Patent Publication Number: US-2023150642-A1

Title: Marine vessel including steering mechanism for marine vessel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2021-187174, filed on Nov. 17, 2021. The entire contents of this application are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a marine vessel including a steering mechanism. 
     2. Description of the Related Art 
     In recent years, with the aim of reducing the burden on a marine vessel operator, a marine vessel is configured to be able to set an autopilot mode in which the marine vessel automatically holds its course or the marine vessel automatically maintains its traveling direction without the marine vessel operator having to operate a steering wheel or a remote controller. In addition, when a passenger fishes, the marine vessel is configured to also be able to set a fixed point holding mode which automatically controls the movement of the marine vessel when the marine vessel is stopped so that the marine vessel stays at one point (for example, see Japanese Laid-Open Patent Publication (kokai) No. 2011-140272). 
     Conventionally, although automatic maneuvering switches that cause the marine vessel to shift to the autopilot mode and the fixed point holding mode, respectively, are provided on a panel or a joystick located at a maneuvering seat, since there is not much space for the panel or the joystick located at the maneuvering seat, providing the automatic maneuvering switches on the panel or the joystick located at the maneuvering seat will make it difficult to provide other switches, etc. on the panel or the joystick located at the maneuvering seat. Therefore, there is room for improvement in terms of flexibility in the layout of switches. 
     In addition, when shifting the marine vessel to the autopilot mode or the fixed point holding mode, since the marine vessel operator needs to operate the steering wheel with one hand and operate the automatic maneuvering switch provided on the panel or the joystick, which is spaced away from the steering wheel with the other hand, it is not easy for the marine vessel operator to operate the automatic maneuvering switch accurately. Therefore, there is also room for improvement in terms of operability of the switches. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide marine vessels including steering mechanisms that are each able to not only improve the flexibility in the layout of switches but also improve the operability of the switches. 
     According to a preferred embodiment of the present invention, a marine vessel includes a steering mechanism including a steering wheel. The steering wheel includes shift switches to cause the marine vessel to shift to a course holding mode to hold a course of the marine vessel, and a traveling direction maintaining mode to maintain a traveling direction of the marine vessel. 
     According to another preferred embodiment of the present invention, a marine vessel includes a steering mechanism including a steering wheel. The steering wheel includes shift switches to cause the marine vessel to shift to a position maintaining mode to keep the marine vessel at a predetermined position, a bow direction maintaining mode to maintain a bow direction of the marine vessel in a predetermined direction, and a fixed point holding mode to keep the marine vessel at the predetermined position and maintain the bow direction of the marine vessel in the predetermined direction. 
     According to another preferred embodiment of the present invention, a marine vessel includes a steering mechanism including a steering wheel. The steering wheel includes a shift switch to cause the marine vessel to shift to at least one of a course holding mode to hold a course of the marine vessel, a traveling direction maintaining mode to maintain a traveling direction of the marine vessel, a position maintaining mode to keep the marine vessel at a predetermined position, a bow direction maintaining mode to maintain a bow direction of the marine vessel in a predetermined direction, or a fixed point holding mode to keep the marine vessel at the predetermined position and maintain the bow direction of the marine vessel in the predetermined direction. 
     According to preferred embodiments of the present invention, the steering wheel includes the shift switches to cause the marine vessel to shift to the course holding mode, the traveling direction maintaining mode, the position maintaining mode, the bow direction maintaining mode, and the fixed point holding mode. As a result, since there is no need to necessarily provide the shift switches on the panel or the joystick, which is located at the maneuvering seat, it becomes easier to provide other switches on the panel or the joystick, which is located at the maneuvering seat, and the flexibility in the layout of the switches is improved. In addition, since it is possible for the marine vessel operator to operate the shift switches without taking his/her hands off the steering wheel, the operability of the shift switches is also be improved. As a result, it is possible to not only improve the flexibility in the layout of the switches but also improve the operability of the switches. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a marine vessel equipped with a steering mechanism according to a preferred embodiment of the present invention. 
         FIG.  2    is a perspective view of a principal portion of a maneuvering seat. 
         FIG.  3    is a block diagram for schematically explaining a configuration of a marine vessel maneuvering system of the marine vessel of  FIG.  1   . 
         FIG.  4    is a view for explaining a configuration of the steering mechanism. 
         FIG.  5 A  is a view for explaining Course Hold which is one of autopilot modes, and  FIG.  5 B  is a view for explaining Heading Hold which is one of the autopilot modes. 
