Abstract:
The present invention relates to a propulsion arrangement for a marine vessel, which propulsion arrangement comprises an internal combustion engine, a shaft arrangement and a steerable thruster unit. The marine vessel further comprises an electric generator or a combined electric generator and motor in connection with the propulsion arrangement. In order to reduce space requirements and required equipment as well as to raise efficiency, the shaft arrangement comprises a main shaft extending from the internal combustion engine to a first angle gear and a drive shaft extending from the first angle gear to a second angle gear in the steerable thruster unit. The electric generator or the combined electric generator and motor is connected to the drive shaft of the shaft arrangement after the main shaft and the first angle gear are connected thereto.

Description:
This is a national stage application filed under 35 USC 371 based on International Application No. PCT/FI2005/050432 filed Nov. 23, 2005, and claims priority under 35 USC 119 of Finnish Patent Application No. 20055109 filed Mar. 10, 2005. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a propulsion arrangement for a marine vessel, which propulsion arrangement comprises an internal combustion engine, a shaft arrangement and a steerable thruster unit, whereby the marine vessel further comprises an electric generator or a combined electric generator and motor in connection with the propulsion arrangement. 
     Conventional marine vessels with the above type of propulsion arrangements and thereto related machinery may be provided with an additional device, particularly an electric generator or a combined electric generator and motor for generating e.g. hotel load electric power or for improving flexibility and redundancy in propulsion power. Such devices are often called shaft generators which, depending upon their location, may be used only as an electric generator or as an electric generator and an electric motor in combination. 
     Basically, an electric generator may be connected to the free end of the internal combustion engine, i.e. opposite the main shaft of the internal combustion engine, whereby no extra gear is necessary. This solution requires surplus space at the free end of the engine. Furthermore, such a generator can not provide power through the engine, i.e. it can not function as an electric motor. This type of single function arrangement is usually called a PTO (Power Take Off) arrangement. 
     Alternatively, a combined electric generator and motor may be connected to the main shaft of the internal combustion engine by means of a so-called step-up gear. Naturally the step-up gear necessitates additional equipment with thereto related costs. The step-up gear also causes transmission losses. Furthermore, this known solution requires sufficient and suitable space along the main shaft. This type of dual function arrangement is usually called a PTO/PTI (Power Take Off/Power Take In) arrangement. 
     However, in view of the general concepts discussed above, the additional device should be clearly understood as having three separate functions, i.e. firstly the additional device may installed to be used as an electric generator (PTO), secondly to be used mainly as an electric motor (PTI), and thirdly to be used as a combined electric generator and motor (PTO/PTI), whereby it may coupled so that it in a first mode functions as an electric generator and in a second mode as an electric motor. 
     The object of the present invention is to achieve a propulsion arrangement for a marine vessel by which the above disadvantages are avoided and which provides a multifunctional operation by way of a simplified arrangement. 
     SUMMARY OF THE INVENTION 
     The basic idea of the invention is to provide a propulsion system that includes an electric generator or a combined electric generator and motor and that may be directly employed also to the steerable thruster unit. This is realised by means of a propulsion arrangement, in which the shaft arrangement comprises a main shaft extending from the internal combustion engine to a first angle gear and a drive shaft extending from the first angle gear to a second angle gear in the steerable thruster unit. The electric generator or the combined electric generator and motor is connected to the drive shaft of the shaft arrangement, after the main shaft and the first angle gear connected thereto. The main shaft is thus free of any installations relating to the electric generator or the combined electric generator and motor. 
     According to an advantageous embodiment of the invention the electric generator is directly coupled to the drive shaft, above the first angle gear with respect to the steerable thruster unit. This eliminates any space requirements around the internal combustion engine or the main shaft. 
     According to another advantageous embodiment of the invention the electric generator is directly coupled to the drive shaft, above the first angle gear with respect to the thruster unit, and a coupling is provided on the drive shaft, between the electric generator and the first angle gear. In addition, this allows the internal combustion engine to drive the steerable thruster unit without turning the generator. 
     According to another advantageous embodiment of the invention the electric generator is directly coupled to the drive shaft, directly above the first angle gear with respect to the steerable thruster unit, and a coupling is provided on the drive shaft between the first angle gear and the second angle gear. In addition, this allows the internal combustion engine to turn the electric generator without driving the steerable thruster unit. 
