Exhaust system for marine propulsion engines

Abstract

To improve holding stability when holding a metal catalyst in an exhaust passage.SOLUTION: An outboard engine exhaust system comprises: an exhaust passage 32 allowing exhaust gas from an engine to be distributed therethrough; and a catalyst device 51 which is installed in the exhaust passage 32 and purifies the exhaust gas. The exhaust passage 32 has: an exhaust manifold 33; and a collector 37 which is connected to an outflow pipe section 36 of the exhaust manifold 33. The catalyst device 51 has: a metal catalyst 52; an outer shell section 53; and a bracket 54. The bracket 54 has a protrusion section 56 in a flange shape outwardly protruding in a radial direction. The catalyst device 51 is held in the exhaust passage 32 with the protrusion section 56 sandwiched between the outflow pipe section 36 and the collector 37.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an exhaust system for a marine propulsion device. [Background technology]

[0002] A catalytic converter that purifies exhaust gas from an engine (internal combustion engine) is provided in the exhaust passage of a marine propulsion device that uses an engine (internal combustion engine) as its power source. The catalytic converter has a catalyst that reduces harmful components contained in the exhaust gas from the engine. The catalyst is formed by supporting precious metals such as platinum and palladium on a honeycomb-shaped carrier.

[0003] The catalyst devices installed in marine propulsion engines often use metal catalysts with a metal carrier or ceramic catalysts with a ceramic carrier. Metal catalysts are more expensive than ceramic catalysts, but have higher impact resistance.

[0004] The following Patent Document 1 describes an exhaust system for an outboard motor that employs a metal catalyst. As shown in Figs. 1 to 3 of the document, the exhaust system described in Patent Document 1 includes an exhaust manifold (35A) that collects exhaust gas. The exhaust manifold (35A) is connected to the outlets (36) of the exhaust ports of the engine (5). A catalyst (42) using a metal honeycomb as a carrier is provided in a second exhaust passage (40A) that constitutes a part of the exhaust manifold (35A). The catalyst (42) is press-fitted into the second exhaust passage (40A) with a mat-shaped insulating material (45) wrapped around it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-169707 A Summary of the Invention [Problem to be solved by the invention]

[0006] During engine operation, the catalyst installed in the exhaust passage is subjected to engine vibration. In addition, when the ship rides over waves and lands on water while sailing, or when the ship makes small jumps while planing, the catalyst is subjected to impacts caused by collisions between the ship and the water surface. To prevent the catalyst from shifting position or falling out of the exhaust passage due to such vibrations and impacts, the catalyst needs to be held stably in the exhaust passage.

[0007] In this regard, in the exhaust system described in the above Patent Document 1, the metal catalyst is held in the second exhaust passage by being pressed into the second exhaust passage with a heat insulating material wrapped around it.

[0008] When comparing a case where a metal catalyst wrapped in a heat insulating material is pressed into the exhaust passage with a case where a ceramic catalyst wrapped in a heat insulating material is pressed into the exhaust passage, the friction coefficient of the metal catalyst in contact with the heat insulating material is smaller than that of the ceramic catalyst in contact with the heat insulating material, so that when a metal catalyst wrapped in a heat insulating material is pressed into the exhaust passage, the retention force for holding the catalyst in the exhaust passage tends to be smaller than when a ceramic catalyst wrapped in a heat insulating material is pressed into the exhaust passage. Therefore, when the metal catalyst is simply held by pressing it into the second exhaust passage as in the exhaust device described in Patent Document 1, it is difficult to ensure a retention force that can withstand the above-mentioned vibrations and impacts, and there is a risk that the catalyst will shift position or fall off due to the above-mentioned vibrations and impacts.

[0009] Furthermore, even if, at the beginning of manufacture of the marine propulsion unit, it is possible to ensure a holding force capable of resisting the above-mentioned vibrations and shocks by pressing the metal catalyst into the exhaust passage to hold it there, there is a risk that the holding force capable of resisting the above-mentioned vibrations and shocks cannot be maintained for a long period of time due to deterioration over time of the insulation material wrapped around the metal catalyst.

