1. Field of the Invention
The present invention relates to an exhaust system of an outboard motor and particularly to an exhaust system of an outboard motor in which a catalyst is properly disposed in an exhaust passage.
2. Related Art
An outboard motor discharges exhaust gas from an engine into water. To purify the exhaust gas, an outboard motor is provided with a catalyst in an exhaust passage of the engine. In such arrangement, if the catalyst comes in contact with seawater, for example, and flows back into the exhaust passage, performance of the catalyst is degraded. Therefore, it is preferable to dispose the catalyst in the exhaust passage in an engine cover located away from a water surface (sea surface).
Such arrangement of an outboard motor is, for example, disclosed in Japanese Patent Application Laid-open No. 2000-356123 (Patent Publication 1). In the outboard motor described in the Patent Publication 1, two catalysts are arranged side by side in the exhaust passage, and exhaust gas discharged from the engine is led to the exhaust passage above the engine and then flows through the two catalysts in the same direction to be purified.
In the outboard motor described above, however, the two catalysts are arranged side by side and the exhaust gas flows through the catalysts in the same direction, and therefore, according to increasing in capacity of the catalysts, a flow passage area of the exhaust passage increases and the exhaust gas flow is likely to stagnate. Moreover, the exhaust gas is led to the exhaust passage above the engine before it is led to the two catalysts, the exhaust passage in the engine cover increases in size.
As described above, the outboard motor of the Patent Publication 1 provides problems of increase in size of the exhaust passage and degradation of exhaust purifying performance.
Moreover, in the outboard motor described above, because the catalysts are arranged in side by side and the exhaust gas flows through the catalysts in the same direction, it is necessary for the exhaust gas to be distributed into two passages and led to the respective catalysts. In this case, if the exhaust gas is distributed unevenly, different amounts of the exhaust gas pass through the respective catalysts. Therefore, the catalyst through which excessive exhaust flows cannot sufficiently purify the exhaust gas and, hence, the purifying efficiency of the catalysts may be decreased.
Furthermore, in the outboard motor described of the Patent Publication 1, it is necessary to adjust gaps between the exhaust passage and the catalysts to make sure that the exhaust gas passes through the catalysts. In addition, in the outboard motor, the catalysts are supported by bolts, and when the bolts corrode, it may become difficult to attach or detach the catalysts.
The present invention was conceived in consideration of the circumstances mentioned above, and an object of the invention is to provide an exhaust system of an outboard motor in which an exhaust passage in an engine cover is miniaturized, exhaust purifying performance of a catalyst is enhanced, and maintenance performance is improved due to easy attachment and detachment of a catalyst.
The above and other objects can be achieved according to the present invention by providing an exhaust system of an outboard motor including an engine mounted vertically and covered with an engine cover and an exhaust unit provided on a side portion of the engine, the exhaust unit including an exhaust passage communicating with exhaust ports in a cylinder head of the engine, the exhaust system comprising:
an exhaust passage forward portion including an exhaust passage communicating with the exhaust passage of the exhaust unit;
an exhaust passage reversed portion including an exhaust passage formed below the exhaust passage of the exhaust passage forward portion in parallel therewith and communicating with an exhaust passage disposed below the engine; and
an exhaust passage U-turn portion including an exhaust passage communicating with both the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion to reverse a flowing direction of exhaust,
wherein a catalyst for purifying the exhaust is disposed at a junction between both the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion and the exhaust passage of the exhaust passage U-turn portion.
In a preferred embodiment, it may be desired that the engine is a multicylinder engine, the exhaust unit forms an exhaust collecting portion including the exhaust passage for collecting the exhaust from the exhaust ports in the cylinder head of the multicylinder engine, and the exhaust passage of the exhaust passage forward portion is formed to extend from a central portion of the exhaust passage of the exhaust collecting portion to be substantially perpendicular to the exhaust passage.
It may be desired that the exhaust passage of the exhaust passage forward portion is formed to extend from the central portion of the exhaust passage of the exhaust collecting portion toward a crankcase of the engine.
