WATERCRAFT AND METHOD OF CONTROLLING WATERCRAFT

Abstract

A watercraft includes a first steering actuator to swing a first nozzle deflector to change a first direction of water jetted from the first nozzle deflector, and a second steering actuator to swing a second nozzle deflector to change a second direction of water jetted from the second nozzle deflector. A controller is configured or programmed to control the first steering actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft, and also control the second steering actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is determined that a watercraft body is intended to move straight forward based on steering information.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2022-210876 filed on Dec. 27, 2022. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to watercraft and methods of controlling watercraft.

2. Description of the Related Art

In recent years, there has been known a type of watercraft propelled with a jet of water such as a sport boat and a jet boat. This type of watercraft is configured to change the direction of the jet of water to change the steering direction of the watercraft.

However, the watercraft of the jet type is not provided with a rudder as is a watercraft of the propeller type. Thus, a further device is required for the watercraft of the jet type to provide good stability during straight movement of the watercraft.

On the other hand, there has been disclosed a watercraft configured to provide good performance during straight movement by inhibiting a watercraft body from swinging to the right and left (e.g., see Japan Laid-open Patent Application Publication No. 2006-199189). This watercraft is configured to direct propellers of outboard motors outward during straight movement such that imaginary lines extending from the rotational axes of the propellers intersect with each other at a location ahead of the outboard motors in the moving direction.

However, the configuration disclosed in Japan Laid-open Patent Application Publication No. 2006-199189 is intended for the watercraft of the propeller type. Thus, a further improvement is required to apply this configuration to a watercraft of the jet type such that the watercraft of the jet type is able to provide good stability during straight movement.

SUMMARY OF THE INVENTION

Example embodiments of the present invention provide watercraft and methods of controlling watercraft that make it possible for the watercraft to easily provide good stability during straight movement even when the watercraft is of the jet propelled type.

A watercraft propelled by a jet of water according to a first example embodiment of the present invention includes a watercraft body, a first jet propulsion device, a second jet propulsion device, a first actuator, a second actuator, a steering sensor, and a controller. The first jet propulsion device is attached to a port side of a rear portion of the watercraft body and includes a first nozzle deflector, from which water is jetted, that is swingable right and left. The second jet propulsion device is attached to a starboard side of the rear portion of the watercraft body symmetrically to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body and includes a second nozzle deflector, from which water is jetted, that is swingable right and left. The first actuator is operable to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector. The second actuator is operable to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector. The steering sensor detects steering information regarding steering of the watercraft body. The controller is configured or programmed to control the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft and also control the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.

A method of controlling a watercraft according to a second example embodiment of the present invention includes controlling a watercraft including a watercraft body, a first jet propulsion device, a second jet propulsion device, a first actuator, and a second actuator. The first jet propulsion device is attached to a port side of a rear portion of the watercraft body and includes a first nozzle deflector, from which water is jetted, that is swingable right and left. The second jet propulsion device is attached to a starboard side of the rear portion of the watercraft body symmetrical to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body and includes a second nozzle deflector, from which water is jetted, that is swingable right and left. The first actuator is operable to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector. The second actuator is operable to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector. The method of controlling the watercraft includes detecting that the watercraft body is intended to move straight forward based on information regarding steering of the watercraft body, controlling the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft and also controlling the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is detected that the watercraft body is intended to move straight forward.

A watercraft according to a third example embodiment of the present invention includes a watercraft body, a first propulsion device, a second propulsion device, a direction changer, a steering sensor, and a controller. The first propulsion device is attached to a port side of the watercraft body and generates a thrust by jetting out water therefrom. The second propulsion device is attached to a starboard side of the watercraft body symmetrically to the first propulsion device with respect to a back-and-forth direction of the watercraft body and generates a thrust by jetting out water therefrom. The direction changer is operable to change a first direction of the water jetted out from the first propulsion device and a second direction of the water jetted out from the second propulsion device. The steering sensor is operable to detect steering information regarding steering of the watercraft body. The controller is configured or programmed to control the direction changer to incline the first direction leftward with respect to a center of gravity of the watercraft and incline the second direction rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.

Overall, when it is determined that the watercraft body is intended to move straight forward, the direction of the water jetted from the first nozzle deflector is inclined leftward with respect to the center of gravity of the watercraft, and the direction of the water jetted from the second nozzle deflector is inclined rightward with respect to the center of gravity of the watercraft. Thus, the direction of the water jetted from the first nozzle deflector and the direction of the water jetted from the second nozzle deflector are set based on the center of gravity of the watercraft. Thus, it is possible for the watercraft to easily provide good stability during straight movement.

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 side view of a watercraft according to an example embodiment of the present invention.

FIG. 2 is a top view of the watercraft.

FIG. 3 is a cross-sectional side view of the watercraft.

FIG. 4 is a schematic diagram showing a system to control the watercraft.

FIG. 5 is a plan view for explaining a first direction of

a first nozzle deflector and a second direction of a second nozzle deflector.

FIG. 6A is a side view for explaining a pitch angle of the watercraft.

FIG. 6B is a side view for explaining a pitch angle of the watercraft.

FIG. 7A is a plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are changed in accordance with the center of gravity of the watercraft.

FIG. 7B is a plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are changed in accordance with the center of gravity of the watercraft.

FIG. 8A is a chart showing a relationship between a steering operation of a steering member and a nozzle angle.

