EP1352435A4

EP1352435A4 - Electrical power generation

Info

Publication number: EP1352435A4
Application number: EP01988379A
Authority: EP
Inventors: John H Westerbeke Jr
Original assignee: Westerbeke Corp
Current assignee: Westerbeke Corp
Priority date: 2000-11-07
Filing date: 2001-11-07
Publication date: 2004-12-01
Also published as: JP2004515200A; WO2002045189A2; EP1352435A2; AU2002241692A1; WO2002045189A3

Abstract

An on-board marine electrical power generator (14) containing a conventional four-stroke, water-cooled outboard motor engine (50) coupled to an alternator (52) upon a transportable frame (44) suitable for mounting on-board a boat. In one embodiment, the crankshaft (60) of the engine extends vertically and is coupled to a vertically oriented rotor (72) of the alternator, either directly or laterally spaced from the engine shaft. In another embodiment, the engine is modified for operation with its crankshaft extending horizontally. The physical size of the overall package is advantageously within a range suitable for installation on pleasure boats.

Description

ELECTRICAL POWER GENERATION

TECHNICAL FIELD

This invention relates to electrical power generation, and more particularly to fuel-powered, on-board marine generators.

BACKGROUND

There are many commercially available generators, some of which are designed especially for use on board boats. A typical marine engine-generator set has a water- cooled engine with its crankshaft coupled to the rotor of an electrical generator, with the crankshaft and rotor collinear and horizontal as mounted in operation. Injecting seawater directly into the exhaust stream cools the engine exhaust.

On many smaller craft, electrical power generation is desirable, but space is limited. It can be particularly difficult below deck, for example, to accommodate the height of commercially available power generators. Market economics generally limit marine power generator manufacturers to the use of engines and generator components otherwise available for other, higher volume applications. A new approach to producing electrical power is needed to satisfy the market need for compact, reliable power generation.

SUMMARY

I have realized that a new configuration of engine and generator components can produce an electrical power generation system suitable to meet the needs of owners of smaller watercraft, and those requiring lower output ratings.

In one aspect of my invention, an on-board marine electrical power generator contains a conventional four-stroke, water-cooled outboard motor engine coupled to an alternator upon a transportable frame suitable for mounting on-board a boat (e.g., on a horizontal surface below deck). In some embodiments, the outboard motor engine is modified to enable its reliable operation with its crankshaft extending horizontally. In some other embodiments, the outboard engine motor shaft extends vertically and is directly coupled to an alternator rotor. Another aspect of my invention features a fuel-powered engine with a vertically oriented shaft coupled to a vertically oriented rotor of an electrical generator laterally spaced from the engine shaft, such that the engine and generator are disposed in side-by- side relation. This configuration enables the use of commercially available, water-cooled engines and engine components from vertically-shafted, outboard marine motors, for example, while keeping the height of the overall package within a range suitable for installation on pleasure boats.

The engine preferably operates on a four-stroke, gasoline (Otto) cycle, and has an exhaust elbow adapted to mix a flow of water into the streaming exhaust to cool the exhaust before it is discharged. Four-stroke engines are particularly preferred for their ability to operate under elevated exhaust back pressures, such as are required to push water-injected exhaust streams through backwash-inhibiting exhaust risers.

The engine and generator are preferably mounted to a portable frame that may also support power-conditioning circuits for the alternator. The output shaft of the engine may be coupled to the rotor shaft of the generator by belted pulleys, for quiet power transmission at a desired speed ratio.

The alternator or generator may be of several types known in the art, but for some applications a variable speed, permanent magnet alternator is preferred. Such alternators are commonly used in generating electrical power from wind-driven turbines, for example, and can be equipped with power conditioning circuitry to provide a stable output frequency over a wide range of input speeds. An advantage of variable speed operation is that the engine can be configured to change speeds in response to load, to maintain an optimum operating efficiency and to enable the use of advantageously small, less powerful engines. By "rotor" I mean the rotating portion of the alternator, whether carrying electrical windings as an armature, or carrying magnets.

