Propulsion system for vessel

Abstract

This propulsion system for a vessel includes at least a first propulsion machine and a second propulsion machine that are provided side by side in a leftward-rightward direction in a hull, and a control unit including at least a processor and a memory and controlling the first propulsion machine and the second propulsion machine, wherein the control unit is capable of executing intermittent control to intermittently vary thrust of at least one propulsion machine of the first propulsion machine and the second propulsion machine on the basis of a first condition for varying a vessel speed, and wherein, during an intermittent driving mode in which at least one of the propulsion machines operates under the intermittent control, the control unit is capable of executing switching control to make thrust of the first propulsion machine and thrust of the second propulsion machine different from each other on the basis of a turning direction.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority based on Japanese Patent Application No. 2025-052655, filed Mar. 26, 2025, the content of which is incorporated herein by reference.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present disclosure relates to a propulsion system for a vessel.Description of Related Art

[0003] In recent years, efforts to provide access to sustainable transportation systems that consider vulnerable people among transportation participants have intensified. For the development of the sustainable transportation systems, research and development is progressing to further improve the safety and convenience of transportation, for example, through driving assistance of a vessel. As a type of driving assistance of a vessel, a configuration in which a shift position of an outboard motor is automatically switched to allow the vessel to sail at a very low speed (so-called auto-shift control) is known. For example, Japanese U.S. Pat. No. 6,156,926 discloses a configuration in which the shift position is switched between a forward position and a neutral position, or between a reverse position and a neutral position, at predetermined time intervals.SUMMARY OF THE INVENTION

[0004] However, in the related art, there is still room for improvement in responsiveness during turning in a case of changing a course of a vessel during auto-shift control.

[0005] The present disclosure provides a propulsion system for a vessel that can improve responsiveness during turning. The present disclosure will further contribute to the development of sustainable transportation systems.

[0006] In order to achieve the above object, a propulsion system for a vessel according to the present disclosure employs the following configurations.

[0007] (1) According to an aspect of the present disclosure, there is provided a propulsion system for a vessel including at least a first propulsion machine and a second propulsion machine that are provided side by side in a leftward-rightward direction in a hull, and a control unit including at least a processor and a memory and controlling the first propulsion machine and the second propulsion machine, wherein the control unit is capable of executing intermittent control to intermittently vary a thrust of at least one propulsion machine of the first propulsion machine and the second propulsion machine on the basis of a first condition for varying a vessel speed, and wherein, during an intermittent driving mode in which at least one of the propulsion machines operates under the intermittent control, the control unit is capable of executing switching control to make a thrust of the first propulsion machine and a thrust of the second propulsion machine different from each other on the basis of a turning direction.

[0008] (2) In the aspect (1) above, when, of the first propulsion machine and the second propulsion machine, the propulsion machine located on an outer side in the turning direction of the hull is referred to as an outer propulsion machine, and the propulsion machine located on an inner side in the turning direction of the hull is referred to as an inner propulsion machine, in the switching control, the control unit may set a thrust of the outer propulsion machine to be greater than a thrust of the inner propulsion machine.

[0009] (3) In the aspect (2) above, in the switching control, the control unit may execute the intermittent control on the outer propulsion machine and may set the thrust of the inner propulsion machine to zero.

[0010] (4) In the aspect (2) above, in the switching control, the control unit may cause the outer propulsion machine to continuously generate the thrust and may execute the intermittent control on the inner propulsion machine.

[0011] (5) In the aspect (1) above, in the switching control, the control unit may execute the intermittent control on one propulsion machine of the first propulsion machine and the second propulsion machine, and may control the thrust of the other propulsion machine on the basis of a second condition that is different from the first condition.

[0012] (6) In the aspect (1) above, the control unit may perform the switching control in a case in which a steering command value in the turning direction is equal to or greater than a steering angle threshold value.

[0013] (7) In the aspect (6) above, the steering angle threshold value may include a right steering angle threshold value at which a course of the hull is changed to a right side with respect to a straight-ahead direction, and a left steering angle threshold value at which a course of the hull is changed to a left side with respect to a straight-ahead direction.

[0014] (8) In the aspect (1) above, the first condition may be a vessel speed, and the intermittent control may switch a shift position of at least one of the propulsion machines from a forward position to a neutral position in a case in which the vessel speed is equal to or greater than a first speed threshold value, and may switch the shift position from a neutral position to a forward position in a case in which the vessel speed is equal to or less than a second speed threshold value that is lower than the first speed threshold value.

[0015] (9) In the aspect (1) above, the first condition may be a shift switching cycle that is set by combining a forward set time during which a forward position is continued and a neutral set time during which a neutral position is continued, and the intermittent control may switch a shift position of the propulsion machine between a forward position and a neutral position on the basis of the shift switching cycle.

[0016] (10) The aspect (2) above may further include a central propulsion machine provided between the first propulsion machine and the second propulsion machine, wherein, in the switching control, the control unit may control a thrust of the central propulsion machine in accordance with the outer propulsion machine.

[0017] (11) The aspect (1) above may further include a third propulsion machine provided between the first propulsion machine and the second propulsion machine, and a fourth propulsion machine provided in a portion located close to the second propulsion machine in the leftward-rightward direction with respect to the third propulsion machine, wherein, in the switching control, the control unit may control a thrust of the third propulsion machine in accordance with the first propulsion machine, and may control a thrust of the fourth propulsion machine in accordance with the second propulsion machine.

[0018] (12) In the aspect (1) above, during the intermittent driving mode, the control unit may control the first propulsion machine and the second propulsion machine such that orientations of the thrust of the first propulsion unit and the thrust of the second propulsion unit are the same direction.

[0019] According to the aspects of the present disclosure, it is possible to improve responsiveness during turning.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a plan view of a vessel according to a first embodiment.

[0021] FIG. 2 is a side view of a propulsion machine according to the first embodiment.

[0022] FIG. 3 is a block diagram of the vessel according to the first embodiment.

[0023] FIG. 4 is a state transition diagram showing switching between a normal driving mode and an intermittent driving mode in the vessel according to the first embodiment.

[0024] FIG. 5 is a flowchart illustrating a switching operation between the intermittent driving mode and the normal driving mode in the vessel according to the first embodiment.

[0025] FIG. 6 is a flowchart illustrating intermittent control (auto-shift control) during the intermittent driving mode in the vessel according to the first embodiment.

[0026] FIG. 7 is a flowchart illustrating the operation of a propulsion system based on a steering command during the intermittent driving mode in the vessel according to the first embodiment.

[0027] FIG. 8 is a plan view of the vessel in a left intermittent state.

[0028] FIG. 9 is a view showing a steering angle threshold value θa.

[0029] FIG. 10 is a plan view of the vessel in a right intermittent state.

[0030] FIG. 11 is a flowchart for explaining a switching operation (switching control) of each propulsion machine in response to a steering flag.

[0031] FIG. 12 is a timing chart for explaining the operation of the vessel according to the first embodiment.

[0032] FIG. 13 is a plan view of the vessel during left turning.

[0033] FIG. 14 is a plan view of the vessel during right turning.

[0034] FIG. 15 is a plan view of a vessel according to a second embodiment.

[0035] FIG. 16 is a state transition diagram during the intermittent driving mode in the vessel of the second embodiment.

[0036] FIG. 17 is a state transition diagram during the intermittent driving mode in a vessel of a third embodiment.

[0037] FIG. 18 is a plan view of a vessel according to a fourth embodiment.

[0038] FIG. 19 is a state transition diagram during the intermittent driving mode in a vessel of a fifth embodiment.

[0039] FIG. 20 is a flowchart for explaining a switching operation (switching control) of each propulsion machine in response to a steering flag in the vessel of the fifth embodiment.

[0040] FIG. 21 is a plan view of the vessel in a right continuation state.

[0041] FIG. 22 is a plan view of the vessel in a left continuation state.

[0042] FIG. 23 is a timing chart for explaining the operation of a propulsion system in the vessel according to the fifth embodiment.

[0043] FIG. 24 is a state transition diagram during the intermittent driving mode in a vessel according to a sixth embodiment.

[0044] FIG. 25 is a flowchart for explaining a switching operation of each propulsion machine in response to a speed flag and a steering flag.

[0045] FIG. 26 is a state transition diagram during the intermittent driving mode in a vessel according to a seventh embodiment.

[0046] FIG. 27 is a flowchart for explaining a switching operation of each propulsion machine in response to a speed flag and a steering flag.

[0047] FIG. 28 is a timing chart for explaining the operation of a propulsion system in a vessel according to an eighth embodiment.DESCRIPTION OF EMBODIMENTS

[0048] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the embodiments and modification examples which will be described below, the same reference numerals may be used to designate corresponding components, and the description thereof may be omitted. In the following description, expressions indicating relative or absolute arrangement, such as “parallel,”“orthogonal,”“center,” and “coaxial,” not only indicate such an arrangement strictly, but also indicate a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. In addition, in the present embodiment, “facing each other” does not necessarily mean that orthogonal directions (normal directions) of two surfaces are aligned with each other, but also means that the orthogonal directions intersect with each other.

[0049] Forward, rearward, upward, downward, leftward, and rightward directions in the following description correspond to orientations of a vessel 1. In this case, an arrow FR in the drawing indicates a forward direction of the vessel 1, the arrow UP in the drawing indicates an upward direction of the vessel 1, and the arrow LH in the drawing indicates a leftward direction of the vessel 1. In addition, a center line CL indicates a center position of the vessel 1 in a leftward-rightward direction (width direction).First EmbodimentVessel 1

[0050] FIG. 1 is a plan view of the vessel 1 according to a first embodiment.

