboard motor silencer in which a carburetor is connected to the engine and the engine and carburetor are covered by a cowling, the engine 1. A silencer for an outboard motor, comprising a sealed resonance chamber having an inlet for introducing radiated sound.