MARINE PROPULSION SYSTEM ENABLING MOVEMENT OF MARINE VESSEL IN LATERAL DIRECTION, AND CONTROL METHOD THEREOF

Abstract

A marine propulsion system includes first propulsion devices located at a stern of the hull, a second propulsion device located toward a bow of the hull, and a controller. To move the hull laterally, the controller is configured or programmed to steer the first propulsion device on a port side of the hull in a leftward turning direction, and fully steer the first propulsion device on a starboard side of the hull in a rightward turning direction; cause one of the first propulsion devices to generate a forward/rearward thrust and cause another one of the first propulsion devices to generate a rearward/forward thrust to position a point of action of a resultant force of the generated thrusts in front of a turning center of the hull; and generate with the second propulsion device a counter moment to cancel a yaw moment about the turning center generated by the resultant force.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No. 2023-130811, filed Aug. 10, 2023, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to marine propulsion system that enable movement of marine vessels in a lateral direction and control methods thereof.

2. Description of the Related Art

In a marine vessel including a plurality of, for example, two outboard motors at a stern, when a hull is moved in a lateral direction, the outboard motor on a port side is steered in a leftward turning direction and the outboard motor on a starboard side is steered in a rightward turning direction, thereby causing the outboard motor on the port side to generate forward or rearward thrust and causing the outboard motor on the starboard side to generate thrust in a direction opposite to the thrust generated by the outboard motor on the port side. At this time, a resultant force of the thrust generated by the outboard motor on the starboard side and the thrust generated by the outboard motor on the port side acts on the hull as a lateral movement force.

Meanwhile, in a marine vessel having a wide width such as a twin boat, a plurality of outboard motors may be provided at the stern while being spaced apart from each other. In this case, even when the outboard motor on the port side and the outboard motor on the starboard side are fully steered, a point of action of the resultant force may be in front of a turning center of the hull. As a result, a yaw moment about the turning center is generated by the resultant force, and the marine vessel rotates on its own axis in a yaw direction during lateral movement of the marine vessel.

Therefore, a technology in which the point of action of the resultant force of the thrusts generated when one outboard motor and the other outboard motor are steered is moved by changing an attachment angle of each outboard motor with respect to the hull, so that the point of action of the resultant force of the thrusts and the turning center of the hull coincide each other is known (see, for example, U.S. Pat. No. 10,202,179). According to this technology, no yaw moment about the turning center is generated by the resultant force of the thrusts, which makes it possible to prevent the marine vessel from rotating on its own axis in the yaw direction during the lateral movement of the marine vessel. In this technology, as illustrated in FIG. 12, in order to change an attachment angle of each of outboard motors 122 and 123 with respect to a hull 120, each of the outboard motors 122 and 123 is attached to the hull 120 via a wedge plate 124 or 125 for adjusting the attachment angle.

However, when each of the outboard motors 122 and 123 is attached to the hull 120 via the wedge plate 124 or 125, a steerable angle of the outboard motor in a direction opposite to a direction in which each of the outboard motors 122 and 123 is inclined by the wedge plate 124 or 125 decreases, which affects turning performance of the marine vessel. In addition, in a neutral state related to steering of each of the outboard motors 122 and 123, a rear side of each of the outboard motors 122 and 123 may protrude from an outer side of the hull 120, which may lead to an increase in resistance during navigation. Therefore, there is still room for improvement in achieving both prevention of rotation of the marine vessel on its own axis during lateral movement of the marine vessel and maintenance of navigation performance of the marine vessel.

SUMMARY OF THE INVENTION

Example embodiments of the present invention provide marine propulsion systems and control methods thereof, which both prevent rotation of marine vessels during lateral movement of the marine vessels and maintain the navigation performance of the marine vessels.

According to an example embodiment of the present invention, a marine propulsion system includes a plurality of first propulsion devices located at a stern of a hull and including at least a first propulsion device on a port side of the hull with respect to a center line extending in a front-rear direction of the hull, and a first propulsion device located on a starboard side of the hull with respect to the center line, a second propulsion device located toward a bow of the hull, and a controller configured or programmed, when moving the hull in a lateral direction, to fully steer in a leftward turning direction the first propulsion device on the port side, and fully steer in a rightward turning direction the first propulsion device on the starboard side so that the first propulsion device on the port side and the first propulsion device on the starboard side form an inverted V shape in plan view, cause the first propulsion device on the port side to generate a forward thrust or a rearward thrust and cause the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located in front of a turning center of the hull, and control the second propulsion device to generate another thrust to generate a counter yaw moment to cancel a yaw moment about the turning center generated by the lateral movement force.

With this configuration, when moving the hull in the lateral direction, in a case where the point of action of the lateral movement force, which is the resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side, is located in front of the turning center of the hull, the counter yaw moment that cancels the yaw moment about the turning center generated by the lateral movement force is generated by another thrust generated by the second propulsion device. As a result, even in a case where the point of action of the lateral movement force is located in front of the turning center of the hull, it is not necessary to change attachment angles of the first propulsion devices on both sides with respect to the hull to make the point of action of the resultant force coincide with the turning center of the hull. That is, it is possible to eliminate the need to use wedge plates to attach the first propulsion devices on both sides to the hull. As a result, it is possible to prevent rotation of the marine vessel during lateral movement of the marine vessel without deteriorating the navigation performance of the marine vessel. That is, it is possible to both prevent rotation of the marine vessel during lateral movement of the marine vessel and maintain the navigation performance of the marine vessel.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a marine vessel to which a marine propulsion system according to a first example embodiment of the present invention is applied.

