Abstract:
A fluid pump includes a pump housing having a housing cavity with an inlet and an outlet. An encapsulated stator assembly is positioned within the housing cavity and at least partially defines a fluid passage from the inlet to the outlet. A polymeric capsule member encloses and seals the encapsulated stator assembly, protecting the motor from, and providing heat transfer to, the working fluid. A stator provides a magnetic field which drives a rotor assembly. The rotor assembly rotates an impeller for pumping fluid from the inlet to the outlet.

Description:
TECHNICAL FIELD 
     The present invention relates to a fluid pump containing an encapsulated stator assembly that seals a pump motor and facilitates heat transfer from the motor and the electronics to the working fluid. 
     BACKGROUND ART 
     Use of fluid pumps in vehicle engine cooling systems and various industrial applications is well known. However, typical fluid pumps in both of these areas have inherent limitations. 
     Typically in engine cooling systems, a coolant pump has a pulley keyed to a shaft. The shaft is driven by the engine via a belt and pulley coupling, and rotates an impeller to pump the working fluid. Fluid seals sometimes fail due to the side load from the drive belt, which tends to allow fluid to leak past the seal into the bearing. 
     U.S. Pat. No. 6,056,518, issued on May 2, 2000 to Allen et al., describes one attempt to overcome the shortcomings of prior art vehicle coolant pumps. The &#39;518 patent provides a fluid pump with a switched reluctance motor that is secured to a housing and rotates an impeller for pumping the fluid. This design eliminates the side load problem associated with keyed pulleys, but it is generally not intended for use where larger industrial pumps are required. 
     Industrial pumps are typically driven by an electric motor connected to the pump via a coupling, the alignment of which is critical. Misalignment of the coupling can result in premature pump failure, which leads to the use of expensive constant velocity couplings to overcome this problem. Moreover, industrial pumps are typically air-cooled, relying on air from the surrounding environment. The cooling air is drawn through the motor leaving airborne dust and other contaminants deposited in the motor. These deposits can contaminate the bearings, causing them to fail, or the deposits can coat the windings, shielding them from the cooling air and causing the windings to overheat and short out. 
     Accordingly, it is desirable to provide an improved fluid pump which overcomes the above-referenced shortcomings of prior art fluid pumps, while also providing enhanced fluid flow rate and control capability while reducing costs. 
     DISCLOSURE OF INVENTION 
     The present invention provides a fluid pump with an encapsulated stator assembly that contains a rotor cavity. A rotor assembly, driven by a stator, is positioned within this cavity and turns an impeller for pumping the working fluid. The encapsulated stator assembly prevents the working fluid from directly contacting the motor. It does, however, have an outside wall that is in contact with the working fluid, thereby facilitating heat transfer from the motor to the fluid. 
     More specifically, the present invention provides a fluid pump including a housing having a housing cavity therein. An encapsulated stator assembly is positioned within the housing cavity and at least partially defines a boundary for the working fluid. The encapsulated stator assembly contains a rotor cavity in which a rotor assembly is located. The magnetic field generated by a stator drives the rotor assembly, which is connected to an impeller for pumping the fluid. 
     In a preferred embodiment, the encapsulated stator assembly is a single unit, and is located inside a two-piece housing. A stator comprising steel laminations, windings, and motor power leads, is encapsulated in a thermally conductive, electrically insulative polymeric capsule member. The polymeric capsule member defines a rotor cavity having an opening. The rotor assembly, consists of a rotor with a rotor shaft, the rotor shaft being supported by a front bearing and a rear bearing. Also, in the preferred embodiment, the rear bearing is located within the encapsulated stator assembly, and the front bearing and a seal are positioned within a front cover that plugs the rotor cavity opening. 
     A diffuser is used to help direct fluid flow and thereby increase the efficiency of the pump. The diffuser comprises an inner wall, an outer wall, and a plurality of diffuser vanes. The diffuser vanes are integrally molded to the outer wall of the encapsulated stator assembly. The polymeric capsule member orients the motor power leads with substantial circumferential symmetry around the diffuser. The motor power leads then interface with a circuit board assembly near the outlet of the pump. The working fluid flows around the outside of the encapsulated stator assembly, thereby encountering the diffuser vanes and allowing heat transfer from the motor to the fluid. The working fluid then encounters the encapsulated motor power leads, thereby cooling both the motor power leads and the circuit board assembly. 