         FIG.  6 A  is a view for explaining Drift Point™ which is one of fixed point holding modes,  FIG.  6 B  is a view for explaining Fish Point™ which is one of the fixed point holding modes, and  FIG.  6 C  is a view for explaining Stay Point™ which is one of the fixed point holding modes. 
         FIG.  7    is a view for explaining a fine adjustment of the course of the marine vessel in the autopilot mode. 
         FIG.  8 A  is a view for explaining Track Point which is one of the autopilot modes, and  FIG.  8 B  is a view for explaining Pattern Steer which is one of the autopilot modes. 
         FIG.  9    is a view for explaining a configuration of a modified example of a steering wheel included in a steering mechanism. 
         FIG.  10    is a side view of a modified example of a marine vessel including a steering mechanism according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 
       FIG.  1    is a perspective view of a marine vessel including a steering mechanism according to a preferred embodiment of the present invention. A marine vessel  1  includes a hull  2 , and a plurality of, for example, two outboard motors  3  that function as marine vessel propulsion devices and are mounted on the hull  2 . It should be noted that the number of the outboard motors  3  provided on the marine vessel  1  is not limited to two, and may be one or three or more. The two outboard motors  3  are mounted side by side on the stern of the hull  2 . Each outboard motor  3  includes an engine (not shown) which is an internal combustion engine functioning as a power source, and obtains a thrust from a propeller (not shown) which is rotated by a driving force of the corresponding engine. It should be noted that each outboard motor  3  may include an electric motor functioning as the power source, or may include both an engine and an electric motor functioning as the power source. 
     In addition, in the marine vessel  1 , a maneuvering seat  4  is provided on the bow side, which is the front portion of the hull  2 .  FIG.  2    is a perspective view of a principal portion of the maneuvering seat  4 . A steering mechanism  5  (hereinafter, also simply referred to as “a marine vessel steering mechanism  5 ”), a remote control switch  6 , a joystick  7 , a main operation unit  8 , an MFD (Multi Function Display)  9 , and an autopilot panel  10  are located on the maneuvering seat  4 . 
     The marine vessel steering mechanism  5  enables a marine vessel operator to determine the course of the marine vessel  1 . The marine vessel steering mechanism  5  includes a steering wheel  11  which is rotatably operated. The marine vessel operator is able to turn the marine vessel  1  left or right by rotatably operating the steering wheel  11  left or right. The remote control switch  6  includes levers  12  corresponding to the outboard motors  3 , respectively. By operating each lever  12 , the marine vessel operator is able to switch a direction of the thrust generated by the corresponding outboard motor  3  between a forward moving direction and a backward moving direction, and adjust the output of the corresponding outboard motor  3  so as to adjust a vessel speed of the marine vessel  1 . 
     The joystick  7  is able to be operated to be tilted forward, backward, leftward, and rightward, and also able to be operated to rotate about an axis. By operating the joystick  7 , the marine vessel operator is able to navigate the marine vessel  1  with a course corresponding to a tilting direction of the joystick  7  and a thrust corresponding to a tilting amount of the joystick  7 . In a normal mode, the outboard motor  3  works mainly according to an operation of the marine vessel steering mechanism  5  and an operation of the remote control switch  6 . On the other hand, in a joystick mode, the outboard motor  3  works mainly according to the operation of the joystick  7 . It is possible to switch between the normal mode and the joystick mode by a change-over switch (not shown). In addition, the joystick  7  includes a plurality of shift switches (not shown) that cause the marine vessel  1  to shift to a plurality of fixed point holding modes, respectively. That is, one of the plurality of the shift switches located on the joystick  7  causes the marine vessel  1  to shift to one of the plurality of the fixed point holding modes. 
     The main operation unit  8  includes a main switch  13  and an emergency switch  14 . The main switch  13  (one main switch  13 ) is provided in common for the outboard motors  3  (respective outboard motors  3 ). The main switch  13  is an operation piece to collectively start and collectively stop the engines of the outboard motors  3  (the respective outboard motors  3 ). 
     The MFD  9  is, for example, a color LCD display. The MFD  9  functions to display various kinds of information, and also functions as a touch panel that accepts inputs from the marine vessel operator. For example, the MFD  9  displays a rotation speed of the engine of each outboard motor  3  and the vessel speed of the marine vessel  1 , and accepts settings of the course of the marine vessel  1  in Track Point, which is one of autopilot modes described below. 
     A plurality of shift switches that cause the marine vessel  1  to shift to a plurality of autopilot modes, respectively, are located on the autopilot panel  10 . That is, one of the plurality of the shift switches located on the autopilot panel  10  causes the marine vessel  1  to shift to one of the plurality of the autopilot modes. The marine vessel operator is able to shift the marine vessel  1  to a desired autopilot mode by operating a desired shift switch. 