In some embodiments, the permanent magnet alternator is coupled to the engine to run at a relatively constant, "synchronous" speed (e.g., 1800 RPM), to produce a desired output frequency. Such a configuration is appropriate for applications that will accommodate some variation in output voltage over a range of operational loads and temperatures. One advantage of this configuration is that it employs a much simpler alternator architecture than that of a wound generator stator with exciter circuits, for example, without the added expense of solid state frequency generation circuitry. According to another aspect of the invention, a method of producing electrical power on-board a boat is provided. The method includes the steps of attaching a crankshaft of an outboard motor engine to an electrical generator, mounting the engine and generator on-board a boat, and running the engine to produce electrical power, and directing electrical power from the generator to a remote electrical load, such as an electrical appliance or on-board power grid, to perform useful work.

This invention can provide cost-effective electrical power generators of a physical size and power rating particularly needed by some boat owners, particularly those with moderate to low power requirements and who prefer a system that can be permanently mounted below deck and out of sight, rather than mounted outboard, for example, where they would be exposed to direct salt spray and less secure from theft.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

Figs. 1 and 2 illustrate an electrical power generator installed on board a boat. Fig. 3 is a perspective view of the electrical power generator. Fig. 4 is a schematic cross-sectional view of the generator, showing the side-by- side arrangement of vertically oriented engine and alternator. Fig. 5 is a schematic cross-sectional view of a second embodiment of the generator, showing an in-line, vertical coupling of engine and alternator.

Fig. 6 is a schematic cross-sectional view of a third embodiment of the generator, showing an in-line, horizontal coupling of engine and alternator. Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to Fig. 1, a boat 10 is equipped with an inboard, gasoline-powered engine 12 and an electric generator 14, with both the engine and generator mounted below deck and accessible through a hatch as shown. Engine 12 and generator 14 may be fed from the same fuel tank (not shown), and exhaust through respective transom bulkhead exhaust ports 16 and 18.

As shown in Fig. 2, the generator 14 is mounted upon a platform 20 secured to the boat hull below the rear deck 22. Platform 20 has appropriate mounting points (such as bolting bosses, tie-down features, or vibration-isolating mounting pads; not illustrated) for securing the generator to below-deck structure. Cooling water is suctioned from a seacock 24 through an inlet hose 26, for injection into the exhaust stream of the generator engine as discussed in more detail below. Cooled exhaust gasses are routed through the transom 28 through an exhaust pipe 30 that rises to above the water line 32. Generator 14 is controlled from a remote controller (e.g., switch panel 34 in Fig. 1), receiving input signals through electrical signal line 36. Generated electrical power is routed to onboard electrical loads (e.g., appliances, air conditioners and such, not shown) via output cable 38. The generator is powered by liquid fuel (e.g., gasoline or diesel fuel) from tank 40, and a typical marine battery 41 provides 12VDC power.

Referring now to Fig. 3, generator 14 forms a compact, readily mountable, practically stand-alone unit. The generator may be equipped with a sound-deadening enclosure 42, as shown, or may alternately be mounted on a rigid frame 44 with open sides and top for increased air circulation. Details of a suitable enclosure 42 can be found in U.S. Patent No. 5,929,394, the contents of which are incorporated by reference as if entirely set forth. Preferably the height "H" of the entire unit is less than about 15 inches or 38 centimeters (more preferably, less than about 12 inches or 30 centimeters), and occupies a footprint with a length "L" of less than about 25 inches or 63 centimeters (more preferably, less than about 20 inches or 50 centimeters), and a width "W" of less than about 15 inches or 38 centimeters (more preferably, less than about 12 inches or 30 centimeters). The weight of a 3 to 4 kilowatt unit is only about 120 pounds. Louvers 46 may be provided through enclosure 42 for increased air circulation, and the enclosure may optionally be equipped with output power receptacles 48, as shown.

Turning to Fig. 4, generator 14 contains a engine 50 coupled to an electric alternator 52 through a flexible timing or synchronous belt 54 and respective pulleys 56 and 58. Belt 54 is of the type commonly used to drive camshafts in automotive engines, for example. Pulley 56 is mounted for rotation with one end of the vertical crankshaft 60 of engine 50, with the other end of crankshaft 60 turning a positive displacement pump 62 for suctioning seawater from inlet hose 26 and pumping the seawater out through hose 64 into engine exhaust elbow 66 where it is injected into the exhaust stream of the engine to cool the exhaust before it enters muffler 68.

