Outboard motor

Abstract

To provide a suitable outboard motor equipped with a hydrogen engine. [Solution] The outboard motor 100 comprises a cowl 31 with an exhaust port 45 formed therein, a hydrogen-fueled engine 10, a drive shaft 21 driven by the engine 10, a propeller 24 connected to the drive shaft 21, a fan 52 that discharges gas from the inside of the cowl 31 to the outside through the exhaust port 45, a hydrogen sensor 70 that detects the hydrogen concentration inside the cowl 31, and a control device 90 that drives the fan 52 when the hydrogen concentration detected by the hydrogen sensor 70 is above a predetermined first threshold while the engine 10 is stopped.

Description

Technical Field

[0001] The present invention relates to an outboard motor.

Background Art

[0002] Conventionally, an outboard motor is known as a propulsion device attached to a ship (for example, see Patent Document 1). The outboard motor includes a propeller, an engine that drives the propeller, and a cowl that houses the engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, engines that use hydrogen as fuel (hereinafter also referred to as hydrogen engines) have been attracting attention for the purpose of reducing CO2 emissions and the like. Therefore, it is conceivable to use a hydrogen engine as the engine of an outboard motor.

[0005] An object of the present invention is to provide a suitable outboard motor equipped with a hydrogen engine.

Means for Solving the Problems

[0006] The outboard motor disclosed herein comprises a cowl having an exhaust port formed therein; an engine disposed inside the cowl and fueled by hydrogen; a drive shaft connected to the engine and driven by the engine; a propeller connected to the drive shaft; a fan disposed inside the cowl and for discharging gas from inside the cowl to the outside of the cowl through the exhaust port; a hydrogen sensor disposed inside the cowl and for detecting the hydrogen concentration inside the cowl; and a control device that drives the fan when the hydrogen concentration detected by the hydrogen sensor exceeds a predetermined first threshold while the engine is stopped.

[0007] According to the outboard motor described above, when the engine is stopped, if the hydrogen concentration inside the cowling becomes high (i.e., exceeds a first threshold), the fan is activated. This causes the hydrogen inside the cowling to be discharged to the outside through the exhaust port. Therefore, the increase in hydrogen concentration inside the cowling when the engine is stopped is suppressed.

[0008] The engine may have a crankshaft, and the fan may be connected to the crankshaft and configured to rotate by the driving force of the crankshaft. The outboard motor may be connected to the crankshaft and include a starter motor that rotates the crankshaft. The control device may be configured to drive the fan by driving the starter motor.

[0009] With the above configuration, the fan is connected to the crankshaft, so the fan is driven when the engine is running. When the engine is running, hydrogen can be discharged from inside the cowl to the outside, and airflow is generated inside the cowl, which can cool the engine. On the other hand, when the engine is stopped, the fan can be driven by driving the starter motor. With the above configuration, the fan used to cool the engine while it is running can be used as a fan to forcibly discharge hydrogen from the cowl when the engine is stopped.

[0010] The aforementioned fan may be an electric fan.

[0011] This makes it easy to control the fan.

[0012] The hydrogen sensor may be positioned above the engine when the drive shaft extends vertically.

[0013] Since hydrogen is a relatively light gas, it tends to accumulate in the upper part of the cowl. With the above configuration, the hydrogen sensor is positioned relatively high. Therefore, it can accurately detect the hydrogen concentration inside the cowl.

[0014] The outboard motor may comprise an outboard motor body having at least the cowling, the engine, the drive shaft, the propeller, the fan, and the hydrogen sensor, and a tilt shaft that supports the outboard motor body so as to be rotatable forward and backward. The hydrogen sensor may be positioned behind a position midway between the front and rear ends of the cowling when the drive shaft extends vertically.

[0015] When a vessel is docked, the outboard motor may be tilted forward. In this case, the portion of the cowl that was behind the midpoint moves upward as the outboard motor rotates. With the above configuration, when the outboard motor is tilted forward, the hydrogen sensor is kept at a relatively high position inside the cowl. Therefore, even when the outboard motor is tilted forward, the hydrogen concentration inside the cowl can be detected accurately.

[0016] The exhaust port may be formed above the engine when the drive shaft extends vertically.

[0017] Since hydrogen is a relatively light gas, it tends to accumulate in the upper part of the cowl. With the above configuration, the hydrogen inside the cowl can be effectively discharged through the exhaust port.

[0018] The engine may include a crankcase supporting a crankshaft, a cylinder body connected to the crankcase, a cylinder head connected to the cylinder body, and a cylinder head cover connected to the cylinder head. The outboard motor may include a gas passage having an inlet connected to the crankcase, the cylinder body, the cylinder head, or the cylinder head cover, and an outlet opening toward the inside of the cowl. The outboard motor may include an electric valve provided in the gas passage.

