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Title:
MARINE PROPULSION SYSTEM WITH ELECTRIC MOTOR ASSIST
Document Type and Number:
WIPO Patent Application WO/2014/089394
Kind Code:
A1
Abstract:
A propulsion system for a marine vessel comprises an internal combustion engine including an output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. A propeller shaft is coupled to the internal combustion engine. An electric machine is coupled to one of the output shaft or the propeller shaft. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the output shaft. The electric machine is activated to add torque to one of the output shaft or the propeller shaft in response to rotational speed data or loading data passing one or more predetermined threshold values for the output shaft.

Inventors:
CALDER NIGEL M (US)
Application Number:
PCT/US2013/073491
Publication Date:
June 12, 2014
Filing Date:
December 06, 2013
Export Citation:
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Assignee:
ELECTRO TECHNOLOGY HOLDINGS INC (US)
International Classes:
B63H21/20; B63H23/12
Domestic Patent References:
WO2003026957A12003-04-03
Foreign References:
DE102008061951A12010-06-17
US20110195618A12011-08-11
US20040192123A12004-09-30
SU1717477A11992-03-07
Attorney, Agent or Firm:
PROMMER, Peter, J. et al. (300 S. Riverside Plaza 16th floo, Chicago Illinois, US)
Download PDF:
Claims:
CLAIMS

What is claimed is:

1. A propulsion system for a marine vessel, the propulsion system comprising: an internal combustion engine including an output shaft, the internal combustion engine having a power curve based on a rotational speed of the output shaft, the power curve defining a rated power of the internal combustion engine at any given rotational speed of the output shaft;

an electric machine coupled to the output shaft, the output shaft extending into a first end of the electric machine and protruding out of a second end; a gearbox coupled to the output shaft at the second end of the electric machine;

a propeller shaft extending from the gearbox; and

a propeller coupled to the propeller shaft, the propeller having a propeller curve based on the rotational speed of the output shaft.

2. The propulsion system of claim 1, further comprising:

one or more sensors configured to monitor the rotational speed of the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers configured to activate the electric machine when the rotational speed of the output shaft approaches a rotational speed at an intersection point of the power curve and the propeller curve.

3. The propulsion system of claim 2, wherein the one or more controllers are configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

4. The propulsion system of claim 2, wherein at least one of the one or more controllers is operative to activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

5. The propulsion system of claim 1, further comprising:

one or more sensors configured to monitor a loading parameter of the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers configured to activate the electric machine when a loading parameter value received from the one or more sensors exceeds a threshold loading value for the output shaft.

6. The propulsion system of claim 5, wherein the loading parameter is torque.

7. The propulsion system of claim 5, wherein the loading parameter is torque and the threshold loading value for the output shaft is 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum rated torque of the internal combustion engine at a respective rotational speed of the output shaft.

8. The propulsion system of claim 5, wherein at least one of the one or more controllers is operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating.

9. The propulsion system of claim 1, further comprising:

one or more sensors configured to monitor the rotational speed of the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers being associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller and the internal combustion engine combination, the one or more controllers being configured to activate the electric machine when the rotational speed of the output shaft is outside of the zone of peak efficiency for the propeller.

10. The propulsion system of claim 9, wherein the electric machine is operative to switch between operating as an electric motor and as a generator.

11. The propulsion system of claim 1, wherein the propeller is an oversized propeller.

12. The propulsion system of claim 1, further comprising a first clutch mechanism, the first clutch mechanism disposed between the internal combustion engine and the electric machine and operative to engage and to disengage the internal combustion engine from the electric machine.

13. The propulsion system of claim 1, further comprising a second clutch mechanism, the second clutch mechanism disposed between the gearbox and the propeller shaft.

14. The propulsion system of claim 1, wherein the gearbox includes a reduction gear configured to be coupled to the propeller shaft, the reduction gear configured to reduce a rotational speed of the propeller shaft to a rotational speed less than the rotational speed of the output shaft.

15. The propulsion system of claim 14, wherein the propeller is a matched propeller.

16. The propulsion system of claim 14, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is matched to the reduction gear.

17. The propulsion system of claim 14, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is oversized with respect to the reduction gear.

18. The propulsion system of claim 1, wherein the electric machine is further operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

19. The marine propulsion system of claim 1, wherein the electric machine is further operative as a generator while the propeller is rotating and engaged with the electric machine.

20. The marine propulsion system of claim 1, wherein the internal combustion engine is a gas turbine.

21. The marine propulsion system of claim 1, wherein the internal combustion engine is a compression-ignition engine.

22. The propulsion system of claim 1, wherein the electric machine is disposed within a flywheel housing of the internal combustion engine, the electric machine including a rotor mounted to a flywheel coupled to the output shaft such that the electric motor is directly coupled to the output shaft of the internal combustion engine.

23. A marine vessel comprising the propulsion system of claim 1.

24. A propulsion system for a marine vessel, the propulsion system comprising: an internal combustion engine including a first output shaft, the internal combustion engine having a power curve based on a rotational speed of the output shaft, the power curve defining a rated power of the internal combustion engine at any given rotational speed of the output shaft;

a gearbox coupled to the first output shaft;

an electric machine including a second output shaft coupled to the gearbox; a propeller shaft extending from the gearbox; and

a propeller coupled to the propeller shaft, the propeller having a propeller curve based on the rotational speed of the first output shaft.

25. The propulsion system of claim 23, further comprising:

one or more sensors configured to monitor the rotational speed of the first output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers configured to activate the electric machine when the rotational speed of the first output shaft approaches a rotational speed at an intersection point of the power curve and the propeller curve.

26. The propulsion system of claim 25, wherein at least one of the one or more controllers is configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

27. The propulsion system of claim 25, wherein at least one of the one or more controllers is operative to activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

28. The propulsion system of claim 24, further comprising:

one or more sensors configured to monitor a loading parameter of the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers configured to activate the electric machine when a loading parameter value received from the one or more sensors exceeds a threshold loading value for the output shaft.

29. The propulsion system of claim 28, wherein the loading parameter is torque.

30. The propulsion system of claim 28, wherein the loading parameter is torque and the threshold loading value for the output shaft is 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum torque of the internal combustion engine at a respective rotational speed of the output shaft.

31. The propulsion system of claim 28, wherein at least one of the one or more controllers is operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating.

32. The propulsion system of claim 24, further comprising:

one or more sensors configured to monitor the rotational speed of the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers being associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller and the internal combustion engine combination, the one or more controllers being configured to activate the electric machine when the rotational speed of the output shaft is outside of the zone of peak efficiency for the propeller.

33. The propulsion system of claim 24, wherein the gearbox includes a reduction gear configured to be coupled to the propeller shaft, the reduction gear configured to reduce a rotational speed of the propeller shaft to a rotational speed less than the rotational speed of the first output shaft.

34. The propulsion system of claim 33, wherein the propeller is a matched propeller.

35. The propulsion system of claim 33, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is matched to the reduction gear.

36. The propulsion system of claim 33, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is oversized with respect to the reduction gear.

37. The propulsion system of claim 24, wherein the propeller is an oversized propeller.

38. The propulsion system of claim 24, further comprising a clutch mechanism, the clutch mechanism disposed between the gearbox and the electric machine.

39. The propulsion system of claim 24, wherein the electric machine is further operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

40. The propulsion system of claim 24, wherein the electric machine is further operative as a generator while the propeller is rotating and engaged with the electric machine.

41. The propulsion system of claim 24, wherein the electric machine is operative to switch between operating as an electric motor and as a generator.

