JP2811449B2 - Exhaust system of internal combustion engine for outboard motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust device for an internal combustion engine for an outboard motor.

2. Description of the Related Art In a conventional exhaust device such as an outboard motor, at least a part of an exhaust passage is formed of an outer cylinder (eg, a casing) and an inner cylinder (eg, a wall forming an exhaust expansion chamber). There is one configured with a heavy cylinder structure. At this time, the inner cylinder portion is directly fixed to an intermediate member or the like integrated with the engine and the outer cylinder portion with a bolt or the like and is cantilevered.

The reason for adopting the double cylinder structure is based on various requests such as providing a water wall, an exhaust passage, or a sound deadening layer between the outer cylinder part and the inner cylinder part.

[Problems to be Solved by the Invention] However, in the above-described conventional exhaust device, the following noise is radiated from the outer cylindrical portion to the surroundings.

The vibration of the inner cylinder part excited by the internal exhaust pressure wave is transmitted to the outer cylinder part via the water wall, the air layer, etc., and this vibrates the outer cylinder part to generate noise.

The vibration of the inner cylinder part excited by the internal exhaust pressure wave is transmitted to the outer cylinder part via an intermediate member or the like, and this vibrates the outer cylinder part to generate noise.

The vibration of the engine is transmitted to the outer cylinder via intermediate members, etc.
This vibrates the outer cylinder part and generates noise.

An object of the present invention is to reduce the noise radiated from an outer cylinder when at least a part of an exhaust path has a double cylinder structure in an internal combustion engine for an outboard motor.

Means for Solving the Problems The present invention includes an exhaust path connected to an exhaust port of an engine of an outboard motor, and at least a part of the exhaust path has a double-cylinder structure including an outer cylinder and an inner cylinder. In the exhaust device for an outboard internal combustion engine configured as described above, an outer cylinder portion is attached to a lower portion of the engine, the outer cylinder portion is extended downward, and the inner cylinder portion is lowered inside the outer cylinder portion. A water wall forming wall provided inside the outer cylinder portion, the upper portion of the inner cylinder portion being attached to the lower portion of the engine, and the lower portion of the inner cylinder portion being attached to the lower portion of the outer cylinder portion via an elastic member. Forming an expansion chamber having an exhaust port at the upper rear of the outer cylinder, and disposing an upper end of the water wall forming wall below the expansion chamber; A space communicating with the outside of the outboard motor is formed between the section and the water wall forming wall.

[Operation] Since the upper part of the inner cylinder part is attached to the lower part of the engine and the lower part of the inner cylinder part is attached to the lower part of the outer cylinder part via an elastic member, the upper and lower elastic members move between the inner cylinder part and the outer cylinder part. It becomes a thing to be sealed, and can prevent that the exhaust pulse sound which flows in an inner cylinder part leaks outside.

Since the upper end of the water wall forming wall is located below the expansion chamber forming the exhaust port at the upper rear portion of the outer cylindrical portion, the accumulated water overflows from the upper end of the water wall forming wall and flows downward. Therefore, even in a low-speed, low-load operation range where the water level is high, the exhaust water can be easily discharged from the exhaust port without blocking the exhaust port formed in the expansion chamber.

Since the water wall is formed between the water wall forming wall provided inside the outer cylinder and the inner cylinder, the sound insulation effect of the water wall can be improved.

A water wall is formed between the outer tube and the inner tube, and a space is formed between the wall for forming the water wall and the outer tube, so that water overflowing from the wall for forming the water wall flows into the space. The radiation sound of the exhaust transmitted to the outer cylinder can be effectively isolated in the space.

As described above, when at least a part of the exhaust path has the double-cylinder structure, the radiation noise from the outer cylinder can be reduced.

[Embodiment] FIG. 1 is a sectional view showing a main part of a first embodiment of the present invention, and FIG.
FIG. 3 is a sectional view taken along the line II-II of FIG. 1, and FIG.
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, and FIG. 5 is a schematic view of the exhaust path in FIG.