       FIG.  3    is a block diagram for schematically explaining a configuration of a marine vessel maneuvering system of the marine vessel  1 . As shown in  FIG.  3   , in addition to the outboard motors  3 , the marine vessel steering mechanism  5 , the remote control switch  6 , the joystick  7 , the main operation unit  8 , the MFD  9 , and the autopilot panel  10  that are described above, the marine vessel maneuvering system of the marine vessel  1  includes a GPS (Global Positioning System)  15 , an HS (Heading Sensor)  16 , a remote control ECU (Engine Control Unit)  18  functioning as a controller, SCUs (Steering Control Units)  19 , and a steering shaft sensor  20 . 
     The GPS  15  obtains the current position of the marine vessel  1  and transmits the current position of the marine vessel  1  to the remote control ECU  18  as position information. The HS  16  incorporates direction sensors (azimuth sensors) such as a yaw sensor, a roll sensor, and a pitch sensor, an acceleration sensor that measures an acceleration of the marine vessel  1  in a front-rear direction (a longitudinal direction), an acceleration sensor that measures an acceleration of the marine vessel  1  in a left/right direction, and an acceleration sensor that measures an acceleration of the marine vessel  1  in a vertical direction. The HS  16  transmits a direction of the marine vessel  1  and the respective accelerations (movement) of the marine vessel  1  to the remote control ECU  18 . 
     The remote control ECU  18  is a main controller of the marine vessel maneuvering system, and controls operations of respective components of the marine vessel maneuvering system according to digital signals that will be described below, and various kinds of programs. In addition, the remote control ECU  18  controls the engine of each outboard motor  3  according to the operation of each lever  12  of the remote control switch  6 . The SCU  19  is provided corresponding to each outboard motor  3 , and controls a steering unit that horizontally turns the corresponding outboard motor  3  with respect to the hull  2  of the marine vessel  1  so as to change an acting direction of the thrust of each outboard motor  3 . The steering shaft sensor  20  detects a rotation angle (an operation angle) of the steering wheel  11  of the marine vessel steering mechanism  5 . 
     In the marine vessel maneuvering system, the respective components are connected to each other by a CAN (Control Area Network)  21  that is a network in which a plurality of nodes are individually connected to a bus. In the CAN  21 , operation inputs to the respective components are transmitted as the digital signals to the remote control ECU  18  via the bus. 
     In addition, in the marine vessel maneuvering system, the remote control switch  6  is connected to the remote control ECU  18  not only by the CAN  21  but also by individual wiring (see a broken line in  FIG.  3   ), and the main operation unit  8  is connected to the remote control ECU  18  not by the CAN  21  but by individual wiring (see a broken line in  FIG.  3   ). The operation input to each lever  12  of the remote control switch  6  is transmitted also as an analog signal to the remote control ECU  18 , and the operation input to the main switch  13  of the main operation unit  8  and the operation input to the emergency switch  14  of the main operation unit  8  are also transmitted as analog signals to the remote control ECU  18 . 
     It should be noted that in the marine vessel maneuvering system, the respective components may be connected to each other not by the CAN but by a LAN (Local Area Network) such as Ethernet (registered trademark) that performs connecting via a network device, or the respective components may be directly connected to each other. Also in this case, the operation inputs to the respective components are transmitted as the digital signals to the remote control ECU  18 . 
       FIG.  4    is a view for explaining a configuration of the marine vessel steering mechanism  5 .  FIG.  4    shows a case that the marine vessel steering mechanism  5  is viewed from the side of the marine vessel operator. It should be noted that a vertical direction and a left/right direction of  FIG.  4    correspond to the vertical direction and the left/right direction of the marine vessel  1 , the depth side of  FIG.  4    is the bow side of the marine vessel  1 , and the front side of  FIG.  4    is the stern side of the marine vessel  1 . 
     As shown in  FIG.  4   , the marine vessel steering mechanism  5  includes the steering wheel  11 , and a column portion  26  that pivotally and rotatably supports the steering wheel  11 . The steering wheel  11  includes a central portion  28  that is supported rotatably around a rotation fulcrum (a steering shaft)  27  with respect to the column portion  26 , a wheel portion  29  that has an annular shape, and for example, three spoke portions (spoke portions  30 ,  31 , and  32 ) that connect the central portion  28  and the wheel portion  29 . 
     When the steering wheel  11  is at a position that makes the marine vessel  1  move straight, the spoke portion  30  is positioned below a virtual plane  33  passing through the rotation fulcrum  27  and parallel to the left/right direction, and extends downward from the rotation fulcrum  27 . 