42. The propulsion system of claim 24, wherein the internal combustion engine is a gas turbine.

43. The propulsion system of claim 24, wherein the internal combustion engine is a compression-ignition engine.

44. A marine vessel comprising the propulsion system of claim 24.

45. A propulsion system for a marine vessel, the propulsion system comprising: an internal combustion engine including an output shaft, the internal combustion engine having a power curve based on a rotational speed of the output shaft, the power curve defining a rated power of the internal combustion engine at any given rotational speed of the output shaft;

a propeller shaft coupled to the internal combustion engine;

an electric machine coupled to one of the output shaft or the propeller shaft; a propeller coupled to the propeller shaft, the propeller having a propeller curve based on the rotational speed of the output shaft.

one or more sensors configured to monitor and receive one of rotational speed data or loading data for the output shaft; and

one or more controllers operatively connected to the one or more sensors and the electric machine, the one or more controllers configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to one of received rotational speed data or loading data passing one or more predetermined threshold values for the output shaft.

46. The propulsion system of claim 45, wherein the output shaft is a crankshaft extending through the internal combustion engine, a first portion of the crankshaft extending out of a first end of the internal combustion engine and a second portion of the crankshaft extending out of a second end of the internal combustion engine, the first portion of the crankshaft including a crankshaft pulley, the electric machine being coupled to the crankshaft through a coupling between the electric machine and the crankshaft pulley.

47. The propulsion system of claim 45, wherein the coupling between the electric machine and the crankshaft pulley includes a belt.

48. The propulsion system of claim 45, wherein the coupling between the electric machine and the crankshaft pulley includes a one or more gears.

49. The propulsion system of claim 45, wherein the coupling between the electric machine and the crankshaft pulley is a direct coupling.

50. The propulsion system any one of claims 45-49, wherein the one or more sensors are configured to monitor and receive rotational speed data for the output shaft, and the one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to the received rotational speed data passing one of the one or more predetermined threshold values for the output shaft, the one or more predetermined threshold values being one or more rotational speeds of the output shaft approaching an intersection point of the power curve and the propeller curve.

51. The propulsion system of claim 50, wherein the one or more controllers are configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

52. The propulsion system of claim 50, wherein at least one of the one or more controllers is operative to activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

53. The propulsion system of any one of claims 45-49, wherein the one or more predetermined threshold values are a loading parameter value for the output shaft, the one or more sensors being configured to monitor and receive loading data for the output shaft, the one or more controllers being configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to the received loading data exceeding the loading parameter value.

54. The propulsion system of claim 53, wherein the loading parameter is torque.

55. The propulsion system of claim 53, wherein the loading parameter is torque and the threshold loading value for the output shaft is 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum rated torque of the internal combustion engine at a respective rotational speed of the output shaft.

56. The propulsion system of claim 53, wherein at least one of the one or more controllers is operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating.

57. The propulsion system of claim 45, wherein the one or more controllers are associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller curve and the internal combustion engine combination, the one or more controllers being configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft when the rotational speed of the output shaft is outside of the zone of efficiency for the propeller.

58. The propulsion system of claim 57, wherein the electric machine is operative to switch between operating as an electric motor and as a generator.

59. The propulsion system of any one of claims 45-58, wherein the output shaft of the internal combustion engine extends through a first end and a second end of the internal combustion engine, the propeller shaft being coupled to the internal combustion engine at the second end of the internal combustion engine, the electric machine including a second output shaft coupled to a portion of the output shaft extending from the first end of the internal combustion engine.

60. The propulsion system of any one of claims 45-59, wherein the propeller is an oversized propeller.

61. The propulsion system of any one of claims 45-60, further comprising a first clutch mechanism, the first clutch mechanism disposed between the internal combustion engine and the electric machine and operative to engage and to disengage the internal combustion engine from the electric machine.

62. The propulsion system of any one of claims 45-61, further comprising a second clutch mechanism, the second clutch mechanism disposed between a gearbox and the propeller shaft.

63. The propulsion system of any one of claims 45-58 and 60-62, further comprising a gearbox coupled to at least one of the output shaft and the propeller shaft.

64. The propulsion system of any one of claims 59 or 63, wherein the gearbox includes a reduction gear configured to be coupled to the propeller shaft, the reduction gear configured to reduce a rotational speed of the propeller shaft to a rotational speed less than the rotational speed of the output shaft.

65. The propulsion system of claim 64, wherein the propeller is a matched propeller.

66. The propulsion system of claim 64, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is matched to the reduction gear.

67. The propulsion system of claim 64, wherein the reduction gear is a higher- than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is oversized with respect to the reduction gear.

68. The propulsion system of any one of claims 45-67, wherein the electric machine is further operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

69. The marine propulsion system of any one of claims 45-68, wherein the electric machine is further operative as a generator while the propeller is rotating and engaged with the electric machine.

70. The marine propulsion system of any one of claims 45-69, wherein the internal combustion engine is a gas turbine.

71. The marine propulsion system of any one of claims 45-69, wherein the internal combustion engine is a compression-ignition engine.

72. The marine propulsion system of any one of claims 43, 50-58, and 60-71, wherein the electric machine is coupled to the output shaft through a gearbox.

73. The marine propulsion system of any one of claims 43, 50-58, and 60-71, wherein the electric machine is directly coupled to the output shaft.

74. The marine propulsion system of any one of claims 43, 50-58, and 60-71, wherein the electric machine is coupled to the output shaft through one of a belt assembly or a gear assembly.

75. The marine propulsion system of any one of claims 43, 50-58, and 60-71, wherein the electric machine is coupled to the propeller shaft through a gearbox.

76. A marine vessel comprising any one of the propulsion systems of claims 45-75.

Description:
MARINE PROPULSION SYSTEM WITH ELECTRIC MOTOR ASSIST

COPYRIGHT

[0001] A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.

FIELD OF THE INVENTION

[0002] The present invention relates generally to a marine propulsion system, and more particularly, to marine propulsion systems with an electric motor assist.

BACKGROUND OF THE INVENTION

[0003] Marine propulsion systems typically include internal combustion engines or electric motors with propellers. The efficiency of a marine propulsion system can be determined by the efficiency with which the propeller loads the engine, or the efficiency with which the propeller transmits power from the engine to the water in order to drive a marine vessel. There is need for marine propulsion systems that maximize the efficiency with which the propeller loads the engine and that maximize efficiency with which the propeller transmits power from the engine to the water.

SUMMARY OF THE INVENTION

[0004] According to one aspect of the present invention, a propulsion system for a marine vessel comprises an internal combustion engine including an output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. An electric machine is coupled to the output shaft. The output shaft extends into a first end of the electric machine and protrudes out of a second end. A gearbox is coupled to the output shaft at the second end of the electric machine. A propeller shaft extends from the gearbox. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the output shaft.

[0005] According to another aspect of the invention, a propulsion system for a marine vessel comprises an internal combustion engine including a first output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. A gearbox is coupled to the first output shaft. An electric machine including a second output shaft is coupled to the gearbox. A propeller shaft extends from the gear box. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the first output shaft.

[0006] According to yet another aspect of the invention, a propulsion system for a marine vessel comprises an internal combustion engine including an output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. A propeller shaft is coupled to the internal combustion engine. An electric machine is coupled to one of the output shaft or the propeller shaft. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the output shaft. One or more sensors are configured to monitor and receive one of rotational speed data or loading data for the output shaft. One or more controllers are operatively connected to the one or more sensors and the electric machine. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to one of received rotational speed data or loading data passing one or more predetermined threshold values for the output shaft.

[0007] Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description, which is made with reference to the drawings, a brief description of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates a top view of a simplified marine vessel with a propulsion system according to an embodiment of the present disclosure.

[0009] FIGS. 2 and 3 illustrate simplified exemplary configurations of marine propulsion systems according to some embodiments of the present disclosure.

[0010] FIG. 4 illustrates an exemplary engine fuel map for an internal combustion engine according to an embodiment of the present disclosure.