FIG. 2 is a side view of the marine vessel to which the marine propulsion system according to an example embodiment of the present invention is applied.

FIG. 3 is a block diagram schematically illustrating a configuration of the marine propulsion system according to an example embodiment of the present invention.

FIG. 4 is a view for describing a problem during movement of the marine vessel in a lateral direction.

FIG. 5 is a view for describing movement of the marine vessel in a rightward lateral direction in an example embodiment of the present invention.

FIG. 6 is a view for describing movement of the marine vessel in a leftward lateral direction in an example embodiment of the present invention.

FIG. 7 is a plan view of the marine vessel in which a distance from a turning center to a propeller is increased in an example embodiment of the present invention.

FIGS. 8A to 8D are views for describing a configuration to increase the distance from the turning center to the propeller in an example embodiment of the present invention.

FIG. 9 is a view for describing movement of a marine vessel in a rightward lateral direction in a second example embodiment of the present invention.

FIG. 10 is a view for describing movement of the marine vessel in a leftward lateral direction in an example embodiment of the present invention.

FIG. 11 is a plan view of the marine vessel in which a distance from a turning center to a propeller is increased in an example embodiment of the present invention.

FIG. 12 is a view for describing movement of a marine vessel in a lateral direction using a conventional marine propulsion system.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

Hereinafter, example embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a marine vessel 10 to which a marine propulsion system according to a first example embodiment of the present invention is applied. FIG. 2 is a side view of the marine vessel 10 to which the marine propulsion system according to the present example embodiment is applied.

In FIGS. 1 and 2, the marine vessel 10 is, for example, a twin-hulled pontoon boat, and includes a long and narrow hull 11 positioned on a port side with respect to a center line CL, which extends through the center of the marine vessel 10 in a left-right direction and extends in a front-rear direction, and a long and narrow hull 12 positioned on a starboard side with respect to the center line CL. In addition, in the marine vessel 10, outboard motors 14 and 15 (first propulsion devices) are attached to sterns of the left hull 11 and the right hull 12, respectively. The outboard motors 14 and 15 can be steered in a rightward turning direction and a leftward turning direction with respect to the corresponding hulls 11 and 12, respectively.

In the present example embodiment, the steering in the rightward turning direction refers to a state in which the outboard motor 14, 15 rotates counterclockwise around the stern of the hull 11, 12 as a fulcrum in plan view of the marine vessel 10. The steering in the leftward turning direction refers to a state in which the outboard motor 14, 15 rotates clockwise around the stern of the hull 11, 12 as a fulcrum in plan view of the marine vessel 10. In addition, in the marine vessel 10, each of the outboard motors 14 and 15 is configured to be steered by, for example, 30° in each of the rightward turning direction and the leftward turning direction.

A pontoon boat, for example, has a configuration in which a deck 13 spans between the left and right hulls 11 and 12, and thus, the pontoon boat is wider than a normal monohull boat. Therefore, an arrangement interval (pitch) between the outboard motors 14 and 15 attached to the pontoon boat is also larger than that of outboard motors attached to a normal monohull boat. In addition, the pontoon boat is focused on stability rather than speed performance, and is suitably used for relatively low-speed cruising, fishing while staying on water, and the like. Therefore, the marine vessel 10 includes a small outboard motor for low-speed navigation or position adjustment during mooring, in addition to the outboard motors 14 and 15. For example, the marine vessel 10 includes a trolling motor 16 (second propulsion device) located toward a bow.

The trolling motor 16 includes a spindle-shaped submerged body 17 that houses an electric motor to drive a propeller 17a, and the submerged body 17 is attached to a distal end of a rod 18. In the trolling motor 16, a vessel operator or a rotary unit (not illustrated) axially rotates the rod 18 to which the submerged body 17 is attached, so that an orientation of the submerged body 17 can be freely changed. As a result, the trolling motor 16 can change a direction of thrust generated by the propeller 17a to a desired direction, and the trolling motor 16 can be used to change course at the time of low-speed navigation or position adjustment during mooring of the marine vessel 10. Normally, the trolling motor 16 is repositionable and can be arranged on the center line of the bow of one hull. As illustrated in the drawing, the trolling motor 16 can also be arranged on the center line CL of the bows of the hulls 11 and 12 (on the center line CL of the bow of the pontoon boat). In a case where the marine vessel 10 is navigating at a relatively high speed, the trolling motor 16 is pulled up to the deck 13 or the hulls 11 and 12 so as not to resist movement of the marine vessel 10.