     Further, when the steering wheel  11  is at the position that makes the marine vessel  1  move straight, the spoke portion  31  is positioned above the virtual plane  33 , and extends from the rotation fulcrum  27  so as to be positioned within an angle range from about 0° to about 60° clockwise with respect to the virtual plane  33  in a circumferential direction about the rotation fulcrum  27  (within an angle range indicated by θ 1  in  FIG.  4   ), preferably, so as to be positioned within an angle range from about 20° to about 40° clockwise with respect to the virtual plane  33  in the circumferential direction about the rotation fulcrum  27  (within an angle range indicated by θ 2  in  FIG.  4   ). 
     Furthermore, when the steering wheel  11  is at the position that makes the marine vessel  1  move straight, the spoke portion  32  is positioned above the virtual plane  33 , and extends from the rotation fulcrum  27  so as to be positioned within an angle range from about 0° to about 60° counterclockwise with respect to the virtual plane  33  in the circumferential direction about the rotation fulcrum  27  (within an angle range indicated by θ 3  in  FIG.  4   ), preferably, so as to be positioned within an angle range from about 20° to about 40° counterclockwise with respect to the virtual plane  33  in the circumferential direction about the rotation fulcrum  27  (within an angle range indicated by θ 4  in  FIG.  4   ). 
     In a preferred embodiment of the present invention, there are a plurality of autopilot modes and a plurality of fixed point holding modes, to which the marine vessel  1  is able to shift. For example, the marine vessel  1  is able to shift to Course Hold (a course holding mode) which is one of the plurality of the autopilot modes, or Heading Hold (a traveling direction maintaining mode) which is one of the plurality of the autopilot modes. Furthermore, the marine vessel  1  is able to shift to Fish Point™ (a position maintaining mode) which is one of the plurality of the fixed point holding modes, Drift Point™ (a bow direction maintaining mode) which is one of the plurality of the fixed point holding modes, or Stay Point™ which is one of the plurality of the fixed point holding modes. It should be noted that Fish Point™, Drift Point™, and Stay Point™ are all registered trademarks. 
     As shown in  FIG.  5 A , in the Course Hold which is an autopilot mode, when the marine vessel  1  navigates, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  follows a set course  35  even when subjected to external disturbances  34  such as wind and water currents. It should be noted that in  FIGS.  5 A,  5 B,  6 A to  6 C,  7 ,  8 A, and  8 B , an arrow included in the marine vessel  1  indicates the acting direction of the thrust. Furthermore, as shown in  FIG.  5 B , in the Heading Hold which is an autopilot mode, when the marine vessel  1  navigates, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  maintains a set heading (a set bow direction) even when subjected to the external disturbances  34  such as the wind and the water currents. 
     As shown in  FIG.  6 A , in the Drift Point™ which is a fixed point holding mode, when the marine vessel  1  is stopped, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  maintains the set heading (the set bow direction) even when subjected to the external disturbances  34  such as the wind and the water currents. It should be noted that in the Drift Point™, the movement of the marine vessel  1  is not actively restricted and the movement of the marine vessel  1  due to the external disturbances  34  is allowed. Furthermore, as shown in  FIG.  6 B , in the Fish Point™ which is a fixed point holding mode, in the case that the marine vessel  1  is stopped, when the marine vessel  1  is subjected to the external disturbances  34  such as the wind and the water currents, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the bow or the stern of the marine vessel  1  is opposed to the flow of the wind and the water currents and the marine vessel  1  stays at one point (one spot). Moreover, as shown in  FIG.  6 C , in the Stay Point™ which is a fixed point holding mode, when the marine vessel  1  is stopped, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  maintains the set heading (the set bow direction) and the marine vessel  1  stays at one point (one spot) even when subjected to the external disturbances  34  such as the wind and the water currents. 
     In a preferred embodiment of the present invention, shift switches that cause the marine vessel  1  to shift to the autopilot modes described above and the fixed point holding modes described above, respectively, are located on the steering wheel  11 . 
     Returning to  FIG.  4   , the spoke portion  31  of the steering wheel  11  is provided with a heading hold switch  36  (the shift switch) that causes the marine vessel  1  to shift to the Heading Hold. In addition, the spoke portion  32  of the steering wheel  11  is provided with a course hold switch  37  (the shift switch) that causes the marine vessel  1  to shift to the Course Hold. In particular, it is preferable that the heading hold switch  36  and the course hold switch  37  are located within a range that fingers of the marine vessel operator who is gripping the wheel portion  29 , for example, thumbs, can reach. It should be noted that the heading hold switch  36  may be located on the spoke portion  32  and the course hold switch  37  may be located on the spoke portion  31 . 
