Abstract:
Provided is a ship maneuvering device that can increase operation sensitivity and enables smooth operation when simultaneously operating the rotation component determination unit and the oblique sailing component determination unit of an operation means. In the ship maneuvering device  1 , a control device  31  computes a rotation component propulsion vector Trot for rotation and an oblique sailing component propulsion vector T trans  for oblique sailing for left and right out-drive units  10 A,  10 B from the amount of operation of a joystick  21 , calculates the combined torque T by combining the rotation component propulsion vector T rot  and the oblique sailing component propulsion vector T trans  for each of the left and right out-drive units  10 A,  10 B, and computes the propulsion and orientation for each of the left and right out-drive units  10 A,  10 B.

Description:
TECHNICAL FIELD 
     The present invention relates to an art of a ship maneuvering device. 
     BACKGROUND ART 
     Conventionally, a ship is known having an inboard motor (inboard engine, outboard drive) in which a pair of left and right engines are arranged inside a hull and power is transmitted to a pair of left and right outdrive devices arranged outside the hull. The outdrive devices are propulsion devices rotating screw propellers so as to propel the hull, and are rudder devices rotated concerning a traveling direction of the hull so as to make the hull turn. 
     Such outdrive devices are rotated with hydraulic steering actuators provided in the outdrive devices (for example, see the Patent Literature 1). Then, a rotation angle of each of the outdrive devices, that is, a steering angle is grasped based on detection results of an angle detection sensor and the like provided in a linkage mechanism constituting the outdrive device. 
     The ship has an operation means setting a traveling direction of the ship. The ship is controlled with a control device so as to travel to the direction set with the operation means. 
     PRIOR ART REFERENCE 
     Patent Literature 
     Patent Literature 1: the Japanese Patent Laid Open Gazette Hei. 1-285486 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     The operation means has an oblique sailing component determination unit and a turning component determination unit. Conventionally, when the oblique sailing component determination unit and the turning component determination unit are operated simultaneously, priority is not set and action of the hull is unnatural, whereby smooth maneuvering cannot be performed. 
     In consideration of the above problems, the purpose of the present invention is to provide a ship maneuvering device that can increase operation sensitivity and enables smooth operation when simultaneously operating the oblique sailing component determination unit and the turning component determination unit of an operation means. 
     Means for Solving the Problems 
     The problems to be solved by the present invention have been described above, and subsequently, the means of solving the problems will be described below. 
     According to the present invention, a ship maneuvering device includes a pair of left and right engines, rotation speed changing actuators independently changing engine rotation speeds of the pair of left and right engines, a pair of left and right outdrive devices respectively connected to the pair of left and right engines and rotating screw propellers so as to propel a hull, forward/reverse switching clutches disposed between the engines and the screw propellers, a pair of left and right steering actuators respectively independently rotating the pair of left and right outdrive devices laterally within a predetermined angle range, an operation means setting a traveling direction of a ship, an operation amount detection means detecting the operation amount of the operation means, and a control device controlling the rotation speed changing actuators, the forward/reverse switching clutches, and the steering actuators so as to travel to a direction set by the operation means. The control device calculates oblique sailing component propulsion power vectors for oblique sailing of the left and right outdrive devices and turning component propulsion power vectors for the turning from the operation amount of the operation means, and composes the oblique sailing component propulsion power vectors and the turning component propulsion power vectors of the left and right outdrive devices so as to calculates composition vectors, thereby calculating propulsion powers and directions of the left and right outdrive devices. 
     According to the present invention, when directions of the composition vector is within a range over a predetermined angle range of the outdrive device, the outdrive device is controlled so as to be made a predetermined limiting angle mode and the engine rotation speed is reduced to a set rotation speed. 
     According to the present invention, when the direction of the composition vector is within a range over a predetermined angle range of the outdrive device, a rotation angle of the outdrive device is fixed at a state of a predetermined limiting angle. 
     According to the present invention, when a direction of the composition vector is within a range over a predetermined angle range of the outdrive device, the engine rotation speed of the engine is reduced following reduction of a minor angle between the direction of the composition vector and a lateral direction of the hull. 