FIG. 3 is a block diagram schematically illustrating a configuration of a marine propulsion system 19 according to the present example embodiment mounted on the marine vessel 10 in FIG. 1. In FIG. 3, the marine propulsion system 19 includes a boat control unit (BCU) 20, a multi function display (MFD) 21, a global navigation satellite system (GNSS) which is, for example, a global positioning system (GPS) 22, an inertial measurement unit (IMU) 23, a compass 24, a remote control unit 25, a joystick 26, a steering mechanism 27, a vessel operation panel 28, a remote control ECU 29, a main operation unit 30, and a steering control unit (SCU) 31. The elements of the marine propulsion system 19 are communicatively connected to one another.

The GPS 22 determines the current position of the marine vessel 10 and transmits the current position of the marine vessel 10 to the BCU 20. The IMU 23 measures behaviors of the hulls 11 and 12 and transmits a measurement result to the BCU 20. The compass 24 determines a bearing of the marine vessel 10 and transmits the bearing of the marine vessel 10 to the BCU 20.

The remote control unit 25 includes levers 25a corresponding to the outboard motors 14 and 15, respectively. The vessel operator operates levers 25a to switch the directions of the thrusts generated by the respective outboard motors 14, 15 back and forth, and adjusts outputs of the respective outboard motors 14, 15 to adjust a vessel speed. At this time, the remote control unit 25 transmits a signal(s) to control the outboard motors 14, 15 in response to the operation of the levers 25a to the BCU 20 and the remote control ECU 29. The joystick 26 is a control stick to operate the marine vessel 10, and transmits a signal to move the marine vessel 10 in a tilting direction of the joystick 26 to the BCU 20 and the remote control ECU 29. The steering mechanism 27 is a device for the vessel operator to determine a course of the marine vessel 10. The vessel operator can turn the marine vessel 10 rightward and leftward by rotating a steering wheel 27a of the steering mechanism 27 leftward and rightward. At this time, the steering mechanism 27 transmits a steering angle corresponding to a rotation operation on the steering wheel 27a to the remote control ECU 29 and the SCU 31.

The main operation unit 30 includes a main switch 30a and an engine shut-off switch 30b. The main switch 30a is an operator to collectively start and collectively stop engines (not illustrated) which are power sources of the outboard motors 14 and 15. The engine shut-off switch 30b is a switch to emergency stop the engines of the outboard motors 14 and 15. The MFD 21 is, for example, a color LCD display, and functions as a display that displays various types of information and also functions as a touch panel that receives an input from the vessel operator. The vessel operation panel 28 includes switches (not illustrated) corresponding to various vessel operation modes, and the vessel operator switches a mode of the marine vessel 10 to a desired vessel operation mode, for example, a fixed point holding mode, by operating the corresponding switch.

The SCU 31 is provided corresponding to each of the outboard motors 14 and 15. Each of the SCUs 31 controls a steering unit (not illustrated), which turns the corresponding outboard motor 14 or 15 with respect to the hull 11 or 12, to change the direction of the thrust of each of the outboard motors 14 and 15.

The BCU 20 determines a situation of the marine vessel 10 based on signals transmitted from the elements of the marine propulsion system 19, determines the magnitude of the thrust to be generated by each of the outboard motors 14 and 15 and the direction of the thrust to be taken, and transmits the determined magnitude and the determined direction to each remote control ECU 29. In addition, the BCU 20 controls a rotation unit of the trolling motor 16 to change the magnitude and direction of the thrust of the trolling motor 16.

One remote control ECU 29 is provided correspondingly to each of the outboard motors 14 and 15, and the remote control ECU 29 transmits signals to control the engine and steering unit of the outboard motor 14, 15 to an engine ECU (not illustrated) and the SCU 31 of the outboard motor 14, 15 according to signals transmitted from the BCU 20, the steering mechanism 27, the remote control unit 25, the joystick 26, and the like, to adjust the magnitude and direction of the thrust of each of the outboard motors 14 and 15.

FIG. 4 is a view for describing a problem during movement of the marine vessel 10 in a lateral direction. For example, to move the marine vessel 10 in a rightward lateral direction (a direction of the white rightward arrow in the drawing), the vessel operator operates the joystick 26 and/or the steering mechanism 27 to input an instruction for movement in the rightward lateral direction. At this time, the one SCU 31 steers the outboard motor 14 on the port side in the leftward turning direction and the other SCU 31 steers the outboard motor 15 on the starboard side in the rightward turning direction, so that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form an inverted V shape in plan view. Then, the one remote control ECU 29 causes the outboard motor 14 on the port side to generate a forward thrust fl and the other remote control ECU 29 causes the outboard motor 15 on the starboard side to generate a rearward thrust fr. A magnitude of the forward thrust fl and a magnitude of the rearward thrust fr are the same. As a result, a resultant force of the forward thrust fl and the rearward thrust fr acts on the marine vessel 10 as a lateral movement force F of the marine vessel 10 in the rightward lateral direction. In the present description, “forward” means a direction in which the bow of the marine vessel 10 faces, and “rearward” means a direction in which the stern of the marine vessel 10 faces.

