Cooling device for ship propulsion machine

Abstract

To sufficiently ensure an ability for collecting a fine object even without using a valve for opening and closing a bypass passage.SOLUTION: In a cooling device for an outboard motor, an upstream part 27A of a drain passage, a collection passage 32 in which a collector 33 is provided, and a bypass passage 34 are arranged such that a difference between a flowing direction of cooling water flowing from the upstream part 27A into a branch part 35 and a flowing direction of the cooling water flowing from the branch part 35 into the collection passage 32 is smaller than a difference between the flowing direction of the cooling water flowing from the upstream part 27A into the branch part 35 and a flowing direction of the cooling water flowing from the branch part 35 into the bypass passage 34.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a cooling device for a marine propulsion machine that has a function of collecting fine particles dispersed in seawater, lake water, or other water. [Background technology]

[0002] In recent years, pollution of oceans, lakes, rivers, etc. caused by the dispersion of fine garbage such as microplastics in seawater, lake water, river water, etc. has become a problem. It is also known that the dispersion of bait residues used in aquaculture in seawater, lake water, river water, etc. pollutes oceans, lakes, rivers, etc. In order to suppress such pollution, it is desirable to capture and recover fine garbage such as microplastics, bait residues, etc. (hereinafter, these are referred to as "fine objects").

[0003] The following Patent Document 1 describes an outboard motor equipped with a cooling device having a function of collecting fine objects. The cooling device uses a pump to take in seawater, lake water, or other water into the outboard motor, and supplies the taken-in water as cooling water to a water jacket provided on the engine of the outboard motor. The cooling water supplied to the water jacket flows through the water jacket, thereby cooling the engine. In addition, the cooling water after flowing through the water jacket flows through a drain pipe, passes through a filter device provided midway through the drain pipe, and is then discharged outside the outboard motor. As the cooling water passes through the filter device, fine objects in the cooling water are captured by the filter device and removed from the cooling water. In this way, according to the cooling device, seawater, lake water, or the like can be taken into the outboard motor, and fine objects contained in the taken-in seawater, lake water, or the like can be collected by the filter device.

[0004] In the cooling device described in Patent Document 1, a bypass passage is connected to the drain pipe in which the filtration device is provided, for allowing the cooling water to flow around the filtration device when the filtration device is clogged. In the cooling device, a relief valve is provided at the connection between the upstream end of the bypass passage and the drain pipe. When the filtration device is not clogged, the relief valve closes to guide the cooling water flowing through the drain pipe to the filtration device, and when the filtration device is clogged, the relief valve opens to guide the cooling water flowing through the drain pipe to the bypass passage, bypassing the filtration device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-163872 A Summary of the Invention [Problem to be solved by the invention]

[0006] 8(A) and (B) show a configuration equivalent to the configuration of the drain side of the conventional cooling device described in the above Patent Document 1. In FIG. 8(A) and (B), 133 is a drain passage. The drain passage 133 corresponds to the drain pipe in the cooling device described in the above Patent Document 1. Also, 135 is a filtration device, 145 is a bypass passage, and 144 is a relief valve. When the filtration device 135 is not clogged, the relief valve 144 is closed as shown in FIG. 8(A). At this time, the cooling water flows through the drain passage 133 so as to pass through the filtration device 135 as shown by the arrow V in FIG. 8(A). On the other hand, when the filtration device 135 is clogged, the relief valve 144 is opened as shown in FIG. 8(B). At this time, the cooling water flows through the bypass passage 145 as shown by the arrow W in FIG. 8(B).

[0007] Incidentally, the inventor of the present application is considering removing the relief valve 144 from the configuration of the drain side of the cooling device as shown in Figures 8(A) and (B), for example. By removing the relief valve 144, the number of parts can be reduced, lowering the manufacturing cost of the cooling device, and also eliminating the occurrence of defects such as breakdowns of the relief valve 144 and the burden of maintaining the relief valve 144. However, removing the relief valve 144 from the configuration of the drain side of the cooling device gives rise to the following problems.

[0008] FIG. 9(A) shows the drainage side configuration of the cooling device shown in FIGS. 8(A) and (B) with the relief valve 144 removed. When the relief valve 144 is removed from the drainage side configuration of the cooling device, the inlet of the bypass passage 145 is always in communication with the drainage passage 133. Therefore, as shown by the arrows X1 and X2 in FIG. 9(A), even when the filtration device 135 is not clogged, the cooling water may flow into the bypass passage 145. As shown by the two-dot chain line in FIG. 9(A), a linear flow path extending from the drainage passage 133 to the bypass passage 145 is formed at the branching portion where the bypass passage 145 branches off from the drainage passage 133, and therefore the flow direction of the cooling water flowing from the drainage passage 133 into the branching portion (arrow X1) and the flow direction of the cooling water flowing from the branching portion into the bypass passage 145 (arrow X2) are the same. In this way, even when the filter device 135 is not clogged, when the cooling water flows into the bypass passage 145, the amount of cooling water flowing through the filter device 135 decreases, and as a result, the ability of the cooling device to capture fine objects decreases.

[0009] In addition, in a configuration in which the relief valve 144 has been removed from the drainage side of the cooling system shown in Figures 8(A) and (B), there is a concern that the cooling water that has flowed through the bypass passage 145 will flow out from the outlet of the bypass passage 145 and then flow back through the drainage passage 133, causing fine objects accumulated in the filtration device 135 to be stirred up, and that the stirred-up fine objects will flow sequentially through the bypass passage 145 and the drainage passage 133 together with the cooling water and be discharged outside the outboard motor.

[0010] 9(B), like FIG. 9(A), shows the drainage side configuration of the cooling device shown in FIG. 8(A) and (B) without the relief valve 144. The cooling water that has flowed through the bypass passage 145 usually flows downward through the drainage passage 133 after flowing out from the outlet of the bypass passage 145, as indicated by arrows Y1 and Y2 in FIG. 9(B). However, if the amount of cooling water flowing through the bypass passage 145 is large, the flow of the cooling water that has flowed through the bypass passage 145 may become turbulent when it flows out from the outlet of the bypass passage 145, and the cooling water may flow back upward through the drainage passage 133, as indicated by arrow Y3 in FIG. 9(B). 9(B), the flow path from the bypass passage 145 to the drain passage 133 is bent at the junction where the bypass passage 145 joins the drain passage 133, and therefore the flow direction (arrow Y1) of the cooling water flowing from the bypass passage 145 into the junction differs from the flow direction (arrow Y2) of the cooling water flowing downward through the drain passage 133 from the junction. When the cooling water flows back through the drain passage 133, the backflowing cooling water flows from bottom to top within the filtration device 135, and there is a risk that fine objects accumulated in the filtration device 135 will be stirred up by this cooling water. In a configuration in which the relief valve 144 is removed, the inlet of the bypass passage 145 is constantly connected to the drain passage 133, so that fine particles that have been stirred up may enter the bypass passage 145 from its inlet together with the cooling water, flow downward through the bypass passage 145 and then the drain passage 133, and be discharged outside the outboard motor. This backflow of the cooling water may cause fine particles that had accumulated in the filtration device 135 to be discharged outside the outboard motor, and therefore this backflow of the cooling water leads to a decrease in the cooling device's ability to collect fine particles.

[0011] In addition, in a configuration in which the relief valve 144 has been removed from the drain side of the cooling system shown in Figures 8(A) and (B), if the power source of the outboard motor is an engine, there is a concern that the engine exhaust gas will flow back up the drain passage 133, causing fine objects accumulated in the filtration device 135 to be stirred up, and that the stirred-up fine objects will flow sequentially through the bypass passage 145 and the drain passage 133 together with the cooling water, and be discharged outside the outboard motor.

