Ship propulsion engine cooling device

Abstract

To provide a ship propulsion engine cooling device capable of sufficiently ensuring micro object collection ability even without using a valve to open / close a bypass passage.SOLUTION: In an outboard engine cooling device, an upstream part 27A of a drain passage, a downstream part 27B of the drain passage, a collection passage 32, and a bypass passage 34 are arranged so that the difference between the flow direction of a cooling water flowing into a branch part 35 from the upstream part 27A and the flow direction of the cooling water flowing into the collection passage 32 from the branch part 35 becomes smaller than the difference between the flow direction of the cooling water flowing into the branch part 35 and the flow direction of the cooling water flowing into the bypass passage 34. The upstream part of the drain passage, the downstream part 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 into a confluent part 36 from the bypass passage 34 and the flow direction of the cooling water flowing into the downstream part 27B from the confluent part 36 becomes smaller than the difference between the flow direction of the cooling water flowing into the confluent part 36 from the collection passage 32 and the flow direction of the cooling water flowing into the downstream 27B from the confluent part 36.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a cooling device for a marine propulsion engine having a function of collecting fine objects diffused in water such as seawater and lake water.

Background Art

[0002] In recent years, pollution of the sea, lakes, rivers, etc. caused by the diffusion of fine garbage such as microplastics in water such as seawater, lake water, and river water has become a problem. Also, it is known that the sea, lakes, rivers, etc. are polluted by the diffusion of residues of feed used in aquaculture, etc. in water such as seawater, lake water, and river water. In order to suppress such pollution, it is desired to collect and recover fine garbage such as microplastics, feed residues, etc. (hereinafter, these are referred to as "fine objects").

[0003] Patent Document 1 below 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 water such as seawater or lake water into the outboard motor, and supplies the taken-in water as cooling water to a water jacket provided in the engine of the outboard motor. The cooling water supplied to the water jacket circulates in the water jacket, and thereby the engine is cooled. Further, the cooling water after circulating in the water jacket flows in a drain pipe and passes through a filtering device provided in the middle of the drain pipe, and then is discharged outside the outboard motor. When the cooling water passes through the filtering device, fine objects in the cooling water are captured by the filtering device and removed from the cooling water. Thus, according to the cooling device, seawater or lake water, etc. can be taken into the outboard motor, and fine objects contained in the taken-in seawater or lake water, etc. can be collected by the filtering device.

[0004] Also, in the cooling device described in Patent Document 1, a bypass passage for flowing cooling water around the filtration device is connected to the drain pipe provided with the filtration device when the filtration device becomes clogged. Further, in this cooling device, a relief valve is provided at the connection portion between the upstream end of the bypass passage and the drain pipe. The relief valve closes when the filtration device is not clogged, guides the cooling water flowing through the drain pipe to the filtration device, and opens when the filtration device becomes clogged, guiding the cooling water flowing through the drain pipe to the bypass passage around the filtration device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Figs. 8(A) and (B) show a configuration equivalent to the drainage-side configuration of the conventional cooling device described in Patent Document 1 above. In Figs. 8(A) and (B), 133 is a drainage passage. The drainage passage 133 corresponds to the drain pipe in the cooling device described in Patent Document 1 above. 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, as shown in Fig. 8(A), the relief valve 144 closes. At this time, the cooling water flows through the drainage passage 133 so as to pass through the filtration device 135 as indicated by the arrow V in Fig. 8(A). On the other hand, when the filtration device 135 becomes clogged, as shown in Fig. 8(B), the relief valve 144 opens. At this time, the cooling water flows through the bypass passage 145 as indicated by the arrow W in Fig. 8(B).

[0007] By the way, the inventor of the present application is considering removing the relief valve 144 from the configuration on the drainage side of the cooling device as shown in FIGS. 8(A) and (B), for example. By removing the relief valve 144, the number of parts can be reduced, the manufacturing cost of the cooling device can be lowered, and moreover, problems such as failures of the relief valve 144 and the burden of maintenance of the relief valve 144 can be eliminated. However, removing the relief valve 144 from the configuration on the drainage side of the cooling device causes the following problems.

[0008] FIG. 9(A) shows the configuration with the relief valve 144 removed from the drainage side of the cooling device shown in FIGS. 8(A) and (B). 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 indicated 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. This phenomenon is such that, as indicated by the dashed-dotted line in FIG. 9(A), at the branch portion where the bypass passage 145 branches from the drainage passage 133, a linear flow path extending from the drainage passage 133 toward the bypass passage 145 is formed. Therefore, this is likely to occur when the flow direction of the cooling water flowing into the branch portion from the drainage passage 133 (arrow X1) and the flow direction of the cooling water flowing into the bypass passage 145 from the branch portion (arrow X2) are the same. Thus, even when the filtration device 135 is not clogged and the cooling water flows into the bypass passage 145, the amount of cooling water flowing through the filtration device 135 decreases. As a result, the ability of the cooling device to collect fine objects decreases.

[0009] Also, in the case where the relief valve 144 is removed from the drainage side configuration of the cooling device shown in FIGS. 8(A) and (B), there is a concern that the fine objects accumulated in the filtration device 135 may be lifted up when the cooling water flowing through the bypass passage 145 flows out from the outlet of the bypass passage 145 and then reversely flows through the drainage passage 133, and the lifted fine objects may sequentially flow through the bypass passage 145 and the drainage passage 133 together with the cooling water and be discharged outside the outboard motor.