[0010] The present invention has been made in consideration of the problems such as those described above, and an object of the present invention is to provide an exhaust device for a marine propulsion unit that can improve the stability of holding a metal catalyst in an exhaust passage. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention The first exhaust device An exhaust device for discharging exhaust gas from an engine of a marine propulsion device, comprising: an exhaust passage for circulating the exhaust gas; 、 and a catalytic device for purifying the exhaust gas, the exhaust passage comprising a first exhaust pipe and a second exhaust pipe connected to the outlet side of the first exhaust pipe, the catalytic device comprising a metal catalyst having a metallic catalyst carrier, a cylindrical outer shell portion containing the metal catalyst therein, and a retaining portion provided on the outer shell portion and formed into a brim-like shape protruding radially outward from the outer circumferential surface of the outer shell portion, for retaining the catalytic device in the exhaust passage, the catalytic device being retained in the exhaust passage by the retaining portion being sandwiched between the outlet side end of the first exhaust pipe and the inlet side end of the second exhaust pipe. The first exhaust pipe and the holding part are formed from different metals, and a first insulating member is provided between the first exhaust pipe and the holding part, and the first exhaust pipe and the holding part are insulated from each other by the first insulating member. It is characterized by: A second exhaust system of the present invention is an exhaust system that discharges exhaust gas from an engine of a marine propulsion device, and includes an exhaust passage through which the exhaust gas flows, and a catalytic device provided within the exhaust passage and that purifies the exhaust gas, the exhaust passage including a first exhaust pipe and a second exhaust pipe connected to an outlet side of the first exhaust pipe, and the catalytic device includes a metal catalyst having a metallic catalyst carrier, an outer shell portion formed in a cylindrical shape and containing the metal catalyst therein, and a catalytic converter provided in the outer shell portion and extending radially outward from an outer circumferential surface of the outer shell portion. and a retaining portion for retaining the catalytic converter in the exhaust passage, the catalytic converter being retained in the exhaust passage by sandwiching the retaining portion between an outlet end of the first exhaust pipe and an inlet end of the second exhaust pipe, the second exhaust pipe and the retaining portion being formed from different metals, a second insulating member being provided between the second exhaust pipe and the retaining portion, and the second exhaust pipe and the retaining portion being insulated from each other by the second insulating member. Effect of the Invention

[0012] According to the present invention, when a metal catalyst is held in an exhaust passage, the stability of the holding can be improved. [Brief description of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram showing an outboard motor including an exhaust device according to an embodiment of the present invention; [Diagram 2] 1 is a perspective view showing an engine provided with an engine holder and an exhaust device according to an embodiment of the present invention; [Diagram 3]1 is a cross-sectional view showing an exhaust device according to an embodiment of the present invention with a portion removed to expose the inside. [Figure 4] 4 is a cross-sectional view showing a lower end of an outflow pipe portion of an exhaust manifold, an upper end of a collector, and a catalytic device in the exhaust system in FIG. 3. [Diagram 5] 5 is a cross-sectional view showing a portion where a protruding portion of a bracket is clamped between a lower end portion of an outflow pipe portion and an upper end portion of a collector in a catalytic device provided in the exhaust system in FIG. 4. FIG. [Figure 6] FIG. 4 is a cross-sectional view showing a modified example of the catalytic converter according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An exhaust system according to an embodiment of the present invention is an exhaust system that discharges exhaust gas from an engine of a marine propulsion device, and includes an exhaust passage through which the exhaust gas flows, and a catalytic device that purifies the exhaust gas.

[0015] In the exhaust system, the exhaust passage includes a first exhaust pipe and a second exhaust pipe connected to the outlet side of the first exhaust pipe.

[0016] In the exhaust system, a catalytic converter is provided in the exhaust passage. The catalytic converter includes a metal catalyst having a metallic catalyst carrier, a cylindrical outer shell that houses the metal catalyst, and a holder for holding the catalytic converter in the exhaust passage.

[0017] The retaining portion is provided on the outer shell portion (e.g., joined or integrally formed) and formed into a flange shape that protrudes radially outward beyond the outer circumferential surface of the outer shell portion. The catalytic converter is retained in the exhaust passage by sandwiching the retaining portion between the outlet end of the first exhaust pipe and the inlet end of the second exhaust pipe.