[0011] FIG. 5 illustrates exemplary propeller curves plotted on an engine fuel map according to an embodiment of the present disclosure.

[0012] FIG. 6 illustrates exemplary torque characteristics of internal combustion engines and electric machines according to an embodiment of the present disclosure.

[0013] FIG. 7 illustrates a simplified exemplary configuration of a marine propulsion system according to some embodiments of the present disclosure. [0014] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as described herein and by the appended claims.

DETAILED DESCRIPTION

[0015] While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. For purposes of the present detailed description, the singular includes the plural and vice versa (unless specifically disclaimed); the words "and" and "or" shall be both conjunctive and disjunctive; the word "all" means "any and all"; the word "any" means "any and all"; and the word "including" means "including without limitation."

[0016] A marine propulsion system typically includes an internal combustion engine and a propeller. In some aspects, between the engine and the propeller there may be, or may not be, forward and reverse gears with one or more clutches, and/or a reduction gear which slows the propeller's rotational speed (rpm) in relation to the engine speed.

[0017] The efficiency of the system is determined, among other things, by (i) the efficiency with which the propeller loads the engine, and (ii) the efficiency with which the propeller transmits power from the engine to the water in order to drive the boat or other marine vessel.

[0018] If the power absorbed by a propeller is expressed in terms of a graph showing power versus revolutions per minute (rpm), the resulting 'propeller curve' will not match a similar power versus rpm curve for the engine driving the propeller. If the two curves are plotted together, depending on the size of the propeller in relation to the engine, the propeller curve may (i) never cross the engine's power curve, in which case the propeller is 'undersized' in this application; (ii) cross the engine's power curve at full rated engine power and speed, in which case the propeller is 'matched' in this application; or (iii) cross the engine's power curve before the engine reaches full power and speed, in which case the propeller is Oversized' in this application and the engine will not be able to reach its full rated power and speed, and may be damaged from overloading.

[0019] The efficiency of an engine at any particular operating speed, and any load at that speed from no load to the engine's full rated power at that speed, can be described by a 'fuel map'. If propeller curves are plotted on an engine's fuel map it will be found that the manner in which propellers load an engine and absorb power from an engine is such that the power demands of a propeller rarely, if ever, load the engine at the peak efficiency for whatever speed it is operating.

[0020] Propellers that are oversized typically create loads on an engine that result in more efficient engine operation than do matched and undersized propellers, but an oversized propeller can prevent the engine from reaching its full rated power and speed, and can potentially damage the engine from overloading.

[0021] When it comes to transmitting engine power to the water, in many boats larger propellers operating at slower rotational speeds are more efficient than smaller propellers operating at higher rotational speeds.

[0022] Adding reduction gears to an engine slows down the propeller's rotational speed for a given engine speed. For any given engine power level, the slower the propeller speed the larger the matched propeller will be that is needed to transmit that power to the water. The larger propeller will be more efficient than will be a smaller propeller with a lower reduction gear operating at a higher rotational speed.

[0023] Mass is a measure of an object's resistance to acceleration. The greater the mass (weight) the greater is the resistance to acceleration. Torque is the force that overcomes this resistance to acceleration - it is a measure of the turning force being applied to a propeller shaft.

[0024] Engines develop no torque at zero rpm, and little torque at idling speeds. Larger propellers have more mass than smaller propellers. If propeller size and mass is increased beyond a certain point, an engine will not have the torque necessary to (i) get the propeller turning from the stationary position, or (ii) overcome the mass of a propeller that is rotating in the opposite direction to that desired if moving between forwards and reverse. In both cases, the engine will stall. Engine torque limitations create a limit on the extent to which propeller size and mass can be increased through increased reduction gearing. [0025] The present disclosure relates to the use of electric motors to apply torque to the output shaft of an internal combustion engine in order to turn a propeller in a boat or other marine vessel.

[0026] The electric motor can either be operated solely as an electric motor, or it can be operated as both an electric motor and as a generator (if driven by the engine, or by a freewheeling propeller). In the latter case it is known as an 'electric machine'.

[0027] Embodiments of the present disclosure relate to marine propulsion systems employing an internal combustion engine, a propeller, and an electric machine. The engine and electric machine can both be used to drive the propeller shaft, either independently or together.

[0028] In one embodiment, the electric machine drives the propeller without the internal combustion engine.

[0029] In another embodiment, the internal combustion engine drives the propeller with added torque provided by the electric machine.

[0030] In another embodiment, the engine drives the propeller without the electric machine.

[0031] In one embodiment, the high torque of the electric machine is used to drive a propeller that is oversized with respect to the engine and any reduction gear.

[0032] In another embodiment, a higher-than-normal reduction gear is used with the engine. A matched propeller with respect to this reduction gear is used. Added torque from the electric machine is used to prevent engine stalling.

[0033] In another embodiment, a higher-than-normal reduction gear is used with the engine. An oversized propeller with respect to this reduction gear is used. Added torque from the electric machine is used to prevent engine stalling.

[0034] In another embodiment, torque from the electric machine is added by any of the mechanisms described. The propeller is oversized. The electric machine is used to add power at higher engine speeds such that the combined engine and electric machine power enable the engine to reach its full rated power and speed in spite of the oversized propeller.

[0035] In another embodiment, torque from the electric machine is added by any of the mechanisms described. The propeller is oversized. The electric machine is used to add power at higher engine speeds such that the combined engine and electric machine power ensure that the engine is not overloaded by the oversized propeller. [0036] In one configuration, the stator of the electric motor or machine is built into the flywheel housing of the engine with the rotor mounted on the flywheel such that the electric motor or machine operates directly on the engine's output shaft (an Integrated Flywheel Generator - IFG - approach as is known in the field of the present disclosure). The rotor can be either internal to the stator or external to it.

[0037] In another configuration, the electric motor or machine is mounted externally to the engine and any transmission and/or reduction gear and is connected to the output shaft of the engine or any associated transmission or the propeller shaft by a belt or gears.

[0038] In another embodiment, the electric motor or electric machine is installed on the crankshaft pulley end of the engine and is connected to the crankshaft by a belt or gears or is directly coupled.

[0039] In one configuration there is a clutch in the drivetrain between the engine and its output shaft such that the engine can be de-coupled or disengaged from the propeller shaft and the electric motor can drive the propeller shaft independently of the engine.

[0040] In another configuration there is no clutch in the drivetrain between the engine and its output shaft with the result that the engine cannot be de-coupled or disengaged from the propeller shaft. In this configuration there may or may not be another mechanism for decoupling the electric motor or machine (for instance, a clutch at the electric motor or machine if the electric motor or machine is externally mounted).

[0041] In another configuration there is a clutch that enables the propeller to be disconnected from the engine and electric machine.

[0042] In general, this disclosure applies to any system for adding electric power to the drivetrain between an engine and a propeller, or to the engine crankshaft, with or without clutches at any point in the system.

[0043] Many electric motors develop high torque from zero rpm. Furthermore, electric motors are not stalled in the manner that an internal combustion engine is stalled. So long as the torque load imposed when accelerating a propeller from zero rpm is less than the electric motor's available torque, the motor will turn the propeller. In the event the propeller already has momentum in the opposite direction (as when moving between forwards and reverse) the electric motor will apply torque that first slows and stops the propeller and then starts it moving in the other direction. Even though the motor may initially be driven backwards, it will not stall. [0044] FIG. 1 illustrates a simplified top view of an exemplary marine vessel 100 that includes a propulsion system 110, such as the propulsion systems described in more detail herein including in the context of FIGS. 2-7. The propulsion system 110 can include a power source 112 that includes, for example, a primary power source (e.g., internal combustion engine) and a secondary power source (e.g., electric machine, electric motor). The power source can also include various transmission(s) or gearbox(es), gearing elements (e.g., reduction gear), flywheel(s), or clutch mechanism(s). The power source 112 is further coupled to a propeller 116 via a propeller shaft 114 extending from the power source 112. The propeller shaft 114 can be a single unit or may include various shaft parts and universal joint elements.

