Electric propulsion drive for watercraft

Abstract

Devices and methods are disclosed related to electric propulsion drives for watercraft. In some embodiments, an electric drive includes an active cooling loop facilitated by a rotating electric motor pumping a coolant through a mast and a housing of the electric drive. The mast can be provided with a separation wall to separate and guide streams of cooler and hotter coolant. The motor and an ESC can be cooled by the coolant. In certain embodiments, the electric drive includes a rotor jacket that substantially surrounds an external rotor of an electric motor; the rotor jacket substantially reduces unwanted eddy currents, and thereby allows the use a large motor and a housing with a smaller external diameter, which reduces hydrodynamic drag. In one embodiment, the external rotor is coupled directly, without intermediary gearing, to a propeller.

What is claimed is: 
     
         1 . A propulsion drive comprising:
 a housing;   a mast coupled to the housing;   wherein the housing is configured to be in fluid communication with the mast to allow inflow of cooled coolant from the housing into the mast and outflow of heated coolant from the mast back into the housing;   a separation wall within the mast, the separation wall configured to provide a separation between the cooled coolant and the heated coolant; and   a motor located within the housing, the motor configured whereby a rotation of the motor causes the coolant to flow in a cooling loop from the housing into the mast and from the mast back into the housing.   
     
     
         2 . The propulsion drive of  claim 1 , further comprising an ESC, wherein the ESC is located in the mast. 
     
     
         3 . The propulsion drive of  claim 2 , wherein the ESC is located at a distal end of the mast away from the housing. 
     
     
         4 . The propulsion drive of  claim 2 , wherein the motor and the ESC are configured to be submerged in the coolant. 
     
     
         5 . The propulsion drive of  claim 1 , wherein the motor is an external rotor electric motor. 
     
     
         6 . The propulsion drive of  claim 1 , further comprising a rotor jacket substantially enclosing the motor. 
     
     
         7 . A propulsion drive comprising:
 a housing;   a motor located within the housing, the motor comprising an external rotor;   a rotor jacket substantially surrounding the external rotor; and   wherein the rotor jacket is configured to reduce an eddy current generated by the motor.   
     
     
         8 . The propulsion drive of  claim 7 , further comprising a propeller shaft coupled to the motor and to a propeller, wherein the motor is coupled to the propeller directly via the shaft without intermediary gearing. 
     
     
         9 . The propulsion drive of  claim 7 , wherein the rotor jacket comprises surface textures and/or structures to facilitate the pumping of a coolant in and out of the housing. 
     
     
         10 . The propulsion drive of  claim 6 , further comprising a mast configured to be in fluid communication with the housing. 
     
     
         11 . The propulsion drive of  claim 10 , wherein the mast comprises a separation wall configured to create a cooled coolant passage and a heated coolant passage within the mast. 
     
     
         12 . A method of manufacturing an outboard electric motor, the method comprising:
 providing an external rotor electric motor;   providing a rotor jacket that substantially encloses the external rotor electric motor; and   providing a housing sized and shaped to geometric tolerances around the rotor jacket to minimize an outside diameter of the housing.   
     
     
         13 . The method of  claim 12 , further comprising providing a hollow mast configured to be in fluid communication with the housing. 
     
     
         14 . The method of  claim 13 , wherein providing a hollow mast further comprises providing a separation wall within the mast to provide a first compartment for a cooled coolant and a second compartment for a heated coolant. 
     
     
         15 . The method of  claim 14 , further comprising providing an ESC within the hollow mast. 
     
     
         16 . The method of  claim 12 , further comprising providing a propeller and a propeller shaft, and directly coupling the external rotor electric motor to the propeller via the propeller shaft. 
     
     
         17 . The method of  claim 13 , wherein providing a hollow mast further comprises providing a sight glass indicator on the hollow mast. 
     
     
         18 . The method of  claim 13 , further comprising providing an ESC external to the hollow mast and configured to be in thermal communication with the hollow mast whereby a flow of coolant within the mast cools the ESC.