     Effect of the Invention 
     The present invention brings the following effects. 
     According to the present invention, in comparison with the case of calculating the propulsion powers and the directions of the left and right outdrive devices based on only the oblique sailing component propulsion power vectors and subsequently calculating the propulsion powers and the directions of the left and right outdrive devices based on only the turning component propulsion power vectors, by calculating the composition vectors based on the oblique sailing component propulsion power vectors and the turning component propulsion power vectors, smooth operation is obtained and operability is improved. Since the oblique sailing component propulsion power and the turning component propulsion power can be controlled independently, the components do not interfere with each other, whereby a turning moment generated at the time of the turning operation has always the same characteristics regardless of the input of the oblique sailing operation. Accordingly, in the ship having this control, accuracy of correction of the turning direction is improved. 
     According to the present invention, even if the direction of the composition vector is over the predetermined angle range of the outdrive device, the steering of the outdrive device can be corrected. 
     According to the present invention, when the direction of the composition vector is over the predetermined angle range of the outdrive devices, frequent change of the rotation angle and frequent switching of forward/reverse rotation of the outdrive device is prevented. 
     According to the present invention, when the direction of the composition vector is over the predetermined angle range of the outdrive devices, the switching of forward/reverse rotation of the outdrive devices can be performed smoothly. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       [ FIG. 1 ]  FIG. 1  is a drawing of a ship according to an embodiment of the present invention. 
       [ FIG. 2 ]  FIG. 2  is a left side view partially in section of an outdrive device according to the embodiment of the present invention. 
       [ FIG. 3 ]  FIG. 3  is a right side view partially in section of the outdrive device according to the embodiment of the present invention. 
       [ FIG. 4 ]  FIG. 4  is a drawing of an operation device. 
       [ FIG. 5 ]  FIG. 5  is a block diagram of a control device. 
       [ FIG. 6 ]  FIG. 6  is a flow chart of a calculation method of propulsion powers and directions of left and right outdrive devices. 
       [ FIG. 7 ]  FIG. 7(A)  is a drawing of oblique sailing component propulsion power vectors of the outdrive devices.  FIG. 7(B)  is a drawing of turning component propulsion power vectors of the outdrive devices.  FIG. 7(C)  is a drawing of composition vectors of the outdrive devices. 
       [ FIG. 8 ]  FIG. 8  is a plan view of a rotation angle of the outdrive device. 
       [ FIG. 9 ]  FIG. 9  is a graph of relation of the angle of the composition vector and the rotation angle of the outdrive device. 
       [ FIG. 10 ]  FIG. 10  is a plan view of the rotation angle of the outdrive device. 
       [ FIG. 11 ]  FIG. 11  is a graph of relation of the rotation angle of the outdrive device and a reduction rate of an engine rotation speed. 
     
    
    
     DESCRIPTION OF NOTATIONS 
       1  ship maneuvering device 
       2  hull 
       3 A and  3 B engines 
       4 A and  4 B rotation speed changing actuators 
       10 A and  10 B outdrive devices 
       15 A and  15 B screw propellers 
       16 A and  16 B forward/reverse switching clutches 
       17 A and  17 B hydraulic steering actuators 
       21  joystick (operation means) 
       31  control device 
       39  operation amount detection sensor (operation amount detection means) 
     T Atrans  and T Btrans  oblique sailing component propulsion power vectors 
     T Arot  and T Brot  turning component propulsion power vectors 
     T A  and T B  composition vectors 
     β angles of composition vectors 
     θ A  and θ B  rotation angles of outdrive devices 
     DETAILED DESCRIPTION OF THE INVENTION 
     Firstly, an explanation will be given on a ship maneuvering device according to an embodiment of the present invention. 