FIG. 8B is a schematic plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are controlled during steering.

FIG. 8C is a schematic plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are controlled during steering.

FIG. 8D is a schematic plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are controlled during steering.

FIG. 8E is a schematic plan view for explaining how the first direction of the first nozzle deflector and the second direction of the second nozzle deflector are controlled during steering.

FIG. 9 is a flowchart showing a method of controlling the watercraft according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

Watercraft according to example embodiments of the present invention will be hereinafter explained with reference to drawings. FIG. 1 is a side view of a watercraft 1 according to an example embodiment. FIG. 2 is a top view of the watercraft 1. In the present example embodiment, the watercraft 1 is a type of watercraft called a jet boat or a sport boat.

The watercraft 1 includes a watercraft body 2, a first propulsion device 3A, and a second propulsion device 3B. The watercraft body 2 includes a deck 11 and a hull 12. The hull 12 is disposed directly below the deck 11. A cockpit 13 is disposed on the deck 11. The first and second propulsion devices 3A and 3B are attached to the watercraft body 2. The first propulsion device 3A is attached to the port side of a rear portion of the watercraft body 2. The second propulsion device 3B is attached to the starboard side of the rear portion of the watercraft body 2. The first and second propulsion devices 3A and 3B are jet propulsion devices. It should be noted that a back-and-forth direction and a right-and-left direction are directions defined based on the watercraft 1. In other words, a forward moving direction of the watercraft 1 is defined as a front direction, whereas a rearward moving direction thereof is defined as a rear direction. On the other hand, a direction inclined rightward with respect to the forward moving direction of the watercraft 1 is defined as a right direction, whereas a direction inclined leftward with respect to the forward moving direction of the watercraft 1 is defined as a left direction. The first and second propulsion devices 3A and 3B are disposed on both sides of an axis O extending along the back-and-forth direction that extends through the right-and-left directional center of the watercraft body 2.

FIG. 3 is a cross-sectional side view of the watercraft 1. FIG. 3 shows portion of the first propulsion device 3A in a cross-sectional representation. As shown in FIG. 3, the first propulsion device 3A is accommodated in the watercraft body 2. The first propulsion device 3A includes a first engine 4A, a first jet pump 5A, a first nozzle deflector 6A, and a first reverse gate 7A. The first engine 4A is connected to the first jet pump 5A. The first jet pump 5A is driven by the first engine 4A so as to suck water from the surroundings of the watercraft body 2 and jet the water. Accordingly, the first jet pump 5A generates a thrust to move the watercraft body 2.

The first jet pump 5A includes a drive shaft 21, an impeller 22, and a pump housing 23. The drive shaft 21 is connected to an output shaft 25 of the first engine 4A through a coupling 24. The impeller 22 is connected to the drive shaft 21. The impeller 22 is disposed inside the pump housing 23. The impeller 22 is rotated together with the drive shaft 21 in order to suck water through a water suction port 26. The impeller 22 jets the sucked water rearward through a jet port of the pump housing 23.

The first nozzle deflector 6A is disposed directly behind the first jet pump 5A. The first nozzle deflector 6A is swingable right and left. The first nozzle deflector 6A changes the direction of water jetted from the first jet pump 5A to the right-and-left direction. The first reverse gate 7A is disposed directly behind the first nozzle deflector 6A. The first reverse gate 7A is switchable between a forward moving position and a rearward moving position. The direction of water jetted from the first jet pump 5A is changed in accordance with the position of the first reverse gate 7A among the forward moving position and the rearward moving position. Movement of the watercraft 1 is thus switched between forward movement and rearward movement.

The second propulsion device 3B is disposed bilaterally symmetrical to the first propulsion device 3A with respect to the axis O extending along the back-and-forth direction of the watercraft body 2. The second propulsion device 3B is configured in similar manner to the first propulsion device 3A. As shown in FIG. 2, the second propulsion device 3B includes a second engine 4B, a second jet pump 5B, a second nozzle deflector 6B, and a second reverse gate 7B. The second engine 4B, the second jet pump 5B, the second nozzle deflector 6B, and the second reverse gate 7B are configured in similar manner to the first engine 4A, the first jet pump 5A, the first nozzle deflector 6A, and the first reverse gate 7A, respectively. Thus, detailed explanation thereof will be hereinafter omitted.

As shown in FIG. 2, the watercraft body 2 includes ballast water tanks 41, 42, and 43. The ballast water tanks 41, 42, and 43 are accommodated in the watercraft body 2. More specifically, the watercraft body 2 includes the first ballast water tank 41, the second ballast water tank 42, and the third ballast water tank 43. The first ballast water tank 41 is disposed in the middle of the watercraft body 2 in the right-and-left direction. The second and third ballast water tanks 42 and 43 are disposed bilaterally symmetrical to each other. It should be noted that the number of ballast water tanks is not limited to three, and the number of ballast water tanks may be less than or greater than three.

FIG. 4 is a schematic diagram showing a system to operate the watercraft 1. As shown in FIG. 4, the watercraft 1 includes a controller 10. The controller 10 includes a processor such as a CPU (Central Processing Unit) and memories (storage) such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The controller 10 is configured or programmed to control the watercraft 1.

The watercraft 1 includes a first steering actuator 31A (exemplary first actuator, or exemplary direction changer) and a first shift actuator 32A. The controller 10 is connected to the first engine 4A, the first steering actuator 31A, and the first shift actuator 32A in a communicable manner.