[0010] FIG. 9(B) shows, as in FIG. 9(A), the configuration of the drainage side of the cooling device shown in FIGS. 8(A) and (B) with the relief valve 144 removed. The cooling water flowing 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 the arrows Y1 and Y2 in FIG. 9(B). However, when the amount of cooling water flowing through the bypass passage 145 is large, when the cooling water flowing through the bypass passage 145 flows out from the outlet of the bypass passage 145, its flow is disturbed, and the cooling water may flow backward upward through the drainage passage 133 as indicated by the arrow Y3 in FIG. 9(B). This backflow occurs because, as indicated by the two-dot chain line in FIG. 9(B), the flow path from the bypass passage 145 to the drainage passage 133 is bent at the confluence where the bypass passage 145 merges with the drainage passage 133. Therefore, it is likely to occur when the flow direction of the cooling water flowing into the confluence from the bypass passage 145 (arrow Y1) is different from the flow direction of the cooling water flowing downward through the drainage passage 133 from the confluence (arrow Y2). When the cooling water flows backward through the drainage passage 133, the backward-flowing cooling water may flow upward from the bottom inside the filtering device 135, and there is a possibility that the fine objects accumulated inside the filtering device 135 may be lifted up by this cooling water. In the configuration where the relief valve 144 is removed, since the inlet of the bypass passage 145 is always in communication with the drainage passage 133, the lifted fine objects may enter the bypass passage 145 from the inlet of the bypass passage 145 together with the cooling water, flow sequentially downward through the bypass passage 145 and the drainage passage 133, and be discharged outside the outboard motor. Because of such a backflow of the cooling water, there is a possibility that the fine objects once accumulated in the filtering device 135 may be discharged outside the outboard motor. Therefore, such a backflow of the cooling water leads to a decrease in the fine object collection ability of the cooling device.

[0011] Further, in the case where the relief valve 144 is removed from the configuration on the drainage side of the cooling device shown in FIGS. 8(A) and (B), when the power source of the outboard motor is an engine, the exhaust gas of the engine flows backward through the drainage passage 133, so that the fine objects accumulated in the filtering device 135 are lifted up, and there is a concern that the lifted fine objects will sequentially flow through the bypass passage 145 and the drainage passage 133 together with the cooling water and be discharged outside the outboard motor.

[0012] That is, in many outboard motors with an engine as the power source, an exhaust chamber is provided at the rear of the lower part of the outboard motor, and the exhaust gas discharged from the engine is configured to be sent to the exhaust chamber through the exhaust passage. When such an outboard motor has a water-cooled cooling device, the cooling device is often configured such that the cooling water flowing through the drainage passage is discharged into the exhaust chamber. When the 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 into the exhaust chamber may flow from the exhaust chamber into the drainage passage and flow backward in the drainage passage.

[0013] FIG. 9(C) shows the configuration on the drainage side of the cooling device shown in FIGS. 8(A) and (B) with the relief valve 144 removed, similar to FIGS. 9(A) and 9(B). As indicated by the arrow Z in FIG. 9(C), exhaust gas flowing backward from the exhaust chamber into the drainage passage 133 may reach the filtration device 135 and flow upward from the bottom within the filtration device 135. The phenomenon in which the exhaust gas flowing backward through the drainage passage 133 reaches the filtration device 135 occurs easily when the flow path from below the filtration device 135 to the filtration device 135 in the drainage passage 133 is linear, as indicated by the dashed-dotted line in FIG. 9(C). When the exhaust gas flows upward from the bottom within the filtration device 135, the fine objects accumulated within the filtration device 135 may be lifted up by this exhaust gas, and the lifted fine objects may sequentially flow downward along with the cooling water through the bypass passage 145 and the drainage passage 133 and be discharged outside the outboard motor. Therefore, such a reverse flow of exhaust gas also leads to a decrease in the fine object collection ability of the cooling device.

[0014] The present invention has been made in view 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 sufficiently ensure the fine object collection ability even when not using a valve or the like that opens and closes a bypass passage according to the presence or absence of clogging of a collector (filtration device).

Means for Solving the Problems

[0015] In order to solve the above problems, the present invention provides a cooling device for a marine propulsion machine, which is provided in the marine propulsion machine, takes in water outside the marine propulsion machine into the marine propulsion machine, and cools the power source of the marine propulsion machine by flowing the taken-in water as cooling water around or inside the power source, and discharges the cooling water after flowing around or inside the power source outside the marine propulsion machine. The cooling device includes a drainage passage for discharging the cooling water after flowing around or inside the power source outside the marine propulsion machine, a collection passage interposed between the upstream portion and the downstream portion of the drainage passage and connecting the upstream portion and the downstream portion of the drainage passage, a collector provided in the middle of the collection passage for collecting fine objects contained in the cooling water flowing from the upstream portion of the drainage passage toward the downstream portion of the drainage passage through the collection passage, a bypass passage connected in parallel with the collection passage between the upstream portion and the downstream portion of the drainage passage, a branch portion where the upstream portion of the drainage passage branches into the collection passage and the bypass passage, and a confluence portion where the collection passage and the bypass passage merge into the downstream portion of the drainage passage. The upstream portion of the drainage passage, the collection passage, and the bypass passage are arranged such that the difference between the flow direction of the cooling water flowing from the upstream portion of the drainage 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 drainage passage into the branch portion and the flow direction of the cooling water flowing from the branch portion into the bypass passage. The downstream portion of the drainage passage, the collection passage, and the bypass passage are arranged such that the difference between the flow direction of the cooling water flowing from the bypass passage into the confluence portion and the flow direction of the cooling water flowing from the confluence portion into the downstream portion of the drainage passage is smaller than the difference between the flow direction of the cooling water flowing from the collection passage into the confluence portion and the flow direction of the cooling water flowing from the confluence portion into the downstream portion of the drainage passage.

Effect of the Invention

[0016] According to the present invention, even when a valve or the like for opening and closing the bypass passage is not used according to the presence or absence of clogging of the collector, the collection ability of fine objects can be sufficiently ensured.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0018] The cooling device for a marine propulsion engine according to an embodiment of the present invention is provided in the marine propulsion engine, takes in water outside the marine propulsion engine into the marine propulsion engine, and cools the power source by flowing the taken-in water as cooling water around or inside the power source of the marine propulsion engine, and then discharges the cooling water that has flowed around or inside the power source to the outside of the marine propulsion engine. The cooling device includes a drainage passage for discharging the cooling water that has flowed around or inside the power source to the outside of the marine propulsion engine, a collection passage interposed between the upstream portion and the downstream portion of the drainage passage and connecting the upstream portion and the downstream portion of the drainage passage, a collector provided in the middle of the collection passage for collecting fine objects contained in the cooling water flowing from the upstream portion of the drainage passage toward the downstream portion of the drainage passage through the collection passage, a bypass passage connected in parallel with the collection passage between the upstream portion and the downstream portion of the drainage passage, a branch portion where the upstream portion of the drainage passage branches into the collection passage and the bypass passage, and a confluence portion where the collection passage and the bypass passage merge into the downstream portion of the drainage passage.

