Cooling system for ship propulsion systems

Abstract

To secure sufficient collection capacity for fine matter even when a valve for opening / closing a bypass passage is not used.SOLUTION: An upstream unit 27A of a drain passage, a collecting passage 32 provided with a collector 33, and a bypass passage 34 are arranged so that difference between flow direction of coolant flowing into a branch unit 35 from the upstream unit 27A and flow direction of the coolant flowing into the collecting passage 32 from the branch unit 35 is smaller than the difference between the flow direction of the coolant flowing into the branch unit 35 from the upstream unit 27A and the flow direction of the coolant flowing into the bypass 34 from the branch unit 35 in a cooling device for an outboard engine. Furthermore, the collecting passage 32 and the bypass passage 34 cross each other in an acute angle at the branching unit 35.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a cooling device for a ship 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 seas, 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. It is also known that seas, 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, residues of feed, 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 flowing through the water jacket flows in a drain pipe, 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 this 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] Furthermore, in the cooling device described in Patent Document 1, a bypass passage is connected to the drain pipe equipped with a filtration device, allowing cooling water to flow around the filtration device in the event of clogging. In addition, a relief valve is provided at the connection point between the upstream end of the bypass passage and the drain pipe. The relief valve closes when the filtration device is not clogging, directing the cooling water flowing through the drain pipe to the filtration device, and opens when the filtration device becomes clogging, directing the cooling water flowing through the drain pipe around the filtration device to the bypass passage. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-163872 [Overview of the project] [Problems that the invention aims to solve]

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

[0007] Incidentally, the inventor of this application is considering removing the relief valve 144 from the drain side configuration of a cooling device, for example, as shown in Figures 8(A) and (B). 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 malfunctions such as failure of the relief valve 144 and the burden of maintenance of the relief valve 144. However, removing the relief valve 144 from the drain side configuration of the cooling device will result in the following problems.

[0008] Figure 9(A) shows the configuration of the cooling system shown in Figures 8(A) and (B) with the relief valve 144 removed. When the relief valve 144 is removed from the configuration of the cooling system's drain side, the inlet of the bypass passage 145 is in constant communication with the drain passage 133. Therefore, as indicated by arrows X1 and X2 in Figure 9(A), cooling water may flow into the bypass passage 145 even when the filtration device 135 is not clogged. This phenomenon is likely to occur when, as indicated by the dashed line in Figure 9(A), a straight flow path is formed at the branching point where the bypass passage 145 branches off from the drain passage 133, and therefore the flow direction of the cooling water flowing from the drain passage 133 to the branching point (arrow X1) and the flow direction of the cooling water flowing from the branching point into the bypass passage 145 (arrow X2) are the same. Thus, even when the filtration device 135 is not clogged, if cooling water flows into the bypass passage 145, the amount of cooling water flowing through the filtration device 135 decreases. As a result, the cooling device's ability to collect fine particles decreases.

[0009] Furthermore, in the configuration of the cooling system shown in Figures 8(A) and (B) with the relief valve 144 removed, there is a concern that the cooling water flowing through the bypass passage 145 will flow back through the drain passage 133 after being discharged from the outlet of the bypass passage 145, causing fine particles accumulated in the filtration device 135 to be stirred up, and these stirred-up fine particles 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.

[0010] Figure 9(B), like Figure 9(A), shows the drain side configuration of the cooling system shown in Figures 8(A) and (B) with the relief valve 144 removed. Cooling water flowing through the bypass passage 145 normally flows out of the outlet of the bypass passage 145 and then flows downward through the drain passage 133, as indicated by arrows Y1 and Y2 in Figure 9(B). However, if the amount of cooling water flowing through the bypass passage 145 is large, the flow of the cooling water may become turbulent when it flows out of the outlet of the bypass passage 145, causing the cooling water to flow backward upward through the drain passage 133, as indicated by arrow Y3 in Figure 9(B). This backflow is likely to occur when the flow direction of the cooling water flowing from the bypass passage 145 to the drain passage 133 differs from the flow direction of the cooling water flowing downward from the bypass passage 145 to the drain passage 133 (arrow Y2), as shown by the dashed line in Figure 9(B). When cooling water flows backward 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 particles accumulated within the filtration device 135 will be stirred up by this cooling water. In the configuration where the relief valve 144 is removed, the inlet of the bypass passage 145 is constantly in communication with the drain passage 133. As a result, the stirred-up fine particles enter the bypass passage 145 from its inlet along with the cooling water, and may flow sequentially downward through the bypass passage 145 and the drain passage 133, potentially being discharged outside the outboard motor. Such backflow of cooling water could cause fine particles that have accumulated in the filter 135 to be discharged outside the outboard motor. Therefore, such backflow of cooling water leads to a decrease in the cooling system's ability to collect fine particles.

[0011] Furthermore, in the configuration of the cooling system shown in Figures 8(A) and (B) with the relief valve 144 removed, there is a concern that when the power source of the outboard motor is the engine, the engine's exhaust gas will flow back through the drainage passage 133, stirring up fine particles accumulated in the filtration device 135, and these stirred-up fine particles 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.

[0012] In other words, most outboard motors powered by an engine have an exhaust chamber located at the rear of the lower part of the outboard motor, and are configured so that exhaust gases discharged from the engine are sent to the exhaust chamber through an exhaust passage. When an outboard motor with such a configuration has a water-cooled cooling system, the cooling system is often configured so that cooling water flowing through a drainage passage is discharged into the exhaust chamber. When a cooling system has such a configuration, the drainage passage and the exhaust passage are connected via the exhaust chamber, so when the pressure in the drainage passage becomes lower than the pressure in the exhaust chamber, exhaust gas sent from the exhaust passage into the exhaust chamber may flow back into the drainage passage.