The first steering actuator 31A is connected to the first nozzle deflector 6A of the first propulsion device 3A. The first steering actuator 31A changes a first direction defined as the direction of water jetted from the first nozzle deflector 6A. FIG. 5 is a diagram for explaining the first direction of the first nozzle deflector 6A and a second direction of the second nozzle deflector 6B. As shown in FIG. 5, the first direction (D1) faces rearward along the axis (M1) of the first nozzle deflector 6A. The first direction D1 can be expressed as the nozzle angle (α) of the first nozzle deflector 6A. The nozzle angle α is defined by the first direction D1 and a direction facing directly rearward as one of opposite directions defining the back-and-forth direction (M0). The nozzle angle α is an angle of the axis M1 of the first nozzle deflector 6A extending rearward from the first nozzle deflector 6A with respect to the back-and-forth direction M0 of the watercraft 1. The first steering actuator 31A changes the nozzle angle α at which water is jetted from the first propulsion device 3A in the first direction D1. The first steering actuator 31A includes, for instance, an electric motor. Alternatively, the first steering actuator 31A may be another type of actuator such as a hydraulic cylinder.

The first shift actuator 32A is connected to the first reverse gate 7A of the first propulsion device 3A. The first shift actuator 32A switches the position of the first reverse gate 7A between the forward moving position and the rearward moving position. The first shift actuator 32A includes, for instance, an electric motor. Alternatively, the first shift actuator 32A may be another type of actuator such as a hydraulic cylinder.

The watercraft 1 includes a second steering actuator 31B (exemplary second actuator, or exemplary direction changer) and a second shift actuator 32B. The controller 10 is connected to the second engine 4B, the second steering actuator 31B, and the second shift actuator 32B in a communicable manner. The second steering actuator 31B is connected to the second nozzle deflector 6B of the second propulsion device 3B. The second steering actuator 31B changes the second direction defined as the direction of water jetted from the second nozzle deflector 6B. As shown in FIG. 5, the second direction (D2) faces rearward along the axis (M2) of the second nozzle deflector 6B. The second direction D2 can be expressed as the nozzle angle (β) of the second nozzle deflector 6B. The nozzle angle β is defined by the second direction D2 and a direction facing directly rearward as one of opposite directions defining the back-and-forth direction M0. The nozzle angle β is an angle of the axis M2 of the second nozzle deflector 6B extending rearward from the second nozzle deflector 6B with respect to the back-and-forth direction M0 of the watercraft 1. The second steering actuator 31B changes the nozzle angle β at which water is jetted from the second propulsion device 3B in the second direction D2. The second steering actuator 31B includes, for instance, an electric motor. Alternatively, the second steering actuator 31B may be another type of actuator such as a hydraulic cylinder. The first and second steering actuators 31A and 31B are direction changers to change the angle at which water is jetted from the first propulsion device 3A and the angle at which water is jetted from the second propulsion device 3B.

The second shift actuator 32B is connected to the second reverse gate 7B of the second propulsion device 3B. The second shift actuator 32B switches the position of the second reverse gate 7B between the forward moving position and the rearward moving position. The second shift actuator 32B includes, for instance, an electric motor. Alternatively, the second shift actuator 32B may be another type of actuator such as a hydraulic cylinder.

The watercraft 1 includes a steering member 14 (exemplary steering member) and a remote controller 15 (exemplary throttle). The controller 10 is connected to the steering member 14 and the remote controller 15 in a communicable manner. The steering member 14 and the remote controller 15 are disposed in the cockpit 13.

The steering member 14 is operated to steer the watercraft 1. In other words, the controller 10 controls a bow direction of the watercraft 1 in accordance with the operation of the steering member 14. The steering member 14 includes, for instance, a steering wheel. The steering member 14 includes a sensor 140 (exemplary steering sensor). The sensor 140 outputs a steering signal indicating the operating direction and the operating amount of the steering member 14.

The controller 10 receives the steering signal from the sensor 140. The controller 10 controls the first steering actuator 31A based on the steering signal so as to control the nozzle angle of the first propulsion device 3A. The controller 10 controls the second steering actuator 31B based on the steering signal so as to control the nozzle angle of the second propulsion device 3B. The bow direction of the watercraft 1 is thus changed right and left.

The remote controller 15 regulates the magnitude of the thrust generated by each of the first and second propulsion devices 3A and 3B. The remote controller 15 includes a first throttle member 15A and a second throttle member 15B. The first throttle member 15A is operated to regulate the output from the first engine 4A and switch between forward movement and rearward movement. The second throttle member 15B is operated to regulate the output from the second engine 4B and switch between forward movement and rearward movement. The first throttle member 15A includes a sensor 151 (exemplified as not only an opening degree sensor but also a position-of-throttle-member detector). The sensor 151 outputs a first throttle signal indicating the operating direction and the operating amount of the first throttle member 15A. The second throttle member 15B includes a sensor 152 (exemplified as not only the opening degree sensor but also the position-of-throttle-member detector). The sensor 152 outputs a second throttle signal indicating the operating direction and the operating amount of the second throttle member 15B. Each of the first and second throttle members 15A and 15B includes a lever. However, each of the first and second throttle members 15A and 15B may include a member such as a switch that is different from a lever.

