JP2929673B2 - Outboard exhaust system - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to an exhaust system for an outboard motor equipped with a multi-cylinder engine, and more particularly to a ship for preventing disadvantageous interference of exhaust. Regarding the exhaust position of the outer unit.

(Prior Art) In an outboard multi-cylinder engine, as shown in FIG.
A vertical engine in which the crankshaft 4 is vertically arranged is generally used. Also, each exhaust port (first exhaust port 5, second exhaust port 6, third exhaust port 7) of each cylinder (first cylinder 1, second cylinder 2, third cylinder 3) is a single exhaust passage. 8, the exhaust from each of the cylinders 1, 2, 3 passes through the exhaust passage 8, and is discharged from an exhaust outlet 9 of the exhaust passage 8 into a drive shaft housing (not shown). .

In a multi-cylinder engine, the cycle process generally differs for each cylinder. For example, in a two-cycle multi-cylinder engine shown in FIG.
The cylinder 2 and the third cylinder 3 explode and compress (the state shown in FIG. 4), and the second cylinder 2 and the third cylinder 3 exhaust and scavenge during the explosion and compression process of the first cylinder 1. , The cran shaft 4 rotates smoothly. Where the sign
Reference numeral 11 denotes a first piston, 12 denotes a second piston, 13 denotes a third piston, and reference numeral 10 denotes a scavenging port.

(Problems to be Solved by the Invention) In the above-described two-cycle multi-cylinder engine, during the exhaust / scavenging process of the first cylinder 1, the exhaust gas in the exhaust passage 8 flows from the first exhaust port 5 to the first cylinder 1. Inflow (backflow)
The exhaust gas flowing out of the first exhaust port 5 may flow in the exhaust passage 8 toward the second cylinder 2 and the third cylinder 3.

In such a case, the combustion of the first cylinder 1 becomes incomplete and the temperature of the engine becomes high, which may cause a decrease in output or a problem in engine strength.

The present invention has been made in consideration of the above circumstances, and has as its object to provide an outboard motor exhaust device that can prevent backflow of exhaust gas and prevent the engine from becoming hot.

[Configuration of the invention]

(Means for Solving the Problems) According to the present invention, each exhaust port of a multi-cylinder engine opens in the same exhaust passage, and the exhaust passage of the first cylinder closest to the exhaust outlet of the exhaust passage is provided in the exhaust passage. An exhaust control plate is provided in the vicinity of the exhaust port and upstream of the exhaust gas flowing in the exhaust passage so as to be able to advance and retreat, and the exhaust control plate is provided in the exhaust passage when the exhaust port of the first cylinder is opened. Characterized by being operated to advance to

(Effects) Therefore, according to the exhaust device for an outboard motor according to the present invention, the exhaust control plate advances into the exhaust passage when the exhaust port of the first cylinder is opened, so that the exhaust in the exhaust passage is reduced by the exhaust control plate. Accordingly, it is possible to prevent the gas from flowing into the exhaust port of the first cylinder (backflow). For this reason, the combustion of the first cylinder is improved, and it is possible to prevent the engine from becoming hot.

(Example) Below. An embodiment of the present invention will be described with reference to the drawings.

1 (A) and 1 (B) are schematic sectional views of an engine showing one embodiment of an outboard motor exhaust system according to the present invention, and FIGS. 2 (A) and (B) are FIGS. 1 (A) and 1 (B). FIG. 2 is a perspective view of an engine corresponding to each of FIGS.

As shown in FIGS. 2A and 2B, the multi-cylinder engine 20 of the outboard motor is generally a vertical engine in which a crankshaft 24 is vertically arranged. The cylinder 21, the second cylinder 22, and the third cylinder 23 are provided side by side. The first piston 25 is provided in the first cylinder 21 and the second cylinder
The second piston 26 is accommodated in the cylinder 22, and the third piston 27 is accommodated in the third cylinder 23. These first, second, and third pistons 25, 26, and 27 are connected to a cran shaft 24 via a connecting rod 28.