[0012] That is, most outboard motors that use an engine as a power source are configured such that an exhaust chamber is provided at the rear of the lower part of the outboard motor, and exhaust gas discharged from the engine is sent to the exhaust chamber through an exhaust passage. When an outboard motor having such a configuration has a water-cooled cooling device, the cooling device is often configured such that cooling water that flows through a drainage passage is discharged into the exhaust chamber. When a cooling device has such a configuration, since the drainage passage and the exhaust passage are connected via the exhaust chamber, when the pressure in the drainage passage becomes lower than the pressure in the exhaust chamber, the exhaust gas sent from the exhaust passage to the exhaust chamber may flow from the exhaust chamber into the drainage passage and backflow through the drainage passage.

[0013] 9(C), like FIG. 9(A) and FIG. 9(B), shows the configuration of the drain side of the cooling device shown in FIG. 8(A) and (B) without the relief valve 144. As indicated by the arrow Z in FIG. 9(C), exhaust gas flowing backward from the exhaust chamber through the drain passage 133 may reach the filter device 135 and flow from bottom to top within the filter device 135. The phenomenon in which exhaust gas flowing backward through the drain passage 133 reaches the filter device 135 is likely to occur when the flow path from below the filter device 135 to the filter device 135 in the drain passage 133 is linear, as indicated by the two-dot chain line in FIG. 9(C), and therefore the exhaust gas flowing backward through the drain passage 133 flows linearly toward the filter device 135. When exhaust gas flows from bottom to top inside the filter device 135, fine particles accumulated inside the filter device 135 are stirred up by the exhaust gas, and the stirred up fine particles flow downward together with the cooling water through the bypass passage 145 and the drain passage 133, and may be discharged outside the outboard motor. Therefore, such a reverse flow of exhaust gas also leads to a decrease in the cooling device's ability to collect fine particles.

[0014] The present invention has been made in consideration of problems such as those described above, and an object of the present invention is to provide a cooling device for a marine propulsion unit that can ensure sufficient fine object collection capacity even without using a valve or the like that opens and closes a bypass passage depending on whether or not the collector (filter) is clogged. [Means for solving the problem]

[0015] In order to solve the above problem, the present invention provides a cooling device for a marine propulsion unit that is provided in a marine propulsion unit, takes in water outside the marine propulsion unit into the marine propulsion unit, flows the taken-in water around or inside a power source of the marine propulsion unit as cooling water to cool the power source, and discharges the cooling water after flowing around or inside the power source to the outside of the marine propulsion unit, the cooling device comprising: a drain passage for discharging the cooling water after flowing around or inside the power source to the outside of the marine propulsion unit; a collection passage interposed between an upstream portion and a downstream portion of the drain passage and connecting the upstream portion and the downstream portion of the drain passage; and a cooling water collector provided midway through the collection passage, which collects the cooling water flowing through the collection passage from the upstream portion of the drain passage to the downstream portion of the drain passage. The drain passage comprises a collector for collecting fine objects contained therein, a bypass passage connected in parallel to the collection passage between the upstream and downstream portions of the drain passage, a branching portion where the upstream portion of the drain passage branches into the collection passage and the bypass passage, and a junction portion where the collection passage and the bypass passage merge into the downstream portion of the drain passage, and the upstream portion of the drain passage, the collection passage and the bypass passage are arranged so that the difference between the flow direction of cooling water flowing from the upstream portion of the drain passage into the branching portion and the flow direction of cooling water flowing from the branching portion into the collection passage is smaller than the difference between the flow direction of cooling water flowing from the upstream portion of the drain passage into the branching portion and the flow direction of cooling water flowing from the branching portion into the bypass passage. Effect of the Invention

[0016] According to the present invention, even if a valve or the like that opens and closes a bypass passage depending on whether the collector is clogged or not is not used, it is possible to ensure sufficient fine object collection capacity. [Brief description of the drawings]

[0017] [Figure 1] 1 is an overall view showing an outboard motor provided with a cooling device according to an embodiment of the present invention; [Diagram 2] 1 is an external view showing an engine of an outboard motor according to an embodiment of the present invention as viewed from the left side; FIG. [Diagram 3]FIG. 3 is an external view showing the engine in FIG. 2 as seen from the rear. [Figure 4] FIG. 1 is an explanatory diagram showing a configuration of a cooling device according to an embodiment of the present invention. [Diagram 5] 1 is an explanatory diagram showing a basic configuration of a fine object collecting device in a cooling device according to an embodiment of the present invention; [Figure 6] 6 is a cross-sectional view taken along line VI-VI in FIG. 3, showing the upstream portion of the drainage passage, the fine object collecting device, and the downstream portion of the drainage passage. [Figure 7] 7 is an enlarged cross-sectional view of the case and the filter cartridge in FIG. 6. [Figure 8] FIG. 13 is an explanatory diagram showing the configuration of the drainage side of a conventional cooling device. [Figure 9] FIG. 1 is an explanatory diagram showing a configuration of a drainage side of a conventional cooling device from which a relief valve has been removed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A cooling device for a marine propulsion unit of an embodiment of the present invention is a cooling device that is provided on a marine propulsion unit, takes in water outside the marine propulsion unit into the marine propulsion unit, cools the power source by flowing the taken-in water around or inside the power source of the marine propulsion unit as cooling water, and discharges the cooling water after flowing around or inside the power source outside the marine propulsion unit.The cooling device is provided with a drainage passage for discharging the cooling water after flowing around or inside the power source to the outside of the marine propulsion unit, a collection passage interposed between the upstream and downstream portions of the drainage passage and connecting the upstream and downstream portions of the drainage passage, a collector provided midway through the collection passage and collecting fine objects contained in the cooling water that flows through the collection passage from the upstream portion of the drainage passage to the downstream portion of the drainage passage, a bypass passage connected in parallel to the collection passage between the upstream and downstream portions of the drainage passage, a branching portion where the upstream portion of the drainage passage branches into the collection passage and the bypass passage, and a junction portion where the collection passage and the bypass passage merge into the downstream portion of the drainage passage.

[0019] In addition, in the cooling device of this embodiment, the upstream portion of the drain passage, the collection passage and the bypass passage are arranged so that the difference between the flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and the flow direction of the cooling water flowing from the branch portion into the collection passage is smaller than the difference between the flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and the flow direction of the cooling water flowing from the branch portion into the bypass passage.

[0020] By arranging the upstream part of the drainage passage, the collection passage, and the bypass passage in this manner, when the collector is not clogged, the cooling water flowing out from the upstream part of the drainage passage is more likely to flow into the collection passage than into the bypass passage. Therefore, without using a valve or the like that opens and closes the bypass passage depending on whether the collector is clogged or not, most of the cooling water flowing out from the upstream part of the drainage passage when the collector is not clogged can be smoothly flowed into the collection passage and sent to the collector. In other words, even if the upstream part of the drainage passage and the inlet of the bypass passage are always in communication with each other, it is possible to prevent the cooling water flowing out from the upstream part of the drainage passage from flowing into the bypass passage when the collector is not clogged. Therefore, when the collector is not clogged, it is possible to prevent the amount of cooling water flowing in the collector from decreasing due to the cooling water flowing into the bypass passage, and to prevent the cooling device's ability to collect fine objects from decreasing.

[0021] In addition, in the cooling device of this embodiment, the downstream portion of the drain passage, the collection passage and the bypass passage are arranged so that the difference between the flow direction of the cooling water flowing from the bypass passage into the junction and the flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage is smaller than the difference between the flow direction of the cooling water flowing from the collection passage to the junction and the flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage.

[0022] By arranging the downstream portion of the drainage passage, the collection passage, and the bypass passage in this manner, the flow direction of the cooling water from the bypass passage to the downstream portion of the drainage passage can be made close to a straight line or made straight. Therefore, when the collector is clogged, the cooling water can be made to flow smoothly from the bypass passage to the downstream portion of the drainage passage, and the cooling water that has flowed through the bypass passage can be prevented from flowing back through the collection passage. Furthermore, by arranging the downstream portion of the drainage passage, the collection passage, and the bypass passage as described above, when exhaust gas flows back through the downstream portion of the drainage passage from the exhaust chamber of the marine propulsion device, the flow direction of the exhaust gas from the downstream portion of the drainage passage to the bypass passage can be made close to a straight line or made straight, and the flow direction of the exhaust gas from the downstream portion of the drainage passage to the collection passage can be bent. Therefore, the exhaust gas that has flowed back through the downstream portion of the drainage passage from the exhaust chamber of the marine propulsion device can be made to flow smoothly into the bypass passage, and the exhaust gas that has flowed back through the downstream portion of the drainage passage can be prevented from flowing back through the collection passage.