     In an alternative embodiment, the one piece encapsulated stator assembly is replaced with a one piece stator housing assembly. This change allows for larger motors to be utilized with the pump, and thereby increases the number of applications in which the invention may be used. The stator housing assembly includes an encapsulated stator assembly and a substantially cylindrical metal case which provides an outlet for a single bundle of motor power leads and also contains diffuser vanes that fully define the boundary of the working fluid. The encapsulated stator assembly is enclosed and sealed by a thermally conductive, electrically insulative polymeric capsule member that defines a motor cavity and provides a heat transfer path to the working fluid. As in the preferred embodiment, a rotor with a rotor shaft is located in the motor cavity and is driven by the magnetic field generated by the stator. The motor housing assembly comprises a front cover, a stator housing assembly, and a rear cover. 
     This alternative embodiment also has a diffuser with diffuser walls and diffuser vanes; however, there are now two sets of diffuser vanes. The front cover is configured with a first set of diffuser vanes and the stator housing assembly is configured with a second set of diffuser vanes. The two covers and the stator housing assembly are joined together and sealed in a manner to prevent the working fluid from entering the motor cavity. 
     Accordingly, an object of the present invention is to provide a fluid pump with an encapsulated stator assembly, the encapsulated stator assembly orienting the motor components and providing heat transfer between the motor and the working fluid. 
     Another object of the invention is to provide a fluid pump with an encapsulated stator assembly, the encapsulated stator assembly forming a diffuser, including a plurality of diffuser vanes. The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a longitudinal cross-sectional view of a fluid pump in accordance with the present invention; 
     FIG. 2 shows a longitudinal cross-sectional view of an encapsulated stator assembly for use with the pump shown in FIG. 1; 
     FIG. 3 shows a perspective view of the encapsulated stator assembly, with the motor cavity opening toward the front and the motor power leads toward the back; 
     FIG. 4 shows a rear perspective view of an impeller for use with the pump shown in FIG. 1; 
     FIG. 5 shows a perspective view of a two piece pump housing with an inlet housing toward the front and an outlet housing toward the rear for use with the pump shown in FIG. 1; 
     FIG. 6 shows a perspective view of the outlet housing corresponding with the embodiment of FIG. 1; 
     FIG. 7 shows a perspective view of the outlet housing of FIG. 6, with a circuit board assembly attached; 
     FIG. 8 shows a side view of a fluid pump in accordance with an alternative embodiment of the invention; 
     FIG. 9 shows a longitudinal cross-sectional view of the fluid pump shown in FIG. 8; 
     FIG. 10 shows a perspective view of the stator housing assembly of the fluid pump of FIG. 8; 
     FIG. 11 shows a longitudinal cross-sectional view of the stator housing assembly of FIG. 10; 
     FIG. 12 shows a longitudinal cross-sectional view of a second alternative embodiment of the fluid pump of FIG. 1; 
     FIG. 13 shows a longitudinal cross-sectional view of a seal cartridge assembly for use with the pump shown in FIG. 12; 
     FIG. 14 shows a perspective view of the seal cartridge assembly and one end of the rotor shaft with a drive pin for use with the pump shown in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a longitudinal cross-sectional view of a fluid pump  10  in accordance with the present invention. A two-piece pump housing comprises an inlet pump housing  12  and an outlet pump housing  14 . The pump housing has a housing cavity  15  therein which contains an encapsulated stator assembly  22 . 
     Referring to FIG. 2, the encapsulated stator assembly  22  defines a rotor cavity  17  with an opening  19 . The encapsulated stator assembly  22  comprises a polymeric capsule member  21 , that has a plurality of diffuser vanes  18  molded integrally thereon. Polymeric capsule member  21  encloses and seals a motor stator  20  and motor power leads  32 . Thus, when the fluid pump  10  is used in an engine cooling system, the motor stator  20  and motor power leads  32  are protected from the liquid engine coolant. Motor stator  20  comprises a plurality of steel laminations  20   a  and a plurality of copper windings  20   b.    
     Returning to FIG. 1, located within rotor cavity  17  is a rotor assembly  28 , consisting of a rotor  28   a  and a rotor shaft  28   b.  The rotor shaft  28   b  is supported by a front bearing  42  and a rear bearing  40 . Rear bearing  40  is located within the encapsulated stator assembly  22 . Front bearing  42  and seal  44  are located within the front cover  26  that plugs the rotor cavity opening  19 . 
     FIG. 3 shows a front perspective view of encapsulated motor assembly  22 . In particular, it shows diffuser vanes  18  which are of split construction (but need not be of split construction for this invention), and the motor power leads  32  which are oriented with substantial circumferential symmetry around the longitudinal axis of the encapsulated stator assembly  22 . As seen in FIG. 1, motor power leads  32  interface with a circuit board assembly  34 . 
     Returning to FIG. 1 impeller  16  is slip fit onto the rotor shaft  28   b  and secured with a buttonhead capscrew  50 . A drive pin  30  transversely located through rotor shaft  28   b  drives impeller  16  via slot  23 . 
