JPH0730704B2 - Multi-cylinder 2-cycle natural engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-cylinder two-cycle internal combustion engine used for outboard motors and the like.

[Prior Art] As an exhaust system of a multi-cylinder two-cycle internal combustion engine used for an outboard motor or the like, an exhaust pipe of an internal combustion engine is connected, and a portion of the inside of the exhaust pipe connected to the internal combustion engine is divided by a partition wall. A part that is divided into one divided passage that communicates with one cylinder of the internal combustion engine and the other divided passage that communicates with the other cylinder of the internal combustion engine, and that continues inside the exhaust passage to the two divided passages. Is a tapered collecting passage that contracts toward the exhaust downstream side in a state where both dividing passages are gathered, and the exhaust pressure of the cylinder communicating with one dividing passage is exerted on the cylinder communicating with the other dividing passage. There is something.

According to the exhaust device, the cylinder on one side of the internal combustion engine and the cylinder on the other side communicate with each other due to the existence of the divided passages and the collecting passages, so that the exhaust gas discharged from the cylinder on the one side is communicated with each other. The pressure wave extends from one divided passage to the cylinder on the other side through the collecting passage and the other divided passage. This makes it possible to pressurize the intake air of the cylinder on the other side, prevent the blow-through of the intake air, increase the charging efficiency of the intake air, and improve the output.

[Problems to be Solved by the Invention] By the way, in the above exhaust device, if the partition wall is made long and the length of the divided passage is made long, the medium and low speed output can be improved.

However, in the above conventional exhaust device, the passage area of each divided passage is reduced in a gradient form from the exhaust upstream side to the exhaust downstream side for the convenience of die cutting. Therefore, if the partition wall is lengthened and the length of each divided passage is increased in order to improve the medium-low speed output, the passage area on the exhaust downstream side of the divided passage becomes too small. In this way, when the passage area on the exhaust downstream side of the divided passage becomes too small, there is a disadvantage that the exhaust resistance at high speed with a large amount of exhaust becomes excessive and the high speed output is reduced.

An object of the present invention is to improve both the medium and low speed output and the high speed output at the same time.

[Means for Solving the Problem] The present invention is to connect an exhaust pipe to an internal combustion engine, and a portion of the exhaust pipe connected to the internal combustion engine is divided by a partition wall to i) a cylinder on one side of the internal combustion engine. One of the divided passages that communicates with each other, and ii) the other divided passage that communicates with the cylinder on the other side of the internal combustion engine. In a multi-cylinder two-cycle internal combustion engine in which the exhaust pressure of the cylinder communicating with one of the split passages is exerted on the cylinder communicating with the other of the split passages,
The passage area of each of the divided passages is gradually expanded from the exhaust upstream side to the exhaust downstream side, and the end portion of the partition wall is made to coincide with the portion where the exhaust pipe changes from the expansion to the reduction.

[Operation] According to the present invention, the following effects are obtained.

By "matching the end portion of the partition wall that divides the exhaust pipe with the portion where the exhaust pipe changes from expansion to contraction", the exhaust passage area at the end portion of the partition wall can be increased.

Therefore, the resistance of the exhaust gas is reduced, and the medium / low speed output is improved.

Also, by "reducing the exhaust pipe from the end of the partition wall", the exhaust pressure rises, and the influence of the reflected wave of the exhaust gas of one cylinder on the other cylinder can be increased, and the output at medium and low speeds can be further increased. Is improved.

On the other hand, by adopting such a structure, it is possible to “shorten the length of the partition wall as much as possible with respect to the entire length of the exhaust pipe”, so that at high speed, the influence of the reflected wave of the exhaust gas of one cylinder can be minimized. It can be given to the other cylinder in a short cycle, and high-speed output can be improved.

Therefore, with a very simple structure, switching operation or the like is not required, and medium-low speed output and high-speed output can be improved at the same time.

[Embodiment] FIG. 1 is a side view showing a partially cutaway view of an outboard motor to which the present invention has been applied, and FIG. 2 is a cross-sectional view of essential parts taken along line II-II of FIG.
3 is a sectional view showing the exhaust pipe of FIG. 1, FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3, and FIG. 5 is a diagram showing the effect of the present invention.