[0019] In hydrogen-fueled engines, hydrogen can accumulate inside the crankcase, cylinder body, cylinder head, or cylinder head cover (hereinafter referred to as "inside the engine"). With the above configuration, by opening an electric valve, the hydrogen inside the engine can be discharged into the cowl through a gas passage. The hydrogen inside the cowl is then forcibly discharged by a fan, as described above. Therefore, with the above configuration, the hydrogen inside the engine can be forcibly discharged to the outside of the cowl.

[0020] The outboard motor may include a propeller shaft connected to the propeller, and a clutch connected to the drive shaft and the propeller shaft. The control device may be electrically connected to the electric valve and configured to close the electric valve when the clutch is engaged and the engine is running, and to open the electric valve when the clutch is disengaged or the engine is stopped.

[0021] This allows hydrogen inside the engine to be discharged to the outside of the engine while the engine is stopped or idling.

[0022] The outboard motor may include a propeller shaft connected to the propeller. The control device may be electrically connected to the electric valve and configured to execute control to close the electric valve when the rotational speed of the propeller shaft is equal to or higher than a predetermined first speed, and to open the electric valve when the rotational speed of the propeller shaft is lower than the first speed.

[0023] By doing this, by opening the electric valve at an extremely low speed of the engine, hydrogen inside the engine can be discharged to the outside of the engine.

[0024] The outboard motor may include a starter motor connected to the crankshaft and configured to rotate the crankshaft. The control device may be configured to open the electric valve and drive the starter motor for a predetermined period of time before starting the engine or after stopping the operation of the engine.

[0025] By doing this, by performing cranking before starting the engine or after stopping the operation of the engine, hydrogen inside the engine can be discharged to the outside of the engine.

[0026] The control device may be configured to prohibit starting of the engine when the hydrogen concentration detected by the hydrogen sensor is equal to or higher than a predetermined second threshold value.

[0027] By doing this, it is possible to prevent starting the engine in a state where the hydrogen concentration inside the cowl is relatively high.

Advantages of the Invention

[0028] According to the present invention, it is possible to provide a suitable outboard motor including an engine using hydrogen as fuel.

Brief Description of the Drawings

[0029] [Figure 1] FIG. 1 is a plan view of a ship according to an embodiment. [Figure 2]Figure 2 is a side view of an outboard motor according to one embodiment. [Figure 3] Figure 3 is a perspective view of the upper part of the cowling of the outboard motor. [Figure 4] Figure 4 is a cross-sectional view of the cowl along line IV-IV in Figure 3. [Figure 5] Figure 5 is a perspective view of the cowl with the first case removed. [Figure 6] Figure 6 is a perspective view of the exhaust duct when the upper duct case has been removed from the lower duct case. [Figure 7] Figure 7 is a schematic front view showing the upper part of the engine in an outboard motor. [Figure 8] Figure 8 is a side view showing the outboard motor body before and after tilting. [Figure 9] Figure 9 is a perspective view of the engine. [Figure 10] Figure 10 is a plan view of the engine. [Figure 11] Figure 11 is a block diagram of the outboard motor's control system. [Figure 12] Figure 12 is a perspective view of a fan according to another embodiment. [Modes for carrying out the invention]

[0030] The following describes an embodiment of the outboard motor with reference to the drawings. Figure 1 is a schematic plan view of a vessel 120 equipped with an outboard motor 100. The vessel 120 comprises a hull 110 and an outboard motor 100. The hull 110 has a hydrogen tank 112 filled with hydrogen. The hydrogen tank 112 is housed inside the hull 110. The outboard motor 100 is mounted at the rear of the hull 110.

[0031] Figure 2 is a side view of the outboard motor 100. As shown in Figure 2, the outboard motor 100 has an outboard motor body 101 and a bracket 102. The outboard motor body 101 is attached to the stern 111 of the hull 110 via the bracket 102. The bracket 102 is provided with a tilt shaft 102a that extends in the left-right direction. The outboard motor body 101 is rotatably supported on the tilt shaft 102a. The tilt shaft 102a supports the outboard motor body 101 so that it can rotate forward and backward. By rotating the outboard motor body 101 around the tilt shaft 102a, the inclination of the outboard motor body 101 relative to the hull 110 can be changed. The outboard motor body 101 is tiltable relative to the hull 110.

[0032] Figure 2 shows the outboard motor 100 when the drive shaft 21, which will be described later, extends vertically. In other words, Figure 2 shows the state when the outboard motor body 101 is not tilted. When the outboard motor body 101 rotates forward around the tilt shaft 102a (in other words, rotates counterclockwise in Figure 2), the outboard motor body 101 tilts forward. In this case, the drive shaft 21 extends backward from the engine 10 (here, backward includes both backward and downward, or backward and upward). Conversely, when the outboard motor body 101 rotates backward around the tilt shaft 102a (in other words, rotates clockwise in Figure 2), the outboard motor body 101 tilts backward. In this case, the drive shaft 21 extends forward and downward from the engine 10.