As shown in FIG. 1, the outboard motor 10 has a propulsion unit 12 attached to a stern plate 13 via a bracket 11. The propulsion unit 12 has an intermediate member
It is equipped with an engine 16 through 15. The output of the engine 16 is transmitted to a propeller shaft 18 via a drive shaft 17,
The propeller 19 can be driven. The engine 16 is a water-cooled engine, and a water pump 20 driven by a drive shaft 17
Pumps the external water taken in from the external water intake 21 to the engine 16.

The casing 14 holds a tubular body 22 at the center. The tubular body 22 has a main expansion chamber 23 formed therein.
An exhaust pipe 26 communicating with the exhaust passage 24 of the engine 16 and the exhaust passage 25 of the intermediate member 15 is opened in the main expansion chamber 23.

That is, in this embodiment, a part of the exhaust passage connected to the engine 16 is connected to the casing 14 (outer cylinder) and the cylinder 22.
(Inner cylinder).

The main expansion chamber 23 communicates with external water through an exhaust passage 27 formed in a lower portion of the casing 14 and a main exhaust port 29 formed in a boss 28 of the propeller 19. Exhaust passage
24, 25, the main expansion chamber 23, and the exhaust passage 27 form a main exhaust passage.

The main expansion chamber 23 communicates with external water or air through the casing 14, the intermediate member 15, the sub exhaust passage 30 formed in the cylindrical body 22, and the sub exhaust port 31 formed in the rear part of the casing 14. doing.

Here, the sub exhaust port 31 is disposed above the main exhaust port 29.

As shown in FIGS. 1 to 4, the auxiliary exhaust passage 30 has a hole-like passage 32 which is opened on both sides of the cylindrical body 22 and communicates with the main expansion chamber 23, and is provided between the casing 14 and the cylindrical body 22. The first sub-expansion chamber 33, which is formed on the downstream side of the hole-shaped passage 32, and the intermediate member 15
A communication passage 34 opened on both sides of the bottom of the first sub-expansion chamber 33 and located downstream of the first sub-expansion chamber 33, a second sub-expansion chamber 35 formed on the intermediate member 15 and located downstream of the communication passage 34, and an intermediate member 15 The communication passage 36 and the cylindrical body 22 which are opened at the rear portion and located on the downstream side of the second sub-expansion chamber 35
And a third sub-expansion chamber 37 located downstream of the communication passage 36.

The cooling water after cooling the engine 16 is
The exhaust gas is discharged from the 16 exhaust passages 41 to the drain passage 42 of the intermediate member 15, and further discharged from the small holes 43 provided at the bottom of the intermediate member 15 and connected to the drain passage 42 to the first auxiliary expansion chamber 33. The cooling water guided to the first sub-expansion chamber 33 forms a water wall between the casing 14 and the cylindrical body 22, overflows from the upper end of the water wall forming wall 14 a of the casing 14, and flows from an outlet (not shown) to the outside. Exhaust gas and the main exhaust port 29
In accordance with the pressure of the main expansion chamber 23 based on the back pressure at the above, the air flows out of the hole passage 32 into the main expansion chamber 23. A part of the cooling water guided to the drain passage 42 of the intermediate member 15 is directly transferred to the main expansion chamber.
It may be discharged to 23 and dropped around the exhaust pipe 26. At a low speed, the exhaust gas mainly passes through the hole passage 32 from the main expansion chamber 23 toward the water wall in accordance with the exhaust pulse.

Thus, the cylindrical body 22 has a casing at the entire lower end thereof.
Mount rubber 44 provided at the lower end of the inner surface of the water wall 14
(Elastic member).
15 is supported by a mount rubber 45 (elastic member) provided on the lower end surface. The mount rubber 44 is cooled by the water on the water wall, and the mount rubber 45 is water captured by a water receiving portion 46 provided on the outer peripheral portion on the upper end side of the cylindrical body 22 (water falling from the small hole 43 connected to the drain passage 42). ).

FIG. 5 schematically shows the above-described exhaust passage.

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

According to the above embodiment, the engine in which the exhaust pressure of the engine 16 is smaller than the head pressure of the external water acting on the main exhaust port 29
In the low-speed and low-load operation range of 16, the exhaust of the engine 16 is discharged into the air from the sub exhaust port 31, and the exhaust pressure of the engine 16 is higher than the head pressure of the external water acting on the main exhaust port 29. In the high load operation range, the exhaust of the engine 16 is discharged from the main exhaust port 29 into the water.