[0023] In this way, by suppressing the backflow of the cooling water or exhaust gas into the collection passage, it is possible to suppress the fine objects accumulated in the collector from being lifted up by the cooling water or exhaust gas passing through the collector from bottom to top. Therefore, even if the inlet of the collection passage and the inlet of the bypass passage are always in communication with each other at the branching portion, it is possible to suppress the fine objects once accumulated in the collector from being lifted up and discharged to the outside of the marine propulsion machine through the bypass passage and the downstream part of the drainage passage. In this way, according to this embodiment, even if a valve or the like for opening and closing the bypass passage depending on whether the collector is clogged is not provided, it is possible to suppress the fine objects once accumulated in the collector from being discharged to the outside of the marine propulsion machine due to the backflow of the cooling water or exhaust gas, and therefore it is possible to sufficiently ensure the fine object collection capacity of the cooling device. EXAMPLES

[0024] Hereinafter, an embodiment of the cooling device for a marine propulsion unit of the present invention will be described with reference to Figures 1 to 7. In the embodiment, when describing the directions of front (Fd), rear (Bd), top (Ud), bottom (Dd), left (Ld), and right (Rd), please refer to the arrows drawn at the bottom left of Figures 1 to 7.

[0025] (Outboard motor) FIG. 1 shows an outboard motor 1, which is one form of marine propulsion device, as viewed from the left. As shown in FIG. 1, the outboard motor 1 includes an engine 2 as a power source, a drive shaft 3 that rotates by receiving power from the engine 2, a propeller 4 that generates propulsive power for the marine vessel, a propeller shaft 5 to which the propeller 4 is attached, and a gear mechanism 6 that transmits the rotation of the drive shaft 3 to the propeller shaft 5. Although not shown, the gear mechanism 6 is provided with a shift device that switches the direction of rotation transmitted from the drive shaft 3 to the propeller shaft 5. The engine 2 is disposed in an upper portion of the outboard motor 1. The gear mechanism 6, the propeller shaft 5, and the propeller 4 are disposed in a lower portion of the outboard motor 1. The drive shaft 3 extends in the vertical direction between the engine 2 and the gear mechanism 6.

[0026] Furthermore, the lower part of the engine 2 is covered by an engine bottom cover 7, and the vertical middle and upper parts of the engine 2 are covered by an engine top cover 8. The engine top cover 8 is detachably attached to the engine bottom cover 7. By removing the engine top cover 8, a wide range of the engine 2 from the vertical middle to the upper part can be exposed. Furthermore, the upper part of the drive shaft 3 is covered by an upper case 9, and the vertical middle part of the drive shaft 3 is covered by a middle case 10. Furthermore, the lower part of the drive shaft 3, and the front part of the gear mechanism 6 and the propeller shaft 5 are covered by a lower case 11.

[0027] Fig. 2 shows the engine 2 as seen from the left. Fig. 3 shows the engine 2 as seen from the rear. The engine 2 is, for example, a four-stroke, four-cylinder gasoline engine, and is cooled by water. The engine 2 is arranged so that the extension direction of the crankshaft is the vertical direction. As shown in Fig. 2, the engine 2 has a crankcase 12 arranged at the front, a cylinder block 13 arranged behind the crankcase 12, and a cylinder head 14 arranged behind the cylinder block 13. The rear of the cylinder head 14 is covered by a cylinder head cover 15.

[0028] As shown in FIG. 1, the outboard motor 1 is provided with an exhaust passage 16 for discharging exhaust gas discharged from the engine 2 to the outside of the outboard motor 1. The upper end of the exhaust passage 16 is connected to an exhaust port provided in a cylinder head 14 of the engine 2, and the lower end of the exhaust passage 16 is connected to an exhaust chamber 17 provided in a rear part of the lower part of the outboard motor 1. In the outboard motor 1 of this embodiment, the exhaust chamber 17 is provided in a portion extending from the rear part of the middle case 10 to the rear part of the lower case 11. Exhaust gas discharged from an exhaust port of the engine 2 is sent to the exhaust chamber 17 via the exhaust passage 16, and is then discharged to the outside of the outboard motor 1 via an exhaust port provided in a shaft part of the propeller 4, for example. Note that the exhaust port of the engine 2 and the exhaust passage 16 are not shown in FIG. 2 and FIG. 3.

[0029] (cooling device) The outboard motor 1 is equipped with a cooling device 21 that uses the water around the outboard motor 1, such as seawater, lake water, or river water, as cooling water to cool the engine 2 and other heat-generating parts of the outboard motor 1. Figure 4 shows the configuration of the cooling device 21.

[0030] As shown in FIG. 4, the cooling device 21 includes a water intake port 22, a water intake passage 23, a water pump 24, a water supply passage 25, a water jacket 26, a drain passage 27, a thermostat 28, a pressure valve 29, and a fine object collecting device 31.

[0031] The water intake 22 is an opening for taking in water around the outboard motor 1 into the outboard motor 1, and is provided in a portion of the outboard motor 1 that is submerged under the water surface, specifically, in a part of the lower case 11 (see FIG. 1). The water intake 22 is also provided with a strainer or a cover with many small holes to prevent stones, seaweed, and other objects larger than minute objects from entering the outboard motor 1 together with seawater, lake water, or river water.

[0032] The water intake passage 23 is a passage for sucking water taken into the outboard motor 1 from the water intake port 22 into the water pump 24, and is provided inside the lower case 11.

[0033] The water pump 24 is a pump that sucks up water taken into the outboard motor 1 through the water intake 22 and discharges the sucked up water as cooling water, and is provided, for example, inside the lower case 11 or the middle case 10. The water pump 24 is operated by utilizing the rotation of the drive shaft 3.

[0034] The water supply passage 25 is a passage for sending the cooling water discharged from the water pump 24 to the water jacket 26, and is formed, for example, by a hose or pipe provided inside the middle case 10, the upper case 9, and the engine bottom cover 7.

[0035] The water jacket 26 is a mechanism for cooling the engine 2 by causing the cooling water fed via the water supply passage 25 to flow around or inside the engine 2, and is provided around or inside the engine 2.

[0036] The drain passage 27 is a passage for discharging the cooling water after flowing through the water jacket 26 to the outside of the outboard motor 1, and is formed by, for example, a hose or a pipe provided inside the engine top cover 8, the engine bottom cover 7, and the upper case 9. A fine object collecting device 31 is interposed in the middle of the drain passage 27, and therefore the drain passage 27 is divided into an upstream portion 27A which is the portion upstream of the fine object collecting device 31, and a downstream portion 27B which is the portion downstream of the fine object collecting device 31.

[0037] As shown in FIG. 2 and FIG. 3, the upstream portion 27A of the drain passage 27 is disposed in an area extending from above the cylinder head 14 to the left of the upper portion of the cylinder head cover 15. The upstream portion 27A of the drain passage 27 is formed of a heat-resistant and highly rigid resin or metal pipe having high corrosion resistance, or a heat-resistant and highly rigid rubber hose. The upper end of the upstream portion 27A of the drain passage 27 is connected to the outlet 26A of the water jacket 26 disposed at the upper portion of the cylinder head 14. The upstream portion 27A of the drain passage 27 extends leftward from the outlet 26A of the water jacket 26 and then bends, then extends rearward while inclining downward on the left side of the rear upper portion of the engine 2, then bends, then extends horizontally rearward on the left side of the rear upper portion of the engine 2, then bends, and then extends vertically downward on the left side of the rear upper portion of the engine 2. The lower end of the upstream portion 27A of the drain passage 27 faces downward. In addition, the lower end of the upstream portion 27A of the drainage passage 27 is connected to the upper ends of the collection passage 32 and bypass passage 34 of the fine object collection device 31 (specifically, the upper end of the inlet pipe portion 41A of the branch pipe 41).

