Abstract:
A ship of the invention comprises: a main propeller  2  which can move the ship forward and reverse by normal rotation, reverse rotation or by changing the pitch angle; a drive unit which drives the main propeller  2;  a rudder  3  which changes the course of the ship; and at least one pod propulsion unit  10 A,  10 B. As a result, the support mechanism and the turning mechanism of the pod propulsion unit arranged separated to the main propeller can be simplified, and cost can be reduced.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a ship incorporating a pod propulsion unit in addition to a main propeller, and an operating method therefor.  
           [0003]    2. Background Art  
           [0004]    Recently, in propulsion devices for ships, in the case where the thrust generated by the main propeller is insufficient, it has been suggested, in order to increase the thrust, to provide a pod propulsion unit to the rear or the front of the main propeller at a position which does not interfere.  
           [0005]    [0005]FIG. 9 shows a relating technology explained in Japanese Patent Application No. 2001-199418 which was filed by the assignee of the present application on Jun. 29, 2001 and has not been published yet. In the technology shown in FIG. 9, reference symbol  1  denotes the stern of the hull of a ship,  2  denotes a main propeller for generating the main propulsive force for propelling the ship, while  10  denotes a pod propulsion unit. The main propeller  2  is rotated by a driving force from a drive mechanism (omitted from the figure) such as a diesel engine (generally referred to as the main engine).  
           [0006]    The pod propulsion unit  10  is furnished with a casing  11 , a pod propeller  12 , a strut  13 , and a support  14 .  
           [0007]    With regards to the casing  11 , the pod propeller  12  is provided at an approximately circular cylindrical rear portion or front portion, or at both the front and rear portions (not shown in the figure). The pod propeller  12  has the function of generating a propulsion force by rotation thereof. An electric motor for driving the pod propeller  12  is provided inside the casing  11 .  
           [0008]    The strut  13  of air foil section, is provided on the upper portion of the casing  11 . The support  14  which constitutes the overall turning axis for the pod propulsion unit  10  is provided on the upper end of the strut  13 . The support  14  is connected to a drive mechanism (not shown in the figure) provided on the hull side. Hence the pod propulsion unit  10  is provided so that the whole unit can be turned with respect to the stern  1  of the ship via the support  14 .  
           [0009]    The ship constructed in this way obtains a propulsive force by rotating the main propeller  2 , rotating the pod propeller  12 , or rotating both the main propeller  2  and the pod propeller  12  together. Furthermore, by turning the pod propulsion unit  10  about the support  14 , the strut  13  demonstrates a steering function to give a steering force, and thus turn the ship.  
           [0010]    In the abovedescribed ship, high speed cruising faster than for a ship equipped with only the main propeller  2  is possible. Furthermore, the strut  13  of the pod propulsion unit  10  can be used as a rudder. Consequently, when steering, particularly at the time of high speed cruising (for example, cruising in excess of around 20 knots), an excessive hydrodynamic force acts on the strut  13 , so that a very large force is applied to the support  14 . Therefore, there is the problem in that the support mechanism for supporting the support  14  and the turning mechanism for turning the pod propulsion unit  10  must have sufficient strength, that is, these must involve large mechanisms.  
           [0011]    The present invention takes into consideration the abovementioned circumstances, with the object of providing a ship and an operating method therefor, whereby the support mechanism and the turning mechanism and the like of the pod propulsion unit arranged at the rear of the main propeller can be simplified, and cost can be reduced.  
         SUMMARY OF THE INVENTION  
         [0012]    In order to solve the abovementioned problem, a ship of the present invention comprises: a main propeller which can move the ship forward and reverse by normal rotation, reverse rotation or by changing the pitch angle; a drive unit which drives the main propeller; a rudder which changes the course of the ship; and at least one pod propulsion unit.  
           [0013]    According to the ship of the present invention, the propulsive force is obtained from the main propeller and/or the pod propulsion unit, and steering is by means of the rudder, and/or the rudder due to the pod propulsion unit. Therefore, the ship speed can be increased, and the ship handling performance can be improved.  
           [0014]    The ship may further comprises: a speed log which measures the speed of the ship, and a control unit which controls a rudder angle of the pod propulsion unit based on a signal from the speed log.  
           [0015]    In this case, the rudder angle of the pod propulsion unit is controlled corresponding to a signal from a speed log for measuring the speed of the hull, that is corresponding to the ship speed. Therefore a situation where an excessive load is applied to the support mechanism and the turning mechanism of the pod propulsion unit can be prevented. Hence these mechanisms can be simplified and cost reduced.  