[0051] The vessel 1 shown in FIG. 1 includes a hull 2, a plurality of propulsion machines 3, a steering angle input unit 4, a thrust input unit 5, a vessel speed sensor 6 (see FIG. 3), an operation unit 7, and a control unit 8. The plurality of propulsion machines 3 and the control unit 8 constitute a propulsion system in the present embodiment.Propulsion Machine 3

[0052] The propulsion machines 3 include a right propulsion machine 3a provided on a right side (STBD side) of a stern with respect to the center line CL, and a left propulsion machine 3b provided on a left side (PORT side) of the stern with respect to the center line CL. In other words, the vessel 1 of the present embodiment is a so-called two-machine small vessel in which two propulsion machines 3 (a right propulsion machine 3a and a left propulsion machine 3b) are provided at both left and right end portions of the stern with respect to the center line CL. In the following description, in a case in which there is no need to distinguish between the propulsion machines 3a and 3b, they will be collectively referred to as the propulsion machine 3. The right propulsion machine 3a and the left propulsion machine 3b are examples of an outer propulsion machine and an inner propulsion machine.

[0053] FIG. 2 is a side view of the propulsion machine 3. FIG. 3 is a block diagram of the vessel 1.

[0054] As shown in FIGS. 2 and 3, the propulsion machine 3 is, for example, an outboard motor. The propulsion machine 3 includes a casing 11, a drive source 12, a drive shaft 13, a propulsion unit 14, and a shift switching mechanism 15.

[0055] The casing 11 is attached to a bracket 9 provided at the stern via a steering shaft 16 (swivel shaft) extending in an upward-downward direction. The propulsion machine 3 is attached to the hull 2 so as to be rotatable in a yaw direction around the steering shaft 16 by the operation of a steering actuator 17 (see FIG. 3).

[0056] The drive source 12 is, for example, an internal combustion engine. The drive source 12 is housed in an upper portion of the casing 11 in a state in which a crankshaft is aligned in the upward-downward direction. The power of the drive source 12 (rotation speed of the engine) is set on the basis of an opening degree of a throttle valve. The throttle valve is driven by the operation of a throttle actuator 18 (see FIG. 3).

[0057] The drive shaft 13 transmits the power generated by the drive source 12 to the propulsion unit 14 via the shift switching mechanism 15. The drive shaft 13 extends in the upward-downward direction within the casing 11. An upper end portion of the drive shaft 13 is connected to the drive source 12.

[0058] The propulsion unit 14 includes a propeller shaft 21 and a propeller 22.

[0059] The propeller shaft 21 is provided at a lower end portion of the casing 11 so as to be rotatable about an axis extending in a forward-rearward direction. A front end portion of the propeller shaft 21 is connected to the shift switching mechanism 15 inside the casing 11.

[0060] The propeller 22 is provided at a rear end portion of the propeller shaft 21 in a state in which the propeller 22 protrudes outside the casing 11. The propeller 22 rotates integrally with the propeller shaft 21.

[0061] The shift switching mechanism 15 includes a drive gear 25, a forward gear 26, a reverse gear 27, and a clutch 28.

[0062] The drive gear 25 is provided at a lower end portion of the drive shaft 13. The drive gear 25 is rotatable integrally with the drive shaft 13.

[0063] The forward gear 26 and the reverse gear 27 are rotatably provided on the propeller shaft 21 at positions facing each other in the forward-rearward direction with the drive gear 25 sandwiched therebetween. The forward gear 26 and the reverse gear 27 are engaged with the drive gear 25. The forward gear 26 and the reverse gear 27 rotate in opposite directions as the drive gear 25 rotates.

[0064] The clutch 28 switches between a power connection state and a power disconnection state between the forward gear 26 or the reverse gear 27 and the propeller shaft 21. The clutch 28 is provided on the propeller shaft 21 at a portion thereof located between the forward gear 26 and the reverse gear 27 so as to be rotatable integrally with the propeller shaft 21. The clutch 28 is provided so as to be movable in the forward-rearward direction along the propeller shaft 21 by the operation of a shift actuator 29. When the clutch 28 is engaged with the forward gear 26, a rotational force of the forward gear 26 can be transmitted to the propeller shaft 21 (forward position F). As a result, the propeller 22 rotates in a normal direction, and thus a thrust in a forward direction is applied to the vessel 1. When the clutch 28 is engaged with the reverse gear 27, a rotational force of the reverse gear 27 can be transmitted to the propeller shaft 21 (reverse position R). As a result, the propeller 22 rotates in a reverse direction, and thus a thrust in a reverse direction is applied to the vessel 1. On the other hand, in a state in which the clutch 28 is not engaged with either the forward gear 26 or the reverse gear 27, no rotational force is transmitted to the propeller shaft 21 (neutral position N).Steering angle input unit 4

[0065] As shown in FIGS. 1 and 3, the steering angle input unit 4 is provided in a cockpit of the hull 2. The steering angle input unit 4 is, for example, a steering wheel that is provided so as to be rotatable leftward and rightward. The steering angle input unit 4 receives a user's operation when changing a course of the vessel 1 (hull 2). That is, the steering angle input unit 4 receives an operation to change an orientation of the thrust of the propulsion machine 3 around the yaw direction. In a case in which the outboard motor is used as the propulsion machine 3 as in the present embodiment, the orientation of the thrust of the propulsion machine 3 is a steering angle θ. The steering angle θ is an angle of inclination of the propulsion machine 3 around the yaw direction with respect to the center line CL in a plan view. In the present embodiment, the steering angle θ of the propulsion machine 3 in a state in which the propeller shaft 21 is parallel to the center line CL in a plan view (in a state in which the orientation of the thrust of each propulsion machine 3 is parallel to the forward-rearward direction of the hull 2) is taken as a reference position (0°).

[0066] The amount of rotation operation of the steering angle input unit 4 is detected by a steering angle sensor 31. The steering angle sensor 31 outputs a detection signal based on the amount of operation of the steering angle input unit 4 to the control unit 8 as a steering command value θm. The steering angle input unit 4 may be a joystick other than a steering wheel, or may be mounted as a switch or the like of the operation unit 7. In the present embodiment, the propulsion machine 3 has been described using the outboard motor as an example, but the present disclosure is not limited to this configuration. The propulsion machine may be an inboard motor, an inboard-outboard motor, a water jet motor, or the like, in addition to the outboard motor. For example, in the case of the inboard motor, the orientation of the thrust of the propulsion machine 3 may be changed by changing an orientation of a separately provided rudder. For example, in the case of the water jet motor, the orientation of the thrust of the propulsion machine 3 may be changed by changing an orientation of a water flow. In addition, the propulsion machine 3 may be formed by combining an outboard motor and a side thruster. In this case, the orientation of the thrust of the propulsion machine 3 may be changed depending on the ratio of the thrust of the outboard motor and the thrust of the side thruster.Thrust input unit 5

[0067] The thrust input unit 5 is provided in the cockpit of the hull 2. The thrust input unit 5 is, for example, a throttle lever (accelerator lever). The thrust input unit 5 receives the user's operation when the thrust (required thrust Sd) of the vessel 1 or the shift position (required shift position) of the propulsion machine 3 is changed. The thrust input unit 5 is configured to be capable of reciprocating movement by rotation, sliding, or the like. The thrust input unit 5 is capable of reciprocating movement within an operation region in which three shift regions of a forward position F, a neutral position N, and a reverse position R are arranged.

[0068] In the vessel 1, the required shift position can be set according to the position of the thrust input unit 5 with respect to the operation region. That is, in a case in which the thrust input unit 5 is located in the shift region of the forward position F, a request can be made to the control unit 8 to set the shift position to the forward position F. In a case in which the thrust input unit 5 is located in the shift region of the neutral position N, a request can be made to the control unit 8 to set the shift position to the neutral position N. In a case in which the thrust input unit 5 is located in the shift region of the reverse position R, a request can be made to the control unit 8 to set the shift position to the reverse position R.

[0069] In the vessel 1, the required thrust Sd can be set according to the position of the thrust input unit 5 with respect to the operation region. That is, in a case in which the thrust input unit 5 is located in the shift region of the neutral position N, a request can be made to the control unit 8 to set the thrust to zero. In a case in which the thrust input unit 5 is set in the shift region of the forward position F or the reverse position R, a request can be made to the control unit 8 to increase the thrust in the corresponding direction of traveling as the thrust input unit 5 moves away from the shift region of the neutral position N. The position of the thrust input unit 5 (lever opening degree LE) is detected by a position sensor 32. The position sensor 32 outputs a detection signal based on the position of the thrust input unit 5 (lever opening degree LE) to the control unit 8.Vessel Speed Sensor 6

[0070] As shown in FIG. 3, the vessel speed sensor 6 detects the speed V of the vessel 1 (vessel speed). The vessel speed sensor 6 receives positioning signals from positioning satellites such as a global positioning system (GPS), measures the absolute position (latitude, longitude) of the vessel 1 on the basis of the received positioning signals, and calculates the vessel speed (vessel speed with respect to the ground) V on the basis of the time-series positioning results. The vessel speed sensor 6 may be an acoustic or electromagnetic sensor that detects the vessel speed (vessel speed with respect to the water) V of the vessel 1. The vessel speed sensor 6 may estimate the vessel speed V on the basis of the rotation speed of the engine. The speed sensor 6 may be a combination of a plurality of sensors described above.Operation Unit 7

[0071] The operation unit 7 receives various operations in the vessel 1. The operation unit 7 is configured to be manually operated by the user, as a multi function display (MFD) or the like, for example. The operation unit 7 may be an external device such as a mobile terminal connected to the vessel 1 by wire or wirelessly.