[0038] The downstream portion 27B of the drain passage 27 is disposed in a region extending from the lower left portion of the rear of the engine 2 to the exhaust chamber 17. The upper end of the downstream portion 27B of the drain passage 27 is formed by a drain hole 30 formed in the lower left portion of the rear of the housing of the engine 2. The drain hole 30 extends downward, although it is slightly inclined to the right, and the upper end of the drain hole 30 faces upward. The upper end of the drain hole 30 is connected to the lower end of the collection passage 32 and the bypass passage 34 (specifically, the lower end of the outflow pipe portion 54C of the junction pipe 54). In the downstream portion 27B of the drain passage 27, the portion below the drain hole 30 is formed by a hose or a pipe provided inside the engine bottom cover 7 and the upper case 9, etc. The lower end of the downstream portion of the drain passage 27 is connected to the exhaust chamber 17 as shown in FIG. 4.

[0039] The thermostat 28 is a device that limits the flow of cooling water to warm up the engine 2 or to prevent overcooling of the engine 2, and is provided, for example, near the outlet 26A of the water jacket 26. The thermostat 28 opens when the temperature of the cooling water flowing inside the water jacket 26 becomes equal to or higher than a predetermined reference temperature, and closes when the temperature of the cooling water becomes lower than the reference temperature.

[0040] The pressure valve 29 is a valve for lowering the water pressure in the water supply passage 25 or the water jacket 26 by releasing the cooling water discharged from the water pump 24 toward the exhaust chamber 17 when the flow of the cooling water is restricted by the thermostat 28. The pressure valve 29 is, for example, a normally closed valve, and opens when the water pressure in the water supply passage 25 exceeds a predetermined reference pressure.

[0041] The fine object collecting device 31 is a device that collects fine objects contained in seawater, lake water, river water, or the like that is taken into the outboard motor 1 from outside the outboard motor 1 and used as cooling water for cooling the engine 2. The fine object collecting device 31 will be described in detail later.

[0042] In the cooling device 21 having such a configuration, when the water pump 24 is operating, the thermostat 28 is open, and the pressure valve 29 is closed, water around the outboard motor 1 is taken into the outboard motor 1 through the water intake port 22, and the water flows through the water intake passage 23 and the water supply passage 25 in this order, and is sent to the water jacket 26 as cooling water. The cooling water sent to the water jacket 26 flows inside the water jacket 26, thereby cooling the engine 2. The cooling water that has flowed inside the water jacket 26 flows from the outlet 26A of the water jacket 26 into the upstream portion 27A of the drain passage 27, flows through the upstream portion 27A of the drain passage 27, then flows through the fine object collecting device 31, then flows through the downstream portion 27B of the drain passage 27, and is then discharged into the exhaust chamber 17. The cooling water discharged into the exhaust chamber 17 is discharged outside the outboard motor 1 together with the exhaust gas, for example, through a discharge port provided on the shaft of the propeller 4. On the other hand, when the water pump 24 is operating, the thermostat 28 is closed, and the pressure valve 29 is open, water taken into the outboard motor 1 from the water intake 22 flows successively through the water intake passage 23 and the water supply passage 25, but before reaching the water jacket 26, it is sent to the exhaust chamber 17 side via the open pressure valve 29 and released into the exhaust chamber 17. The cooling water released into the exhaust chamber 17 is discharged outside the outboard motor 1 together with the exhaust gas.

[0043] (fine object collection device) As described above, the fine object collecting device 31 is a device that collects fine objects contained in seawater, lake water, river water, etc. that is taken into the outboard motor 1 from outside and used as cooling water for cooling the engine 2. As shown in Figures 2 and 3, the fine object collecting device 31 is disposed on the left side of the rear of the engine 2. The fine object collecting device 31 is also disposed inside the engine top cover 8.

[0044] The fine objects are, for example, minute garbage such as microplastics, or residue of bait used in aquaculture. The size of the fine objects is, for example, about 0.1 mm or more and about 5 mm or less. Because of such a size, the fine objects cannot be removed by a strainer or a cover having many small holes provided on the water intake 22. That is, when the water pump 24 is operating, the thermostat 28 is open, and the pressure valve 29 is closed, the fine objects enter the outboard motor 1 from the water intake 22 together with seawater, lake water, river water, etc., and flow into the fine object collecting device 31 through the water intake passage 23, the water supply passage 25, the water jacket 26, and the upstream portion 27A of the drain passage 27.

[0045] Fig. 5 shows a basic configuration of fine object collecting device 31. As shown in Fig. 5, fine object collecting device 31 includes a collecting passage 32, a collector 33, a bypass passage 34, a branching portion 35, and a junction portion 36.

[0046] The collection passage 32 is a passage that is interposed between the upstream portion 27A and the downstream portion 27B of the drainage passage 27 and connects the upstream portion 27A and the downstream portion 27B of the drainage passage 27. The collection passage 32 causes the cooling water flowing through the upstream portion 27A of the drainage passage 27 to flow to the downstream portion 37B of the drainage passage 27 via the collector 33.

[0047] The collector 33 is provided midway through the collection passage 32 and is a device for collecting fine objects contained in the cooling water that passes through the collection passage 32 and flows from the upstream portion 27A of the drain passage 27 toward the downstream portion 27B of the drain passage 27. As will be described later, the collector 33 captures fine objects in the cooling water by passing the cooling water flowing through the collection passage 32 through a filter 43, thereby removing the fine objects from the cooling water.

[0048] The bypass passage 34 is a passage connected in parallel to the collection passage 32 between the upstream portion 27A and the downstream portion 27B of the drainage passage 27. When the filter 43 of the collector 33 becomes clogged, for example, the bypass passage 34 directs the cooling water flowing through the upstream portion 27A of the drainage passage 27 to the downstream portion 37B of the drainage passage 27 without passing through the collector 33.

[0049] The branching portion 35 is a portion where the upstream portion 27A of the drainage passage 27 branches into the collection passage 32 and the bypass passage 34. The merging portion 36 is a portion where the collection passage 32 and the bypass passage 34 merge into the downstream portion 27B of the drainage passage 27.

[0050] (Arrangement of collection passages and bypass passages at branching points) In Figure 5, the upstream portion 27A of the drainage passage 27, the collection passage 32, and the bypass passage 34 are arranged so that the difference between the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is smaller than the difference between the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34.

[0051] Specifically, the upstream portion 27A of the drainage passage 27 and the collection passage 32 are arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 is the same as the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32. In contrast, the upstream portion 27A of the drainage passage 27 and the bypass passage 34 are arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 is different from the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34.

[0052] More specifically, the upstream portion 27A of the drain passage 27 is disposed so that the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 into the branch portion 35 is downward and vertical, as indicated by arrow A. The collection passage 32 is disposed so that the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is downward and vertical, as indicated by arrow B. In contrast, the bypass passage 34 is disposed so that the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34 is not vertical, as indicated by arrow C.

[0053] In this embodiment, the lower end of the upstream portion 27A of the drain passage 27 and the upper end of the collection passage 32, which are connected to each other at the branch portion 35, both extend vertically and are arranged coaxially with each other. As a result, a straight flow path extending vertically is formed from the lower end of the upstream portion 27A of the drain passage 27 to the upper end of the collection passage 32. In contrast, the upper end of the bypass passage 34, which is connected to the lower end of the upstream portion 27A of the drain passage 27 at the branch portion 35, is inclined with respect to the vertical. As a result, a curved flow path is formed from the lower end of the upstream portion 27A of the drain passage 27 to the upper end of the bypass passage 34.