The catalyst may be disposed in the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion or in the exhaust passage of the exhaust passage U-turn portion and pinched by the exhaust passage forward portion, the exhaust passage reversed portion, and the exhaust passage U-turn portion.
The catalyst may be press-fitted in and integrated with the exhaust passage of the exhaust passage U-turn portion.
It may be further desired that the catalyst includes a single catalyst member including a sectional area substantially equal to a sum of sectional areas of both the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion.
The catalyst may include two catalyst members including sectional areas substantially equal to sectional areas of the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion.
According to the present invention of the characters mentioned above, a sufficient catalyst area is obtainable without increasing the size of the exhaust passage. Since the exhaust gas reliably passes through the catalyst, the exhaust purifying performance of the catalyst can be improved while making the exhaust passage compact.
Moreover, the catalyst is disposed at the junction between both the exhaust passages of the exhaust passage forward portion and the exhaust passage reversed portion and the exhaust passage of the exhaust passage U-turn portion, which facilitates attachment and detachment of the catalyst and improves ease of maintenance.
The nature and further characteristic features of the present invention will be made clearer from the following descriptions made with reference to the accompanying drawings.
In accompanying drawings:
Preferred embodiments of the present invention will be described below based on the drawings. Further, it is to be noted that terms “right”, “left”, “upper”, “lower” and the like used herein in illustrated states or in an actually operating state.
With reference to
An upper end portion of a pilot shaft 18 is fixed to the engine holder 12 and, on the other hand, an opposite lower end portion thereof is fixed to the drive shaft housing 14. The pilot shaft 18 is laterally (horizontally) rotatably supported on a swivel bracket 19. The swivel bracket 19 is swingably (vertically) rotatably supported on a cramp bracket 21 by means of a swivel shaft 20, and the cramp bracket 21 is fixed to a stern portion 22 of a hull. In this way, the outboard motor 10 is mounted to the stern portion 22 so as to be turnable in the horizontal and vertical directions.
The engine 11 is a four-cycle multicylinder engine, for example, a four-cycle in-line four-cylinder engine, and disposed vertically, in which a crankshaft, not shown, is oriented in the vertical direction and cylinders 23A, 23B, 23C and 23D (
Rotation of the crankshaft of the engine 11 is transmitted to a drive shaft 28 via a drive gear and a driven gear, not shown. The drive shaft 28 vertically extends through the engine holder 12, the oil pan block 13, the drive shaft housing 14 and the gear case 15, and is engaged with a bevel gear mechanism 29 in the gear case 15. Therefore, rotating force of the crankshaft is transmitted to a propeller shaft 30 which is coupled to the bevel gear mechanism 29 via the drive shaft 28 and the bevel gear mechanism 29, and when the propeller shaft 30 rotates, a propeller 31 is also rotated. Rotation of the drive shaft 28 constantly rotating in one direction is switched between normal and reverse directions by a forward/reverse switching mechanism. Thus, the propeller 31 rotates normally or reversely to move the hull in the forward or rearward direction.
As shown in
The cylinder head 26 is mounted with fuel injectors for injecting fuel into the intake ports 35A to 35D and provided with intake valves and exhaust valves, not shown, for opening and closing the intake ports 35A to 35D and the exhaust ports 36A to 36D, respectively. In the cylinder head 26, valve trains 37A, 37B, 37C and 37D for operating the intake valves and the exhaust valves are also disposed. The valve trains 37A to 37D are covered with the head cover 27.