[0013] Figure 9(C), like Figures 9(A) and 9(B), shows the configuration of the cooling system on the drain side shown in Figures 8(A) and (B) with the relief valve 144 removed. As indicated by arrow Z in Figure 9(C), exhaust gas flowing backward from the exhaust chamber through the drain passage 133 may reach the filter 135 and flow from bottom to top within the filter 135. The phenomenon of exhaust gas flowing backward through the drain passage 133 reaching the filter 135 is likely to occur when the flow path from below the filter 135 to the filter 135 is straight, as indicated by the dashed line in Figure 9(C), and therefore the exhaust gas flowing backward through the drain passage 133 flows in a straight line toward the filter 135. When exhaust gas flows from bottom to top through the filter 135, fine particles accumulated in the filter 135 are stirred up by the exhaust gas. These stirred-up fine particles, along with the cooling water, flow sequentially downward through the bypass passage 145 and the drainage passage 133, potentially being discharged outside the outboard motor. Therefore, such backflow of exhaust gas also leads to a decrease in the cooling device's ability to capture fine particles.

[0014] The present invention has been made in view of the problems described above, for example, and the object of the present invention is to provide a cooling device for a ship's propulsion system that can sufficiently secure the ability to collect fine particles even without using a valve or the like that which opens and closes a bypass passage depending on whether or not the collector (filtration device) is clogged. [Means for solving the problem]

[0015] To solve the above problems, the present invention provides a cooling device for a ship's propulsion system, which is installed in the ship's propulsion system and takes in water from outside the ship's propulsion system into the ship's propulsion system, cools the power source of the ship's propulsion system by flowing the taken-in water around or inside the power source of the ship's propulsion system as cooling water, and discharges the cooling water that has flowed around or inside the power source to the outside of the ship's propulsion system, comprising: a drainage passage for discharging the cooling water that has flowed around or inside the power source to the outside of the ship's propulsion system; a collection passage interposed between the upstream and downstream parts of the drainage passage and connecting the upstream and downstream parts of the drainage passage; and a collection passage provided in the middle of the collection passage for the cooling water that flows through the collection passage from the upstream part of the drainage passage toward the downstream part of the drainage passage. The drainage passage comprises a collector for collecting contained fine particles, a bypass passage connected in parallel with the collection passage between the upstream and downstream portions of the drainage passage, a branching section where the upstream portion of the drainage passage branches into the collection passage and the bypass passage, and a confluence section where the collection passage and the bypass passage merge at the downstream portion of the drainage passage, wherein 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 cooling water flowing from the upstream portion of the drainage passage to the branching section and the flow direction of cooling water flowing from the branching section to the collection passage is smaller than the difference between the flow direction of cooling water flowing from the upstream portion of the drainage passage to the branching section and the flow direction of cooling water flowing from the branching section to the bypass passage. [Effects of the Invention]

[0016] According to the present invention, even without using a valve or the like to open and close a bypass passage depending on whether or not the collector is clogged, the ability to collect fine particles can be sufficiently ensured. [Brief explanation of the drawing]

[0017] [Figure 1] This is an overall view showing an outboard motor equipped with a cooling device according to an embodiment of the present invention. [Figure 2] This is an external view showing the engine of an outboard motor in an embodiment of the present invention, viewed from the left. [Figure 3]It is an external view showing the engine in FIG. 2 as viewed from the rear. [Figure 4] It is an explanatory diagram showing the configuration of the cooling device of an embodiment of the present invention. [Figure 5] It is an explanatory diagram showing the basic configuration of the fine object collection device in the cooling device of an embodiment of the present invention. [Figure 6] It is a cross-sectional view showing the upstream part of the drainage passage, the fine object collection device, and the downstream part of the drainage passage cut along the cutting line VI-VI in FIG. 3. [Figure 7] It is a cross-sectional view showing an enlarged case and filter cartridge in FIG. 6. [Figure 8] It is an explanatory diagram showing the configuration on the drainage side of a conventional cooling device. [Figure 9] It is an explanatory diagram showing the configuration on the drainage side of a conventional cooling device with the relief valve removed.

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 a marine propulsion engine, takes in water outside the marine propulsion engine into the marine propulsion engine, 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 discharges the cooling water after flowing 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 after flowing around or inside the power source to the outside of the marine propulsion engine, a collection passage interposed between the upstream part and the downstream part of the drainage passage and connecting the upstream part and the downstream part 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 part of the drainage passage toward the downstream part of the drainage passage through the collection passage, a bypass passage connected in parallel with the collection passage between the upstream part and the downstream part of the drainage passage, a branch part where the upstream part of the drainage passage branches into the collection passage and the bypass passage, and a confluence part where the collection passage and the bypass passage merge into the downstream part of the drainage passage.

[0019] 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 portion 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 portion 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 portion 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 portion 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 portion of the drainage passage from flowing into the bypass passage when the collector is not clogged. Thus, 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] In the cooling device of the present embodiment, 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.

[0022] By arranging the downstream section of the drainage passage, the collection passage, and the bypass passage in this manner, the flow direction of cooling water from the bypass passage to the downstream section of the drainage passage can be made nearly straight or straight. Therefore, when the collector is clogged, cooling water can flow smoothly from the bypass passage to the downstream section of the drainage passage, and backflow of cooling water flowing through the bypass passage into the collection passage can be suppressed. Furthermore, by arranging the downstream section of the drainage passage, the collection passage, and the bypass passage as described above, when exhaust gas flows back from the exhaust chamber of the ship's propulsion engine to the downstream section of the drainage passage, the flow direction of the exhaust gas from the downstream section of the drainage passage to the bypass passage can be made nearly straight or straight, and the flow direction of the exhaust gas from the downstream section of the drainage passage to the collection passage can be curved. Therefore, exhaust gas that has flowed back from the exhaust chamber of the ship's propulsion engine to the downstream section of the drainage passage can be smoothly flowed into the bypass passage, and backflow of exhaust gas that has flowed back from the downstream section of the drainage passage into the collection passage can be suppressed.