     As shown in  FIGS. 1 ,  2  and  3 , a ship maneuvering device  1  has a pair of left and right engines  3 A and  3 B, rotation speed changing actuators  4 A and  4 B independently changing engine rotation speeds N A  and N B  of the pair of left and right engines  3 A and  3 B, a pair of left and right outdrive devices  10 A and  10 B respectively connected to the pair of left and right engines  3 A and  3 B and rotating screw propellers  15 A and  15 B so as to propel a hull  2 , forward/reverse switching clutches  16 A and  16 B disposed between the engines  3 A and  3 B and the screw propellers  15 A and  15 B, a pair of left and right hydraulic steering actuators  17 A and  17 B respectively independently rotating the pair of left and right outdrive devices  10 A and  10 B laterally, electromagnetic valves  17 Aa and  17 Ba controlling hydraulic pressure in the hydraulic steering actuators  17 A and  17 B, a joystick  21 , accelerator levers  22 A and  22 B and an operation wheel  23  as operation means setting a traveling direction of the ship, an operation amount detection sensor  39  (see  FIG. 5 ) as an operation amount detection means detecting an operation amount of the joystick  21 , operation amount detection sensor  43 A and  43 B (see  FIG. 5 ) as operation amount detection means detecting operation amounts of the accelerator levers  22 A and  22 B, an operation amount detection sensor  44  (see  FIG. 5 ) as an operation amount detection means detecting an operation amount of the operation wheel  23 , and a control device  31  (see  FIG. 5 ) controlling the rotation speed changing actuators  4 A and  4 B, the forward/reverse switching clutches  16 A and  16 B, the hydraulic steering actuators  17 A and  17 B and the electromagnetic valves  17 Aa and  17 Ba so as to travel to a direction set by the joystick  21 , the accelerator levers  22 A and  22 B and the operation wheel  23 . 
     The engines  3 A and  3 B are arranged in a rear portion of the hull  2  as a pair laterally, and are connected to the outdrive devices  10 A and  10 B arranged outside the ship. The engines  3 A and  3 B have output shafts  41 A and  41 B for outputting rotation power. 
     The rotation speed changing actuators  4 A and  4 B are means controlling the engine rotation power, and changes a fuel injection amount of a fuel injection device and the like so as to control engine rotation speeds of the engines  3 A and  3 B. 
     The outdrive devices  10 A and  10 B are propulsion devices rotating the screw propellers  15 A and  15 B so as to propel the hull  2 , and are provided outside the rear portion of the hull  2  as a pair laterally. The pair of left and right outdrive devices  10 A and  10 B are respectively connected to the pair of left and right engines  3 A and  3 B. The outdrive devices  10 A and  10 B are rudder devices which are rotated concerning the traveling direction of the hull  2  so as to make the hull  2  turn. The outdrive devices  10 A and  10 B mainly include input shafts  11 A and  11 B, the forward/reverse switching clutches  16 A and  16 B, drive shafts  13 A and  13 B, final output shaft  14 A and  14 B, and the rotating screw propellers  15 A and  15 B. 
     The input shafts  11 A and  11 B transmit rotation power. In detail, the input shafts  11 A and  11 B transmit rotation power of the engines  3 A and  3 B, transmitted from the output shafts  41 A and  41 B of the engines  3 A and  3 B via universal joints  5 A and  5 B, to the forward/reverse switching clutches  16 A and  16 B. One of ends of each of the input shafts  11 A and  11 B is connected to corresponding one of the universal joints  5 A and  5 B attached to the output shafts  41 A and  41 B of the engines  3 A and  3 B, and the other end thereof is connected to corresponding one of the forward/reverse switching clutches  16 A and  16 B. 
     The forward/reverse switching clutches  16 A and  16 B are arranged between the engines  3 A and  3 B and the rotating screw propellers  15 A and  15 B, and switch rotation direction of the rotation power. In detail, the forward/reverse switching clutches  16 A and  16 B are rotation direction switching devices which switch the rotation power of the engines  3 A and  3 B, transmitted via the input shafts  11 A and  11 B and the like, to forward or reverse direction. The forward/reverse switching clutches  16 A and  16 B have forward bevel gears and reverse bevel gears which are connected to inner drums having disc plates, and pressure plates of outer drums connected to the input shafts  11 A and  11 B is pressed against the disc plates of the forward bevel gears or the reverse bevel gears so as to switch the rotation direction. 