Each of the first cylinder 21, the second cylinder 22, and the third cylinder 23 has a first cylinder.
Exhaust port 29, second exhaust port 30, and third exhaust port 3
1 are formed respectively. In addition, each of the first cylinder 21 and the second cylinder 22
A first scavenging port 32, a second scavenging port 33, and a third scavenging port 34 are formed in the third cylinder 23, respectively. These scavenging ports 32, 33 and 34 are connected to the first scavenging port 32.
As shown in FIG. 1, the scavenging passage 35 (FIG. 1A)
And (B)) through the crankcase 36. Accordingly, fresh air flowing into the crankcase 36 passes through the first scavenging port 32, the second scavenging port 33, and the third scavenging port 34, and enters the first cylinder 21, the second cylinder 22, and the third cylinder 23, respectively. It is provided so that it can be supplied.

In addition, the first exhaust port 29, the second exhaust port 30, and the third
The exhaust port 31 is communicated with one exhaust passage 37 formed in the cylinder block 39. Therefore, the exhaust gas discharged from each of the first exhaust port 29, the second exhaust port 30, and the third exhaust port 31 merges in the exhaust passage 37, and from the exhaust outlet 38 in the exhaust passage 37, a drive shaft (not shown) Discharged into the housing.

That is, in the state shown in FIG. 2A, the first cylinder 21 is in the compression / explosion step, and the first exhaust port 29 is closed by the first piston 25, but the second cylinder 22 and the third cylinder
Reference numeral 23 denotes an exhaust process in which the second exhaust port 30 and the third exhaust port 31 are open.
And, exhaust gas is discharged from the third exhaust port 31 into the exhaust passage 37. In the state shown in FIG. 2 (B), the second cylinder
22 and the third cylinder 23 are in the explosion / compression step, and the second exhaust port 30 and the third exhaust port 31 are closed by the second piston 26 and the third piston 27, respectively. In the exhaust / scavenging process, the first exhaust port 29 is open, and the exhaust is discharged from the first exhaust port 29 into the exhaust passage 37.

By the way, in the exhaust passage 37, an exhaust valve as an exhaust control plate is provided upstream of the first exhaust port 29 in the exhaust gas flow direction.
40 are arranged to be able to advance and retreat. As shown in FIGS. 1A and 1B, the exhaust valve 40 is supported by a valve connecting rod 41, and the valve connecting rod 41 is connected to the cran shaft 24 via an eccentric bush 42. That is, the eccentric bush 42 is fixed to the crankshaft 24, and the large end 43 of the valve connecting rod 41 is rotatably fitted around the outer periphery of the eccentric bush 42.

The valve connecting rod 41 is connected to the first
When the cylinder 21 is in the compression / explosion step shown in FIG. 1 (A) and the first piston 25 is at the top dead center, the exhaust valve 40 is retracted to the outside of the exhaust passage 37, and the first cylinder 21 Fig. 1 (B)
When the first piston 25 is at the bottom dead center and the first exhaust port 29 is open in the exhaust / scavenging process shown in FIG. 5, the exhaust valve 40 is advanced into the exhaust passage 37 to make the exhaust passage 37 thin. It is configured to

 Next, the operation and effect will be described.

As shown in FIG. 2A, the first cylinder 21 is in the compression / explosion step, the first exhaust port 29 is closed by the first piston 25, and the second cylinder 22 and the third cylinder 23 are closed. In the exhaust process, the second exhaust port 30 and the third exhaust port
When the valve 31 is open, the exhaust valve 40 is closed as shown in FIG.
As shown in FIG. Therefore, at this time, exhaust gas is discharged from the second exhaust port 30 of the second cylinder 22 and the third exhaust port 31 of the third cylinder 23 into the exhaust passage 37, and no exhaust gas is exhausted from the first exhaust port 29. The exhaust gas in the exhaust passage 37 is exhausted from the exhaust outlet 38 without being obstructed by the exhaust valve 40.