As described above, the marine vessel 10 is a pontoon boat, and thus the pitch of the outboard motors 14 and 15 is larger than that of outboard motors attached to a normal monohull boat. Therefore, even when the outboard motor 14 on the port side is fully steered in the leftward turning direction and the outboard motor 15 on the starboard side is fully steered in the rightward turning direction, a point P of action of the lateral movement force F remains in front of a turning center G of the hulls. At this time, a clockwise yaw moment M about the turning center G is generated by the lateral movement force F, and when the marine vessel 10 moves in the rightward lateral direction, the marine vessel 10 rotates in a yaw direction about the turning center G.

In the present example embodiment, in order to reduce or prevent the rotation of the marine vessel 10 in the yaw direction about the turning center G when the marine vessel 10 moves in the rightward lateral direction, the thrust of the trolling motor 16 is used to generate a counter yaw moment MC that cancels the yaw moment M generated by the lateral movement force F.

FIG. 5 is a view for describing movement of the marine vessel 10 in the rightward lateral direction in the present example embodiment. In the present example embodiment, to move the marine vessel 10 in the rightward lateral direction (a direction of the white rightward arrow in the drawing), the one SCU 31 turns the outboard motor 14 on the port side in the rightward turning direction and the other SCU 31 turns the outboard motor 15 on the starboard side in the leftward turning direction so that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form a V shape in plan view.

In the marine vessel 10, when the outboard motor 14 on the port side is fully steered in the rightward turning direction and the outboard motor 15 on the starboard side is fully steered in the leftward turning direction, the outboard motor 14 on the port side and the outboard motor 15 on the starboard side approach each other. In the marine vessel 10, the pitch of the outboard motors 14 and 15 is set to be large to such an extent that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side do not interfere with each other at this time.

Then, the one remote control ECU 29 causes the outboard motor 14 on the port side to generate a rearward thrust fl, and the other remote control ECU 29 causes the outboard motor 15 on the starboard side to generate a forward thrust fr. A magnitude of the rearward thrust fl and a magnitude of the forward thrust fr are the same. As a result, a resultant force of the rearward thrust fl and the forward thrust fr acts on the marine vessel 10 as a lateral movement force F of the marine vessel 10 in the rightward lateral direction.

At this time, as illustrated in the drawing, since a line of action of the rearward thrust fl of the outboard motor 14 on the port side and a line of action of the forward thrust fr of the outboard motor 15 on the starboard side intersect each other behind the turning center G, a point P of action of the lateral movement force F is also positioned behind the turning center G. That is, since the point P of action of the lateral movement force F does not coincide with the turning center G, a counterclockwise yaw moment M about the turning center G is generated by the lateral movement force F.

Meanwhile, the BCU 20 axially rotates the rod 18 of the trolling motor 16 to cause the trolling motor 16 to generate a thrust FT (another thrust) in the rightward lateral direction. At this time, the thrust FT generates the counter yaw moment MC about the turning center G. Since the trolling motor 16 is disposed on the bow side, the counter yaw moment MC is a clockwise yaw moment. Therefore, the yaw moment M generated by the lateral movement force F in the rightward lateral direction can be canceled by the counter yaw moment MC.

A magnitude of the thrust FT to be generated by the trolling motor 16 is determined in consideration of a magnitude of the yaw moment M and a distance from the turning center G to the trolling motor 16. Specifically, the magnitude of the thrust FT is determined by the following Formula (1).

$\begin{array}{cc}\mathrm{Thrust}\mathrm{FT}=\left(\mathrm{Yaw}\mathrm{moment}M\right)/\left(\mathrm{Distance}\mathrm{from}\mathrm{turning}\mathrm{center}G\mathrm{to}\mathrm{trolling}\mathrm{motor}16\right)& \left(1\right)\end{array}$

Although the yaw moment M and the counter yaw moment MC are drawn to be offset from the turning center G for easy understanding in FIG. 5 and subsequent drawings, both the yaw moment M and the counter yaw moment MC are moments about the turning center G as described above.

FIG. 6 is a view for describing movement of the marine vessel 10 in the leftward lateral direction in the present example embodiment. To move the marine vessel 10 in the leftward lateral direction (a direction of the white leftward arrow in the drawing), the SCUs 31 steer the outboard motor 14 on the port side and the outboard motor 15 on the starboard side such that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form a V shape in plan view, in a similar manner to the case of moving the marine vessel 10 in the rightward lateral direction.

Then, the one remote control ECU 29 causes the outboard motor 14 on the port side to generate a forward thrust fl and the other remote control ECU 29 causes the outboard motor 15 on the starboard side to generate a rearward thrust fr. A magnitude of the forward thrust fl and a magnitude of the rearward thrust fr are the same. As a result, a resultant force of the forward thrust fl and the rearward thrust fr acts on the marine vessel 10 as a lateral movement force F of the marine vessel 10 in the leftward lateral direction.

Also at this time, similar to the case of moving the marine vessel 10 in the rightward lateral direction, a line of action of the forward thrust fl of the outboard motor 14 on the port side and a line of action of the rearward thrust fr of the outboard motor 15 on the starboard side intersect each other behind the turning center G, and thus a point P of action of the lateral movement force F is also positioned behind the turning center G. Then, a clockwise yaw moment M about the turning center G is generated by the lateral movement force F of which point P of action is positioned behind the turning center G.