[0023] In this way, by suppressing the backflow of cooling water or exhaust gas into the collection passage, it is possible to prevent the fine particles accumulated in the collection from being stirred up by the cooling water or exhaust gas passing from bottom to top inside the collection. Therefore, even if the inlet of the collection passage and the inlet of the bypass passage are always in communication at the branching point, it is possible to prevent the fine particles that have been accumulated in the collection from being stirred up and discharged outside the ship's propulsion system through the downstream parts of the bypass passage and drainage passage. Thus, according to this embodiment, even if there is no valve or the like to open and close the bypass passage depending on whether the collection passage is clogged or not, it is possible to prevent the fine particles that have been accumulated in the collection from being discharged outside the ship's propulsion system due to the backflow of cooling water or exhaust gas, and therefore, the fine particle collection capacity of the cooling system can be sufficiently ensured. [Examples]

[0024] The following describes an embodiment of the cooling device for a ship's propulsion system according to the present invention, with reference to Figures 1 to 7. In the embodiment, when describing the directions of forward (Fd), aft (Bd), up (Ud), down (Dd), left (Ld), and right (Rd), refer to the arrows drawn in the lower left of Figures 1 to 7.

[0025] (Outboard motor) Figure 1 shows an overall view of an outboard motor 1, a type of marine propulsion system, from the left. As shown in Figure 1, the outboard motor 1 comprises an engine 2 as a power source, a drive shaft 3 that rotates in response to the power of the engine 2, a propeller 4 that generates thrust 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 in the figure, the gear mechanism 6 is also equipped 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 located at the top of the outboard motor 1. The gear mechanism 6, propeller shaft 5, and propeller 4 are located at the bottom of the outboard motor 1. The drive shaft 3 extends vertically between the engine 2 and the gear mechanism 6.

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

[0027] Figure 2 shows the engine 2 viewed from the left. Figure 3 shows the engine 2 viewed from the rear. Engine 2 is, for example, a 4-stroke, 4-cylinder gasoline engine, and its cooling system is water-cooled. Engine 2 is arranged so that the extension direction of the crankshaft is vertical. As shown in Figure 2, in engine 2, the crankcase 12 is located at the front, the cylinder block 13 is located behind the crankcase 12, and the cylinder head 14 is located behind the cylinder block 13. The rear of the cylinder head 14 is covered by a cylinder head cover 15.

[0028] As shown in Figure 1, the outboard motor 1 is provided with an exhaust passage 16 for discharging exhaust gas 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 the 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 the lower rear part of the outboard motor 1. In the outboard motor 1 of this embodiment, the exhaust chamber 17 is provided in the part extending from the rear of the middle case 10 to the rear of the lower case 11. The exhaust gas discharged from the exhaust port of the engine 2 is sent to the exhaust chamber 17 via the exhaust passage 16, and then discharged to the outside of the outboard motor 1 through an outlet provided, for example, on the shaft of the propeller 4. Note that the exhaust port of the engine 2 and the exhaust passage 16 are not shown in Figures 2 and 3.

[0029] (cooling device) The outboard motor 1 is equipped with a cooling device 21 for cooling the engine 2 and other heat-generating parts of the outboard motor 1 by using the surrounding water, 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 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 micro-object collection device 31.

[0031] The water intake 22 is an opening that takes in water from around the outboard motor 1 into the outboard motor 1, and is located in the part of the outboard motor 1 that is submerged below the water surface, specifically in a part of the lower case 11 (see Figure 1). The water intake 22 is also equipped with a strainer or a cover with numerous small holes to prevent objects larger than microscopic particles, such as stones and algae, from entering the outboard motor 1 along with seawater, lake water, or river water.

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

[0033] The water pump 24 is a pump that draws in water taken into the outboard motor 1 from the water intake 22 and discharges the drawn-in water as cooling water. It is installed, for example, inside the lower case 11 or the middle case 10. The water pump 24 is operated using the rotation of the drive shaft 3.

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

[0035] The water jacket 26 is a mechanism that cools the engine 2 by circulating 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 that has flowed through the water jacket 26 to the outside of the outboard motor 1, and is formed by a hose or pipe installed inside, for example, the engine top cover 8, the engine bottom cover 7, and the upper case 9. A micro-object collection device 31 is interposed in the middle of the drainage passage 27, and therefore the drainage passage 27 is divided into an upstream section 27A, which is the part upstream of the micro-object collection device 31, and a downstream section 27B, which is the part downstream of the micro-object collection device 31.

[0037] As shown in Figures 2 and 3, the upstream portion 27A of the drainage passage 27 is located in the area from above the cylinder head 14 to the upper left of the cylinder head cover 15. The upstream portion 27A of the drainage passage 27 is formed from a heat-resistant and rigid resin pipe or a corrosion-resistant metal pipe, or a heat-resistant and rigid rubber hose, etc. The upper end of the upstream portion 27A of the drainage passage 27 is connected to the outlet 26A of the water jacket 26 located above the cylinder head 14. Furthermore, the upstream portion 27A of the drainage passage 27 extends to the left from the outlet 26A of the water jacket 26, then bends, then extends rearward while sloping downward to the left of the rear upper portion of the engine 2, then bends, then extends horizontally rearward to the left of the rear upper portion of the engine 2, then bends, and then extends vertically downward to the left of the rear upper portion of the engine 2. The lower end of the upstream portion 27A of the drainage passage 27 faces downward. Furthermore, the upper ends of the collection passage 32 and bypass passage 34 of the micro-object collection device 31 (specifically, the upper ends of the inlet pipe section 41A of the branch pipe 41) are connected to the lower end of the upstream section 27A of the drainage passage 27.