     The drive shafts  13 A and  13 B transmit the rotation power. In detail, the drive shafts  13 A and  13 B are rotation shafts which transmit the rotation power of the engines  3 A and  3 B, transmitted via the forward/reverse switching clutches  16 A and  16 B and the like, to the final output shaft  14 A and  14 B. A bevel gear provided at one of ends of each of the drive shafts  13 A and  13 B is meshed with the forward bevel gear and the reverse bevel gear provided on corresponding one of the forward/reverse switching clutches  16 A and  16 B, and a bevel gear provided at the other end is meshed with a bevel gear provided on corresponding one of the final output shaft  14 A and  14 B. 
     The final output shaft  14 A and  14 B transmit the rotation power. In detail, the final output shaft  14 A and  14 B are rotation shafts which transmit the rotation power of the engines  3 A and  3 B, transmitted via the drive shafts  13 A and  13 B and the like, to the screw propellers  15 A and  15 B. As mentioned above, the bevel gear provided at one of ends of each of the final output shaft  14 A and  14 B is meshed with the bevel gear of corresponding one of the drive shafts  13 A and  13 B, and the other end is attached thereto with corresponding one of the screw propellers  15 A and  15 B. 
     The screw propellers  15 A and  15 B are rotated so as to generate propulsion power. In detail, the screw propellers  15 A and  15 B are driven by the rotation power of the engines  3 A and  3 B transmitted via the final output shaft  14 A and  14 B and the like so that a plurality of blades arranged around the rotation shafts paddle surrounding water, whereby the propulsion power is generated. 
     The hydraulic steering actuators  17 A and  17 B are hydraulic devices which drive steering arms  18 A and  18 B so as to rotate the outdrive devices  10 A and  10 B. The hydraulic steering actuators  17 A and  17 B are provided therein with the electromagnetic valves  17 Aa and  17 Ba for controlling hydraulic pressure, and the electromagnetic valves  17 Aa and  17 Ba are connected to the control device  31 . 
     The hydraulic steering actuators  17 A and  17 B are so-called single rod type hydraulic actuators. However, the hydraulic steering actuators  17 A and  17 B may alternatively be double rod type. 
     The joystick  21  as the operation means is a device determining the traveling direction of the ship, and is provided near an operator&#39;s seat of the hull  2 . A plane operation surface of the joystick  21  is an oblique sailing component determination part  21   a , and a torsion operation surface thereof is a turning component determination part  21   b.    
     The joystick  21  can be moved free within the operation surface parallel to an X-Y plane shown in  FIG. 4 , and a center of the operation surface is used as a neutral starting point. Longitudinal and lateral directions in the operation surface correspond to the traveling direction, and an inclination amount of the joystick  21  corresponds to a target hull speed. The target hull speed is increased corresponding to increase of the inclination amount of the joystick  21 . 
     The torsion operation surface is provided with the joystick  21 , and by twisting the joystick  21  concerning a Z axis extended substantially perpendicularly to the plane operation surface as a turning axis, a turning speed can be changed. A torsion amount of the joystick  21  corresponds to a target turning speed. A maximum target lateral turning speed is set at fixed turning angle positions of the joystick  21 . 
     The accelerator levers  22 A and  22 B as the operation means are devices determining the target hull speed of the ship, and are provided near the operator&#39;s seat of the hull  2 . The two accelerator levers  22 A and  22 B are provided so as to correspond respectively to the left and right engines  3 A and  3 B. The rotation speed of the engine  3 A is changed by operating the accelerator lever  22 A, and the rotation speed of the engine  3 B is changed by operating the accelerator lever  22 B. 
     The operation wheel  23  as the operation means is a device determining the traveling direction of the ship, and is provided near the operator&#39;s seat of the hull  2 . The traveling direction is changed widely following increase of a rotation amount of the operation wheel  23 . 
     A correction control start switch  42  (see  FIG. 5 ) is a switch for starting correction control of turning action of the hull  2 . 
     The correction control start switch  42  is provided near the joystick  21  and is connected to the control device  31 . 
     Next, an explanation will be given on various kinds of detection means referring to  FIG. 5 . 
