JPH0526922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust system for an outboard motor, and more particularly to an exhaust system for an outboard motor that improves low-speed stability of an internal combustion engine and reduces exhaust noise.

(Prior technology) As an exhaust system for an outboard motor, an exhaust pipe is provided that is connected to the internal combustion engine mounted on the top of the case, and the exhaust pipe discharges exhaust gas into the expansion chamber inside the case. At high speeds, some exhaust gases are discharged from the main exhaust passage through an underwater exhaust hole formed in the underwater part of the case or in the propeller boss connected to the case, rather than through an idle hole that exhausts exhaust gas directly into the air from a passage.

This type of exhaust device has two passages for discharging from the exhaust pipe to the expansion chamber.
No. 162397 was issued. This has the problem that the expansion chamber and the atmosphere are connected only through the idle hole, and exhaust noise easily leaks through the idle hole.

Conventional approaches to solving this problem have been to lengthen the exhaust passage around the idle hole, improve performance by utilizing reflected waves, improve low-speed stability especially at low speeds, or attenuate the exhaust gas flow. ,
Efforts are being made to reduce exhaust noise, especially at low speeds. As a means to lengthen the exhaust passage at low speeds, there is a method in which a labyrinth through which exhaust gas passes is formed in the exhaust guide on which the internal combustion engine is mounted or in the case itself constituting the outboard motor.

(Problems to be Solved by the Invention) Incidentally, with some outboard motors, internal combustion engines with different outputs may be mounted in the same case. In this case, if the maze through which the exhaust gas passes is formed in the exhaust guide on which the internal combustion engine is mounted or in the case itself that makes up the outboard motor, the length of the exhaust passage will not be appropriate for the internal combustion engine. However, it was difficult to obtain optimal performance, and the exhaust noise at low speeds could not be effectively reduced.

This invention was made in view of the above circumstances, and it is possible to replace the exhaust pipe by providing a labyrinth that communicates the expansion chamber inside the case with the atmosphere side of the case in the exhaust pipe that is removably installed in the case. It is an object of the present invention to provide an exhaust system for an outboard motor, which can obtain optimum performance according to the internal combustion engine by simple means, and which can reduce exhaust noise at low speeds.

(Means for Solving the Problems) In order to solve the above problems, the present invention connects an exhaust pipe to the internal combustion engine mounted on the upper part of the case,
A main exhaust passage is provided for discharging exhaust gas from the exhaust passage of the exhaust pipe to an expansion chamber formed in the case, and discharging the exhaust gas from the expansion chamber into the water through an underwater exhaust hole, and from the expansion chamber formed in the case. In an exhaust system for an outboard motor having a sub-exhaust passage for discharging air into the air from an air exhaust hole, a side wall forming an exhaust passage of an exhaust pipe constituting a part of the main exhaust passage is provided with air from an expansion chamber of the case. The present invention is characterized in that a labyrinth communicating with the air exhaust hole is formed to constitute a part of the sub-exhaust passage, and that the exhaust pipe is formed separately from the case and is detachably provided.

(Function) In this invention, an exhaust pipe formed separately from the case in which the internal combustion engine is mounted is made removable, and an exhaust passage is formed in the exhaust pipe to guide exhaust gas from the internal combustion engine to the expansion chamber in the case. A labyrinth communicating from the expansion chamber to the air exhaust hole side of the case is formed on the formed side wall. Therefore, when internal combustion engines with different outputs are installed in the same case using an outboard motor, the length of the exhaust passage can be changed depending on the internal combustion engine by simply replacing the exhaust pipe.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a partially cutaway side view of an outboard motor to which the present invention is applied, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. 3 is an enlarged cross-sectional view showing how the exhaust pipe is installed. .

In the figure, reference numeral 1 denotes a hull 1 of a small boat, and a clamp bracket 3 is fixed to a stern plate 2 of the hull 1. A swivel bracket 4 is attached to the clamp bracket 3 so as to be movable up and down, and an outboard motor main body 5 is attached to the swivel bracket 4 so as to be pivotable in the left and right directions.

The outboard motor main body 5 has an upper case part 6 and a lower case part 7.
an internal combustion engine unit 10 mounted on the upper part of the upper case 6 via an exhaust guide 9;
It is made up of. Upper case part 6 and lower case part 7
are integrally connected, and these upper case parts 6
A drive shaft 11 is provided passing through the inside of the lower case portion 7. A propeller 12 is installed in the lower case part 7.
is installed, and the rotational force obtained by the internal combustion engine 13 is transmitted to the propeller 12 via the drive shaft 11.
is transmitted to enable the propeller 12 to rotate forward or backward.

A water pump 14 is disposed in the lower part of the upper case part 6, and this water pump 14 is driven by the rotation of the drive shaft 11. The water pump 14 sucks outside water through a water suction pipe 15 provided inside the lower case section 7, and a water supply pipe 16 provided inside the upper case section 6.
Cooling water is supplied to the water jacket of the internal combustion engine 13 through an inflow path (not shown) formed in the exhaust guide 9.

