Abstract:
A watercraft includes a plurality of outboard motors. Each of the outboard motors has a generator and a rudder deflecting system driven by an electric motor. The outboard motors are turned by the rudder deflecting systems thereby steering the watercraft. Electric power can be supplied from the generators of others of the plurality of outboard motors to the rudder deflecting system of an arbitrary outboard motor among the plurality of the outboard motors. Using this arrangement it is possible to provide a watercraft in which electric power for operation is stably supplied to the rudder deflecting system without increasing the size of the generators.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a watercraft having a plurality of watercraft propulsion units, a generator disposed in each of the watercraft propulsion units, and a rudder deflecting system disposed in each of the watercraft propulsion units. The watercraft propulsion units are turned by the rudder deflecting systems thereby steering the watercraft. 
     2. Description of the Related Art 
     Conventionally, there are watercrafts of the kind described above, as shown in  FIGS. 10 ,  11 A, and  11 B. The watercraft has a plurality of, herein two, outboard motors  1  as watercraft propulsion units. A generator  2  and a main battery  3  are connected to each of the outboard motors  1 . The outboard motors  1  are steered by rudder deflecting systems  4 . 
     That is, when an operator of the watercraft rotates a steering wheel (not shown), a rotational angle of the steering wheel is detected, and the signal is sent to the rudder deflecting system  4  of the outboard motor  1 . An electric motor of the rudder deflecting system  4  is driven with electric power from the generator  2 , the main battery  3 , and the like, and the outboard motor  1  is steered. 
     On the other hand, when electric power from the main battery  3  is supplied to a starter motor of an engine of each of the outboard motors  1  and the engine is started, the generator  2  generates electric power from the drive of the engine. The main battery  3  is charged, and electric power is supplied to the rudder deflecting system  4 . 
     The generator  2  also supplies electric power to a PTT (power trim and tilt system), an auxiliary device, and the like. 
     Further, a sub-battery (accessory battery)  5  is connected to the two generators  2 . The sub-battery  5  supplies electric power to accessory devices such as an engine speed sensor, fishfinder, GPS, etc. (not shown). JP-A-2001-128388 discloses a watercraft of this kind. 
     However, in this kind of conventional watercraft, the generator  2  generates electric power for each of the outboard motors  1 , and this electric power is supplied only to the rudder deflecting system  4  and the like of the individual outboard motor  1 . 
     That is, a steering force acts on the outboard motor  1  because of a propeller reaction force, and thus the outboard motor  1  constantly requires steering. A steering load to one of the outboard motors  1  (for example, the outboard motor  1  on the starboard side) is larger than a steering load to the other outboard motor  1  (for example, the outboard motor  1  on the port side) in the case that the watercraft having a plurality of outboard motors  1  is turning, for example. 
     As a result, as shown in  FIG. 11A , the main battery  3  of the outboard motor  1  on the port side is charged since consumption of electric power is smaller than an amount of generated electric power on that side. However, the main battery  3  of the outboard motor on the starboard side discharges electric power since consumption of electric power is larger than an amount of generated electric power on that side. 
     Therefore, the main battery  3  of the starboard side outboard motor  1  tends to be insufficiently charged, which causes the rudder deflecting system  4  to have an insufficient output. 
     To cope with this circumstance, the generator  2  may be arranged to supply the maximum electric power required by the outboard motor  1 . However, this results in increases in both the size of the generator  2  and the cost. 
     SUMMARY OF THE INVENTION 
     In order to overcome the problems described above, preferred embodiments of the present invention provide a watercraft in which operational electric power is stably and reliably supplied to the rudder deflecting system without increasing a size of a generator. 
     A first preferred embodiment of the present invention provides a watercraft having a plurality of watercraft propulsion units. Each of the watercraft propulsion units has a generator and a rudder deflecting system arranged therein. Each of the watercraft propulsion unit includes an electric motor for supplying a driving force. The watercraft propulsion units are turned by operation of the rudder deflecting systems, and the watercraft is steered thereby. Additionally, electric power can be supplied from the generators of the other watercraft propulsion units to the rudder deflecting system of any other watercraft propulsion unit among the plurality of the watercraft propulsion units. 
     A second preferred embodiment of the present invention provides a watercraft in which a main battery preferably is provided for each of the plurality of the watercraft propulsion units while being connected thereto. The main battery is capable of supplying electric power to the rudder deflecting system of the watercraft propulsion unit and to not supply electric power to the rudder deflecting systems of the other watercraft propulsion units. 
     A third preferred embodiment of the present invention provides a watercraft in which a main battery is provided for each of the plurality of the watercraft propulsion units while being connected thereto, and electric power is supplied from the generators of the other watercraft propulsion units to the main battery of an arbitrary watercraft propulsion unit. 
