Spring regulated variable flow electric water pump

Abstract

An electric water pump having a motor with an axially moveable rotor unit. A rotary pump member is fixed for axial movement with the rotor unit to vary its position within a pump chamber so as to vary the flow rate through the pump chamber.

1 . A variable flow electric water pump for use in an engine coolant system of a motor vehicle, the electric water pump comprising:
 a pump housing defining a fluid chamber and a motor chamber, said fluid chamber including a fluid inlet and a discharge outlet for providing flow of a coolant through said fluid chamber;   an electric motor disposed within said motor chamber of said pump housing and including a stationary stator assembly and a rotor unit having a rotor shaft supported for rotation about a longitudinal axis and extending into said fluid chamber;   a pump member fixed to said rotor shaft for rotation in said fluid chamber and operable to pump coolant from said fluid inlet to said discharge outlet; and   a biasing arrangement for normally locating said rotor unit in a first position that is axially offset relative to said stator assembly for locating said pump member in a retracted position within said fluid chamber to provide a low flow characteristic between said fluid inlet and said discharge outlet when said pump member is rotatably driven by said rotor shaft at a low rotor speed;   wherein rotation of said impeller at a high impeller speed causes said rotor unit to move into a second position axially aligned with said stator assembly and causes said pump member to move into an extended position within said fluid chamber to provide a high flow characteristic between said fluid inlet and said discharge outlet.   
     
     
         2 . The electric water pump of  claim 1 , wherein said biasing arrangement is a mechanical biasing arrangement including a biasing member configured to exert a preload on said rotor unit. 
     
     
         3 . The electric water pump of  claim 2 , wherein said biasing member is a coil spring disposed between a portion of said pump housing and said rotor unit. 
     
     
         4 . The electric water pump of  claim 1 , wherein said biasing arrangement is a magnetic biasing arrangement including a plurality of magnets extending axially outwardly from said rotor unit and operable to align the center of a magnetic field associated with said rotor unit with the center of a magnetic field associated with said stator assembly for locating said rotor unit in its first position. 
     
     
         5 . The electric water pump of  claim 1 , wherein said rotor shaft is axially moveable relative to said pump housing and has a first end slideably and rotatably supported by a first guide bushing and a second end slideably and rotatably supported by a second guide bushing. 
     
     
         6 . The electric water pump of  claim 1 , wherein said pump housing includes an interface between said fluid inlet and said fluid chamber defining a flange surface, wherein said pump member is an impeller having an outer rim surface aligned with said flange surface of said pump housing, wherein a large clearance gap is established between said outer rim surface of said impeller and said flange surface of said pump housing when said impeller is located in its retracted position, and wherein said large clearance gap is configured to decrease the coolant flow rate between said fluid inlet and said discharge outlet. 
     
     
         7 . The electric water pump of  claim 6 , wherein a small clearance gap is established between said flange surface of said pump housing and said rim surface of said impeller when said impeller is located in its extended position, and wherein said small clearance gap is configured to increase the coolant flow rate between said fluid inlet and said discharge outlet. 
     
     
         8 . The electric water pump of  claim 7 , wherein a pressure differential established across said impeller in response to increasing impeller speed is operable to cause said impeller to move from its retracted position into its extended position, and wherein such axial movement of said impeller causes concurrent axial movement of said rotor unit relative to said stator assembly from its first position into its second position. 
     
     
         9 . The electric water pump of  claim 1 , wherein a pressure differential established across said pump member in response to increasing rotor unit speed is operable to cause said pump member to move from its retracted position into its extended position, and wherein such axial movement of said pump member causes concurrent axial movement of said rotor unit relative to said stator assembly from its first position into its second position. 
     
     
         10 . A variable flow electric water pump for pumping a coolant in an engine coolant system of a motor vehicle, comprising:
 a pump housing defining a fluid chamber and a motor chamber, said fluid chamber including a fluid inlet, a discharge outlet and a pumping cavity providing fluid communication between said fluid inlet and said discharge outlet;   an electric motor disposed in said motor chamber of said pump housing and including a sleeve delineating said motor chamber into a stator cavity and a rotor cavity, a stationary stator assembly located in said stator cavity, and a rotor unit located in said rotor cavity and being supported therein for rotation about a longitudinal axis for axial translation along said longitudinal axis;   an impeller located in said pumping cavity and fixed for rotation and axial translation with said rotor unit;   a housing mechanism disposed between said rotor unit and said pump housing and configured for normally biasing said rotor unit toward a first axial position relative to said stator assembly which locates said impeller in a retracted position within said pumping cavity to establish a low flow characteristic for the coolant supplied from said fluid inlet to said discharge outlet in response to said impeller being driven by said rotor unit at a low impellor speed;   wherein rotation of said impeller at a high impellor speed counteracts the biasing applied to said rotor unit and causes said rotor unit to move toward a second axial position relative to said stator assembly which locates said impeller in an extended position within said pumping cavity to establish a high flow characteristic for the coolant supplied from said fluid inlet to said discharge outlet in response to said impeller being driven by said rotor unit at a high impellor speed.   
     
     
         11 . The electric water pump of  claim 10  wherein said rotor unit is offset relative to said stator assembly in its first position, and wherein said rotor unit is aligned relative to said stator assembly in its second position. 
     
     
         12 . The electric water pump of  claim 10  wherein said biasing mechanism includes a biasing spring configured to exert a preload on said rotor unit for biasing said rotor unit toward its first position. 
     
     
         13 . The electric water pump of  claim 10  wherein said biasing mechanism is a magnetic arrangement including a plurality of magnets mounted to said rotor unit and operable to align a magnetic field established between said stator assembly and said motor unit when said rotor unit is located in its first position. 
     
     
         14 . The electric water pump of  claim 10  wherein said rotor unit includes a rotor shaft supported for sliding axial translation in said pump housing and having an end portion fixedly secured to said impeller. 
     
     
         15 . The electric water pump of  claim 10  wherein a pressure differential established across said impeller in response to increasing the impeller speed is operable to cause said impeller to move from its retracted position into its extended position which causes said rotor unit to move from its first position into its second position relative to said stator assembly. 
     
     
         16 . The electric water pump of  claim 15  wherein an interface between said fluid inlet and said pumping cavity defines an annular flange surface, wherein said impeller is configured to include a rim surface aligned with said flange surface of said pump housing, and wherein a large clearance gap is established between said flange surface and said rim surface when said impeller is located in its retracted position, said large clearance gap configured to decrease a flow rate of the coolant. 
     
     
         17 . The electric water pump of  claim 16  wherein a small clearance gap is established between said flange surface and said rim surface when said impellor is located in its extended position, said small clearance gap configured to increase the flow rate of the coolant.