JPH0939890A - Exhaust release structure of outboard motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable exhaust gas to be reliably discharged to the atmosphere by providing an exhaust gas expansion chamber on the way of an exhaust passage upstream from an exhaust hole formed on an engine holder, and integrally forming an exhaust gas release passage on the engine holder. SOLUTION: Exhaust gas discharged from an engine of an outboard motor is converged by an exhaust gas collecting cover, guided to an exhaust gas expansion chamber 34 in the lower part of the engine through an exhaust tube, depressurized, muffled, purified through a catalyst, guided to a second exhaust gas expansion chamber 35, and further depressurized, and muffled. Next, the exhaust gas is discharged into the water through the exhaust tube 41, an exhaust hole 40, and an exhaust passage 42. On the other hand, when exhaust pressure of the engine 6 is low and the exhaust gas can not be discharged into the water, the exhaust gas is discharged through an exhaust gas release passage 47 formed on the engine holder 4 and extending from the exhaust hole 40 to the outside of the engine cover 12, and therefore, discharge is made possible even if exhaust gas has small pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust release structure for outboard motors.

[0002]

2. Description of the Related Art In recent years, some outboard motors are provided with an exhaust gas purification catalyst for preventing air and water pollution in the middle of an exhaust passage.

As disclosed in, for example, Japanese Unexamined Patent Publication No. 6-146878, the catalyst is provided with an exhaust expansion chamber in the middle of the exhaust passage so as not to become a resistance to the flow of exhaust gas, and is arranged downstream of the exhaust expansion chamber. ing.

By the way, in the outboard motor, since the exhaust pressure of the engine is small at the time of starting the engine and idling, for example, seawater that has entered the exhaust passage cannot be discharged into the water, and exhaust gas is also discharged. It will be difficult.

Therefore, an exhaust release passage communicating with the atmosphere is provided in the middle of the exhaust passage so that part of the exhaust gas is released into the atmosphere. However, if the exhaust gas is emitted directly from the exhaust passage, the exhaust sound becomes louder. Therefore, the exhaust release passage has a complicated maze structure or, as shown in the above publication, the exhaust passage in the drive shaft housing located on the downstream side of the catalyst. An exhaust release passage is provided in. At the installation position of the exhaust release passage, the exhaust gas is considerably decompressed and silenced, so the exhaust release passage does not have a maze structure.

[0006]

However, if the exhaust release passage has a maze structure, the number of parts and the number of manufacturing steps increase, and the cost increases.

Further, as shown in the above publication, when an exhaust release passage is provided in the exhaust passage in the drive shaft housing, a water jacket for cooling the exhaust passage is provided between the drive shaft housing and the exhaust passage. Since the surroundings of the exhaust release passage must be sealed, the number of parts and the number of manufacturing processes increase, and the cost increases.

Further, a part of the drive shaft housing is always below the draft surface, and depending on the model of the hull to which the outboard motor is attached, the exhaust release passage may be below the draft surface, making it difficult to exhaust the exhaust gas and dust. It may get stuck.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust release structure for an outboard motor which has a simple structure and can reliably discharge exhaust gas into the atmosphere. .

[0010]

In order to solve the above-mentioned problems, an outboard motor exhaust release structure according to the present invention is an engine mounted on a hull via a bracket as described in claim 1. A holder, an engine arranged at an upper portion of the engine holder, and a drive shaft housing arranged at a lower portion of the engine holder,
In an outboard motor including an exhaust passage extending from the engine through the drive shaft housing into the water, an exhaust hole through which the exhaust passage passes is formed in the engine holder, and the exhaust passage is located upstream of the exhaust hole. While at least one exhaust expansion chamber is provided in the engine holder, an exhaust release passage for communicating the exhaust hole with the atmosphere is integrally formed in the engine holder.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an example of an outboard motor to which the present invention is applied, and FIG. 2 is a sectional view taken along line II-II in FIG.

As shown in FIG. 1, the outboard motor 1 includes a hull 2
It is attached to the transom 2a of FIG.
The outboard motor 1 includes an engine holder 4 connected to the bracket 3. An engine 6 is provided above the engine holder 4 via an oil seal housing 5, and an engine exhaust manifold 7 is provided below the engine holder 4. Drive shaft housings 8 are installed respectively.