     A fourth preferred embodiment of the present invention provides a watercraft in which a sub-battery is connected to the plurality of watercraft propulsion units, and electric power is supplied from the sub-battery to each of the main batteries. 
     A fifth preferred embodiment of the present invention provides a watercraft in which a plurality of generators are provided for each of the watercraft propulsion units, an arbitrary generator among the plurality of generators is connected to the main battery, and the other generators are connected to rudder deflecting systems of the other watercraft propulsion units. 
     In the first preferred embodiment of the present invention, electric power can be supplied from the generators of the other watercraft propulsion units to the rudder deflecting system of an arbitrary watercraft propulsion unit among the plurality of the watercraft propulsion units. Therefore, electric power can be stably and reliably supplied to the rudder deflecting systems without increasing a size of the generator. 
     In the second preferred embodiment of the present invention, the watercraft is constructed such that the main battery is provided for each of the plurality of the watercraft propulsion units while being connected thereto. The main battery is capable of supplying electric power to the rudder deflecting system of the watercraft propulsion unit and to not supply electric power to the rudder deflecting systems of the other watercraft propulsion units. Accordingly, a reduction in the amount of electric power used for charging the main battery can be prevented since the generator does not supply electric power to the rudder deflecting systems of the other watercraft propulsion units. 
     In the third preferred embodiment of the present invention, electric power is supplied from the generators of the other watercraft propulsion units to the main battery of an arbitrary watercraft propulsion unit. Therefore, the amount of electric power required for charging the main battery can be assured. 
     In the fourth preferred embodiment of the present invention, the watercraft is constructed such that electric power is supplied from the sub-battery to each of the main batteries. Therefore, the amount of electric power required for charging each of the main batteries can be ensured. 
     In the fifth preferred embodiment of the present invention, the plurality of generators are provided for each of the watercraft propulsion units, an arbitrary generator among the plurality of generators is connected to the main battery, and the other generators are connected to the rudder deflecting systems of the other watercraft propulsion units. Accordingly, the amount of electric power required for charging the main battery can be ensured, and electric power can be appropriately supplied to the rudder deflecting systems of the other watercraft propulsion units. 
     Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a watercraft in accordance with a first preferred embodiment of the present invention. 
         FIG. 2  is a plan view showing a rudder deflecting system and the like in accordance with the first preferred embodiment of the present invention. 
         FIG. 3  is a side view of a rear portion of the watercraft in accordance with the first preferred embodiment of the present invention. 
         FIG. 4  is a block diagram of various devices for supplying electric power to the rudder deflecting systems in accordance with the first preferred embodiment of the present invention. 
         FIG. 5  is an explanatory plan view showing a turning state of the watercraft in accordance with the first preferred embodiment of the present invention. 
         FIGS. 6A and 6B  are explanatory diagrams for explaining the first preferred embodiment,  FIG. 6A  is a graph indicating an amount of generated electric power and a consumption of electric power in the outboard motors on a port side and a starboard side, and  FIG. 6B  is a graph indicating amounts of electric power for charging a main battery and electric power discharged from a main battery. 
         FIG. 7  is a block diagram of various devices for supplying electric power to the rudder deflecting systems in accordance with a second preferred embodiment of the present invention. 
         FIG. 8  is a block diagram of various devices for supplying electric power to the rudder deflecting systems in accordance with a third preferred embodiment of the present invention. 
         FIG. 9  is a block diagram of various devices for supplying electric power to the rudder deflecting systems in accordance with a fourth preferred embodiment of the present invention. 
         FIG. 10  is a block diagram of various devices for supplying electric power to rudder deflecting systems in the conventional art. 
         FIGS. 11A and 11B  are explanatory diagrams explaining the conventional art, wherein  FIG. 11A  is a graph indicating an amount of generated electric power and a consumption of electric power in outboard motors on a port side and a starboard side, and  FIG. 11B  is a graph indicating amounts of electric power for charging a main battery and electric power discharged from a main battery. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described with reference to the figures. 
     First Preferred Embodiment 
       FIGS. 1 through 6  show a first preferred embodiment of the present invention. 
     An overall construction of the watercraft will be described first. As shown in  FIG. 1 , a watercraft in accordance with the first preferred embodiment preferably has two outboard motors  12  as examples of watercraft propulsion units mounted on a stern board  11  of a hull  10 . The outboard motors  12  can be turned around swivel shafts  14  provided along the vertical direction. 