[0018] In the exhaust system of this embodiment, the catalytic converter is held in the exhaust passage by clamping the retaining portion between the outlet end of the first exhaust pipe and the inlet end of the second exhaust pipe. Therefore, compared to a case in which the catalytic converter is held in the exhaust passage simply by pressing it into the exhaust passage with insulation wrapped around it, the retaining force that holds the catalytic converter in the exhaust passage can be increased and the stability of the catalytic converter being held in the exhaust passage can be improved. EXAMPLES

[0019] Hereinafter, an embodiment of the exhaust system of the present invention will be described. In the description of the embodiment, the directions of up (Ud), down (Dd), front (Fd), rear (Bd), left (Ld), and right (Rd) will be described according to the arrows drawn at the bottom right of each figure.

[0020] (Outboard motor) Fig. 1 shows an outboard motor 1 including an exhaust system according to an embodiment of the present invention. The outboard motor 1 is a device that generates propulsive power for a boat, and is one form of a boat propulsion device. As shown in Fig. 1, the outboard motor 1 is attached to a transom 82 provided at the stern of a boat 81.

[0021] An engine holder 10 and an engine 21 serving as a power source for the outboard motor 1 are provided at the top of the outboard motor 1. The engine 21 is mounted on the engine holder 10. The lower parts of the engine holder 10 and the engine 21 are covered by a bottom cowling 2, and the upper part of the engine 21 is covered by a top cowling 3. An upper casing 4 provided below the bottom cowling 2 contains a drive shaft 5 that transmits the power of the engine 21 to a propeller shaft 8. A lower casing 6 provided below the upper casing 4 contains a gear mechanism 7 that transmits the rotation of the drive shaft 5 to the propeller shaft 8, and the propeller shaft 8 that is the rotating shaft of the propeller 9. The propeller 9 is attached to the rear end of the propeller shaft 8.

[0022] (engine) FIG. 2 shows an engine 21 provided with the engine holder 10 and the exhaust device 31 according to the embodiment of the present invention. The engine 21 is a four-stroke engine that uses gasoline as fuel. As shown in FIG. 2, the engine 21 has a crankcase 22 at its front and, for example, four cylinders 23 at the rear of the crankcase 22. Each of the four cylinders 23 extends in the front-rear direction and is lined up in the vertical direction. A cylinder head 24 is provided at the rear of these cylinders 23. As shown in FIG. 1, a crankshaft 25 extending in the vertical direction is provided in the crankcase 22. Each cylinder 23 has a piston 26 provided therein, and each piston 26 is connected to the crankshaft 25 via a connecting rod 27. The crankshaft 25 is connected to the drive shaft 5.

[0023] Although not shown, the cylinder head 24 is provided with an intake port that sends a mixture of air and gasoline into the cylinder 23, an exhaust port that discharges the combustion gas in the cylinder 23 to the outside of the cylinder 23 as exhaust gas, an intake valve that opens and closes the intake port, an exhaust valve that opens and closes the exhaust port, and a spark plug that ignites the mixture, for each cylinder 23. Furthermore, the cylinder head 24 is provided with a valve mechanism that controls the opening and closing of each intake valve and each exhaust valve.

[0024] (Exhaust system) FIG. 3 shows the exhaust device 31. In FIG. 3, the left portion of the exhaust device 31 has been removed to expose the inside of the exhaust device 31. The exhaust device 31 is a device that discharges exhaust gas from the engine 21, and as shown in FIG. 3, includes an exhaust passage 32 through which the exhaust gas flows, and a catalytic device 51 that purifies the exhaust gas. The exhaust device 31 in this embodiment is disposed on the left side of the engine 21. Also, arrow A in FIG. 3 indicates the direction in which the exhaust gas flows.

[0025] (Exhaust passage) The exhaust passage 32 includes an exhaust manifold 33 as a first exhaust pipe and a collector 37 as a second exhaust pipe. Both the exhaust manifold 33 and the collector 37 are made of an aluminum alloy. Both the exhaust manifold 33 and the collector 37 have a double-cylinder structure.

[0026] The exhaust manifold 33 includes four inlet pipe sections 34 (the same number as the number of cylinders), a junction section 35, and a single outlet pipe section 36. Each inlet pipe section 34 is formed on the inlet side of the exhaust manifold 33 through which exhaust gas flows in. The outlet pipe section 36 is formed on the outlet side of the exhaust manifold 33 through which exhaust gas flows out. The junction section 35 is formed in the exhaust manifold 33 between the four inlet pipe sections 34 and the outlet pipe section 36.

