JPH0219547Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Industrial application field) The present invention relates to an exhaust system for an outboard motor.

(Prior Art and its Problems) In general, outboard motors are configured to mix exhaust gas with, for example, cooling water and discharge the mixture into water in order to reduce noise during operation.

However, if the exhaust gas is released into the water, the following problems will occur during test operation before shipment.

That is, during test operation, the outboard motor is mounted in a small water tank 26 as shown in FIG. There is a risk that the surfaces of the cases 2 and 3 and the propeller 6 may be soiled, or that dirty water may be sucked in from the cooling water suction port 7 again, reducing the value of the product. Also, cleaning after the test is difficult.

(Means for solving the problem) In order to solve the above problem, the present invention forms an exhaust passage chamber for discharging exhaust gas in the transmission case, and provides a lower end outlet of the exhaust passage chamber in the water. An exhaust pipe that connects to the exhaust hole of the engine is inserted into the exhaust passage chamber from above, and a part of the case wall below the lower open end of the exhaust pipe has an inner diameter that is the same as or smaller than the inner diameter of the open end of the exhaust pipe. A hole with a larger inner diameter extending from the exhaust passage chamber to the outside is provided, and an exhaust pipe for test operation and a lid for normal operation, which can be freely connected to the opening end of the exhaust pipe, are selectively connected to the hole from the outside. It is fixed so that it can be replaced freely.

Furthermore, as shown in Figs. 5 and 6, the transmission case 2
Small bypass hole 2 on the rear wall for reducing exhaust gas pressure
A device in which only the hole 21' is formed and the hole 21' is communicated with the inside of the exhaust pipe 11 through the small bypass hole 31 of the exhaust pipe 11 has been used in the past.

(Embodiment) In FIG. 1, a transmission case (upper case) 2 extending into the water is provided below a diesel engine 1, and a lower case 3 is provided at the lower end of the transmission case 2. A propeller shaft support part 5 that projects downward is provided in the front half of the lower case 3, and a propeller 6 that projects backward is provided on the support part 5. A cooling water suction port 7 is formed on the side surface of the support portion 5, and a discharge port 8 facing rearward and downward is provided at the rear end portion of the lower case 3.

An exhaust passage chamber 10 for discharging exhaust gas and cooling water is formed within the transmission case 2, and a lower end portion of the exhaust passage chamber 10 communicates with the discharge port 8. The exhaust passage chamber 10 extends upward along the rear wall of the case 2,
It communicates with the cooling water passage of the engine 1, and an exhaust pipe 11 is inserted from above. The exhaust pipe 11 is connected to an exhaust hole of the engine 1 and extends downward to a midway portion of the exhaust passage chamber 10, with its lower open end 11a opening into the exhaust passage chamber 10. Exhaust passage chamber 10 from which the exhaust pipe 11 protrudes
In this section, an annular space on the outer peripheral surface of the exhaust pipe serves as a cooling water passage 12.

A hole 15 having an inner diameter larger than the inner diameter of the lower open end 11a of the exhaust pipe 11 is formed in the rear wall of the case 2, and the hole 15 is formed at a position slightly below the open end 11a of the exhaust pipe. There is. The hole 15 extends from the exhaust passage chamber 10 to the outside.

The hole 15 has an L for test operation as shown in Fig. 2.
A shaped exhaust pipe 18 and a lid 20 for normal operation as shown in FIG. 3 are selectively and replaceably fixed.

In FIG. 2, the L-shaped exhaust pipe 18 for test operation has approximately the same outer diameter as the exhaust pipe 11;
It can be freely inserted and removed from the outside of the case 2 into the hole 15. The front upper end of the pipe 18 can be freely fitted and connected to the open end 11a of the exhaust pipe 11, and the pipe 18 has a flange 19 in the middle thereof, and the flange 19 is attached to the rear wall of the case 2. It is detachably fixed to the rear surface with bolts 17. pipe 1
The bellows-shaped rear part 18a of 8 is extended to a suitable exhaust location above the water surface.

In FIG. 3, which shows the state during normal operation, the lid 20 for normal operation is arranged so as to close the hole 15, and is fixed to the rear surface of the rear wall of the case 2 with bolts 17. A small bypass hole 21 for reducing exhaust gas pressure is formed in the lid 20, and an upward guide rib 22 for reducing gas pressure is formed on the inner circumferential side of the lid 20 (the surface facing the exhaust passage chamber). A downward gas pressure reducing guide rib 23 is integrally formed on the side surface. The inner guide rib 22 projects forward to the rear end edge of the exhaust pipe 11.

(Function) During test operation before shipment, as shown in Figure 1,
Insert the exhaust pipe 18 through the hole 15 and close the exhaust pipe 11.
The flange portion 19 is fixed to the rear wall of the case 2. The outboard motor is mounted in the test water tank 26 in such a state.

During test operation, exhaust gas from the engine 1 is discharged from the exhaust pipe 11 to the outside of the water tank through the exhaust pipe 18, as shown by the hollow thick arrow in FIG. Therefore, the water in the water tank 26 shown in FIG. 1 is not contaminated with carbon or oil. Also, the cooling water sucked in from the suction port 7 is supplied to the cooling water jacket of the engine 1 through the cooling water passage in the case 2, and then flows to the outer periphery of the exhaust pipe 11 as shown by the solid arrow in FIG. It passes through the side annular cooling water passage 12 and the exhaust passage chamber 10, and is discharged into the water from the discharge port 8 at the lower end without mixing with the exhaust gas.