The controller 10 receives the first throttle signal and the second throttle signal. The controller 10 controls the rotational speed of the first engine 4A in accordance with the operating amount of the first throttle member 15A indicated by the first throttle signal. The controller 10 controls the rotational speed of the second engine 4B in accordance with the operating amount of the second throttle member 15B indicated by the second throttle signal. The controller 10 controls the first shift actuator 32A in accordance with the operating direction of the first throttle member 15A indicated by the first throttle signal. Accordingly, the direction of the thrust generated by the first propulsion device 3A is switched between the forward moving direction and the rearward moving direction. The controller 10 controls the second shift actuator 32B in accordance with the operating direction of the second throttle member 15B indicated by the second throttle signal. Accordingly, the direction of the thrust generated by the second propulsion device 3B is switched between the forward moving direction and the rearward moving direction.

As shown in FIG. 4, the watercraft 1 includes a first rotational speed sensor 33A, a second rotational speed sensor 33B, an angular sensor 51, ballast water amount sensors 52, and seat sensors 53. The controller 10 is connected to the first rotational speed sensor 33A, the second rotational speed sensor 33B, the angular sensor 51, the ballast water amount sensors 52, and the seat sensors 53 in a communicable manner.

The first rotational speed sensor 33A detects the rotational speed of the first engine 4A. The first rotational speed sensor 33A outputs a first rotational speed signal indicating the rotational speed of the first engine 4A to the controller 10. The second rotational speed sensor 33B detects the rotational speed of the second engine 4B. The second rotational speed sensor 33B outputs a second rotational speed signal indicating the rotational speed of the second engine 4B to the controller 10. The controller 10 determines the velocity of the watercraft 1 based on the first or second rotational speed signal. It should be noted that the controller 10 may not necessarily obtain the velocity of the watercraft 1 based on the first or second rotational speed signal. Alternatively, the controller 10 may obtain the velocity of the watercraft 1 based on the opening degree of the first throttle member 15A indicated by the first throttle signal transmitted thereto from the sensor 151 and the opening degree of the second throttle member 15B indicated by the second throttle signal transmitted thereto from the sensor 152. The controller 10 may obtain the velocity of the watercraft 1 by utilizing, for instance, a GPS (Global Positioning System).

The angular sensor 51 detects the pitch angle (γ) of the watercraft body 2. The angular sensor 51 outputs a pitch angle signal indicating the pitch angle γ of the watercraft body 2 to the controller 10. For example, an IMU (Inertial Measurement Unit) can be used as the angular sensor 51. FIGS. 6A and 6B are diagrams for explaining the pitch angle γ. FIG. 6A is a side view of the watercraft 1 in a stationary state. A straight line denoted by L1 extends in the back-and-forth direction while being superimposed on the watercraft 1 in the stationary state. As shown in FIG. 6B, the watercraft 1 tilts up to the bow side during navigation such that the straight line L1 tilts up to the front side. An angle defined by the straight line L1 and a horizontal line L0 is the pitch angle γ.

The ballast water amount sensors 52 are provided in the first, second, and third ballast water tanks 41, 42, and 43, respectively. Each ballast water amount sensor 52 detects the amount of water in each of the first, second, and third ballast water tanks 41, 42, and 43. Each ballast water amount sensor 52 includes, for instance, a water level sensor. Each ballast water amount sensor 52 outputs a ballast water amount signal indicating the amount of water in each ballast water tank 41, 42, 43 to the controller 10.

The seat sensors 53 are disposed in seats on the watercraft 1, respectively. Each seat sensor 53 detects whether a seat is occupied by people on board. When it is detected that a seat is occupied by people on board, a seat sensor 53 outputs a seating signal to the controller 10. The controller 10 is able to obtain the number of people on board and the locations of people on board in the watercraft 1 based on the seat signals.

When it is determined that the watercraft body 2 is intended to move straight forward based on the steering information, as shown in FIG. 5, the controller 10 controls the first steering actuator 31A such that the first direction D1 is inclined leftward with respect to the center of gravity of the watercraft 1 and also controls the second steering actuator 31B such that the second direction D2 is inclined rightward with respect to the center of gravity of the watercraft 1.

The controller 10 determines whether or not the watercraft body 2 is intended to move straight forward based on the steering signal (exemplary operating information) transmitted thereto from the sensor 140, the first throttle signal transmitted thereto from the sensor 151, and the second throttle signal transmitted thereto from the sensor 152. The controller 10 determines that the watercraft body 2 is intended to move straight forward, for instance, when the steering operation angle, obtained based on the operating amount indicated by the steering signal, falls in an absolute angular range from 0° to a predetermined threshold, while the operating directions of the first and second throttle members 15A and 15B, obtained based on the first and second throttle signals, are the forward moving directions. It should be noted that the term “straight” is used to refer to a direction extending along the back-and-forth direction of the watercraft 1. It should be noted that the range of the steering operation angle from 0 to the predetermined threshold is set as an angular range including a play or clearance and an error, for example, based upon social conventions, the watercraft 1 is considered as being oriented straight when the steering operation angle falls within the angular range.

The controller 10 stores the initial location (P0) of the center of gravity of the watercraft 1 (see FIG. 2). The initial location P0 of the center of gravity can be preliminarily set in a design phase of the watercraft 1. The controller 10 obtains the location of the center of gravity based on the pitch angle γ indicated by the pitch angle signal. The controller 10 stores a table indicating a relationship between the pitch angle and the location of the center of gravity. For example, when the pitch angle is increased during navigation of the watercraft 1, the location of the center of gravity is shifted rearward. In FIG. 2, the location of the center of gravity, shifted rearward from the initial location P0, is indicated by P1. Thus, the controller 10 can obtain the location of the center of gravity P1 when shifted from the initial location P0 based on the pitch angle signal inputted thereto.