[0033] In the diagram, F, Rr, L, R, Z1, and Z2 indicate the forward, rear, left, right, upper, and lower directions of the outboard motor body 101 when the outboard motor body 101 is not tilted relative to the hull 110.

[0034] The outboard motor body 101 comprises an engine 10 consisting of an internal combustion engine, a drive shaft 21, a gear unit 22, a propeller shaft 23, and a propeller 24. The outboard motor body 101 also comprises a cowl 31, an upper case 32, and a lower case 33.

[0035] Engine 10 is a hydrogen-fueled engine. Engine 10 is housed in cowling 31; that is, engine 10 is located inside cowling 31. Details of engine 10 will be described later.

[0036] The drive shaft 21 is connected to the engine 10. The drive shaft 21 rotates when driven by the engine 10. The drive shaft 21 extends downward from the engine 10. The drive shaft 21 is housed in the cowl 31, the upper case 32, and the lower case 33.

[0037] The gear unit 22 is connected to the lower end of the drive shaft 21 and the front end of the propeller shaft 23. The driving force of the drive shaft 21 is transmitted to the propeller shaft 23 via the gear unit 22. Although not shown in the diagram, the gear unit 22 includes multiple gears. The drive shaft 21 and the propeller shaft 23 are connected via the gear unit 22. The gear unit 22 also includes a clutch 25. When the clutch 25 is engaged, the driving force of the drive shaft 21 is transmitted to the propeller shaft 23 via the clutch 25. When the clutch 25 is disengaged, the driving force of the drive shaft 21 is not transmitted to the propeller shaft 23.

[0038] The propeller shaft 23 extends rearward from the gear unit 22. The propeller 24 is connected to the rear end of the propeller shaft 23. As the propeller shaft 23 rotates, the propeller 24 rotates. The propeller shaft 23 and propeller 24 are located below the engine 10. The driving force of the engine 10 is transmitted to the propeller 24 via the drive shaft 21, the gear unit 22, and the propeller shaft 23. The propeller 24 rotates in response to the driving force of the engine 10. As the propeller 24 rotates in the water, it generates thrust that propels the vessel 120.

[0039] The upper case 32 is located below the cowl 31, and the lower case 33 is located below the upper case 32. The cowl 31, upper case 32, and lower case 33 constitute the housing of the outboard motor body 101. The materials of the cowl 31, upper case 32, and lower case 33 are not particularly limited, but in this embodiment, the cowl 31 is made of resin, and the upper case 32 and lower case 33 are made of metal such as aluminum. The lower case 33 houses the lower part of the drive shaft 21, the gear unit 22, and the propeller shaft 23. The propeller 24 is located behind the lower case 33.

[0040] Figure 3 is a perspective view of the upper portion of the cowl 31. The cowl 31 has a first case 41, a second case 42, and a third case 43. The first case 41 is assembled to the second case 42 and is positioned above the second case 42. The second case 42 is assembled to the third case 43 and is positioned above the third case 43.

[0041] The cowl 31 has an intake port 46 that connects the inside and outside of the cowl 31. Here, the intake port 46 is formed on the left side 31L and the right side 31R of the cowl 31. Figure 4 is a cross-sectional view of the cowl 31 taken along line IV-IV of Figure 3. As shown in Figure 4, the upper left portion 42LU of the second case 42 is tilted to the right. The upper left portion 42LU of the second case 42 extends upward and to the right. The lower left edge 41LD of the first case 41 is spaced to the left of the upper left portion 42LU of the second case 42. This gap between the lower left edge 41LD of the first case 41 and the upper left portion 42LU of the second case 42 forms the left intake port 46. Similarly, the upper right portion 42RU of the second case 42 is tilted to the left. The upper right portion 42RU of the second case 42 extends upward and to the left. The lower right edge 41RD of the first case 41 is spaced to the right of the upper right portion 42RU of the second case 42. This gap between the lower right edge 41RD of the first case 41 and the upper right portion 42RU of the second case 42 forms the right-side air intake 46. However, the configuration of the air intake 46 described here is merely an example. The position, orientation, shape, and dimensions of the air intake 46 can be changed as appropriate.

[0042] As shown in Figure 3, the cowl 31 has an exhaust port 45 that connects the inside and outside of the cowl 31. Here, the exhaust port 45 is formed in the upper part 31U of the cowl 31. The exhaust port 45 is formed in the first case 41 and is located at a relatively high position. The exhaust port 45 opens forward. When viewed from the front, the exhaust port 45 is formed in a horizontally elongated rectangular shape. However, the configuration of the exhaust port 45 described here is merely an example. The position, orientation, shape, and dimensions of the exhaust port 45 are not particularly limited.

