Electric motor having fluid circulation system and methods for cooling an electric motor

Abstract

An electric motor having a housing, a stator mounted in the housing, and a rotor mounted in the housing for rotation relative to the stator about a central axis. A plurality of fluid flow passages extend through the rotor between opposite ends. An electro-magnetic drive system is adapted for driving rotation of the rotor relative to the stator. A fluid circulation system is in fluid communication with the fluid flow passages for providing fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages. The rotor and components of the fluid circulation system can be assembled to make a rotor assembly

1 . An electric motor comprising:
 a housing;   a stator mounted in the housing;   a rotor mounted in the housing for rotation relative to the stator about a central axis, the rotor having first and second opposite ends and a plurality of fluid flow passages extending through the rotor between the first and second ends;   an electro-magnetic drive system operatively connected to the rotor for driving rotation of the rotor relative to the stator; and   a fluid circulation system in fluid communication with the fluid flow passages for providing fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages, wherein the fluid circulation system comprises at least one impeller mounted in the housing for rotation relative to the stator, the impeller having a peripheral edge margin, an inlet positioned radially inward from the peripheral edge margin and in alignment with an opening at the end of at least one of the fluid flow passages so the impeller inlet is positioned to receive fluid as it exits the opening, and an outlet positioned radially outward from the inlet, the impeller being adapted to produce at least some of said fluid flow by propelling said fluid radially outward from the inlet to the outlet when the impeller is rotated relative to the stator.   
     
     
         2 . An electric motor as set forth in  claim 1  wherein the stator and the rotor are totally enclosed by the housing. 
     
     
         3 . An electric motor as set forth in  claim 1  wherein said fluid flow passages are substantially parallel to said central axis. 
     
     
         4 . An electric motor as set forth in  claim 1  wherein said fluid flow passages comprise helical fluid flow passages. 
     
     
         5 . An electric motor as set forth in  claim 1  wherein said flow includes fluid flow from the first end of the rotor to the second end of the rotor through multiple passages of the plurality of fluid flow passages and fluid flow from the second end to the first end through multiple other passages of the plurality of fluid flow passages. 
     
     
         6 . An electric motor as set forth in  claim 5  wherein the impeller inlet is positioned to receive fluid as it exits multiple passages of the plurality of fluid flow passages. 
     
     
         7 . An electric motor as set forth in  claim 5  wherein said plurality of fluid flow passages are spaced angularly from one another about said central axis. 
     
     
         8 . An electric motor as set forth in  claim 1  wherein the housing and stator are substantially devoid of fluid flow passages in fluid communication with fluid from the fluid circulation system. 
     
     
         9 . An electric motor as set forth in  claim 1  wherein the impeller is connected to the rotor so that rotation of the rotor by the electromagnetic drive system drives the impeller to rotate relative to the stator. 
     
     
         10 . An electric motor as set forth in  claim 9  wherein the impeller is fixedly secured to the rotor. 
     
     
         11 . An electric motor as set forth in  claim 1  wherein the rotor includes a plurality of openings at each of the first and second ends of the rotor, each of said fluid flow passages extending between at least one of said openings at the first end and at least one of said openings at the second end. 
     
     
         12 . An electric motor as set forth in  claim 1  wherein said at least one impeller is a first impeller and said at least one of the fluid flow passages is first fluid flow passage, the fluid circulation system further comprising a second impeller mounted in the housing for rotation relative to the stator at an opposite end of the rotor from the first impeller, the second impeller having a peripheral edge margin, an inlet positioned radially inward from the peripheral edge margin and in alignment with an opening at the end of a second one of the fluid flow passages so fluid enters the second impeller inlet as it exits the opening of the second fluid flow passage, and an outlet positioned radially outward from the inlet, the second impeller being adapted to propel said fluid radially outward from the inlet to the outlet when the impeller is rotated relative to the stator. 
     
     
         13 . An electric motor comprising:
 a housing;   a stator mounted in the housing;   a rotor mounted in the housing for rotation relative to the stator about a central axis, the rotor having first and second opposite ends and a plurality of fluid flow passages extending through the rotor between the first and second ends;   an electro-magnetic drive system operatively connected to the rotor for driving rotation of the rotor relative to the stator; and   a fluid circulation system in fluid communication with the fluid flow passages for providing fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages,   wherein the housing and stator are substantially devoid of fluid flow passages that communicate with the with the fluid circulated by the fluid circulation system   
     
     
         14 . An electric motor as set forth in  claim 13  wherein the stator and the rotor are totally enclosed by the housing. 
     
     
         15 . An electric motor as set forth in  claim 13  wherein said fluid flow passages are substantially parallel to said central axis. 
     
     
         16 . An electric motor as set forth in  claim 13  wherein said fluid flow passages comprise helical fluid flow passages. 
     
     
         17 . An electric motor as set forth in  claim 1  wherein the fluid circulation system comprises at least one impeller mounted in the housing for rotation relative to the stator, the impeller having a peripheral edge margin, an inlet positioned radially inward from the peripheral edge margin, and an outlet positioned radially outward from the inlet, the impeller being adapted to produce at least some of said fluid flow by propelling said fluid radially outward from the inlet to the outlet when the impeller is rotated relative to the stator. 
     
     
         18 . A method of cooling an electric motor comprising a housing, a stator in the housing, a rotor having first and second opposite ends mounted in the housing for rotation relative to the stator, and an electro-magnetic drive system adapted to drive rotation of the rotor relative to the stator, the method comprising:
 pumping air from the first end of the rotor through a first fluid flow passage through the rotor to the second end of the rotor; and   pumping air from the second end of the rotor through a second fluid flow passage in the rotor to the first end of the rotor.   
     
     
         19 . A method as set forth in  claim 18  wherein the air is totally enclosed in the housing. 
     
     
         20 . A method as set forth in  claim 18  wherein pumping air from the first end of the rotor to the second end of the rotor comprises drawing air into the first end of the rotor from a free space in the housing at the first end of the rotor and wherein pumping air from the second end of the rotor to the first end of the rotor comprises drawing air into the second end of the rotor from a free space in the housing at the second end of the rotor.