Two-shaft four-rudder ship

Abstract

A steering control device 200 comprises a low-speed on-the-spot turning function unit which, in a state in which right and left propulsion propellers 101a, 101b are rotating at a constant low speed in the forward direction in a low speed range of ship maneuvering, sets a pair of high-lift rudders 102a, 102b corresponding to one propulsion propeller 101a to an astern steering angle, sets a pair of high-lift rudders 103a, 103b corresponding to the other propulsion propeller 101b to a forward steering angle, and implements an on-the-spot turning maneuver.

Description

Two-screw, four-rudder ship

[0001] The present invention relates to a two-shaft, four-rudder ship with two propulsion shafts and a pair of high-lift rudders behind each propeller, and relates to technology that enables easy maneuvering.

[0002] A conventional twin-shaft, twin-rudder ship, as shown in Japanese Patent Publication JP 2010-195302, for example, has a pair of left and right propellers arranged side by side at the rear of the hull, and a pair of left and right rudders arranged side by side at the rear of the hull behind the pair of left and right propellers and towards the centre of the hull, the pair of rudders having first guide surfaces on the inboard side that face each other and second guide surfaces on the outboard side that do not face each other, with the bulge of the second guide surface towards the outboard side protruding further than the bulge of the first guide surface towards the inboard side.

[0003] In addition, the twin-screw ship shown in Japanese Patent Publication No. 2012-35786 has a pair of left and right skeg sections spaced apart in the width direction of the hull at the stern of the hull, a pair of left and right propellers arranged at the rear ends of the skeg sections, and a pair of left and right rudders arranged behind the propellers at the stern, with the rudders extending along the width direction of the hull and equipped with movable fins that can rotate around an axis.

[0004] Traditionally, twin-shaft, twin-rudder systems have often been adopted for medium- to high-speed vessels such as ferries, passenger ships, naval vessels, and patrol boats, as well as shallow draft or wide cargo ships. The propellers on each of the two shafts rotate in opposite directions on the inboard or outboard side, and the propeller wakes also create swirling flows in opposite directions, so the fluid forces involved in steering a twin-shaft, twin-rudder vessel are complex, and it is not easy to estimate the vessel motion.

[0005] In turning maneuvering, rotating the propeller on one shaft in the forward direction and the propeller on the other shaft in the reverse direction makes turning easy, but because reversing the main engine and steering are complicated, there is a demand for improved maneuvering performance in terms of directional control and speed control.In addition, when one main engine becomes inoperable and the ship is steered only by the other main engine, steering is complicated, so easy maneuverability is required for twin-screw ships.

[0006] Like twin-screw vessels, some vessels use a pair of podded propellers at the stern. While the podded propellers are said to have good maneuverability due to their 360-degree rotation, they do not have a rudder behind the propellers, making them less capable of keeping course.

[0007] The present invention is intended to solve the above problems, and aims to provide a two-propeller, four-rudder ship with excellent maneuverability that allows for easy directional control and speed control.

[0008] In order to solve the above-mentioned problems, the twin-shaft, four-rudder ship of the present invention is provided with a thrust system and a steering system that controls the thrust system, the thrust system is provided with a pair of propeller shafts that rotate in opposite directions, a pair of left and right propellers with opposite blade angles that are attached to each propeller shaft and arranged at the stern, a pair of left and right high-lift rudders that are arranged behind each propeller, and a plurality of steering gears that drive each high-lift rudders, and the steering system is provided with a state in which the left and right propellers rotate at a constant rate in the forward direction, and each high-lift rudders is independently operated at various angles by each steering gear. The steering control device controls the direction of the propeller wake of each propeller, thereby controlling the direction of thrust acting around the stern on the hull, by changing the combination of rudder angles of a pair of high-lift rudders corresponding to each propeller, and by doing so, controls the direction of thrust acting around the stern on the hull.The steering control device is characterized by having a low-speed on-the-spot turning function unit that, in low-speed maneuvering, when the left and right propellers are rotating constantly at a low speed in the forward direction, sets the pair of high-lift rudders corresponding to one propeller to a reverse steering angle and sets the pair of high-lift rudders corresponding to the other propeller to a forward steering angle, thereby performing on-the-spot turning maneuvering.