The outboard motor 10 has a propulsion unit 14 attached to a hull 11 via a clamp bracket 12 and a swivel bracket 13. The propulsion unit 14 includes a casing 15 and a casing 15
Internal combustion engine 17 mounted on the upper part of the vehicle via exhaust guide plate 16
It consists of The internal combustion engine 17 is a V-type 4-cylinder 2-cycle internal combustion engine, and is covered with a cowling 18. The output of the internal combustion engine 17 is transmitted to the propeller 20 via a drive shaft 19 vertically installed inside the casing 15, and the propeller 20 can be rotated forward or backward by a switching operation of a forward / reverse switching device (not shown). .

An exhaust expansion chamber 21 is formed inside the casing 15. An exhaust pipe 22 connected to the internal combustion engine 17 is arranged inside the expansion chamber 21. The exhaust pipe 22 is provided so as to be joined to the lower surface portion of the exhaust guide plate 16.

The exhaust pipe 22 divides a portion of the exhaust pipe 22 connected to the internal combustion engine 17 by a partition wall 23 into a divided passage 24 and a divided passage 25. The partition wall 23, which is exaggerated in the drawing, has a cross-section that is sharp toward the exhaust gas downstream side due to the drafting gradient (FIG. 4). The divided passage 24 is an exhaust passage 28 of the cylinders 26, 27 located on the left side partitioned by the partition wall 17A of the internal combustion engine 17,
The exhaust guide plate 16 communicates with each other through a passage 29. Also,
The split passage 25 includes cylinders 30, 31 located on the right side of the internal combustion engine 17.
The exhaust passage 32 communicates with the exhaust passage 32 of the exhaust guide plate 16.

The exhaust pipe 22 has a portion following the both passages 24, 25 as a tapered collecting passage 34 that contracts toward the exhaust downstream side in a state where the both passages 24, 25 are collected. Also, the exhaust pipe 22
Is a tail passage 35 that opens to the expansion chamber 21 by gradually expanding the portion following the collecting passage 34 toward the exhaust downstream side. The exhaust gas from the left cylinders 26 and 27 of the internal combustion engine 17 and the exhaust gas from the right cylinders 30 and 31 are expanded at predetermined timings through the respective divided passages 24 and 25, the collecting passage 34, and the tail passage 35 of the exhaust pipe 22. After being discharged into the chamber 21, expanded and attenuated, it is discharged into the outside water from an unillustrated underwater exhaust passage provided in the boz portion of the propeller 20.

Here, when the exhaust gas is discharged from the left cylinders 26 and 27, the pressure wave of the exhaust gas discharged from the exhaust cylinders 26 and 27 is divided from the dividing passage 24 to the collecting passage 34 and the dividing passage 25 to the right cylinder 30, It reaches 31. As a result, the intake air of the right cylinder 30, 31 is pressurized,
The blow-through can be prevented, the charging efficiency of intake air can be increased, and the output of the internal combustion engine 17 can be improved. On the other hand, when the exhaust gas is discharged from the right cylinders 30 and 31, the pressure wave of the exhaust gas discharged from the cylinders 30 and 31 passes from the split passage 25 to the collecting passage 34 and the split passage 24 to the left cylinders 26 and 27. Up to. This makes it possible to pressurize the intake air of the left cylinders 26 and 27, prevent the blow-by of the intake air, increase the intake air charging efficiency, and improve the output of the internal combustion engine 17.

Further, the exhaust pipe 22 expands the passage area of each of the divided passages 24 and 25 in a gradient form from the exhaust upstream side to the exhaust downstream side. That is, as shown in FIGS. 3 and 4, the passage areas of the respective divided passages 24 and 25 are located on the most upstream side of the exhaust passage and are connected to the passages 29 and 33 of the exhaust guide plate 16, which are the passage portions 24A, When the area of 25A is S1 and the area of the passage portions 24B and 25B located on the most downstream side of the exhaust gas and connected to the collecting passage 34 is S2, the area gradually increases from S1 to S2.

Further, the portion 101 where the exhaust pipe 22 turns from the expansion to the reduction is made to coincide with the terminal end portion 102 of the partition wall 23.

