Integrated Brushless Direct Current Motor and Lift Pump

Abstract

A lift pump having a longitudinal axis and comprising first and second housing components defining an operational volume, a brushless direct current motor assembly, and a pump assembly disposed in said volume. The brushless direct current motor assembly has a motor axis eccentric with the longitudinal axis, a rotor, and a stator disposed diametrically inwardly of the rotor. The rotor further comprises a plurality of magnetic poles of alternating opposite polarity. The pump assembly has a pump annulus and a pump element. The pump annulus is disposed intermediate said first and second housing components and coaxial with the longitudinal axis. The pump element is coaxial with said motor axis, and comprises a generally cylindrical hub defining a motor assembly cavity sized to diametrically receive said motor assembly.

What is claimed is: 
     
         1 . A lift pump having a longitudinal axis comprising:
 first and second housing components defining an inlet, an outlet, and an operational volume;   a brushless direct current motor assembly having a motor axis eccentric with the longitudinal axis, a rotor comprising a plurality of magnetic poles arranged in alternating opposite polarity, and a stator comprising a number of selectively energizeable coils disposed diametrically inwardly of said rotor annulus; and   a pump assembly having an inlet and outlet including a pump annulus coaxial with the longitudinal axis, a pump element coaxial with said motor axis and having a generally cylindrical hub defining a motor assembly cavity having a diametral width w and an axial depth d, wherein said motor assembly cavity is sized to diametrically receive said motor assembly so that said pump element rotates with said rotor.   
     
     
         2 . The lift pump of  claim 1 , wherein said plurality of magnetic poles comprise a plurality of individual magnets of alternating opposite polarity affixed to an annulus, and said annulus is secured diametrically within said motor assembly cavity. 
     
     
         3 . The lift pump of  claim 1 , wherein said plurality of magnetic poles comprise a single multipole magnet having alternating opposite poles. 
     
     
         4 . The lift pump of  claim 1 , wherein said plurality of magnetic poles are integral with said hub. 
     
     
         5 . The lift pump of  claim 1 , wherein said pump element is a gerotor pump having an inner and outer rotor, said inner rotor having said pump annulus. 
     
     
         6 . The lift pump of  claim 1 , wherein said pump element is a roller vane pump. 
     
     
         7 . The lift pump of  claim 6 , wherein rollers of said pump comprise a ferrous material. 
     
     
         8 . The lift pump of  claim 6 , wherein rollers of said pump comprise a non-ferrous material. 
     
     
         9 . The lift pump of  claim 1 , wherein an axial height of said stator coils and said magnetic poles is larger than said depth d of said motor assembly cavity.