[0038] Furthermore, the downstream portion 27B of the drainage passage 27 is located in the area from the lower left rear of the engine 2 to the exhaust chamber 17. The upper end of the downstream portion 27B of the drainage passage 27 is formed by a drain hole 30 formed in the lower left rear of the engine 2 housing. The drain hole 30 extends downward, although it is slightly inclined to the right, and the opening at the upper end of the drain hole 30 faces upward. The lower ends of the collection passage 32 and the bypass passage 34 (specifically, the lower ends of the outlet pipe section 54C of the confluence pipe 54) are connected to the upper end of the drain hole 30. In addition, the portion of the downstream portion 27B of the drainage passage 27 below the drain hole 30 is formed by hoses or pipes provided inside the engine bottom cover 7 and upper case 9, etc. Furthermore, the lower end of the downstream portion of the drainage passage 27 is connected to the exhaust chamber 17 as shown in Figure 4.

[0039] The thermostat 28 is a device that restricts the flow of coolant in order to warm up the engine 2 or to prevent overcooling of the engine 2, and is installed, for example, near the outlet 26A of the water jacket 26. The thermostat 28 opens when the temperature of the coolant flowing in the water jacket 26 reaches or exceeds a predetermined reference temperature, and closes when the temperature of the coolant falls below the above reference temperature.

[0040] The pressure valve 29 is a valve that reduces the water pressure in the water supply passage 25 or water jacket 26 by releasing the cooling water discharged from the water pump 24 to the exhaust chamber 17 when the flow of 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 micro-object collection device 31 is a device that collects micro-objects contained in seawater, lake water, or river water, etc., that is taken into the outboard motor 1 from outside the motor 1 and used as cooling water to cool the engine 2. The micro-object collection device 31 will be described in detail later.

[0042] In a cooling system 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 from around the outboard motor 1 is taken into the outboard motor 1 from the intake port 22, and this water flows sequentially through the intake passage 23 and the supply passage 25 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 section 27A of the drainage passage 27, flows through the upstream section 27A of the drainage passage 27, then flows inside the fine object collection device 31, then flows through the downstream section 27B of the drainage 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 along with the exhaust gas, for example, through an outlet 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, the water taken into the outboard motor 1 from the water intake 22 flows sequentially 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 discharged into the exhaust chamber 17. The cooling water discharged into the exhaust chamber 17 is then discharged outside the outboard motor 1 along with the exhaust gas.

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

[0044] The micro-objects are, for example, tiny debris such as microplastics, or residue from feed used in aquaculture. The size of the micro-objects is, for example, between approximately 0.1 mm and approximately 5 mm. Because of their size, the micro-objects are not removed by the strainer or cover with numerous small holes provided at 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 micro-objects enter the outboard motor 1 from the water intake 22 along with seawater, lake water, or river water, and flow into the micro-object collection device 31 through the water intake passage 23, the water supply passage 25, the water jacket 26, and the upstream section 27A of the drainage passage 27.

[0045] Figure 5 shows the basic configuration of the micro-object collection device 31. As shown in Figure 5, the micro-object collection device 31 includes a collection passage 32, a collector 33, a bypass passage 34, a branching section 35, and a merging section 36.

[0046] The collection passage 32 is interposed between the upstream section 27A and the downstream section 27B of the drainage passage 27, and is a passage that connects the upstream section 27A and the downstream section 27B of the drainage passage 27. The collection passage 32 directs the cooling water flowing in the upstream section 27A of the drainage passage 27 to the downstream section 37B of the drainage passage 27, passing it through the collector 33.

[0047] The collector 33 is installed in the middle of the collection passage 32 and is a device that collects fine particles contained in the cooling water that flows through the collection passage 32 from the upstream part 27A of the drainage passage 27 to the downstream part 27B of the drainage passage 27. As will be described later, the collector 33 captures fine particles in the cooling water by passing the cooling water flowing through the collection passage 32 through the filter 43 and removes the fine particles from the cooling water.

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

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

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

[0051] Specifically, the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 are the same. In contrast, the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the bypass passage 34 are different.

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

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

[0054] Furthermore, at the branching section 35, the collection passage 32 and the bypass passage 34 intersect 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, approximately 20 degrees or more and less than 90 degrees. Alternatively, 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 branching section 35; in this case, P becomes 90 degrees.

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

[0056] Specifically, the bypass passage 34 and the downstream section 27B of the drainage passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drainage passage 27 are substantially the same. In contrast, the collection passage 32 and the downstream section 27B of the drainage passage 27 are arranged such that the flow direction of the cooling water flowing from the collection passage 32 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drainage passage 27 are different.

[0057] The reason why the relationship between the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drain passage 27 is described as "approximately the same" is that, as shown in Figure 3, when the engine 2 is viewed from the rear, the upper end (drain hole 30) of the downstream section 27B of the drain passage 27 is slightly inclined to the right with respect to the vertical. This slight inclination of the upper end of the downstream section 27B of the drain passage 27 to the right with respect to the vertical does not significantly reduce the effect of the cooling device 21 in this embodiment, which is to suppress the backflow of cooling water that has flowed through the bypass passage 34 into the collection passage 32, nor does it significantly reduce the effect of the cooling device 21 in this embodiment, which is to suppress the backflow of exhaust gas that has flowed back from the exhaust chamber 17 into the collection passage 32 from the lower end of the collection passage 32.

[0058] More specifically, the bypass passage 34 is positioned such that the flow direction of the cooling water flowing from the bypass passage 34 into the confluence section 36 is downward and vertical, as indicated by arrow E. Similarly, the downstream section 27B of the drainage passage 27 is positioned such that the flow direction of the cooling water flowing from the confluence section 36 into the downstream section 27B of the drainage passage 27 is downward and approximately vertical, as indicated by arrow F. In contrast, the collection passage 32 is positioned such that the flow direction of the cooling water flowing from the collection passage 32 into the confluence section 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 section 27B of the drainage passage 27 are connected to each other at the confluence section 36. The lower end of the bypass passage 34 extends vertically, and the upper end of the downstream section 27B of the drainage passage 27 extends approximately vertically, with the lower end of the bypass passage 34 and the upper end of the downstream section 27B of the drainage passage 27 being arranged approximately coaxially with each other. As a result, a substantially straight flow path is formed from the lower end of the bypass passage 34 to the upper end of the downstream section 27B of the drainage passage 27, extending approximately vertically. In contrast, the lower end of the collection passage 32, which is connected to the upper end of the downstream section 27B of the drainage passage 27 at the confluence section 36, is inclined with respect 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 section 27B of the drainage passage 27.

