Pump assembly

Abstract

A pump assembly ( 1 ) includes a rotor axle ( 45 ), an impeller ( 12 ) fixed to the rotor axle ( 45 ), and a pump housing ( 11 ) accommodating the impeller ( 12 ). The pump housing ( 11 ) defines a first radial inner reference surface ( 71 ). A drive motor includes a stator ( 17 ) and a rotor ( 51 ) fixed to the rotor axle ( 45 ) for driving the impeller ( 12 ). A rotor can ( 57 ) accommodates the rotor ( 51 ) and includes a rotor can flange ( 63 ). A stator housing ( 13 ) accommodates the stator ( 17 ) and includes windings around a stator core ( 114 ). A first surface portion of the stator core ( 114 ) is overmolded with a first material ( 122 ) as an electrically insulating layer between the windings and the stator core ( 114 ). A second surface portion of the stator core ( 114 ) is overmolded with a second material ( 124 ) forming walls of the stator housing ( 13 ).

What is claimed is: 
     
         1 . A pump assembly comprising:
 a rotor axle extending along a rotor axis;   an impeller fixed to the rotor axle;   a pump housing accommodating the impeller, wherein the pump housing defines a first radial inner reference surface;   a drive motor comprising a stator and a rotor, wherein the rotor is fixed to the rotor axle for driving the impeller;   a rotor can accommodating the rotor, wherein the rotor can comprises a rotor can flange; and   a stator housing accommodating the stator and comprising windings around a stator core, wherein a first surface portion of the stator core is overmolded with a first material as an electrically insulating layer between the windings and the stator core, and wherein a second surface portion of the stator core is overmolded with a second material forming walls of the stator housing.   
     
     
         2 . The pump assembly according to  claim 1 , wherein:
 the stator core is formed as a stator ring with radially inwardly projecting stator teeth;   the first material covers a radially inner surface of the stator ring with a first thickness; and   the second material covers a radially outer surface of the stator ring with a second thickness; and   the first thickness is lower than the second thickness.   
     
     
         3 . The pump assembly according to  claim 2 , wherein the first material has a higher dielectric strength and/or a higher comparative tracking index than the second material. 
     
     
         4 . The pump assembly according to  claim 1 , wherein the second material has a lower flammability than the first material. 
     
     
         5 . The pump assembly according to  claim 1 , wherein the second material has no contact to the stator windings. 
     
     
         6 . The pump assembly according to  claim 1 , wherein the first material forms bobbin webs projecting axially from the stator core. 
     
     
         7 . The pump assembly according to  claim 1 , wherein:
 the pump housing defines a first annular reference surface facing away from the impeller;   the second material defines a second annular reference surface facing towards the impeller; and   the second annular reference surface is biased against the first annular reference surface.   
     
     
         8 . The pump assembly according to  claim 7 , wherein:
 the stator core is formed as a stator ring with radially inwardly projecting stator teeth;   the stator teeth define a second radial inner reference surface; and   the rotor can comprises a radial outer alignment surface aligned essentially perpendicular to the first annular reference surface of the pump housing by radially abutting against the second radial inner reference surface of the stator housing.   
     
     
         9 . The pump assembly according to  claim 1 , further comprising:
 a first radial bearing ring in sliding contact with the rotor axle;   a bearing retainer embracing the first radial bearing ring and centering the first radial bearing ring with respect to the first radial inner reference surface of the pump housing;   the rotor can flange has a radial distance to the pump housing; and   the rotor can comprises a radial inner centering surface centered by radially abutting against a radial outer centering surface of the bearing retainer.   
     
     
         10 . The pump assembly according to  claim 9 , wherein:
 the radial inner centering surface of the rotor can has at least three radial projections; or   the radial outer centering surface of the bearing retainer has at least three radial projections; or   the radial inner centering surface of the rotor can has at least three radial projections and the radial outer centering surface of the bearing retainer has at least three radial projections.   
     
     
         11 . The pump assembly according to  claim 9 , wherein the bearing retainer comprises a radial outer bearing retainer surface having at least three radial projections radially abutting against the first radial inner reference surface of the pump housing and centering the bearing retainer with respect to the first radial inner reference surface of the pump housing. 
     
     
         12 . The pump assembly according to  claim 1 , further comprising a bayonet ring securing the stator housing to the pump housing, wherein the bayonet ring is resiliently preloaded for axially biasing the stator housing against the pump housing towards the impeller. 
     
     
         13 . A method of manufacturing a stator housing of a pump assembly comprising a rotor axle extending along a rotor axis, an impeller fixed to the rotor axle, a pump housing accommodating the impeller, wherein the pump housing defines a first radial inner reference surface, a drive motor comprising a stator and a rotor, wherein the rotor is fixed to the rotor axle for driving the impeller, a rotor can accommodating the rotor, wherein the rotor can comprises a rotor can flange; and a stator housing, the method comprising the steps of:
 accommodating the stator in the stator housing, wherein the stator housing comprises windings around a stator core;   overmolding a first surface portion of the stator core with a first material as an electrically insulating layer between the windings and the stator core;   overmolding a second surface portion of the stator core with a second material forming walls of the stator housing; and   providing a temperature of the stator core that is lower during the overmolding of the second surface portion of the stator core than during the overmolding of the first surface portion of the stator core.   
     
     
         14 . The method according to  claim 13 , wherein the windings are spooled on the first surface portion of the stator core after the first surface portion of the stator core is overmolded with the first material and before the second surface portion of the stator core is overmolded with the second material. 
     
     
         15 . The method according to  claim 13 , wherein:
 the stator core comprises a stator ring and radially inwardly projecting stator teeth;   one or more of the overmolding steps are performed by injection overmolding using an injection mandrel holding the stator core in a well-defined position during overmolding by contacting a radial inner reference surface defined by the stator teeth.   
     
     
         16 . The method according to  claim 13 , wherein the first material has a higher dielectric strength and/or a higher comparative tracking index than the second material. 
     
     
         17 . The method according to  claim 13 , wherein the second material has a lower flammability than the first material. 
     
     
         18 . The method according to  claim 13 , wherein the second material has no contact to the stator windings. 
     
     
         19 . The method according to  claim 13 , wherein the first material forms bobbin webs projecting axially from the stator core.