An exhaust passage 17, a first expansion chamber 18, and a second expansion chamber 19 are formed in the exhaust guide 9, and the first expansion chamber 18 and the second expansion chamber 19 communicate with each other through a throttle hole 20.

A cylindrical partition wall 21 is vertically formed inside the upper case portion 6, and the partition wall 21 defines an expansion chamber 22 on the inside and a cooling chamber 23 on the outside.

From the expansion chamber 22, although not shown, the propeller 12
A main exhaust passage communicating with the boss is provided. At medium and high speeds, the negative pressure generated at the rear of the propeller 12 causes exhaust gas to flow into the water through the main exhaust passage from the internal combustion engine 13, the exhaust pipe 24, the expansion chamber 22, and to the underwater exhaust hole (not shown) underwater. be discharged.

The cooling chamber 23 communicates with the second expansion chamber 19 of the exhaust guide 9, and the cooling water discharged from the water jacket of the internal combustion engine 13 is drained through a drainage channel (not shown) formed in the exhaust guide 9. It is discharged to the cooling chamber 23 via. At this time, the partition wall 21 is cooled by the drainage water, indirectly cooling the expansion chamber 22, and the water is discharged into the outside water.

An exhaust pipe 24 is disposed within the expansion chamber 22, and the exhaust pipe 24 has a flange 25 joined to the lower surface of the exhaust guide 9 as shown in FIG. A tightening bolt 26 is screwed onto the exhaust guide 9 and is detachably provided.

The exhaust pipe 24 has an exhaust passage 2 that communicates the exhaust passage 17 of the exhaust guide 9 with the expansion chamber 22 through its side wall 27.
8 is formed.

A labyrinth 29 is formed in the side wall 27 of the exhaust passage 28, which connects the expansion chamber 22 and the first expansion chamber 18 of the exhaust guide 9.
are in communication. This maze 29 is an expansion chamber 22
A straight line part 29a extends upward from the bottom of the side wall in communication with the side wall, a straight line part 29b bends at the upper part and extends downward, and the first expansion chamber 18 of the exhaust guide 9 bends at the lower part and extends upward. Straight section 2 connected to
9c. Exhaust gas discharged from the exhaust port of the internal combustion engine 13 is guided to the expansion chamber 22 via the exhaust passage 17 of the exhaust guide 9 and the exhaust passage 28 of the exhaust pipe 24, and is expanded. This exhaust gas is throttled in the maze 29 of the exhaust pipe 24 and guided to the first expansion chamber 18 of the exhaust guide 9, and then enters the atmosphere from the second expansion chamber 19 of the exhaust guide 9 through the throttle hole 20 and the air exhaust hole 30. It is beginning to be excreted.

That is, the area from the maze 29 of the exhaust pipe 24 to the air exhaust hole 30 becomes a sub-exhaust passage connecting the expansion chamber 22 and the outside of the outboard motor main body 5. The length of this maze 29 affects the length of the sub-exhaust passage in the exhaust system, which is different from the main exhaust passage, and contributes to muffling the low to high frequencies of the exhaust gas. Back pressure can be reduced, and the noise reduction effect in the low frequency range is large.

Furthermore, regarding performance improvement due to reflected waves, the length of the sub-exhaust passage independently contributes to the same extent as the length of the main exhaust passage. Setting this length appropriately has the effect of improving performance.

In this embodiment, the length of the maze 29 is the length of the exhaust passage 28.
It is set to approximately twice the length. This exhaust pipe 24
The length of the maze 29 can be changed to any desired length by increasing or decreasing the straight portion according to the output of the internal combustion engine 13, and the cross-sectional area of the passage can also be changed arbitrarily.

Next, the operation of this embodiment will be explained.

When the outboard motor is in operation, the internal combustion engine 13 drives the drive shaft 11 to rotate and drive the propeller 12 . This rotation of the drive shaft 11 drives the water pump 14, and the cooling water sucked in by the water suction pipe 15 is sent to the internal combustion engine 13 via the water pipe 16.

Exhaust gas discharged by driving the internal combustion engine 13 is discharged into the expansion chamber 22 via the exhaust passage 17 of the exhaust guide 9, the exhaust passage 26 of the exhaust pipe 24, and is attenuated by expansion. moreover,
Exhaust gas is discharged from the expansion chamber 22 into the water through a main exhaust passage communicating with a boss portion of the propeller 12 (not shown) due to negative pressure generated at the rear of the propeller 12 at medium and high speeds.

On the other hand, at low speeds, exhaust gas flows into the expansion chamber 22.
From the straight parts 29a, 20 of the maze 29 of the exhaust pipe 24
b, 29c, the back pressure is reduced due to the resistance of the pipe and the noise is muffled, and the first exhaust guide 9
It is sent to the expansion chamber 18 and expanded again. Then, the exhaust gas is compressed through the throttle hole 20, and the second expansion chamber 1
After being expanded at 9, it is discharged into the atmosphere from an air exhaust hole 30 formed in the lower case part 6.