In a presently preferred and commercially advantageous embodiment, engine 50 is a four-stroke gasoline engine designed for use in a vertical shaft configuration in outboard marine motors, and is therefore appropriate for marine environmental conditions. Such engines are typically already equipped with exhaust cooling elbow 66 and seawater pump 62, and are therefore readily adapted for use in generator 14 by mounting the engine block to the generator frame, and supporting the lower end of crankshaft 60 in a frame-mounted bearing block 70. For a generator 14 rated at about 3 to 4 kilowatts, a two cylinder, 15 horsepower outboard engine motor is suitable. For a generator 14 rated at only about 1-2 kilowatts, a one cylinder, 6 horsepower outboard engine motor is sufficient. As emissions regulations continue to encourage the replacement of two-stroke outboard motor engines with four-stroke versions, the cost and availability of appropriate engines suitable for use in my generator should continue to improve. The overall height of the generator is kept advantageously low by arranging alternator 52 to occupy the same vertical space as engine 50, with their shafts running parallel, spaced apart and vertical. The rotor shaft 72 of alternator 52 is mounted upon two spaced apart bearings (not shown) within the alternator housing, such that pulley 58 is mounted in cantilevered fashion at the end of the rotor shaft. In this example, alternator 52 is a permanent magnet alternator designed to be run at variable speed. Variable speed PM alternators are also known to be employed in wind machines and in some modern automotive systems, such as in hybrid vehicles.

Engine 50 may include a speed regulator to maintain the speed of the engine as close as possible to a speed selected with respect to the drive ratio to cause a synchronous alternator speed for producing a desired output frequency. For example, the engine may be speed-regulated about a 1500 RPM set point to cause a four-pole alternator to rotate at 1800 RPM for producing a 60 hertz output frequency. Such embodiments may require an increase in engine capacity over variable speed arrangements in order to maintain the speed and voltage within acceptable ranges over operational loads and temperatures, but advantageously do not require elaborate power conditioning circuitry.

Alternatively, generator controller 74 may include appropriate power- conditioning circuitry as is employed in variable speed, permanent magnet motor drivers, for accepting a wide range of raw power frequencies from alternator 52 and producing a desired output frequency. The cost of such circuitry will in some cases be sufficiently offset by the corresponding use of a smaller (lighter, less expensive) engine configured to operate at higher speeds in response to high load.

Other preferred features and aspects of controller 74 are disclosed in presently pending U.S. serial number 09/368,200, filed August 4, 1999 and incorporated herein by reference as if entirely set forth, and in corresponding PCT application US00/21141, published August 3, 2000 as WO 01/11765.

Referring to the embodiment of Fig. 5, generator 14' contains a vertically-shafted, four-stroke outboard engine motor 50 in which the standard flywheel at the end of its crankshaft has been replaced with a cup-shaped rotor 76 of a pancake profile, permanent magnet alternator 78. Rotor 76 turns with the motor crankshaft and carries an arrangement of permanent magnets 80 attached to its inner circumferential surface. The weight and position of magnets 80 are selected to balance firing impulses and radial accelerations of the motor and its rotating components. Packaged within rotating rotor 76 is a stationary, wound stator 82 responsive to the moving magnetic fields generated by rotor 76. This type of alternator can be constructed to have a very low profile or axial length, such that, replacing the flywheel of the motor, the motor-alternator combination can add only few inches to the height of the motor itself. Pump 62 may be mounted on the other end of the crankshaft, as shown, or can be electrically powered and mounted remotely for even lower package height.

The two above-described embodiments share the practical advantage of enabling the use of virtually unmodified outboard motor engines, which are produced in high quantity and therefore very reasonably priced. However, it is also possible to modify such engines for use in horizontally coupled configurations, as shown in Fig. 6. In generator 14", engine 50' is mounted with its crankshaft 60 extending horizontally and coupled through a flexible coupling 82 to the rotor shaft of alternator 52. Because engine 50' was designed to operate with shaft 60 vertical, a few key modifications are made to ensure proper operation and reliability. First, engine 50' is equipped with a bottom oil sump 84 with an appropriate internal oil pickup for siphoning lubricating oil up into the engine. For some outboard motor engines, other modifications may be required to keep oil from pooling on shaft seals, or collecting in internal passages and not returning properly to the sump. Second, carburetor 86 has been repositioned to maintain a vertical throat orientation as designed. In some cases, this entails installing a custom intake manifold designed for this purpose. Other necessary modifications will also be recognized and understood by those of ordinary skill, depending on the specific outboard motor engine selected for any given application.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the pulleys and belt of the embodiment of Fig. 4 can be arranged above the engine and alternator, with the seawater pump mounted below. Accordingly, other embodiments are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. An on-board marine electrical power generator comprising a four-stroke, water-cooled engine (50) with a vertically-oriented drive shaft (60); an alternator (52) with a vertically oriented rotor (72) coupled for rotation with the engine drive shaft to produce electricity and laterally spaced from the engine shaft; and a transportable frame upon which the engine and alternator are mounted in side- by-side relation.