[0027] The four inlet pipes 34 are aligned in the vertical direction, and the inlets of these inlet pipes 34 are connected to the outlets of the four exhaust ports, respectively. In addition, the outlet sides of these inlet pipes 34 are each connected to a junction 35.

[0028] 3, the outflow pipe section 36 is formed in a cylindrical shape, extends forward from the upper front part at the junction 35, then curves gently downward, and then extends downward again. In addition, the outflow outlet of the outflow pipe section 36 opens downward.

[0029] The collector 37 is connected to the outflow side of the exhaust manifold 33. Specifically, the inlet of the collector 37 is connected to the outlet of the outflow pipe section 36, so that the inside of the outflow pipe section 36 and the inside of the collector 37 communicate with each other. The upper end surface of the collector 37 faces the lower end surface of the outflow pipe section 36 (see FIG. 4). The collector 37 is formed in a cylindrical shape and extends linearly in the vertical direction.

[0030] The outlet of the collector 37 is connected to the inlet of an exhaust outlet hole 11 formed in the engine holder 10. Although not shown, the outlet side of the exhaust outlet hole 11 is connected to a discharge passage provided in the outboard motor 1. The discharge passage extends vertically inside the upper casing 4 and lower casing 6 of the outboard motor 1, and the lower end of the discharge passage reaches the vicinity of the propeller shaft 8. The propeller 9 is also provided with a discharge passage that discharges the exhaust gas carried through the exhaust passage into the water.

[0031] (Catalyst device) Fig. 4 shows an enlarged view of the lower end of the outflow pipe portion 36 of the exhaust manifold 33, the upper end of the collector 37, and the catalytic device 51 in Fig. 3. As shown in Fig. 4, the catalytic device 51 is provided inside the exhaust passage 32, specifically, inside the collector 37. The catalytic device 51 includes a metal catalyst 52, an outer shell portion 53 in which the metal catalyst 52 is housed, and a bracket 54 serving as a holder for holding the catalytic device 51 in the exhaust passage 32.

[0032] The metal catalyst 52 has the function of reducing harmful components contained in the exhaust gas of the engine 21. The metal catalyst 52 is formed by supporting a precious metal such as platinum or palladium on a catalyst carrier formed in a honeycomb shape from steel such as stainless steel. The metal catalyst 52 has a cylindrical outer shape.

[0033] The outer shell portion 53 is formed into a cylindrical shape from steel such as stainless steel. The inner diameter of the outer shell portion 53 is set to a value substantially equal to the outer diameter of the metal catalyst 52 so that no gap is formed between the inner peripheral surface of the outer shell portion 53 and the outer peripheral surface of the metal catalyst 52 housed in the outer shell portion 53. The outer diameter of the outer shell portion 53 is set to a value smaller than the inner diameter of the collector 37 so that the outer shell portion 53 housing the metal catalyst 52 can be housed in the collector 37. The length of the outer shell portion 53 is longer than the length of the metal catalyst 52 and shorter than the length of the collector 37. The metal catalyst 52 is disposed in the outer shell portion 53 at a position slightly lower than the outer shell portion 53, and an empty area E where the metal catalyst 52 is not present is formed in the upper end portion of the outer shell portion 53.

[0034] The bracket 54 is formed from the same material as the outer shell portion 53. The bracket 54 has a cylindrical portion 55 and a protruding portion 56.

[0035] The tubular portion 55 is formed in a cylindrical shape. The outer diameter of the tubular portion 55 is set to a value substantially equal to the inner diameter of the outer shell portion 53. Strictly speaking, the outer diameter of the tubular portion 55 is set to a value slightly smaller than the inner diameter of the outer shell portion 53 so that the lower end portion (the other axial end portion) of the tubular portion 55 fits inside the outer shell portion 53.

[0036] The protruding portion 56 protrudes radially outward from an upper end portion (one axial end portion) of the cylindrical portion 55. The protruding portion 56 protrudes radially outward from the outer peripheral surface of the outer shell portion 53. The protruding portion 56 is formed in a brim or flange shape around the entire circumference of the cylindrical portion 55. As shown in FIG. 4, the outer diameter D1 of the protruding portion 56 is larger than the inner diameter D2 of the upper end portion 37A of the collector 37 and is also larger than the inner diameter D3 of the lower end portion 36A of the outflow pipe portion 36.