Since the upper part of the cylinder 22 is attached to the lower part of the engine 16 and the lower part of the cylinder 22 is attached to the lower part of the casing 14 via the mounting rubbers 44 and 45, the upper and lower mounting rubbers 44 and 45 This seals the space, and can prevent the exhaust pulse sound flowing through the cylinder 22 from leaking outside.

Since the upper end of the water wall forming wall 14A is located below the sub-expansion chamber 37 forming the sub exhaust port 31 at the upper rear portion of the casing 14, the accumulated water overflows from the upper end of the water wall forming wall 14A. Flow down. Therefore, even in a low-speed and low-load operation region where the water level is high, the exhaust water can be easily discharged from the sub-exhaust port 31 without blocking the sub-exhaust port 31 formed in the sub-expansion chamber 37.

Water wall forming wall 14A provided inside casing 14 and cylindrical body 2
Since a water wall is formed between the two, the sound insulation effect of the water wall can be improved.

Since a water wall was formed between the casing 14 and the cylindrical body 22, and a space was formed between the water wall forming wall 14A and the casing 14,
The water overflowing from the water wall forming wall 14A can flow into the space, and the radiation sound of the exhaust transmitted to the casing 14 can be effectively shielded in the space.

As described above, when a part of the exhaust passage has a double cylinder structure,
The radiation noise from the casing 14 can be reduced.

Further, in this embodiment, it is possible to prevent the vibration of the cylindrical body 22 from amplifying the internal sound and to emit this as a large idle hole sound from the sub-exhaust port 31, and also reduce the idle hall sound from the sub-exhaust port 31. .

FIG. 6 is a sectional view showing a main part of a second embodiment of the present invention, and FIG.
The figure is a sectional view along the line VII-VII in FIG.

Functional portions of the second embodiment that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

This second embodiment is different from the first embodiment in that the casing 14 is connected to the engine 16 without the intermediate member 15 therebetween, and the exhaust pipe 51 connected directly to the exhaust passage 24 of the engine 16 is formed by a casing. It has been arranged inside the 14.

That is, in the second embodiment, a part of the exhaust passage connected to the engine 16 has a double-cylinder structure including the casing 14 (outer cylinder) and the exhaust pipe 51 (inner cylinder).

The outboard motor 10 has a partition wall provided inside the casing 14.
A water jacket 54 surrounding the exhaust pipe 51 is formed between the exhaust pipe 51 and the outer peripheral wall 53 on the rear side. 55 is a water jacket
Drainage passage for draining 54 overflow water.

Further, the outboard motor 10 is provided with a partition 52 of the casing 14 and a partition.
Another partition 56 disposed on the front side of 52 forms an exhaust expansion chamber 57 located forward of the exhaust pipe 51. The exhaust expansion chamber 57 communicates with the outside via an exhaust passage 58 formed in the lower portion of the casing 14 and an exhaust passage formed in the propeller boss portion. Note that the casing 14 has an exhaust communication passage 59 opened in an upper portion of the partition wall 52. As a result, the exhaust expansion chamber 57 is
It communicates with the upper space of the water jacket 54 via 59, and further communicates with the outside via an idle hole 60 provided in the outer peripheral wall 53 on the rear side of the casing 14. That is, in the low-speed and low-load operation range of the engine 16, the exhaust is discharged from the idle hole 60 through the exhaust expansion chamber 57, the exhaust communication passage 59, and the upper space of the water jacket 54. On the other hand, engine 16
In the high-speed and high-load operation range of
The air is discharged from the propeller boss through the exhaust passage 58.

Thus, in the second embodiment, the exhaust pipe 51 is
The entire periphery of the lower end is supported by a mount rubber 61 (elastic member) provided inside the casing 14, and the entire periphery of the upper end is supported by a mount rubber 62 (elastic member) provided on the lower end surface of the engine 16.