[0060] Furthermore, at the confluence 36, the collection passage 32 and the bypass passage 34 intersect 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, approximately 20 degrees or more and less than 90 degrees. Alternatively, the lower end of the collection passage 32 may be extended horizontally so that the collection passage 32 and the bypass passage 34 intersect at a right angle at the confluence 36; in this case, Q becomes 90 degrees.

[0061] The collection passage 32 extends vertically downward from the branching section 35, then curves, and then extends downward while inclined relative to the vertical, reaching the confluence section 36. The collector 33 is installed in the middle of the vertically extended portion of the collection passage 32. The bypass passage 34 extends downward while inclined relative to the vertical from the branching section 35, then curves, and then extends vertically downward, reaching the confluence section 36.

[0062] (Cooling water flow in a micro-object collection device) In Figure 5, the lower end of the upstream section 27A of the drainage passage 27 and the upper end of the collection passage 32 both extend vertically. Furthermore, the lower end of the upstream section 27A of the drainage passage 27 and the upper end of the collection passage 32 are coaxially positioned, and a vertically extending straight flow path is formed from the lower end of the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 are both downward and vertical, as indicated by arrows A and B, and are identical. In contrast, the upper end of the bypass passage 34 is inclined with respect to the vertical, and a curved flow path is formed from the lower end of the upstream section 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 section 35 to 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 section 27A of the drainage passage 27 to the branch section 35 is different from the flow direction of the cooling water flowing from the branch section 35 to the bypass passage 34. Therefore, if the filter 43 of the collector 33 is not clogged, most of the cooling water that flows from the upstream section 27A of the drainage passage 27 to the branch section 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. As the cooling water passes through the filter 43, fine particles in the cooling water are removed. The cooling water that has passed through the filter 43 flows through the lower part of the collection passage 32 and the confluence section 36 in sequence and into the downstream section 27B of the drainage passage 27. Thus, according to this embodiment, without using a valve or the like to open and close the bypass passage 34 depending on whether the filter 43 of the collector 33 is clogged or not, when the filter 43 of the collector 33 is not clogged, most of the cooling water that flows out from the upstream part 27A of the drain passage 27 can be allowed to flow into the collection passage 32 and sent to the collector 33.

[0063] On the other hand, if the filter 43 of the collector 33 is clogged, it becomes difficult for the cooling water to pass through the filter 43, causing the flow of cooling water to stagnate inside the collector 33 and in the upper part of the collection passage 32 (the part above the collector 33). Therefore, if the filter 43 of the collector 33 is clogged, most of the cooling water that flows from the upstream part 27A of the drainage passage 27 to the branching part 35 flows into the bypass passage 34, and then flows through the bypass passage 34 and the confluence part 36 in sequence into the downstream part 27B of the drainage passage 27. Here, the lower end of the bypass passage 34 extends vertically, and the upper end of the downstream part 27B of the drainage passage 27 extends approximately vertically, with the lower end of the bypass passage 34 and the upper end of the downstream part 27B of the drainage passage 27 being arranged approximately coaxially with each other. As a result, a substantially straight flow path is formed from the lower end of the bypass passage 34 to the upper end of the downstream part 27B of the drainage passage 27, extending approximately vertically. Therefore, the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drainage passage 27 are both downward and approximately vertical, as indicated by arrows E and F, and are approximately the same. Consequently, the cooling water flows smoothly downward in an approximately linear and approximately vertical manner from the bypass passage 34 to the downstream section 27B of the drainage passage 27. Thus, according to this embodiment, it is possible to suppress the disruption of the flow of cooling water flowing from the bypass passage 34 to the confluence section 36 and the backflow of the collection passage 32 from the lower end of the bypass passage 34. Consequently, by having the cooling water pass through the collector 33 from bottom to top, it is possible to suppress the stirring up of fine particles accumulated in the filter 43 of the collector 33.

[0064] (Flow of exhaust gases that have flowed back out of the exhaust chamber) As can be seen in Figures 1 and 4, the exhaust chamber 17 of the outboard motor 1 is connected to the exhaust passage 16 and the downstream section 27B of the drainage passage 27. As a result, the exhaust passage 16 and the downstream section 27B of the drainage passage 27 are connected via the exhaust chamber 17. Therefore, when the pressure in the downstream section 27B of the drainage passage 27 becomes lower than the pressure in the exhaust chamber 17, exhaust gas sent from the exhaust passage 16 into the exhaust chamber 17 flows from the exhaust chamber 17 into the downstream section 27B of the drainage passage 27, causing a backflow in the downstream section 27B of the drainage passage 27. In the outboard motor 1, the lower end of the bypass passage 34 and the upper end of the downstream section 27B of the drainage passage 27 both extend approximately vertically. Furthermore, the lower end of the bypass passage 34 and the upper end of the downstream section 27B of the drainage passage 27 are arranged approximately coaxially with each other, and a substantially straight flow path is formed extending approximately vertically from the lower end of the bypass passage 34 to the upper end of the downstream section 27B of the drainage passage 27. Therefore, most of the exhaust gas that flows back through the downstream section 27B of the drainage passage 27 flows in a nearly straight line from bottom to top through this nearly straight passage. In other words, most of the backflowing exhaust gas flows smoothly from the downstream section 27B of the drainage passage 27 into the bypass passage 34. The exhaust gas that flows into the bypass passage 34 then flows from bottom to top through the bypass passage 34, and then flows through the branch section 35 to the upstream section 27A of the drainage passage 27. In this way, according to this embodiment, it is possible to suppress the flow of exhaust gas that flows back through the downstream section 27B of the drainage passage 27 into the collection passage 32, and by having the backflowing exhaust gas pass through the collector 33 from bottom to top, it is possible to suppress the stirring up of fine particles accumulated in the filter 43 of the collector 33.