     Rotation speed detection sensors  35 A and  35 B as rotation speed detection means are means for detecting engine rotation speeds N A  and N B  of the engines  3 A and  3 B and are provided in the engines  3 A and  3 B. 
     An elevation angle sensor  36  as an elevation angle detection means is a means for detecting an elevation angle a of the hull  2 . The elevation angle indicates inclination of the hull in the water concerning a flow. 
     A hull speed sensor  37  as a hull speed detection means is a means for detecting a hull speed V, and is an electromagnetic log, a Doppler sonar or a GPS for example. 
     Lateral rotation angle detection sensors  38 A and  38 B as lateral rotation angle detection means are means for detecting lateral rotation angles θ A  and θ B  of the outdrive devices  10 A and  10 B. The lateral rotation angle detection sensors  38 A and  38 B are provided near the hydraulic steering actuators  17 A and  17 B, and detect the lateral rotation angles θ A  and θ B  of the outdrive devices  10 A and  10 B based on the drive amounts of the hydraulic steering actuators  17 A and  17 B. 
     The operation amount detection sensor  39  as the operation amount detection means is a sensor for detecting the operation amount in the plane operation surface and the operation amount in the torsion operation surface of the joystick  21 . The operation amount detection sensor  39  detects an inclination angle and an inclination direction of the joystick  21 . The operation amount detection sensor  39  detects the torsion amount of the joystick  21 . 
     The operation amount detection sensors  43 A and  43 B as the operation amount detection means are sensors for detecting the operation amounts of the accelerator levers  22 A and  22 B. The operation amount detection sensors  43 A and  43 B detect inclination angles of the accelerator levers  22 A and  22 B. 
     The operation amount detection sensor  44  as the operation amount detection means is a sensor for detecting the operation amount of the operation wheel  23 . The operation amount detection sensor  44  detects the rotation amount of the operation wheel  23 . 
     Outdrive device rotation speed detection sensors  40 A and  40 B as rotation speed detection means of the outdrive devices  10 A and  10 B are sensors for detecting rotation speeds of the screw propellers  15 A and  15 B of the outdrive devices  10 A and  10 B, and are provided at middle portions of the final output shaft  14 A and  14 B. The outdrive device rotation speed detection sensors  40 A and  40 B detect outdrive device rotation speeds ND A  and ND B . 
     The control device  31  controls the rotation speed changing actuators  4 A and  4 B, the forward/reverse switching clutches  16 A and  16 B and the hydraulic steering actuators  17 A and  17 B so that the ship travels to the direction set by the joystick  21 . The control device  31  is connected respectively to the rotation speed changing actuators  4 A and  4 B, the forward/reverse switching clutches  16 A and  16 B, the hydraulic steering actuators  17 A and  17 B, the electromagnetic valves  17 Aa and  17 Ba, the joystick  21 , the accelerator levers  22 A and  22 B, the operation wheel  23 , the rotation speed detection sensors  35 A and  35 B, the elevation angle sensor  36 , the hull speed sensor  37 , the lateral rotation angle detection sensors  38 A and  38 B, the operation amount detection sensor  39 , the operation amount detection sensors  43 A and  43 B, the operation amount detection sensor  44 , and the outdrive device rotation speed detection sensors  40 A and  40 B. The control device  31  includes a calculation means  32  having a CPU (central processing unit) and a storage means  33  such as a ROM, a RAM or a HDD. 
     Next, an explanation will be given on a method for calculating the propulsion powers and directions of the left and right outdrive devices  10 A and  10 B with the control device  31  referring to  FIG. 6 . 
     Firstly, an operation amount of the joystick  21  is detected (step S 10 ), and based on the operation amount of the joystick  21 , oblique sailing component propulsion power vectors T Atrans  and T Btrans  for the oblique sailing and turning component propulsion power vectors T Arot  and T Brot  for the turning of the left and right outdrive devices  10 A and  10 B are calculated respectively (step S 20 ). 