[0009] The twin-shaft, four-rudder ship of the present invention comprises a thrust system and a steering system that controls the thrust system, the thrust system comprising a pair of propeller shafts that rotate in opposite directions, a pair of left and right propellers with opposite blade angles mounted on each propeller shaft and arranged at the stern, a pair of left and right high-lift rudders arranged behind each propeller, and a plurality of steering gears that drive each high-lift rudders, and the steering system operates each high-lift rudders independently to various angles with each steering gear while the left and right propellers rotate at a constant rate in the forward direction, and controls the propellers of each propeller by changing the combination of rudder angles of the pair of high-lift rudders corresponding to each propeller. The steering control device is equipped with a steering control device that controls the direction of the propeller wake and controls the direction of thrust acting around the stern on the hull, and is characterized by having a turning speed adjustment function unit that controls the turning speed during low-speed maneuvering, while the left and right propellers are rotating at a constant low speed in the forward direction, by controlling the pair of high-lift rudders corresponding to one of the propellers to increase or decrease the rudder angle within a reverse steering angle range while maintaining a symmetrical rudder angle, and by controlling the pair of high-lift rudders corresponding to the other propeller to increase or decrease the rudder angle within a forward steering angle range while maintaining a symmetrical rudder angle, and by controlling the moment acting around the stern on the hull to adjust the turning speed during low-speed maneuvering.

[0010] With the above configuration, in the twin-screw, four-rudder ship of the present invention, by changing the combination of rudder angles of a pair of high-lift rudders corresponding to each propeller, the propeller wakes generated from each propeller can be reliably controlled independently by a pair of high-lift rudders, and the direction of thrust acting on the hull around the stern can be controlled, thereby achieving easy and stable maneuverability in a twin-screw ship.

[0011] Generally, rudder is not very effective at low speeds, so the main engine output is temporarily increased to strengthen the propeller wake, but this is not necessary with the twin-shaft, four-rudder ship of the present invention.

[0012] In other words, in the twin-shaft, four-rudder ship of the present invention, when maneuvering at low speeds, with the left and right propellers rotating at a constant slow speed in the forward direction, by setting a pair of high-lift rudders corresponding to one of the propellers to a reverse rudder angle, a reverse thrust acts on one side of the stern, and by setting a pair of high-lift rudders corresponding to the other propeller to a forward rudder angle, a forward thrust acts on the other side of the stern, so that on-the-spot turning maneuvering can be achieved at low speeds without the need to reverse the rotation of the main engine or increase its power output.

[0013] Furthermore, in the twin-shaft, four-rudder ship of the present invention, when maneuvering at low speeds, with the left and right propellers rotating at a constant low speed in the forward direction, the magnitude of the astern thrust acting on one side of the stern can be adjusted by controlling the rudder angle of a pair of high-lift rudders corresponding to one of the propellers within the astern rudder angle range, and the forward thrust acting on the other side of the stern can be adjusted by controlling the rudder angle of a pair of high-lift rudders corresponding to the other propeller within the forward rudder angle range.This allows the turning speed during maneuvering at low speeds to be adjusted by controlling the moment around the stern acting on the hull without requiring reverse operation or power increase operation of the main engine, thereby achieving maneuvering performance that makes it easy to control the direction of the bow and the turning speed.