     According to a further advantageous embodiment of the invention the combined electric generator and motor is directly coupled to the drive shaft, above the first angle gear with respect to the steerable thruster unit, and a coupling is provided on the main shaft, between the internal combustion engine and the first angle gear. This allows the combined electric generator and motor to drive the steerable thruster unit without turning the internal combustion engine. 
     According to an optional arrangement vis a vis the above mentioned further advantageous embodiment of the invention an auxiliary coupling may be provided between the combined electric generator and motor and the first angle gear. This additionally allows the internal combustion engine to drive the steerable thruster unit without turning the combined electric generator and motor. 
     According to another optional arrangement vis a vis the above mentioned further advantageous embodiment an auxiliary coupling may be provided between the first angle gear and the second angle gear. This additionally allows the internal combustion engine to turn the combined electric generator and motor without driving the steerable thruster unit. 
     The combined electric generator and motor may also be provided with a shaft section and a gear transmission, whereby it is connected to the drive shaft through the first angle gear by means of the gear transmission. The combined electric generator and motor is then preferably arranged on either side of or aft of the steerable thruster unit or the drive shaft, substantially in the plane of the main shaft and the first angle gear. 
     For this propulsion arrangement generally the main shaft is substantially horizontal or generally horizontally oriented, the drive shaft substantially vertical or generally vertically oriented, and the propeller shaft of the steerable thruster substantially horizontal or generally horizontally oriented, whereby transmission is provided through the first angle gear and the second angle gear as well as the angle transmission, when appropriate. 
     However, depending on the machinery arrangement, the main shaft may as well be inclined. 
     The coupling and auxiliary couplings are preferably so-called disconnecting couplings or flexible couplings and may be deployed according to the desired operational mode. 
     This simplifies the arrangements discussed above and reduces costs. Transmission losses also are reduced when the arrangements are used to drive the steerable thruster unit. No space is needed along the main shaft or at the free end of the internal combustion engine. On a whole, the invention also reduces the equipment on board the marine vessel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be described, by way of example only, more in detail with reference to the accompanying schematic drawings, in which 
         FIG. 1  shows a first embodiment of the present invention, 
         FIG. 2  shows a second embodiment of the present invention, 
         FIG. 3  shows a third embodiment of the present invention, 
         FIG. 4  shows a fourth embodiment of the present invention, 
         FIG. 5  shows a fifth embodiment of the present invention, and 
         FIG. 6  shows a sixth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the figures a marine vessel is generally indicated by reference numeral  1 . The marine vessel  1  is provided with a propulsion arrangement comprising an internal combustion engine  2 , typically a diesel engine, a shaft arrangement  3  and a steerable thruster unit  4 . The shaft arrangement  3  includes a main shaft  31  extending from the internal combustion engine  2  to a first angle gear  32 , which connects the main shaft  31  to a drive shaft  33 , and a second angle gear  34  arranged in the steerable thruster unit  4 . The second angle gear  34  connects the drive shaft  33  to a propeller shaft  41 , with a propeller  42 , in the steerable thruster unit  4 . 
     Power is thus transmitted from the internal combustion engine  2  by means of the substantially horizontal or generally horizontally oriented main shaft  31  to the first angle gear  32 , from the first angle gear  32  to the substantially vertical or generally vertically oriented drive shaft  33 , which drives the second angle gear  34 , which in turn drives the substantially horizontal or generally vertically oriented propeller shaft  41  with the propeller  42 . 
     An arrangement of this type with steerable thruster units  4  is generally called a Z-drive due to its configuration. 
     In the embodiment of  FIG. 1  the marine vessel  1  is provided with an electric generator  51  which is directly coupled to the drive shaft  33  and arranged directly above the first angle gear  32  with respect to the steerable thruster unit  4 . In this arrangement the electric generator  51  always turns when the propeller  42  is turning, i.e. when the steerable thruster unit  4  is driven by the internal combustion engine  2 . The electric generator  51  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the electric generator  51 , thus providing free space around the main shaft  31 . This set-up provides a so-called secondary PTO. 
     In the embodiment of  FIG. 2  the marine vessel  1  is provided with an electric generator  51  which is directly coupled to the drive shaft  33  and arranged above the first angle gear  32  with respect to the steerable thruster unit  4 . A coupling  61  is provided on the drive shaft  33  between the electric generator  51  and the first angle gear  32 . When the coupling  61  is disconnected, the internal combustion engine  2  can drive the steerable thruster unit  4 , i.e. the propeller  42 , without turning the electric generator  51 . The electric generator  51  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the electric generator  51 , thus providing free space around the main shaft  31 . 