     The operation amount of the joystick  21  is the inclination angle, the inclination direction and a torsion amount of the joystick  21 , and detected with the operation amount detection sensor  39 . Then, based on the operation amounts, the control device  31  calculates the oblique sailing component propulsion power vectors T Atrans  and T Btrans  for the oblique sailing and the turning component propulsion power vectors T Arot  and T Brot  for the turning of the left and right outdrive devices  10 A and  10 B. The oblique sailing component propulsion power vectors T Atrans  and T Btrans  of the left and right outdrive devices  10 A and  10 B are calculated as shown in  FIG. 7(A) . The turning component propulsion power vectors T Arot  and T Brot  of the left and right outdrive devices  10 A and  10 B are calculated as shown in  FIG. 7(B) . 
     Next, the oblique sailing component propulsion power vectors T Atrans  and T Btrans  and the turning component propulsion power vectors T Arot  and T Brot  of the left and right outdrive devices  10 A and  10 B are composed respectively so as to calculate the propulsion powers and the directions of the left and right outdrive devices  10 A and  10 B (step S 30 ). 
     As shown in  FIG. 7(C) , vectors T A  and T B  are calculated by composing the oblique sailing component propulsion power vectors T Atrans  and T Btrans  and the turning component propulsion power vectors T Arot  and T Brot  of the left and right outdrive devices  10 A and  10 B calculated at the step S 20 . 
     Next, based on norms of the composited vectors T A  and T B , the control device  31  calculates a rotation speed N of each of the left and right engines  3 A and  3 B (step S 40 ), the forward/reverse switching clutches  16 A and  16 B are switched, and the left and right engines  3 A and  3 B are driven. Based on the directions of the composited vectors T A  and T B , the lateral rotation angles θ A  and θ B  of the outdrive devices  10 A and  10 B are calculated respectively (step S 50 ), and the hydraulic steering actuators  17 A and  17 B are driven. 
     Next, an explanation will be given on a process of restriction of the lateral rotation angles of the pair of left and right outdrive devices  10 A and  10 B at the calculation of the rotation angles θ A  and θ B  at the step S 50 . Since the same process is performed concerning the pair of left and right outdrive devices  10 A and  10 B, the process of restriction of the lateral rotation angle of the one outdrive device  10 A is described. 
     When the angle (direction) β of the composition vectors T A  is over a predetermined angle range of the outdrive device  10 A at the step S 50  in the flow chart, the outdrive device  10 A is controlled so as to be at a predetermined limiting angle mode. 
     Herein, the predetermined angle range is a range shown with slashes in  FIG. 8 , and is an angle range in which the outdrive device  10 A can be rotated. Since the hydraulic steering actuator  17 A is constructed by a hydraulic cylinder and its rotation range is limited, the predetermined angle range is provided. When the predetermined angle range is referred to as θ 1 , a limiting angle is referred to as α, and the rear side is regarded as 0°, the relation thereof is −α&lt;θ 1 ≦α. Since the rotation of the engine  3 A can be switched between forward and reverse rotations with the forward/reverse switching clutch  16 A, centering on the front side, in other words,) 180° (−180°), the lateral angle is −180°&lt;θ 1 ≦180°−(−α), 180°−α&lt;θ 1 ≦180°. For example, when α is 30°, the predetermined angle range is −180°&lt;θ 1 ≦−150°, −30°&lt;θ 1 ≦30°, 150°&lt;θ 1 ≦180°. 
     Next, an explanation will be given on the limiting angle mode. 
     In the limiting angle mode, for obtaining smooth action following the operation of the joystick  21 , the driving is performed with reduced propulsion power. Namely, the engine rotation speed N A  is reduced to a set rotation speed N set . In the limiting angle mode, the rotation angle θ A  of the outdrive device  10 A is fixed at a state of a predetermined limiting angle. Concretely, by the angle (direction) β of the composition vectors T A  determined with the control device  31 , the lateral rotation angle θ A  of the outdrive device  10 A is determined. As shown in  FIG. 9 , in the case in which an X axis indicates the angle β of the composition vector T A  and a Y axis indicates the lateral rotation angle θ A  of the outdrive device  10 A, when the angle β of the composition vector T A  is within a range of −180°−(−α)&lt;β≦−90°, the lateral rotation angle θ A  of the outdrive device  10 A is −180°−(−α). When the angle β of the composition vector T A  is within a range of −90°&lt;β≦−α, the lateral rotation angle θ A  of the outdrive device  10 A is (−α). When the angle β of the composition vector T A  is within a range of α&lt;β≦90°, the lateral rotation angle θ A  of the outdrive device  10 A is α. When the angle β of the composition vector T A  is within a range of 90°&lt;β≦180°−α, the lateral rotation angle θ A  of the outdrive device  10 A is 180°−α. 