[0054] At the branching portion 35, the collection passage 32 and the bypass passage 34 intersect with each other at an acute angle. The angle P between the upper end of the collection passage 32 and the upper end of the bypass passage 34 is, for example, equal to or greater than about 20 degrees and less than 90 degrees. Note that the upper end of the bypass passage 34 may be extended horizontally so that the collection passage 32 and the bypass passage 34 intersect with each other at a right angle at the branching portion 35, in which case P becomes 90 degrees.

[0055] (Layout of collection passages and bypass passages at junctions) The collection passage 32, the bypass passage 34, and the downstream portion 27B of the drain passage 27 are arranged so that the difference between the flow direction of the cooling water flowing from the bypass passage 34 into the junction 36 and the flow direction of the cooling water flowing from the junction 36 into the downstream portion 27B of the drain passage 27 is smaller than the difference between the flow direction of the cooling water flowing from the collection passage 32 into the junction 36 and the flow direction of the cooling water flowing from the junction 36 into the downstream portion 27B of the drain passage 27.

[0056] Specifically, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged so that the flow direction of the cooling water flowing from the bypass passage 34 into the junction 36 and the flow direction of the cooling water flowing from the junction 36 into the downstream portion 27B of the drain passage 27 are substantially the same as each other. In contrast, the collection passage 32 and the downstream portion 27B of the drain passage 27 are arranged so that the flow direction of the cooling water flowing from the collection passage 32 into the junction 36 and the flow direction of the cooling water flowing from the junction 36 into the downstream portion 27B of the drain passage 27 are different from each other.

[0057] The reason why the relationship between the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 and the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27 is described as "substantially the same" is because, as shown in Fig. 3, when the engine 2 is viewed from the rear, the upper end portion (drain hole 30) of the downstream portion 27B of the drain passage 27 is slightly inclined to the right with respect to the vertical. The fact that the upper end portion of the downstream portion 27B of the drain passage 27 is slightly inclined to the right with respect to the vertical does not substantially reduce the effect of the cooling device 21 of this embodiment, which is to suppress the backflow of the cooling water that has flowed through the bypass passage 34 into the collection passage 32, and does not substantially reduce the effect of the cooling device 21 of this embodiment, which is to suppress the exhaust gas that has flowed back from the exhaust chamber 17 from flowing into the collection passage 32 from the lower end portion of the collection passage 32.

[0058] More specifically, the bypass passage 34 is disposed so that the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 is downward and vertical, as indicated by arrow E. Furthermore, the downstream portion 27B of the drainage passage 27 is disposed so that the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drainage passage 27 is downward and approximately vertical, as indicated by arrow F. In contrast, the collection passage 32 is disposed so that the flow direction of the cooling water flowing from the collection passage 32 to the junction 36 is not vertical, as indicated by arrow D.

[0059] In this embodiment, the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drain passage 27 are connected to each other at the junction 36, the lower end of the bypass passage 34 extends vertically, the upper end of the downstream portion 27B of the drain passage 27 extends approximately vertically, and the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drain passage 27 are arranged approximately coaxially with each other. As a result, a substantially straight flow path extending approximately vertically is formed from the lower end of the bypass passage 34 to the upper end of the downstream portion 27B of the drain passage 27. In contrast, the lower end of the collection passage 32 connected to the upper end of the downstream portion 27B of the drain passage 27 at the junction 36 is inclined relative to the vertical. As a result, a curved flow path is formed from the lower end of the collection passage 32 to the upper end of the downstream portion 27B of the drain passage 27.

[0060] Furthermore, at the junction 36, the collection passage 32 and the bypass passage 34 intersect with each other at an acute angle. The angle Q between the lower end of the collection passage 32 and the lower end of the bypass passage 34 is, for example, equal to or greater than about 20 degrees and less than 90 degrees. Note that the lower end of the collection passage 32 may be extended horizontally so that the collection passage 32 and the bypass passage 34 intersect with each other at a right angle at the junction 36, in which case Q becomes 90 degrees.

[0061] The collection passage 32 extends vertically downward from the branching portion 35, then bends, and then extends downward while inclining relative to the vertical, reaching the junction 36. The collector 33 is provided midway along the vertically extending portion of the collection passage 32. The bypass passage 34 extends downward from the branching portion 35 while inclining relative to the vertical, then bends, and then extends vertically downward, reaching the junction 36.

[0062] (Flow of cooling water in a fine object collection device) In FIG. 5, the lower end of the upstream portion 27A of the drain passage 27 and the upper end of the collection passage 32 both extend vertically. The lower end of the upstream portion 27A of the drain passage 27 and the upper end of the collection passage 32 are arranged coaxially with each other, and a straight flow path extending vertically is formed from the lower end of the upstream portion 27A of the drain passage 27 to the upper end of the collection passage 32. Therefore, the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 to the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 to the collection passage 32 are both downward and vertical, as shown by arrows A and B, and are the same as each other. In contrast, the upper end of the bypass passage 34 is inclined with respect to the vertical, and a bent flow path is formed from the lower end of the upstream portion 27A of the drain passage 27 to the upper end of the bypass passage 34. Therefore, the flow direction of the cooling water flowing from the branch portion 35 to the bypass passage 34 is not vertical, as shown by arrow C. As a result, the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 to the branch portion 35 differs from the flow direction of the cooling water flowing from the branch portion 35 to the bypass passage 34. Therefore, when the filter 43 of the collector 33 is not clogged, most of the cooling water flowing from the upstream portion 27A of the drain passage 27 to the branch portion 35 flows into the collection passage 32. The cooling water that flows into the collection passage 32 passes through the filter 43 in the collector 33. When the cooling water passes through the filter 43, fine objects in the cooling water are removed. The cooling water that has passed through the filter 43 flows into the downstream portion 27B of the drain passage 27 through the lower portion of the collection passage 32 and the junction portion 36 in this order. In this way, according to this embodiment, when the filter 43 of the collector 33 is not clogged, most of the cooling water flowing out from the upstream portion 27A of the drainage passage 27 can be made to flow into the collection passage 32 and sent to the collector 33 without using a valve or the like that opens and closes the bypass passage 34 depending on whether the filter 43 of the collector 33 is clogged or not.

[0063] On the other hand, when the filter 43 of the collector 33 is clogged, it becomes difficult for the cooling water to pass through the filter 43, and the flow of the cooling water is stagnated in the collector 33 and in the upper part of the collection passage 32 (the part above the collector 33). Therefore, when the filter 43 of the collector 33 is clogged, most of the cooling water that flows from the upstream part 27A of the drain passage 27 to the branch part 35 flows into the bypass passage 34, and flows into the downstream part 27B of the drain passage 27 through the bypass passage 34 and the junction part 36 in order. Here, the lower end of the bypass passage 34 extends vertically, the upper end of the downstream part 27B of the drain passage 27 extends approximately vertically, and the lower end of the bypass passage 34 and the upper end of the downstream part 27B of the drain passage 27 are arranged approximately coaxially with each other. As a result, a substantially straight flow path extending approximately vertically from the lower end of the bypass passage 34 to the upper end of the downstream part 27B of the drain passage 27 is formed. Therefore, the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 and the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27 are both downward and substantially vertical, as indicated by arrows E and F, and are substantially the same as each other. Therefore, the cooling water flows smoothly and substantially vertically downward in a substantially straight line from the bypass passage 34 to the downstream portion 27B of the drain passage 27. Therefore, according to this embodiment, it is possible to prevent the flow of the cooling water flowing from the bypass passage 34 to the junction 36 from being disturbed and flowing back through the collection passage 32 from the lower end of the bypass passage 34. Therefore, it is possible to prevent the fine objects accumulated in the filter 43 of the collector 33 from being stirred up by the cooling water passing from the bottom to the top inside the collector 33.