           [0016]    In the above ship, when a ship speed obtained by the speed log exceeds a predetermined value, the control unit may fix the rudder angle of the pod propulsion unit to zero degrees.  
           [0017]    In this case, if the ship speed exceeds a predetermined value, the rudder angle of the pod propulsion unit is fixed at zero. Therefore a situation where an excessive load is applied to the support mechanism and the turning mechanism of the pod propulsion unit can be prevented. Hence these mechanisms can be simplified and cost reduced.  
           [0018]    When a ship speed obtained by the speed log is less than a predetermined value, the control unit may set the rudder angle of the pod propulsion unit linked to a rudder angle of the rudder.  
           [0019]    In this case, the rudder angle of the pod propulsion unit is made to correspond to the rudder angle of the rudder. Therefore the ship operator simply orders (controls) only the rudder angle of the rudder. Hence, the rudder angle of the rudder and of the pod propulsion unit can be controlled simultaneously, and ship handling thus greatly simplified.  
           [0020]    The ship may further comprise a rudder angle switching device which switches the rudder angle of the pod propulsion unit to either one of +90° and −90°.  
           [0021]    In this case, the construction is such that by setting a switching device to a position of 0°, +90°, −90° the rudder angle of the pod propulsion unit is set to a position of 0°, +90°, −90°. Therefore construction of the overall equipment can be simplified. That is, the steering gear for the pod propulsion unit can be omitted, and hence cost is further reduced.  
           [0022]    The ship may further comprise a drive source which drives both a steering gear for changing the rudder angle of the rudder, and a turning drive mechanism which changes the rudder angle of the pod propulsion unit.  
           [0023]    In this case, a steering gear which changes the rudder angle of the rudder, and a turning drive mechanism which changes the rudder angle of the pod propulsion unit are driven by the same drive source. Therefore the construction of a drive source for driving the steering gear and the turning drive mechanism can be simplified, and hence cost can be further reduced.  
           [0024]    The second aspect of the present invention is a method for operating a ship comprising a main propeller which can move the ship forward and reverse by normal rotation, reverse rotation or by changing the pitch angle; a drive unit which drives the main propeller; a rudder which changes the course of the ship; at least one pod propulsion unit; a speed log which measures the speed of the ship; and a control unit which controls a rudder angle of the pod propulsion unit by means of a signal from the speed log. The operating method comprises the steps of: when the ship speed obtained by the speed log exceeds a predetermined value, changing the course direction of the ship by changing only the rudder angle of the rudder; and when the ship speed is less than a predetermined value, changing the course direction and/or the travelling direction of the ship using the rudder and the pod propulsion unit together, or using only the pod propulsion unit.  
           [0025]    According to the operating method for a ship, in changing the course direction and/or the travelling direction of the ship, when the ship speed exceeds a predetermined value, only the rudder is used, while when the ship speed is less than a predetermined value, the rudder and the pod propulsion unit are used together. Therefore, when the ship speeds exceeds a predetermined value, a situation where an excessive load is applied to the support mechanism and the turning mechanism of the pod propulsion unit can be prevented. Moreover, when the ship speed is less than a predetermined speed the ship handling performance can be improved.  
           [0026]    In the above method, a rudder angle of the pod propulsion unit may be controlled based on a signal from the speed log.  
           [0027]    In this case, the rudder angle of the pod propulsion unit is controlled corresponding to a signal from a speed log for measuring the speed of the hull, that is, corresponding to the ship speed. Therefore a situation where an excessive load is applied to the support mechanism and the turning mechanism of the pod propulsion unit can be prevented. Hence these mechanisms can be simplified and cost reduced.  
           [0028]    When a ship speed value obtained by the speed log exceeds a predetermined value, the rudder angle of the pod propulsion unit may be fixed at 0° by the control unit.  
           [0029]    In this case, if the ship speed exceeds a predetermined value, the rudder angle of the pod propulsion unit is fixed at 0°. Therefore a situation where an excessive load is applied to the support mechanism and the turning mechanism of the pod propulsion unit in cruising at a ship speed which exceeds the predetermined value, can be prevented. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0030]    [0030]FIG. 1A and FIG. 1B show an embodiment of a ship according to the present invention, FIG. 1A being a schematic starboard side view of the stern of the ship, and FIG. 1B being a view as seen in the direction of arrow A of FIG. 1A.  
         [0031]    [0031]FIG. 2 is a block diagram showing a configuration for controlling the rudder angle of a pod propulsion unit provided in the ship according to the present invention.  