     As shown in  FIG. 9 , in the limiting angle mode, a play tolerance (hysteresis) is set so as to prevent frequent change of the rotation angle θ A  of the outdrive device  10 A. 
     In the case in which the angle β of the composition vector T A  is within a range of −180°−(−α)&lt;β≦−90°, when the angle β of the composition vector T A  is larger than −90°+γ, the rotation angle θ A  of the outdrive device  10 A is (−α). In the case in which the angle β of the composition vector T A  is within a range of −90°&lt;β≦−α, when the angle β of the composition vector T A  is not more than −90°−γ, the rotation angle θ A  of the outdrive device  10 A is −180°−(−α). 
     In the case in which the angle β of the composition vector T A  is within a range of α&lt;β≦90°, when the angle β of the composition vector T A  is larger than 90°+γ, the rotation angle θ A  of the outdrive device  10 A is 180°−α. In the case in which the angle β of the composition vector T A  is within a range of 90°&lt;β≦180°−α, when the direction of the composition vector T A  is not more than 90°−γ, the rotation angle θ A  of the outdrive device  10 A is α. 
     In the limiting angle mode, the engine rotation speed N A  of the engine  3 A may alternatively be reduced following reduction of a minor angle between the direction of the composition vector T A  and the lateral direction of the hull  2 . Following the reduction of the angle between the direction of the composition vector T A  and the lateral direction of the hull (90° and −90°), that is, following approach of the angle β of the composition vector T A  to 90° or −90°, the engine rotation speed N A  of the engine  3 A is reduced. 
     As shown in  FIGS. 10 and 11 , in the limiting angle mode, by increasing a rotation reduction rate of the engine  3 A, the engine rotation speed N A  is reduced. 
     An area shown with slashes in  FIG. 10  is a rotation speed reduction area in which the engine rotation speed N A  is reduced gradually, and a colored area is a reduction rate 100% area in which the reduction rate of the engine rotation speed N A  is 100%. 
     Concretely, as shown in  FIG. 11 , within a range larger than −180°−(−α) and not more than Φ 1 , the reduction rate is increased following the increase of the angle β of the composition vector T A , and at Φ 1 , the reduction rate is 100%, that is, the engine rotation speed N A  is a low idling rotation speed. 
     When the angle β of the composition vector T A  is larger than Φ 1  and not more than Φ 2 , the reduction rate is maintained at 100%. 
     When the angle β of the composition vector T A  is larger than Φ 2  and not more than −α, the reduction rate is reduced following the increase of the angle β. At −α, the reduction rate is 0%, that is, the engine rotation speed N A  is the engine rotation speed calculated at the step S 40 . 
     Herein, Φ 1  and Φ 2  are angles are linearly symmetrical with −90°. For example, when Φ 1  is −100°, Φ 2  is −80°. 
     When the angle β of the composition vector T A  is larger than α and not more than Φ 3 , the reduction rate is increased following the increase of the angle β. At Φ 3 , the reduction rate is 100%, that is, the engine rotation speed N A  is the low idling rotation speed. 
     When the angle β of the composition vector T A  is larger than Φ 3  and not more than Φ 4 , the reduction rate is maintained at 100%. 
     When the angle β of the composition vector T A  is larger than Φ 4  and not more than 180°−α, the reduction rate is reduced following the increase of the angle β. At 180°−α, the reduction rate is 0%, that is, the engine rotation speed N A  is the engine rotation speed calculated at the step S 40 . 
     Herein, Φ 3  and Φ 4  are angles are linearly symmetrical with 90°. For example, when Φ 3  is 80°, Φ 4  is 100°. 