The crankshaft is disposed in a crank chamber formed to the crankcase 24 and the cylinder block 25 and is coupled to respective pistons in the cylinders 23A, 23B, 23C and 23D through connection rods, not shown, interposed therebetween. The pistons reciprocate due to combustion of the fuel in the respective combustion chambers 34A to 34D and the reciprocating motion of the piston is converted into rotational motion by the crankshaft and then transmitted to the drive shaft 28 (
As shown in
The intake system 38 includes an intake air induction passage 41 (
In the exhaust system 39, an exhaust manifold 47 as an exhaust collecting portion is extended vertically on a side portion of the cylinder block 25 in the engine 11. In the exhaust manifold 47, an exhaust passage 48 extends in the same direction so as to communicate with the exhaust ports 36A, 36B, 36C and 36D. The exhaust passage 48 in the exhaust manifold 47 communicates with an exhaust passage 49 formed in the engine holder 12 via an exhaust passage forward (outward) portion 60, an exhaust passage U-turn portion 62, and an exhaust passage reversed (homeward) portion 61 so as to collect an exhaust gas from the exhaust ports 36A to 36D of the engine 11. The exhaust gas is led to the exhaust passage 49.
The exhaust gas is led from the exhaust passage 49 in the engine holder 12, via an exhaust passage in the oil pan block 13 shown in
The engine 11 is a water-cooled engine and uses seawater, for example, as cooling water. In other words, as shown in
The cooling water led to the cooling water passage in the engine holder 12 is guided to a water jacket 55 formed around the exhaust passage 48 in the exhaust manifold 47 in the cylinder block 25 and a water jacket formed around the exhaust ports 36A to 36D in the cylinder head 26 to cool the exhaust passage 48 and the exhaust ports 36A to 36D.
Furthermore, the cooling water led to the cooling water passage in the engine holder 12 is guided to water jackets 63, 64, and 65 formed around the exhaust passage forward portion 60, the exhaust passage reversed portion 61, and the exhaust passage U-turn portion 62 so as to cool the exhaust passage forward portion 60, the exhaust passage reversed portion 61, and the exhaust passage U-turn portion 62 as shown also in
The cooling water, that has cooled the cylinders 23A to 23D, the combustion chambers 34A to 34D, the exhaust passage 48 in the exhaust manifold 47, the exhaust ports 36A to 36D, the exhaust passage forward portion 60, the exhaust passage reversed portion 61, and the exhaust passage U-turn portion 62, passes through the other cooling water passage in the engine holder 12, flows down into the exhaust expansion chamber in the drive shaft housing 14 shown in
A thermostat or the like, not shown, may be disposed in the above-described cooling water passage to control a flow of the cooling water based on a detected water temperature.
A magnet cover 66 covers a flywheel magnet coupled to the crankshaft, as shown in
As shown in
As shown in
Although the first exhaust passage 60A, the second exhaust passage 60B, the first exhaust passage 61A, and the second exhaust passage 61B may be formed on a side surface portion of the cylinder block 25, the first exhaust passage 60A of the exhaust passage forward portion 60 is formed in the cylinder block 25 and the second exhaust passage 60B of the exhaust passage forward portion 60, and the first exhaust passage 61A and the second exhaust passage 61B of the exhaust passage reversed portion 61 are formed in a side surface member 67 secured to the side portion of the cylinder block 25 in the embodiment. Therefore, the second exhaust passage 60B of the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 are integrally formed in the side surface member 67.
As shown in
As shown in
Then, at a junction between the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61, and the exhaust passage 62A of the exhaust passage U-turn portion 62, a catalyst 71 for purifying the exhaust gas is disposed. In the embodiment, the catalyst 71 is fitted in a junction position in the exhaust passage 62A of the exhaust passage U-turn portion 62 to be joined to the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61 as shown in
At this time, as shown in
A front surface of the catalyst 71 is supported by a spring 74 such as a tapered washer disposed at the step portion 73. A rear surface of the catalyst 71 is supported by the junction end 60BB of the second exhaust passage 60B of the exhaust passage forward portion 60 and the junction end 61AA of the first exhaust passage 61A of the exhaust passage reversed portion 61 (i.e., the junction end surface 68 of the side surface member 67). In this way, the catalyst 71 is pinched between the exhaust passage U-turn portion 62, and the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 by the elastic force of the spring 74.
This catalyst 71 contains platinum, rhodium, palladium or the like, serves to promote oxidation-reduction function of harmful substances such as carbon monoxide (CO), hydrocarbons (CH), nitrogen oxides (NOx) in the exhaust gas flowing through the exhaust passage 48, and changes them into harmless carbon dioxide (CO2), water (H2O), nitrogen (N2), and the like.