[0065] (Details of the micro-object collection device configuration) Figure 6 shows a detailed view of the configuration of the micro-object collection device 31. This figure shows a cross-section of the upper end of the upstream section 27A of the drainage passage 27, the micro-object collection device 31, and the downstream section 27B of the drainage passage 27, viewed from the left, along the cutting line VI-VI in Figure 3. Figure 7 shows a magnified view of the collector 33 in Figure 6.

[0066] Specifically, the micro-object collection device 31 comprises a branch pipe 41, a collector 33, a connecting hose 51, a bypass pipe 52, a connecting pipe 53, and a confluence pipe 54, as shown in Figure 6. The first outflow section 41B of the branch pipe 41, the connecting hose 51, and the first inflow section 54A of the confluence pipe 54 form a collection passage 32. The second outflow section 41C of the branch pipe 41, the bypass pipe 52, the connecting pipe 53, and the second inflow section 54B of the confluence pipe 54 form a bypass passage 34. In the branch pipe 41, the portion where the inflow section 41A branches into the first outflow section 41B and the second outflow section 41C corresponds to the branch section 35. In the confluence pipe 54, the portion where the first inflow section 54A and the second inflow section 54B merge into the outflow section 54C corresponds to the confluence section 36.

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

[0068] The collector 33 has a filter cartridge 42 and a case 46. As shown in Figure 7, the filter cartridge 42 has a filter 43 that captures fine particles and allows cooling water to pass through, and a holder 44 that holds the filter 43. The filter 43 is made of, for example, nonwoven fabric or resin mesh, and is formed in the shape of a bag that is open at the top and closed at the bottom. The holder 44 is made of a resin with high heat resistance and rigidity, or a metal with high corrosion resistance, and is formed in the shape of a cylinder with a vertically extended axis. In addition, a plurality of water passage holes 45 are provided in the peripheral wall of the holder 44. The filter 43 is positioned inside the holder 44 so as to cover each water passage hole 45 and the opening at the bottom of the holder 44. The upper part of the filter 43 is attached to the inner circumferential surface of the upper part of the holder 44 with, for example, an adhesive, and is fixed inside the holder 44 with the upper part of the filter 43 open upwards.

[0069] The case 46 is a component that houses the filter cartridge 42. The case 46 is formed in a cylindrical shape with a vertically extended axis, using a resin with high heat resistance and rigidity, or a metal with high corrosion resistance. 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. The filter cartridge 42 is also arranged coaxially with the case 46.

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

[0071] Furthermore, the lower case portion 48 is detachably connected to the upper case portion 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 circumference of the lower case portion 48 so as to be rotatable relative to the lower case portion 48 and movable in the vertical direction relative to the lower case portion 48. Screws are formed on the outer circumference of the lower end of the upper case portion 47 and on the inner circumference of the connecting member 50, respectively. By screwing the connecting member 50, which is rotatably held by the lower case portion 48, to the lower end of the upper case portion 47, the lower case portion 48 is connected to the upper case portion 47. The lower case portion 48 can also be separated from the upper case portion 47 by rotating the connecting member 50 in the direction that loosens the screw and removing it from the lower end of the upper case portion 47.

[0072] The connecting hose 51 is a pipe that connects the case 46 to the first inlet pipe section 54A of the junction pipe 54. The connecting hose 51 is made of a rubber hose with high heat resistance and rigidity. Although the connecting hose 51 is rigid, it is also flexible. As shown in Figure 6, the upper end of the connecting hose 51 is arranged coaxially with the case 46 and is connected to the lower end of the connecting pipe section 49 which is integrally formed with the lower case section 48. The connecting hose 51 extends vertically downward from its upper end, then bends gently, then extends downward while tilting to the right rear, then bends gently, and then extends downward while tilting to the left front. In this way, a part of the connecting hose 51 is tilted relative to the vertical, so after rotating the connecting member 50 in the direction that loosens the screw to make the lower case section 48 separable from the upper case section 47, the upper end of the connecting hose 51 can be grasped by hand, and the upper end of the connecting hose 51 can be pushed down to separate the lower case section 48 from the upper case section 47. By separating the lower case portion 48 from the upper case portion 47, the filter cartridge 42 can be removed from the case 46. In this way, the user can remove the filter cartridge 42 from the case 46 and remove the fine particles accumulated in the filter 43.

[0073] The bypass pipe 52 is made of a heat-resistant and rigid rubber hose, or a heat-resistant and rigid resin or corrosion-resistant metal pipe. The upper end of the bypass pipe 52 is connected to the lower end of the second outlet pipe section 41C of the branch pipe 41. From its upper end, the bypass pipe 52 extends downward while inclined forward relative to the vertical, then bends, and then extends vertically downward.

[0074] The connecting pipe 53 is made of a resin with high heat resistance and rigidity, or a metal with high corrosion resistance. The connecting pipe 53 extends vertically and 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 connects the connecting hose 51 to the downstream section 27B of the drainage passage 27, and also connects the bypass pipe 52 to the downstream section 27B of the drainage passage 27 via the connecting pipe 53. The confluence pipe 54 is made of a resin with high heat resistance and rigidity, or a metal with high corrosion resistance. The confluence pipe 54 has a first inlet section 54A, a second inlet section 54B, and an outlet section 54C. In the confluence pipe 54, the second inlet section 54B is located on the upper side, and the outlet section 54C is located on the lower side. The second inlet section 54B and the outlet section 54C are arranged coaxially, and the portion of the confluence pipe 54 from the second inlet section 54B to the outlet section 54C extends vertically in a straight line. The second inlet section 54B and the connecting pipe 53 are also arranged coaxially, and the lower end of the connecting pipe 53 is connected to the upper end of the second inlet section 54B. Furthermore, the lower end of the outflow pipe section 54C is positioned substantially coaxially with the drain hole 30 that forms the upper end of the downstream section 27B of the drainage 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 backward from approximately the middle of the vertical direction of the portion from the second inflow pipe section 54B to the outflow pipe section 54C in the combined pipe 54, while sloping upward and to the right. The lower end of the connecting hose 51 is connected to the upper end of the first inflow pipe section 54A.