The controller 10 may obtain the location of the center of gravity of the watercraft 1 based on the ballast water amount signals transmitted thereto from the ballast water amount sensors 52. The location of the center of gravity is shifted in the back-and-forth direction in accordance with the amount of ballast water. For example, when the first ballast water tank 41 contains a greater amount of water, whereas the second and third ballast water tanks 42 and 43 contain a lesser amount of water, the location of the center of gravity is shifted forward from the initial location P0. Contrarily, when the first ballast water tank 41 contains a lesser amount of water, whereas the second and third ballast water tanks 42 and 43 contain a greater amount of water, the location of the center of gravity is shifted rearward from the initial location P0.

The controller 10 may obtain the number of people on board and the locations of the people on board based on the seat signals transmitted thereto from the seat sensors 53, and then, may obtain the location of the center of gravity from the number of people on board and the locations of the people on board. For example, when the operator (and a passenger) is seated on the front-side seat (seats) but no one is seated on the rear-side seat, the location of the center of gravity is shifted forward from the initial location P0. It should be noted that, when the pitch angle γ cannot be detected by the angular sensor 51, the location of the center of gravity may be obtained based on both or either of the ballast water amount signals transmitted from the ballast water amount sensors 52 and the seat signals transmitted from the seat sensors 53.

The controller 10 obtains the pitch angle from the velocity of the watercraft 1 and determines whether or not the pitch angle detected by the angular sensor 51 is correct. When it is determined that the pitch angle detected by the angular sensor 51 is not correct, the controller 10 sets the initial location P0 as the location of the center of gravity without using the obtained center-of-gravity location based on the pitch angle detected by the angular sensor 51. The controller 10 stores a table indicating a relationship between the velocity and the pitch angle of the watercraft 1. The controller 10 obtains the velocity of the watercraft 1 as described above, and then, obtains the pitch angle of the watercraft 1 from the obtained velocity with reference to the table. The controller 10 compares the pitch angle obtained from the velocity and the pitch angle detected by the angular sensor 51, and when a difference between the pitch angles is greater than or equal to a predetermined amount, the controller 10 sets the initial location P0 as the location of the center of gravity without using the obtained center-of-gravity location based on the pitch angle γ detected by the angular sensor 51. The predetermined amount is set as an amount including not only an error of the angular sensor 51 but also an error of the pitch angle obtained from the velocity. It should be noted that, when the difference between the pitch angle obtained from the velocity and the pitch angle detected by the angular sensor 51 is greater than or equal to the predetermined amount, the location of the center of gravity may be obtained based on both or either of the ballast water amount signals transmitted from the ballast water amount sensors 52 and the seat signals transmitted from the seat sensors 53 without setting the initial location P0 as the location of the center of gravity.

When it is determined that the watercraft body 2 is intended to move straight forward based on the steering information, the controller 10 controls the first and second steering actuators 31A and 31B to set the first and second directions D1 and D2 such that a rotational moment acting about the obtained center-of-gravity location is closer to zero. Specifically, as shown in FIG. 5, the controller 10 controls the first steering actuator 31A such that the first direction D1 is inclined outward (to the port side) with respect to the back-and-forth direction. The controller 10 controls the second steering actuator 31B such that the second direction D2 is inclined outward (to the starboard side) with respect to the back-and-forth direction. As shown in FIG. 5, the first and second directions D1 and D2 are set such that the interval therebetween gradually increases in the rearward direction.

When it is determined that the watercraft body 2 is intended to move straight forward based on the steering information, the controller 10 may control the first and second steering actuators 31A and 31B to set the first and second directions D1 and D2 such that the rotational moment acting about the obtained center-of-gravity location is reduced or minimized.

For example, when it is determined that the watercraft body 2 is intended to move straight forward based on the steering information, as shown in a plan view of FIG. 7A, the controller 10 preferably controls the first steering actuator 31A such that the axis M1, corresponding to the first direction D1, intersects with the obtained center-of-gravity location (P1). When it is determined that the watercraft body 2 is intended to move straight forward based on the steering information, as shown in the plan view of FIG. 7A, the controller 10 preferably controls the second steering actuator 31B such that the axis M2, corresponding to the second direction D2, intersects with the obtained center-of-gravity location P1. Thus, when moving forward, the watercraft 1 provides good stability during straight movement by directing the first direction D1 of water jetted from the first nozzle deflector 6A outward and the second direction D2 of water jetted from the second nozzle deflector 6B outward. A direction along the axis M1 is exemplified as the axial direction of the first nozzle deflector, whereas a direction along the axis M2 is exemplified as the axial direction of the second nozzle deflector. It should be noted that, unlike the configuration shown in the diagram of FIG. 7A, the axes M1 and M2 may not be set to extend through the center-of-gravity location P1. More specifically, as long as the axes M1 and M2 are set such that the rotational moment acting about the center-of-gravity location P1 is small in magnitude, the watercraft 1 can provide good stability during straight movement.