Meanwhile, the BCU 20 causes the trolling motor 16 to generate a thrust FT in the leftward lateral direction. At this time, the thrust FT generates a counterclockwise counter yaw moment MC about the turning center G. The yaw moment M generated by the lateral movement force F in the leftward lateral direction can be canceled by the counter yaw moment MC. Similarly in a case of moving the marine vessel 10 in the leftward lateral direction, a magnitude of the thrust FT generated by the trolling motor 16 is determined by Formula (1) above.

According to the present example embodiment, in a case of the marine vessel 10 to be moved in the lateral direction, the outboard motor 14 on the port side and the outboard motor 15 on the starboard side are steered such that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form a V shape in plan view. Then, the thrust fl and the thrust fr opposite to each other are generated by the outboard motor 14 on the port side and the outboard motor 15 on the starboard side, so that the lateral movement force F of which point P of action is positioned behind the turning center G is generated. Further, the thrust FT in the same direction as the lateral movement force F is generated by the trolling motor 16 disposed on the bow side. As a result, the yaw moment M generated by the lateral movement force F can be canceled by the counter yaw moment MC generated by the thrust FT.

As a result, it is not necessary to change attachment an angle(s) of the outboard motor 14 on the port side and/or the outboard motor 15 on the starboard side with respect to the hull 11 or 12 to make the point of action of the resultant force of the thrust fl and the thrust fr coincide with the turning center G. That is, it is possible to eliminate the need to use wedge plates for attaching the outboard motor 14 on the port side to the hull 11 and the outboard motor 15 on the starboard side to the hull 12. As a result, it is possible to prevent rotation of the marine vessel 10 in the yaw direction during lateral movement of the marine vessel 10 without deteriorating navigation performance of the marine vessel 10. That is, it is possible to both prevent of rotation of the marine vessel 10 during lateral movement of the marine vessel 10 and maintain navigation performance of the marine vessel 10.

In addition, in the present example embodiment, an acting direction of the lateral movement force F, which is the resultant force of the thrust fl of the outboard motor 14 on the port side and the thrust fr of the outboard motor 15 on the starboard side, is the same as an acting direction of the thrust FT generated by the trolling motor 16. Therefore, not only the lateral movement force F but also the thrust FT contributes to the lateral movement of the marine vessel 10, so that lateral movement efficiency of the marine vessel 10 is improved.

In the present example embodiment, the trolling motor 16 is used as a generation source of the thrust FT that generates the counter yaw moment MC. However, in a case where the marine vessel 10 includes a bow thruster or a side thruster on the bow side, the thrust FT may be generated by the bow thruster or the side thruster.

By the way, in the present example embodiment, since the line of action of the thrust fl of the outboard motor 14 on the port side and the line of action of the thrust fr of the outboard motor 15 on the starboard side intersect each other considerably behind the turning center G, an arm of the yaw moment M is long, and the yaw moment M is large. In order to cancel the large yaw moment M, it is necessary to increase the thrust FT generated by the trolling motor 16 to balance the counter yaw moment MC with the yaw moment M.

However, the trolling motor 16 is configured to be repositionable, and thus, the trolling motor 16 is a relatively small propulsion device. Therefore, an electric motor included in the trolling motor 16 is also relatively small, and thus, the magnitude of the thrust FT that can be generated by the trolling motor 16 is limited. In addition, when the thrust FT is increased, electricity costs increase, and in some cases, a charge amount of a battery (not illustrated) included in the marine vessel 10 may become zero during lateral movement. Therefore, it is preferable that the thrust FT to be generated by the trolling motor 16 is small.

Therefore, in order to decrease the thrust FT while maintaining the magnitude of the counter yaw moment MC, it is preferable to increase a “distance from the turning center G to the propeller 17a that generates the thrust FT”, which is an arm length of the counter yaw moment MC, as illustrated in FIG. 7. Specifically, the thrust FT is generated in front of the bow of the hull 11 (12).

FIGS. 8A to 8D are views for describing a configuration to increase the distance from the turning center G to the propeller 17a.

For example, as illustrated in FIG. 8A, the trolling motor 16 may include an arm 32 that can extend forward, and the rod 18 may be attached at vicinity of a front end of the arm 32. In this case, as illustrated in FIG. 8B, the arm 32 extends by sliding forward with respect to the hull 11 (12), so that the submerged body 17 including the propeller 17a is positioned in front of the bow. As a result, the distance from the turning center G to the propeller 17a is increased, and therefore the counter yaw moment MC that cancels the yaw moment M can be generated even with the small thrust FT.

Further, for example, as illustrated in FIG. 8C, the trolling motor 16 may include a case 33 that can be tilted, and the rod 18 may be housed in the case 33 in an extendable manner. In this case, as illustrated in FIG. 8D, the case 33 is tilted so that a lower side of the case 33 moves forward, and further, the rod 18 is extended from the case 33. At this time, the rod 18 is inclined with respect to the water surface. Then, the submerged body 17 attached to the distal end of the rod 18 is submerged in front of the bow. With such a configuration as well, it is possible to increase the distance from the turning center G to the propeller 17a of the submerged body 17.