[0037] The bracket 54 is joined to the upper end portion (inlet end portion) of the outer shell portion 53. Specifically, the lower end portion of the tubular portion 55 is inserted into the upper portion (inlet side portion) of the outer shell portion 53 from above (inlet side) of the outer shell portion 53, and the lower end portion of the tubular portion 55 and the upper end portion of the outer shell portion 53 are welded. The tubular portion 55 is welded to the upper end portion of the outer shell portion 53 with the outer peripheral surface of the lower end portion in contact with the inner peripheral surface of the outer shell portion 53. Also, the inner peripheral surface of the lower end portion of the tubular portion 55 is closer to the axis C of the outer shell portion 53 than the inner peripheral surface of the upper portion of the outer shell portion 53. Note that 57 in FIG. 4 is a welded portion that joins the tubular portion 55 and the outer shell portion 53.

[0038] The catalytic device 51 having such a configuration is inserted into the collector 37 via the heat insulating material 58. That is, the heat insulating material 58 is provided between the outer peripheral surface of the lower portion (outlet side portion) of the outer shell portion 53 and the inner peripheral surface of the collector 37. The heat insulating material 58 is formed in a mat shape using inorganic fibers such as aluminum oxide fibers (alumina fibers) as its main material.

[0039] During manufacture or maintenance of the exhaust system 31, the catalytic device 51 is pressed into the collector 37 from above (one axial side) after wrapping the insulating material 58 around the outer shell 53. In order to facilitate the operation of pressing the catalytic device 51 into the collector 37, an enlarged diameter portion 38 is formed in the upper portion (one axial side portion) of the collector 37, the diameter of which gradually increases in the direction from the lower side (other axial side) of the collector 37 toward the upper side (one axial side).

[0040] The catalytic converter 51 is held in the collector 37 by pressing it into the collector 37 with insulation material 58 wrapped around the outer shell 53. In addition, the catalytic converter 51 is held in the collector 37 by the protrusion 56 of the bracket 54 being clamped between the lower end 36A (outlet end) of the outlet pipe 36 of the exhaust manifold 33 and the upper end 37A (inlet end) of the collector 37.

[0041] Fig. 5 shows an enlarged view of the catalytic converter 51 in Fig. 4, where the protruding portion 56 of the bracket 54 is sandwiched between the lower end portion 36A of the outflow pipe portion 36 and the upper end portion 37A of the collector 37. As shown in Fig. 5, a step portion 39 is formed around the entire periphery of the upper end surface of the collector 37 such that the inner peripheral portion is lower than the outer peripheral portion. The protruding portion 56 of the bracket 54 is sandwiched between the lower end surface of the outflow pipe portion 36 and the lowered portion on the inner peripheral side of the upper end surface of the collector 37.

[0042] Additionally, an upper joint sheet 61 formed in the shape of a ring-shaped thin plate made of an insulating material is provided between the lower end surface of the outflow pipe section 36 and the upper surface of the protruding section 56 of the bracket 54. The upper joint sheet 61 provides insulation between the outflow pipe section 36 and the bracket 54, which are made of different metals, and has the function of preventing electrolytic corrosion of the outflow pipe section 36 or the bracket 54 (mainly the outflow pipe section 36 made of an aluminum alloy). The upper joint sheet 61 is a specific example of a first insulating member.

[0043] In addition, a lower joint sheet 62 made of an insulating material and formed in a ring-shaped thin plate shape is provided between the lower surface of the protruding portion 56 of the bracket 54 and the lower portion of the upper end surface of the collector 37 on the inner circumferential side. The lower joint sheet 62 provides insulation between the bracket 54 and the collector 37, which are made of different metals, and has a function of preventing electrolytic corrosion of the bracket 54 or the collector 37 (mainly the collector 37 made of an aluminum alloy). For example, a paper gasket can be used as the upper joint sheet 61 and the lower joint sheet 62. The lower joint sheet 62 is a specific example of a second insulating member.