The controller 10 sets the first and second directions D1 and D2 such that each nozzle angle α, β, defined with respect to the back-and-forth direction M0, is reduced as the center-of-gravity location P1 is shifted forward.

Similarly to the above, when the watercraft body 2 is moved straight rearward, the controller 10 may control the first steering actuator 31A such that the first direction D1 is inclined leftward and may control the second steering actuator 31B such that the second direction D2 is inclined rightward. In other words, when the watercraft body 2 is moved rearward by operating the remote controller 15, after having moved forward with the first direction D1 inclined leftward with respect to center of gravity of the watercraft 1 and the second direction D2 inclined rightward with respect to center of gravity of the watercraft 1, the first and second directions D1 and D2 may be set identical to those when forwardly moving the watercraft body 2.

FIG. 8A is a diagram showing a chart of a relationship between the angle of steering operation by the steering member 14 and the nozzle angle. In FIG. 8A, the horizontal axis indicates the angle of steering operation by the steering member 14. The origin on the horizontal axis is a neutral position of the steering member 14. On the other hand, the negative side of the origin on the horizontal axis indicates the steering operation angle to the port side, whereas the positive side of the origin on the horizontal axis indicates the steering operation angle to the starboard side. When the steering operation angle increases in absolute value on the negative side, this indicates that the steering member 14 is greatly operated leftward. Contrarily, when the steering operation angle increases in absolute value on the positive side, this indicates that the steering member 14 is greatly operated rightward. In FIG. 8A, the vertical axis indicates the nozzle angle. The origin on the vertical axis indicates a condition that the nozzle angle is zero, i.e., a condition that the first and second directions D1 and D2 extend along the back-and-forth direction M0. The positive side of the origin on the vertical axis indicates the magnitude of the nozzle angle to the port side, whereas the negative side of the origin on the vertical axis indicates the magnitude of the nozzle angle to the starboard side. When the nozzle angle increases in absolute value on the positive side, this indicates that the nozzle angle increases to the port side. Contrarily, when the nozzle angle increases in absolute value on the negative side, this indicates that the nozzle angle increases to the starboard side. A first line g1 indicates a change in the nozzle angle α of the first nozzle deflector 6A with respect to the steering operation angle, whereas a second line g2 indicates a change in the nozzle angle β of the second nozzle deflector 6B with respect to the steering operation angle.

As shown in the diagram of FIG. 8A, when a target steering operation angle, i.e., a target steering angle for the operation of the steering member 14, is an angle to the port side (the negative side angle on the horizontal axis), the controller 10 controls the first and second steering actuators 31A and 31B to drive only the second nozzle deflector 6B and not the first nozzle deflector 6A in an angular range from 0° to −θ1° (exemplary predetermined threshold), in other words, an absolute angle of an angular range from 0° to θ1°.

It is assumed that during forward movement, the nozzle angle α is C°, whereas the nozzle angle β is −C°. FIG. 8B is a schematic diagram showing a condition of the first and second directions D1 and D2 made when the angle of steering operation by the steering member 14 is 0° during forward movement. As shown in FIG. 8B, in the present example embodiment, the first and second directions D1 and D2 are inclined outward in accordance with the center-of-gravity location P1 so as to provide the watercraft 1 with good stability during straight movement.

FIG. 8C is a schematic diagram showing a condition of the first and second directions D1 and D2 when the steering operation angle reaches −θ2° (see FIG. 8A) by operating the steering member 14 leftward during forward movement. When the steering operation angle is −θ2°, the nozzle angle α of the first nozzle deflector 6A is kept constant. Thus, the first direction D1 of the first nozzle deflector 6A is not changed and only the nozzle angle β of the second nozzle deflector 6B is changed. When the steering operation angle is −θ2°, the nozzle angle β of the second nozzle deflector 6B is 0°. Thus, the second direction D2 extends along the back-and-forth direction.

FIG. 8D is a schematic diagram showing a condition of the first and second directions D1 and D2 when the steering operation angle reaches −θ1° (see FIG. 8A) by operating the steering member 14 leftward during forward movement. When the steering operation angle is −θ1°, the nozzle angle α of the first nozzle deflector 6A is kept constant. Thus, the first direction D1 of the first nozzle deflector 6A is not changed and only the nozzle angle β of the second nozzle deflector 6B is changed. When the steering operation angle is −θ1°, the nozzle angle β of the second nozzle deflector 6B is C°. Thus, the second direction D2 is parallel or substantially parallel to the first direction D1.

FIG. 8E is a schematic diagram showing a condition of the first and second directions D1 and D2 when the steering operation angle reaches −θ3° (see FIG. 8A) by operating the steering member 14 leftward during forward movement. When the steering operation angle is −θ3°, the nozzle angle α of the first nozzle deflector 6A and the nozzle angle β of the second nozzle deflector 6B are both changed in a similar manner.

As described above, the first nozzle deflector 6A is inclined outward during forward movement. Thus, when the target steering angle by the steering member 14 is an angle to the port side, only the second nozzle deflector 6B is driven and not the first nozzle deflector 6A in a range from 0° to −θ1°.

It should be noted that, even during starboard-side steering, when the target steering angle by the steering member 14 is an angle to the starboard side (the positive side on the horizontal axis), the controller 10 controls the first and second steering actuators 31A and 31B in a similar manner to port-side steering such that only the first nozzle deflector 6A is driven and not the second nozzle deflector 6B in an angular range of from 0° to +θ1° (exemplary predetermined threshold), in other words, an absolute angular range from 0° to θ1°.