Although in FIGS. 8A to 8D the submerged body 17 is directed forward, the submerged body 17 is directed in a movement direction (lateral direction) when the marine vessel 10 moves in the lateral direction.

Next, a second example embodiment of the present invention will be described. Configurations and operations in the second example embodiment are basically the same as those of the first example embodiment described above. Therefore, in the following description, descriptions of configurations and effects overlapping those of the first example embodiment will be omitted, and configurations and effects different from those of the first example embodiment will be described.

In the first example embodiment described above, a method of reducing or preventing rotation in a yaw direction about a turning center G by using thrust FT of a trolling motor 16 in a case where an outboard motor 14 on a port side and an outboard motor 15 on a starboard side form a V shape has been described. In the second example embodiment, a method of reducing or preventing the rotation in the yaw direction about the turning center G by using the thrust FT of the trolling motor 16 in a case where the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form an inverted V shape will be described.

FIG. 9 is a view for describing movement of a marine vessel 10 in a rightward lateral direction in the second example embodiment of the present invention. In the present example embodiment, to move the marine vessel 10 in the rightward lateral direction (a direction of the white rightward arrow in the drawing), one SCU 31 steers the outboard motor 14 on the port side in a leftward turning direction and the other SCU 31 steers the outboard motor 15 on the starboard side in a rightward turning direction so that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form an inverted V shape in plan view.

Then, the one remote control ECU 29 causes the outboard motor 14 on the port side to generate a forward thrust fl and the other remote control ECU 29 causes the outboard motor 15 on the starboard side to generate a rearward thrust fr. A magnitude of the forward thrust fl and a magnitude of the rearward thrust fr are the same. As a result, a resultant force of the forward thrust fl and the rearward thrust fr acts on the marine vessel 10 as a lateral movement force F of the marine vessel 10 in the rightward lateral direction.

At this time, as illustrated in the drawing, since a line of action of the forward thrust fl of the outboard motor 14 on the port side and a line of action of the rearward thrust fr of the outboard motor 15 on the starboard side intersect each other in front of the turning center G, a point P of action of the lateral movement force F is also positioned in front of the turning center G. That is, since the point P of action of the lateral movement force F does not coincide with the turning center G, a clockwise yaw moment M about the turning center G is generated by the lateral movement force F.

Meanwhile, a BCU 20 axially rotates a rod 18 of the trolling motor 16 to cause the trolling motor 16 to generate the thrust FT of which a direction is opposite to the lateral movement force F (“a direction opposite to the lateral movement force F” is a leftward lateral direction). The thrust FT in the leftward lateral direction generates a counter yaw moment MC about the turning center G. The counter yaw moment MC is a counterclockwise yaw moment. Therefore, the yaw moment M generated by the lateral movement force F in the rightward lateral direction can be canceled by the counter yaw moment MC. Also in the present example embodiment, a magnitude of the thrust FT generated by the trolling motor 16 is determined by Formula (1) above.

FIG. 10 is a view for describing movement of the marine vessel 10 in the leftward lateral direction in the present example embodiment. Similarly, to move the marine vessel 10 in the leftward lateral direction, the SCUs 31 steer the outboard motor 14 on the port side and the outboard motor 15 on the starboard side such that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form an inverted V shape in plan view.

Then, the one remote control ECU 29 causes the outboard motor 14 on the port side to generate a rearward thrust fl, and the other remote control ECU 29 causes the outboard motor 15 on the starboard side to generate a forward thrust fr. A magnitude of the rearward thrust fl and a magnitude of the forward thrust fr are the same. As a result, a resultant force of the rearward thrust fl and the forward thrust fr acts on the marine vessel 10 as a lateral movement force F of the marine vessel 10 in the leftward lateral direction.

Also at this time, similar to the case of moving the marine vessel 10 in the rightward lateral direction, a line of action of the rearward thrust fl of the outboard motor 14 on the port side and a line of action of the forward thrust fr of the outboard motor 15 on the starboard side intersect each other in front of the turning center G, and thus a point P of action of the lateral movement force F is also positioned in front of the turning center G. That is, since the point P of action of the lateral movement force F does not coincide with the turning center G, a counterclockwise yaw moment M about the turning center G is generated by the lateral movement force F.

Meanwhile, a BCU 20 axially rotates a rod 18 of the trolling motor 16 to cause the trolling motor 16 to generate the thrust FT of which a direction is opposite to the lateral movement force F (“a direction opposite to the lateral movement force F” is the rightward lateral direction). The thrust FT in the rightward lateral direction generates a counter yaw moment MC about the turning center G. The counter yaw moment MC is a clockwise yaw moment. Therefore, the yaw moment M generated by the lateral movement force F in the leftward lateral direction can be canceled by the counter yaw moment MC. Also in the present example embodiment, a magnitude of the thrust FT generated by the trolling motor 16 is determined by Formula (1) above.