     A steering bracket  15  is fixed to an upper end of the swivel shaft  14 . A rudder deflecting system  16  is coupled to a front end  15   a  of the steering bracket  15 . The rudder deflecting system  16  is moved by operation of a steering wheel  17  disposed in a cockpit. 
     As shown in  FIG. 2 , the rudder deflecting system  16  has an electric motor  20 , for example, of a DD (Direct Drive) type. The electric motor  20  is placed on a threaded rod  21  arranged in the right-and-left direction, and moves to right or left along the threaded rod  21 . 
     Both ends of the threaded rod  21  are supported by a pair of right and left supporting members  22 . The supporting members  22  are supported by a tilt shaft  23 . 
     A coupling bracket  24  is arranged to protrude rearward from the electric motor  20 . The coupling bracket  24  and the steering bracket  15  are coupled together via a coupling pin  25 . 
     Accordingly, as the electric motor  20  drives it moves to right or left along the threaded rod  21 . Thereby, the outboard motor  12  rotates around the swivel shaft  14  via the coupling bracket  24  and the steering bracket  15 . 
     On the other hand, as shown in  FIG. 1 , the steering wheel  17  is fixed to a steering wheel shaft  26 . A steering wheel control unit  27  is provided at a base end of the steering wheel  26 . The steering wheel control unit  27  has a steering wheel angle sensor  28  for detecting a steering angle of the steering wheel  17 , and a reaction motor  29  for applying a desired reaction force to the steering wheel  17  when the steering wheel  17  is operated. 
     The steering wheel control unit  27  is connected to an ECU (Electronic Control Unit)  33  via a signal cable  30 . The ECU  33  is connected to the electric motors  20  of the rudder deflecting systems  16 . A signal from the steering wheel angle sensor  28  is input to the ECU  33 . The ECU  33  controls and operates the electric motors  20 . The ECU  33  also controls the reaction motor  29 . A position where the ECU  33  is located is not limited to the position shown in  FIG. 1 , but the ECU  33  may be located in the outboard motor  12 , in a remote controller (not shown) of the watercraft, or the like. 
     Meanwhile, as shown in  FIG. 3 , the outboard motor  12  has an engine  13  in an upper portion thereof. Output of the engine  13  is transmitted to the propeller shaft  37  to which a propeller  36  is fixed via a drive shaft  34  and the shift device  35 . 
     As shown in  FIG. 4 , a generator  42  is provided for each of the engines  13  of the two outboard motors  12 . Two main batteries  43  are connected to the generators  42  and the electric motors  20  of the rudder deflecting systems  16 . 
     Further, a sub-battery (for example, a battery for accessory devices)  44  is connected to the generators  42  and the main batteries  43  corresponding to the respective outboard motors  12 . 
     The rudder deflecting system  16  of one of the outboard motors  12  can be supplied with electric power from the generator  42  of the other outboard motor  12  via a connection wiring H between the batteries  44  and the like. 
     The electric motors  20  of the rudder deflecting devices  16  are operated with electric power from the generators  42 , the main batteries  43 , and the like, and thereby the outboard motors  12  are steered. 
     Next, an operation of the first preferred embodiment will be described. 
     When the steering wheel  17  is rotated in order to steer the hull  10  while the watercraft is traveling, a rotational amount is detected by the steering wheel angle sensor  28 , and sent to the ECU  33 . The electric motors  20  of the rudder deflecting systems  16  are operated by prescribed amounts in accordance with a signal from the ECU  33 . The two outboard motors  12  are turned around the swivel shafts  14  by the prescribed amount in prescribed directions via the steering brackets  15  and the like. 
     For example, as shown in  FIG. 5 , a steering load to one of the outboard motors  12  (the outboard motor  12  on the starboard side in this case) becomes larger than a steering load to the other outboard motor  12  (the outboard motor  12  on the port side in this case) when the two outboard motors  12  are turned and the hull  10  is turned to the right. 
     As a result of the example shown in  FIG. 6A , the consumption of electric power of the outboard motor  12  on the starboard side is larger than the amount of electric power generated by the generator  42  on the starboard side. The consumption of electric power of the outboard motor  12  on the port side is smaller than the amount of electric power generated by the generator  42  on the port side. The amount of electric power generated by the generator  42  on the starboard side is generally equal to the amount of electric power generated by the generator  42  on the port side. Therefore, a portion (a) of the amount of electric power generated by the generator  42  on the port side is distributed to be added to the amount of electric power generated by the generator  42  on the starboard side via the connection wiring H. 