[0043] Figure 5 is a perspective view of the cowl 31 when the first case 41 is removed. As shown in Figure 5, the cowl 31 is provided with an exhaust duct 48. The exhaust duct 48 is located between the first case 31 and the second case 42. The exhaust duct 48 has a lower duct case 48A fixed to the second case 42 and an upper duct case 48B fixed to the lower duct case 48A. Figure 6 is a perspective view of the exhaust duct 48 when the upper duct case 48B is removed from the lower duct case 48A. As shown in Figure 6, the second case 42 has an opening 42a that penetrates in the vertical direction. The lower duct case 48A has a duct inlet 48a that opens downwards. The duct inlet 48a is connected to the opening 42a of the second case 42. As shown in Figure 5, the upper duct case 48B has a duct outlet 48b that opens forwards. The duct outlet 48b is connected to the exhaust port 45 (see Figure 3) formed in the first case 41. The upper duct case 48B and the lower duct case 48A divide the flow path from the duct inlet 48a to the duct outlet 48b (see arrow 48F in Figure 6).

[0044] Figure 7 is a schematic front view showing the upper part of the engine 10. As shown in Figure 7, the outboard motor body 101 comprises a rotating shaft 51 connected to the crankshaft 11 of the engine 10 and a fan 52 connected to the rotating shaft 51. Reference numeral 11c represents the central axis of the crankshaft 11. The rotating shaft 51 is connected to the crankshaft 11 via a reduction gear 55. The form of the fan 52 is not particularly limited, but the fan 52 in this embodiment is a centrifugal blower that draws in air along the axial direction and sends air in a direction perpendicular to the axial direction. Here, the fan 52 is a cylindrical multi-blade fan having multiple blades. A fan casing 53 is provided around the fan 52. The fan casing 53 surrounds the fan 52. The fan casing 53 has a cylindrical portion 53A that surrounds the fan 52 and an upper plate portion 53B that closes the top of the cylindrical portion 53A. The upper plate portion 53B has an opening 53a that penetrates vertically. The opening 53a is connected to the opening 42a of the second case 42 (see Figure 6).

[0045] When the rotating shaft 51 rotates, the fan 52 rotates. When the fan 52 rotates, air is drawn in from the outside to the inside of the cowl 31 through the intake port 46 (see Figures 3 and 4). Also, when the fan 52 rotates, the air inside the cowl 31 is sent to the duct inlet 48a of the exhaust duct 48 through the opening 53a of the fan casing 53 and the opening 42a of the second case 42. This air flows from the duct inlet 48a into the exhaust duct 48, circulates inside the exhaust duct 48, and reaches the duct outlet 48b (see arrow 48F in Figure 6). The air that has passed through the duct outlet 48b is discharged to the outside of the cowl 31 through the exhaust port 45 of the cowl 31. In this embodiment, the rotation of the fan 52 creates an airflow that circulates inside the cowl 31. In other words, air is drawn in through the intake port 46 formed on the top of the cowl 31, flows downwards inside the cowl 31, then rises towards the exhaust duct 48, and is discharged through the exhaust duct 48 and out of the exhaust port 45.

[0046] As shown in Figure 7, the outboard motor body 101 is equipped with a starter motor 60. A gear 63 is fixed to the output shaft 62 of the starter motor 60. Gear 63 meshes with gear 61 fixed to the rotating shaft 51. The starter motor 60 is connected to the rotating shaft 51 via gears 63 and 61. As mentioned above, the rotating shaft 51 is connected to the crankshaft 11 of the engine 10. Therefore, the starter motor 60 is connected to the crankshaft 11 via the rotating shaft 51. When the starter motor 60 is driven, the driving force of the starter motor 60 is transmitted to the crankshaft 11 through the rotating shaft 51. By driving the starter motor 60, the crankshaft 11 is rotated, and fuel is injected in conjunction with the rotation of the crankshaft 11, the engine 10 can be started. On the other hand, by driving the starter motor 60 and prohibiting fuel injection, the fan 52 can be rotated while the engine 10 is stopped.

[0047] As shown in Figure 2, the outboard motor body 101 is equipped with a hydrogen sensor 70. The hydrogen sensor 70 is located inside the cowl 31. The installation position of the hydrogen sensor 70 can be selected as appropriate. The hydrogen sensor 70 may be located inside the first case 41 of the cowl 31, or it may be located inside the second case 42. The hydrogen sensor 70 detects the hydrogen concentration inside the cowl 31. In this embodiment, the hydrogen sensor 70 is located above the engine 10 when the outboard motor body 101 is not tilted. In other words, the hydrogen sensor 70 is located above the engine 10 when the drive shaft 21 extends vertically.

[0048] In Figure 2, the line L1 is a vertical line passing through the midpoint between the front and rear ends of the cowl 31 when the drive shaft 21 extends vertically. In this embodiment, the hydrogen sensor 70 is positioned behind the line L1. Unless otherwise specified below, the midpoint between the front and rear ends of the cowl 31 when the drive shaft 21 extends vertically will be referred to as the midpoint in the longitudinal direction of the cowl 31. The hydrogen sensor 70 is positioned behind the midpoint in the longitudinal direction of the cowl 31. Therefore, as shown in Figure 8, even when the outboard motor body 101 is tilted forward, the position of the hydrogen sensor 70 is maintained at a relatively high position inside the cowl 31.