[0072] FIG. 4 is a state transition diagram showing switching between a normal driving mode and an intermittent driving mode.

[0073] As shown in FIG. 4, the vessel 1 of the present embodiment can be switched between an intermittent driving mode (auto-shift mode) and a normal driving mode (normal navigation mode) in response to the operation of the thrust input unit 5, for example.

[0074] The intermittent driving mode is a mode in which the vessel 1 is allowed to sail in a very low speed range within a predetermined speed range (for example, approximately 2 km / h to 4 km / h or even lower). The intermittent driving mode is applied in a case in which the required thrust Sd is equal to or less than the thrust output at the minimum output value (rotation speed during idling) of the drive source 12, for example. In the intermittent driving mode, for example, when the vessel 1 is moving forward (the required shift position is the forward position F), intermittent control is executed. In the intermittent control, the shift position is automatically switched between the forward position F and the neutral position N. As a result, in the intermittent driving mode, the vessel 1 can be allowed to sail at a vessel speed V that can be realized with the thrust output at the minimum output value of the drive source 12 or less.

[0075] The normal driving mode is a mode in which the vessel 1 is allowed to sail in a speed range other than the very low speed range (normal speed range). The normal driving mode is applied in a case in which the required thrust Sd is greater than the thrust output at the minimum output value of the drive source 12, for example. In the normal driving mode, for example, when the vessel 1 is moving forward, the output (throttle opening degree φ) of the drive source 12 is adjusted according to the position of the thrust input unit 5 (lever opening degree LE), and thus the thrust generated by the propulsion machine 3 is adjusted. In the present embodiment, whether the switching control between the intermittent driving mode and the normal driving mode is enabled (auto shift ON) or disabled (auto shift OFF) can be selected, for example, by the operation of the operation unit 7 (on / off operation).Control Unit 8

[0076] The control unit 8 comprehensively controls the operation of the vessel 1 (propulsion machine 3). That is, the control unit 8 is an example of a control device. The control unit 8 is one or a plurality of electronic control devices that are provided in the vessel 1. The control unit 8 is realized, for example, by a hardware processor such as a central processing unit (CPU) executing a program (software) stored in a read only memory (ROM), a random access memory (RAM), or the like. Some or all of these components may be realized by hardware (including circuitry) such as a large scale integration (LSI), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a graphics processing unit (GPU), and a system on chip (SOC), or may be realized by a combination of software and hardware.

[0077] The control unit 8 includes a storage unit 60, an acquisition unit 61, a determination unit 62, and a drive processing unit 63.

[0078] The storage unit 60 is constituted by, for example, a ROM and the like. The storage unit 60 stores programs such as the intermittent driving mode and the normal driving mode and various data, which are necessary for the sailing of the vessel 1.

[0079] The acquisition unit 61 is constituted by, for example, a RAM and the like. The acquisition unit 61 acquires the detection results of various sensors.

[0080] The determination unit 62 is constituted by, for example, a CPU and the like. The determination unit 62 determines the state of the vessel 1 on the basis of information obtained by the acquisition unit 61 and information stored in the storage unit 60.

[0081] The drive processing unit 63 is constituted by, for example, a CPU and the like. The drive processing unit 63 controls the operation of various actuators on the basis of the determination results of the determination unit 62 and the information stored in the storage unit 60 and the acquisition unit 61, and also performs operation control of the engine, such as fuel injection and ignition, using a known ECU provided in the propulsion machine 3.Operation Method of Propulsion System

[0082] An operation method of the propulsion system will now be described. The following mainly describes a switching operation between the intermittent driving mode and the normal driving mode when the vessel 1 is moving forward (when the required shift position is the forward position F) and a turning operation in the intermittent operation mode. A process which will be described below is repeatedly executed at a predetermined control cycle (for example, several tens of milliseconds [msec]).

[0083] FIG. 5 is a flowchart illustrating a switching operation between the intermittent driving mode and the normal driving mode in the vessel 1.

[0084] As shown in FIG. 5, in step S11, the control unit 8 determines whether or not the shift position is the forward position F and the required thrust Sd is equal to or less than the thrust output at the minimum output value of the drive source 12.

[0085] In a case in which the determination result in step S11 is “NO,” the process proceeds to step S12. That is, in a case in which the determination result in step S11 is “NO,” the control unit 8 determines that the shift position is other than the forward position F or that the required thrust Sd is greater than the thrust output at the minimum output value of the drive source 12.

[0086] In step S12, the control unit 8 executes the normal driving mode. In the normal driving mode, the output (throttle opening degree φ) of the drive source 12 is adjusted according to the position of the thrust input unit 5 (lever opening degree LE), and thus the thrust generated by the propulsion machine 3 is adjusted. As a result, the vessel 1 sails at the vessel speed V according to the required thrust Sd of the user.

[0087] In a case in which the determination result in step S11 is “YES,” the process proceeds to step S13. That is, in a case in which the determination result in step S11 is “YES,” the control unit 8 determines that the shift position is the forward position F and the required thrust Sd is equal to or less than the thrust output at the minimum output value of the drive source 12. In this case, the control unit 8 executes the intermittent driving mode.

[0088] FIG. 6 is a flowchart illustrating the intermittent control (auto-shift control) during the intermittent driving mode in the vessel 1.

[0089] As shown in FIG. 6, in step S21, it is determined whether or not it is immediately after the start of the intermittent control. The expression “immediately after the start of intermittent control” refers to, for example, several seconds after the start of the intermittent control.

[0090] In a case in which the determination result in step S21 is “YES,” it is determined that it is immediately after the start of the intermittent control, and the process proceeds to step S22.

[0091] In step S22, the control unit 8 sets a speed flag to “1.” The speed flag “1” is a flag for setting the shift position of the propulsion machine 3 to the forward position F. That is, when the speed flag becomes “1,” the control unit 8 sets the shift position of the propulsion machine 3 to the forward position F. As a result, the thrust of the propulsion machine 3 is generated, and the vessel speed V increases due to the thrust of the propulsion machine 3.

[0092] In a case in which the determination result in step S21 is “NO,” the process proceeds to step S23.

[0093] In step S23, the control unit 8 determines whether or not the vessel speed V is equal to or greater than a first speed threshold value V1, on the basis of the detection result of the vessel speed sensor 6. The first speed threshold value V1 is, for example, an upper limit value of the very low speed range (a boundary value between the slow speed range and the normal speed range). In this case, it is preferable that the first speed threshold value V1 be lower than the vessel speed V that can be realized with the minimum output value of the drive source 12 (the minimum value of the throttle opening degree φ). However, the first speed threshold value V1 may be set appropriately using actual traveling data.

[0094] In a case in which the determination result in step S23 is “YES” (V≥V1), the process proceeds to step S24. That is, in a case in which the determination result in step S23 is “YES,” it is determined that the vessel has exited or is likely to exit the very low speed range despite the required thrust Sd.

[0095] In this case, the control unit 8 sets the speed flag to “0” in step S24. The speed flag “0” is a flag for setting the shift position of the propulsion machine 3 to the neutral position N. That is, when the speed flag becomes “0,” the control unit 8 sets the shift position of the propulsion machine 3 to the neutral position N. As a result, the thrust of the propulsion unit 3 becomes zero, and an increase in the vessel speed V caused by the thrust of the propulsion machine 3 is suppressed.

[0096] In a case in which the determination result in step S23 is “NO” (V<V1), the process proceeds to step S25. That is, in a case in which the determination result in step S23 is “NO,” it is determined that the vessel is sailing within the very low speed range, on the basis of the required thrust Sd.

[0097] In step S25, it is determined whether or not the vessel speed V is equal to or less than a second speed threshold value V2. The second speed threshold value V2 is a lower limit value of the very low speed range.

[0098] In a case in which the determination result in step S25 is “YES” (V≤V2), the process proceeds to step S26. That is, in a case in which the determination result in step S25 is “YES,” the control unit 8 determines that the vessel has exited or is likely to exit the very low speed range despite the required thrust Sd.

[0099] In step S26, the control unit 8 sets the speed flag to “1.” As a result, the shift position of the propulsion machine 3 is set to the forward position F, and thus the vessel speed V increases.

[0100] In a case in which the determination result in step S25 is “NO” (V>V2), the process proceeds to step S27. That is, in a case in which the determination result in step S25 is “NO,” the control unit 8 determines that the vessel is sailing within the very low speed range, on the basis of the required thrust Sd.

[0101] In step S27, the control unit 8 determines whether the speed flag in the previous control cycle is “1” or “0.”

[0102] In a case in which the determination result in step S27 is “1,” the process proceeds to step S28.

[0103] In step S28, the control unit 8 maintains the speed flag at “1.” That is, the shift position of the propulsion machine 3 is maintained in the forward position F.

[0104] In a case in which the determination result in step S27 is “0,” the process proceeds to step S29.

[0105] In step S29, the control unit 8 maintains the speed flag at “0.” That is, the shift position of the propulsion machine 3 is maintained in the neutral position N.

[0106] In the intermittent driving mode, a routine of the intermittent control routine described above is repeated, and thus the vessel 1 can be allowed to sail in a state in which the vessel speed V is maintained within the very low speed range.

[0107] FIG. 7 is a flowchart illustrating the operation of the propulsion system based on a steering command during the intermittent driving mode.