[0014] Schematic diagram showing the thrust system and maneuvering system of a two-propeller, four-rudder ship according to an embodiment of the present invention. Schematic diagram showing an overview of the thrust system according to the embodiment. Side view showing the configuration of the stern and bow according to the embodiment. Schematic diagram showing the maneuvering stand for the steering control device according to the embodiment. Block diagram showing the configuration of the maneuvering stand according to the embodiment. Schematic diagram showing the operating range of the high-lift rudder according to the embodiment. Schematic diagram showing the combined rudder angle and propulsion direction of the high-lift rudder in each of the maneuvers of (a) ahead (AHEAD), (b) hovering (HOVERING), and (c) astern (ASTERN) according to the embodiment. (d) forward left turn (TURN TO PORT), (e) forward left turn (ROTATE TO PORT), and turn left on the spot (+THRUSTER THRUST), (f) astern left (STERN TO PORT), and turn right on the spot (+THRUSTER THRUST), according to the embodiment. (g) A schematic diagram showing the combined rudder angle and thrust direction of the high-lift rudder in each of the maneuvers of (h) forward right turn (TURN TO STBD.), (i) forward right turn (ROTATE TO STBD.), turn right on the spot (+thruster thrust) ROTATE TO STBD. ON THE SPOT (+THRUSTER THRUST), (j) reverse right (STERN TO STBD.), turn left on the spot (+thruster thrust) ROTATE TO PORT ON THE SPOT (+THRUSTER THRUST), (k) reverse right turn (ASTERN TO STBD.) in the same embodiment. (h) A schematic diagram showing the combined rudder angle and thrust direction of the high-lift rudder in each of the maneuvers of (h) forward right turn (TURN TO STBD.), (i) forward right turn (ROTATE TO STBD.), turn right on the spot (+thruster thrust) ROTATE TO STBD. ON THE SPOT (+THRUSTER THRUST), (j) reverse right turn (STERN TO STBD.), turn left on the spot (+thruster thrust) ROTATE TO PORT ON THE SPOT (+THRUSTER THRUST), (k) reverse right turn (ASTERN TO STBD.) in the same embodiment. Schematic diagram showing the combined rudder angle and propulsion direction of the high-lift rudder in each maneuver of the (PORT ON THE SPOT)

[0015] The present invention will be described in detail below with reference to the accompanying drawings, in which: (Configuration of the embodiment) A twin-propeller, four-rudder ship according to the present embodiment includes a thrust system 100 and a steering system (steering control device) 200 that controls the thrust system 100, as shown in FIGS.

[0016] The thrust system 100 comprises a pair of propeller shafts 110a, 110b that rotate in opposite directions and are arranged at the stern of the hull 110; a pair of left and right propeller propellers 101a, 101b with opposite blade angles that are mounted on each propeller shaft 110a, 110b and arranged at the stern; and a pair of left and right high-lift rudders 102a, 102b on the starboard side and a pair of left and right high-lift rudders 103a, 103b on the port side that are arranged behind each propeller propeller 101a, 101b.

[0017] Each of the high-lift rudders 102a, 102b, 103a, and 103b is configured to be able to steer 105° outboard (outboard side) and 35° inboard (inboard side). While both propulsion propellers 101a, 101b are rotating in the forward direction, the pair of high-lift rudders 102a, 102b on the starboard side or the pair of high-lift rudders 103a, 103b on the port side can be operated independently to various angles, and the combination of the rudder angles of the pairs of high-lift rudders 102a, 102b, 103a, and 103b on both sides can be changed, thereby distributing the propeller wake in a desired direction and freely changing the thrust in each direction.

[0018] Therefore, by controlling the propeller wakes of the propellers 101a and 101b on both sides and controlling the thrust around the stern in all directions at 360°, the ship can be steered forward and backward, stopped, turned forward, turned backward, etc., and the movement of the ship can be freely controlled.

[0019] Furthermore, the thrust system 100 includes rotary vane steering gears 104a, 104b, 105a, and 105b that drive the high-lift rudders 102a, 102b, 103a, and 103b, rudder control devices (servo amplifiers) 106a, 106b, 107a, and 107b that control the rotary vane steering gears 104a, 104b, 105a, and 105b, a bow thruster 108 arranged on the bow side of the hull 110 and a thruster control device 109 that controls the bow thruster 108, and main engines 111a and 111b that drive each propulsion propeller 101a and 101b.

[0020] In addition, pump units 151a, 151b, 152a, 152b, rudder angle transmitters 153a, 153b, 154a, 154b, and feedback units 155a, 155b, 156a, 156b are connected to the rotary vane steering gears 104a, 104b, 105a, 105b, respectively, and the feedback units 155a, 155b, 156a, 156b are connected to the rudder control devices 106a, 106b, 107a, 107b.