[0049] Figure 9 is a perspective view of the engine 10. Figure 10 is a plan view of the engine 10. The engine 10 according to this embodiment is a so-called V8 engine. The engine 10 has a pair of four cylinders arranged vertically on the left and right sides. As shown in Figure 10, the engine 10 has a crankcase 12 that supports the crankshaft 11, a cylinder body 13 connected to the crankcase 12, a cylinder head 14 connected to the cylinder body 13, and a cylinder head cover 15 connected to the cylinder head 14. An intake pipe 16 and an exhaust pipe 17 are connected to the cylinder head 14.

[0050] As shown in Figure 9, the engine 10 has a fuel injector 18. The fuel injector 18 is mounted on the cylinder head 14. The fuel injector 18 includes a delivery pipe 18A and an injector (not shown) connected to the delivery pipe 18A. The injector is configured to inject hydrogen as fuel into the cylinder body 13. A hydrogen supply pipe (hereinafter referred to as hydrogen pipe) 19 is connected to the delivery pipe 18A. The delivery pipe 18A and the injector are located behind the midpoint in the longitudinal direction of the cowl 31. Also, much of the hydrogen pipe 19 is located behind the midpoint in the longitudinal direction of the cowl 31. As mentioned above, the hydrogen sensor 70 is located above the engine 10 and behind the midpoint in the longitudinal direction of the cowl 31. Therefore, the hydrogen sensor 70 is located above the portion of the engine 10 where the delivery pipe 18A and the injector are located. Also, the hydrogen sensor 70 is located above the portion of the engine 10 where the hydrogen pipe 19 is concentrated.

[0051] As schematically shown in Figure 10, the engine 10 is connected to a gas passage 80 that communicates the inside and outside of the engine 10. In this embodiment, the gas passage 80 has an inlet 80a connected to the cylinder head cover 15 and an outlet 80b that opens toward the inside of the cowl 31. The gas passage 80 is not limited in its configuration and only needs to be a passage that communicates the inside and outside of the engine 10 so that hydrogen can be discharged from the inside of the engine 10 to the outside. The gas passage 80 may be a dedicated passage for discharging hydrogen from the inside of the engine 10, or it may be an existing passage used for other purposes that is partially utilized. For example, as shown in Figure 10, a passage 85 that supplies engine oil to the inside of the engine 10 may be partially utilized. Note that an oil filler cap 86 is fitted into the passage 85 that supplies engine oil.

[0052] The material of the gas passage 80 is not particularly limited. Part or all of the gas passage 80 may be a rigid pipe or a flexible hose. The gas passage 80 may be any passage that connects the inside of the engine 10 to the inside of the cowl 31. Here, the inlet 80a of the gas passage 80 is connected to the cylinder head cover 15, but the inlet 80a may be connected to the crankcase 12, cylinder body 13, or cylinder head 14. It is preferable that the outlet 80b of the gas passage 80 is located near the duct inlet 48a of the exhaust duct 48 so that hydrogen from inside the engine 10 can be quickly discharged to the outside of the cowl 31. The inlet 80a of the gas passage 80 may be located outside the exhaust duct 48, or it may be located inside the exhaust duct 48. The inlet 80a of the gas passage 80 may be connected to the exhaust duct 48. When the inlet 80a is connected to the exhaust duct 48, hydrogen can be directly supplied from the gas passage 80 to the exhaust duct 48. Therefore, hydrogen inside the engine 10 can be quickly discharged to the outside of the cowl 31.

[0053] A solenoid valve 81 is provided in the gas passage 80. The solenoid valve 81 is an example of an electric valve that opens and closes in response to an electrical signal. The solenoid valve 81 is configured to open and close the gas passage 80.

[0054] As shown in Figure 11, the outboard motor 100 is equipped with a control device 90. Although not shown in the figure, the control device 90 is composed of a microcomputer with a CPU, RAM, ROM, and a communication interface. The control device 90 is electrically connected to the hydrogen sensor 70 and receives signals from the hydrogen sensor 70. The hydrogen concentration information detected by the hydrogen sensor 70 is input to the control device 90. The outboard motor 100 is equipped with a rotational speed sensor 72 that detects the rotational speed of the crankshaft 11 of the engine 10 (hereinafter also referred to as engine rotational speed). The control device 90 is electrically connected to the rotational speed sensor 72 and receives signals from the rotational speed sensor 72. Based on the engine rotational speed, the control device 90 can detect whether the engine 10 is stopped or not. The control device 90 is also electrically connected to the starter motor 60, the fuel injector 18 (specifically, the injector of the fuel injector 18), and the solenoid valve 81. The control device 90 is configured to control the starter motor 60, the fuel injector 18, and the solenoid valve 81. The control device 90 controls the output of the engine 10 by controlling the fuel injection device 18.