     In the embodiment of  FIG. 3  the marine vessel  1  is provided with an electric generator  51  which is directly coupled to the drive shaft  33  and arranged directly above the first angle gear  32  with respect to the steerable thruster unit  4 . A coupling  61  is provided on the drive shaft  33  between the first angle gear  32  and the second angle gear  34 . When the coupling  61  is disconnected the internal combustion engine  2  can turn the electric generator  51  without driving the steerable thruster unit  4 , i.e. the propeller  42 . The electric generator  51  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the electric generator  51 , thus providing free space around the main shaft  31 . This set up provides a so-called primary PTO/PTI. 
     The electric generator  51  may be used for power take out, e.g. for the marine vessel hotel load. 
     In the embodiment of  FIG. 4  the marine vessel is provided with a combined electric generator and motor  52  which is directly coupled to the drive shaft and arranged above the first angle gear  32  with respect to the steerable thruster unit  4 . A coupling  61  is provided on the main shaft  31  between the internal combustion engine  2  and the first angle gear  32 . Due to this coupling the combined electric generator and motor  52  can drive the steerable thruster unit  4 , i.e. the propeller  42 , without turning the internal combustion engine  2 . 
     An additional auxiliary coupling  62  may be provided on the drive shaft  33 , between the combined electric generator and motor  52  and the first angle gear  32 . This auxiliary coupling  62  allows the internal combustion engine  2  to drive the steerable thruster unit  4 , i.e. the propeller  42 , without turning the combined electric generator and motor  52 . 
     The combined electric generator and motor  52  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the combined electric generator and motor  52 , thus providing free space around the main shaft  31 . 
     In the embodiment of  FIG. 5  the marine vessel is provided with a combined electric generator and motor  52  which is directly coupled to the drive shaft and arranged directly above the first angle gear  32  with respect to the steerable thruster unit  4 . A coupling  61  is provided on the main shaft  31  between the internal combustion engine  2  and the first angle gear  32 . Due to this coupling the combined electric generator and motor  52  can drive the steerable thruster unit  4 , i.e. the propeller  42 , without turning the internal combustion engine  2 . 
     An additional auxiliary coupling  62  may be provided on the drive shaft  33 , between the first angle gear  32  and the second angle gear  34 . This auxiliary coupling  62  allows the internal combustion engine  2  to turn the combined electric generator and motor  52 , without driving the steerable thruster unit  4 , i.e. the propeller  42 . This arrangement provides a so-called primary PTO. 
     The combined electric generator and motor  52  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the combined electric generator and motor  52 , thus providing free space around the main shaft  31 . 
     The embodiments discussed in  FIGS. 4 and 5  above may as well be carried out without the auxiliary coupling  62  providing the options also described above. The auxiliary coupling is thus optional. 
       FIG. 6  shows another arrangement, in which the marine vessel  1  is provided with a combined electric generator and motor  52  which by a shaft section  53  and a transmission gear  54  is connected to the first angle gear  32  of the shaft arrangement  3 . In this embodiment the combined electric generator and motor  52  is situated aft of the steerable thruster unit  4 , or the drive shaft  33 , i.e. opposite the main shaft  31  substantially aligned or in the same plane as the main shaft  31 . It is clear that the combined electric generator and motor  52  also may be on either side of the steerable thruster unit  4 , or in any in between position around the first angle gear  32 , and that it need not be in the same plane as the main shaft  31 . 
     The combined electric generator and motor  52  may be used for power take out, e.g. for the marine vessel hotel load, or it can be used alone or in combination with the internal combustion engine  2  to drive the steerable thruster unit  4 . 
     The combined electric generator and motor  52  is coupled to the drive shaft  33  after the main shaft  31  and the first angle gear  32  connected thereto in the direction of transmission of power from the internal combustion engine to the propeller  42 . Thereby the main shaft  31  is free from any connections with the combined electric generator and motor  52 , thus providing free space around the main shaft  31 . 
     The electric generator or the combined electric generator could be of a modified type, whereby it could be made to rotate without producing electricity. 
     The attached drawings and the description related thereto are only intended for clarification of the basic idea of the invention. The invention may vary in further detail within the scope of the ensuing claims.