[0021] The maneuvering system 200, which constitutes a steering control device, is stored in a maneuvering stand 250, and the stand housing integrally comprises the following: a gyro direction display unit 252 that displays the gyro direction of a gyrocompass 251, an auto-maneuvering unit 253 that steers the ship in a maneuvering mode by autopilot using a GPS compass, a joystick maneuvering unit 255 that steers the ship in a maneuvering mode by a joystick lever 254, a manual maneuvering unit 257 that steers the ship in a maneuvering mode by a manual steering wheel 256, a non-follow-up maneuvering unit 259 that steers the ship in a maneuvering mode by non-follow-up steering levers 258a, 258b, 258c, 258d, and a mode switching unit 261 that switches between the maneuvering units using a mode switching switch 260.

[0022] Furthermore, the navigation system is provided with a display device 262 having a touch panel on the screen, an image control unit 263 that controls the image displayed on the display device 262, an emergency stop unit 265 that operates in a steering mode that takes priority over all steering modes and brings the ship to an emergency stop by operating an emergency stop button 264, a rudder angle instruction unit 280 that gives an instruction rudder angle to the rotary vane steering gears 104a, 104b, 105a, 105b via the rudder control devices 106a, 106b, 107c, 107d, an electronic chart display unit 282 that displays an electronic navigation chart on the display device 262, a course line setting unit 283 that sets the planned route of the ship on the electronic navigation chart, a course correction unit 284 that corrects any deviation of the ship's position from the course line, a low-speed range steering switch button 285 that switches to steering in the low-speed range, and a low-speed range steering unit 286 that performs steering in the low-speed range.

[0023] The image control unit 263 selectively displays or simultaneously displays a nautical chart display image 266 that displays an electronic navigational chart, a gyro orientation display image 267 that displays the gyro orientation, an orientation display unit operation image 268 for touch-operating the gyro orientation display unit 252 on the monitor screen, and an auto-ship steering operation image 269 for touch-operating the auto-ship steering unit 253 on the monitor screen.

[0024] The joystick operation unit 255 is configured so that the joystick lever 254 can be operated in either the X or Y direction, and the tilt direction of the joystick lever 254 controls the commanded direction of movement of the hull, and the tilt angle in the tilt direction controls the commanded speed in the bow-stern direction and the commanded speed in the hull turning direction.

[0025] The joystick control unit 255 controls the rudder angles of the pair of high-lift rudders 102a, 102b, 103a, 103b on both sides to rudder angles set according to the tilt direction of the joystick lever 254, and by combining the rudder angles of the high-lift rudders 102a, 102b, 103a, 103b on both sides, the thrust of the propeller wake is turned in the desired direction, and the rotary vane steering gears 104a, 104b, 105a, 105b control the rudder angles of the pair of high-lift rudders 102a, 102b, 103a, 103b on both sides within a range of 105° outboard and 35° inboard. (See FIG. 6) The basic rudder angle combinations of the high-lift rudders 102a, 102b, 103a, and 103b, the states of the joystick lever 254, their names, propeller wake lines, and movement directions will be explained with reference to FIGS.

[0026] In Figures 7 to 9, the rudder is shown in horizontal cross section, and the rudder angle of each rudder is shown to the side or below. Rudder angles are shown as positive (+) to the right and negative (-) to the left, and names for combinations of these rudder angles are listed. The propeller wake is shown with a thin arrow, and the resulting propulsion direction of the ship is shown with a thick hollow arrow.

[0027] The rudder angles shown below are examples in this embodiment and do not limit the invention. In the following, the pair of high-lift rudders 102a, 102b on both sides and the pair of high-lift rudders 103a, 103b have the same pattern, and the port rudders and starboard rudders described below are the port rudders and starboard rudders of the pair of high-lift rudders 102a, 102b, 103a, 103b on both sides, respectively.

[0028] 7, (a) AHEAD is a pair of high-lift rudders 102a, 102b, 103a, 103b on both sides, with the port rudder at 0° and the starboard rudder at 0°. Similarly, (b) HOVERING, which stops the hull in place, is a port rudder at -75° and a starboard rudder at +75°, and (c) ASTERN is a port rudder at -105° and a starboard rudder at +105°.