According to the present example embodiment, in a case of the marine vessel 10 to be moved in the lateral direction, the outboard motor 14 on the port side and the outboard motor 15 on the starboard side are steered such that the outboard motor 14 on the port side and the outboard motor 15 on the starboard side form an inverted V shape in plan view. Then, the thrust fl of the outboard motor 14 on the port side and the thrust fr of the outboard motor 15 on the starboard side opposite to each other are generated, so that the lateral movement force F of which point P of action is positioned in front of the turning center G is generated. Further, the thrust FT in a direction opposite to the lateral movement force F is generated by the trolling motor 16 disposed at the bow side. As a result, the yaw moment M generated by the lateral movement force F can be canceled by the counter yaw moment MC generated by the thrust FT. As a result, the present example embodiment can also achieve effects similar to those of the first example embodiment.

As described above, also in the second example embodiment, the magnitude of the thrust FT generated by the trolling motor 16 is determined by Formula (1) above. In the second example embodiment, a distance from the lateral movement force F to the turning center is very short as compared with that in the first example embodiment, whereas a distance from the turning center G to the trolling motor 16 is similar to that in the first example embodiment. Therefore, in the second example embodiment, the thrust FT may be very small as compared with the first example embodiment, and for example, the thrust FT may be smaller than the lateral movement force F. As a result, it is possible to use the smaller lower-output trolling motor 16.

In the present example embodiment, since an acting direction of the lateral movement force F is opposite to an acting direction of the thrust FT generated by the trolling motor 16, the thrust FT inhibits the marine vessel 10 from moving in the lateral direction. As described above, since the thrust FT is smaller than the lateral movement force F, the movement of the marine vessel 10 in the lateral direction is not stopped by the thrust FT. However, from the viewpoint of efficiently moving the marine vessel 10 in the lateral direction, it is preferable that the thrust FT generated by the trolling motor 16 is smaller.

Therefore, in order to decrease the thrust FT while maintaining a magnitude of the counter yaw moment MC, also in the second example embodiment, similarly to the first example embodiment, a distance from the turning center G to a propeller 17a that generates the thrust FT may be increased (see FIG. 11). Specifically, the thrust FT may be generated in front of the bow of the hull 11 (12). Also in the second example embodiment, it is preferable to increase the distance from the turning center G to the propeller 17a by providing the configurations illustrated in FIGS. 8A to 8D.

Although example embodiments of the present invention have been described above, the present invention is not limited to the above-described example embodiments, and various modifications and changes can be made within the scope of the gist of the present invention.

The marine propulsion system according to each of the example embodiments of the present invention is applied to a pontoon boat that is a twin boat as an example. However, the marine vessel to which the marine propulsion system according to each of the example embodiments of the present invention is applied may be any marine vessel as long as it includes an outboard motor on each of the port side and the starboard side. For example, the marine propulsion system according to each of the example embodiments of the present invention may be applied to a trimaran having a larger width, or may be applied to a monohull boat having a wide hull shape and having a large pitch between left and right outboard motors. The outboard motor may include an electric motor as a power source instead of the engine.

In addition, the marine propulsion system according to each of the example embodiments of the present invention may be applied to a marine vessel including three or more outboard motors. Further, the marine propulsion system according to each of the example embodiments of the present invention may be applied not only to a marine vessel including outboard motors at the sterns of both sides of the hull, but also to a marine vessel including inboard/outboard motors or jet propulsion devices at the sterns of both sides of the hull.

The gist of the present invention can be applied not only in a case where the marine vessel 10 moves in the lateral direction but also in a case where the marine vessel 10 moves obliquely forward or obliquely rearward, wherein the gist of the present invention is to reduce or prevent rotation in the yaw direction about the turning center G during movement by the thrust FT of the trolling motor 16.

While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Claims

1. A marine propulsion system comprising: a plurality of first propulsion devices located at a stern of a hull, and including at least a first propulsion device on a port side of the hull with respect to a center line extending in a front-rear direction of the hull, and a first propulsion device on a starboard side of the hull with respect to the center line; anda second propulsion device located toward a bow of the hull;a controller configured or programmed, when moving the hull in a lateral direction, to: fully steer in a leftward turning direction the first propulsion device on the port side of the hull, and fully steer in a rightward turning direction the first propulsion device on the starboard side of the hull so that the first propulsion device on the port side and the first propulsion device on the starboard side form an inverted V shape in a plan view;cause the first propulsion device on the port side to generate a forward thrust or a rearward thrust and cause the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located in front of a turning center of the hull; andcontrol the second propulsion device to generate another thrust to generate a counter yaw moment to cancel a yaw moment about the turning center generated by the lateral movement force.

2. The marine propulsion system according to claim 1, wherein the controller is further configured or programmed to: steer the first propulsion device on the port side in the rightward turning direction and steer the first propulsion device on the starboard side in the leftward turning direction so that the first propulsion device on the port side and the first propulsion device on the starboard side form a V shape in the plan view;cause the first propulsion device on the port side to generate the forward thrust or the rearward thrust and cause the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located behind the turning center; andcause the second propulsion device to generate the another thrust in a same direction as the resultant force.

3. The marine propulsion system according to claim 2, wherein, even when the first propulsion device on the port side is steered in the rightward turning direction and the first propulsion device on the starboard side is steered in the leftward turning direction, the first propulsion device on the port side and the first propulsion device on the starboard side do not interfere with each other.