As shown in
According to the present embodiment of the structure mentioned above, the following functions and effects (1) to (5) will be attained.
(1) As shown in
The catalyst 71 is disposed in the junction position in the exhaust passage 62A of the exhaust passage U-turn portion 62 to be joined to the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61. Therefore, the exhaust gas from the exhaust passage 48 in the exhaust manifold 47 passes through the catalyst 71 twice and is purified while passing through the second exhaust passage 60B of the exhaust passage forward portion 60, turns in U-shape in the exhaust passage 62A of the exhaust passage U-turn portion 62, and reaches the first exhaust passage 61A of the exhaust passage reversed portion 61.
As a result, in a narrow engine room 75 (
(2) The catalyst 71 is disposed in the junction position in the exhaust passage 62A of the exhaust passage U-turn portion 62 to be joined to the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61. Therefore, the catalyst 71 can be easily detached from and attached to the exhaust passage U-turn portion 62 by detaching the exhaust passage U-turn portion 62 from the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 (i.e., the side surface member 67). Detachment and attachment of the catalyst 71 becomes easy in this way, thereby improving the maintenance of the catalyst 71.
(3) One catalyst 71 is disposed in the exhaust passage 62A of the exhaust passage U-turn portion 62, the exhaust gas flowing from the second exhaust passage 60B of the exhaust passage forward portion 60 toward the exhaust passage 62A of the exhaust passage U-turn portion 62 passes through the upper half portion of the catalyst 71 so as to be purified, and the exhaust gas flowing from the exhaust passage 62A of the exhaust passage U-turn portion 62 toward the first exhaust passage 61A of the exhaust passage reversed portion 61 passes through the lower half portion of the catalyst 71 so as to be purified. Therefore, the exhaust purifying efficiency can be improved. At the same time, the number of catalysts 71 can be reduced. Thus, the maintenance cost can be reduced and the easiness of assembling the catalyst 71 can be improved.
(4) The catalyst 71 has the sectional area substantially equal to the sum of the respective flow path areas of the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61, and this catalyst 71 is disposed in the exhaust passage 62A of the exhaust passage U-turn portion 62. Therefore, an outer peripheral portion of the catalyst 71 is in contact with the exhaust passage U-turn portion 62 and is cooled by the cooling water flowing through the water jacket 65 of the exhaust passage U-turn portion 62. However, an inner portion except the outer peripheral portion of the catalyst 71 is not cooled too much by the cooling water, and thus, the performance of the catalyst 71 can be prevented from degrading.
(5) The catalyst 71 is pinched between the exhaust passage U-turn portion 62, and the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 by the action of the elasticity of the spring 74 (
The catalyst 71 may be press-fitted in the exhaust passage 62A of the exhaust passage U-turn portion 62 and formed integrally with the exhaust passage U-turn portion 62 instead of being pinched by the exhaust passage U-turn portion 62, the exhaust passage forward portion 60, and the exhaust passage reversed portion 61. In this case, both the catalyst 71 and the exhaust passage U-turn portion 62 are replaced at the time of replacement of the catalyst 71. Therefore, mis-assembling of the catalyst 71 can be prevented.
In the second embodiment, the same reference numerals are added to portions or members similar or corresponding to those in the first embodiment and duplicated description is omitted or simplified herein.
An exhaust system 80 of the outboard motor in this embodiment is different from the exhaust system 39 in the first embodiment in that the catalyst 71 is not disposed in the exhaust passage U-turn portion 62 but in a side surface member 81 formed by integrating the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 with each other.
In other words, the catalyst 71 is fitted in an area of the side surface member 81 that is inside a junction end surface portion 82 to be abutted and joined to the opening end surface 69 of the exhaust passage U-turn portion 62 and forms a portion of the second exhaust passage 60B of the exhaust passage forward portion 60 and the first exhaust passage 61A of the exhaust passage reversed portion 61.