[0019] Further, in the cooling device of the present embodiment, the upstream portion of the drainage passage, the collection passage, and the bypass passage are arranged such that the difference between the flow direction of the cooling water flowing from the upstream portion of the drainage 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 drainage passage into the branch portion and the flow direction of the cooling water flowing from the branch portion into the bypass passage.

[0020] With the upstream part of the drainage passage, the collection passage, and the bypass passage arranged in this way, 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 according to the presence or absence of clogging of the collector, most of the cooling water flowing out from the upstream part of the drainage passage when the collector is not clogged can smoothly flow into the collection passage and be sent to the collector. That is, even when the upstream part of the drainage passage and the inlet of the bypass passage are always in communication, it is possible to suppress 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 suppress a decrease in the amount of cooling water flowing through the collector due to the cooling water flowing into the bypass passage, and it is possible to suppress a decrease in the ability of the cooling device to collect fine objects.

[0021] Also, in the cooling device of the present embodiment, the downstream part of the drainage passage, the collection passage, and the bypass passage are arranged such that the difference between the flow direction of the cooling water flowing into the confluence part from the bypass passage and the flow direction of the cooling water flowing into the downstream part of the drainage passage from the confluence part is smaller than the difference between the flow direction of the cooling water flowing into the confluence part from the collection passage and the flow direction of the cooling water flowing into the downstream part of the drainage passage from the confluence part.

[0022] By arranging the downstream part of the drainage passage, the collection passage, and the bypass passage in this way, the flow direction of the cooling water from the bypass passage to the downstream part of the drainage passage can be made closer to a straight line or a straight line. Therefore, when the collector is clogged, the cooling water can flow smoothly from the bypass passage to the downstream part of the drainage passage, and it is possible to suppress the cooling water flowing through the bypass passage from flowing backward through the collection passage. Further, by arranging the downstream part of the drainage passage, the collection passage, and the bypass passage as described above, when the exhaust gas flows backward from the exhaust chamber of the marine propulsion engine to the downstream part of the drainage passage, the flow direction of the exhaust gas from the downstream part of the drainage passage to the bypass passage can be made closer to a straight line or a straight line, and the flow direction of the exhaust gas from the downstream part of the drainage passage to the collection passage can be bent. Therefore, the exhaust gas flowing backward from the exhaust chamber of the marine propulsion engine to the downstream part of the drainage passage can flow smoothly into the bypass passage, and it is possible to suppress the exhaust gas flowing backward through the downstream part of the drainage passage from flowing backward through the collection passage.

[0023] In this way, by suppressing the backflow of the cooling water or the exhaust gas into the collection passage, it is possible to suppress the fine objects accumulated in the collector from being lifted up when the cooling water or the exhaust gas passes through the collector from bottom to top. Therefore, even when the inlet of the collection passage and the inlet of the bypass passage are constantly connected at the branch portion, it is possible to suppress the fine objects once accumulated in the collector from being lifted up and discharged outside the marine propulsion engine through the bypass passage and the downstream part of the drainage passage. Thus, according to the present embodiment, even when a valve or the like for opening and closing the bypass passage is not provided according to the presence or absence of clogging of the collector, it is possible to suppress the fine objects once accumulated in the collector from being discharged outside the marine propulsion engine due to the backflow of the cooling water or the exhaust gas. Therefore, the collection ability of the fine objects of the cooling device can be sufficiently ensured.

Example

[0024] Hereinafter, an embodiment of the cooling device for a marine propulsion unit of the present invention will be described with reference to FIGS. 1 to 7. In the embodiment, when referring to the directions of front (Fd), rear (Bd), upper (Ud), lower (Dd), left (Ld), and right (Rd), follow the arrows drawn at the lower left in FIGS. 1 to 7.

[0025] (Outboard motor) FIG. 1 shows a state of an outboard motor 1, which is one form of a marine propulsion unit, as viewed from the left side. As shown in FIG. 1, the outboard motor 1 includes an engine 2 as a power source, a drive shaft 3 that rotates receiving the power of the engine 2, a propeller 4 that generates a propulsion force for the ship, 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 for switching the direction of rotation transmitted from the drive shaft 3 to the propeller shaft 5. The engine 2 is disposed at the upper part of the outboard motor 1. The gear mechanism 6, the propeller shaft 5, and the propeller 4 are disposed at the lower part of the outboard motor 1. The drive shaft 3 extends vertically between the engine 2 and the gear mechanism 6.

[0026] Also, the lower part of the engine 2 is covered by an engine bottom cover 7, and the middle and upper parts in the vertical direction 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 parts from the middle part to the upper part in the vertical direction of the engine 2 can be exposed. Further, the upper part of the drive shaft 3 is covered by an upper case 9, and the middle part in the vertical direction of the drive shaft 3 is covered by a middle case 10. Also, the lower part of the drive shaft 3, the front part of the gear mechanism 6, and the front part of the propeller shaft 5 are covered by a lower case 11.

[0027] Figure 2 shows the state of the engine 2 as viewed from the left side. Figure 3 shows the state of the engine 2 as viewed from the rear side. The engine 2 is, for example, a four-cycle four-cylinder gasoline engine, and the cooling method of the engine 2 is a water-cooled type. The engine 2 is arranged such that the extending direction of the crankshaft is in the vertical direction. As shown in Figure 2, in the engine 2, a crankcase 12 is arranged at the front part, a cylinder block 13 is arranged behind the crankcase 12, and a cylinder head 14 is arranged behind the cylinder block 13. Further, the rear part of the cylinder head 14 is covered by a cylinder head cover 15.

[0028] Also, as shown in Figure 1, the outboard motor 1 is provided with an exhaust passage 16 for discharging the exhaust gas discharged from the engine 2 to the outside of the outboard motor 1. The upper end side of the exhaust passage 16 is connected to an exhaust port provided in the cylinder head 14 of the engine 2, and the lower end side of the exhaust passage 16 is connected to an exhaust chamber 17 provided at the rear part of the lower part in the outboard motor 1. In the outboard motor 1 of this embodiment, the exhaust chamber 17 is provided in a portion from the rear part in the middle case 10 to the rear part in the lower case 11. The exhaust gas discharged from the exhaust port of the engine 2 is sent to the exhaust chamber 17 through the exhaust passage 16, and then is discharged to the outside of the outboard motor 1 through, for example, an exhaust port provided in the shaft part of the propeller 4. Note that in Figures 2 and 3, the illustration of the exhaust port of the engine 2 and the exhaust passage 16 is omitted.