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

During operation of the outboard motor 10, the internal combustion engine 17 is driven to drive the exhaust ports 26 of the left cylinders 26 and 27 and the right cylinders 30 and 31, respectively.
Exhaust gas flowing out from A, 27A, 30A, 31A is, at a predetermined timing, in the left and right exhaust passages 28, 30, passages 29, 33 of the exhaust guide plate 16, divided passages 24, 25 of the exhaust pipe 22, and a collecting passage. It is discharged into the expansion chamber 21 through the tail passage 35 and the tail passage 35.

At this time, as described above, the exhaust pressure of the left cylinders 26 and 27 communicating with the one dividing passage 24 extends to the right cylinders 30 and 31 communicating with the other dividing passage 25, and Pressurize the intake air. In addition, the right cylinder communicating with the other split passage 25
The exhaust pressures of 30 and 31 reach the left cylinders 26 and 27 communicating with one of the divided passages 25 and pressurize the intake air of the cylinders 26 and 27.
This prevents the intake air from blowing through the cylinders 26, 27, 30, and 31 to increase the intake charging efficiency and improve the output of the internal combustion engine 17.

Then, the exhaust pipe 22 has the following effects (1) to (3).

"Exhaust pipe 22 part 101 that changes from expansion to contraction and exhaust pipe 2
By matching the end portions 102 of the partition wall 23 that divide the two, the exhaust passage area of the end portion 102 of the partition wall 23 can be expanded.

Therefore, the resistance of the exhaust gas is reduced, and the medium / low speed output is improved.

Further, by "reducing the exhaust pipe 22 from the terminal end 102 of the partition wall 23", the exhaust pressure rises, and the influence of the reflected wave of the exhaust gas of one cylinder on the other cylinder can be increased, and The output at medium and low speeds is improved.

On the other hand, by adopting such a structure, "the length of the partition wall 23 can be made as short as possible with respect to the entire length of the exhaust pipe 22", so at high speed, the influence of the reflected wave of the exhaust gas of one cylinder Can be applied to the other cylinder in a cycle as short as possible, and high-speed output can be improved.

Therefore, with a very simple structure, switching operation or the like is not required, and medium-low speed output and high-speed output can be improved at the same time.

FIG. 5 is a diagram showing the relationship between the rotational speed N of the internal combustion engine, the output P, and the torque T, the solid line shows the result using the exhaust pipe 22, and the broken line shows the result using the exhaust pipe of the conventional structure. Is. According to FIG. 5, the high speed output,
It is recognized that the medium / low speed output and the medium / low speed torque can be improved without causing a decrease in the high speed torque.

[Advantages of the Invention] As described above, according to the present invention, it is possible to improve both the medium and low speed output and the high speed output.

[Brief description of drawings]

FIG. 1 is a side view showing an outboard motor to which the present invention has been applied, partially broken away, and FIG.
3 is a sectional view showing the exhaust pipe of FIG. 1, FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3, and FIG. 5 is a diagram showing the effect of the present invention. 17: Internal combustion engine, 22: Exhaust pipe, 23: Partition wall, 24, 25
...... Split passages, 26, 27 ...... One side cylinder, 30, 31 ...... Other side cylinders, 34 ...... Collecting passage, 101 ...... The part that changes from expansion to contraction, 102 ...... End part.

Claims (1)

[Claims] 1. An exhaust pipe is connected to an internal combustion engine, and a portion of the inside of the exhaust pipe connected to the internal combustion engine is divided by a partition wall. I) One divided passage communicating with one cylinder of the internal combustion engine. Ii) It is divided into the other divided passage communicating with the cylinder on the other side of the internal combustion engine, and the portion inside the exhaust passage that continues to the two divided passages is connected to the exhaust downstream side with the divided passages gathered together. In a multi-cylinder two-cycle internal combustion engine, the passage area of each divided passage is defined as a tapered collecting passage that contracts toward each other, and exerts exhaust pressure of a cylinder communicating with one divided passage on a cylinder communicating with the other divided passage. A multi-cylinder two-cycle internal combustion engine, characterized in that it expands in a gradient form from the exhaust upstream side to the exhaust downstream side, and the portion where the exhaust pipe turns from expansion to contraction is made to coincide with the end portion of the partition wall.