     In the marine vessel  1  that is navigating, sometimes the marine vessel operator grips the wheel portion  29  while standing, at that time, since the marine vessel operator holds the wheel portion  29  from above, the marine vessel operator grips the upper half of the wheel portion  29 , particularly grips the vicinity where the wheel portion  29  intersects the spoke portions  31  and  32 . Therefore, in the case that the heading hold switch  36  and the course hold switch  37  are located within the range that the thumbs of the marine vessel operator who is gripping the wheel portion  29  can reach, since the marine vessel operator is able to operate the heading hold switch  36  and the course hold switch  37  with his or her thumbs without regripping the wheel portion  29 , the operability of the heading hold switch  36  and the course hold switch  37  is improved. 
     When the heading hold switch  36  or the course hold switch  37  is operated, specifically, when the heading hold switch  36  or the course hold switch  37  is pressed down, in the CAN  21 , the operation input to the heading hold switch  36  or the course hold switch  37  operated (pressed down) is transmitted as the digital signal to the remote control ECU  18 . In order to realize the Course Hold or the Heading hold, the remote control ECU  18  transmits control signals to each SCU  19  and an ECU (Engine Control Unit) (not shown) of each outboard motor  3  to control the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3 . After the marine vessel  1  shifts to the autopilot mode, when the marine vessel operator operates the heading hold switch  36  or the course hold switch  37  again, or rotates the wheel portion  29  by a predetermined amount or more, the autopilot mode is released. 
     Furthermore, in the case of shifting the marine vessel  1  to the Heading hold or the Course Hold, although the marine vessel  1  is often navigating at a high speed, for example, at about 50 knots, in a preferred embodiment of the present invention, it is possible for the marine vessel operator to operate the heading hold switch  36  or the course hold switch  37  without taking his/her hands off the wheel portion  29 . Therefore, when the marine vessel operator shifts the marine vessel  1  to the autopilot mode, the marine vessel operator is able to keep holding the wheel portion  29  of the marine vessel  1  navigating at the high speed, and as a result, it is possible to easily maintain the course of the marine vessel  1 . 
     In addition, in a preferred embodiment of the present invention, it is possible to perform a fine adjustment of the course of the marine vessel  1  in the autopilot mode. As shown in  FIG.  7   , with respect to the set course  35 , it is possible to slightly change the course of the marine vessel  1  toward the starboard direction or the port direction. In order to change the course of the marine vessel  1 , when the wheel portion  29  is rotated, as described above, since there is a possibility that the autopilot mode will be released, in a preferred embodiment of the present invention, the fine adjustment of the course of the marine vessel  1  is performed with switches. These switches are located on the steering wheel  11 . Specifically, in the spoke portion  31 , within the range that the fingers of the marine vessel operator who is gripping the wheel portion  29  can reach, a heading changing switch  38  (a course adjusting switch) that finely adjusts the course of the marine vessel  1  toward the port direction is located so as to be adjacent to the heading hold switch  36 . Further, in the spoke portion  32 , within the range that the fingers of the marine vessel operator who is gripping the wheel portion  29  can reach, a heading changing switch  39  (a course adjusting switch) that finely adjusts the course of the marine vessel  1  toward the starboard direction is located so as to be adjacent to the course hold switch  37 . It should be noted that in the spoke portion  31 , the heading changing switch  38  may be located on a range other than the range that the fingers of the marine vessel operator who is gripping the wheel portion  29  can reach. Also, it should be noted that in the spoke portion  32 , the heading changing switch  39  may be located on a range other than the range that the fingers of the marine vessel operator who is gripping the wheel portion  29  can reach. 
     When the heading changing switch  38  or the heading changing switch  39  is operated, specifically, when the heading changing switch  38  or the heading changing switch  39  is pressed down, in the CAN  21 , the operation input to the heading changing switch  38  or the heading changing switch  39  operated (pressed down) is transmitted as the digital signal to the remote control ECU  18 . In order to slightly change the course of the marine vessel  1 , the remote control ECU  18  transmits control signals to each SCU  19  and the ECU (not shown) of each outboard motor  3  to control the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3 . It should be noted that the remote control ECU  18  changes a change amount of the course of the marine vessel  1  according to the number of times of operations of the heading changing switch  38  or the heading changing switch  39 . Specifically, as the number of times of the operations of the heading changing switch  38  increases, the change amount of the course of the marine vessel  1  toward the port direction is increased. In addition, as the number of times of the operations of the heading changing switch  39  increases, the change amount of the course of the marine vessel  1  toward the starboard direction is increased. 