As shown in FIGS. 1 and 2, the engine 6
Is, for example, a water-cooled 2-cycle V-type 6-cylinder engine.
The engine 6 is configured by combining a cylinder head 9, a cylinder block 10, a crankcase 11, and the like, and a V bank 20 is formed between the cylinder blocks 10 by arranging the pair of cylinder blocks 10 in a V shape. The engine 6 installed on the engine holder 4 is covered with an engine cover 12. Further, a crankshaft 13 is rotatably supported in the crankcase 11.

On the other hand, a gear case 14 is provided below the drive shaft housing 8, and a propeller shaft 15 driven by the engine 6 is rotatably supported by the gear case 14. The rotation of the engine 6 is transmitted to the propeller shaft 15 by a drive shaft 16 connected to the crankshaft 13 and a bevel gear (not shown) to drive a propeller 17 supported at the rear end of the propeller shaft 15. .

A cylinder 18 is formed in the cylinder block 10 of the engine 6. A piston 21 is slidably inserted into the cylinder 18, and the piston 21 and the crank pin 22 of the crank shaft 13 are connected by a connecting rod 23. The reciprocating stroke of the piston 21 is converted into the rotational movement of the crankshaft 13. A combustion chamber 24 is formed at the joint between the cylinder head 9 and the cylinder block 10, and an ignition plug 25 is screwed to the center of the combustion chamber 24 from the outside.

The crankcase 11 is provided with a reed valve device 26 as an intake valve device. A surge tank 27 is arranged on the upstream side of the reed valve device 26,
An intake pipe 29 having a throttle 28 is connected to the upstream side of the surge tank 27.

A fuel injector 30 is attached to the surge tank 27 from the outside, and the reed valve device 26 is provided.
Is arranged so as to inject fuel toward the upstream side of.

On the other hand, exhaust ports (not shown) are formed on the inner peripheral surface of each cylinder 18 outside the V bank 20.
These exhaust ports are covered by an exhaust gas collecting cover 31. The exhaust gas collecting cover 31 is provided for each cylinder 18
Although not shown in detail, it collects exhaust gas discharged from the first exhaust hole 32 formed in the oil seal housing 5, the engine holder 4, and the exhaust manifold 7, and the first exhaust hole 32. Is connected to the first exhaust tube 33 connected to.

A first exhaust expansion chamber 34 is provided below the exhaust manifold 7 in the drive shaft housing 8.
Is provided, and the first exhaust tube 33 is disposed inside thereof. A second exhaust expansion chamber 35 is provided in the upper part of the oil seal housing 5 and behind the cylinder head 9 of the engine 6 with respect to the traveling direction of the hull 2. The first exhaust expansion chamber 34 and the second exhaust expansion chamber 35 communicate with each other. 36
Is communicated with. The communication passage 36 is connected to the communication hole 37 formed in the oil seal housing 5, the engine holder 4, and the exhaust manifold 7, and is connected to the communication hole 37, and is disposed in the first exhaust expansion chamber 34. It is composed of an exhaust tube 38 and a third exhaust tube 39 connected to the communication hole 37 and arranged in the second exhaust expansion chamber 35.

On the other hand, a second exhaust hole 40 is formed in the oil seal housing 5, the engine holder 4 and the exhaust manifold 7 adjacent to the communication hole 37.
A fourth exhaust tube 41 is arranged above the second exhaust hole 40 and inside the second exhaust expansion chamber 35 to be connected to the second exhaust hole 40, and at the lower part of the second exhaust hole 40, the first exhaust gas is provided. The first exhaust passage 42 formed integrally with or separately from the expansion chamber 34 is connected. In addition, the first exhaust passage 42
The end portion on the outlet side of is connected to the second exhaust passage 43 provided in the gear case 14. Then, this second exhaust passage 43
Is communicated with water by an exhaust gas discharge passage 44 formed around the propeller shaft 15. As described above, the first exhaust hole 32, the first exhaust tube 33, the communication passage 36 (the communication hole 37, the second and third exhaust tubes 38,
39), the fourth exhaust tube 41, the second exhaust hole 4
0, the first exhaust passage 42, the second exhaust passage 43, and the exhaust gas exhaust passage 44 constitute an exhaust passage 45.

Further, the first exhaust expansion chamber 34 of the communication passage 36.
A catalyst 46 is attached to the side opening, that is, the lower portion of the second exhaust tube 38.

FIG. 3 is a plan view of the engine holder 4 taken along the line III-III in FIG. In addition, FIG. 4 shows a circle IV in FIG.
It is an enlarged view of the principal part shown by.