     FIG. 4 shows impeller  16  with slot  23  configured to receive drive pin  30 . FIG. 5 shows the inlet pump housing  12  attached to the outlet pump housing  14 . Outlet pump housing  14  is again shown in FIG. 6, this time with motor power leads  32 . FIG. 7 shows the outside of pump  10  including the inlet pump housing  12 , the outlet pump housing  14 , the circuit board assembly  34 , and the connection points between circuit board assembly  34  and the motor power leads  32 . 
     Referring to FIG. 8, a fluid pump  60  is shown in accordance with one alternative embodiment of the invention. Although similar in function to the preferred embodiment, there are a number of notable differences with regard to form. Rather than a two-piece housing, this embodiment employs a three-piece housing comprising an inlet housing  62 , a stator housing assembly  64 , and an outlet housing  66 , assembled with bolts  68 . 
     The stator housing assembly  64 , shown in FIG.  10  and sectioned in FIG. 11, includes an encapsulated stator assembly  75  and a substantially cylindrical metal case  73  which provides an outlet for a single bundle of motor power leads  92  and diffuser vanes  83  that fully define the boundary of the working fluid. The encapsulated stator assembly  75  includes a plurality of steel laminations  90   a,  a plurality of windings  90   b,  and a plurality of motor power leads  92 . A polymeric capsule member  77  encloses and seals the stator assembly  90 , and also defines a rotor cavity  79 . 
     As shown in FIG. 9, a rotor assembly  82 , consisting of a rotor  82   a  and a rotor shaft  82   b,  mislocated within rotor cavity  79 . Rotor shaft  82   b  is supported by a rear bearing  96  positioned within the rear cover  74  which plugs the rear opening of the rotor cavity  79 , and a front bearing  86  and seals  100  positioned within a front cover  70  which plugs the forward opening of the rotor cavity  79 . Drive pin  84  is positioned transversely through rotor shaft  82   b  and drives impeller  76 . 
     Referring to FIG. 9, unlike the preferred embodiment, this alternative embodiment has two separate sets of diffuser vanes, the first set  81  being configured on the front cover  70  and the second set  83  being configured on the stator housing assembly  64 . 
     FIGS. 10 and 11 clearly show the resultant fluid passage  88  formed between the vanes  83  and the inner and outer walls  73   a,    73   b  of the metal case  73 . 
     The encapsulated stator assembly  75  may be manufactured by locating the stator assembly  90  within the substantially cylindrical metal case  73  and temporarily capping the two open ends of the metal case. The stator assembly  90  would then be encapsulated in a polymeric thermally conductive, electrically insulative material  77 . The opposing ends of the metal case would be uncapped, and the front and rear covers  70 ,  74  would be attached to the metal case to complete the encapsulated stator assembly  75 . 
     FIG. 12 shows a second alternative embodiment of the fluid pump of FIG.  1 . Seal cartridge assembly  26  plugs opening  19  in rotor cavity  17 . Wear sleeve  24  is slip fit over the end of rotor shaft  52   b.  An impeller  16  is slip fit onto wear sleeve  24  and is secured to rotor shaft  52   b  with a buttonhead capscrew  50 . A drive pin  30  transversely located through rotor shaft  52   b  and wear sleeve  24  serves multiple functions. The drive pin  30  drives impeller  16  via slot  23  (similarly as shown in FIG.  4 ); it prevents wear sleeve  24  from rotating relative to rotor shaft  52   b;  it captures axial loads from rotor assembly  52 . 
     Some of the features and components of the seal cartridge assembly  26  are shown in FIGS. 12 and 13. Body  27  has a wet side  31  in contact with the working fluid, such as a liquid engine coolant, and a dry side  29 . The body  27  also contains a plurality of holes  47  for attaching the seal cartridge assembly  26  to the encapsulated stator assembly  57 , using bolts  48 . A seal  53  is press fit into the body  27  and plugs an opening on the wet side  31 . 
     Referring to FIG. 14, the wear sleeve  24  is machined to form an inner diameter and has an axis coaxial to an axis of the body  27 . A hole  25  is machined transverse to the wear sleeve axis and is configured to receive drive pin  30 . The rotor shaft  52   b  has a transverse hole  56  that also receives drive pin  30 . 
     Returning to FIG. 13, the front bearing  51 , being press fit onto the substantially cylindrical wear sleeve  24 , plugs an opening on the dry side  29 . The bearing  51  and wear sleeve  24  are press-fit into the cartridge body, and the wear sleeve  24  is slip fit over the shaft  52   b.  The seal cartridge assembly  26  also contains leak detection ports  33 , shown in FIG. 14, for visual or electronic indication of seal  53  failure. 
     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.