[0029] As shown in Figure 8, (d) forward left turn (TURN TO PORT) is port rudder -35° and starboard rudder -35°, (e) forward left turn (ROTATE TO PORT) is port rudder -70° and starboard rudder -35°, (f) astern left turn (STERN TO PORT) is port rudder -105° and starboard rudder +45° to +75°, and (g) astern left turn (STERN TO PORT) is port rudder -105° and starboard rudder +75° to +105°.

[0030] As shown in Figure 9, (h) forward right turn (TURN TO STBD.) is port rudder +35° and starboard rudder +35°, (i) forward right turn (ROTATE TO STBD.) is port rudder +35° and starboard rudder +70°, (j) astern right shift (STERN TO STBD.) is port rudder -45° to -75° and starboard rudder +105°, and (k) astern right turn (STERN TO STBD.) is port rudder -75° to -105° and starboard rudder +105°.

[0031] In addition, (e) when rotating forward to the port (ROTATE TO PORT), if the thrust of the bow thruster 108 is applied in the starboard direction to increase the port turning speed, it becomes a rotate to the port on the spot (+THRUSTER THRUST), and (i) when rotating forward to the right (ROTATE TO STBD.), if the thrust of the bow thruster 108 is applied in the port direction to increase the right turning speed, it becomes a rotate to the port on the spot (+THRUSTER THRUST).

[0032] Similarly, (f) when reversing and leaning to the port (STERN TO PORT), if the thrust of the bow thruster 108 is applied in the port direction to increase the speed of turning to the right, the ship will turn to the right on the spot (ROTATE TO STBD. ON THE SPOT (+THRUSTER THRUST)), and (j) when reversing and leaning to the right (STERN TO STBD.), if the thrust of the bow thruster 108 is applied in the starboard direction to increase the speed of turning to the left, the ship will turn to the left on the spot (ROTATE TO PORT ON THE SPOT (+THRUSTER THRUST).

[0033] Furthermore, steering to move the hull in the beam direction while maintaining the bow heading is performed as follows: For example, (f) when reversing and leaning to the left (STERN TO PORT), applying thrust from the bow thruster 108 in the starboard direction results in leftward movement, and (j) when reversing and leaning to the right (STERN TO STBD.), applying thrust from the bow thruster 108 in the port direction results in rightward movement.

[0034] In this way, a two-screw, four-rudder ship having a pair of high-lift rudders 102a, 102b and 103a, 103b on both sides and equipped with a bow thruster 108 can reliably control each of the propeller wakes generated from each propeller 101a, 101b independently with the pair of high-lift rudders 102a, 102b and 103a, 103b by varying the combinations of rudder angles of the pair of high-lift rudders 102a, 102b and 103a, 103b on both sides corresponding to each propeller propeller 101a, 101bb, and thereby control the direction of thrust acting around the stern on the hull, thereby achieving easy and stable maneuverability in a twin-screw ship.

[0035] When maneuvering in the low speed range, a low speed range maneuvering unit 286 for maneuvering in the low speed range is activated by pressing a low speed range maneuvering switch button 285. The low speed range maneuvering unit 286 has a low speed on the spot turning function unit 287 and a turning speed adjustment function unit 288, and activation of the low speed range maneuvering unit 286 switches the rudder angle control by the joystick lever 254 to the low speed range maneuvering mode.

[0036] The auto-pilot unit 253 controls and guides the ship to a predetermined course based on the ship's current position information, guidance route information, and mooring position information from a GPS compass and an electronic chart system.

[0037] When the emergency stop button 264 is pressed in an emergency, the emergency stop unit 265 cancels the rudder angle related to the current maneuvering, regardless of the maneuvering state indicated by the joystick lever 254 or whether the ship is being maneuvered in another maneuvering mode, and turns the port rudder 103 to the starboard direction (clockwise as seen from above) and the starboard rudder 102 to the starboard direction (counterclockwise as seen from above) until they are hard over (fully turned), thereby applying braking force to the ship and stopping it.

[0038] The manual steering unit 257 controls the rudder angles of the two high-lift rudders 102 and 103 by rotating the manual steering wheel 256 to steer the ship.