[0029] (Cooling Device) The outboard motor 1 is provided with a cooling device 21 for cooling the engine 2 and other heat-generating parts in the outboard motor 1 by using the water around the outboard motor 1, such as seawater, lake water, or river water, as cooling water. Figure 4 shows the configuration of the cooling device 21.

[0030] As shown in Figure 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 drainage passage 27, a thermostat 28, a pressure valve 29, and a fine object collection device 31.

[0031] The water intake port 22 is an opening for taking in the water around the outboard motor 1 into the outboard motor 1, and is provided in a portion of the outboard motor 1 that sinks below the water surface, specifically, a part of the lower case 11 (see FIG. 1). Further, the water intake port 22 is provided with a strainer for preventing an object larger than a fine object such as a stone or seaweed from entering the outboard motor 1 together with seawater, lake water, or river water, or a cover having a large number of small holes.

[0032] The water intake passage 23 is a passage for sucking the 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 the water taken into the outboard motor 1 from the water intake port 22 and discharges the sucked water as cooling water, and is provided, for example, inside the lower case 11 or the middle case 10. Further, the water pump 24 operates by utilizing the rotation of the drive shaft 3.

[0034] The water supply passage 25 is a passage for supplying the cooling water discharged from the water pump 24 to the water jacket 26, and is formed by, for example, a hose or a 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 flowing the cooling water supplied through the water supply passage 25 around or inside the engine 2, and is provided around or inside the engine 2.

[0036] The drainage 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 collection device 31 is interposed in the middle of the drainage passage 27. Therefore, the drainage passage 27 is divided into an upstream portion 27A that is a portion upstream of the fine object collection device 31 and a downstream portion 27B that is a portion downstream of the fine object collection device 31.

[0037] As shown in FIGS. 2 and 3, the upstream portion 27A of the drain passage 27 is disposed in a region extending from above the cylinder head 14 to the left of the upper part of the cylinder head cover 15. The upstream portion 27A of the drain passage 27 is formed of a pipe made of a resin having high heat resistance and rigidity or a metal having high corrosion resistance, or a rubber hose having high heat resistance and rigidity, etc. The upper end portion of the upstream portion 27A of the drain passage 27 is connected to the outlet 26A of the water jacket 26 disposed on the upper part of the cylinder head 14. Further, the upstream portion 27A of the drain passage 27 extends leftward from the outlet 26A of the water jacket 26 and then bends, and then extends rearward while inclining downward to the left of the upper rear part of the engine 2, and then bends, and then extends horizontally rearward to the left of the upper rear part of the engine 2, and then bends, and then extends vertically downward to the left of the upper rear part of the engine 2. And the mouth at the lower end of the upstream portion 27A of the drain passage 27 faces downward. Further, at the lower end portion of the upstream portion 27A of the drain passage 27, the upper end portions (specifically, the upper end portion of the inflow pipe portion 41A of the branch pipe 41) of the collection passage 32 and the bypass passage 34 of the fine object collection device 31 are connected.

[0038] Also, the downstream portion 27B of the drain passage 27 is disposed in a region from the lower left part of the rear portion of the engine 2 to the exhaust chamber 17. The upper end portion of the downstream portion 27B of the drain passage 27 is formed by a drain hole 30 formed in the lower left part of the rear portion of the housing of the engine 2. The drain hole 30 extends downward although it is slightly inclined to the right, and the mouth at the upper end of the drain hole 30 faces upward. Further, at the upper end portion of the drain hole 30, the lower end portions (specifically, the lower end portion of the outflow pipe portion 54C of the confluence pipe 54) of the collection passage 32 and the bypass passage 34 are connected. Also, 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. Further, the lower end portion 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 restricts the flow of cooling water to warm up the engine 2 or prevent the engine 2 from being supercooled, and is provided, for example, near the outlet 26A of the water jacket 26. The thermostat 28 opens the valve when the temperature of the cooling water flowing in the water jacket 26 becomes equal to or higher than a predetermined reference temperature, and closes the valve when the temperature of the cooling water becomes lower than the reference temperature.

[0040] The pressure valve 29 is a valve for reducing the water pressure in the water supply passage 25 or the water jacket 26 by allowing the cooling water discharged from the water pump 24 to escape to the exhaust chamber 17 side 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 the valve 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 captures fine objects contained in seawater, lake water, river water, etc., which are 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 operates, the thermostat 28 opens, and the pressure valve 29 closes, the water around the outboard motor 1 is taken into the outboard motor 1 from the water intake 22. The water then sequentially flows through the water intake passage 23 and the water supply passage 25 and is sent as cooling water to the water jacket 26. The cooling water sent to the water jacket 26 flows through the water jacket 26, thereby cooling the engine 2. The cooling water that has flowed through the water jacket 26 flows into the upstream portion 27A of the drain passage 27 from the outlet 26A of the water jacket 26, flows through the upstream portion 27A of the drain passage 27, then flows through the fine object collection 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 through, for example, a discharge port provided in the shaft portion of the propeller 4. On the other hand, when the water pump 24 operates, the thermostat 28 closes, and the pressure valve 29 opens, the water taken into the outboard motor 1 from the water intake 22 sequentially flows 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 through the open pressure valve 29 and is 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.

[0043] (Fine Object Collection Device) As described above, the fine object collection device 31 is a device that collects fine objects contained in seawater, lake water, river water, etc., which are taken into the outboard motor 1 from outside the outboard motor 1 and used as cooling water for cooling the engine 2. As shown in FIGS. 2 and 3, the fine object collection device 31 is disposed on the left side of the rear portion of the engine 2. Further, the fine object collection device 31 is disposed within the engine top cover 8.

