STEERING DEVICE

Abstract

 A steering device 4 for steering a gate rudder 11 comprising two rudder plates disposed so as to flank a propulsion device from lateral directions, includes a mode setting unit 41 that sets a steering mode to either a first steering mode in which the gate rudder 11 is steered with the two rudder plates kept substantially parallel to each other, or a second steering mode in which the gate rudder 11 is steered with rear edges of the two rudder plates kept closer to each other than when in the first steering mode, and a rudder angle control unit 42 that controls rudder angles of the two rudder plates according to the steering mode set by the mode setting unit 41.

Description

Technical field

[0001] This invention relates to a technique for steering a ship equipped with a rudder having two rudder plates.

Background Art

[0002] In recent years, a rudder system for ships, e.g., Gate Rudder^™, is known, in which two rudder plates are arranged to flank a propeller from both sides perpendicular to the direction of propulsion. Since the gate rudder does not obstruct the propulsive flow behind the propeller, it substantially improves the propulsive capability of the propeller and thus the fuel efficiency of the ship, compared to conventional rudders located behind the propeller.

[0003] As a technique related to the gate rudder, a steering device is known, which comprises a driving mechanism for rotating steering shafts, and a power mechanism for driving the steering shafts, in which two steering shafts are rotatably arranged with vertical rotation axes located on both sides of the propeller shaft, an upper portion of each of the rudder plates is connected to and suspended from each steering shaft, and rotation of the two steering shafts can turn the two rudder plates from the position aside the propeller to the down stream side of the propeller where the propeller aft flow is mostly blocked directly behind the propeller (e.g., Patent Document 1).

Citation List

Patent Document

[0004] Patent document 1: JP 5833278

Disclosure of the Invention

Problems to be solved by the invention

[0005] The problem to be solved by the present invention is to provide a steering device that can switch steering modes.

Means for Solving the Problems

[0006] In an embodiment, a steering device for steering a rudder comprising two rudder plates disposed so as to flank a propulsion device from lateral directions, includes a mode setting unit that sets a steering mode to either a first steering mode in which the rudder is steered with the two rudder plates kept substantially parallel to each other, or a second steering mode in which the rudder is steered with rear edges of the two rudder plates being positioned closer to each other than when in the first steering mode, and a rudder angle control unit that controls rudder angles of the two rudder plates according to the steering mode set by the mode setting unit.

Advantageous Effects of the Invention

[0007] An aspect of the present invention provides a steering device that can switch between steering modes.

Brief Description of the Drawings

[0008] 

Fig. 1 is a block diagram of the steering system in the first embodiment.

Fig. 2 is a schematic plan view of the gate rudder.

Fig. 3 is a schematic rear view of the gate rudder.

Fig. 4 is a flowchart showing the operation of the steering mode setting process for the first embodiment.

Fig. 5 is a schematic plan view of the gate rudder when the ship is steered in the starboard direction in the first steering mode.

Fig. 6 is a schematic plan view of the gate rudder when the ship is steered in the port direction in the first steering mode.

Fig. 7 is a schematic plan view of the gate rudder when the ship is steered in the straight-ahead direction in the second steering mode.

Fig. 8 is a schematic plan view of the gate rudder when the ship is steered in the starboard direction in the second steering mode.

Fig. 9 is a schematic plan view of the gate rudder when the ship is steered in the port direction in the second steering mode.

Fig. 10 is a flowchart showing the operation of the steering mode setting process for the second embodiment.

Best Mode for Carrying Out the Invention

[0009] A steering device according to embodiments of the present invention will now be described with reference to the drawings.

<First embodiment>

(Steering system)

[0010] The configuration of a steering system according to the first embodiment is described below. Fig. 1 is a block diagram showing the configuration of the steering system.

[0011] As shown in Fig. 1, the steering system 1 is equipped with an ECS (Electronic Chart System) 2, a route control unit 3, a steering device 4, a ship's hull 10, a gate rudder 11 that changes the direction of travel of the hull 10, a driving device 12 that drives the gate rudder 11, and sensors 13 that detect the state of the hull 10. The sensors 13 include at least a gyrocompass to detect the heading of the hull 10, a GNSS sensor that detects the ship's position by a satellite positioning system (GNSS). The ECS 2 may be an ECDIS (Electronic Chart Display and Information System).