[0108] As shown in FIG. 7, in step S31, the control unit 8 determines whether or not it is immediately after the start of the intermittent driving mode. The expression “immediately after the start of intermittent driving mode” refers to, for example, several seconds after the start of the intermittent driving mode.

[0109] In a case in which the determination result in step S31 is “YES,” the process proceeds to step S32.

[0110] In step S32, the control unit 8 sets a steering flag to “1.”

[0111] FIG. 8 is a plan view of the vessel 1 in a left intermittent state. In FIG. 8, “A” indicates the intermittent control (auto shift), and “N” indicates the neutral position N.

[0112] As shown in FIG. 8, the steering flag “1” is a flag for setting the propulsion machine 3 to the left intermittent state (see FIG. 4). The left intermittent state is a state in which the left propulsion machine 3b is intermittently controlled while the shift position of the right propulsion machine 3a is set to the neutral position N. In the left intermittent state, the thrust of the right propulsion machine 3a becomes zero. That is, in the left intermittent state, the thrust of the left propulsion machine 3b is set to be greater than the thrust of the right propulsion machine 3a.

[0113] In a case in which the determination result in step S31 is “NO,” the process proceeds to step S33.

[0114] After step S33, the control unit 8 determines whether or not a steering command angle θd is equal to or greater than a steering angle threshold value θa.

[0115] The steering command angle θd and the steering angle threshold value θa will be described.

[0116] The steering command angle θd is calculated, for example, from a map or the like stored in advance in the storage unit 60, on the basis of the amount of operation of the steering angle input unit 4, and is the steering angle θ of the propulsion machine 3 required to turn the vessel 1 in accordance with the steering request of the user. The control unit 8 rotates the propulsion machine 3 around the yaw direction with respect to the reference position on the basis of the calculated steering command angle θd. Specifically, the control unit 8 outputs the steering command angle θd to the propulsion machine 3. As a result, the propulsion machine 3 rotates around the yaw direction on the basis of the steering command angle θd. As a result, the orientation of the thrust of the propulsion machine 3 is changed. In the present embodiment, both of the right propulsion machine 3a and the left propulsion machine 3b are configured to rotate synchronously on the basis of the steering command angle θd. In addition, when the steering flag is determined, either the steering command value θm or the steering command angle θd may be used.

[0117] FIG. 9 is a view showing the steering angle threshold value θa.

[0118] As shown in FIG. 9, the steering angle threshold value θa includes a right steering angle threshold value θar, which is a threshold value for a direction in which the course of the vessel 1 turns right with respect to a straight-ahead direction, and a left steering angle threshold value θal, which is a threshold value for a direction in which the course of the vessel 1 turns left with respect to the straight-ahead direction. In the present embodiment, the absolute values of the right steering angle threshold value θar and the left steering angle threshold value θal are set to be equal to each other. As described above, in a case in which the steering angle θ in a state in which the propeller shaft 21 is parallel to the center line CL in a plan view is taken as the reference position (0°), then, for example, if the right steering angle threshold value θar is positive (+), the left steering angle threshold value θal becomes negative (−). However, in the present embodiment, the determination is made using the absolute values of the right steering angle threshold value θar and the left steering angle threshold value θal.

[0119] As shown in FIGS. 7 and 9, in step S33, the control unit 8 determines whether or not the steering command angle θd is greater than the right steering angle threshold value θar.

[0120] In a case in which the determination result in step S33 is “YES,” the process proceeds to step S34.

[0121] In step S34, the control unit 8 sets the steering flag to “1.”

[0122] In a case in which the determination result in step S33 is “NO,” the process proceeds to step S35.

[0123] In step S35, the control unit 8 determines whether or not the steering command angle θd is greater than the left steering angle threshold value θal.

[0124] In a case in which the determination result in step S35 is “YES,” the process proceeds to step S36.

[0125] In step S35, the control unit 8 sets the steering flag to “0.”

[0126] FIG. 10 is a plan view of the vessel 1 in a right intermittent state. In FIG. 10, “A” indicates the intermittent control (auto shift), and “N” indicates the neutral position N.

[0127] As shown in FIG. 10, the steering flag “0” is a flag for setting the propulsion machine 3 to the right intermittent state (see FIG. 4). The right intermittent state is a state in which the shift position of the left propulsion machine 3b is set to the neutral position N while the right propulsion machine 3a is intermittently controlled. In the right intermittent state, the thrust of the left propulsion machine 3b becomes zero. That is, in the right intermittent state, the thrust of the right propulsion machine 3a is set to be greater than the thrust of the left propulsion machine 3b.

[0128] As shown in FIG. 7, in step S37, the control unit 8 determines whether the steering flag in the previous control cycle is “1” or “0.”

[0129] In a case in which the determination result in step S37 is “1,” the process proceeds to step S38.

[0130] In step S38, the control unit 8 maintains the steering flag at “1.”

[0131] In a case in which the determination result in step S37 is “0,” the process proceeds to step S39.

[0132] In step S39, the control unit 8 maintains the steering flag at “0.”

[0133] FIG. 11 is a flowchart for explaining a switching operation (switching control) of each of the propulsion machines 3a and 3b in response to the steering flag.

[0134] As shown in FIG. 11, in step S41, it is determined whether or not the current steering flag is “0.”

[0135] In a case in which the determination result in step S41 is “YES,” the process proceeds to step S42.

[0136] As shown in FIGS. 4, 10, and 11, in step S42, the control unit 8 sets each of the propulsion machines 3a and 3b to the right intermittent state. That is, the control unit 8 sets the shift position of the left propulsion machine 3b to the neutral position N while intermittently controlling the right propulsion machine 3a. As a result, in the right intermittent state, the power of the right propulsion machine 3a is set to be greater than the power of the left propulsion machine 3b.

[0137] In a case in which the determination result in step S41 is “NO,” the process proceeds to step S43.

[0138] As shown in FIGS. 4, 8, and 11, in step S43, the control unit 8 sets each of the propulsion machines 3a and 3b to the left intermittent state. That is, the control unit 8 intermittently controls the left propulsion machine 3b while setting the shift position of the right propulsion machine 3a to the neutral position N. As a result, the power of the left propulsion machine 3b is set to be greater than the power of the right propulsion machine 3a.

[0139] FIG. 12 is a timing chart for explaining the operation of the vessel 1 according to the first embodiment.

[0140] As shown in FIG. 12, in the initial state at time t0, the required thrust Sd and the steering command angle θd are zero. Therefore, the shift position of each of the propulsion machines 3a and 3b is the neutral position N, the steering angle θ is zero, and the vessel speed V is zero.

[0141] At time t1, the shift position is the forward position F, and the required thrust Sd is equal to or less than the thrust output at the minimum output value of the drive source 12. Then, the intermittent driving mode is executed. Immediately after the start of the intermittent driving mode, when the steering flag is set to “1,” the propulsion machines 3a and 3b become the left intermittent state. That is, in a state in which the shift position of the right propulsion machine 3a is maintained in the neutral position N, the left propulsion machine 3b is intermittently controlled. As a result, the vessel speed V gradually increases.

[0142] Between time t2 and time t3, when the steering command angle θd increases to the left side in the turning direction (the side of the left steering angle threshold value θal), the vessel is steered to the left side around the yaw direction while each of the propulsion machines 3a and 3b is maintained in the left intermittent state. At this time, the steering angle θ of each of the propulsion machines 3a and 3b is set on the basis of the steering command angle θd. As a result, the left turning of the vessel 1 is started.

[0143] At time t3, when the steering command angle θd exceeds the left steering angle threshold value θal, the steering flag becomes “0,” and thus the propulsion machines 3a and 3b become the right intermittent state. That is, the right propulsion machine 3a is switched to the intermittent control, and the shift position of the left propulsion machine 3b is switched to the neutral position N (switching control).

[0144] FIG. 13 is a plan view of the vessel 1 during left turning.

[0145] As shown in FIG. 13, when the vessel 1 turns left, the right propulsion machine 3a functions as an outer propulsion machine located on the outer side in the turning direction, and the left propulsion machine 3b functions as an inner propulsion machine located on the inner side in the turning direction. Therefore, by setting the propulsion machine to the right intermittent state when the vessel 1 turns left, the left turning of the vessel 1 is performed in a state in which the thrust of the outer propulsion machine is greater than the thrust of the inner propulsion machine.

[0146] As shown in FIG. 12, at time t4, when the vessel speed V reaches the first speed threshold value V1, the shift position of the right propulsion machine 3a is switched to the neutral position N under the intermittent control of the right propulsion machine 3a. As a result, the vessel speed V gradually decreases.

[0147] From time t5 to time t6, the steering command angle θd gradually returns to 0°. At this time, even when the steering command angle θd falls below the left steering angle threshold value θal, only the steering angle θ is controlled on the basis of the steering command angle θd while each of the propulsion machines 3a and 3b is maintained in the right intermittent state.

[0148] At time t6, when the vessel speed V becomes equal to or less than the second speed threshold value V2, the shift position of the right propulsion machine 3a is switched to the forward position F under the intermittent control of the right propulsion machine 3a. As a result, the vessel speed V gradually increases.

[0149] At time t7, when the vessel speed V reaches the first speed threshold value V1, the shift position of the right propulsion machine 3a is switched to the neutral position N under the intermittent control of the right propulsion machine 3a. As a result, the vessel speed V gradually decreases. In this way, in the right intermittent state, the shift position of the right propulsion machine 3a is switched on the basis of the vessel speed V as a first condition, while the shift position of the left propulsion machine 3b is maintained in the neutral position N regardless of the first condition. In this case, the shift position of the left propulsion machine 3b is controlled using the steering command angle θd as a second condition that is different from the first condition.