     Since the heading changing switch  38  and the heading changing switch  39  are located adjacent to the heading hold switch  36  and the course hold switch  37 , respectively, the marine vessel operator is able to operate the heading changing switch  38  and the heading changing switch  39  without regripping the wheel portion  29 , and as a result, the operability of the heading changing switch  38  and the heading changing switch  39  is improved. In particular, in the marine vessel  1  that has shifted to the autopilot mode and is navigating at the high speed, since the marine vessel operator is able to change the course of the marine vessel  1  without taking his/her hands off the wheel portion  29 , it is possible to further enhance the operability of the heading changing switch  38  and the heading changing switch  39 . 
     In addition, since the heading changing switch  38  which finely adjusts the course of the marine vessel  1  toward the port direction is located on the spoke portion  31  which is located on the port side when the steering wheel  11  is at the position that makes the marine vessel  1  move straight, and the heading changing switch  39  which finely adjusts the course of the marine vessel  1  toward the starboard direction is located on the spoke portion  32  which is located on the starboard side when the steering wheel  11  is at the position that makes the marine vessel  1  move straight, when the marine vessel operator wants to slightly change the course of the marine vessel  1  toward a desired direction, the marine vessel operator just needs to operate the heading changing switch for the desired direction. Therefore, the marine vessel operator is able to intuitively navigate the marine vessel  1  by using the heading changing switch, and as a result, the burden on the marine vessel operator is reduced. 
     In addition, in a preferred embodiment of the present invention, as the autopilot modes, the marine vessel  1  can shift not only to the Course Hold and the Heading Hold, but also, for example, to the Track Point and Pattern Steer. As shown in  FIG.  8 A , in the Track Point, a course  42  is set to pass through waypoints  40  and  41 , which are set in advance by the marine vessel operator, for example, in the MFD  9 , and the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  navigates along the course  42 . Furthermore, as shown in  FIG.  8 B , in the Pattern Steer, the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3  are controlled so that the marine vessel  1  navigates according to a navigating pattern, which is set in advance by the marine vessel operator, for example, in the MFD  9 . In  FIG.  8 B , although a spiral pattern that continues spiral movement is set as the navigating pattern, a zigzag pattern that continues zigzag movement can also be set as the navigating pattern. 
     Although there are no dedicated switches which cause the marine vessel  1  to shift to the Track Point and the Pattern Steer, respectively, on the steering wheel  11 , as described above, since the heading hold switch  36  and the course hold switch  37  transmit the digital signals according to the operation inputs to the heading hold switch  36  and the course hold switch  37 , it is possible to assign shifting to the Track Point and shifting to the Pattern Steer to these digital signals. Accordingly, by operating the heading hold switch  36  or the course hold switch  37 , it is possible to shift the marine vessel  1  to the Track Point or the Pattern Steer. For example, in the MFD  9 , the marine vessel operator is able to change assigning of functions to the digital signals transmitted by the heading hold switch  36  and the course hold switch  37 . 
     Also, the functions of the heading hold switch  36  and the course hold switch  37  may be switched according to the operation of a switch  43  located on the spoke portion  30  of the steering wheel  11 . Specifically, each time the switch  43  is operated, the function of the heading hold switch  36  may be switched between shifting to the Heading Hold and shifting to the Track Point. In addition, each time the switch  43  is operated, the function of the course hold switch  37  may be switched between shifting to the Course Hold and shifting to the Pattern Steer. 
     It should be noted that since the course of the marine vessel  1  is changed in the Track Point and the Pattern Steer, it is preferable to avoid shifting to the Track Point due to carelessness of the marine vessel operator and shifting to the Pattern Steer due to carelessness of the marine vessel operator. In response to this, it is preferable so that the marine vessel  1  does not shift to the Track Point or the Pattern Steer unless the heading hold switch  36  or the course hold switch  37  is operated (is pressed down) for a predetermined period of time or longer. 
     In addition, a fish point switch  44  (the shift switch) that causes the marine vessel  1  to shift to the Fish Point™, a stay point switch  45  (the shift switch) that causes the marine vessel  1  to shift to the Stay Point™, and a drift point switch  46  (the shift switch) that causes the marine vessel  1  to shift to the Drift Point™ are located on the spoke portion  30  of the steering wheel  11 . 