At the time of shipment, the lid 20 is fixed to the hole 15 as shown in FIG. 3, and the lid 20 is used for normal operation in the sea, lake, etc. with the lid 20 attached.

During normal operation at sea or the like, the exhaust gas coming out of the exhaust stack 11 shown in FIG. 3 mixes with cooling water in the exhaust passage chamber 10 and is discharged into the water from the discharge port (FIG. 1) 8 together with the cooling water.

To explain the role of the bypass hole 21 of the lid 20,
By removing a portion of the exhaust gas from the bypass hole 21, the pressure of the exhaust gas exiting from the exhaust port 8 during reverse or idling operation is lowered. This prevents the exhaust gas from being drawn into the forward propeller 6 and prevents cavitation from occurring. Of course, in this case, part of the exhaust gas and part of the cooling water are also discharged from the bypass hole. Moreover, by providing the upward guide ribs 22 on the inside of the lid 20, gas can be vented smoothly even when the gas pressure is relatively low. Further, by providing a downward guide rib 23 on the outside of the lid 20, the exhaust gas from the bypass hole 21 is smoothly guided downward, and there is no fear of contaminating things around the outboard motor.

Note that the exhaust gas pressure in the exhaust pipe 11 is high in the range of the opening section X of the exhaust valve as shown in FIG. becomes even more effective.

Furthermore, in the illustrated embodiment, by providing the bypass hole 21 below the open end 11a of the exhaust pipe 11, the small bypass hole 31 of the exhaust pipe 11 as shown in FIGS. 5 and 6 is eliminated. , during test operation as shown in Figure 1, when the exhaust pressure is low (when the exhaust valve is closed), cooling water flows into the exhaust stack 1.
There is no risk of intrusion into 1.

(Another embodiment) (1) The present invention can be applied to gasoline engines as well as diesel engines.

(2) It is appropriate that the hole 15 provided in the transmission case 2 has an inner diameter large enough to allow insertion of an exhaust pipe having an inner diameter that is at least the same as or larger than the inner diameter of the exhaust pipe 11.

(Effects of the Invention) As explained above, the present invention provides a wall portion of the transmission case 2 below the lower open end 11a of the exhaust pipe 11 with an inner diameter that is approximately the same as or smaller than the inner diameter of the open end 11a of the exhaust pipe 11. A hole 15 with a larger inner diameter extending from the exhaust passage chamber 10 to the outside is provided, and an exhaust pipe 18 for testing and a lid 20 for operation, which can be freely connected to the exhaust pipe opening end 11a, are connected to the hole 15 from the outside. Since it is fixed in a replaceable manner, it has the following advantages.

(1) During the pre-shipment test run in a small water tank, the exhaust pipe 18 is installed to prevent exhaust gas from being released into the water, so carbon and oil in the exhaust gas will not accumulate in the tank during the test run. There is no need to worry about carbon or oil getting on the outboard motor.

That is, the outboard motor hardly gets dirty during the test, and there is almost no effort required after the test.

(2) Since the lid 20 is attached during normal operation at sea or the like, exhaust gas can be discharged into the water together with cooling water, and therefore exhaust noise can be reduced.

As shown in FIG. 3, if the lid 20 itself is provided with a bypass hole 21 for reducing gas pressure, it is not necessary to provide a bypass hole separately from the lid 20, which is practical.

Furthermore, since the lid 20 is disposed below the lower end opening 11a of the exhaust pipe, if the lid 20 is provided with the bypass hole 21 as shown in FIG. There is no need to form a small hole 31 as in the conventional example shown in the figure. Furthermore, there is no fear that cooling water will enter the exhaust stack when the exhaust gas pressure is low during a test run with the pipe 18 installed.

[Brief explanation of the drawing]

Figure 1 is a partially longitudinal side view of an outboard motor to which the present invention is applied, with an exhaust pipe installed during a test run before shipment, and Figure 2 is a side view showing the outboard motor with an exhaust pipe installed during a test run before shipment.
Fig. 3 is an enlarged vertical cross-sectional view of the main part of the main part shown in Fig. 3, showing the state in which the lid for normal operation is attached;
Figure 4 is a graph showing changes in exhaust gas pressure;
FIG. 6 is a partial vertical cross-sectional view of a conventional example.
DESCRIPTION OF SYMBOLS 1... Engine, 2... Transmission case, 10... Exhaust passage chamber, 11... Exhaust pipe, 11a... Open end, 15... Hole, 18... Exhaust pipe for test operation, 20... Normal Lid for driving.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An exhaust passage chamber for discharging exhaust gas is formed in the transmission case, the lower end of the exhaust passage chamber is provided underwater, and the exhaust gas is connected to the exhaust hole of the engine. Inserting the cylinder into the exhaust passage chamber from above,
A hole having an inner diameter that is approximately the same as or larger than the inner diameter of the exhaust pipe opening end and extending from the exhaust passage chamber to the outside is provided in the case wall portion below the lower opening end of the exhaust pipe. An exhaust system for an outboard motor, characterized in that an exhaust pipe for test operation and a lid for normal operation, which can be freely connected to the opening end of the exhaust stack, are selectively and replaceably fixed from the outside. (2) The exhaust system for an outboard motor as set forth in claim 1 of the utility model registration claim, in which a small-diameter bypass hole is provided in the lid for normal operation.