[0150] Between time t7 and time t8, when the steering command angle θd increases to the right turning side (the side of the right steering angle threshold value θar), the vessel is steered to the right side around the yaw direction while each of the propulsion machines 3a and 3b is maintained in the right intermittent state. At this time, the steering angle θ of each of the propulsion machines 3a and 3b is set on the basis of the steering command angle θd. As a result, the right turning of the vessel 1 is started.

[0151] At time t8, when the steering command angle θd exceeds the right steering angle threshold value θar, the steering flag becomes “1,” and thus the propulsion machines 3a and 3b become the left intermittent state. That is, the shift position of the right propulsion machine 3a is switched to the neutral position N, and the left propulsion machine 3b is switched to the intermittent control (switching control).

[0152] FIG. 14 is a plan view of the vessel 1 during right turning.

[0153] As shown in FIG. 14, when the vessel 1 turns right, the left propulsion machine 3b functions as an outer propulsion machine located on the outer side, and the right propulsion machine 3a functions as an inner propulsion machine located on the inner side in the turning direction. Therefore, by setting the propulsion machine to the left intermittent state when the vessel 1 turns right, the right turning of the vessel 1 is performed in a state in which the thrust of the outer propulsion machine is greater than the thrust of the inner propulsion machine.

[0154] As shown in FIG. 12, at time t9, when the vessel speed V becomes equal to or less than the second speed threshold value V2, the shift position of the left propulsion machine 3b is switched to the forward position F under the intermittent control of the left propulsion machine 3b. As a result, the vessel speed V gradually increases. In this way, in the left intermittent state, the shift position of the left propulsion machine 3b is switched on the basis of the vessel speed V as a first condition, while the shift position of the right propulsion machine 3a is maintained in the neutral position N regardless of the first condition. In this case, the shift position of the right propulsion machine 3a is controlled using the steering command angle θd as a second condition that is different from the first condition.

[0155] At time t10, the required shift position of each of the propulsion machines 3a and 3b is set to the neutral position N (the required thrust Sd is zero), and thus the shift position of each of the propulsion machines 3a and 3b is set to the neutral position N.

[0156] In this way, the present embodiment is equipped with at least the right propulsion machine (first propulsion machine) 3a and the left propulsion machine (second propulsion machine) 3b provided side by side in the leftward-rightward direction in the hull 2, and the control unit 8 that includes at least a processor and a memory and controls the right propulsion machine 3a and the left propulsion machine 3b. The control unit 8 is capable of executing the intermittent control to intermittently vary the thrust of at least one propulsion machine on the basis of the first condition for varying the vessel speed V. During the intermittent driving mode, the control unit 8 is capable of executing the switching control to make the thrust of the right propulsion machine 3a and the thrust of the left propulsion machine 3b different from each other on the basis of the turning direction.

[0157] According to this configuration, during the intermittent driving mode, the switching control is performed on the basis of the turning direction, and thus the thrust of each of the propulsion machines 3a and 3b is controlled such that an appropriate thrust for turning is generated regardless of the state before the turning. As a result, it is possible to realize smooth turning sailing according to the command of the user, and it is possible to improve responsiveness during turning. As a result, in the present embodiment, it is possible to further contribute to the development of sustainable transportation systems.

[0158] In the switching control, the control unit 8 of the present embodiment sets the thrust of the outer propulsion machine to be greater than the thrust of the inner propulsion machine.

[0159] According to this configuration, in the outer propulsion machine, a component, of the thrust of the outer propulsion machine, in a direction orthogonal to a straight line passing through a center of flotation of the vessel 1 and the steering shaft 16 in a plan view is greater than that of the inner propulsion machine. For this reason, when the vessel 1 is turning, by increasing the thrust of the outer propulsion machine, it is possible to reduce fuel consumption, and it is possible to improve turning performance.

[0160] In the propulsion system of the present embodiment, in the switching control, the control unit 8 executes the intermittent control on the outer propulsion machine and sets the thrust of the inner propulsion machine to zero.

[0161] According to this configuration, it is possible to improve turning performance while the very low speed range is maintained.

[0162] In the propulsion system of the present embodiment, the control unit 8 switches from the intermittent control to the switching control in a case in which the steering command angle θd is equal to or greater than the steering angle threshold value θa during the intermittent control in the intermittent driving mode.

[0163] According to this configuration, the occurrence of hunting in a region where the steering angle θ is small can be suppressed, and the user can be prevented from feeling uncomfortable.

[0164] In the propulsion system of the present embodiment, the steering angle threshold value θa includes the right steering angle threshold value θar at which the course of the hull 2 is changed to the right side with respect to the straight-ahead direction, and the left steering angle threshold value θal at which the course of the hull 2 is changed to the left side with respect to the straight-ahead direction.

[0165] According to this configuration, it is possible to determine whether to continue the intermittent control or to perform the switching control at each time when the vessel turns right and when the vessel turns left during the intermittent driving mode.

[0166] In the propulsion system of the present embodiment, the first condition is the vessel speed V. The intermittent control switches the shift position of at least one propulsion machine from the forward position F to the neutral position N in a case in which the vessel speed V is equal to or greater than the first speed threshold value V1, and switches the shift position from the neutral position N to the forward position F in a case in which the vessel speed V is equal to or less than the second speed threshold value V2.

[0167] According to this configuration, by performing the intermittent control on the basis of the vessel speed V itself, it is possible to allow the vessel 1 to sail at the very low speed within the range of a desired vessel speed V.

[0168] In the propulsion system of the present embodiment, in the intermittent driving mode, the intermittent control is performed on one propulsion machine 3 on the basis of the first condition, and the thrust of the other propulsion machine 3 is controlled on the basis of the second condition that is different from the first condition.

[0169] According to this configuration, it is easy to control the thrust of each of the propulsion machines 3a and 3b to a desired thrust.

[0170] In the propulsion system of the present embodiment, in the switching control, the control unit 8 controls each of the propulsion machines 3a and 3b such that the orientations of the thrust of the propulsion machine 3a and the thrust of the propulsion machine 3b are the same direction.

[0171] According to this configuration, a smooth transition can be performed even in a case in which the switching or variation of the thrust may occur between the propulsion machines 3a and 3b, for example, in a case of the switching control or in a case in which switching is performed from the intermittent driving mode to the normal driving mode. As a result, it is possible to improve responsiveness.Second Embodiment

[0172] FIG. 15 is a plan view of a vessel 1 according to a second embodiment. The second embodiment differs from the embodiment described above in that three propulsion machines 3 are provided.

[0173] The vessel 1 shown in FIG. 15 is equipped with a central propulsion machine 3c in addition to the right propulsion machine 3a and a left propulsion machine 3b. The central propulsion machine 3c is provided at a position overlapping the center line CL in a plan view.

[0174] FIG. 16 is a state transition diagram during the intermittent driving mode (during auto-shift control) in the vessel 1 of the second embodiment.

[0175] As shown in FIG. 16, in the switching control, the control unit 8 controls the thrust and the orientation of the thrust (steering angle θ) of the central propulsion machine 3c in accordance with the outer propulsion machine. Specifically, in the right intermittent state, the right propulsion machine 3a functions as the outer propulsion machine during left turning, and the left propulsion machine 3b functions as the inner propulsion machine during left turning. For this reason, in the right intermittent state, the shift position of the left propulsion machine 3b is set to the neutral position N while the right propulsion machine 3a and the central propulsion machine 3c are intermittently controlled. In the left intermittent state, the left propulsion machine 3b functions as the outer propulsion machine during right turning, and the right propulsion machine 3a functions as the inner propulsion machine during right turning. For this reason, in the left intermittent state, the shift position of the right propulsion machine 3a is set to the neutral position N while the left propulsion machine 3b and the central propulsion machine 3c are intermittently controlled.

[0176] In this way, in the propulsion system of the present embodiment, in the switching control, the control unit 8 controls the thrust and the orientation of the thrust of the central propulsion machine 3c in accordance with the outer propulsion machine.

[0177] According to this configuration, it is possible to increase the thrust acting during turning, and thus it is possible to improve turning performance.Third Embodiment

[0178] FIG. 17 is a state transition diagram during the intermittent driving mode (during auto-shift control) in a vessel 1 of a third embodiment.

[0179] As shown in FIG. 17, in the switching control, the control unit 8 controls the thrust and the orientation of the thrust (steering angle θ) of the central propulsion machine 3c in accordance with the inner propulsion machine. Specifically, in the right intermittent state, the right propulsion machine 3a functions as the outer propulsion machine during left turning, and the left propulsion machine 3b functions as the inner propulsion machine during left turning. For this reason, in the right intermittent state, the shift positions of the left propulsion machine 3b and the central propulsion machine 3c are set to the neutral position N while the right propulsion machine 3a is intermittently controlled. In the left intermittent state, the left propulsion machine 3b functions as the outer propulsion machine during right turning, and the right propulsion machine 3a functions as the inner propulsion machine during right turning. For this reason, in the left intermittent state, the shift positions of the right propulsion machine 3a and the central propulsion machine 3c are set to the neutral position N while the left propulsion machine 3b is intermittently controlled.

[0180] In this way, in the propulsion system of the present embodiment, in the switching control, the control unit 8 controls the thrust and the orientation of the thrust of the central propulsion machine 3c in accordance with the inner propulsion machine.