The engine holder 4 is integrally formed by, for example, a casting or die-casting method, and as shown in FIGS. 1, 3 and 4, the engine holder 4 has a second exhaust hole 40 through which a second exhaust hole 40 is formed. An exhaust release passage 47 is formed integrally with the engine holder 4 toward the rear.
The outlet side end of the exhaust release passage 47 is set so as to project to the outside of the engine cover 12, and the second exhaust hole 4
0 is in communication with the atmosphere. Incidentally, reference numeral 48 is a packing.

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

The exhaust gas discharged from each cylinder 18 of the engine 6 is converged by the exhaust gas collecting cover 31, and then introduced into the first exhaust expansion chamber 34 through the first exhaust hole 32 and the first exhaust tube 33. Decompressed and muted. The exhaust gas guided to the first exhaust expansion chamber 34 is purified by passing through the catalyst 46, is guided to the second exhaust expansion chamber 35 via the communication passage 36, and is further depressurized and silenced. Then, the exhaust gas guided to the second exhaust expansion chamber 35, the fourth exhaust tube 41, the second exhaust hole 40,
It is discharged into water through the first exhaust flow path 42, the second exhaust flow path 43, and the exhaust gas discharge passage 44.

By the way, when the engine 6 is stopped or idling, the exhaust pressure of the engine 6 is small and, for example, seawater 49 is filled up to the middle of the first exhaust passage 42 (see FIG. 1). Furthermore, since the exhaust pressure of the engine 6 is low, this seawater 49 cannot be discharged into the water, and exhaust of exhaust gas becomes difficult.

However, in the engine holder 4, the exhaust release passage 47 is formed from the second exhaust hole 40 to the engine cover 12.
By forming the exhaust gas toward the outside, exhaust gas having a low exhaust pressure can be released into the atmosphere (see arrow 50 in FIG. 4). Since the exhaust gas reaching the second exhaust hole 40 is sufficiently decompressed and silenced in the first and second exhaust expansion chambers 34 and 35, the exhaust release passage 47 needs to have a complicated maze structure for silencing. There is also no exhaust release passage 47
Since it is integrally formed with the engine holder 4, the number of parts and the number of manufacturing steps do not increase significantly, and the cost does not increase.

Further, since the engine holder 4 is always arranged at a position sufficiently higher than the draft surface, the exhaust release passage 47 will not be below the draft surface depending on the model of the hull 2 to which the outboard motor 1 is attached. Can be difficult
There is no problem such as clogging with dust.

Furthermore, since no water jacket for cooling the exhaust passage 45 is formed around the exhaust release passage 47, no sealing process is required.

[0031]

As described above, according to the exhaust release structure of the outboard motor of the present invention, the engine holder mounted on the hull via the bracket and the engine arranged on the upper part of the engine holder. An outboard motor having a drive shaft housing disposed below the engine holder and extending into the water from the engine through the drive shaft housing, wherein the exhaust passage passes through the engine holder. An exhaust hole is formed, and at least one exhaust expansion chamber is provided in the exhaust passage upstream of the exhaust hole, while an exhaust release passage that connects the exhaust hole and the atmosphere is integrally formed in the engine holder. Therefore, the exhaust gas can be reliably discharged into the atmosphere with a simple structure.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an outboard motor showing an embodiment of an exhaust release structure for an outboard motor according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

3 is a plan view of the engine holder taken along the line III-III in FIG.

FIG. 4 is an enlarged view of a main part indicated by a circle IV in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outboard motor 2 Hull 3 Bracket 4 Engine holder 6 Engine 8 Drive shaft housing 34 First exhaust expansion chamber 35 Second exhaust expansion chamber 40 Second exhaust hole 45 Exhaust passage 46 Catalyst 47 Exhaust release passage

Claims (1)

[Claims] 1. An engine holder mounted on a hull via a bracket, an engine arranged above the engine holder, and a drive shaft housing arranged below the engine holder. In an outboard motor having an exhaust passage extending into the water through the drive shaft housing, an exhaust hole 40 through which the exhaust passage 45 passes is formed in the engine holder 4, and the exhaust passage 45 upstream of the exhaust hole 40. While at least one exhaust expansion chamber 34, 35 is provided in the middle of the engine, an exhaust release passage 47 for communicating the exhaust hole 40 with the atmosphere is integrally formed in the engine holder 4. Exhaust release structure.