[0045] FIG. 2 illustrates a configuration in which the electric machine (3) is built into the flywheel housing of an engine (1). There may be, or may not be, a clutch (2) between the engine and the electric machine. The engine and electric machine can both drive a transmission (4) which may, or may not, have a reduction gear. The transmission may, or may not, have an internal clutch. There may be, or may not be, a clutch (5) between the transmission and/or reduction gear and the propeller. From the point of view of the present disclosure, a desirable aspect of this configuration is the ability of the electric machine to add torque to the propeller shaft in conjunction with the engine. Depending on whether or not clutch (2) is incorporated, the electric machine may be able to add torque to the shaft independently of the engine. Depending on whether or not there is a clutch in the transmission and/or reduction gear, or the added clutch (5), the engine may be, or may not be, able to drive the electric machine as a generator, with the propeller decoupled from the system. Depending on whether or not there is the clutch (2) between the engine (1) and the electric machine (3), a freewheeling propeller may be, or may not be, able to drive the electric machine as a generator with the engine decoupled.

[0046] FIG. 3 illustrates a configuration in which the electric machine (8) is mounted externally to the engine and any transmission and or reduction gear. In some aspects there may, and in some aspects there may not, be a clutch (9) between the electric machine and the propeller. This may be at the electric machine or at the propeller shaft, or integrated into any transmission and/or reduction gear (7). The electric machine may be attached to any transmission and/or reduction gear with any gear and clutch arrangement that permits the electric machine to add torque to the propeller shaft in conjunction with the engine (6). Depending on the clutch arrangements, it may be possible for the engine to drive the electric machine as a generator independent of the propeller, or for a freewheeling propeller to drive the electric machine as a generator independent of the engine.

[0047] It is contemplated that in the marine propulsion system illustrated in FIG. 3 that the electric machine (8) is 'behind' the engine (6) and can be connected into the propulsion system at a gearbox or after the gearbox, such as being connected to the propeller shaft itself. The rotational speed can be measured at an output shaft from the engine. However, it is also contemplated that the electric machine can be added to the propulsion system at any point along the crankshaft and drive train and the rotational speed can be measured at any point of the system from the crankshaft to the propeller.

[0048] In certain aspects, it is contemplated that the electric machine (8) can be a start- assist motor or a powerful starter-type motor (e.g., oversized starter motor), similar to what is used in certain hybrid automobile configurations. For electric machine aspects using a start- type motor configuration, the electric machine may be coupled to a flywheel housing (not illustrated) of the internal combustion engine rather than to the transmission or gearbox illustrated in FIG. 3.

[0049] Propulsion systems can include one or more controllers (e.g., exemplary controller 200, 300 or 700 in FIGS. 2, 3 or 7), such as an electronic control unit, PID controller, or a programmable logic controller, that is connected to one or more sensors (e.g., exemplary sensors 202, 204, 206 in FIG. 2, 302, 304, 306 in FIG. 3, and 702, 704 and 706 in FIG. 7) disposed adjacent to or near certain operating parts of the propulsion system. For example, a sensor may be disposed such that it is operative to monitor an output shaft or flywheel associated with an internal combustion engine, other components of the internal combustion engine, a transmission, a propeller shaft, the propeller itself, or the electric machine. For a sensor monitoring the rotational speed of one of the components of the propulsion system (e.g., output shaft, flywheel, propeller shaft), the controller may be operative to receive and process the rotational speed data. The one or more controllers are also operatively connected and configured for controlling the electric machine. For example, the one or more controllers may be operative to activate the electric machine when the rotational speed of the output shaft approaches zero, or to activate the electric machine when the rotational speed of the output shaft approaches a rotational speed at an intersection point of a power curve and a propeller curve (see FIGS. 4-6) for a given propulsion system. The one or more controllers can also be operatively connected and configured for monitoring other sensors and controlling other aspects of the propulsion system such as the internal combustion engine, clutch mechanism(s), and transmission or gearbox mechanisms.

[0050] FIG. 4 illustrates an exemplary engine fuel map. An engine fuel map provides information on the fuel consumption per unit of output energy produced by an engine over the full operating speed and load profile for the engine. The fuel consumption is typically expressed as grams per kilowatt-hour (g/kWh) or pounds per horsepower-hour (lbs/hp-h) and is known as 'Specific Fuel Consumption' (SFC). The data is typically displayed on a graph of torque versus engine speed or power versus engine speed. FIG. 4 is an example of a nominal fuel map based on power versus engine speed, and is a non-limiting, illustrative example for a 52KW (68 hp) diesel engine. It would be understood in the field of the present disclosure that fuel maps for other types of engines could be readily determined and applied according to the aspects described herein.

[0051] Peak efficiency for the exemplary engine in FIG. 4 occurs between 1300 rpm, and 2000 rpm at a load that increases from 20 kW to 30 kW (10). The fuel consumption is around 230 g/kWh in this operating band. Total fuel consumption at any point equals the load at that point (for example, 25 kW at 1700 rpm) times the fuel consumption at that point (in this case, 230 g/kWh): 25 x 230 = 5750 grams per hour. The standard weight of diesel is 840 grams per liter, in which case this converts to 6.85 liters (1.8 US gallons).

[0052] FIG. 5 illustrates an undersized (11), a matched (12), and an oversized (13) propeller curve plotted on the fuel map shown in FIG. 4. When matching a propeller to an engine, typically, a propeller size is selected for which the energy demand is such that the propeller curve crosses the engine's full power curve at, or very close to, the engine's full rated speed and power (the 'matched' propeller (12) in FIG. 5). If a propeller is undersized, the energy demand will be less than the engine's full rated power at full rated speed (the undersized propeller (11) in FIG. 5). If a propeller is oversized (13), the energy demand will result in the propeller curve crossing the engine's full power curve before the engine's full rated speed is reached. The engine speed will be limited to the speed at which the propeller curve crosses the engine's full power curve, with a resulting loss of peak power from the engine (the oversized propeller (13) in FIG. 5). It would be understood in the field of the present disclosure that propeller curves plotted on fuel maps for other types of engine and propeller combinations could be readily determined, such as the curve-fuel map plot illustrated in FIG. 5, and such curve-fuel map plots could be applied according to the aspects described herein. [0053] For any given engine and reduction gear, there will be a matched propeller (12). Increasing the propeller's diameter and/or the pitch will result in an oversized propeller (13). Oversizing typically moves the propeller curve into a more efficient part of the engine's fuel map, improving engine efficiency at all points along the propeller curve but at the expense of limiting peak engine power and rpm and potentially overloading the engine and damaging it. Decreasing propeller diameter and/or pitch (11) results in an undersized propeller which typically decreases fuel efficiency at points along the propeller curve, and does not allow the engine to develop its full rated power. If in FIG. 5 it is assumed that all three propellers - oversized (13), matched (12) and normal (11) - are applying a 20 kW load to the engine, the oversized propeller will operate at just under 240 g/kWh, the matched propeller at 250 g/kWh and the undersized propeller at just over 260 g/kWh - i.e. the oversized propeller forces the engine to operate more efficiently than the other propellers do.