[0181] According to this configuration, it is easy to maintain the very low speed range during turning.Fourth Embodiment

[0182] FIG. 18 is a plan view of a vessel 1 according to a fourth embodiment. The fourth embodiment differs from the embodiments described above in that four propulsion machines 3 are provided.

[0183] The vessel 1 shown in FIG. 18 is equipped with four propulsion machines 103a to 103d. The four propulsion machines 103a to 103d are a right outer propulsion machine (first propulsion machine) 103a, a left outer propulsion machine (second propulsion machine) 103b, a right inner propulsion machine (third propulsion machine) 103c, and a left inner propulsion machine (fourth propulsion machine) 103d. The right outer propulsion machine 103a is provided at the right side end portion of the stern. The left outer propulsion machine 103b is provided at the left side end portion of the stern. The right inner propulsion machine 103c is provided between the right outer propulsion machine 103a and the left outer propulsion machine 103b, and on the right side with respect to the center line CL. The left inner propulsion machine 103d is provided between the right outer propulsion machine 103a and the left outer propulsion machine 103b, and on the left side with respect to the center line CL.

[0184] In a four-machine vessel 1, in the right inner propulsion machine 103c, the thrust and the orientation of the thrust may be controlled in accordance with the right outer propulsion machine 103a, and in the left inner propulsion machine 103d, the thrust and the orientation of the thrust may be controlled in accordance with the left outer propulsion machine 103b. In addition, in the right inner propulsion machine 103c and the left inner propulsion machine 103d, the thrust and the orientation of the thrust may be controlled in accordance with any one of the outer propulsion machines 103a and 103b. Fifth Embodiment

[0185] FIG. 19 is a state transition diagram during the intermittent driving mode (during auto-shift control) in a vessel 1 of a fifth embodiment.

[0186] The vessel 1 shown in FIG. 19 differs from the embodiments described above in that, in the switching control, the shift position of the outer propulsion machine is set to the forward position F while the inner propulsion machine is intermittently controlled. Specifically, in a right continuation state, the right propulsion machine 3a functions as the outer propulsion machine during left turning, and the left propulsion machine 3b functions as the inner propulsion machine during left turning. For this reason, in the right continuation state, the left propulsion machine 3b is intermittently controlled while the shift position of the right propulsion machine 3a is set to the forward position F. In a left continuation state, the left propulsion machine 3b functions as the outer propulsion machine during right turning, and the right propulsion machine 3a functions as the inner propulsion machine during right turning. For this reason, in the left continuation state, the right propulsion machine 3a is intermittently controlled while the shift position of the left propulsion machine 3b is set to the forward position F.

[0187] FIG. 20 is a flowchart for explaining a switching operation (switching control) of each of the propulsion machines 3a and 3b in response to the steering flag.

[0188] As shown in FIG. 20, in step S51, it is determined whether or not the current steering flag is “0.”

[0189] In a case in which the determination result in step S51 is “YES,” the process proceeds to step S52.

[0190] FIG. 21 is a plan view of the vessel 1 in the right continuation state.

[0191] As shown in FIGS. 19 to 21, in step S52, the control unit 8 sets each of the propulsion machines 3a and 3b to the right continuation state. That is, the control unit 8 intermittently controls the left propulsion machine 3b while setting the shift position of the right propulsion machine 3a to the forward position F. As a result, in the right continuation state, the power of the right propulsion machine 3a is set to be greater than the power of the left propulsion machine 3b.

[0192] FIG. 22 is a plan view of the vessel 1 in the left continuation state.

[0193] As shown in FIGS. 19, 20 and 22, in a case in which the determination result in step S51 is “NO,” the process proceeds to step S53.

[0194] In step S53, the control unit 8 sets each of the propulsion machines 3a and 3b to the left continuation state. That is, the control unit 8 sets the shift position of the left propulsion machine 3b to the forward position F while intermittently controlling the right propulsion machine 3a. As a result, the power of the left propulsion machine 3b is set to be greater than the power of the right propulsion machine 3a.

[0195] FIG. 23 is a timing chart for explaining the operation of a propulsion system in the vessel 1 according to the fifth embodiment. FIG. 20 differs from FIG. 12 only in the state of the propulsion machines 3a and 3b. Therefore, the following mainly describes the differences from FIG. 12.

[0196] As shown in FIG. 23, at time t1, the shift position is the forward position F, and the required thrust Sd is equal to or less than the thrust output at the minimum output value of the drive source 12. Then, the intermittent driving mode is executed. Immediately after the start of the intermittent driving mode, when the steering flag is set to “1,” the propulsion machines 3a and 3b become the left continuation state. That is, in a state in which the right propulsion machine 3a is intermittently controlled, the shift position of the left propulsion machine 3b is maintained in the forward position F. At time t1, the right propulsion machine 3a is in a state of being immediately after the intermittent control, and thus the shift position of the right propulsion unit 3a is set to the forward position F. That is, in the left continuation state, the shift position of the right propulsion machine 3a is switched on the basis of the vessel speed V as a first condition, while the shift position of the left propulsion machine 3b is maintained in the forward position F regardless of the first condition. In this case, the shift position of the left propulsion machine 3b is controlled using the steering command angle θd as a second condition that is different from the first condition.

[0197] At time t3, when the steering command angle θd exceeds the left steering angle threshold value θal, the steering flag becomes “0,” and thus the propulsion machines 3a and 3b become the right continuation state. That is, the shift position of the right propulsion machine 3a is maintained in the forward position F, and the left propulsion machine 3b is intermittently controlled. Due to the switching between the left continuation state and the right continuation state, the left propulsion machine 3b becomes a state of being immediately after intermittent control, and thus the shift position of the left propulsion machine 3b is set to the forward position F (the speed flag is “1”).

[0198] At time t4, when the vessel speed V reaches the first speed threshold value V1, the shift position of the left propulsion machine 3b is switched to the neutral position N under the intermittent control of the left propulsion machine 3b. The shift position of the right propulsion machine 3a is maintained in the forward position F.

[0199] At time t6, when the vessel speed V becomes equal to or less than the second speed threshold value V2, the shift position of the left propulsion machine 3b is switched to the forward position F under the intermittent control of the left propulsion machine 3b. The shift position of the right propulsion machine 3a is maintained in the forward position F.

[0200] At time t7, when the vessel speed V reaches the first speed threshold value V1, the shift position of the left propulsion machine 3b is switched to the neutral position N under the intermittent control of the left propulsion machine 3b. The shift position of the right propulsion machine 3a is maintained in the forward position F. In this way, in the right continuation state, the shift position of the left propulsion machine 3b is switched on the basis of the vessel speed V as a first condition, while the shift position of the right propulsion machine 3a is maintained in the forward position F regardless of the first condition. In this case, the shift position of the right propulsion machine 3a is controlled using the steering command angle θd as a second condition that is different from the first condition.

[0201] At time t8, when the steering command angle θd exceeds the right steering angle threshold value θar, the steering flag becomes “1,” and thus the propulsion machines 3a and 3b become the left continuation state. That is, the intermittent control of the right propulsion machine 3a is executed, and the shift position of the left propulsion machine 3b is maintained in the forward position F. At time t8, the shift position of the right propulsion machine 3a is maintained in the forward position F.

[0202] Thereafter, at time t9 and time t10, the shift position of the right propulsion machine 3a is switched between the forward position F and the neutral position N under the intermittent control of the right propulsion machine 3a.

[0203] Then, at time t11, the required shift position of each of the propulsion machines 3a and 3b is set to the neutral position N (the required thrust Sd is zero), and thus the shift position of each of the propulsion machines 3a and 3b is set to the neutral position N.

[0204] In this way, in the propulsion system of the present embodiment, in the switching control, the control unit 8 causes the outer propulsion machine to continuously generate the thrust and executes the intermittent control on the inner propulsion machine.

[0205] According to this configuration, it is possible to adjust the vessel speed V by the inner propulsion machine while it is possible to reliably apply the thrust to the vessel 1 by the outer propulsion machine. As a result, it is possible to improve turning performance, and it is possible to allow the vessel to sail at the very low speed.

[0206] In the fifth embodiment described above, the vessel 1 having two machines has been described as an example, but it is possible to employ the configuration of the present embodiment in the vessel 1 having three or more machines.Sixth Embodiment

[0207] FIG. 24 is a state transition diagram during the intermittent driving mode (during auto-shift control) in a vessel 1 according to a sixth embodiment. FIG. 25 is a flowchart for explaining a switching operation of each of the propulsion machines 3a and 3b in response to a speed flag and a steering flag. In the embodiments described above, the state of the propulsion machine 3 is switched between the right intermittent state and the left intermittent state, or the right continuation state and the left continuation state, whereas in the present embodiment, the state of the propulsion machine 3 is switched between a first state, a second state, and a third state.

[0208] As shown in FIGS. 24 and 25, in step S61, it is determined whether or not the current speed flag is “0.”

[0209] In a case in which the determination result in step S61 is “YES,” the process proceeds to step S62.

[0210] In step S62, the control unit 8 sets each of the propulsion machines 3a and 3b to the first state. In the present embodiment, the first state is a state in which the shift position of each of the propulsion machines 3a and 3b is set to the neutral position N.

[0211] In a case in which the determination result in step S61 is “NO,” the process proceeds to step S63.

[0212] In step S63, it is determined whether or not the current steering flag is “1.”

[0213] In a case in which the determination result in step S63 is “YES,” the process proceeds to step S64.