[0044] The fine objects are, for example, fine dust such as microplastics, or residues of feed used in aquaculture. The size of the fine objects is, for example, about 0.1 mm or more and about 5 mm or less. Since the fine objects are of such a size, they are not removed by the strainer provided at the water intake 22 or the cover having a large number of small holes. 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 pass through the intake passage 23, the water supply passage 25, the water jacket 26, and the upstream portion 27A of the drainage passage 27 and flow into the fine object collection device 31.

[0045] Figure 5 shows the basic configuration of the fine object collection device 31. As shown in Figure 5, the fine object collection device 31 includes a collection passage 32, a collector 33, a bypass passage 34, a branch portion 35, and a confluence portion 36.

[0046] The collection passage 32 is interposed between the upstream portion 27A and the downstream portion 27B of the drainage passage 27 and is a passage connecting the upstream portion 27A and the downstream portion 27B of the drainage passage 27. The collection passage 32 allows 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 in the middle of the collection passage 32 and is a device that collects fine objects contained in the cooling water flowing from the upstream portion 27A of the drainage passage 27 to the downstream portion 27B of the drainage passage 27 through the collection passage 32. As will be described later, the collector 33 captures the fine objects in the cooling water by passing the cooling water flowing through the collection passage 32 through the filter 43 and removes the fine objects from the cooling water.

[0048] The bypass passage 34 is a passage connected in parallel with the collection passage 32 between the upstream portion 27A and the downstream portion 27B of the drainage passage 27. The bypass passage 34 allows 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 without passing through the collector 33 when the filter 43 of the collector 33 is clogged, etc.

[0049] The branch portion 35 is the portion where the upstream portion 27A of the drainage passage 27 branches into the collection passage 32 and the bypass passage 34. The confluence portion 36 is the 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 the collection passage and the bypass passage at the branch portion, etc.) In FIG. 5, the upstream portion 27A of the drainage passage 27, the collection passage 32, and the bypass passage 34 are arranged such 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 such that 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 are the same as each other. In contrast, the upstream portion 27A of the drainage passage 27 and the bypass passage 34 are arranged such that 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 are different from each other.

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

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

[0054] Also, at the branch portion 35, the collection passage 32 and the bypass passage 34 intersect each other at an acute angle. The angle P formed by the upper end of the collection passage 32 and the upper end of the bypass passage 34 is, for example, about 20 degrees or more 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 at a right angle at the branch portion 35. In this case, P is 90 degrees.

[0055] (Arrangement of collection passage, bypass passage, etc. at the confluence portion) The collection passage 32, the bypass passage 34, and the downstream portion 27B of the drainage passage 27 are arranged such that the difference between the flow direction of the cooling water flowing into the confluence portion 36 from the bypass passage 34 and the flow direction of the cooling water flowing into the downstream portion 27B of the drainage passage 27 from the confluence portion 36 is smaller than the difference between the flow direction of the cooling water flowing into the confluence portion 36 from the collection passage 32 and the flow direction of the cooling water flowing into the downstream portion 27B of the drainage passage 27 from the confluence portion 36.

[0056] Specifically, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 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 such that the flow direction of the cooling water flowing from the collection passage 32 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are different from each other.

[0057] Regarding the relationship between the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27, the reason for expressing it as "substantially the same" is that, as shown in FIG. 3, in a state where 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 hardly reduces the effect of the cooling device 21 of this embodiment, which can suppress the backflow of the cooling water flowing through the bypass passage 34 into the collection passage 32, and hardly reduces the effect of the cooling device 21 of this embodiment, which can suppress the exhaust gas flowing 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, as shown by arrow E, the bypass passage 34 is arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 is downward and vertical. Further, as shown by arrow F, the downstream portion 27B of the drain passage 27 is arranged such that the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 is downward and substantially vertical. In contrast, as shown by arrow D, the collection passage 32 is arranged such that the flow direction of the cooling water flowing from the collection passage 32 into the confluence portion 36 is not vertical.

[0059] In this embodiment, the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drainage passage 27 are connected to each other at the confluence portion 36. The lower end of the bypass passage 34 extends vertically, the upper end of the downstream portion 27B of the drainage passage 27 extends substantially vertically, and the lower end of the bypass passage 34 and the upper end of the downstream portion 27B of the drainage passage 27 are arranged substantially coaxially with each other. Thereby, a substantially linear flow path extending substantially vertically is formed from the lower end of the bypass passage 34 to the upper end of the downstream portion 27B of the drainage passage 27. On the other hand, the lower end of the collection passage 32 connected to the upper end of the downstream portion 27B of the drainage passage 27 at the confluence portion 36 is inclined with respect to the vertical. Thereby, a bent flow path is formed from the lower end of the collection passage 32 to the upper end of the downstream portion 27B of the drainage passage 27.

[0060] Also, at the confluence portion 36, the collection passage 32 and the bypass passage 34 intersect each other at an acute angle. The angle Q formed by the lower end of the collection passage 32 and the lower end of the bypass passage 34 is, for example, about 20 degrees or more and less than 90 degrees. Note that the lower end of the collection passage 32 may be extended horizontally, and at the confluence portion 36, the collection passage 32 and the bypass passage 34 may intersect at a right angle. In this case, Q is 90 degrees.

[0061] The collection passage 32 extends vertically and downward from the branch portion 35, then bends, and then extends downward while being inclined with respect to the vertical, reaching the confluence portion 36. Also, the collector 33 is provided in the middle of the portion of the collection passage 32 that extends vertically. The bypass passage 34 extends downward while being inclined with respect to the vertical from the branch portion 35, then bends, and then extends vertically and downward, reaching the confluence portion 36.

[0062] (Flow of cooling water in the fine object collection device) In FIG. 5, the lower end of the upstream portion 27A of the drainage passage 27 and the upper end of the collection passage 32 both extend vertically. Further, the lower end of the upstream portion 27A of the drainage passage 27 and the upper end of the collection passage 32 are coaxially arranged with each other, and a straight flow path extending vertically is formed from the lower end of the upstream portion 27A of the drainage 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 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 are both downward and vertical, and the same as each other, as indicated by arrows A and B. On the other hand, 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 drainage 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 into the bypass passage 34 is not vertical, as indicated by arrow C. As a result, 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 are different from each other. 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 drainage passage 27 into the branch portion 35 flows into the collection passage 32. The cooling water flowing 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 drainage passage 27 through the lower part of the collection passage 32 and the confluence portion 36 in sequence. Thus, according to this embodiment, without using a valve or the like that opens and closes the bypass passage 34 according to the presence or absence of clogging of the filter 43 of the collector 33, 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.