2. The generator of any of the above claims wherein the engine (50) is adapted to operate on a four-stroke, gasoline cycle.

3. The generator of any of the above claims wherein the engine (50) has an exhaust elbow (66) adapted to mix a flow of water into streaming exhaust to cool the exhaust before it is discharged.

4. The generator of any of the above claims wherein the shaft (60) of the engine (50) is coupled to the rotor (72) of the alternator (52) by belted pulleys (56,58).

5. The generator of any of the above claims mounted inside a boat hull, with an exhaust system of the engine including an exhaust riser (30) extending to above a water line of the hull.

6. The generator of any of the above claims wherein the exhaust system extends through a transom bulkhead exhaust port (18).

7. The generator of any of the above claims mounted below a deck of the boat.

8. The generator of any of the above claims wherein the alternator (52) comprises a variable speed, permanent magnet alternator, and wherein the engine (50) is configured to change speeds in response to load.

9. The generator of any of the above claims wherein the alternator (52) is coupled to the engine (50) to run at a synchronous speed.

10. The generator of any of the above claims wherein the platform (44) defines mounting points for securing the generator (14) to below-deck structure.

11. The generator of any of the above claims further comprising an enclosure (42) surrounding the engine and alternator.

12. The generator of claim 11 wherein the enclosure (42) is equipped with output power receptacles (48).

13. The generator of any of the above claims having an overall height (H) of less than about 15 inches (38 centimeters), preferably less than about 12 inches (30 centimeters).

14. The generator of any of the above claims occupying a footprint with a length (L) of less than about 25 inches (63 centimeters), preferably less than about 20 inches (50 centimeters), and a width (W) of less than about 15 inches (38 centimeters), preferably less than about 12 inches (30 centimeters).

15. The generator of any of the above claims wherein the drive shaft (50) also turns a seawater pump (62).

16. The generator of any of the above claims wherein the seawater pump (62) is directly coupled to the drive shaft (50) at an opposite end of the engine (50) than a pulley (56) driving the alternator (52).

17. The generator of any of the above claims wherein the engine (52) comprises an engine designed for use in a vertical shaft configuration in outboard marine motors.

18. An on-board marine electrical power generator comprising a four-stroke, water-cooled engine (50) with a vertically-oriented drive shaft (60); a permanent magnet alternator (78) with a cup-shaped rotor (76) mounted at one end of the engine drive shaft to produce electricity; and a transportable frame upon which the engine and alternator are mounted in side- by-side relation, (see Fig. 5)

19. The generator of claim 18 wherein rotor (76) carries an arrangement of permanent magnets (80) attached to an inner circumferential surface of the rotor.

20. The generator of claim 18 or claim 19 wherein weight and position of magnets (80) are selected to balance firing impulses and radial accelerations of the engine (50) and its rotating components.

21. The generator of any of claims 18 through 20 wherein alternator (78) includes a stationary, wound stator (82) responsive to the moving magnetic fields generated by rotor (76) and packaged within rotating rotor (76).

22. The generator of any of claims 18 through 21 further comprising a seawater pump (62) mounted on another end of the engine drive shaft (60).

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23. The generator of any of claims 18 through 22 wherein the engine (52) comprises an engine designed for use in a vertical shaft configuration in outboard marine motors.

24. A method of producing electrical power on-board a boat, the method comprising attaching a crankshaft (60) of an outboard motor engine (50) to an electrical generator (52); mounting the engine and generator within a hull of a boat; running the engine to produce electrical power; and directing electrical power from the generator to a remote electrical load to perform useful work.

25. The method of claim 24 further comprising enclosing both the engine (50) and generator (52) in an enclosure (42).

26. The method of claim 24 or claim 25 wherein the engine (50) and generator (52) are mounted below deck.

27. The method of any of claims 24 through 26 wherein the engine (50) and generator (52) are mounted in side-by-side relation.

28. The method of any of claims 24 through 26 wherein the generator (52) is mounted directly to the crankshaft (60) at one end of the engine.