As shown in FIG. 2 (B), when the second cylinder 22 and the third cylinder 23 are in the explosion / compression step, the second exhaust port
30 and the third exhaust port 31 are closed, and the first cylinder
When 21 is in the exhaust / scavenging process and the first exhaust port 29 is open, the control valve 40 advances into the exhaust passage 37 as shown in FIG. 1 (A). At this time, the exhaust gas is exhausted only from the first exhaust port 29 into the exhaust passage 37. In the exhaust passage 37, the second exhaust port 30 and the third exhaust port The exhaust gas discharged from the exhaust port 31 is flowing.

Since the exhaust gas discharged from the second exhaust port 30 and the third exhaust port 31 is blocked by the presence of the control valve 40, the exhaust gas does not flow (backflow) into the first exhaust port 29 of the first cylinder 21. Conversely, the first exhaust port
Exhaust exhausted from the exhaust pipe 29 is also blocked by the exhaust valve 40 and does not flow in the exhaust passage 37 toward the second exhaust port 30 and the third exhaust port 31, but is smoothly exhausted from the exhaust outlet 37. From these facts, the first cylinder 21
, The engine output increases, and the engine temperature can be prevented from rising.

In addition, independent exhaust passages are provided for each of the first exhaust port 29 of the first cylinder 21, the second exhaust port 30 of the second cylinder 22, and the third exhaust port 31 of the third cylinder 23 to prevent exhaust backflow and interference. In this embodiment, the exhaust passage 37 is shared by the exhaust ports 29, 30 and 31, and the exhaust valve 40 and the valve connecting rod 41
The cost can be reduced because of only providing.

Note that the exhaust valve 40 in the above embodiment may be formed such that the distal end portion is made thinner and gradually wider as in the exhaust valve 44 shown in FIG.

〔The invention's effect〕

As described above, according to the exhaust device for an outboard motor according to the present invention, each exhaust port of the multi-cylinder engine opens in the same exhaust passage, and the exhaust passage is most closely connected to the exhaust outlet of the exhaust passage. An exhaust control plate is provided in the vicinity of the exhaust port of the adjacent first cylinder and upstream of the exhaust gas flowing in the exhaust passage so as to be able to advance and retreat, and the exhaust control plate is connected to the exhaust port of the first cylinder. When the engine is opened, it is operated so as to advance into the exhaust passage, so that exhaust gas in the exhaust passage can be prevented from flowing back into the exhaust port of the first cylinder. It can be prevented beforehand.

[Brief description of the drawings]

1 (A) and 1 (B) are schematic sectional views of an engine showing an embodiment of an outboard motor exhaust device according to the present invention, and FIGS. 2 (A) and (B) are FIGS. 1 (A) and 1 (B). FIG. 3 (A) is a perspective view of the engine corresponding to FIG.
And FIG. 9B is a partial view showing a modified example of the control valve shown in FIG.
FIG. 4 is a perspective view of an engine showing a conventional exhaust device for an outboard motor. 20 ... engine, 21 ... first cylinder, 22 ... second cylinder, 23
... Third cylinder 25, first piston 29, first exhaust port 30, second exhaust port 31, third exhaust port 31
37 ... exhaust passage, 38 ... exhaust outlet, 40 ... exhaust valve,
41 …… Valve connecting rod, 42 …… Eccentric bush.

Claims (1)

(57) [Claims] 1. An exhaust port of a multi-cylinder engine opens in the same exhaust passage, and the exhaust passage has a vicinity of the exhaust port of a first cylinder closest to an exhaust outlet of the exhaust passage, An exhaust control plate is provided upstream and downstream of the exhaust gas flowing in the exhaust passage so as to advance and retreat, and the exhaust control plate is operated so as to advance into the exhaust passage when the exhaust port of the first cylinder is opened. An exhaust device for an outboard motor.