[0055] When the engine 10 is stopped, the control device 90 executes a control to drive the fan 52 when the hydrogen concentration detected by the hydrogen sensor 70 exceeds a predetermined first threshold. As the fan 52 rotates, the hydrogen inside the cowl 31 is discharged to the outside of the cowl 31 through the exhaust port 45 along with air. This prevents the hydrogen concentration inside the cowl 31 from rising. The first threshold can be set as appropriate, for example, to 2%. The control device 90 can rotate the fan 52 while the engine 10 is stopped by driving the starter motor 60 and prohibiting fuel injection from the fuel injector 18. The control device 90 can discharge hydrogen from inside the cowl 31 to the outside while the engine 10 is stopped. The fan 52 may be driven for a predetermined time, or until the hydrogen concentration detected by the hydrogen sensor 70 falls below a predetermined threshold.

[0056] Furthermore, the control device 90 is configured to execute a control that prohibits starting the engine 10 when the hydrogen concentration detected by the hydrogen sensor 70 is above a predetermined second threshold. In other words, if the hydrogen concentration inside the cowl 31 is high, the control device 90 will not start the engine 10 by not driving the starter motor 60 or not injecting fuel from the fuel injector 18, even if the ship's crew attempts to start the engine 10.

[0057] Furthermore, the control device 90 is capable of various controls, such as opening and closing the solenoid valve 81 (see Figure 10) of the gas passage 80 according to the operating state of the outboard motor 100, as described below.

[0058] The control device 90 can control the solenoid valve 81 to close when the engine 10 is operating normally, and to open when the engine 10 is stopped or idling. Specifically, the control device 90 closes the solenoid valve 81 when the clutch 25 (see Figure 2) is engaged and the engine 10 is running. The control device 90 opens the solenoid valve 81 when the clutch 25 is disengaged or when the engine 10 is stopped. By performing this control, hydrogen inside the engine 10 can be discharged to the outside of the engine 10 when the engine 10 is stopped or idling.

[0059] Furthermore, the control device 90 may open the solenoid valve 81 even when the engine 10 is running if the rotational speed of the propeller shaft 23 is very low. That is, the control device 90 may open the solenoid valve 81 to discharge hydrogen from inside the engine 10 to the outside when the outboard motor 100 is operating at an extremely low speed. Specifically, the control device 90 may be capable of performing control such as closing the solenoid valve 81 when the rotational speed of the propeller shaft 23 is equal to or greater than a predetermined first speed, and opening the solenoid valve 81 when the rotational speed of the propeller shaft 23 is less than the first speed. The rotational speed of the propeller shaft 23 can be calculated based on the rotational speed of the crankshaft 11 detected by the rotational speed sensor 72. The control device 90 may indirectly detect the rotational speed of the propeller shaft 23. Alternatively, the outboard motor body 101 may be equipped with a sensor that detects the rotational speed of the propeller shaft 23, and the control device 90 may be configured to directly detect the rotational speed of the propeller shaft 23 using this sensor. Although not particularly limited, the extremely low-speed operation of the outboard motor 100 is performed, for example, when the vessel 120 is docked. Whether or not the vessel 120 is docked can be detected, for example, by using GPS. Therefore, the control device 90 may execute a control to open the solenoid valve 81 when the vessel 120 is docked and the outboard motor 100 is operating at an extremely low speed.

[0060] The control device 90 may be capable of executing a control that opens the solenoid valve 81 and drives the starter motor 60 for a predetermined period of time before starting the engine 10. This control allows hydrogen inside the engine 10 to be discharged to the outside of the engine 10 before it starts. The control device 90 may also be capable of executing a control that opens the solenoid valve 81 and drives the starter motor 60 for a predetermined period of time after the engine 10 has stopped running. This control allows hydrogen inside the engine 10 to be discharged to the outside of the engine 10 after it has stopped running. Along with the discharge of hydrogen, water vapor in the combustion chamber will also be discharged to the outside of the engine 10. Therefore, this control can suppress the generation of rust inside the engine 10.

[0061] Next, we will describe the various effects brought about by this embodiment.

[0062] As described above, the outboard motor 100 according to this embodiment includes a cowl 31 with an exhaust port 45 formed therein, a fan 52 that discharges gas from inside the cowl 31 to the outside of the cowl 31 through the exhaust port 45, a hydrogen sensor 70 that detects the hydrogen concentration inside the cowl 31, and a control device 90 that drives the fan 52 when the hydrogen concentration detected by the hydrogen sensor 70 exceeds a first threshold when the engine 10 is stopped. According to this embodiment, when the engine 10 is stopped, if the hydrogen concentration inside the cowl 31 becomes high (i.e., exceeds the first threshold), the fan 52 is driven. As a result, the hydrogen inside the cowl 31 is discharged to the outside of the cowl 31 through the exhaust port 45. Therefore, according to this embodiment, the increase in the hydrogen concentration inside the cowl 31 when the engine 10 is stopped is suppressed.