[0076] Furthermore, the inner diameters of the inlet section 41A of the branch pipe 41, the first outlet section 41B of the branch pipe 41, the second outlet section 41C of the branch pipe 41, the connecting hose 51, the bypass pipe 52, the connecting pipe 53, the first inlet section 54A of the confluence pipe 54, the second inlet section 54B of the confluence pipe 54, and the outlet section 54C of the confluence 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 section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 is smaller than the difference between the flow direction of the cooling water flowing from the upstream section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the bypass passage 34. With the upstream section 27A of the drainage passage 27, the collection passage 32, and the bypass passage 34 arranged in this manner, when the filter 43 of the collector 33 is not clogged, the cooling water flowing out from the upstream section 27A of the drainage passage 27 flows more easily into the collection passage 32 than into the bypass passage 34. Therefore, without using a valve or the like to open and close the bypass passage 34 depending on whether the filter 43 of the collector 33 is clogged, when the filter 43 of the collector 33 is not clogged, most of the cooling water that flows out from the upstream part 27A of the drainage passage 27 can be smoothly allowed to flow into the collection passage 32 and sent to the collector 33. In other words, even when the upstream part 27A of the drainage passage 27 and the inlet of the bypass passage 34 are always in communication, when the filter 43 of the collector 33 is not clogged, it is possible to suppress the flow of cooling water that flows out from the upstream part 27A of the drainage passage 27 into the bypass passage 34. Thus, when the filter 43 of the collector 33 is not clogged, it is possible to suppress the decrease in the amount of cooling water flowing inside the collector 33 due to the flow of cooling water into the bypass passage 34, and suppress the decrease in the fine object collection capacity of the cooling device 21.

[0078] Furthermore, in the cooling device 21 of this embodiment, the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 are the same, while the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the bypass passage 34 are different. With this configuration, when the filter 43 of the collector 33 is not clogged, most of the cooling water that flows out from the upstream section 27A of the drainage passage 27 can flow more smoothly into the collection passage 32, and the fine object collection capacity of the cooling device 21 can be sufficiently ensured.

[0079] Furthermore, in the cooling device 21 of this embodiment, 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 to the branching portion 35 is downward and vertical, the collection passage 32 is arranged such that the flow direction of the cooling water flowing from the branching portion 35 to the collection passage 32 is downward and vertical, and the bypass passage 34 is arranged such that the flow direction of the cooling water flowing from the branching portion 35 to 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 that flows out from the upstream portion 27A of the drainage passage 27 can flow more smoothly into the collection passage 32.

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

[0081] Furthermore, in the cooling device 21 of this embodiment, the collection passage 32, the bypass passage 34, and the downstream section 27B of the drainage passage 27 are arranged such that the difference between the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 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 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drainage passage 27. By arranging the downstream section 27B of the drainage 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 section 27B of the drainage passage 27 can be made closer to a straight line, or even made straight. Therefore, when the filter 43 of the collector 33 is clogged, cooling water can flow smoothly from the bypass passage 34 to the downstream section 27B of the drain passage 27, and the cooling water that has flowed through the bypass passage 34 can flow into the collection passage 32 from the outlet of the collection passage 32, preventing backflow through the collection passage 32. Furthermore, by arranging the downstream section 27B of the drain passage 27, the collection passage 32, and the bypass passage 34 as described above, when exhaust gas flows back from the exhaust chamber 17 of the outboard motor 1 through the downstream section 27B of the drain passage 27, the flow direction of the exhaust gas from the downstream section 27B of the drain passage 27 to the bypass passage 34 can be made nearly straight or straight, and the flow direction of the exhaust gas from the downstream section 27B of the drain passage 27 to the collection passage 32 can be made curved. Therefore, exhaust gas that has flowed back from the exhaust chamber 17 through the downstream section 27B of the drainage passage 27 can be smoothly flowed to the bypass passage 34, and exhaust gas that has flowed back through the downstream section 27B of the drainage passage 27 can flow into the collection passage 32 from the outlet of the collection passage 32, thereby suppressing backflow through the collection passage 32. In this way, backflow of cooling water or exhaust gas into the collection passage 32 can be suppressed, so that the cooling water or exhaust gas passes through the collector 33 from bottom to top, preventing fine particles accumulated in the filter 43 from being stirred up. Therefore, even when the inlet of the collection passage 32 and the inlet of the bypass passage 34 are constantly in communication at the branch section 35, it is possible to suppress fine particles that have been temporarily accumulated in the filter 43 from being stirred up and discharged outside the outboard motor 1 through the bypass passage 34 and the downstream section 27B of the drainage passage 27.Thus, according to this embodiment, even if there is no valve or the like to open and close the bypass passage 34 depending on whether or not the filter 43 of the collector 33 is clogged, it is possible to suppress the discharge of fine particles that have been temporarily accumulated in the filter 43 to the outside of the outboard motor 1 due to the backflow of cooling water or exhaust gas, and therefore, the fine particle collection capacity of the cooling device 21 can be sufficiently ensured.