[0044] As shown in FIG. 5 , the inner peripheral portion of the upper joint sheet 61 is interposed between the lower end face of the outflow pipe portion 36 and the upper face of the protruding portion 56 of the bracket 54, while the outer peripheral portion of the upper joint sheet 61 is interposed between the outer peripheral portion of the lower end face of the outflow pipe portion 36 and the outer peripheral portion of the upper end face of the collector 37.

[0045] In the exhaust device 31, exhaust gas flowing out from each exhaust port of the engine 21 flows into each inlet pipe section 34 of the exhaust manifold 33, then joins at the junction 35, and flows from the junction 35 into the outlet pipe section 36. The exhaust gas flowing into the outlet pipe section 36 flows through the outlet pipe section 36 and flows into the collector 37. The exhaust gas flowing into the collector 37 flows inside the metal catalyst 52 of the catalytic device 51. The exhaust gas, whose harmful components have been reduced by flowing through the metal catalyst 52, flows from the collector 37 through the exhaust outlet hole 11 and the discharge passage in that order, and is released into the water from a discharge passage provided in the propeller 9.

[0046] As described above, in the exhaust system 31 according to the embodiment of the present invention, the bracket 54 having the protruding portion 56 is provided on the outer shell portion 53 in which the metal catalyst 52 is housed, and the catalytic converter 51 is held on the collector 37 by the protruding portion 56 of the bracket 54 being sandwiched between the lower end portion 36A of the outlet pipe portion 36 of the exhaust manifold 33 and the upper end portion 37A of the collector 37. With this configuration, the force for holding the catalytic converter 51 on the collector 37 can be increased compared to the case in which the catalytic converter 51 is held only by being pressed into the collector 37 with the insulating material 58 wrapped around the outer periphery of the outer shell portion 53. Therefore, the stability of the catalytic converter 51 on the collector 37 can be improved, and the catalytic converter 51 can be prevented from being displaced from the collector 37 and from falling off the collector 37. Specifically, the catalytic converter 51 can be prevented from shifting out of its vertical position due to vibrations of the engine 21, the catalytic converter 51 can be prevented from falling downward from within the collector 37 due to the impact caused when the ship 81 collides with the water surface while sailing, and the catalytic converter 51 can be prevented from shifting out of its vertical position due to deterioration of the insulation material 58 over time.

[0047] In the exhaust system 31 of this embodiment, an upper joint sheet 61 is provided between the lower end surface of the outflow pipe section 36 of the exhaust manifold 33 and the upper surface of the protruding portion 56 of the bracket 54 to insulate the outflow pipe section 36 and the bracket 54 from each other. This configuration makes it possible to prevent electrolytic corrosion of the outflow pipe section 36 or the bracket 54. Therefore, it is possible to prevent a decrease in the holding force that holds the catalytic device 51 between the outflow pipe section 36 and the collector 37 due to electrolytic corrosion of the outflow pipe section 36 or the bracket 54.

[0048] In the exhaust system 31 of this embodiment, a lower joint sheet 62 is provided between the lower surface of the protruding portion 56 of the bracket 54 and the upper end surface of the collector 37 to insulate the bracket 54 and the collector 37 from each other. This configuration can prevent electrolytic corrosion of the bracket 54 or the collector 37. Therefore, it is possible to prevent a decrease in the holding force that holds the catalytic converter 51 between the outflow pipe portion 36 and the collector 37 due to electrolytic corrosion of the bracket 54 or the collector 37.

[0049] In the catalytic converter 51 of this embodiment, the lower end portion of the tubular portion 55 of the bracket 54 is inserted into the outer shell portion 53 from above the outer shell portion 53 and joined to the outer shell portion 53. As a result, the tubular portion 55 is disposed such that the outer peripheral surface of the lower end portion of the tubular portion 55 contacts the inner peripheral surface of the outer shell portion 53, and the inner peripheral surface of the lower end portion of the tubular portion 55 is closer to the axis C of the outer shell portion 53 than the inner peripheral surface of the upper portion of the outer shell portion 53. With this configuration, it is possible to prevent seawater or condensed water that has entered from the outside from accumulating between the tubular portion 55 and the outer shell portion 53, and it is possible to suppress rusting of the tubular portion 55 or the outer shell portion 53. If the inner diameter of the tubular portion 55 of the bracket 54 were made slightly larger than the outer diameter of the outer shell portion 53 and the upper end portion of the outer shell portion 53 were inserted into the lower end portion of the tubular portion 55 of the bracket 54 to join the two, seawater and condensed water would easily accumulate on the upper end surface of the outer shell portion 53 located inside the tubular portion 55. As a result, the tubular portion 55 or the outer shell portion 53 would easily rust. According to the catalyst device 51 of this embodiment, no place where seawater or condensed water is likely to accumulate is formed between the tubular portion 55 and the outer shell portion 53, so that rusting of the tubular portion 55 or the outer shell portion 53 due to accumulation of seawater or condensed water can be suppressed.