[0012] The ECS 2 displays own ship and other ships on the electronic chart, as well as various information and user interface for the ship's navigator to set the ship's planned route. The ECS 2 also issues an entering notification to the steering device 4 indicating that the ship has entered a predetermined area. The route control device 3 performs navigation control to control the ship's position to follow the planned route set in the ECS 2, and heading control to control the ship's heading to follow the reference heading, and outputs the reference heading to the steering device.

[0013] The steering device 4 includes a mode setting unit 41 whose steering mode is set to either a first or second steering mode by the mode setting process described below, and a rudder angle control unit 42 that controls the driving device 12, that drives the gate rudder 11, so that the ship's heading follows the reference heading in the steering mode set by the mode setting unit 41.

(Gate Rudder)

[0014] The configuration of the gate rudder is described below. Figs. 2 and 3 show a schematic plan view and a schematic rear view, respectively, of the gate rudder configuration.

[0015] As shown in Figs. 2 and 3, the gate rudder 11 has two rudder plates 110a and 110b arranged to flank the propeller 14 from the lateral directions, i.e., perpendicular to the direction of the ship's propulsion and vertical direction, and two rudder shafts 111a and 111b provided corresponding to each of the rudder plates 110a and 110b. In the following description, when the two rudder plates 110a, 110 b are not specifically distinguished, they are simply referred to as a rudder plate 110. The two rudder shafts 111a and 111b are also referred to simply as a rudder shaft 111 when they are not specifically distinguished.

[0016] In this embodiment, the rudder plates 110 are substantially plate-shaped members installed substantially vertically. The rudder shafts 111 are installed at positions relatively offset inwardly in the lateral direction from the positions of the corresponding rudder plates 110, with the shaft's axes oriented substantially vertical, and the orientation of the rudder plates 110 are adjusted by the rotation of the corresponding rudder shafts driven by the driving device 12.

(Mode setting process)

[0017] The mode setting process is described below. Fig. 4 is a flowchart showing the operation of the steering mode setting process. Figs. 5 and 6 are schematic plan views showing the gate rudder when steered, respectively, into starboard and port directions in the first steering mode. Figs. 7, 8 and 9 are schematic plan views showing the gate rudder when steered, respectively, in the straight ahead, starboard, and port directions in the second steering mode.

[0018] As shown in Fig. 4, first, the mode setting unit 41 of the steering device 4 calculates the rate of turn (S101) based on the headings of the ship detected by the sensors 13 during a duration of time immediately after the true rudder angle has matched the rudder angle order by the rudder angle control unit 42, and determines whether the calculated rate of turn is less than a preset threshold value (S102).

[0019] If the rate of turn is not less than the threshold value (S102, NO), the mode setting unit 41 determines whether or not an entering notification has been issued by the ECS 2 (S103). The entering notification is issued when the ship is located within a predetermined area on the electronic chart displayed by the ECS 2, for example, areas within a certain distance from a wharf, mooring buoy, planned offshore anchorage point, offshore structure, etc.

[0020] If no entering notifications are issued (S103, NO), the mode setting unit 41 sets the steering mode of the rudder angle control unit 42 to the first steering mode (S104). When set to the first steering mode, the rudder angle control unit 42 controls the rudder angle of the gate rudder 11 in such a way that the two rudder plates 110 are kept parallel to each other, as shown in Figs. 2, 5, and 6. The rudder angle control unit 42 may also control the rudder angles of the gate rudder 11 to keep the rear sides of the two rudder plates 110 inclined outward in the lateral direction.

[0021] On the other hand, if an entering notification is issued (S103, YES), the mode setting unit 41 sets the steering mode of the rudder angle control unit 42 to the second steering mode (S105). The rudder angle control unit 42 set to the second steering mode controls the rudder angle of the gate rudder 11 to keep the rear sides of the two rudder plates 110 inclined inward in the lateral direction, as shown in Figs. 7, 8 and 9.