         [0032]    [0032]FIG. 3 is a graph showing a relationship between operational rudder angle and ship speed illustrating an example of where a control apparatus for a ship according to the present invention controls the rudder angle of a pod propulsion unit.  
         [0033]    [0033]FIG. 4 is a graph showing a relationship between operational rudder angle and ship speed illustrating another example of where the control apparatus for a ship according to the present invention controls the rudder angle of a pod propulsion unit.  
         [0034]    [0034]FIG. 5 is a schematic starboard side view showing a different embodiment of a ship according to the present invention.  
         [0035]    [0035]FIG. 6 is a schematic starboard side view showing another embodiment of a ship according to the present invention.  
         [0036]    [0036]FIG. 7 is a schematic starboard side view showing yet another embodiment of a ship according to the present invention.  
         [0037]    [0037]FIG. 8 is a schematic starboard side view of the stern of a ship showing an example of a ship where a pod propulsion unit is provided in addition to a main propeller.  
         [0038]    [0038]FIG. 9 is a schematic starboard side view of the stem of a ship showing another example of a ship where a pod propulsion unit is provided in addition to a main propeller. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]    Hereunder is a description of embodiments of a ship according to the present invention, with reference to the drawings. Parts similar to those of the above mentioned technology are denoted by the same reference symbols, and detailed description thereof is omitted.  
         [0040]    As is shown in FIGS. 1A and 1B, this ship has a main propeller  2 , a rudder  3  located to the rear of the rudder  3  and turnably attached to the stern  1  of the ship via the support  4 , and two pod propulsion units  10 A and  10 B located on either side of the rudder  3 . The pod propulsion units  10 A and  10 B respectively has casings  11 A and  11 B, pod propellers  12 A and  12 B, struts  13 A and  13 B, and supports  14 A and  14 B.  
         [0041]    The rudder  3  is a planar member having a streamline cross-section. Furthermore, the support  4  is attached vertically to the top of the rudder  3 , and the upper end side of the support  4  is connected to a steering gear (omitted from the figure) provided on the hull side to turn the rudder  3  and the support  4  as one.  
         [0042]    The pod propulsion units  10 A and  10 B are each turnably attached to the stem  1  via the supports  14 A and  14 B. Regarding the pod propulsion units  10 A and  10 B, the pod propellers  12 A and  12 B for producing a thrust, are provided on the rear or on the front (on the front in the example in the figure). Moreover the pod propulsion units  10 A and  10 B are furnished with casings  11 A and  11 B housing a propeller drive mechanism (omitted from the figure) such as an electric motor thereinside, and struts  13 A and  13 B of airfoil section which are secured integrally to the upper portions of the casings  11 A and  11 B. The supports  14 A and  14 B are attached vertically to the top of the struts  13 A and  13 B, and the upper end side of the supports  14 A and  14 B are connected to steering drive mechanisms (omitted from the figure) provided on the hull side to turn the supports  14 A and  14 B, the struts  13 A and  13 B, the casings  11 A and  11 B, and the pod propellers  12 A and  12 B as one.  
         [0043]    In the pod propulsion units  10 A and  10 B constructed in this manner, a thrust is produced by rotating the pod propellers  12 A and  12 B to propel the ship. Moreover, by turning the whole of the thruster with respect to the stern  1 , a steering function is obtained, enabling the travelling direction of the ship to be changed.  
         [0044]    The pod propulsion units  10 A and  10 B are a type, as shown in the figure, with electric motors for outputting a drive force for the pod propellers  12 A and  12 B, installed inside the casings  11 A and  11 B, or a type which receives a drive force from a drive source (omitted from the figure) such as an electric motor installed on the hull side.  
         [0045]    In a ship of such a construction, a propulsive force can be obtained by rotating the main propeller  2  by itself, or by rotating one or both of the pod propellers  12 A and  12 B, or by rotating the main propeller  2  and one or both of the pod propellers  12 A and  12 B together.  
         [0046]    Furthermore, in order to change the course direction and/or the travelling direction of the ship, the rudder  3  is turned about the support  4 , or one or both of the pod propulsion units  10 A and  10 B are turned about the supports  14 A and  14 B, or the rudder  3  and one or both of the pod propulsion units  10 A and  10 B are turned.  
         [0047]    In the case where the change in the course direction and/or the travelling direction of the ship is mainly performed by the rudder  3 , the portions for the struts  13 A and  13 B of the pod propulsion units  10 A and  10 B can be made smaller than for the conventional case.  
         [0048]    As a result, the load applied to the support mechanism and the steering mechanism of the pod propulsion units  10 A and  10 B can be reduced, thus enabling simplification of these mechanisms.  