[0039] The non-follow-up steering unit 259 steers the ship to starboard or port depending on the time that the non-follow-up steering levers 258a, 258b are operated left or right.

[0040] The operation of the above configuration will now be described.

[0041] Joystick Steering Mode Joystick steering mode is selected by operating the mode selector switch 260. The joystick steering unit 255 uses the joystick lever 254 to command the direction of hull movement, command thrust in the bow and stern directions, and command thrust in the width direction.

[0042] In this maneuvering, a twin-screw, four-rudder ship has a pair of high-lift rudders 102a, 102b and 103a, 103b on both sides and is equipped with a bow thruster 108. By changing the combinations of the rudder angles of the pair of high-lift rudders 102a, 102b and 103a, 103b on both sides corresponding to each propeller propeller 101a, 101bb, the propeller wakes generated from each propeller 101a, 101b can be reliably controlled independently by the pair of high-lift rudders 102a, 102b and 103a, 103b, and the direction of thrust acting around the stern on the hull can be controlled in all directions of 360°, thereby achieving easy and stable maneuverability in a twin-screw ship.

[0043] In this type of maneuvering, there is no need to reverse the thrust of the propeller (reverse propeller rotation), and all maneuvering control can be performed with the main engine always rotating forward.By adjusting the rudder angle of both rudders, the ship speed can be controlled precisely and steplessly from the maximum forward speed corresponding to the propeller rotation speed at that time, to the maximum reverse speed, without adjusting the main engine rotation speed.

[0044] Generally, rudder effectiveness is poor at low speeds, and the output of the main engine is temporarily increased to strengthen the propeller wake, but this is not necessary with the twin-shaft, four-rudder ship of this embodiment.

[0045] When performing low-speed maneuvering while traveling at low speed in a harbor or congested waters with the twin-propeller and four-rudder ship according to this embodiment, the low-speed maneuvering unit 286 for maneuvering at low speeds is activated by pressing the low-speed maneuvering switch button 285. Activating the low-speed maneuvering unit 286 switches the rudder angle control by the joystick lever 254 to low-speed maneuvering mode.

[0046] In the low-speed maneuvering mode, the turning direction is indicated by tilting the joystick lever 254, and the low-speed on-the-spot turning function unit 287 adjusts the rudder angles of the pair of high-lift rudders 102a, 102b, 103a, 103b on both sides while the left and right propulsion propellers 101a, 101b rotate at a constant speed in the forward direction.

[0047] For example, in the (n) rotation to starboard (ROTATE TO STBD. ON THE SPOT) maneuver shown in Figure 10, the pair of starboard high-lift rudders 102a, 102b corresponding to one starboard propeller 101a are set to astern steering angles, i.e., -105°, +105°, thereby applying astern thrust to the starboard side of the stern. Then, the pair of high-lift rudders 103a, 103b corresponding to the other port propeller 101b are set to forward steering angles, i.e., 0°, 0°, thereby applying forward thrust to the port side of the stern. This allows for spot rotation to starboard at low speeds without the need to reverse the rotation or increase the power output of the main engines 111a, 111b. While this maneuver does not generally require the thrust of the bow thruster 108, it may be utilized in some cases.

[0048] 10 (m), a ship can be rotated to port on the spot by setting the pair of high-lift rudders 102a, 102b on the starboard side corresponding to one of the starboard propeller propellers 101a at a forward rudder angle, here 0°, 0°, so that a forward thrust acts on the starboard side of the stern.Then, by setting the pair of high-lift rudders 103a, 103b corresponding to the other port propeller propeller 101b at a reverse rudder angle, here -105°, +105°, so that a reverse thrust acts on the port side of the stern.This makes it possible to realize a ship that can be rotated to port on the spot at low speeds without requiring reverse rotation or power increase operation of the main engines 111a, 111b.

[0049] In the low-speed maneuvering mode, the left and right propulsion propellers 101a, 101b rotate at a constant low speed in the forward direction, and the turning speed adjustment function unit 288 controls the bow direction and turning speed by the tilt angle of the joystick lever 254.