[0064] (Flow of exhaust gases flowing backwards from the exhaust chamber) As can be seen from FIG. 1 and FIG. 4, the exhaust passage 16 and the downstream portion 27B of the drain passage 27 are connected to the exhaust chamber 17 of the outboard motor 1. As a result, the exhaust passage 16 and the downstream portion 27B of the drain passage 27 are connected via the exhaust chamber 17. Therefore, when the pressure in the downstream portion 27B of the drain passage 27 becomes lower than the pressure in the exhaust chamber 17, the exhaust gas sent from the exhaust passage 16 to the exhaust chamber 17 may flow from the exhaust chamber 17 into the downstream portion 27B of the drain passage 27 and flow back through the downstream portion 27B of the drain passage 27. In the outboard motor 1, the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drain passage 27 both extend approximately vertically. In addition, the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drain passage 27 are arranged approximately coaxially with each other, and a substantially straight flow path extending approximately vertically is formed from the lower end of the bypass passage 34 to the upper end of the downstream portion 27B of the drain passage 27. Therefore, most of the exhaust gas that flows back through the downstream portion 27B of the drain passage 27 flows in a substantially straight line from bottom to top in this substantially straight flow passage. That is, most of the exhaust gas that flows back smoothly flows from the downstream portion 27B of the drain passage 27 into the bypass passage 34. Then, the exhaust gas that flows into the bypass passage 34 flows from bottom to top through the bypass passage 34, and then flows through the branch portion 35 to the upstream portion 27A of the drain passage 27. In this way, according to this embodiment, it is possible to prevent the exhaust gas that flows back through the downstream portion 27B of the drain passage 27 from flowing into the collection passage 32, and the fine objects accumulated in the filter 43 of the collector 33 from being stirred up by the exhaust gas that flows back from bottom to top through the collector 33.

[0065] (Details of the configuration of the fine object collection device) Fig. 6 shows the details of the configuration of the fine object collecting device 31, and shows a cross section of the upstream portion 27A of the drainage passage 27, the fine object collecting device 31, and the upper end portion of the downstream portion 27B of the drainage passage 27, taken along the section line VI-VI in Fig. 3, as viewed from the left. Fig. 7 shows an enlarged view of the collector 33 in Fig. 6.

[0066] Specifically, as shown in FIG. 6, the fine object collecting device 31 includes a branch pipe 41, a collector 33, a connection hose 51, a bypass pipe 52, a connecting pipe 53, and a junction pipe 54. The first outlet pipe section 41B of the branch pipe 41, the connecting hose 51, and the first inlet pipe section 54A of the junction pipe 54 form a collecting passage 32. The second outlet pipe section 41C of the branch pipe 41, the bypass pipe 52, the connecting pipe 53, and the second inlet pipe section 54B of the junction pipe 54 form a bypass passage 34. In the branch pipe 41, the part where the inlet pipe section 41A branches into the first outlet pipe section 41B and the second outlet pipe section 41C corresponds to the branch section 35. In the junction pipe 54, the part where the first inlet pipe section 54A and the second inlet pipe section 54B join the outlet pipe section 54C corresponds to the junction section 36.

[0067] The branch pipe 41 is a pipe that connects the upstream portion 27A of the drain passage 27 to the collector 33, and also connects the upstream portion 27A of the drain passage 27 to the bypass pipe 52. The branch pipe 41 is formed of a resin having high heat resistance and rigidity, or a metal having high corrosion resistance, or the like. The branch pipe 41 has an inflow pipe section 41A, a first outflow pipe section 41B, and a second outflow pipe section 41C. In the branch pipe 41, the inflow pipe section 41A is located on the upper side, and the first outflow pipe section 41B is located on the lower side. The inflow pipe section 41A and the first outflow pipe section 41B are arranged coaxially, and the portion of the branch pipe 41 from the inflow pipe section 41A to the first outflow pipe section 41B extends vertically in a straight line. In addition, the inflow pipe section 41A is arranged coaxially with the lower end of the upstream portion 27A of the drain passage 27, and the upper end of the inflow pipe section 41A is connected to the lower end of the upstream portion 27A of the drain passage 27. The second outflow pipe section 41C extends forward while inclining downward from a substantially vertical middle portion of the portion of the branch pipe 41 extending from the inflow pipe section 41A to the first outflow pipe section 41B.

[0068] The collector 33 has a filter cartridge 42 and a case 46. As shown in FIG. 7, the filter cartridge 42 has a filter 43 that captures fine objects and allows cooling water to pass through, and a holder 44 that holds the filter 43. The filter 43 is formed, for example, from a nonwoven fabric or a resin mesh, and is formed in a bag shape with an open upper side and a closed lower side. The holder 44 is formed in a cylindrical shape with a vertically extending axis, from a heat-resistant and highly rigid resin, or a highly corrosion-resistant metal, etc. In addition, a plurality of water passage holes 45 are provided in the peripheral wall of the holder 44. The filter 43 is disposed inside the holder 44 so as to cover each water passage hole 45 and the opening on the lower side of the holder 44. In addition, the upper part of the filter 43 is attached to the inner peripheral surface of the upper part of the holder 44 by, for example, an adhesive, and is fixed inside the holder 44 with the upper part of the filter 43 open upward.

[0069] The case 46 is a member that houses the filter cartridge 42. The case 46 is made of a heat-resistant and highly rigid resin, or a highly corrosion-resistant metal, and is formed into a cylindrical shape having an axis that extends vertically. The case 46 is divided into an upper case portion 47 that forms an upper portion of the case 46, and a lower case portion 48 that forms a lower portion of the case 46. The filter cartridge 42 is held between the upper case portion 47 and the lower case portion 48. The filter cartridge 42 is disposed coaxially with the case 46.

[0070] The lower end of the first outflow pipe portion 41B of the branch pipe 41 is connected to the upper opening of the upper case portion 47. In this embodiment, the upper case portion 47 is integrally formed with the first outflow pipe portion 41B of the branch pipe 41. In addition, a connecting pipe portion 49 is provided below the lower case portion 48, and the lower case portion 48 and the connecting pipe portion 49 are integral with each other.

[0071] The lower case part 48 is separably connected to the upper case part 47 by a connecting member 50. The connecting member 50 is formed in a cylindrical shape from, for example, resin or metal. The connecting member 50 is held on the outer periphery of the lower case part 48 so as to be rotatable relative to the lower case part 48 and to be vertically movable relative to the lower case part 48. A screw is formed on the outer periphery of the lower end part of the upper case part 47 and on the inner periphery of the connecting member 50, and the lower case part 48 is connected to the upper case part 47 by screwing the connecting member 50, which is rotatably held by the lower case part 48, to the lower end part of the upper case part 47. The lower case part 48 is separated from the upper case part 47 by rotating the connecting member 50 in a direction that loosens the screw and removing it from the lower end part of the upper case part 47.

[0072] The connection hose 51 is a pipe that connects the case 46 and the first inlet pipe portion 54A of the junction pipe 54. The connection hose 51 is formed of a rubber hose that is heat-resistant and highly rigid. The connection hose 51 has high rigidity but is flexible. As shown in FIG. 6, the upper end of the connection hose 51 is arranged coaxially with the case 46 and is connected to the lower end of the connection pipe portion 49 that is integrally formed with the lower case portion 48. The connection hose 51 extends vertically downward from its upper end, then bends gently, then extends downward while inclining to the right rear, then bends gently, and then extends downward while inclining to the left front. In this way, since a part of the connection hose 51 is inclined with respect to the vertical, the coupling member 50 is rotated in a direction that loosens the screw to make the lower case portion 48 separable from the upper case portion 47, and then the upper end of the connection hose 51 can be gripped by hand and pushed down to pull the lower case portion 48 away from the upper case portion 47. The filter cartridge 42 can be removed from the case 46 by pulling the lower case part 48 away from the upper case part 47. By removing the filter cartridge 42 from the case 46 in this manner, the user can remove fine objects accumulated in the filter 43.

[0073] The bypass pipe 52 is formed of a heat-resistant and highly rigid rubber hose, or a heat-resistant and highly rigid resin or corrosion-resistant metal pipe, etc. The upper end of the bypass pipe 52 is connected to the lower end of the second outflow pipe portion 41C of the branch pipe 41. The bypass pipe 52 extends downward from its upper end while inclining forward with respect to the vertical, then bends, and then extends vertically downward.