[0063] In this embodiment, since the fan 52 is connected to the crankshaft 11 of the engine 10, the fan 52 is driven while the engine 10 is running. Since airflow is generated inside the cowl 31 while the engine 10 is running, the engine 10 can be cooled. On the other hand, when the engine 10 is stopped, the fan 52 can be driven by driving the starter motor 60. In this embodiment, the fan 52 used to cool the engine 10 can be used as a fan to forcibly discharge hydrogen from the cowl 31 when the engine 10 is stopped.

[0064] In this embodiment, the hydrogen sensor 70 is positioned above the engine 10 when the outboard motor body 101 is in a position where the drive shaft 21 extends vertically (see Figure 2). Since hydrogen is a relatively light gas, it tends to accumulate in the upper part of the inside of the cowl 31. In this embodiment, since the hydrogen sensor 70 is positioned at a relatively high position, the hydrogen concentration inside the cowl 31 can be detected well.

[0065] For example, when the vessel 120 is docked, the outboard motor body 101 may be tilted forward, as shown by the dashed line in Figure 8. In this case, the portion of the cowl 31 that was behind the midpoint in the longitudinal direction (see straight line L1 in Figure 8) moves upward as the outboard motor body 101 is tilted. According to this embodiment, the hydrogen sensor 70 is positioned behind the midpoint between the front and rear ends of the cowl 31 when the drive shaft 21 extends vertically. Therefore, when the outboard motor body 101 is tilted forward, the position of the hydrogen sensor 70 is maintained at a relatively high position within the cowl 31. Consequently, even when the outboard motor body 101 is tilted forward, such as when docking, the hydrogen concentration inside the cowl 31 can be detected well.

[0066] As mentioned above, since hydrogen is a relatively light gas, it tends to accumulate in the upper part of the cowl 31. In this embodiment, the exhaust port 45 of the cowl 31 is formed above the engine 10 when the drive shaft 21 extends vertically. The exhaust port 45 is formed at a relatively high position. Therefore, hydrogen in the cowl 31 can be effectively discharged from the exhaust port 45.

[0067] The engine 10 according to this embodiment is a hydrogen-fueled engine. Hydrogen may accumulate inside the crankcase 12, cylinder body 13, cylinder head 14, or cylinder head cover 15 (i.e., inside the engine) when the engine 10 is stopped. Hydrogen may also accumulate inside the engine when idling. The outboard motor 100 according to this embodiment includes a gas passage 80 having an inlet 80a connected to the cylinder head cover 15 and an outlet 80b opening toward the inside of the cowl 31, and a solenoid valve 81 provided in the gas passage 80 (see Figure 10). By opening the solenoid valve 81, hydrogen inside the engine 10 can be discharged into the cowl 31 through the gas passage 80. The hydrogen inside the cowl 31 is forcibly discharged by the fan 65 as described above. Therefore, according to this embodiment, hydrogen inside the engine 10 can be forcibly discharged to the outside of the cowl 31.

[0068] According to this embodiment, the control device 90 can perform control to close the solenoid valve 81 when the clutch 25 is engaged and the engine 10 is running, and to open the solenoid valve 81 when the clutch 25 is disengaged or the engine 10 is stopped. By performing such control, hydrogen inside the engine 10 can be discharged to the outside of the engine 10 while the engine 10 is stopped or idling.

[0069] According to this embodiment, the control device 90 can perform control such as closing the solenoid valve 81 when the rotational speed of the propeller shaft 23 is equal to or greater than the first speed, and opening the solenoid valve 81 when the rotational speed of the propeller shaft 23 is less than the first speed. By performing such control, for example, during extremely low-speed operation when docking, hydrogen inside the engine 10 can be discharged to the outside of the engine 10.

[0070] According to this embodiment, the control device 90 can perform control to open the solenoid valve 81 and drive the starter motor 60 for a predetermined period of time before starting or after stopping the engine 10. By performing such control, hydrogen inside the engine 10 can be discharged to the outside of the engine 10 before starting or after stopping the engine 10.

[0071] According to this embodiment, the control device 90 can perform control to prohibit the starting of the engine 10 when the hydrogen concentration detected by the hydrogen sensor 70 is equal to or greater than a predetermined second threshold. Therefore, it is possible to prevent the engine 10 from being started when the hydrogen concentration inside the cowl 31 is relatively high.

[0072] The above describes one embodiment of an outboard motor, but this embodiment is merely one example. Many other embodiments are possible. Next, we will describe examples of other embodiments.