[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 stagnates 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 has flowed into the branch portion 35 from the upstream portion 27A of the drain passage 27 flows into the bypass passage 34, and sequentially passes through the bypass passage 34 and the confluence portion 36 and flows into the downstream portion 27B of the drain passage 27. Here, the lower end portion of the bypass passage 34 extends vertically, the upper end portion of the downstream portion 27B of the drain passage 27 extends substantially vertically, and the lower end portion of the bypass passage 34 and the upper end portion of the downstream portion 27B of the drain passage 27 are arranged substantially coaxially with each other. Thereby, a substantially linear flow path that extends substantially vertically is formed from the lower end portion of the bypass passage 34 to the upper end portion of the downstream portion 27B of the drain passage 27. Therefore, the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are both downward and substantially vertical, and substantially the same as each other, as indicated by the arrows E and F. Therefore, the cooling water smoothly flows downward substantially linearly from the bypass passage 34 to the downstream portion 27B of the drain passage 27. Therefore, according to the present embodiment, it is possible to suppress the flow of the cooling water flowing from the bypass passage 34 into the confluence portion 36 from being disturbed and flowing backward from the lower end portion of the bypass passage 34 to the collection passage 32. Therefore, it is possible to suppress the fine objects accumulated on the filter 43 of the collector 33 from being lifted up when the cooling water passes through the collector 33 from bottom to top.

[0064] (Flow of exhaust gas flowing backward from the exhaust chamber) As can be seen from FIGS. 1 and 4, an exhaust passage 16 and a downstream portion 27B of a drain passage 27 are connected to an 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 into the exhaust chamber 17 may flow from the exhaust chamber 17 into the downstream portion 27B of the drain passage 27 and flow backward through the downstream portion 27B of the drain passage 27. In the outboard motor 1, the lower end portion of the bypass passage 34 and the upper end portion of the downstream portion 27B of the drain passage 27 both extend substantially vertically. Further, the lower end portion of the bypass passage 34 and the upper end portion of the downstream portion 27B of the drain passage 27 are arranged substantially coaxially with each other, and a substantially linear flow path extending substantially vertically is formed from the lower end portion of the bypass passage 34 to the upper end portion of the downstream portion 27B of the drain passage 27. Therefore, most of the exhaust gas flowing backward through the downstream portion 27B of the drain passage 27 flows substantially linearly upward from the bottom through this substantially linear flow path. That is, most of the exhaust gas flowing backward smoothly flows from the downstream portion 27B of the drain passage 27 into the bypass passage 34. Then, the exhaust gas flowing into the bypass passage 34 flows upward through the bypass passage 34 and then flows through the branch portion 35 to the upstream portion 27A of the drain passage 27. Thus, according to the present embodiment, it is possible to suppress the exhaust gas flowing backward through the downstream portion 27B of the drain passage 27 from flowing into the collection passage 32, and it is possible to suppress the fine objects accumulated in the filter 43 of the collector 33 from being lifted up when the exhaust gas flowing backward passes through the inside of the collector 33 from the bottom upward.

[0065] (Details of the Configuration of the Fine Object Collection Device) FIG. 6 shows the details of the configuration of the fine object collection device 31. This figure shows a cross-section of the upstream portion 27A of the drain passage 27, the fine object collection device 31, and the upper end portion of the downstream portion 27B of the drain passage 27 cut along the cutting 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 particle collection device 31 includes a branch pipe 41, a collector 33, a connection hose 51, a bypass pipe 52, a connecting pipe 53, and a confluence pipe 54. The first outflow pipe portion 41B of the branch pipe 41, the connection hose 51, and the first inflow pipe portion 54A of the confluence pipe 54 form a collection passage 32. Further, the second outflow pipe portion 41C of the branch pipe 41, the bypass pipe 52, the connecting pipe 53, and the second inflow pipe portion 54B of the confluence pipe 54 form a bypass passage 34. In the branch pipe 41, the portion where the inflow pipe portion 41A branches into the first outflow pipe portion 41B and the second outflow pipe portion 41C corresponds to a branch portion 35. In the confluence pipe 54, the portion where the first inflow pipe portion 54A and the second inflow pipe portion 54B merge into the outflow pipe portion 54C corresponds to a confluence portion 36.

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

[0068] The trap 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 of, for example, a non-woven fabric or a resin mesh, and is formed in a bag shape that is open at the upper side and closed at the lower side. The holder 44 is formed in a cylindrical shape having an axis extending vertically, made of a resin with high heat resistance and rigidity, or a metal with high corrosion resistance. Further, a plurality of water passing holes 45 are provided in the peripheral wall portion of the holder 44. The filter 43 is disposed inside the holder 44 so as to cover each water passing hole 45 and the opening at the lower side of the holder 44. Further, 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 or the like, and is fixed in the holder 44 with the upper part of the filter 43 being open upward.

[0069] The case 46 is a member that houses the filter cartridge 42. The case 46 is formed in a cylindrical shape having an axis extending vertically, made of a resin with high heat resistance and rigidity, or a metal with high corrosion resistance. Further, the case 46 is divided into an upper case portion 47 that forms the upper part of the case 46 and a lower case portion 48 that forms the lower part of the case 46. The filter cartridge 42 is held between the upper case portion 47 and the lower case portion 48. Further, the filter cartridge 42 is disposed coaxially with the case 46.

[0070] The lower end portion 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 the present embodiment, the upper case portion 47 is integrally formed with the first outflow pipe portion 41B of the branch pipe 41. Further, a connection pipe portion 49 is provided below the lower case portion 48, and the lower case portion 48 and the connection pipe portion 49 are integrated.