         [0049]    Consequently, when high speed cruising is required (for example at more than 20 knots), the thrust can be obtained by rotating the main propeller  2  and both of the pod propulsion units  12 A and  12 B together.  
         [0050]    Furthermore, when medium speed cruising is required (for example at around 12 knots) such as at the time of cruising in a channel, the thrust can be obtained by rotating the main propeller  2  by itself, or-by rotating only the two pod propellers  12 A and  12 B.  
         [0051]    Moreover, when low speed cruising is required (for example at less than 5 knots) such as when entering and leaving port, the thrust can be obtained by rotating only the two pod propulsion units  12 A and  12 B.  
         [0052]    In the present embodiment, in addition to the above construction there may be provided as shown in FIG. 2, a speed log  21  for measuring ship speed, and a control unit  22  which can control the rudder angle of the pod propulsion units  10 A and  10 B by means of a signal from the speed log  21 .  
         [0053]    By using these devices, then for example rudder angle control for the pod propulsion units  10 A and  10 B, as shown for example in FIG. 3 and FIG. 4 can be performed.  
         [0054]    The control shown in FIG. 3 illustrates a control where, when the ship speed is less than 5 knots, the rudder angle of the pod propulsion units  10 A and  10 B can be kept within a range of ±90° (here 0° degrees indicates the bow direction), while when the ship speed exceeds 20 knots, the rudder angle is fixed at zero and steering is not possible.  
         [0055]    That is to say, the information on ship speed obtained by the speed log  21  shown in FIG. 2 is sent as a signal to the control unit  22 , and the control unit  22 , based on this signal, controls the maximum rudder angle which the pod propulsion units  10 A and  10 B can take.  
         [0056]    Furthermore, the control shown in FIG. 4, controls such that, when the ship speed is less than 5 knots, the rudder angle of the pod propulsion units  10 A and  10 B can be kept within a range of ±90° (here 0° degrees indicates the bow direction), when the ship speed is more than 5 knots and less than 10 knots, the rudder angle of the pod propulsion units  10 A and  10 B can be kept within a range of ±70°, when the ship speed is greater than 10 knots and less than 15 knots, the rudder angle of the pod propulsion units  10 A and  10 B can be kept within a range of ±50°, when the ship speed is greater than 15 knots and less than 20 knots, this is kept within a range ±30°, and when the ship speed exceeds 20 knots, the rudder angle is fixed at zero and steering is not possible.  
         [0057]    As shown in FIG. 3 and FIG. 4, when the ship speed exceeds 20 knots for example, the rudder angle of the pod propulsion units  10 A and  10 B is fixed at zero, and the course is changed by the rudder  3  only. Hence an excessive hydrodynamic force does not act on the struts  13 A and  13 B, and a situation where an excessive load is applied to the supports  14 A and  14 B can thus be prevented. Consequently, the strength of the support mechanism for supporting the supports  14 A and  14 B, and the strength of the turning mechanism for turning the pod propulsion units  10 A and  10 B can be reduced, enabling these mechanisms to be simplified and cost thus reduced.  
         [0058]    A ship as described above furnished with the main propeller  2 , the rudder  3  located to the rear thereof and turnably attached to the stern  1  via the support  4 , the two pod propulsion units  10 A and  10 B located on either side of the rudder  3 , the speed log  21  for measuring ship speed, and the control unit  22  which can control the rudder angle of the pod propulsion units  10 A and  10 B by a signal from the speed log  21 , can be operated for example as hereunder.  
         [0059]    For example, when the ship is cruising at a high speed which exceeds a ship speed of 20 knots, the thrust can be obtained by rotating both the main propeller  2  and the two pod propellers  12 A and  12 B together, while the rudder angle of the pod propulsion units  10 A and  10 B is fixed at zero, and course change is performed by the rudder  3  only.  
         [0060]    Next, when cruising at more than 5 knots and less than 20 knots, the thrust is obtained by rotating the main propeller  2  alone, or by rotating only the two pod propellers  12 A and  12 B, and course change is performed by using the rudder  3  together with the pod propulsion units  10 A and  10 B which are controlled so that the maximum rudder angle depends on the ship speed.  
         [0061]    Moreover, when low speed cruising is required (for example at less than 5 knots) such as when entering and leaving port, thrust is obtained by rotating only the two pod propulsion units  12 A and  12 B, and course change and/or a change in travelling direction is performed by using the pod propulsion units  10 A and  10 B together with the rudder  3 .  