[0074] The connecting pipe 53 is formed of a resin having high heat resistance and rigidity, or a metal having high corrosion resistance, etc. The connecting pipe 53 extends vertically and is disposed coaxially with the bypass pipe 52. The upper end of the connecting pipe 53 is connected to the lower end of the bypass pipe 52.

[0075] The junction pipe 54 is a pipe that connects the connection hose 51 and the downstream portion 27B of the drain passage 27, and connects the bypass pipe 52 to the downstream portion 27B of the drain passage 27 via the connecting pipe 53. The junction pipe 54 is formed of a resin having high heat resistance and rigidity, or a metal having high corrosion resistance. The junction pipe 54 has a first inflow pipe portion 54A, a second inflow pipe portion 54B, and an outflow pipe portion 54C. In the junction pipe 54, the second inflow pipe portion 54B is located on the upper side, and the outflow pipe portion 54C is located on the lower side. The second inflow pipe portion 54B and the outflow pipe portion 54C are arranged coaxially, and the portion of the junction pipe 54 from the second inflow pipe portion 54B to the outflow pipe portion 54C extends vertically in a straight line. In addition, the second inflow pipe portion 54B and the connecting pipe 53 are arranged coaxially with each other, and the lower end portion of the connecting pipe 53 is connected to the upper end portion of the second inflow pipe portion 54B. In addition, the lower end of the outflow pipe section 54C is disposed approximately coaxially with the drain hole 30 that forms the upper end of the downstream section 27B of the drain passage 27, and the lower end of the outflow pipe section 54C is connected to the upper end of the drain hole 30. The first inflow pipe section 54A extends rearward while inclining upward and to the right from approximately the middle in the vertical direction of the portion of the junction pipe 54 from the second inflow pipe section 54B to the outflow pipe section 54C. The lower end of the connection hose 51 is connected to the upper end of the first inflow pipe section 54A.

[0076] In addition, the inner diameters of the inlet pipe section 41A of the branch pipe 41, the first outlet pipe section 41B of the branch pipe 41, the second outlet pipe section 41C of the branch pipe 41, the connecting hose 51, the bypass pipe 52, the connecting pipe 53, the first inlet pipe section 54A of the junction pipe 54, the second inlet pipe section 54B of the junction pipe 54, and the outlet pipe section 54C of the junction pipe 54 are all approximately equal.

[0077] As described above, in the cooling device 21 of the outboard motor 1 according to the embodiment of the present invention, the upstream portion 27A of the drain passage 27, the collection passage 32, and the bypass passage 34 are arranged so that the difference between the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 into the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is smaller than the difference between the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 into the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34. By arranging the upstream portion 27A of the drain passage 27, the collection passage 32, and the bypass passage 34 in this manner, when the filter 43 of the collector 33 is not clogged, the cooling water flowing out from the upstream portion 27A of the drain passage 27 is more likely to flow into the collection passage 32 than into the bypass passage 34. Therefore, without using a valve or the like that opens and closes the bypass passage 34 depending on whether the filter 43 of the collector 33 is clogged, most of the cooling water that flows out from the upstream portion 27A of the drain passage 27 when the filter 43 of the collector 33 is not clogged can be smoothly made to flow into the collection passage 32 and sent to the collector 33. That is, even if the upstream portion 27A of the drain passage 27 and the inlet of the bypass passage 34 are always in communication with each other, it is possible to prevent the cooling water that flows out from the upstream portion 27A of the drain passage 27 when the filter 43 of the collector 33 is not clogged from flowing into the bypass passage 34. Therefore, when the filter 43 of the collector 33 is not clogged, it is possible to prevent the amount of cooling water flowing in the collector 33 from decreasing due to the cooling water flowing into the bypass passage 34, and it is possible to prevent the cooling device 21 from decreasing in the ability to collect fine objects.

[0078] In the cooling device 21 of this embodiment, the upstream portion 27A of the drainage passage 27 and the collection passage 32 are arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 is the same as the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32, and the upstream portion 27A of the drainage passage 27 and the bypass passage 34 are arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 is different from the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34. With this configuration, when the filter 43 of the collector 33 is not clogged, most of the cooling water flowing out from the upstream portion 27A of the drainage passage 27 can be made to flow more smoothly into the collection passage 32, and the cooling device 21 can fully secure its ability to collect fine objects.

[0079] In addition, in the cooling device 21 of this embodiment, the upstream portion 27A of the drain passage 27 is arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 into the branch portion 35 is downward and vertical, the collection passage 32 is arranged so that the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is downward and vertical, and the bypass passage 34 is arranged so that the flow direction of the cooling water flowing from the branch portion 35 into the bypass passage 34 is not vertical. With this configuration, most of the cooling water flowing out from the upstream portion 27A of the drain passage 27 can flow into the collection passage 32 more smoothly when the filter 43 of the collector 33 is not clogged.

[0080] Furthermore, the collection passage 32 and the bypass passage 34 intersect at an acute angle at the branching portion 35. Therefore, when the filter 43 of the collector 33 is clogged, the cooling water flowing out from the upstream portion 27A of the drain passage 27 can be smoothly flowed into the bypass passage 34. This prevents the flow of cooling water in the drain passage 27 from deteriorating due to clogging of the filter 43 of the collector 33.

[0081] In addition, in the cooling device 21 of this embodiment, the collection passage 32, the bypass passage 34, and the downstream portion 27B of the drain passage 27 are arranged so that the difference between the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 and the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27 is smaller than the difference between the flow direction of the cooling water flowing from the collection passage 32 to the junction 36 and the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27. By arranging the downstream portion 27B of the drain passage 27, the collection passage 32, and the bypass passage 34 in this manner, the flow direction of the cooling water from the bypass passage 34 to the downstream portion 27B of the drain passage 27 can be made close to a straight line or made straight. Therefore, when the filter 43 of the collector 33 is clogged, the cooling water can be smoothly flowed from the bypass passage 34 to the downstream portion 27B of the drain passage 27, and the cooling water that has flowed through the bypass passage 34 can be prevented from flowing into the collection passage 32 from the outlet of the collection passage 32 and flowing back through the collection passage 32. In addition, by arranging the downstream portion 27B of the drain passage 27, the collection passage 32, and the bypass passage 34 as described above, when exhaust gas flows back through the downstream portion 27B of the drain passage 27 from the exhaust chamber 17 of the outboard motor 1, the flow direction of the exhaust gas from the downstream portion 27B of the drain passage 27 to the bypass passage 34 can be made close to a straight line or made straight, and the flow direction of the exhaust gas from the downstream portion 27B of the drain passage 27 to the collection passage 32 can be bent. Therefore, the exhaust gas that has flowed backward from the exhaust chamber 17 through the downstream portion 27B of the drain passage 27 can be smoothly flowed into the bypass passage 34, and the exhaust gas that has flowed backward through the downstream portion 27B of the drain passage 27 can be prevented from flowing into the collection passage 32 from the outlet of the collection passage 32 and flowing backward through the collection passage 32. In this way, the backflow of the cooling water or exhaust gas into the collection passage 32 can be prevented, so that the cooling water or exhaust gas passing from bottom to top inside the collector 33 can be prevented from being stirred up, which would otherwise occur when the cooling water or exhaust gas passes through the collector 33. Therefore, even if the inlet of the collection passage 32 and the inlet of the bypass passage 34 are always in communication with each other at the branch portion 35, the fine matter that has once accumulated in the filter 43 can be prevented from being stirred up and discharged to the outside of the outboard motor 1 through the bypass passage 34 and the downstream portion 27B of the drain passage 27.Thus, according to this embodiment, even if a valve or the like is not provided to open and close the bypass passage 34 depending on whether the filter 43 of the collector 33 is clogged or not, it is possible to prevent fine objects that have accumulated in the filter 43 from being discharged outside the outboard motor 1 due to backflow of the cooling water or exhaust gas, and therefore the fine object collection capacity of the cooling device 21 can be sufficiently ensured.