[0214] In step S64, the control unit 8 sets each of the propulsion machines 3a and 3b to the second state. In the present embodiment, the second state is a state in which the shift position of the left propulsion machine 3b is set to the forward position F while the shift position of the right propulsion machine 3a is maintained in the neutral position N. By transitioning between the first state and the second state, the shift position of the left propulsion machine 3b is switched between the neutral position N and the forward position F. That is, by transitioning between the first state and the second state, the intermittent control of the left propulsion machine 3b is executed (left intermittent state) while the shift position of the right propulsion machine 3a is maintained in the neutral position N.

[0215] In a case in which the determination result in step S63 is “NO,” the process proceeds to step S65.

[0216] In step S65, the control unit 8 sets each of the propulsion machines 3a and 3b to the third state. In the present embodiment, the third state is a state in which the shift position of the left propulsion machine 3b is maintained in the neutral position N while the shift position of the right propulsion machine 3a is set to the forward position F. By transitioning between the first state and the third state, the shift position of the right propulsion machine 3a is switched between the neutral position N and the forward position F. That is, by transitioning between the first state and the third state, the intermittent control of the right propulsion machine 3a is executed (right intermittent state) while the shift position of the left propulsion machine 3b is maintained in the neutral position N. By transitioning between the second state and the third state, the propulsion machine 3 that is the target of the intermittent control is switched (switching control).Seventh Embodiment

[0217] FIG. 26 is a state transition diagram during the intermittent driving mode (during auto-shift control) in a vessel 1 according to a seventh embodiment. FIG. 27 is a flowchart for explaining a switching operation of each of the propulsion machines 3a and 3b in response to a speed flag and a steering flag. In the embodiments described above, the intermittent control of the outer propulsion machine is executed while the shift position of the inner propulsion machine is set to the neutral position N, whereas in the present embodiment, the shift position of the outer propulsion machine is maintained in the forward position F while the intermittent control of the inner propulsion machine is executed.

[0218] As shown in FIGS. 26 and 27, in step S71, it is determined whether or not the current speed flag is “1.”

[0219] In a case in which the determination result in step S71 is “YES,” the process proceeds to step S72.

[0220] In step S72, the control unit 8 sets each of the propulsion machines 3a and 3b to the first state. In the present embodiment, the first state is a state in which the shift position of each of the propulsion machines 3a and 3b is set to the forward position F.

[0221] In a case in which the determination result in step S71 is “NO,” the process proceeds to step S73.

[0222] In step S73, it is determined whether or not the current steering flag is “1.”

[0223] In a case in which the determination result in step S73 is “YES,” the process proceeds to step S74.

[0224] In step S74, the control unit 8 sets each of the propulsion machines 3a and 3b to the second state. In the present embodiment, the second state is a state in which the shift position of the left propulsion machine 3b is maintained in the forward position F while the shift position of the right propulsion machine 3a is set to the neutral position N. By transitioning between the first state and the second state, the shift position of the right propulsion machine 3a is switched between the neutral position N and the forward position F. That is, by transitioning between the first state and the second state, the intermittent control of the right propulsion machine 3a is executed (left continuation state) while the shift position of the left propulsion machine 3b is maintained in the forward position F.

[0225] In a case in which the determination result in step S73 is “NO,” the process proceeds to step S75.

[0226] In step S75, the control unit 8 sets each of the propulsion machines 3a and 3b to the third state. In the present embodiment, the third state is a state in which the shift position of the left propulsion machine 3b is set to the neutral position N while the shift position of the right propulsion machine 3a is maintained in the forward position F. By transitioning between the first state and the third state, the shift position of the left propulsion machine 3b is switched between the neutral position N and the forward position F. That is, by transitioning between the first state and the third state, the intermittent control of the left propulsion machine 3b is executed (right continuation state) while the shift position of the right propulsion machine 3a is maintained in the forward position F. By transitioning between the second state and the third state, the propulsion machine 3 that is the target of the intermittent control is switched (switching control).Eighth Embodiment

[0227] FIG. 28 is a timing chart for explaining the operation of a propulsion system. In the embodiments described above, the vessel speed V itself is used as the first condition for varying the vessel speed V. In contrast, the present embodiment differs from the embodiments described above in that in the intermittent control, time (shift switching cycle) is used as the first condition for varying the vessel speed V.

[0228] As shown in FIG. 28, at time t11, the shift position is the forward position F, and the required thrust Sd is equal to or less than the thrust output at the minimum output value of the drive source 12. Then, the intermittent driving mode is executed. Immediately after the start of the intermittent driving mode, when the steering flag is set to “1,” the propulsion machines 3a and 3b become the left intermittent state. That is, in a state in which the shift position of the right propulsion machine 3a is maintained in the neutral position N, the left propulsion machine 3b is intermittently controlled.

[0229] At time t12, when the steering command angle θd exceeds the left steering angle threshold value θal, the steering flag becomes “0,” and thus the propulsion machines 3a and 3b become the right intermittent state. That is, the right propulsion machine 3a is switched to the intermittent control, and the shift position of the left propulsion machine 3b is switched to the neutral position N.

[0230] For example, as shown at times t12 to t14, in the intermittent control of the present embodiment, the switching of the shift position between the forward position F and the neutral position N is performed on the basis of a shift switching cycle Ts. The shift switching cycle Ts is a time during which a forward set time Tfl and a neutral set time Tnl are performed once each. In the present embodiment, during the intermittent control, the switching of the shift position between the forward position F and the neutral position N is performed by repeating the shift switching cycle Ts.

[0231] At time t15, when the steering command angle θd exceeds the right steering angle threshold value θar, the steering flag becomes “1,” and thus the propulsion machines 3a and 3b become the left intermittent state. That is, the shift position of the right propulsion machine 3a is switched to the neutral position N, and the left propulsion machine 3b is switched to the intermittent control.

[0232] For example, as shown at times t15 to t17, even in the left intermittent state, the intermittent control of the left propulsion machine 3b is performed on the basis of the shift switching cycle Ts. In the present embodiment, during the intermittent control, the switching of the shift position between the forward position F and the neutral position N is performed by repeating the shift switching cycle Ts. In the present embodiment, the shift switching cycle Ts of the corresponding propulsion machine 3 is set to be equal in both the right intermittent state and the left intermittent state. However, the shift switching cycle Ts of the corresponding propulsion machine 3 may be different between the right intermittent state and the left intermittent state.

[0233] Thus, in the propulsion system of the present embodiment, in the intermittent driving mode, the control unit 8 executes the intermittent control of the thrust by switching the shift position between the forward position F and the neutral position N on the basis of the shift switching cycle Ts.

[0234] According to this configuration, by switching the shift position on the basis of a shift switching cycle set in advance, the control can be simplified compared to a case in which the shift position is switched on the basis of the vessel speed V.Modification Example of Eighth Embodiment

[0235] In the eighth embodiment described above, the configuration in which the ratio of the forward set time Tfl to the neutral set time Tnl is equal in the shift switching cycle Ts has been described, but the present disclosure is not limited to this configuration. In one shift switching cycle Ts, the lengths and ratios of the neutral set time Tnl and the forward set time Tfl can be changed as appropriate.

[0236] In the eighth embodiment described above, the configuration in which the shift position is switched on the basis of one type of shift switching cycle Ts during the intermittent control has been described, but the present disclosure is not limited to this configuration. The control unit 8 may select one shift switching cycle Ts from among a plurality of types of shift switching cycles Ts and perform the intermittent control. In the plurality of types of shift switching cycles Ts, at least one of the forward set time Tfl and the neutral set time Tnl in one shift switching cycle Ts only has to be different from that in another shift switching cycle Ts. In this case, the lengths of the shift switching cycles Ts themselves may be equal to or different from each other.

[0237] In a configuration having the plurality of types of shift switching cycles Ts, the control unit 8 can select one shift switching cycle Ts from among the plurality of types of shift switching cycles Ts on the basis of, for example, the required thrust Sd, sea conditions, and the like. In this case, it is preferable that the control unit 8 selects a shift switching cycle Ts in which the proportion of the neutral set time Tnl in the shift switching cycle Ts is small, for example, in a case in which the required thrust Sd is high, compared to a case in which the required thrust Sd is low. As a result, it is easy to adjust the vessel speed V to correspond to the required thrust Sd.Other Modification Examples

[0238] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the configuration are possible without departing from the spirit of the present disclosure. The present disclosure is not limited by the foregoing description, but only by the appended claims.

[0239] The type of hull 2 may be applied to various water moving bodies such as a V-hull (V-Shaped Hull), a pontoon vessel, a center console, a runabout, a fishing boat, and a water bike.

[0240] In the embodiments described above, the drive source 12 is an internal combustion engine, but the present disclosure is not limited to this configuration. The drive source 12 may be an electric motor or the like. In the case of an electric motor, the motor rotation speed, torque, or the like corresponds to the “thrust.” In this case, the neutral position N is achieved by setting the motor rotation speed to zero.

[0241] In a case in which automatic driving or driving assistance (for example, autopilot or cruise control as constant speed driving) is performed, it may be configured such that the computer calculates the command value and sets the target speed, and the like without inputting the “required thrust Sd” by the user (operator).

[0242] In the embodiments described above, the configuration in which the intermittent control is performed by switching the shift position between the forward position F and the neutral position N has been described, but the present disclosure is not limited to this configuration. The intermittent control may be performed by switching between the forward position F and the reverse position R.

[0243] In the embodiments described above, the intermittent driving mode has been described using the example in which the vessel 1 moves forward, but the present disclosure is not limited to this configuration. The intermittent driving mode may be performed when the vessel 1 is moving in reverse. In this case, as the intermittent control, the shift position may be switched between the reverse position R and the neutral position N, or the shift position may be switched between the reverse position R and the forward position F.