[0050] For example, during maneuvering for (n) ROTATE TO STBD. ON THE SPOT as shown in Figure 10, the pair of starboard high-lift rudders 102a, 102b corresponding to one of the starboard propeller propellers 101a are maintained at symmetrical rudder angles while being controlled to increase or decrease within the astern steering angle range, here between -75° and -105° and between +75° and +105°, in accordance with the tilt angle of the joystick lever 254, thereby increasing or decreasing the astern thrust on the starboard side of the stern.

[0051] Furthermore, during maneuvering for (n) ROTATE TO STBD. ON THE SPOT as shown in Figure 10, the pair of port side high-lift rudders 103a, 103b corresponding to the other port side propulsion propeller 101b are controlled to increase or decrease within the forward rudder angle range, here between -75° and 0° and between +75° and 0°, while maintaining symmetrical rudder angles, according to the tilt angle of the joystick lever 254, thereby increasing or decreasing the forward thrust on the port side of the stern.

[0052] Here, the pair of high-lift rudders 102a, 102b on both sides and the pair of high-lift rudders 103a, 103b on both sides may be controlled simultaneously, or only one of them may be controlled. The same applies to the maneuvering of the ship for rotating to port on the spot shown in Figure 10(b), and a description thereof will be omitted.

[0053] In this way, the turning speed during low-speed maneuvering is adjusted by controlling the moment around the stern acting on the hull without requiring reverse operation or power increase operation of the main engines 111a, 111b, thereby achieving maneuvering performance that allows easy control of the bow direction and turning speed.

[0054] Maneuvering mode using emergency stop unit With a single action of pressing the emergency stop button 264, the emergency stop unit 265 can be activated, and the ship can be stopped urgently, taking priority over all maneuvering modes. That is, regardless of the steering mode of the joystick lever 254 or other maneuvering modes, the emergency stop unit 265 switches to crash astern mode ("ASTERN" in which the port rudder is steered to 105° port and the starboard rudder is steered to 105° starboard for the pair of high-lift rudders 102a, 102b, 103a, 103b on both sides), generating extremely large braking force and astern force, and therefore the ship can be stopped in a much shorter time and distance than by maneuvering the ship by reversing the propellers.

[0055] Furthermore, even in the crash astern mode, there is no need to stop the main engines 111a, 111b and restart them in reverse, so the ship does not enter a so-called uncontrolled state during maneuvering, making it possible to respond quickly to emergencies during navigation.

[0056] Furthermore, if the ship needs to turn due to its characteristics or external disturbances while maneuvering using the emergency stopping unit 265, or if it is necessary to change the direction of travel, including the bow heading, by simply operating the joystick lever 254, the ship can be steered freely using the joystick lever 254 to navigate around the obstacle, just as with normal joystick operation.

[0057] Autopilot Steering Mode In normal ship navigation, the mode selector switch 260 is operated to select the autopilot steering mode.

[0058] An auto-ship steering operation image 269 is displayed on the monitor screen of the display device 262, and the position of the ship, the direction to go, the position to be reached or the bow and stern direction are input to the auto-ship steering section 253 by touching the monitor screen, and the ship is automatically guided and steered along the set course.

[0059] Furthermore, the electronic chart display unit 282 displays the electronic navigation chart as a chart display image 266 on the monitor screen of the display device 262, and the course line setting unit 283 sets the planned route of the ship on the electronic navigation chart.

[0060] The autopilot 253 controls the rudder angle appropriately based on the current position information of the ship, the guided route information, and the anchoring position information. The autopilot maintains the course indicated by the gyrocompass as the desired heading or bow and stern direction set in the autopilot operation image 269.

[0061] Manual Steering Mode The mode selector switch 260 is operated to select a steering mode using the manual steering wheel 256. In this steering mode, the rudder angles of the pairs of high-lift rudders 102a, 102b, 103a, 103b on both sides are instructed to the manual steering unit 257 by rotating the manual steering wheel 256, and the rudder angles of the two high-lift rudders 102a, 102b, 103a, 103b are controlled to steer the ship.