[0071] Further, the lower case portion 48 is detachably coupled to the upper case portion 47 by a coupling member 50. The coupling member 50 is formed in a cylindrical shape, for example, by resin or metal. The coupling member 50 is held on the outer peripheral side of the lower case portion 48 so as to be rotatable and vertically movable with respect to the lower case portion 48. Threads are formed on the outer peripheral surface of the lower end portion of the upper case portion 47 and the inner peripheral surface of the coupling member 50, respectively. By screwing the coupling member 50 rotatably held on the lower case portion 48 to the lower end portion of the upper case portion 47, the lower case portion 48 is coupled to the upper case portion 47. Further, by rotating the coupling member 50 in the direction of loosening the screw and removing it from the lower end portion of the upper case portion 47, the lower case portion 48 is separated from the upper case portion 47.

[0072] The connection hose 51 is a tube connecting the case 46 and the first inflow tube portion 54A of the confluence pipe 54. The connection hose 51 is formed of a rubber hose having high heat resistance and rigidity. Although the connection hose 51 has high rigidity, it has flexibility. The upper end portion of the connection hose 51 is coaxially arranged with the case 46 as shown in FIG. 6 and is connected to the lower end portion of a connection pipe portion 49 integrally formed with the lower case portion 48. The connection hose 51 extends vertically downward from its upper end portion and then bends gently, and then extends downward while inclining rearward to the right, and then bends gently, and then extends downward while inclining forward to the left. Thus, since a part of the connection hose 51 is inclined with respect to the vertical, after rotating the coupling member 50 in the direction of loosening the screw to make the lower case portion 48 separable from the upper case portion 47, the upper end portion of the connection hose 51 can be grasped by hand, the upper end portion of the connection hose 51 can be pushed down, and the lower case portion 48 can be pulled away from the upper case portion 47. By pulling the lower case portion 48 away from the upper case portion 47, the filter cartridge 42 can be removed from the case 46. The user can remove the filter cartridge 42 from the case 46 in this way and remove the fine objects accumulated on the filter 43.

[0073] The bypass pipe 52 is formed of a rubber hose with high heat resistance and rigidity, or a pipe made of resin with high heat resistance and rigidity or metal with high corrosion resistance. 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 while inclining forward with respect to the vertical direction from its upper end, then bends, and thereafter extends vertically downward.

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

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

[0076] Further, the inner diameters of the inflow pipe portion 41A of the branch pipe 41, the first outflow pipe portion 41B of the branch pipe 41, the second outflow pipe portion 41C of the branch pipe 41, the connection hose 51, the bypass pipe 52, the connecting pipe 53, the first inflow pipe portion 54A of the confluence pipe 54, the second inflow pipe portion 54B of the confluence pipe 54, and the outflow pipe portion 54C of the confluence pipe 54 are substantially equal.

[0077] As described above, in the cooling device 21 of the outboard engine 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 such that the difference in 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 is smaller than the difference in 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 bypass passage 34. 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 due to such an arrangement of the upstream portion 27A of the drain passage 27, the collection passage 32, and the bypass passage 34. Therefore, without using a valve or the like that opens and closes the bypass passage 34 according to the presence or absence of clogging of the filter 43 of the collector 33, most of the cooling water flowing out from the upstream portion 27A of the drain passage 27 can be smoothly made to flow into the collection passage 32 and sent to the collector 33 when the filter 43 of the collector 33 is not clogged. That is, even when the upstream portion 27A of the drain passage 27 and the inlet of the bypass passage 34 are constantly in communication, it is possible to suppress the cooling water flowing out from the upstream portion 27A of the drain passage 27 from flowing into the bypass passage 34 when the filter 43 of the collector 33 is not clogged. Therefore, when the filter 43 of the collector 33 is not clogged, it is possible to suppress a decrease in the amount of cooling water flowing through the collector 33 due to the cooling water flowing into the bypass passage 34, and it is possible to suppress a decrease in the ability of the cooling device 21 to collect fine objects.

[0078] Also, in the cooling device 21 of the present embodiment, the upstream portion 27A of the drain passage 27 and the collection passage 32 are arranged such that 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 are the same as each other. The upstream portion 27A of the drain passage 27 and the bypass passage 34 are arranged such that 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 are different from each other. 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 drain passage 27 can be made to flow into the collection passage 32 more smoothly, and the collection ability of the cooling device 21 for fine objects can be sufficiently ensured.

[0079] Also, in the cooling device 21 of the present embodiment, the upstream portion 27A of the drain passage 27 is arranged such 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 such that the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is downward and vertical. The bypass passage 34 is arranged such 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, 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 drain passage 27 can be made to flow into the collection passage 32 more smoothly.

[0080] Also, in the branch portion 35, the collection passage 32 and the bypass passage 34 intersect each other at an acute angle. 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 made to flow into the bypass passage 34 smoothly. Thus, it is possible to prevent the flow of the cooling water in the drain passage 27 from deteriorating due to clogging of the filter 43 of the collector 33.

[0081] Further, in the cooling device 21 of the present embodiment, the downstream portion 27B of the collection passage 32, the bypass passage 34, and the drainage passage 27 are arranged such that the difference between the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drainage passage 27 is smaller than the difference between the flow direction of the cooling water flowing from the collection passage 32 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drainage passage 27. By arranging the downstream portion 27B of the drainage passage 27, the collection passage 32, and the bypass passage 34 in this way, the flow direction of the cooling water from the bypass passage 34 to the downstream portion 27B of the drainage passage 27 can be made closer to a straight line or made straight. Therefore, when the filter 43 of the collector 33 is clogged, the cooling water can flow smoothly from the bypass passage 34 to the downstream portion 27B of the drainage passage 27, and the cooling water flowing 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 backward through the collection passage 32. Further, by arranging the downstream portion 27B of the drainage passage 27, the collection passage 32, and the bypass passage 34 as described above, when the exhaust gas flows backward from the exhaust chamber 17 of the outboard motor 1 to the downstream portion 27B of the drainage passage 27, the flow direction of the exhaust gas from the downstream portion 27B of the drainage passage 27 to the bypass passage 34 can be made closer to a straight line or made straight, and the flow direction of the exhaust gas from the downstream portion 27B of the drainage passage 27 to the collection passage 32 can be bent. Therefore, the exhaust gas flowing backward from the exhaust chamber 17 to the downstream portion 27B of the drainage passage 27 can flow smoothly into the bypass passage 34, and the exhaust gas flowing backward through the downstream portion 27B of the drainage 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 backward flow of the cooling water or the exhaust gas into the collection passage 32 can be suppressed, so that the fine objects accumulated on the filter 43 can be prevented from being lifted up when the cooling water or the exhaust gas passes through the inside of the collector 33 from bottom to top. Therefore, even when 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 objects once accumulated on the filter 43 can be prevented from being lifted up and discharged outside the outboard motor 1 through the bypass passage 34 and the downstream portion 27B of the drainage passage 27.Thus, according to this embodiment, even when no valve or the like for opening and closing the bypass passage 34 is provided according to the presence or absence of clogging of the filter 43 of the collector 33, it is possible to suppress the fine objects once accumulated in the filter 43 from being discharged outside the outboard motor 1 due to the backflow of the cooling water or the exhaust gas. Therefore, the fine object collection ability of the cooling device 21 can be sufficiently ensured.