[0082] In the cooling device 21 of the present embodiment, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged so that the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 is substantially the same as the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27, and the collection passage 32 and the downstream portion 27B of the drain passage 27 are arranged so that the flow direction of the cooling water flowing from the collection passage 32 to the junction 36 is different from the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27. This configuration can improve the smoothness of the flow of the cooling water flowing from the bypass passage 34 to the downstream portion 27B of the drain passage 27 when the filter 43 of the collector 33 is clogged, and can also improve the smoothness of the flow of the exhaust gas flowing back from the downstream portion 27B of the drain passage 27 to the bypass passage 34. Therefore, the effect of suppressing the backflow of the cooling water or exhaust gas into the collection passage 32 can be improved, and the effect of suppressing the stirring up of fine objects accumulated on the filter 43 can be improved.

[0083] In the cooling device 21 of this embodiment, the bypass passage 34 is arranged so that the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 is downward and vertical, the downstream portion 27B of the drain passage 27 is arranged so that the flow direction of the cooling water flowing from the junction 36 to the downstream portion 27B of the drain passage 27 is downward and approximately vertical, and the collection passage 32 is arranged so that the flow direction of the cooling water flowing from the collection passage 32 to the junction 36 is not vertical. This configuration can further improve the smoothness of the flow of the cooling water flowing from the bypass passage 34 to the downstream portion 27B of the drain passage 27 when the filter 43 of the collector 33 is clogged. Therefore, the effect of suppressing the backflow of the cooling water to the collection passage 32 can be further improved.

[0084] Moreover, at the junction 36, the collection passage 32 and the bypass passage 34 intersect with each other at an acute angle. Therefore, when the filter 43 of the collector 33 is not clogged, the cooling water flowing out from the collector 33 can smoothly flow to the downstream portion 27B of the drain passage 27 via the collection passage 32. When the filter 43 of the collector 33 is clogged, the cooling water that has flowed through the bypass passage 34 can be prevented from flowing into the collection passage 32 from the outlet of the collection passage 32.

[0085] In the above embodiment, the upstream portion 27A of the drainage passage 27 and the collection passage 32 are arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 is the same as the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32. The flow direction of the cooling water flowing from the upstream portion 27A of the drainage passage 27 into the branch portion 35 and the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 do not have to be completely the same as each other, and may be slightly different within a range that ensures the smooth flow of cooling water from the upstream portion 27A of the drainage passage 27 to the collection passage 32 when the filter 43 of the collector 33 is not clogged.

[0086] In the above embodiment, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged so that the flow direction of the cooling water flowing from the bypass passage 34 to the junction portion 36 and the flow direction of the cooling water flowing from the junction portion 36 to the downstream portion 27B of the drain passage 27 are substantially the same. The flow direction of the cooling water flowing from the bypass passage 34 to the junction portion 36 and the flow direction of the cooling water flowing from the junction portion 36 to the downstream portion 27B of the drain passage 27 are not completely the same but slightly different from each other because the extension direction of the upper end portion (drain hole 30) of the downstream portion 27B of the drain passage 27 is slightly inclined with respect to the vertical. However, if the difference is to this extent, the smooth flow of the cooling water from the bypass passage 34 to the downstream portion 27B of the drain passage 27 and the smooth flow of the exhaust gas from the downstream portion 27B of the drain passage 27 to the bypass passage 34 can be ensured, so that this degree of difference can be regarded as being the same. However, the extension direction of the upper end (drainage hole 30) of the downstream portion 27B of the drainage passage 27 may be vertical, and the flow direction of the cooling water flowing from the bypass passage 34 to the junction 36 may be completely identical to the flow direction of the cooling water flowing from the junction 36 into the downstream portion 27B of the drainage passage 27.

[0087] In the above embodiment, the upstream portion 27A of the drain passage 27 is arranged so that the flow direction of the cooling water flowing from the upstream portion 27A of the drain passage 27 to the branch portion 35 is downward and vertical, and specifically, the lower end of the upstream portion 27A of the drain passage 27 extends vertically. The collection passage 32 is arranged so that the flow direction of the cooling water flowing from the branch portion 35 to the collection passage 32 is downward and vertical, and specifically, the upper end of the collection passage 32 extends vertically. The bypass passage 34 is arranged so that the flow direction of the cooling water flowing from the bypass passage 34 to the junction portion 36 is downward and vertical, and specifically, the lower end of the bypass passage 34 extends vertically. These flow directions and extension directions do not have to be completely vertical, and may be slightly inclined relative to the vertical.

[0088] In addition, in the above embodiment, the fine object collecting device 31 is disposed on the left side of the rear of the engine 2, but the fine object collecting device 31 may be disposed at another position around the engine 2, such as on the right side of the rear of the engine 2.

[0089] The power source of the outboard motor 1 is not limited to an engine, but may be an electric motor. The cooling device of the present invention is not limited to an outboard motor, but may also be provided in other types of marine propulsion motors, such as inboard-outboard motors or inboard motors.

[0090] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or concept of the invention that can be read from the claims and the entire specification, and a cooling device for a marine propulsion unit that includes such modifications is also included in the technical concept of the present invention. [Explanation of symbols]

[0091] 1. Outboard motor (marine propulsion unit) 2 Engine (power source) 21 Cooling device 27 Drain passage 27A Upstream section 27B Downstream 32 Collection passage 33 Collector 34 Bypass Passage 35 Branch 36 Junction

Claims

1. A cooling device for a marine propulsion device that is provided to a marine propulsion device, takes in water outside the marine propulsion device into the marine propulsion device, flows the taken-in water as cooling water around or inside a power source of the marine propulsion device to cool the power source, and discharges the cooling water that has flowed around or inside the power source to the outside of the marine propulsion device, a drain passage for discharging the cooling water after flowing around or inside the power source to the outside of the marine propulsion device; a collection passage interposed between an upstream portion and a downstream portion of the drainage passage and connecting the upstream portion and the downstream portion of the drainage passage; a collector provided in the collection passage and configured to collect fine objects contained in the cooling water flowing through the collection passage from the upstream portion of the drain passage toward the downstream portion of the drain passage; a bypass passage connected in parallel with the collection passage between the upstream and downstream portions of the drainage passage; a branching portion where an upstream portion of the drainage passage branches into the collection passage and the bypass passage; a junction portion where the collection passage and the bypass passage join a downstream portion of the drainage passage, A cooling device for a marine propulsion unit, characterized in that the upstream portion of the drainage passage, the collection passage and the bypass passage are arranged so that the difference between the flow direction of cooling water flowing from the upstream portion of the drainage passage into the branch portion and the flow direction of cooling water flowing from the branch portion into the collection passage is smaller than the difference between the flow direction of cooling water flowing from the upstream portion of the drainage passage into the branch portion and the flow direction of cooling water flowing from the branch portion into the bypass passage.

2. the upstream portion of the drainage passage and the collection passage are arranged such that a flow direction of the cooling water flowing from the upstream portion of the drainage passage into the branching portion and a flow direction of the cooling water flowing from the branching portion into the collection passage are the same as each other, A cooling device for a marine propulsion unit as described in claim 1, characterized in that the upstream portion of the drainage passage and the bypass passage are arranged so that the flow direction of the cooling water flowing from the upstream portion of the drainage passage into the branching portion and the flow direction of the cooling water flowing from the branching portion into the bypass passage are different from each other.

3. the upstream portion of the drain passage is disposed so that the flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion is downward and vertical; the collection passage is disposed such that the flow direction of the cooling water flowing from the branch portion into the collection passage is downward and vertical, 3. The cooling device for a marine propulsion device according to claim 1, wherein the bypass passage is disposed so that a flow direction of the cooling water flowing from the branching portion into the bypass passage is not vertical.

4. 4. The cooling device for a marine propulsion device according to claim 1, wherein the collection passage and the bypass passage intersect at an acute angle with each other at the branching portion.

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