         [0062]    In particular, since the rudder angle of the pod propulsion units  10 A and  10 B at less than 5 knots can be ±90°, the pod propulsion units  10 A and  10 B can function as stern thrusters. Therefore, pier or shore docking can be made easy, and operating time required for entering and leaving port can be reduced.  
         [0063]    In the embodiment of the present invention, the description has been for where the operational rudder angle of the pod propulsion units  10 A and  10 B is ±90° (refer to FIG. 3 and FIG.4). However the present invention is not limited to this, and this may be ±360°.  
         [0064]    In particular, if when the ship speed is less than 5 knots, the operational rudder angle of the pod propulsion units  10 A and  10 B can be ±360°, then thrust in the rearward direction (stem power) which is variously used at the time of pier or shore docking can be obtained by the pod propulsion units  10 A and  10 B. Therefore there is no need to start a drive unit (in general the main engine) for rotating the main propeller  2  in order to obtain stem power.  
         [0065]    Furthermore the construction may be such that the rudder angle of the pod propulsion units  10 A and  10 B is linked to the rudder angle of the rudder  3  and the ship speed.  
         [0066]    That is to say, when for example the ship speed exceeds 20 knots, the rudder angle of the pod propulsion units  10 A and  10 B is fixed at zero degrees by the control unit  22 . When the ship speed is greater than 5 knots and less than 20 knots the rudder angle of the pod propulsion units  10 A and  10 B is made proportional to the rudder angle of the rudder  3 . For example, at +35° rudder angle for the rudder  3 , the pod propulsion units  10 A and  10 B have +14° rudder angle, and at +10° rudder angle for the rudder  3 , the pod propulsion units  10 A and  10 B have +4° rudder angle. Moreover, when the ship speed is less than 5 knots, then at +35° rudder angle for the rudder  3 , the pod propulsion units  10 A and  10 B have +90° rudder angle, and at +10° rudder angle for the rudder  3 , the pod propulsion units  10 A and  10 B have +45° rudder angle.  
         [0067]    By having such a construction, the ship operator can control the rudder angle of the rudder  3  and of the pod propulsion units  10 A and  10 B simultaneously by ordering only the rudder angle of the rudder  3 , thus greatly simplifying ship handling.  
         [0068]    Furthermore, an arrangement is possible such that the pod propulsion units  10 A and  10 B can only be used at a position where their rudder angle is for example +90° and −90°.  
         [0069]    That is to say, at the time of normal cruising, the rudder angle of the pod propulsion unit may be fixed at zero degrees, and steering performed by the rudder only, while at the time of pier or shore docking, the rudder angle of the pod propulsion units  10 A and  10 B may be positioned at for example +90 degrees or −90 degrees, so as to function as stern thrusters. Therefore pier or shore docking can be made easy, and operating time required for entering and leaving port can be reduced. Changing of this rudder angle position is performed by a separately provided switching device.  
         [0070]    By having such a construction, the steering gear for the pod propulsion unit can be omitted, and hence cost is further reduced.  
         [0071]    The construction may also be such that hydraulic pressure produced by the steering gear for the rudder  3  is also used in the turning drive mechanism which changes the rudder angle of the pod propulsion units  10 A and  10 B.  
         [0072]    That is to say, the hydraulic pressure produced by a hydraulic pump (drive source) provided in the steering gear of the rudder  3  is used in the turning drive mechanism which changes the rudder angle of the pod propulsion units  10  and  10 B. As a result, the hydraulic pump can be omitted from the turning drive mechanism, enabling simplification of the construction for the turning drive mechanism, and hence cost can be reduced.  
         [0073]    In the embodiment as described above, the description has been for where two pod propulsion units are provided. However the present invented is not limited to this, and as shown in FIG. 5, a single pod propulsion unit  10  incorporating a pod propeller  12  on the rear end of a casing  11  may be provided so that the main propeller  2 , the rudder  3  and the pod propulsion unit  10  are in sequence from the bow in a straight line along the keel line.  
         [0074]    Furthermore, as shown in FIG. 6, a single pod propulsion unit  10  incorporating a pod propeller  12  on the rear end of a casing  11  may be provided so that the main propeller  2 , the pod propulsion unit  10  and the rudder  3  are in sequence from the bow in a straight line along the keel line.  
         [0075]    Moreover, as shown in FIG. 7, a single pod propulsion unit  10  incorporating a pod propeller  12  on the front end of the casing  11  may be provided so that the main propeller  2 , the pod propulsion unit  10  and the rudder  3  are in sequence from the bow in a straight line along the keel line.