[0054] If the focus is shifted from engine efficiency to propeller efficiency - i.e. the efficiency with which engine power is converted by a propeller into thrust and boat motion - this will be found to vary from propeller to propeller. However, in general, in displacement vessels large diameter propellers turning at slow speeds are more efficient than smaller diameter propellers turning at higher speeds. For example, given the engine in FIG. 5, for which the peak power is rated at 3,000 rpm, and given a matched propeller (i.e. one in which the propeller curve (12) crosses the engine's power curve at full rated speed and power), if a 2.74: 1 reduction gear is installed the peak shaft speed will be 1,095 rpm (3,000/2.74 = 1,095). A matched propeller in an exemplary boat might have a diameter of 23" with a peak efficiency of 51%. If the reduction gear is increased to 3.75: 1, the peak shaft speed will slow to 800 rpm (3,000/3.75 = 800). A matched propeller in the same exemplary boat will now have a diameter of 24" with a peak efficiency of 53%. In both cases, the propeller (12) is matched to the engine. The difference is that when the reduction gear is increased, the propeller speed is slowed, which then requires a larger propeller to absorb the full power and speed of the engine. For any given engine, increasing the reduction gearing will slow the propeller shaft speed, enabling a larger and more efficient propeller to be matched to the engine.

[0055] Peak efficiencies at the propeller can be achieved by installing the highest reduction gear possible and thus slowing the shaft speed such that the matched propeller (12) is as large as possible. Note that the propeller is still a matched propeller and the propeller curve will follow the path of the matched propeller (12) in FIG. 5. If the size of the propeller is now increased so that it is oversized for this reduction gear (13), the propeller curve can be moved into a more efficient part of the fuel map. A combination of high reduction gears and oversizing the propeller for the given reduction gear optimizes both propeller and engine efficiency, except that the oversizing limits peak engine speed and power and risks damaging the engine through overloading.

[0056] FIG. 6 illustrates the torque characteristics of engines (14) and electric motors (15). Engines (14) develop no torque at zero rpm, building torque with speed up to a peak torque, after which torque declines. At idling speeds, and the speeds that occur when a transmission is shifted between forwards and reverse, marine engines may develop around l/3 rd of their full rated torque. This substantially limits the size and mass of propeller that an engine can accelerate from zero rpm without stalling the engine. It would be understood in the field of the present disclosure that the torque v. engine rpm plot, such as the plot illustrated in FIG. 6, could be readily determined for many different electric machines and engine combinations and applied according to the aspects described herein.

[0057] Stalling is even more likely when switching between forwards and reverse because now the propeller is already turning, but in the opposite direction to what is desired. The engine has to be able to bring the propeller to a stop and to get it spinning in the other direction without stalling. More than one engine company has tried to improve propeller efficiency by adding high reduction gears in order to slow down propeller shaft speeds and drive large propellers, only to find the engine stalled as boats (or other marine vessels) came alongside a dock and went from forwards to reverse in order to stop the boat. Note that the propeller in this scenario is still nominally matched to the engine and reduction gear. The problem lies in the fact that as reduction gearing is increased, propeller shaft speeds slow resulting in a rise in the size and mass of a matched propeller. Above a certain level of reduction gearing, the mass of the matched propeller becomes too much for the engine to handle. Once an engine has stalled, combustion ceases and extemal power (e.g. a starter motor) is required to get things going again.

[0058] The ability of an internal combustion engine to swing a large propeller is accordingly limited by the torque available at idle speeds relative to the highest torque load imposed by the propeller when moving between forwards and reverse.

[0059] Many electric motors (15) develop full rated torque from zero rpm and then sustain this to rated speeds, after which torque declines. Furthermore, electric motors are not stalled in the manner that an internal combustion engine is stalled. So long as the torque load imposed when accelerating a propeller from zero rpm is less than the electric motor's available torque, the motor will rum the propeller. In the event the propeller already has momentum in the opposite direction (as when moving between forwards and reverse) the electric motor will apply torque that first slows and stops the propeller and then starts it moving in the other direction. Even though the motor may initially be driven backwards, it will not stall.

[0060] FIG. 7 illustrates a configuration in which the electric machine (16) is added to the crankshaft pulley (20) end of the engine (17). The electric machine (16) can be connected to the crankshaft pulley by a belt, gears or directly coupled (19). In some aspects there may be, and in some aspects there may not be, a clutch transmission (18) which may, or may not, include a reduction gear. In some aspects, the transmission may, or may not, include an internal clutch. From the point of view of the present disclosure, a desirable aspect of the configuration in FIG. 7 is the ability of the electric machine to add torque to the propeller shaft via the engine crankshaft in conjunction with the engine.

[0061] Some aspects of the present disclosure use an electric motor (e.g., 3, 8, 16) to add power to the drive train and propeller shaft (4, 7, 18) of a marine propulsion system through any of the mechanisms described above and as illustrated in FIGS. 2, 3 and 7 or to add power through other mechanisms known in the field of the present disclosure. This power may be added either with the internal combustion engine (1, 6, 17) running or without it running. If the system has a reduction gear (4, 7, 18) between the engine and the propeller, the gearing is determined by conventional mechanisms for matching reduction gears and propellers to an engine. A larger than normal (oversized (13)) propeller than can be used in a conventional installation is installed. The high torque characteristics of the electric motor (3, 8, 16) are used to add torque to the drivetrain (4, 7, 18) in a manner that prevents stalling of the engine (1, 6, 17) when maneuvering with the engine, and when moving between forwards and reverse. This enables the efficiency benefits of the oversized propeller to be realized without risk of stalling the engine.

[0062] Some aspects of the present disclosure use an electric motor (e.g., 3, 8, 16) to add power to the drive train and propeller shaft (4, 7, 18) of a marine propulsion system through any of the mechanisms described above or to add power through other mechanisms known in the field of the present disclosure. This power may be added either with the internal combustion engine (1, 6, 17) running or without it running. A higher reduction gear than typical for a conventional installation is used between the engine and the propeller, resulting in slower propeller shaft speeds and a larger diameter matched propeller (12) than typically used in the conventional installation. The high torque characteristics of the electric motor are used to add torque to the drivetrain (4, 7, 18) in a manner that prevents stalling of the engine when maneuvering with the engine (1, 6, 17), and when moving between forwards and reverse. This enables the efficiency benefits of the larger-than-normal but still nominally matched propeller to be realized without risk of stalling the engine.

[0063] Some aspects of the present disclosure use an electric motor (e.g., 3, 8, 16) to add power to the drive train and propeller shaft (4, 7, 18) of a marine propulsion system through any of the mechanisms described above or to add power through other mechanisms known in the field of the present disclosure. This power may be added either with the internal combustion engine (1, 6, 17) running or without it running. A higher reduction gear than typical for a conventional installation is used between the engine and the propeller, resulting in slower propeller shaft speeds and a larger diameter matched propeller (12) than typical can be used in the conventional installation. The propeller is then additionally oversized (13) with respect to this reduction gear. The high torque characteristics of the electric motor are used to add torque to the drivetrain (4, 7, 18) in a manner that prevents stalling of the engine when maneuvering with the engine (1, 6, 17), and when moving between forwards and reverse. This enables the efficiency benefits of both a higher-than-normal reduction gear and an oversized propeller with respect to this reduction gear to be realized without risk of stalling the engine.

[0064] Some aspects of the present disclosure use an electric motor (e.g., 3, 8, 16) to add power to the drive train and propeller shaft (4, 7, 18) of a marine propulsion system through any of the mechanisms described above or to add power through other mechanisms known in the field of the present disclosure. The propeller is oversized (13) with respect to the engine (1, 6, 17) and any given reduction gear (4, 7, 18), moving the propeller curve into a more efficient part of the engine's fuel map (see FIGS. 4 and 5). In the conventional system this would limit the peak speed and power of the engine and would potentially overload the engine. With the aspects of the present disclosure, the electric motor, or another electric motor, is used to add power to the drive train and propeller shaft at higher engine/shaft rotational speeds such that the combined engine and electric motor power can deliver the equivalence of the engine's full rated power to the propeller shaft without overloading the engine. In certain aspects, it can be desirable to have two electric motors where a first electric motor to add power when the internal combustion engine is operating at high rotational speeds and a second electric motor to add power when the internal combustion engine is operating at lower rotational speeds.