A method of controlling a watercraft will be hereinafter explained. FIG. 9 is a flowchart showing a method of controlling a watercraft.

In step S10, the controller 10 determines whether or not the watercraft body 2 is intended to move straight forward based on the steering information. The controller 10 determines whether or not the watercraft body 2 is intended to move straight forward based on the steering signal transmitted thereto from the sensor 140, the first throttle signal transmitted thereto from the sensor 151, and the second throttle signal transmitted thereto from the sensor 152.

In step S10, when it is not determined that the watercraft body 2 is intended to move straight forward, the control process stands by until the controller 10 determines that the watercraft body 2 is intended to move straight forward.

When it is determined that the watercraft body 2 is intended to move straight forward, the controller 10 obtains the location of the center of gravity of the watercraft 1 in step S11. For example, the controller 10 calculates the center-of-gravity location P1 based on the pitch angle signal transmitted thereto from the angular sensor 51, the ballast water amount signals transmitted thereto from the ballast water amount sensors 52, and the seat signals transmitted thereto from the seat sensors 53.

Next, in step S12, the controller 10 detects the velocity of the watercraft 1. For example, the controller 10 obtains the velocity of the watercraft 1 based on the first rotational speed signal transmitted thereto from the first rotational speed sensor 33A and the second rotational speed signal transmitted thereto from the second rotational speed sensor 33B. Alternatively, the controller 10 may obtain the velocity of the watercraft 1 based on the first throttle signal transmitted thereto from the sensor 151 and the second throttle signal transmitted thereto from the sensor 152.

Next, in step S13, the controller 10 compares the pitch angle obtained based on the velocity and the pitch angle detected by the angular sensor 51 and determines whether or not a difference therebetween is greater than or equal to a predetermined amount.

When it is determined that the difference is greater than or equal to the predetermined amount in step S13, the controller 10 uses the initial location P0 as the location of the center of gravity of the watercraft 1 in step S14.

On the other hand, when it is determined that the difference is less than the predetermined amount in step S13, the controller 10 uses the center-of-gravity location obtained in step S11 as the location of the center of gravity of the watercraft 1 in step S15.

Next, in step S16, as shown in FIG. 5, the controller 10 controls the first and second steering actuators 31A and 31B with respect to the center of gravity so as to set the first and second directions D1 and D2 such that a rotational moment acting about the used center of gravity is closer to zero.

In the watercraft 1 according to the example embodiments explained above, when it is determined that the watercraft body 2 is intended to move straight forward, the first direction D1 of water jetted from the first nozzle deflector 6A is oriented to the rear left side with respect to the center of gravity of the watercraft 1, whereas the second direction D2 of water jetted from the second nozzle deflector 6B is oriented to the rear right side with respect to the center of gravity of the watercraft 1. Thus, the direction of water jetted from the first nozzle deflector 6A and the direction of water jetted from the second nozzle deflector 6B can be set in consideration of the center of gravity of the watercraft 1. Thus, the watercraft 1 provides good stability during straight movement.

Example embodiments of the present invention have been explained above. However, the present invention is not limited to the example embodiments described above, and a variety of changes can be made without departing from the gist of the present invention.

The watercraft 1 is not limited to the jet boat, alternatively the watercraft 1 may be of another type such as a watercraft equipped with an outboard motor. The number of propulsion devices installed in the watercraft 1 is not limited to two, alternatively the number of propulsion devices may be less than or greater than two. The propulsion devices installed in the watercraft 1 are not limited to the jet propulsion devices, alternatively the propulsion devices may be of another type such as outboard motors. The watercraft 1 may include a side thruster.

In the example embodiments described above, the watercraft 1 uses the remote controller 15 as an exemplary throttle member. However, the throttle member is not limited to the remote controller 15, alternatively the throttle member may be a joystick lever, a switch, or so forth.

In the example embodiments described above, the watercraft 1 is provided with the seat sensors 53 as an exemplary number-of-people-on-board detector and an exemplary location-of-people-on-board detector. However, the number-of-people-on-board detector and the location-of-people-on-board detector may not be limited to the seat sensors 53. For example, the watercraft 1 may be provided with an imaging device such as a camera. In this case, the controller 10 may analyze data of images taken by the imaging device so as to obtain the number of people on board and the positions of people on board. Alternatively, the watercraft 1 may be provided with an input device to allow the operator to input the number of people on board and the positions of people on board.

In the example embodiments described above, the watercraft 1 is provided with the first engine 4A (exemplary first drive source) that is an internal combustion engine, and the second engine 4B (exemplary second drive source) that is an internal combustion engine. However, the first and second drive sources may not be limited to the first and second engines 4A and 4B, alternatively the first and second drive sources may be electric machines such as electric motors.

According to example embodiments of the present invention, it is possible for a watercraft to easily provide good stability during straight movement even when the watercraft is propelled with a jet of water.

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 watercraft to be propelled by a jet of water, the watercraft comprising: a watercraft body;a first jet propulsion device attached to a port side of a rear portion of the watercraft body, and including a first nozzle deflector to jet water and be swingable right and left;a second jet propulsion device attached to a starboard side of the rear portion of the watercraft body and symmetrical to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body, the second jet propulsion device including a second nozzle deflector to jet water and be swingable right and left;a first actuator to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector;a second actuator to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector;a steering sensor to detect steering information regarding steering of the watercraft body; anda controller configured or programmed to control the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft and also to control the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.