     Thereby, the consumption of electric power becomes equal to the amount of generated electric power on the starboard side. Accordingly, discharge “b” as shown by a broken line in  FIG. 6B  is prevented, and an insufficient charge to the main battery  43  and an insufficient output of the rudder deflecting system  16  are prevented. In the case where the watercraft turns left and the consumption of electric power becomes larger than the generated electric power in the outboard motor  12  on the port side, the amount of electric power generated by the generator  42  on the starboard side is distributed to be added to the amount of electric power generated by the generator  42  on the port side. 
     Thereby, electric power for operating the rudder deflecting systems  16  can be stably supplied without increasing a size of the generator  42  in the case that a plurality of outboard motors  12  are provided. 
     Second Preferred Embodiment 
       FIG. 7  shows a second preferred embodiment of the present invention. 
     In the second preferred embodiment, diodes D preferably are disposed about midway in the connection wiring H by which the main batteries  43  and the sub-battery  44  are connected to the rudder deflecting systems  16 . Thereby, the diodes D intercept electric current running from the rudder deflecting systems  16  toward the main batteries  43  and the sub-battery  44 . 
     In other words, the main battery  43  arranged to start the engine of the outboard motor  12  is connected to each of the plurality of the outboard motors  12 . The main battery  43  is connected to the rudder deflecting system  16  of the outboard motor  12  while being capable of supplying electric power to the rudder deflecting system  16 , and this main battery  43  does not supply electric power to the rudder deflecting system  16  of the other outboard motor  12 . 
     Accordingly, the main batteries  43  are independent of each other, but electric power may be supplied from the generator  42  of one of the outboard motors  12  to the rudder deflecting system  16  of the other outboard motor  12 . 
     A reduction in the amount of electric power for charging the main battery  43  arranged to start the engine can be prevented by making the main battery  43  of one of the outboard motors  12  independent of the other outboard motor  12  as described above. 
     Other constructions and actions are similar to the first preferred embodiment, and descriptions thereof are omitted. 
     Third Preferred Embodiment 
       FIG. 8  shows a third preferred embodiment of the present invention. 
     Comparing the third preferred embodiment with the second preferred embodiment, in the second preferred embodiment the sub-battery  44  preferably is directly connected to the rudder deflecting systems  16  via the diodes D. However, in the third preferred embodiment the sub-battery  44  preferably is connected to the positions between the diodes D and the main batteries  43  via other diodes D. 
     Thereby, electric power is supplied from the generator  42  of an arbitrary outboard motor  12  to the main battery  43  and the rudder deflecting system  16  of the outboard motor  12 . Further, electric power is supplied from the generator  42  of the arbitrary outboard motor  12  to the main battery  43  and the rudder deflecting system  16  of the other outboard motor  12 . 
     Electric power is supplied also from the sub-battery  44  to the rudder deflecting system  16  and the main battery  43  of each of the outboard motors  12 . 
     In such a construction, the main battery  43  is charged by electric power supplied from the generator  42  of the other outboard motor  12  via the diode D, and both the main batteries  43  are charged by electric power supplied from the sub-battery  44  via the respective diodes D. No electric power is supplied from the main battery  43  to the other outboard motor  12 , and the amount of electric power for charging the main battery  43  can be secured. 
     Other constructions and actions are similar to the second preferred embodiment, and descriptions thereof are omitted. 
     Fourth Preferred Embodiment 
       FIG. 9  shows a fourth preferred embodiment of the present invention. 
     Comparing the fourth preferred embodiment with the third preferred embodiment, a single generator  42  preferably is provided for each outboard motor  12  in the third preferred embodiment. However, in the fourth preferred embodiment, two generators  42  preferably are provided for each outboard motor  12 . One of the generators  42  is connected to a single main battery  43 , and the other generator  42  is connected to the sub-battery  44 . 
     Thereby, one of the generators  42  provided for an arbitrary outboard motor  12  is used for charging the main battery  43  of this outboard motor  12  and for supplying electric power to the rudder deflecting system  16  of this outboard motor  12 , and is not used for supplying electric power to the rudder deflecting system  16  of the other outboard motor  12 . Therefore, the amount of electric power for charging the main batteries  43  can be secured. 
     The other generator  42  supplies electric power to the rudder deflecting system  16  of the other outboard motor  12 . The other generator  42  also charges the main battery  43  of the other outboard motor  12 . 
     Other constructions and actions are similar to the third preferred embodiment, and descriptions will not be made. 
     In each of the above preferred embodiments, a watercraft is provided with two outboard motors. However, the present invention maybe applied to a watercraft with three, four, or more outboard motors. In such a case, combinations of generators, rudder deflecting systems, main batteries, and the like may be simply added. An outboard motor is an example of a watercraft propulsion unit in each of the above preferred embodiments. However, the present invention can be applied to inboard/outboard motors. 
     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 the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.