[0082] Also, in the cooling device 21 of this embodiment, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are substantially the same as each other. The collection passage 32 and the downstream portion 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the collection passage 32 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are different from each other. With this configuration, when the filter 43 of the collector 33 is clogged, 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 can be enhanced, and 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 can be enhanced. Therefore, the effect of suppressing the backflow of the cooling water or the exhaust gas into the collection passage 32 can be enhanced, and the effect of suppressing the entrainment of the fine objects accumulated in the filter 43 can be enhanced.

[0083] Also, in the cooling device 21 of this embodiment, the bypass passage 34 is arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 is downward and vertical, and the downstream portion 27B of the drain passage 27 is arranged such that the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 is downward and substantially vertical. The collection passage 32 is arranged such that the flow direction of the cooling water flowing from the collection passage 32 into the confluence portion 36 is not vertical. With this configuration, when the filter 43 of the collector 33 is clogged, 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 can be further enhanced. Therefore, the effect of suppressing the backflow of the cooling water into the collection passage 32 can be further enhanced.

[0084] Also, in the confluence portion 36, the collection passage 32 and the bypass passage 34 intersect 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 be smoothly flowed through the collection passage 32 to the downstream portion 27B of the drain passage 27. Further, when the filter 43 of the collector 33 is clogged, it is possible to suppress the cooling water flowing through the bypass passage 34 from flowing into the collection passage 32 from the outlet of the collection passage 32.

[0085] In addition, in the above embodiment, the upstream portion 27A of the drain passage 27 and the collection passage 32 are arranged such that 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 are the same as each other. 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 do not have to be exactly the same as each other, and may be slightly different within the range that can ensure the smoothness of the flow of the cooling water from the upstream portion 27A of the drain passage 27 to the collection passage 32 when the filter 43 of the collector 33 is not clogged.

[0086] Also, in the above embodiment, the bypass passage 34 and the downstream portion 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are substantially the same as each other. The flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 are not completely the same as each other but are slightly different as a result of the extension direction of the upper end portion (drain hole 30) of the downstream portion 27B of the drain passage 27 being slightly inclined with respect to the vertical. However, if the difference is within this range, the smoothness of the flow of the cooling water from the bypass passage 34 to the downstream portion 27B of the drain passage 27 and the smoothness of the flow of the exhaust gas from the downstream portion 27B of the drain passage 27 to the bypass passage 34 can be ensured, so a difference within this range can be regarded as the same. However, the extension direction of the upper end portion (drain hole 30) of the downstream portion 27B of the drain passage 27 may be set to be vertical, and the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 and the flow direction of the cooling water flowing from the confluence portion 36 into the downstream portion 27B of the drain passage 27 may be made completely the same.

[0087] Also, in the above embodiment, the upstream portion 27A of the drain passage 27 is arranged such 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. Specifically, the lower end portion of the upstream portion 27A of the drain passage 27 extends vertically. Further, the collection passage 32 is arranged such that the flow direction of the cooling water flowing from the branch portion 35 into the collection passage 32 is downward and vertical. Specifically, the upper end portion of the collection passage 32 extends vertically. Also, the bypass passage 34 is arranged such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence portion 36 is downward and vertical. Specifically, the lower end portion 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 with respect to the vertical.

[0088] Also, in the above embodiment, the fine object collection device 31 is arranged on the left side of the rear portion of the engine 2, but the fine object collection device 31 may be arranged at other positions around the engine 2, such as on the right side of the rear portion of the engine 2.

[0089] Further, the power source of the outboard motor 1 is not limited to an engine, and an electric motor may also be used. Further, the cooling device of the present invention can be provided not only for an outboard motor but also for other types of marine propulsion devices such as an inboard-outboard motor or an inboard motor.

[0090] Further, the present invention can be appropriately modified within a range not contrary to the gist or idea of the invention that can be read from the claims and the entire specification, and a cooling device for a marine propulsion device accompanied by such a modification is also included in the technical idea of the present invention.

Explanation of Reference Numerals

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

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, the upstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the collection passage is smaller than a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the bypass passage, the downstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the bypass passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage is smaller than a difference between a flow direction of the cooling water flowing from the collection passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage, 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, 2. A cooling device for a marine propulsion device, comprising: a bypass passage arranged such that a flow direction of cooling water flowing from the branch portion into the bypass passage is not vertical.

2. 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, the upstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the collection passage is smaller than a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the bypass passage, the downstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the bypass passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage is smaller than a difference between a flow direction of the cooling water flowing from the collection passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage, 4. A cooling device for a marine propulsion device, comprising: a first passage for passing through the first cooling passage and a second passage for passing through the second cooling passage;

3. 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, the upstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the collection passage is smaller than a difference between a flow direction of the cooling water flowing from the upstream portion of the drain passage into the branch portion and a flow direction of the cooling water flowing from the branch portion into the bypass passage, the downstream portion of the drain passage, the collection passage, and the bypass passage are arranged such that a difference between a flow direction of the cooling water flowing from the bypass passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage is smaller than a difference between a flow direction of the cooling water flowing from the collection passage to the junction and a flow direction of the cooling water flowing from the junction to the downstream portion of the drain passage, 4. A cooling device for a marine propulsion device, comprising: a first passage for passing through the first passage and a second passage for passing through the second passage;

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