[0062] Non-follow-up steering mode A steering mode using the non-follow-up steering levers 258a, 258b is selected by operating the mode selector switch 260. In this steering mode, the non-follow-up steering unit 259 steers each of the rotary vane steering gears 104a, 104b, 105a, 105b corresponding to the non-follow-up steering levers 258a, 258b to the starboard or port side depending on the time that each of the non-follow-up steering levers 258a, 258b is operated to the left or right.

[0063] 100 Thrust system 101 Propulsion propeller 102a, 102b, 103a, 103b High-lift rudders 104a, 104b, 105a, 105b Rotary vane steering gears 106a, 106b, 107a, 107b Rudder control devices 108 Bow thrusters 109 Thruster control devices 110 Hull 110a, 110b Propeller shafts 151a, 151b, 152a, 152b Pump units 153a, 153b, 154a, 154b Rudder angle transmitters 155a, 155b, 156a, 156b Feedback units 200 Ship steering system 250 Ship steering stand 251 Gyrocompass 252 Gyro direction display unit 253 Auto ship steering unit 254 Joystick lever 255 Joystick steering unit 256 Manual steering wheel 257 Manual steering unit 258a, 258b Non-follow-up steering lever 259 Non-follow-up steering unit 260 Mode changeover switch 261 Mode changeover unit 262 Display device 263 Image control unit 264 Emergency stop button 265 Emergency stop unit 266 Nautical chart display image 267 Gyro bearing display image 268 Bearing display unit operation image 269 Auto steering operation image 280 Rudder angle indication unit 282 Electronic chart display unit 283 Course line setting unit 285 Low speed range steering changeover button 286 Low speed range steering unit 287 Low speed range on-the-spot turning function unit 288 Turning speed adjustment function unit

Claims

1. A ship having a thrust system and a steering system for controlling the thrust system, the thrust system comprising a pair of propeller shafts rotating in opposite directions, a pair of left and right propulsion propellers having opposite blade angles mounted on each propeller shaft and positioned at the stern, a pair of left and right high-lift rudders positioned behind each propulsion propeller, and a plurality of steering gears for driving each high-lift rudders, the steering system comprising a steering control device which, while the left and right propulsion propellers are rotating at a constant speed in the forward direction, operates each of the high-lift rudders independently at various angles using each steering gear, and by changing the combination of rudder angles of the pair of high-lift rudders corresponding to each propulsion propeller, controls the direction of the propeller wake of each propulsion propeller, thereby controlling the direction of thrust acting around the stern on the hull, A twin-shaft, four-rudder ship characterized in that the steering control device has a low-speed on-the-spot turning function unit that, during low-speed steering, sets a pair of high-lift rudders corresponding to one of the propulsion propellers to a reverse rudder angle, and sets a pair of high-lift rudders corresponding to the other propulsion propeller to a forward rudder angle, while the left and right propulsion propellers are rotating constantly at a low speed in the forward direction.

2. A ship having a thrust system and a steering system for controlling the thrust system, the thrust system comprising a pair of propeller shafts rotating in opposite directions, a pair of left and right propulsion propellers having opposite blade angles mounted on each propeller shaft and positioned at the stern, a pair of left and right high-lift rudders positioned behind each propulsion propeller, and a plurality of steering gears for driving each high-lift rudders, the steering system comprising a steering control device which, while the left and right propulsion propellers are rotating at a constant speed in the forward direction, operates each of the high-lift rudders independently at various angles using each steering gear, and by changing the combination of rudder angles of the pair of high-lift rudders corresponding to each propulsion propeller, controls the direction of the propeller wake of each propulsion propeller, thereby controlling the direction of thrust acting around the stern on the hull, A two-shaft, four-rudder ship characterized in that, during low-speed maneuvering, when the left and right propulsion propellers are rotating at a constant slow speed in the forward direction, the steering control device controls a pair of high-lift rudders corresponding to one of the propulsion propellers to increase or decrease the rudder angle within the astern rudder angle range while maintaining them at symmetrical rudder angles, and controls a pair of high-lift rudders corresponding to the other propulsion propeller to increase or decrease the rudder angle within the forward rudder angle range while maintaining them at symmetrical rudder angles, thereby controlling the moment around the stern acting on the hull and adjusting the turning speed during low-speed maneuvering.

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