Exhaust gas is attenuated by repeated compression and expansion as it passes through this sub-exhaust passage, thereby muffling the sound, and by utilizing reflected waves, performance is improved.

Incidentally, although the case 8 of the outboard motor main body 5 is the same, an internal combustion engine 13 with a different horsepower may be installed.In this case, the tightening bolt 26 is removed and the exhaust pipe 24 is replaced at the same time, and the internal combustion The exhaust pipe 24 is optimal for the 13. That is, the performance and noise reduction effect of the internal combustion engine 13 are affected by the length of the exhaust passage.
Therefore, depending on the horsepower of the internal combustion engine 13, the exhaust pipe is selected so that performance corresponding to the engine can be obtained and idling noise can be reduced.

FIG. 5 is a side view showing essential parts of an outboard motor showing another embodiment.

In this embodiment, the exhaust pipe 24 is detachably installed in the exhaust guide 9, and the exhaust passage 26 communicates with the exhaust passage 17 of the exhaust guide 9 and the expansion chamber 22 in the upper case 6. A labyrinth 29 is formed on the side wall 27 of the exhaust pipe 24, and the labyrinth 29 includes an axially elongated linear part 29d and an expansion chamber 29e formed integrally with the linear part 29d at the upper part of the side wall 27.
The expansion chamber 29e is in communication with the first expansion chamber 18 of the exhaust guide 9.

Therefore, the exhaust gas generated by the drive of the internal combustion engine 13 is discharged from the exhaust passage 17 of the exhaust guide 9, and is discharged from the exhaust passage 28 of the exhaust pipe 24 to the expansion chamber 22, where it is expanded. The expanded exhaust gas becomes a back pressure at the straight part 29d of the maze 29 of the exhaust pipe 24, and the exhaust gas
It is guided to the expansion chamber 29e of the exhaust guide 9 and the expansion chamber 18 of the exhaust guide 9, and is expanded again. This expanded exhaust gas is throttled by the throttle hole 20, guided to the second expansion chamber 19, and discharged into the atmosphere from the air exhaust hole 30.

In this way, in the exhaust system, the exhaust gas is expanded and compressed repeatedly, and the exhaust noise is successively attenuated and effectively reduced. The exhaust pipe 24 ensures a passage for compressing the exhaust gas in the exhaust passage and an exhaust passage for expanding the exhaust gas. In other words, for outboard motors with limited installation space,
Expansion chamber 22 with a necessary capacity corresponding to the internal combustion engine 13
is formed by the exhaust pipe 24, and is useful in cases where securing an expansion chamber in the upper case portion 6 is limited, such as in the case of an outboard motor for a small boat.

(Effects of the Invention) As described above, the present invention makes it possible to attach and detach an exhaust pipe formed separately from the case in which the internal combustion engine is mounted, and the exhaust pipe guides exhaust gas from the internal combustion engine to the expansion chamber. The side wall that forms the passage has a labyrinth that connects the expansion chamber to the air exhaust port side of the case, so when using an outboard engine, when internal combustion engines with different outputs are installed in the same case, it is difficult to connect the exhaust pipe. The length of the exhaust passage can be changed depending on the internal combustion engine by simply replacing it. This makes it possible to obtain optimum performance for the internal combustion engine by simply replacing the exhaust pipe, and also to reduce exhaust noise during idling and at low speeds.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of an outboard motor to which the present invention is applied, FIG. 2 is a sectional view taken from FIG. FIG. 4 is a side view showing essential parts of an outboard motor showing another embodiment. 5... Outboard motor body, 6... Upper case part, 7...
Lower case part, 9...exhaust guide, 17...exhaust passage, 18...first expansion chamber, 19...second expansion chamber,
21... Bulkhead, 22... Expansion chamber, 24... Exhaust pipe, 28... Exhaust passage, 29... Maze.

Claims (1)

[Claims] 1. An exhaust pipe is connected to an internal combustion engine mounted on the upper part of the case, exhaust gas is discharged from an exhaust passage of the exhaust pipe to an expansion chamber formed inside the case, and the exhaust gas is discharged from the expansion chamber into water. In an exhaust system for an outboard motor, the outboard motor has a main exhaust passage for discharging water from an exhaust hole into the water, and a sub-exhaust passage for discharging air from the expansion chamber into the air from an air exhaust hole formed in a case. A labyrinth communicating from the expansion chamber to the air exhaust hole side of the case is formed on a side wall forming an exhaust passage of an exhaust pipe constituting the part, forming a part of the sub-exhaust passage; An exhaust system for an outboard motor, characterized in that it is formed separately from a case and is removably provided. 2. The exhaust system for an outboard motor according to claim 1, wherein the maze of exhaust pipes has an expansion chamber.