Therefore, also in this case, the vibration of the exhaust pipe 51 is reduced by the mounting rubbers 61 and 62 on the same principle as in the first embodiment.
Or vibration isolation. Further, the exhaust pipe 51 and the mount rubbers 61 and 62 perform a function as a dynamic vibration absorber. Thereby, the radiation noise from the casing 14 can be reduced.

Also, it is possible to prevent the vibration of the exhaust pipe 51 from amplifying the internal sound and releasing the internal sound from the idle hole 60 as a loud idle hole sound.

 FIG. 8 is a schematic view showing a third embodiment of the present invention.

The third embodiment is an example of application to an outboard motor 70 such as a water jet propulsion boat. In the figure, 71 is a hull, 72 is an engine, 73 is a water injection passage, and 74 is an impeller. A part of the exhaust passage 75 connected to the engine 72 has a double cylinder structure including an exhaust expansion case 76 (outer cylinder) and an exhaust pipe 77 (inner cylinder). Further, the front and rear ends of the exhaust pipe 77 are
It is supported by 8, 79 (elastic member). Also in this case, the radiation noise from the exhaust expansion case 76 can be reduced.

 FIG. 9 is a schematic view showing a fourth embodiment of the present invention.

The fourth embodiment is an example of application to a motorcycle 80. Inside the exhaust pipe 82 (outer cylinder) connected to the engine 81, the inner cylinder 83
(Inner cylinder part) to provide a double cylinder structure. Further, the front and rear ends of the inner cylinder 83 are mounted on mount rubbers 84 and 85 (elastic members).
We support in. Also in this case, the radiation noise from the exhaust pipe 82 can be reduced.

[Effects of the Invention] As described above, according to the present invention, in an internal combustion engine for an outboard motor, when at least a part of the exhaust path has a double-cylinder structure, radiation noise from the outer cylinder portion is reduced. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. III
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, FIG. 5 is a schematic view of the exhaust path in FIG. 1, and FIG. 6 is a second embodiment of the present invention. 7 is a sectional view taken along the line VII-VII of FIG. 6, FIG. 8 is a schematic view showing a third embodiment of the present invention, and FIG. 9 is a fourth embodiment of the present invention. It is a schematic diagram which shows an example. 14 ... casing (outer cylinder), 16 ... engine, 22 ...
Cylinder (inner cylinder), 44, 45: Mount rubber (elastic member), 51: Exhaust pipe (inner cylinder), 61, 62: Mount rubber (elastic member), 72: Engine, 76: … Exhaust expansion case (outer cylinder), 77… Exhaust pipe (inner cylinder), 78, 79… Mount rubber (elastic member), 81… Engine, 82 …… Exhaust pipe (outer cylinder), 83 …… Inner cylinder (inner cylinder part), 84, 85 …… Mount rubber (elastic member).

Continuation of the front page (56) References Japanese Utility Model Sho 53-120628 (JP, U) Japanese Utility Model Sho 55-9847 (JP, U) Japanese Utility Model Sho 55-64421 (JP, U) Japanese Utility Model Sho 54-178317 (JP) , U) JP 56-41478 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 7/08-7/12 B63H 21/26

Claims (1)

(57) [Claims] 1. An outboard motor comprising an exhaust path connected to an exhaust port of an engine of an outboard motor, wherein at least a part of the exhaust path is constituted by a double cylinder structure comprising an outer cylinder and an inner cylinder. An exhaust device for an internal combustion engine for use, wherein an outer cylinder portion is attached to a lower portion of the engine, the outer cylinder portion extends downward, and an inner cylinder portion extends downward inside the outer cylinder portion. The upper part is attached to the lower part of the engine, the lower part of the inner cylinder part is attached to the lower part of the outer cylinder part via an elastic member, and water is formed between the inner wall part and the water wall forming wall provided inside the outer cylinder part. A wall is formed, an expansion chamber having an exhaust port is formed at an upper rear portion of the outer cylinder portion, and an upper end of the water wall formation wall is arranged below the expansion chamber, and an outer cylinder portion and a water wall formation wall are formed. An exhaust device for an internal combustion engine for an outboard motor, wherein a space communicating with the outside of the outboard motor is formed therebetween.