[0073] In the above embodiment, the fan 65 used to cool the engine 10 was repurposed as a fan that discharges hydrogen from the inside of the cowl 31 to the outside (hereinafter referred to as the hydrogen discharge fan). In the above embodiment, the hydrogen discharge fan is a fan 65 driven by the crankshaft 11 of the engine 10. However, the hydrogen discharge fan may be a dedicated fan. An electric fan may also be used as the hydrogen discharge fan. The hydrogen discharge fan can be installed at any position inside the cowl 31. For example, as shown in Figure 12, an electric fan 66 may be installed inside the exhaust duct 48 as the hydrogen discharge fan. In this embodiment as well, by driving the electric fan 66, hydrogen inside the cowl 31 can be discharged to the outside of the cowl 31 through the exhaust port 45. The electric fan 66 is electrically connected to the control device 90 and controlled by the control device 90. In this embodiment as well, various controls similar to those in the above embodiment can be performed.

[0074] In the above embodiment, an exhaust duct 48 (see Figure 5) is connected to the exhaust port 45 of the cowl 31, but the exhaust duct 48 is not necessarily required. The outboard motor 100 does not need to have an exhaust duct 48 as long as gas can be smoothly discharged from the exhaust port 45.

[0075] Engine 10 is not limited to a multi-cylinder engine; it may also be a single-cylinder engine. [Explanation of Symbols]

[0076] 10 Engines 11 Crank Axle 12 Crankcase 13 Cylinder body 14 Cylinder head 15 Cylinder head cover 21 drive shafts 23 Propeller shaft 24 propellers 25 Clutch 31 Cowl 45 Exhaust vent 52 Fans 60 Starter motor 66 Electric Fan 70 Hydrogen Sensor 80 Gas passage 80a Entrance to the gas passage 80b Gas passage outlet 81 Solenoid valve (electric valve) 90 Control device 100 Outboard motors 101 Outboard motor body 102a Tilt axis

Claims

1. A cowl with an exhaust port formed on it, An engine that uses hydrogen as fuel is located inside the aforementioned cowl, A drive shaft connected to the engine and driven by the engine, A propeller connected to the aforementioned drive shaft, A fan is positioned inside the cowl and discharges the gas inside the cowl to the outside of the cowl through the exhaust port. A hydrogen sensor is placed inside the cowl to detect the hydrogen concentration inside the cowl, When the engine is stopped, if the hydrogen concentration detected by the hydrogen sensor exceeds a predetermined first threshold, the control device drives the fan. An outboard motor equipped with [a specific feature / equipment].

2. The engine has a crankshaft, The fan is connected to the crankshaft and is configured to rotate by receiving the driving force of the crankshaft. It is equipped with a starter motor connected to the crankshaft and which rotates the crankshaft, The outboard motor according to claim 1, wherein the control device is configured to drive the fan by driving the starter motor.

3. The outboard motor according to claim 1, wherein the fan is an electric fan.

4. The outboard motor according to claim 1, wherein the hydrogen sensor is positioned above the engine when the drive shaft extends vertically.

5. An outboard motor body having at least the cowl, the engine, the drive shaft, the propeller, the fan, and the hydrogen sensor, The outboard motor body is supported by a tilt shaft that allows it to rotate forward and backward, The outboard motor according to claim 4, wherein the hydrogen sensor is positioned behind a position midway between the front and rear ends of the cowl when the drive shaft extends vertically.

6. The outboard motor according to claim 1, wherein the exhaust port is formed above the engine when the drive shaft extends in the vertical direction.

7. The engine comprises a crankcase that supports the crankshaft, a cylinder body connected to the crankcase, a cylinder head connected to the cylinder body, and a cylinder head cover connected to the cylinder head. A gas passage having an inlet connected to the crankcase, the cylinder body, the cylinder head, or the cylinder head cover, and an outlet opening toward the interior of the cowl, The outboard motor according to claim 1, further comprising an electric valve provided in the gas passage.

8. A propeller shaft connected to the aforementioned propeller, The drive shaft and the propeller shaft are connected by a clutch, The outboard motor according to claim 7, wherein the control device is electrically connected to the electric valve and is configured to perform control to close the electric valve when the clutch is engaged and the engine is running, and to open the electric valve when the clutch is disengaged or the engine is stopped.

9. The propeller shaft is connected to the aforementioned propeller, The outboard motor according to claim 7, wherein the control device is electrically connected to the electric valve and is configured to close the electric valve when the rotational speed of the propeller shaft is equal to or greater than a predetermined first speed, and to open the electric valve when the rotational speed of the propeller shaft is less than the first speed.

10. It is equipped with a starter motor connected to the crankshaft and which rotates the crankshaft, The outboard motor according to claim 7, wherein the control device is configured to open the electric valve and drive the starter motor for a predetermined period of time before the engine is started or after it has stopped running.

11. The outboard motor according to claim 1, wherein the control device is configured to prohibit starting the engine when the hydrogen concentration detected by the hydrogen sensor is equal to or greater than a predetermined second threshold.

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