     Φ 1 , Φ 2 , Φ 3  and Φ 4  can be changed within the ranges of −180°−(−α)≦Φ 1 &lt;−90°, −90°≦Φ 2 &lt;−α, α≦Φ 3 &lt;90°, and 90°≦Φ 4 &lt;180°−α. 
     As mentioned above, the ship maneuvering device  1  has the pair of left and right engines  3 A and  3 B, the rotation speed changing actuators  4 A and  4 B independently changing engine rotation speeds N of the pair of left and right engines  3 A and  3 B, the pair of left and right outdrive devices  10 A and  10 B respectively connected to the pair of left and right engines  3 A and  3 B and rotating the screw propellers  15 A and  15 B so as to propel the hull  2 , the forward/reverse switching clutches  16 A and  16 B disposed between the engines  3 A and  3 B and the screw propellers  15 A and  15 B, the pair of left and right hydraulic steering actuators  17 A and  17 B respectively independently rotating the pair of left and right outdrive devices  10 A and  10 B laterally, the joystick  21  setting the traveling direction of the ship, the operation amount detection sensor  39  detecting the operation amount of the joystick  21 , and the control device  31  controlling the rotation speed changing actuators  4 A and  4 B, the forward/reverse switching clutches  16 A and  16 B, and the hydraulic steering actuators  17 A and  17 B so as to travel to a direction set by the joystick  21 . From the operation amount of the joystick  21 , the control device  31  calculates the oblique sailing component propulsion power vectors T Atrans  and T Btrans  for the oblique sailing of the left and right outdrive devices  10 A and  10 B and the turning component propulsion power vectors T Arot  and T Brot  for the turning, and composes the oblique sailing component propulsion power vectors T Atrans  and T Btrans  and the turning component propulsion power vectors T Arot  and T Brot  of the left and right outdrive devices  10 A and  10 B so as to calculates the composition vectors T A  and T B , thereby calculating the propulsion powers and the directions of the left and right outdrive devices  10 A and  10 B. 
     According to the construction, in comparison with the case of calculating the propulsion powers and the directions of the left and right outdrive devices  10 A and  10 B based on only the oblique sailing component propulsion power vectors T Atrans  and T Btrans  and subsequently calculating the propulsion powers and the directions of the left and right outdrive devices  10 A and  10 B based on only the turning component propulsion power vectors T Arot  and T Brot , by calculating the composition vectors T A  and T B  based on the oblique sailing component propulsion power vectors T Atrans  and T Btrans  and the turning component propulsion power vectors T Arot  and T Brot , the final propulsion powers and the final directions can be calculated, whereby smooth operation is obtained without setting priority and operability is improved. 
     When the angle β of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive devices  10 A and  10 B, the outdrive devices  10 A and  10 B are controlled so as to be made the predetermined limiting angle mode and the engine rotation speed N A  (N B ) is reduced to the set rotation speed N set . 
     According to the construction, even if the angle β of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive device  10 A ( 10 B), the steering of the outdrive devices  10 A ( 10 B) can be corrected. 
     When the angle β of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive device  10 A ( 10 B), the rotation angle θ A  (θ B ) of the outdrive device  10 A ( 10 B) is fixed at the state of the predetermined limiting angle. 
     According to the construction, when the angle of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive devices  10 A ( 10 B), frequent change of the rotation angle and frequent switching of forward/reverse rotation of the outdrive device  10 A ( 10 B) is prevented. 
     When the angle β of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive device  10 A ( 10 B), the engine rotation speed N A  (N B ) of the engine  3 A ( 3 B) is reduced following the reduction of the minor angle between the direction β of the composition vector T A  (T B ) and the lateral direction of the hull. 
     According to the construction, when the angle β of the composition vector T A  (T B ) is over the predetermined angle range of the outdrive devices  10 A ( 10 B), the switching of forward/reverse rotation of the outdrive devices  10 A ( 10 B) can be performed smoothly. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for a ship having an inboard motor in which a pair of left and right engines are arranged inside a hull and power is transmitted to a pair of left and right outdrive devices arranged outside the hull.