[0244] In the embodiments described above, the configuration in which the very low speed sailing is possible by switching the shift position in the intermittent driving mode has been described, but the present disclosure is not limited to this configuration. The intermittent driving mode may be realized by varying the thrust within the same shift position (forward position F when moving forward, and reverse position R when moving in reverse) based on the course of the vessel 1.

[0245] In the embodiments described above, the configuration in which the intermittent driving mode is switched between the enabled state and the disabled state by operating the operation unit 7 has been described, but the present disclosure is not limited to this configuration. The intermittent driving mode may be enabled at all times.

[0246] In the embodiments described above, the configuration in which the steering command angle θd is calculated on the basis of the amount of operation of the steering angle input unit 4 has been described, but the present disclosure is not limited to this configuration. The steering command angle θd may be calculated on the basis of the amount of operation of the steering angle input unit 4 per unit time. According to this configuration, the switching control is executed only in a case in which the output of the propulsion machine 3 is required, such as during sharp turning. As a result, it is possible to improve fuel efficiency.

[0247] In the embodiments described above, the configuration in which the switching control is executed while maintaining the intermittent driving mode (a state in which at least one propulsion machine is performing the intermittent control) has been described, but the present disclosure is not limited to this configuration. By performing the switching control, the driving mode may be transitioned between the intermittent driving mode and the normal driving mode.

[0248] In the embodiments described above, the configuration in which the steering command angle θd is used as the second condition, thereby maintaining the shift position at the neutral position N or the forward position F regardless of the vessel speed V and the like has been described, but the present disclosure is not limited to this configuration. The shift position and the thrust may be controlled on the basis of, for example, the vessel speed V or the shift switching cycle Ts as the second condition. In addition, the second condition may be the engine load of the propulsion machine that is operating in gear (forward position F or reverse position R), external disturbance information such as a wind orientation and a wind speed, the number of crew members, the amount of cargo on board, and the like. In other words, the control may be performed such that, for example, in a case in which the engine load is high, or there is a head wind, head waves, or a lot of cargo, the gear is engaged, and in a case in which the engine load is low, or there are following waves, a tail wind, or little cargo, the gear is not engaged.

[0249] In the embodiments described above, the configuration in which switching control is performed such that the thrust of the outer propulsion machine is greater than the thrust of the inner propulsion machine during turning has been described, but the present disclosure is not limited to this configuration. During turning, the switching control may be performed such that the thrust of the inner propulsion machine is greater than the thrust of the outer propulsion machine.

[0250] In the embodiments described above, the configuration has been described in which the absolute values of the right steering angle threshold value θar and the left steering angle threshold value θal are equal to each other, but the present disclosure is not limited to this configuration. The absolute values of the right steering angle threshold value θar and the left steering angle threshold value θal may be different from each other.

[0251] In the embodiments described above, the configuration in which both the right propulsion machine 3a and the left propulsion machine 3b rotate synchronously on the basis of the steering command angle θd has been described, but the present disclosure is not limited to this configuration. The steering angles θ of the right propulsion machine 3a and the left propulsion machine 3b may be made different from each other on the basis of the steering command angle θd.

[0252] In addition, it is possible to appropriately replace the constituent elements in the above-described embodiments with well-known constituent elements without departing from the spirit of the present disclosure, and the above-described modification examples may be combined as appropriate.

[0253] The propulsion system for a vessel according to the above-described embodiments may be partially or entirely described as follows.Appendix 1

[0254] A vessel including

[0255] a hull,

[0256] at least a first propulsion machine and a second propulsion machine that are provided side by side in a leftward-rightward direction in the hull, and

[0257] a control unit including at least a processor and a memory and controlling the first propulsion machine and the second propulsion machine,

[0258] wherein the control unit is capable of executing intermittent control to intermittently vary a thrust of at least one propulsion machine of the first propulsion machine and the second propulsion machine on the basis of a first condition for varying a vessel speed, and

[0259] wherein, during an intermittent driving mode in which at least one of the propulsion machines operates under the intermittent control, the control unit is capable of executing switching control to make a thrust of the first propulsion machine and a thrust of the second propulsion machine different from each other on the basis of a turning direction.Appendix 2

[0260] A control device for a vessel which includes a control unit including at least processor and a memory and controlling at least a first propulsion machine and a second propulsion machine that are provided side by side in a leftward-rightward direction in the hull,

[0261] wherein the control unit is capable of executing intermittent control to intermittently vary a thrust of at least one propulsion machine of the first propulsion machine and the second propulsion machine on the basis of a first condition for varying a vessel speed, and

[0262] wherein, during an intermittent driving mode in which at least one of the propulsion machines operates under the intermittent control, the control unit is capable of executing switching control to make a thrust of the first propulsion machine and a thrust of the second propulsion machine different from each other on the basis of a turning direction.BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS1 Vessel

[0264] 2 Hull

[0265] 3a Right propulsion machine (first propulsion machine, outer propulsion machine, inner propulsion machine)

[0266] 3b Left propulsion machine (second propulsion machine, inner propulsion machine, outer propulsion machine)

[0267] 3c Central propulsion machine

[0268] 8 Control unit

[0269] 103a Right outer propulsion machine (first propulsion machine)

[0270] 103b Left outer propulsion machine (second propulsion machine)

[0271] 103c Right inner propulsion machine (third propulsion machine)

[0272] 103d Left inner propulsion machine (fourth propulsion machine)

[0273] F Forward position

[0274] N Neutral position

[0275] Ts Shift switching cycle

[0276] V Vessel speed

[0277] V1 First speed threshold value

[0278] V2 Second speed threshold value θ Steering angle θa Steering angle threshold value θal Left steering angle threshold value θar Right steering angle threshold value θm Steering command value

Claims

1. A propulsion system for a vessel comprising:at least a first propulsion machine and a second propulsion machine that are provided side by side in a leftward-rightward direction in a hull; anda control unit including at least a processor and a memory and controlling the first propulsion machine and the second propulsion machine,wherein the control unit is capable of executing intermittent control to intermittently vary a thrust of at least one propulsion machine of the first propulsion machine and the second propulsion machine on the basis of a first condition for varying a vessel speed, andwherein, during an intermittent driving mode in which at least one of the propulsion machines operates under the intermittent control, the control unit is capable of executing switching control to make a thrust of the first propulsion machine and a thrust of the second propulsion machine different from each other on the basis of a turning direction.

2. The propulsion system for a vessel according to claim 1,wherein, when, of the first propulsion machine and the second propulsion machine, the propulsion machine located on an outer side in the turning direction of the hull is referred to as an outer propulsion machine, and the propulsion machine located on an inner side in the turning direction of the hull is referred to as an inner propulsion machine,in the switching control, the control unit sets a thrust of the outer propulsion machine to be greater than a thrust of the inner propulsion machine.

3. The propulsion system for a vessel according to claim 2, wherein, in the switching control, the control unit executes the intermittent control on the outer propulsion machine and sets the thrust of the inner propulsion machine to zero.

4. The propulsion system for a vessel according to claim 2, wherein, in the switching control, the control unit causes the outer propulsion machine to continuously generate the thrust and executes the intermittent control on the inner propulsion machine.

5. The propulsion system for a vessel according to claim 1, wherein, in the switching control, the control unit executes the intermittent control on one propulsion machine of the first propulsion machine and the second propulsion machine, and controls the thrust of the other propulsion machine on the basis of a second condition that is different from the first condition.

6. The propulsion system for a vessel according to claim 1, wherein the control unit performs the switching control in a case in which a steering command value in the turning direction is equal to or greater than a steering angle threshold value.

7. The propulsion system for a vessel according to claim 6, wherein the steering angle threshold value includesa right steering angle threshold value at which a course of the hull is changed to a right side with respect to a straight-ahead direction, anda left steering angle threshold value at which a course of the hull is changed to a left side with respect to a straight-ahead direction.

8. The propulsion system for a vessel according to claim 1,wherein the first condition is a vessel speed, andwherein the intermittent control switches a shift position of at least one of the propulsion machines from a forward position to a neutral position in a case in which the vessel speed is equal to or greater than a first speed threshold value, and switches the shift position from a neutral position to a forward position in a case in which the vessel speed is equal to or less than a second speed threshold value that is lower than the first speed threshold value.

9. The propulsion system for a vessel according to claim 1,wherein the first condition is a shift switching cycle that is set by combining a forward set time during which a forward position is continued and a neutral set time during which a neutral position is continued, andwherein the intermittent control switches a shift position of the propulsion machine between a forward position and a neutral position on the basis of the shift switching cycle.

10. The propulsion system for a vessel according to claim 2, further comprising a central propulsion machine provided between the first propulsion machine and the second propulsion machine,wherein, in the switching control, the control unit controls a thrust of the central propulsion machine in accordance with the outer propulsion machine.

11. The propulsion system for a vessel according to claim 1, further comprising:a third propulsion machine provided between the first propulsion machine and the second propulsion machine; anda fourth propulsion machine provided in a portion located close to the second propulsion machine in the leftward-rightward direction with respect to the third propulsion machine,wherein, in the switching control, the control unit controls a thrust of the third propulsion machine in accordance with the first propulsion machine, and controls a thrust of the fourth propulsion machine in accordance with the second propulsion machine.

12. The propulsion system for a vessel according to claim 1, wherein, during the intermittent driving mode, the control unit controls the first propulsion machine and the second propulsion machine such that orientations of the thrust of the first propulsion unit and the thrust of the second propulsion unit are the same direction.

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