[0065] Additional aspects of the present disclosure can include any of the embodiments described above, including those embodiments described in the context of FIGS. 1-7, along with additional features described below. For example, it is contemplated that an oversized propeller or a high reduction gear can be applied to any type of internal combustion engine including a compression-ignition engine (e.g., diesel engine), a gasoline engine, a gas turbine, and others known in the field of marine propulsion systems. It is also contemplated that an oversized propeller or a high reduction gear can be applied to any number of propeller shafts.

[0066] The described aspects of the present disclosure are particularly desirable because they allow for a marine propulsion system to operate with added fuel efficiency over conventional marine propulsion systems. For example, fuel efficiency is improved in the marine propulsion systems of the present disclosure through larger-than-normal propeller(s) - whether achieved through oversizing the propeller, providing a high reduction gear, or both - without stalling the propulsion system. The efficiency gains achieved via oversizing occur at least in part as fuel efficiency gains in the internal combustion engine by moving into a more efficient part of the fuel map for a given engine. At the upper end of the engine's power curve the oversizing can cause undesirable overloading of the engine, but this is countered through the addition of added electric power through an electric machine that is part of the marine propulsion system described in the present disclosure. For example, in the exemplary power curves illustrated in FIGS. 4-6, it is contemplated that an electric machine can provide additional power to the marine propulsion system with an oversized propeller when the engine rpm exceeds at least 2000 rpms (e.g., at or near where the exemplary propeller curve intersects the exemplary engine power curve). It is also contemplated, as described above in the exemplary context of FIG. 6 and the simplified marine propulsion systems described in the exemplary context of FIGS. 2, 3 and 7, that the electric machine can apply power that is transmitted to the propeller when the marine propulsion system is at or near a stall condition.

[0067] In some aspects of the present disclosure, the marine propulsion system with electric motor assist includes an engine coupled to a propeller shaft. For example, in certain aspects, the electric machine may be built directly around the flywheel or propeller shaft where the shaft goes in one end of the electric machine and out the other end (e.g., the opposite end). It is also contemplated that the electric machine can also be added at any point 'behind' the engine (e.g., see FIG. 3) and be connected or coupled to the drivetrain (to a forward/reverse gear mechanism, or to a reduction gear, or to the propeller shaft - there are various places it can be added) with a gear, belt, or chain assembly. It is further contemplated that the electric machine can be placed at the front end of the engine (e.g., see FIG. 7) and connected to the crankshaft (and thus the drive train) through a direct coupling to the crankshaft, or via a gear, belt or chain assembly. Each of the described propulsion systems can include a forward and reverse gear mechanism, and may further include reduction gears. It is also contemplated that certain aspects of the propulsion systems do not include the forward and reverse gear mechanism or the reduction gear(s). The addition of the electric machine to the engine in the marine propulsion systems described in the present disclosure is particularly desirable because the electric machine adds torque at certain points in the engine operating cycle. If there is a forward and reverse gear mechanism the propulsion system will include a clutch. It is further contemplated that there may be one or more clutches between the electric machines of the different propulsion system configurations that are described and the engine/drive train. However, it is also contemplated that the clutch may not be present in some aspects as the electric machine can be coupled without clutches and allowed to freewheel when it is not needed to add torque or to act as a generator.

[0068] A desirable aspect of the marine propulsion systems described herein is that the exemplary electric machine and engine configurations provide for the electric machine to add torque at certain points of the engine cycle to allow the engine to handle an oversized propeller and/or a higher-than-normal reduction gear concomitant with a larger-than-normal propeller. This is accomplished without overloading the engine of the marine propulsion system. The torque may be added by the electric machine at any point in the mechanical system from the crankshaft to the propeller that is readily accessible to the electric machine, and with any of a number of combinations of gears and clutches such as the combinations described herein.

[0069] While the marine propulsion systems, such as the ones described for the present disclosure, will often include a gearbox, it is contemplated that some propulsion systems will not include a gear box feature. It is further contemplated that the marine propulsion system includes a mechanism, such as a system of sensor(s) that are electrically connected to and operative to send a signal to a controller. The system of sensor(s) and the controller can then trigger the electric machine to add torque based on a rotational speed and/or torque of an output shaft of the engine. The system of sensor(s) and the controller can also or alternatively be configured to trigger the electric machine to add torque based on knowledge of the engine fuel map and propeller curve (e.g., see FIGS. 4 and 5) for the propulsion system.

[0070] The marine propulsion systems that are described in the present disclosure are particularly desirable because the adding of torque through the electric motor assist provided by the electric machine allows an oversized propeller and/or a higher-than-normal reduction gear to be included as part of the marine propulsion system. By applying the electric machine to the described marine propulsion systems along with an unconventional propeller and/or reduction gear, , the propeller curve for the described systems is shifted to a different part of the engine's fuel map. The electric machine then provides a torque boost toward the ends of the propeller curve (e.g., see exemplary curves 11, 12, 13 in FIG. 5) to compensate for any torque issues for the engine that would typically arise in a conventional system. The torque boost can be applied by the electric machine to the engine or other propulsion components, such as the crankshaft, flywheel, at the output shaft from a gearbox, or at some point inside the engine that connects to the crankshaft.

[0071] In an alternative embodiment A, a propulsion system for a marine vessel includes an internal combustion engine (e.g., gasoline engine). The internal combustion engine includes an output shaft. The internal combustion engine has a power curve based on the rotational speed on the output shaft. The power curve defines a rated power of the internal combustion engine at any rotational speed of the output shaft. An electric machine is coupled to the output shaft. The output shaft extends through one end of the electric machine and protrudes out of another end. A gearbox is coupled to the output shaft at one of the ends of the electric machine. A propeller shaft extends from the gearbox. A propeller having a propeller curve based on the rotation speed of the output shaft is coupled to the propeller shaft.

[0072] In an alternative embodiment B, the propulsion system of alternate A can also include one or more sensors configured to monitor the rotational speed of the output shaft. The propulsion system also includes one or more controllers connected to the one or more sensors and the electric machine that are configured to activate the electric machine when the rotational speed of the output shaft approaches a speed at the intersection point of the power curve and the propeller curve so that the internal combustion engine is operative to reach the full rated power. [0073] In an alternative embodiment C, the one or more controllers of the propulsion system of alternate B are configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

[0074] In an alternative embodiment D, at least one of the one or more controllers of any one of the propulsions systems of alternates B or C can also be configured to activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

[0075] In an alternative embodiment E, the propulsion system of alternate A can also include one or more sensors configured to monitor the loading parameter of the output shaft. The propulsion system also includes one or more controllers connected to the one or more sensors and the electric machine that are configured to activate the electric machine when the loading parameter value received from the one or more sensors exceeds a threshold loading value for the output shaft so that the internal combustion engine is operative to reach full rated power.

[0076] In an alternative embodiment F, the loading parameter of the propulsion system of alternate E is torque.

[0077] In an alternative embodiment G, the loading parameter of alternate E is torque and the threshold loading value for the output shaft is 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum rated torque of the internal combustion engine at the respective rotational speed of the output shaft.

[0078] In an alternative embodiment H, the propulsion system of any one of alternates E to G can also include one or more of the controllers being operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating.

[0079] In an alternative embodiment I, the propulsion system of alternate A can also include one or more sensors configured to monitor the rotational speed of the output shaft and one or more controllers operatively connected to the one or more sensors and the electric machine. The controllers are associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller and the internal combustion engine combination. The one or more controllers are configured to activate the electric machine when the rotational speed of the output shaft is outside the zone of peak efficiency for the propeller.