     When the fish point switch  44 , the stay point switch  45 , or the drift point switch  46  is operated, specifically, when the fish point switch  44 , the stay point switch  45 , or the drift point switch  46  is pressed down, in the CAN  21 , the operation input to the fish point switch  44 , the stay point switch  45 , or the drift point switch  46  is transmitted as the digital signal to the remote control ECU  18 . In order to realize the Fish Point, the Stay Point™, or the Drift Point™, the remote control ECU  18  transmits control signals to each SCU  19  and the ECU of each outboard motor  3  to control the thrust of each outboard motor  3  and the acting direction of the thrust of each outboard motor  3 . 
     Operations of the fish point switch  44 , the stay point switch  45 , and the drift point switch  46  are disabled unless in a state that each lever  12  of the remote control switch  6  is positioned at N (neutral) and the engine of each outboard motor  3  is disconnected from the propeller by a clutch or the like. 
     After the marine vessel  1  shifts to the fixed point holding mode, when the marine vessel operator operates the fish point switch  44 , the stay point switch  45 , or the drift point switch  46  again, or moves the position of each lever  12  of the remote control switch  6  from N (neutral) to another position, the fixed point holding mode is released. 
     As described above, in the marine vessel  1  that is navigating, since the marine vessel operator grips the vicinity where the wheel portion  29  intersects the spoke portions  31  and  32 , the fingers of the marine vessel operator cannot reach the spoke portion  30  extending downward from the rotation fulcrum  27 . Therefore, when the marine vessel  1  is navigating, the marine vessel operator will not erroneously operate the fish point switch  44 , the stay point switch  45 , and the drift point switch  46  which are assumed to be operated when the marine vessel  1  is navigating at a low speed or when the marine vessel  1  is stopped. In addition, since the fish point switch  44 , the stay point switch  45 , and the drift point switch  46  are located at places where it is difficult to operate when the marine vessel  1  is navigating, the marine vessel operator is able to intuitively understand that these switches are assumed to be operated when the marine vessel  1  is navigating at the low speed or when the marine vessel  1  is stopped. 
     In addition, in a preferred embodiment of the present invention, it is possible to set a level of the thrust of each outboard motor  3  to adjust the position of the marine vessel  1  in the fixed point holding mode, for example, it is possible to set the level of the thrust generated by each outboard motor  3  in order to keep the marine vessel  1  at one point in the Fish Point™. In a preferred embodiment of the present invention, the level of the thrust is set with two switches. These two switches are also located on the steering wheel  11 . Specifically, a thrust level setting switch  47 , which decreases the level of the thrust, is located on the spoke portion  31 , and a thrust level setting switch  48 , which increases the level of the thrust, is located on the spoke portion  32 . 
     When the thrust level setting switch  47  or the thrust level setting switch  48  is operated, specifically, when the thrust level setting switch  47  or the thrust level setting switch  48  is pressed down, in the CAN  21 , the operation input to the thrust level setting switch  47  or the thrust level setting switch  48  is transmitted as the digital signal to the remote control ECU  18 . The remote control ECU  18  changes the level of the thrust of each outboard motor  3  generated in the fixed point holding mode. It should be noted that the remote control ECU  18  changes the level of the thrust according to the number of times of operations of the thrust level setting switch  47  or the thrust level setting switch  48 . Specifically, as the number of times of the operations of the thrust level setting switch  48  increases, the level of the thrust generated in the fixed point holding mode is increased. In addition, as the number of times of the operations of the thrust level setting switch  47  increases, the level of the thrust generated in the fixed point holding mode is decreased. 
     According to a preferred embodiment of the present invention, the shift switches  36 ,  37 ,  44 ,  45 , and  46  that cause the marine vessel  1  to shift to the autopilot modes and the fixed point holding modes, respectively, are located on the steering wheel  11 . This eliminates the need for the marine vessel operator to operate the automatic maneuvering switch provided on the panel or the joystick, which is spaced away from the steering wheel  11 , in order to shift the marine vessel  1  to the autopilot mode or the fixed point holding mode. In particular, since the heading hold switch  36  and the course hold switch  37  are located within the range that the fingers of the marine vessel operator who is gripping the wheel portion  29  can reach, the marine vessel operator is able to shift the marine vessel  1  to the autopilot mode without taking his/her hands off the wheel portion  29  of the steering wheel  11 . As a result, it is possible to improve the operability of the shift switches  36 ,  37 ,  44 ,  45 , and  46 . 
     Furthermore, when the marine vessel  1  is navigating, although the steering wheel  11  often comes into the field of view of the marine vessel operator, in a preferred embodiment of the present invention, since the shift switches  36 ,  37 ,  44 ,  45 , and  46  are located on the steering wheel  11 , it is also possible to improve the visibility of the shift switches  36 ,  37 ,  44 ,  45 , and  46 . 