4. The marine propulsion system according to claim 2, wherein the second propulsion device generates the another thrust in front of the bow of the hull in the same direction as the resultant force.

5. The marine propulsion system according to claim 4, wherein the second propulsion device includes an extendable arm and a propeller to generate the another thrust; andthe extendable arm is extended to locate the propeller in front of the bow of the hull.

6. The marine propulsion system according to claim 4, wherein the second propulsion device includes an extendable rod and a propeller to generate the another thrust; andthe propeller is located at a distal end of the extendable rod, and the extendable rod is inclined with respect to a water surface to submerge the propeller in front of the bow of the hull.

7. The marine propulsion system according to claim 2, wherein to move the hull in the lateral direction to the starboard side, the controller is configured or programmed to cause the first propulsion device on the port side to generate the rearward thrust, cause the first propulsion device on the starboard side to generate the forward thrust, and cause the second propulsion device to generate the another thrust toward the starboard side; andto move the hull in the lateral direction to the port side, the controller is configured or programmed to cause the first propulsion device on the port side to generate the forward thrust, cause the first propulsion device on the starboard side to generate the rearward thrust, and cause the second propulsion device to generate the another thrust toward the port side.

8. The marine propulsion system according to claim 1, wherein the controller is configured or programmed to: steer the first propulsion device on the port side in the leftward turning direction and steer the first propulsion device on the starboard side in the rightward turning direction so that the first propulsion device on the port side and the first propulsion device on the starboard side form the inverted V shape in the plan view;cause the first propulsion device on the port side to generate the forward thrust or the rearward thrust and cause the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located in front of the turning center of the hull; andcause the second propulsion device to generate the another thrust in a direction opposite to the resultant force.

9. The marine propulsion system according to claim 8, wherein a magnitude of the another thrust in the direction opposite to the resultant force is smaller than a magnitude of the resultant force.

10. The marine propulsion system according to claim 8, wherein the second propulsion device generates the another thrust in front of the bow of the hull in the direction opposite to the resultant force.

11. The marine propulsion system according to claim 10, wherein the second propulsion device includes an extendable arm and a propeller to generate the another thrust; and the extendable arm is extended to locate the propeller in front of the bow of the hull.

12. The marine propulsion system according to claim 10, wherein the second propulsion device includes an extendable rod and a propeller to generate the another thrust; andthe propeller is located at a distal end of the extendable rod, and the extendable rod is inclined with respect to a water surface to submerge the propeller in front of the bow of the hull.

13. The marine propulsion system according to claim 8, wherein to move the hull in the lateral direction to the starboard side, the controller is configured or programmed to cause the first propulsion device on the port side to generate the forward thrust, cause the first propulsion device on the starboard side to generate the rearward thrust, and cause the second propulsion device to generate the another thrust toward the port side; andto move the hull in the lateral direction to the port side, the controller is configured or programmed to cause the first propulsion device on the port side to generate the rearward thrust, cause the first propulsion device on the starboard side to generate the forward thrust, and cause the second propulsion device to generate the another thrust toward the starboard side.

14. A control method of a marine propulsion system including a plurality of first propulsion devices located at a stern of a hull and including at least a first propulsion device on a port side of the hull with respect to a center line extending in a front-rear direction of the hull and a first propulsion device on a starboard side of the hull with respect to the center line, and a second propulsion device located toward a bow of the hull, the control method comprising: when moving the hull in a lateral direction: fully steering in a leftward turning direction the first propulsion device located on the port side of the hull, and fully steering in a rightward turning direction the first propulsion device located on the starboard side of the hull so that the first propulsion device on the port side and the first propulsion device on the starboard side form an inverted V shape in a plan view;causing the first propulsion device on the port side to generate a forward thrust or a rearward thrust and causing the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located in front of a turning center of the hull; andcontrolling the second propulsion device to generate another thrust to generate a counter yaw moment to cancel a yaw moment about the turning center generated by the lateral movement force.

15. A marine vessel comprising: a marine propulsion system including: a plurality of first propulsion devices located at a stern of a hull, and including at least a first propulsion device on a port side of the hull with respect to a center line extending in a front-rear direction of the hull, and a first propulsion device on a starboard side of the hull with respect to the center line;a second propulsion device located toward a bow of the hull; anda controller configured or programmed, when moving the hull in a lateral direction, to: fully steer in a leftward turning direction the first propulsion device located on the port side of the hull, and fully steer in a rightward turning direction the first propulsion device located on the starboard side of the hull so that the first propulsion device on the port side and the first propulsion device on the starboard side form an inverted V shape in a plan view;cause the first propulsion device on the port side to generate a forward thrust or a rearward thrust and cause the first propulsion device on the starboard side to generate a thrust in a direction opposite to the thrust generated by the first propulsion device on the port side so that a point of action of a lateral movement force that is a resultant force of the thrust generated by the first propulsion device on the port side and the thrust generated by the first propulsion device on the starboard side is located in front of a turning center of the hull; andcontrol the second propulsion device to generate another thrust to generate a counter yaw moment to cancel a yaw moment about the turning center generated by the lateral movement force.