[0080] In an alternative embodiment J, the electric machine of the propulsion system of alternate I is operative to switch between operating as an electric motor and as a generator.

[0081] In an alternative embodiment K, the propulsion system of any one of alternates A to J can also include a first clutch mechanism disposed between the internal combustion engine and the electric machine. The first clutch mechanism is operative to engage and disengage the internal combustion engine from the electric machine.

[0082] In an alternate embodiment L, the propulsion system of any one of alternates A to K can also include a second clutch mechanism disposed between the gearbox and the propeller shaft.

[0083] In an alternate embodiment M, the propulsion system of any one of alternates A to L can also include a gearbox with a reduction gear configured to be coupled to the propeller shaft. The reduction gear is configured to reduce the rotational speed of the propeller shaft to a rotational speed less that the rotational speed of the output shaft.

[0084] In an alternative embodiment N, the propeller of the propulsion system of alternate M is a matched propeller.

[0085] In an alternative embodiment O, the reduction gear of the propulsion system of alternate M is a higher-than-normal reduction gear. In some aspects, the propeller is matched to the reduction gear. In some aspects, the propeller is oversized with respect to the reduction gear.

[0086] In an alternative embodiment P, the propeller recited for any one of alternates A to O can be an oversized propeller.

[0087] In an alternative embodiment Q, the electric machine of any one of the propulsion systems of alternates A to I and K to P is operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

[0088] In an alternative embodiment R, the electric machine of any one of the propulsion systems of alternates A to I and K to P is operative as a generator while the propeller is rotating and engaged with the electric machine.

[0089] In an alternative embodiment S, the internal combustion engine of any one of the propulsion systems of alternates A to R is a gas turbine. [0090] In an alternative embodiment T, the internal combustion engine of any one of the propulsion systems of alternates A to R is a compression-ignition engine.

[0091] In an alternative embodiment U, the electric machine of any one of the propulsion systems of alternates A to T is disposed within a flywheel housing of the internal combustion engine. The electric machine also includes a rotor mounted to a flywheel coupled to the output shaft such that the electric motor is directly coupled to the output shaft of the internal combustion engine.

[0092] It is also contemplated that a marine vessel can include the propulsion system(s) from any one of alternates A to U.

[0093] In an alternative embodiment Al, a propulsion system for a marine vessel includes an internal combustion engine (e.g., gasoline engine) with a first output shaft having a power curve based on rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. The system further includes a gearbox coupled to the first output shaft and an electric machine including a second output shaft coupled to the gearbox. A propeller shaft extends from the gearbox. The propeller shaft is couple to a propeller. The propeller has a propeller curve based on the rotational speed of the first output shaft.

[0094] In an alternative embodiment Bl, the propulsion system of alternate Al can also include one or more sensors configured to monitor the rotational speed of the output shaft. The propulsion system also includes one or more controllers connected to the one or more sensors and the electric machine that are configured to activate the electric machine when the rotational speed of the output shaft approaches a speed at the intersection point of the power curve and the propeller curve so that the internal combustion engine is operative to reach the full rated power.

[0095] In an alternative embodiment CI, at least one of the one or more controllers of the propulsion system of alternate Bl are configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

[0096] In an alternative embodiment Dl, at least one of the one or more controllers of any one of the propulsion system of alternates Bl or CI can also activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

[0097] In an alternative embodiment El, the propulsion system of alternate Al can also include one or more sensors configured to monitor the loading parameter of the output shaft. The propulsion system also includes one or more controllers connected to the one or more sensors and the electric machine that are configured to activate the electric machine when the loading parameter value received from the one or more sensors exceeds a threshold loading value for the output shaft so that the internal combustion engine is operative to reach full rated power.

[0098] In an alternative embodiment Fl, the loading parameter of the propulsion system of alternate El is torque.

[0099] In an alternative embodiment Gl, the loading parameter of the propulsion system of alternate El is torque and the threshold loading value for the output shaft is 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum rated torque of the internal combustion engine at the respective rotational speed of the output shaft.

[00100] In an alternative embodiment HI, the propulsion system of any one of alternates El to Gl can also include one or more of the controllers being operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating.

[00101] In an alternative embodiment II, the propulsion system of alternate Al can also include one or more sensors configured to monitor the rotational speed of the output shaft and one or more controllers operatively connected to the one or more sensors and the electric machine. The one or more controllers are associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller and the internal combustion engine combination. The one or more controllers are configured to activate the electric machine when the rotational speed of the output shaft is outside the zone of peak efficiency for the propeller.

[00102] In an alternate embodiment Jl, the propulsion system of any one of alternates Al to II can also include the gearbox with a reduction gear configured to be coupled to the propeller shaft. The reduction gear is configured to reduce the rotational speed of the propeller shaft to a rotational speed less than the rotational speed of the output shaft. [00103] In an alternative embodiment Kl, the propeller of the propulsion system of alternate Jl is a matched propeller.

[00104] In an alternative embodiment LI, the reduction gear of the propulsion system, of alternate Jl is a higher-than-normal reduction gear. . In some aspects, the propeller is matched to the reduction gear. In some aspects, the propeller is oversized with respect to the reduction gear.

[00105] In an alternative embodiment Ml, the propeller of any one of the propulsions systems of alternates Al to Jl can be an oversized propeller.

[00106] In an alternative embodiment Nl, the propulsion system of any one of alternates Al to Ml can also include a clutch mechanism disposed between the gearbox and the electric machine.

[00107] In an alternative embodiment 01, the electric machine of any one of the propulsion systems of alternates Al-Nl is operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

[00108] In an alternative embodiment PI, the electric machine of the propulsion systems of alternates Al-Ol is operative as a generator while the propeller is rotating and engaged with the electric machine.

[00109] In an alternative embodiment Ql, the electric machine of the propulsions system of any one of alternates Al to PI is operative to switch between operating as an electric motor and as a generator.

[00110] In an alternative embodiment Rl, the internal combustion engine of the propulsion systems of any one of alternates Al-Rl is a gas turbine.

[00111] In an alternative embodiment SI, the internal combustion engine of the propulsion system of any one of alternates Al-Rl is a compression- ignition engine.

[00112] In an alternative embodiment Tl, the propulsion systems of any one of alternates Al to SI can include the second output shaft of the electric machine being coupled to the gearbox through a coupling between the electric machine and the internal combustion engine. In some aspects, the electric machine is coupled to the internal combustion engine through a coupling between first output shaft and the second output shaft.

[00113] In an alternative embodiment Ul, the propulsion system of any one of alternates Al to SI further include a crankshaft pulley connected to the first output shaft, the second output shaft of the electric machine being coupled to the gearbox through a coupling between the electric machine and the internal combustion engine at the crankshaft pulley. [00114] It is also contemplated that a marine vessel can include the propulsion system(s) from any one of alternates Al to Ul .

[00115] In an alternative embodiment A2, a propulsion system for a marine vessel comprises an internal combustion engine (e.g., gasoline engine) including an output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. A propeller shaft is coupled to the internal combustion engine. An electric machine is coupled to one of the output shaft or the propeller shaft. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the output shaft. One or more sensors are configured to monitor and receive one of rotational speed data or loading data for the output shaft. One or more controllers are operatively connected to the one or more sensors and the electric machine. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to one of received rotational speed data or loading data passing one or more predetermined threshold values for the output shaft.

[00116] In an alternative embodiment B2, the propulsion system of alternate A2 can also include the output shaft being a crankshaft extending through the internal combustion engine. A first portion of the crankshaft extends out of a first end of the internal combustion engine and a second portion of the crankshaft extends out of a second end of the internal combustion engine. The first portion of the crankshaft includes a crankshaft pulley. The electric machine is coupled to the crankshaft through a coupling between the electric machine and the crankshaft pulley.