[0022] If the rate of turn is less than the threshold value in step S102 (S102, YES), the mode setting unit 41 sets the steering mode of the rudder angle control unit 42 to the second steering mode (S105).

[0023] Thus, by switching between the first steering mode, which prioritizes fuel efficiency, and the second steering mode, which prioritizes rudder effectiveness compared to the first steering mode, the gate rudder 11 can be steered appropriately for the navigational situation. While, in the description above, the first steering mode is a steering mode in which the rudder is steered with the rudder plates held parallel or inclined outward, and the second steering mode is a steering mode in which the rudder is steered with the rudder plates held inclined inward, the second steering mode may be a steering mode in which the rudder is steered with rear edges of the two rudder plates 110 kept closer to each other than in the first steering mode. While the present embodiment is described for a ship equipped with a propeller 14, the ship may alternatively be a one equipped with other propulsion devices, for example, a water jet propulsion system, etc.

[0024]  <Second embodiment>

[0025] In the first embodiment, the steering mode is switched based on the rate of turn; however, in this embodiment, the steering system differs from that of the first embodiment in that the steering mode is switched based on the speed-through-water instead of the rate of turn. Fig. 10 is a flowchart showing the operation of the steering mode setting process for this embodiment.

[0026] The steering system 1 of this embodiment differs from that of the first embodiment in that the sensors 13 include a speed log that detects a speed-through-water of the hull 10, and the steering device 4 receives the speed-through-water detected by the sensors 13.

[0027] First, as shown in Fig. 10, the mode setting unit 41 of the steering device 4 determines whether or not the speed-through-water detected by the sensors 13 is less than or equal to a predetermined threshold value (S201). The threshold value is set based on the pre-confirmed rudder effectiveness against speed-through-water. The correlation between the speed-through-water and rudder effectiveness is established based on, for example, simulations using ship motion models, measurements from water tank experiments, and measurements from test sailing of real ships.

[0028] If the speed-through-water is not less than the threshold value (S201, NO), the mode setting unit 41 sets the steering mode of the rudder angle control unit 42 to the first steering mode (S202).

[0029] On the other hand, if the speed-through-water is less than or equal to the threshold value (S201, YES), the mode setting unit 41 sets the steering mode of the rudder angle control unit 42 to the second steering mode (S203).

[0030] Thus, the calculation of the rate of turn may be spared and the amount of calculation involved in setting the steering mode may be reduced by setting the steering mode based on the evaluation of speed-through-water against a threshold value, wherein the threshold value is set based on the rudder effectiveness or, in other words, the correlation between the rate of turn and the speed-through-water. In addition, the use of the speed-through-water allows a switching of the steering mode that takes account of the effects on the hull 10 from wind directions, wind speeds, and direction and speed of currents.

[0031]  The embodiment of the present invention has been presented by way of example only, and is not intended to limit the scope of the invention. The novel embodiment described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes may be made without departing from the spirit of the invention. The embodiment and modifications are included in the scope or spirit of the present invention and in the appended claims and their equivalents.

Reference Signs List

[0032] 

4 Steering device

11 Gate rudder

41 Mode setting unit

42 Rudder angle control unit

Claims

1. A steering device for controlling a rudder comprising two rudder plates disposed so as to flank a propulsion device from lateral directions, comprising:

a mode setting unit that sets a steering mode to either

a first steering mode wherein the rudder is steered with the two rudder plates kept substantially parallel to each other, or

a second steering mode wherein the rudder is steered with rear edges of the two rudder plates kept closer to each other than in the first steering mode; and

a rudder angle control unit that controls angles of the two rudder plates
according to the steering mode set by the mode setting unit.

2. The steering device according to claim 1,
wherein the mode setting unit sets the steering mode to the second steering
mode when a rate of turn of a ship on which the rudder is disposed is below a predetermined threshold value.

3. The steering device according to claim 1,
wherein the mode setting unit sets the steering mode to the second steering
mode when a speed-through-water of a ship on which the rudder is disposed is below a predetermined threshold value.

4. The steering device according to either one of claims 1 - 3,
wherein the mode setting unit sets the steering mode to the second steering
mode when a position of a ship on which the rudder is disposed is within a predetermined area set on an electronic chart.

Drawing