[0082] Furthermore, in the cooling device 21 of this embodiment, the bypass passage 34 and the downstream section 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drain passage 27 are substantially the same, while the collection passage 32 and the downstream section 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the collection passage 32 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drain passage 27 are different. With this configuration, when the filter 43 of the collector 33 is clogged, the smoothness of the flow of cooling water flowing from the bypass passage 34 to the downstream section 27B of the drain passage 27 can be improved, and the smoothness of the flow of exhaust gas flowing back from the downstream section 27B of the drain passage 27 to the bypass passage 34 can be improved. Therefore, the effect of suppressing the backflow of cooling water or exhaust gas into the collection passage 32 can be enhanced, and the effect of suppressing the stirring up of fine particles accumulated in the filter 43 can be enhanced.

[0083] Furthermore, 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 to the confluence section 36 is downward and vertical, the downstream section 27B of the drainage passage 27 is arranged such that the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drainage passage 27 is downward and approximately vertical, and the collection passage 32 is arranged such that the flow direction of the cooling water flowing from the collection passage 32 to the confluence section 36 is not vertical. With this configuration, the smoothness of the flow of cooling water from the bypass passage 34 to the downstream section 27B of the drainage passage 27 can be further improved when the filter 43 of the collector 33 is clogged. Therefore, the effect of suppressing backflow of cooling water into the collection passage 32 can be further enhanced.

[0084] Furthermore, at the confluence section 36, the collection passage 32 and the bypass passage 34 intersect at an acute angle. Therefore, when the filter 43 of the collector 33 is not clogged, the cooling water flowing out of the collector 33 can flow smoothly through the collection passage 32 to the downstream section 27B of the drainage passage 27. Also, when the filter 43 of the collector 33 is clogged, it is possible to prevent the cooling water that has flowed through the bypass passage 34 from flowing into the collection passage 32 from the outlet of the collection passage 32.

[0085] In the above embodiment, the upstream section 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 section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 are the same. The flow direction of the cooling water flowing from the upstream section 27A of the drainage passage 27 to the branch section 35 and the flow direction of the cooling water flowing from the branch section 35 to the collection passage 32 do not have to be exactly the same, and they may differ slightly to the extent that smooth flow of cooling water from the upstream section 27A of the drainage passage 27 to the collection passage 32 is ensured when the filter 43 of the collector 33 is not clogged.

[0086] Furthermore, in the above embodiment, the bypass passage 34 and the downstream section 27B of the drain passage 27 are arranged such that the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 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 confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drain passage 27 are not completely the same, but slightly different, as the extension direction of the upper end (drain hole 30) of the downstream section 27B of the drain passage 27 is slightly inclined with respect to the vertical. However, if the difference is of this magnitude, the smooth flow of cooling water from the bypass passage 34 to the downstream section 27B of the drain passage 27, and the smooth flow of exhaust gas from the downstream section 27B of the drain passage 27 to the bypass passage 34 can be ensured, so this magnitude of difference can be considered equivalent to the same. However, the extension direction of the upper end (drain hole 30) of the downstream section 27B of the drain passage 27 may be made vertical, and the flow direction of the cooling water flowing from the bypass passage 34 to the confluence section 36 and the flow direction of the cooling water flowing from the confluence section 36 to the downstream section 27B of the drain passage 27 may be made completely identical.

[0087] Furthermore, in the above embodiment, 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 to the branching portion 35 is downward and vertical, and specifically, the lower end of the upstream portion 27A of the drainage passage 27 extends vertically. The collection passage 32 is also arranged such that the flow direction of the cooling water flowing from the branching 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 also arranged such that the flow direction of the cooling water flowing from the bypass passage 34 to the confluence 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 perfectly vertical, and may be slightly inclined with respect to the vertical.

[0088] Furthermore, in the above embodiment, the micro-object collection device 31 was positioned to the left of the rear of the engine 2, but the micro-object collection device 31 may be positioned at other locations around the engine 2, such as to the right of the rear of the engine 2.

[0089] Furthermore, the power source of the outboard motor 1 is not limited to an engine; it may also be an electric motor. In addition, the cooling device of the present invention is not limited to outboard motors, but can also be installed on other types of ship propulsion systems such as inboard or outboard motors or inboard motors.

[0090] Furthermore, the present invention may be modified as appropriate, provided that it does not contradict the gist or idea of ​​the invention as can be read from the claims and the specification as a whole, and cooling devices for ship propulsion systems with such modifications are also included in the technical concept of the present invention. [Explanation of Symbols]

[0091] 1. Outboard motor (ship propulsion system) 2. Engine (power source) 21 Cooling device 27 Drain passage 27A Upstream section 27B Downstream 32 Collection passage 33 Collector 34 Bypass passage 35 Branching point 36. Confluence

Claims

[Claim 1] A cooling device for a ship's propulsion system, provided in the ship's propulsion system, which takes in water from outside the ship's propulsion system into the ship's propulsion system, cools the power source of the ship's propulsion system by circulating the taken-in water as cooling water around or inside the power source of the ship's propulsion system, and discharges the cooling water that has flowed around or inside the power source to the outside of the ship's propulsion system, A drainage passage for discharging cooling water that has flowed around or inside the power source to the outside of the ship's propulsion system, A collection passage interposed between the upstream and downstream sections of the drainage passage, connecting the upstream and downstream sections of the drainage passage, A collector is provided in the middle of the collection passage and collects fine particles contained in the cooling water that flows through the collection passage from the upstream part of the drainage passage to the downstream part of the drainage passage, A bypass passage is connected in parallel with the collection passage between the upstream and downstream sections of the drainage passage, The upstream portion of the drainage passage has a branching section where it branches into the collection passage and the bypass passage, The collection passage and the bypass passage are provided with a confluence section where they merge at the downstream end 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 cooling water flowing from the upstream portion of the drainage passage to the branching portion and the flow direction of cooling water flowing from the branching portion to the collection passage is smaller than the difference between the flow direction of cooling water flowing from the upstream portion of the drainage passage to the branching portion and the flow direction of cooling water flowing from the branching portion to the bypass passage. A cooling system for a ship's propulsion system, characterized in that the collection passage and the bypass passage intersect at an acute angle at the branching section.

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