JPS6332329Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention relates to an outboard motor. Specifically, the invention is a boat that discharges engine exhaust gas into the water during high-speed operation, and discharges the engine exhaust gas into the atmosphere during low-speed operation. This relates to the structure of the exhaust tube of the external engine.

FIG. 1 shows a conventional outboard motor.

During high-speed operation, this outboard motor directs exhaust gas from the engine 1 to the lower end opening 2a of the exhaust tube 2 and the expansion chamber 3 of the drive shaft housing 3.
a. Exhaust passage 6 formed in the upper side wall 2b of the exhaust tube 2 to discharge exhaust gas from the engine 1 into the water via the unillustrated exhaust passage of the gear case 4 and the propeller boss 5 during low-speed operation.
The air is discharged into the atmosphere through a hole 7 formed in the upper rear wall of the drive shaft housing 3. In addition, this outboard motor cools the engine by taking in cooling water from a cooling water intake port 4a formed in the gear case 4, and then allows the cooling water to fall from the engine holder 8 into the expansion chamber 3a. The gas is discharged into the water via an exhaust passage and a propeller boss 5 (not shown).

By the way, in such an outboard motor, the exhaust passage 6
is simply a hole bored in the exhaust tube 2. Therefore, the cooling water falling into the expansion chamber 3a is sucked into the combustion chamber of the engine 1 through the exhaust passage 6 due to the pulsation of the exhaust gas.
This has sometimes caused an adverse effect on the engine. This was particularly noticeable when the lower end opening 2a of the exhaust tube 2 was submerged in water, that is, during low-speed operation.

In view of the above-mentioned circumstances, the present invention aims to provide an outboard motor that can maintain a predetermined performance of the engine.

In order to achieve the above object, in this invention, a spiral pipe is integrally embedded in the peripheral wall of the exhaust tube to form an exhaust passage, and the length of the exhaust passage is ensured so that the cooling water can flow through the exhaust. This prevents it from entering the tube.

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 2 shows an exhaust tube used in the outboard motor according to the present invention. This exhaust tube 11 has a pipe 12 wound a plurality of times embedded in its upper peripheral wall 11a, and a lower end 1 of this pipe 12.
2a opens downward on the outer surface of the circumferential wall 11a, and the upper end 12b of the pipe 12 opens on the outer surface of the circumferential wall 11a.
It is open on the inner surface. In order to manufacture such an exhaust tube 11, in the embodiment, a previously prepared spiral pipe 12 is placed in an appropriate manner in a mold for the exhaust tube, and then molten metal is poured into the mold. An exhaust tube 11 integrated with a pipe 12 is obtained. Therefore, in this embodiment, the pipe 12 forms an exhaust passage 13 having a sufficient length.
And this exhaust tube 11 is the third
As shown in the figure, it is installed in the engine holder 8 instead of the exhaust tube 2 of the outboard motor in FIG.

In the outboard motor in which the exhaust tube 11 is installed in this manner, engine exhaust gas discharged into the exhaust tube 11 during low-speed operation is guided into the pipe from one end 12b of the pipe 12, and the exhaust passage 13 is The exhausted exhaust gas is discharged from the lower end 12a of the pipe 12 to the outside of the exhaust tube 11, and the subsequent exhaust gas is discharged into the atmosphere through the hole 7 of the drive shaft housing 3. At this time, in the embodiment, the exhaust passage 13 is formed in a spiral shape as described above, and the exhaust passage 13
The inner opening 13a of the exhaust tube 11
is formed so as to be located above the outer surface side opening 13b of the exhaust passage 13, so that the cooling water that has fallen into the expansion chamber 3a due to the pulsation of exhaust gas is surely prevented from entering the exhaust tube 11. To prevent. Therefore, even during low-speed operation, cooling water is not sucked into the combustion chamber of the engine 1.

As explained above, in the present invention, since the exhaust passage is constituted by a pipe, a sufficient length of the exhaust passage can be ensured, and therefore, the cooling water flows into the combustion chamber through the exhaust tube. There is no inhalation, and stable engine performance can be maintained at all times. Further, since the exhaust tube used in the present invention forms an exhaust gas exhaust passage by integrally embedding a pipe in its peripheral wall, the exhaust passage is extremely easy to manufacture.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of a conventional outboard motor, Fig. 2 is a conceptual vertical cross-sectional view of an exhaust tube used in the present invention, and Fig. 3 is an illustration of an outboard motor according to the present invention. FIG. 2 is a partially cutaway side view showing an example. DESCRIPTION OF SYMBOLS 1...Engine, 11...Exhaust tube, 11a...Upper peripheral wall, 12...Pipe, 12
a...lower end, 12b...upper end, 13...exhaust passage, 13a...inner side opening, 13b...outer side opening.

Claims (1)

[Scope of utility model registration request] During high-speed operation, engine exhaust gas is discharged into the water through the bottom opening of the exhaust tube.
In an outboard motor that, during low-speed operation, exhaust gas from the engine is discharged into the atmosphere through an exhaust passage formed in the upper side wall of the exhaust tube, the exhaust tube has a spiral pipe embedded in its upper peripheral wall. An outboard motor characterized in that the exhaust passage is formed integrally with a pipe, one end of which is opened on the outer surface of the peripheral wall, and the other end is opened on the inner surface of the peripheral wall.