2. The watercraft according to claim 1, wherein the controller is configured or programmed to set the first direction and the second direction such that a rotational moment acting about the center of gravity is closer to zero.

3. The watercraft according to claim 1, wherein the controller is configured or programmed to set the first direction and the second direction such that an axial direction of the first nozzle deflector and an axial direction of the second nozzle deflector are oriented toward the center of gravity in a plan view of the watercraft.

4. The watercraft according to claim 1, wherein the controller is configured or programmed to set the first direction and the second direction such that an angle between each of the first direction and the second direction and the back-and-forth direction is reduced as the center of gravity is located farther forward on the watercraft.

5. The watercraft according to claim 1, further comprising: a steering on the watercraft body and operable by an operator of the watercraft to change a steering angle of the watercraft; whereinthe steering sensor is operable to detect an angle of a steering operation by the steering; andthe controller is configured or programmed to determine that the watercraft body is intended to move straight forward when the angle of steering operation falls within an absolute angular range from 0° to a predetermined threshold.

6. The watercraft according to claim 1, further comprising: an angular sensor to detect a pitch angle of the watercraft body; whereinthe controller is configured or programmed to obtain a location of the center of gravity based on the pitch angle of the watercraft body.

7. The watercraft according to claim 1, further comprising: a ballast water amount sensor to detect an amount of ballast water in a ballast water tank on or in the watercraft body; whereinthe controller is configured or programmed to obtain a location of the center of gravity based on the amount of ballast water.

8. The watercraft according to claim 7, wherein the controller is configured or programmed to obtain the location of the center of gravity based on the amount of ballast water and a location of the ballast water tank.

9. The watercraft according to claim 1, further comprising: a number-of-people-on-board detector to detect a number of people on board the watercraft body; whereinthe controller is configured or programmed to obtain a location of the center of gravity based on the number of people on board the watercraft body.

10. The watercraft according to claim 1, further comprising: a location-of-people-on-board detector to detect locations of people on board the watercraft body; whereinthe controller is configured or programmed to obtain a location of the center of gravity based on the locations of people on board the watercraft body.

11. The watercraft according to claim 6, further comprising: a storage to store an initial location of the center of gravity; anda velocity-related information detector to detect information related to a velocity of the watercraft; whereinthe controller is configured or programmed to use the initial location of the center of gravity without using the location of the center of gravity obtained based on the pitch angle when a difference between the pitch angle obtained from the detected velocity and the pitch angle detected by the angular sensor is greater than or equal to a predetermined amount.

12. The watercraft according to claim 11, further comprising: a throttle to regulate a thrust generated by each of the first jet propulsion device and the second jet propulsion device; whereinthe velocity-related information detector includes an opening degree sensor to detect an opening degree of the throttle; andthe controller is configured or programmed to obtain the velocity based on the opening degree of the throttle.

13. The watercraft according to claim 11, wherein the first jet propulsion device includes a first drive source;the second jet propulsion device includes a second drive source;the velocity-related information detector includes a rotational speed sensor to detect a rotational speed of the first drive source or the second drive source; andthe controller is configured or programmed to obtain the velocity based on the rotational speed of the first drive source or the second drive source.

14. The watercraft according to claim 1, wherein the controller is configured or programmed to obtain a target steering angle based on the steering information;when the target steering angle is an angle to the port side, the controller is configured or programmed to drive only the second nozzle deflector and not the first nozzle deflector within an absolute angular range from 0° to a predetermined threshold; andwhen the target steering angle is an angle to the starboard side, the controller is configured or programmed to drive only the first nozzle deflector and not the second nozzle deflector within the absolute angular range of steering operation from 0° to the predetermined threshold.

15. The watercraft according to claim 1, further comprising: a throttle to switch between forward movement and rearward movement by each of the first and second jet propulsion devices; anda position-of-throttle detector to detect a position of the throttle; whereinthe controller is configured or programmed to control the first actuator such that the first direction is inclined leftward and also control the second actuator such that the second direction is inclined rightward when it is determined that the watercraft body is intended to move straight rearward based on the position of the throttle and the steering information.

16. A method of controlling a watercraft including a watercraft body, a first jet propulsion device attached to a port side of a rear portion of the watercraft body and including a first nozzle deflector to jet water and swingable right and left, a second jet propulsion device attached to a starboard side of the rear portion of the watercraft body symmetrically to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body and including a second nozzle deflector to jet water and swingable right and left, a first actuator to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector, and a second actuator to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector, the method comprising: detecting when the watercraft body is intended to move straight forward based on information regarding steering of the watercraft body; andcontrolling the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft, and also controlling the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is detected that the watercraft body is intended to move straight forward.

17. A watercraft comprising: a watercraft body; anda first propulsion device attached to a port side of the watercraft body to generate a thrust by jetting water therefrom;a second propulsion device attached to a starboard side of the watercraft body symmetrically to the first propulsion device with respect to a back-and-forth direction of the watercraft body to generate a thrust by jetting water therefrom;a direction changer to change a first direction of the water jetted from the first propulsion device and a second direction of the water jetted from the second propulsion device;a steering sensor to detect steering information regarding steering of the watercraft body; anda controller configured or programmed to control the direction changer to incline the first direction leftward with respect to a center of gravity of the watercraft and incline the second direction rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.