MARINE PROPULSION DEVICE
A marine propulsion device such as an outboard motor includes a submersible electric motor having a propeller connected directly with the drive shaft of the motor. The motor is an efficient brushless motor having symmetrical elliptical coils connected with a stator which generate magnetic flux when current is passed through the coils to rotate a rotor for driving the drive shaft. The motor is arranged in a housing having a nozzle connected with a rear portion thereof which surrounds the propeller to reduce cavitation. Cooling fins are provided on the outer surface of the housing to assist with cooling the motor and a motor controller arranged in the housing.
The present invention relates to a marine propulsion system in the form of an outboard motor. Such motors have been used for many years to propel small vessels on protected bodies of water. The most common types of outboard motors are gas and electric. Internal combustion engines which rely on gas for fuel provide greater horsepower. However, they are noisy and contribute to pollution of the body of water on which the vessel is used. Accordingly, many bodies of water restrict the size of the gas powered motors allowed or eliminate them altogether.
Electric outboard motors are much cleaner and quieter than gas powered motors. They are particularly useful for propelling rowboats and fishing boats to maneuver the boats in shallow water and around submerged obstacles such as fallen trees. The main drawbacks with electric outboard motors are the limitation in horsepower, the amount of current required to operate them, and the heat generated by the motor.
The present invention was developed in order to overcome these and other drawbacks of prior electric outboard motors by providing a submersible motor of greater efficiency with increased output torque.
SUMMARY OF THE INVENTIONThe marine propulsion system according to the invention includes a submersible housing containing a brushless electric motor having a longitudinal drive shaft extending from the housing. An external propeller is connected directly to the drive shaft for rotation by the motor. Preferably, the motor produces a high torque output with reduced energy consumption. It includes a cylindrical stator having a longitudinal axis and defining a chamber in which a rotor is coaxially arranged. The drive shaft is connected with the rotor. A plurality of magnets are connected with the outer surface of the rotor and a plurality of symmetrical coils are connected with the inner surface of the stator. The coils are formed by winding a conductor in an elliptical configuration with the long axis of each coil being parallel with the longitudinal axis of the stator. When current is supplied to the conductors of each coil, the coils produce a magnetic flux which acts on the magnets to cause the rotor to rotate which in turn drives the propeller.
The housing includes a nozzle which extends from the rear and surrounds the propeller to reduce cavitation. In addition, the housing includes a plurality of longitudinal cooling fins arranged in spaced relation about the housing exterior surface to assist with dissipating heat generated in the housing by the motor.
A bracket is provided to connect the marine propulsion system to the transom of a vessel and a shaft is connected between the bracket and the motor. The shaft includes a rudder adjacent to the housing to assist with steering the vessel by pivotal movement of the shaft and housing. A controller for the motor is arranged within the housing and a control panel is connected with the bracket for use by the operator to control the speed and direction of the motor and the orientation of the shaft.
Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which:
The marine propulsion system according to the invention will first be described with reference to
The housing has a curved nose portion 18 at the forward end in the direction of travel so that the housing passes smoothly through the water and sheds debris. Rearwardly, the housing includes a nozzle 20 which preferably has a truncated conical configuration and surrounds the propeller as shown in
The housing is formed of any durable water proof material such as metal or synthetic plastic and is shown in detail in
The motor 10 is a brushless electric motor. Referring now to
Each coil is formed of a conductor 34 wound with a jig into an elliptical configuration. The conductor is preferably formed of copper and preferably has a rectangular cross-sectional configuration. The conductor is wound so that the flat portion of the conductor is contiguous. The wound coils are pressed into an annular configuration to fit within the stator 26 with which each coil is connected in a conventional manner. The ends of the conductors of each winding are connected with a current supply so that as current runs through each coil, magnetic flux is generated. The symmetrical coils increase the efficiency of the motor by allowing more copper to be present in each coil. The greater copper density and symmetrical shape of the coils increase the magnetic flux generated by the coils. The coils are operated pairs to produce magnetic fluxes of different direction. The interaction of the magnetic flux from the coils and the magnetic fields from the permanent magnets on the rotor causes the rotor to rotate about its axis, thereby rotating the shaft 14.
The solid rectangular shaped conductor increases the density of the coils and thus increases the amount of conductive material in the space provided for the coils. The additional density allows the radial axis of the motor to be reduced and improves the overall efficiency of the design. The torque is increased and the motor diameter is reduced. The reduction in diameter also increases the heat transferability and thus increases the longevity of the magnets and reduces wear on the motor.
Referring once again to
The control panel can be operated manually in a conventional manner or via a remote control cable 34. In the exemplary embodiment shown in
The marine propulsion system according to the invention has minimal impact on the environment because it produces no exhaust and minimal noise. Moreover, because the motor is submersed in the water adjacent to the propeller, any noise or heat generated by the motor is dispersed in the water. The heat dissipation from the motor and controller increases the efficiency and longevity of these components.
While the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.
Claims
1. A marine propulsion device, comprising
- (a) a submersible housing containing a brushless electric motor having a longitudinal drive shaft extending from said housing; and
- (b) a propeller connected with said drive shaft and being driven for rotation by said motor.
2. A marine propulsion device as defined in claim 1, wherein said motor includes
- (a) a cylindrical stator having a longitudinal axis and defining a chamber;
- (b) a rotor arranged within said stator chamber coaxial with said stator, said drive shaft being connected with said rotor;
- (c) a plurality of magnets connected with an outer surface of said rotor; and
- (d) a plurality of symmetrical coils connected with an inner surface of said stator, each of said coils comprising a conductor wound in an elliptical configuration, a long axis of each coil being parallel with the stator longitudinal axis, whereby when current is supplied to said coils, said coils produce a magnetic flux which acts on said magnets to cause said rotor to rotate with respect to said stator.
3. A marine propulsion device as defined in claim 2, wherein said housing includes a nozzle extending rearwardly therefrom, said propeller being arranged within said nozzle, whereby said nozzle reduces cavitation resulting from rotation of said propeller.
4. A marine propulsion device as defined in claim 3, wherein said nozzle has a truncated conical configuration.
5. A marine propulsion device as defined in claim 3, wherein said housing includes a plurality of longitudinal cooling fins arranged in spaced relation about the housing exterior surface.
6. A marine propulsion device as defined in claim 5, and further comprising a controller arranged within said housing and connected with said motor.
7. A marine propulsion device as defined in claim 2, and further comprising means for connecting said housing with a vessel.
8. A marine propulsion device as defined in claim 7, wherein said connecting means comprises a bracket connected with a vessel transom and a shaft connected between said bracket and said housing.
9. A marine propulsion device as defined in claim 8, and further comprising a rudder connected with said shaft adjacent to said housing.
10. A marine propulsion device as defined in claim 9, and further comprising a control system connected with said bracket.
11. A marine propulsion device as defined in claim 10, wherein said control system includes means for rotating said shaft relative to said bracket to steer the vessel and means for supplying electric current to said motor.
Type: Application
Filed: May 20, 2008
Publication Date: Nov 27, 2008
Inventor: Sean Scott (Crownsville, MD)
Application Number: 12/123,661
International Classification: B63H 21/17 (20060101); B63H 20/08 (20060101); B63H 21/21 (20060101); B63H 25/06 (20060101); B63H 1/18 (20060101);