     Moreover, in a preferred embodiment of the present invention, since the shift switches that cause the marine vessel  1  to shift to the autopilot modes and the fixed point holding modes, respectively, do not necessarily have to be located on the panel or the joystick, which is located at the maneuvering seat  4 , it is possible to provide other switches on the panel or the joystick, which is located at the maneuvering seat  4 , and as a result, it is possible to improve the flexibility in the layout of the other switches. In addition, in a preferred embodiment of the present invention, the marine vessel maneuvering system of  FIG.  3    can be provided on the marine vessel  1  only by providing the marine vessel steering mechanism  5  including the steering wheel  11  on the marine vessel  1  without providing the shift switches  36 ,  37 ,  44 ,  45 , and  46  on the panel or the joystick, which is located at the maneuvering seat  4 , and it is possible to easily realize the autopilot modes and the fixed point holding modes. 
     Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described preferred embodiments, and various modifications and changes can be made within the scope of the gist thereof. 
     For example, the locations of the shift switches  36 ,  37 ,  44 ,  45 , and  46  are not limited to the spoke portions  30 ,  31 , and  32 , as an example, at least one of the shift switches  36 ,  37 ,  44 ,  45 , and  46  may be located on the column portion  26 , the central portion  28 , or the wheel portion  29 . Similarly, locations of the heading changing switches  38  and  39 , and the thrust level setting switches  47  and  48  may be the column portion  26 , the central portion  28 , or the wheel portion  29 . 
     Further, each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  may be provided with an indicator indicating that the marine vessel  1  has shifted to the corresponding mode according to the operation input. For example, each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  is provided with a small lighting unit (for example, an LED lamp), and when each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  is operated and the marine vessel  1  shifts to the corresponding mode, the lighting unit lights up. Alternatively, each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  is provided with a backlight unit, and when each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  is operated and the marine vessel  1  shifts to the corresponding mode, light emitted from the backlight unit is transmitted through a printed portion (for example, a character string “STAY POINT”) of the shift switches  36 ,  37 ,  44 ,  45 , and  46 , and the printed portion emits light. This allows the marine vessel operator to easily understand whether or not the marine vessel  1  has shifted to a desired mode. 
     It should be noted that regardless of whether or not the shift switch is operated, the printed portion of each of the shift switches  36 ,  37 ,  44 ,  45 , and  46  may be illuminated by the backlight unit. In this case, it is possible to improve the visibility of the shift switches  36 ,  37 ,  44 ,  45 , and  46  in the marine vessel  1  navigating at dusk or at night. 
     Furthermore, as shown in  FIG.  9   , instead of the wheel portion  29  having an annular shape, the steering wheel  11  on which the shift switches  36 ,  37 ,  44 ,  45 , and  46  are located may be provided with handlebars  49  and  50  that are located on the right and the left, respectively. In this case, the heading hold switch  36 , the heading changing switch  38 , and the thrust level setting switch  47  are located on a spoke portion  51  that connects the handlebar  49  located on the port side and the central portion  28 , and the course hold switch  37 , the heading changing switch  39 , and the thrust level setting switch  48  are located on a spoke portion  52  that connects the handlebar  50  located on the starboard side and the central portion  28 . 
     In addition, since the shift switches  36 ,  37 ,  44 ,  45 , and  46 , the heading changing switches  38  and  39 , and the thrust level setting switches  47  and  48  transmit the digital signals according to the operation inputs to the shift switches  36 ,  37 ,  44 ,  45 , and  46 , the heading changing switches  38  and  39 , and the thrust level setting switches  47  and  48 , it is possible to assign respective switches to functions other than the functions described above by associating the digital signals with other functions. For example, it is possible to assign a lateral movement mode toward the port direction to the heading changing switch  38  and assign a lateral movement mode toward the starboard direction to the heading changing switch  39 . In addition, it is possible to assign a dock hold mode toward the port direction to the heading hold switch  36  and assign a dock hold mode toward the starboard direction to the course hold switch  37 . It should be noted that the marine vessel operator is able to assign other functions to respective switches by using, for example, the MFD  9 . 
     Although the marine vessel steering mechanism  5  according to preferred embodiments of the present invention is applied to the marine vessel  1  including the two outboard motors  3 , there is no limitation on the type of the marine vessel to which the marine vessel steering mechanism  5  is applied, and it may be applied to a marine vessel including inboard/outboard motors or inboard motors, and for example, as shown in  FIG.  10   , it may be applied to a jet boat  54 , which is a marine vessel that has at least one of an engine or an electric motor built into its hull and navigates by the thrust of a water jet  53 . 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.