The catalyst 71 is pinched by the exhaust passage U-turn portion 62 and the side surface member 81 (i.e., the exhaust passage forward portion 60 and the exhaust passage reversed portion 61) by the elastic force of the spring 74 (not shown in
According to the embodiment, the catalyst 71 is disposed at the junction between the exhaust passage forward portion 60 having the second exhaust passage 60B and the exhaust passage reversed portion 61 having the first exhaust passage 61A, and the exhaust passage U-turn portion 62 having the exhaust passage 62A. The exhaust gas flowing from the second exhaust passage 60B of the exhaust passage forward portion 60 toward the exhaust passage 62A of the exhaust passage U-turn portion 62 flows through the upper half portion of the catalyst 71 so as to be purified. The exhaust gas flows in the direction reversed in the exhaust passage 62A of the exhaust passage U-turn portion 62 toward the first exhaust passage 61A of the exhaust passage reversed portion 61 flows through the lower half portion of the catalyst 71 so as to be purified. As a result, this embodiment also exerts effects the same as or similar to those (1) to (5) of the first embodiment.
In the third embodiment, like reference numerals are added to portions or members similar or corresponding to those in the first embodiment, and duplicated description will be omitted herein.
An exhaust system 90 of the outboard motor in this third embodiment is different from the exhaust system 39 in the first embodiment in that two catalysts (catalysts 91, 92) are disposed in a side surface member 93 formed by integrating the exhaust passage forward portion 60 and the exhaust passage reversed portion 61 with each other, or in the exhaust passage U-turn portion 62 (in the side surface member 93 in this embodiment).
A catalyst 91 is fitted in an area of the side surface member 93 that is inside a junction end surface 94 to be abutted and joined to the opening end surface 69 of the exhaust passage U-turn portion 62 and forms a portion of the second exhaust passage 60B of the exhaust passage forward portion 60.
Furthermore, a catalyst 92 is fitted in an area of the side surface member 93 that is inside the junction end surface 94 and forms a portion of the first exhaust passage 61A of the exhaust passage reversed portion 61. The catalyst 91 has a circular section with an area substantially equal to a sectional area of the second exhaust passage 60B of the exhaust passage forward portion 60. The catalyst 92 has a circular section with an area substantially equal to a sectional area of the first exhaust passage 61A of the exhaust passage reversed portion 61.
The respective catalysts 91 and 92 are pinched by the exhaust passage U-turn portion 62 and the side surface member 93 (i.e., the exhaust passage forward portion 60 and the exhaust passage reversed portion 61) by the elastic force of the spring 74 (not shown in
Therefore, in this embodiment, the exhaust gas flowing from the second exhaust passage 60B of the exhaust passage forward portion 60 toward the exhaust passage 62A of the exhaust passage U-turn portion 62 flows through the catalyst 91 so as to be purified. The exhaust gas flows in the direction reversed in the exhaust passage U-turn portion 62 toward the first exhaust passage 61A of the exhaust passage reversed portion 61 through the catalyst 92 so as to be purified.
As a result, this third embodiment exerts effects similar to the effects (1) to (3) and (5) of the first embodiment together with the following effect (6).
(6) The exhaust gas, which flows through the second exhaust passage 60B of the exhaust passage forward portion 60, the exhaust passage 62A of the exhaust passage U-turn portion 62, and the first exhaust passage 61A of the exhaust passage reversed portion 61 in this order, flows through the two catalysts 91 and 92. Therefore, the catalysts 91 and 92 may be of different kinds. In this case, the different kinds of catalysts 91 and 92 will equally remove harmful substances in the exhaust gas to thereby purify the exhaust.
Further, it is to be noted that although the invention has been described above with reference to the embodiments, the invention is not limited to such embodiments, and many other changes and modifications may be made without departing from the scopes of the appended claims.
For example, the second exhaust passage 60B in the exhaust passage forward portion 60 may be formed to extend not toward the crankcase 24 but toward the cylinder head 26, and the exhaust passage U-turn portion 62 may be disposed on the side of the cylinder head 26.
Number | Date | Country | Kind |
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2007-267675 | Oct 2007 | JP | national |