[00117] In an alternative embodiment C2, the propulsion system of alternate A2 can also include the coupling between the electric machine and the crankshaft pulley being a belt.

[00118] In an alternative embodiment D2, the propulsion system of alternate A2 can also include the coupling between the electric machine and the crankshaft pulley being one or more gears.

[00119] In an alternative embodiment E2, the propulsion system of alternate A2 can also include the coupling between the electric machine and the crankshaft pulley being a direct coupling.

[00120] In an alternative embodiment F2, the propulsion system any one of alternates A2- E2 include the one or more sensors being configured to monitor and receive rotational speed data for the output shaft. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to the received rotational speed data passing one of the one or more predetermined threshold values for the output shaft. The one or more predetermined threshold values are one or more rotational speeds of the output shaft approaching an intersection point of the power curve and the propeller curve.

[00121] In an alternative embodiment G2, the propulsion system of alternate F2 includes the one or more controllers being configured to activate the electric machine when the rotational speed of the output shaft exceeds 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the rotational speed at the intersection point of the power curve and the propeller curve.

[00122] In an alternative embodiment H2, the propulsion system of alternate F2 includes at least one of the one or more controllers being operative to activate the electric machine when the rotational speed of the output shaft approaches zero (e.g., less than 800 rpm, less than 700 rpm, less than 600 rpm, less than 500 rpm, less than 400 rpm, less than 300 rpm, less than 200 rpm, less than 100 rpm, less than 50 rpm) or is zero.

[00123] In an alternative embodiment 12, the propulsion system of any one of alternates A2-E2 include the one or more predetermined threshold values being a loading parameter value for the output shaft. The one or more sensors are configured to monitor and receive loading data for the output shaft. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft in response to the received loading data exceeding the loading parameter value.

[00124] In an alternative embodiment J2, the propulsion system of alternate 12 includes the loading parameter being torque.

[00125] In an alternative embodiment K2, the propulsion system of alternate 12 includes the loading parameter being torque and the threshold loading value for the output shaft being 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, or 95 percent of the maximum rated torque of the internal combustion engine at a respective rotational speed of the output shaft.

[00126] In an alternative embodiment L2, the propulsion system of alternate 12 includes at least one of the one or more controllers being operative to activate the electric machine when the loading parameter value received from the one or more sensors indicates the internal combustion engine is approaching an overload state for a respective rotational speed at which the output shaft is operating. [00127] In an alternative embodiment M2, the propulsion system of any one of alternates A2-E2 include the one or more controllers being associated with a memory storing the propeller curve and a fuel map identifying a zone of peak efficiency for the propeller curve and the internal combustion engine combination. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft when the rotational speed of the output shaft is outside of the zone of efficiency for the propeller.

[00128] In an alternative embodiment N2, the propulsion system of any one of alternates A2-M2 include the electric machine being operative to switch between operating as an electric motor and as a generator.

[00129] In an alternative embodiment 02, the propulsion system of any one of alternates A2-N2 include the output shaft of the internal combustion engine extending through a first end and a second end of the internal combustion engine. The propeller shaft is coupled to the internal combustion engine at the second end of the internal combustion engine. The electric machine includes a second output shaft coupled to a portion of the output shaft extending from the first end of the internal combustion engine.

[00130] In an alternative embodiment P2, the propulsion system of any one of alternates A2-N2 include the output shaft of the internal combustion engine extending through a first end and a second end of the internal combustion engine such that the gearbox and propeller shaft are coupled to the internal combustion engine through the second end of the internal combustion engine. The electric machine includes a second output shaft coupled to a portion of the output shaft at the first end of the internal combustion engine.

[00131] In an alternative embodiment Q2, the propulsion system of any one of alternates A2-P2 include the propeller being an oversized propeller.

[00132] In an alternative embodiment R2, the propulsion system of any one of alternates A2-Q2 include a first clutch mechanism, the first clutch mechanism disposed between the internal combustion engine and the electric machine and operative to engage and to disengage the internal combustion engine from the electric machine.

[00133] In an alternative embodiment S2, the propulsion system of any one of alternates A2-R2 include a second clutch mechanism. The second clutch mechanism is disposed between the gearbox and the propeller shaft.

[00134] In an alternative embodiment T2, the propulsion system of any one of alternates A2-S2 include a gearbox coupled to at least one of the output shaft and the propeller shaft. [00135] In an alternative embodiment U2, the propulsion system of any one of alternates P2 or T2 include a reduction gear configured to be coupled to the propeller shaft. The reduction gear is configured to reduce a rotational speed of the propeller shaft to a rotational speed less than the rotational speed of the output shaft.

[00136] In an alternative embodiment V2, the propulsion system of any one of alternates A2-P2 and R2-U2 include the propeller being a matched propeller.

[00137] In an alternative embodiment W2, the propulsion system of any one of alternates A2-V2 include the reduction gear being is a higher-than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is matched to the reduction gear.

[00138] In an alternative embodiment W2, the propulsion system of any one of alternates A2-V2 include the reduction gear being a higher-than-normal reduction gear matched to a larger-than-normal propeller such that the propeller is oversized with respect to the reduction gear.

[00139] In an alternative embodiment X2, the propulsion system of any one of alternates A2-W2 include the electric machine being further operative as a generator while the internal combustion engine is activated and engaged with the electric machine.

[00140] In an alternative embodiment Y2, the propulsion system of any one of alternates A2-X2 include the electric machine being further operative as a generator while the propeller is rotating and engaged with the electric machine.

[00141] In an alternative embodiment Z2, the propulsion system of any one of alternates A2-Y2 include the internal combustion engine being a gas turbine.

[00142] In an alternative embodiment AA2, the propulsion system of any one of alternates A2-Y2 include the internal combustion engine being a compression-ignition engine.

[00143] In an alternative embodiment AB2, the propulsion system of any one of alternates A2-AA2 include the electric machine being coupled to the propulsion system through a coupling between the electric machine and the internal combustion engine via a crankshaft pulley connected to the output shaft.

[00144] In an alternative embodiment AC2, the propulsion system of any one of alternates A2-AB2 include the electric machine being coupled to the output shaft through a gearbox.

[00145] In an alternative embodiment AD2, the propulsion system of any one of alternates A2-AB2 include the electric machine is directly coupled to the output shaft. [00146] In an alternative embodiment AE2, the propulsion system of any one of alternates A2-AB2 include the electric machine is coupled to the output shaft through one of a belt assembly or a gear assembly.

[00147] In an alternative embodiment AF2, the propulsion system of any one of alternates A2-AB2 include the electric machine being coupled to the propeller shaft through a gearbox.

[00148] In an alternative embodiment AG2, a marine vessel includes any one of the propulsion systems of alternates A2-AF2.

[00149] According to another aspect, a propulsion system for a marine vessel comprises an internal combustion engine with a crankshaft that extends out both ends of the engine including at one end a crankshaft pulley and at the other end an output shaft. The internal combustion engine has a power curve based on a rotational speed of the output shaft. The power curve defines a rated power of the internal combustion engine at any given rotational speed of the output shaft. An electric machine is coupled to the crankshaft pulley end of the engine. A propeller shaft is coupled to the internal combustion engine. A propeller is coupled to the propeller shaft. The propeller has a propeller curve based on the rotational speed of the output shaft. One or more sensors are configured to monitor and receive one of rotational speed data or loading data for the output shaft. One or more controllers are operatively connected to the one or more sensors and the electric machine. The one or more controllers are configured to activate the electric machine to add torque to one of the output shaft or the propeller shaft or the crankshaft in response to one of received rotational speed data or loading data passing one or more predetermined threshold values for the output shaft.

[00150] Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and aspects.