[0050] In the exhaust device 31 of this embodiment, an expanded diameter portion 38 is formed in the upper portion of the collector 37, the diameter of which gradually expands in the direction from the lower portion to the upper portion of the collector 37. This configuration allows the catalytic device 51, whose outer shell portion 53 is wrapped with a heat insulating material 58, to be easily inserted into the collector 37 from above the collector 37, improving the ease of assembling the catalytic device 51 into the collector 37. Specifically, a jig or the like for inserting the catalytic device 51 into the collector 37 is not required, and the catalytic device 51 can be easily inserted into the collector 37 by hand. This reduces the workload of manufacturing or maintaining the exhaust device 31.

[0051] In the above embodiment, the catalytic converter 51 is connected to the outer shell 53 by the bracket 54 having the protruding portion 56. However, the present invention is not limited to this. The retaining portion 74 having the same function as the protruding portion 56 of the bracket 54 may be integrated with the outer shell 73 as shown in FIG. 6. That is, in the catalytic converter 71 shown in FIG. 6, the retaining portion 74 is formed by bending the upper end portion (one axial end portion) of the outer shell 73 so as to protrude radially outward. The retaining portion 74 is sandwiched between the lower end portion 36A of the outflow pipe portion 36 of the exhaust manifold 33 and the upper end portion 37A of the collector 37, so that the catalytic converter 71 can be held on the collector 37. The outer shell 73 integrated with the retaining portion 74 can be formed by, for example, drawing.

[0052] In the above embodiment, the protruding portion 56 of the bracket 54 in the catalytic converter 51 is sandwiched between the exhaust manifold 33 and the collector 37, but the present invention is not limited to this. The protruding portion 56 may be sandwiched between the exhaust manifold and an exhaust pipe other than the collector that constitutes the exhaust passage of the exhaust device, the protruding portion 56 may be sandwiched between the collector and an exhaust pipe other than the exhaust manifold that constitutes the exhaust passage of the exhaust device, or the protruding portion 56 may be sandwiched between two exhaust pipes other than the exhaust manifold or the collector that constitute the exhaust passage of the exhaust device. The protruding portion 56 may also be sandwiched between an exhaust pipe that constitutes the exhaust passage of the exhaust device and a part equivalent to an exhaust pipe.

[0053] In the above embodiment, the catalytic converter 51 is disposed inside the collector 37, but the present invention is not limited to this. For example, the catalytic converter 51 may be disposed inside the outlet pipe 36 of the exhaust manifold 33 by turning the parts of the catalytic converter 51 other than the metal catalyst 52 upside down compared to the above embodiment.

[0054] In addition, if the exhaust manifold 33 and the bracket 54 of the catalytic converter 51 are made of the same metal and do not or are unlikely to cause electrolytic corrosion when they come into contact with each other, and there is no possibility of exhaust gas leakage from the exhaust passage 32, the upper joint sheet 61 may not be provided. Similarly, if the bracket 54 and the collector 37 of the catalytic converter 51 are made of the same metal and do not or are unlikely to cause electrolytic corrosion when they come into contact with each other, the lower joint sheet 62 may not be provided. However, if the exhaust manifold 33 and the collector 37 are made of different metals, a sheet made of an insulating material is provided between the outflow pipe portion 36 of the exhaust manifold 33 and the collector 37.

[0055] Furthermore, the materials of the exhaust manifold 33, the collector 37, and the outer shell 53 and bracket 54 of the catalytic converter 51 are not limited to those in the above embodiment.

[0056] Furthermore, although the exhaust device 31 in the above embodiment is disposed on the left side of the engine 21, the exhaust device of the present invention may be disposed at another location on the engine, such as on the right side of the engine. Furthermore, the number of cylinders in the engine is not limited. Furthermore, the present invention is not limited to exhaust devices for outboard motors, and can also be applied to exhaust devices for other types of marine propulsion devices, such as inboard-outboard motors or inboard motors.

[0057] Furthermore, the present invention can be modified as appropriate within the scope of the claims and the gist or concept of the invention that can be read from the entire specification, and exhaust devices involving such modifications are also included in the technical concept of the present invention. [Explanation of symbols]

[0058] 1. Outboard motor (marine propulsion unit) 21 Engine 31 Exhaust system 32 Exhaust passage 33 Exhaust manifold (first exhaust pipe) 37 Collector (second exhaust pipe) 38 Expanded diameter part 51, 71 Catalytic device 52 Metal Catalyst 53, 73 Outer shell 54 Bracket (holding part) 55 Cylinder part 56 Protrusion 58 Insulation 61 Upper joint sheet (first insulating member) 62 Lower joint sheet (second insulating member) 74 Holding part 81 Ships

Claims

1. An exhaust device that discharges exhaust gas from an engine of a marine propulsion device, an exhaust passage through which the exhaust gas flows; a catalytic converter provided in the exhaust passage for purifying the exhaust gas, The exhaust passage is A first exhaust pipe; a second exhaust pipe connected to an outlet side of the first exhaust pipe, The catalytic converter includes: A metal catalyst having a metal catalyst carrier; a cylindrical outer shell portion containing the metal catalyst therein; a retaining portion provided on the outer shell portion and formed in a flange shape protruding radially outward from an outer circumferential surface of the outer shell portion, for retaining the catalytic converter in the exhaust passage, the catalytic converter is held in the exhaust passage by sandwiching the holding portion between an outlet end of the first exhaust pipe and an inlet end of the second exhaust pipe, an exhaust device characterized in that the first exhaust pipe and the holding portion are formed from different metals, a first insulating member is provided between the first exhaust pipe and the holding portion, and the first exhaust pipe and the holding portion are insulated from each other by the first insulating member.

2. An exhaust system for discharging exhaust gas from an engine of a marine propulsion device, comprising: an exhaust passage through which the exhaust gas flows; a catalytic converter provided in the exhaust passage for purifying the exhaust gas, The exhaust passage is A first exhaust pipe; a second exhaust pipe connected to an outlet side of the first exhaust pipe, The catalytic converter includes: A metal catalyst having a metal catalyst carrier; a cylindrical outer shell portion containing the metal catalyst therein; a retaining portion provided on the outer shell portion and formed in a flange shape protruding radially outward from an outer circumferential surface of the outer shell portion, for retaining the catalytic converter in the exhaust passage, the catalytic converter is held in the exhaust passage by sandwiching the holding portion between an outlet end of the first exhaust pipe and an inlet end of the second exhaust pipe, an exhaust device characterized in that the second exhaust pipe and the holding portion are formed from different metals, a second insulating member is provided between the second exhaust pipe and the holding portion, and the second exhaust pipe and the holding portion are insulated from each other by the second insulating member.

3. The holding portion is A cylindrical portion and a protruding portion protruding radially outward from one axial end portion of the cylindrical portion, The exhaust device according to claim 1 or 2, characterized in that the other axial end portion of the cylindrical portion is inserted into the outer shell portion from the inlet side of the outer shell portion and joined to the outer shell portion so that the outer peripheral surface of the other axial end portion of the cylindrical portion contacts the inner peripheral surface of the inlet side portion of the outer shell portion, and the inlet side end face of the outer shell portion is positioned outside the cylindrical portion.

4. 3. The exhaust device according to claim 1, wherein the retaining portion is formed by bending one axial end of the outer shell portion so as to protrude radially outward.

5. the catalytic converter is disposed in the second exhaust pipe; a heat insulating material is provided between the outer shell portion and the second exhaust pipe, An exhaust system as described in any one of claims 1 to 4, characterized in that an enlarged diameter section is formed in one axial side portion of the second exhaust pipe, the enlarged diameter section gradually enlarging in a direction from the other axial side of the second exhaust pipe toward the one axial side thereof in order to insert the catalytic device and the insulating material into the second exhaust pipe from the one axial side of the second exhaust pipe.

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