Divisible lamination brushless pump-motor having fluid cooling system

Abstract: A brushless pump-motor has a pump housing having an impeller chamber with an impeller in the impeller chamber. A motor assembly is coupled to the pump housing. The motor assembly includes a stator assembly having a plurality of core members. A connecting structure couples the plurality of core members with respect to each other to form a generally annular core assembly such that adjacent core members are disposed in non-contacting relation. Windings are operatively associated with the core members. The stator assembly has an interior portion defining a rotor chamber and a rotor assembly is disposed in the rotor chamber. The connecting structure has a partition portion constructed and arranged to isolate the windings from the rotor chamber. A shaft is provided on which the rotor assembly and impeller are mounted. The shaft includes a hollow portion in open communication with the rotor chamber. Bearing structure is operatively associated with the hollow portion of the shaft for supporting the shaft for rotational movement. An electronic control unit is coupled to the motor assembly and has an upper surface in communication with the rotor chamber. A fluid flow path structure is constructed and arranged to permit fluid (1) to pass from a high pressure portion of the impeller chamber and enter the rotor chamber so that the rotor assembly may be submerged in the fluid, (2) to contact the upper surface of the electronic control unit to cool the electronic control unit, (3) to contact the core members, with the partition portion preventing the fluid from contacting the windings, and (4) to enter the hollow portion of the shaft to cool the bearing structure.

Description: FIELD OF THE INVENTION The present invention relates to a pump-motor having a rotary pump for moving water or other liquid and a brushless electric motor having an improved divisible lamination assembly, wherein the motor has fluid flow passages therein to cool certain areas of the motor. BACKGROUND OF THE INVENTION Pump-motors of the dry winding set type typically include a rotor mounted in a rotor chamber and a stator assembly. The stator assembly, having laminations and a winding set, is operatively associated with the rotor assembly. One type of stator assembly is disclosed in U.S. Patent No. 5,729,072 which has a divided iron core lamination assembly. The divided lamination core assembly includes a plurality of individual laminated iron cores divided for each pole-tooth unit. Windings are wound perpendicularly to the pole-tooth portions of the iron cores and the iron cores are then combined at circumferential portions thereof to form a cylindrical shape. Thereafter, the laminated iron cores are made integral by welding or bonding adjacent iron cores at the circumferential portions to define the stator assembly. However, since the outer circumferential portions of adjacent lamination iron cores are welded or bonded together to define the stator assembly, magnetic leakage may occur at these locations which may reduce the efficiency of the motor by approximately 5% to 10%. In addition, significant time may be required to manufacture this stator assembly since each lamination iron core must be wound separately and thereafter the lamination iron cores are combined by welding or bonding. Other divided iron core lamination assemblies are disclosed in US-A-4392072, GB-A-2123318, GB-A-1572417 and US-A-5212419. Generally, in pump-motors, the rotor assembly shares a bearing-supported shaft with an impeller of the pump. Water pump-motors generally have some type of cooling to extend the operating capability thereof. It is desirable to maintain the temperature of such devices below a predetermined limit in order to prevent deterioration of the device through thermal breakdown or distortion due to thermal expansion of elements of the device. Pump-motors having stator assemblies with divided lamination cores are difficult to cool since the cooling fluid should be isolated from the winding set to maintain dry windings. Thus, there is a need to provide an efficient stator assembly having a divided lamination core assembly which is configured to isolate the windings from cooling fluid flowing through the motor. Further, water pump-motors for use in today's automobiles are electronically controlled and generally have an electronic control unit electrically coupled to the windings of the motor. The electronic control unit generates heat that may limit the operating temperature of the pump-motor. Thus, there is a need to provide cooling not only of the bearings and stator assembly of the device, but also of the electronic control unit thereof. SUMMARY OF THE INVENTION According to the invention there is provided a stator for a motor as set forth in the independent claim and a method of providing a stator assembly for an electric motor is provided as set forth in the independent method claim Other objects, features and characteristic of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a water pump-motor provided in accordance with the principles of the present invention; FIG. 2 is a perspective view of an individual core member of the stator assembly of the pump-motor of FIG. 1; FIG. 3 is a plan view of a plurality of core members joined by a connecting structure to form a core assembly in accordance with the principles of the present invention; FIG. 4 is a cross-sectional view of the core assembly of FIG.3 wherein solid core members are shown above line A and stacked lamina core members are shown below line A; FIG. 5 is a plan view of a stator assembly provided in accordance with the principles of the present invention, shown without the windings thereon; and FIG. 6 is a sectional view of a stator assembly provided in accordance with the principles of the preset invention wherein solid core members are shown above line A and stacked lamina core members are shown below line A. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS Referring to the drawings, a brushless d.c. water pump-motor of the dry winding set type is shown generally indicated at 10 in FIG. 1, which embodies the principles of the present invention. The water pump-motor 10 may be employed in automobiles. The water pump motor 10 includes a pump housing 12 defining an impeller chamber 14. An impeller 16 is disposed in the impeller chamber 14. The pump housing and impeller may be of any conventional type having an exit at an outer or high pressure portion 20 of the impeller chamber 14, and an inlet at a low pressure portion 22 of the impeller chamber 14. A motor assembly, generally indicated at 26, is coupled at a first end 28 thereof to the pump housing 12 via bolting 30. The motor assembly 26 includes a stator assembly, generally indicated at 32, having laminations 34, windings 36 and a flux ring 37. The stator assembly 32 is of the divisible core type. Thus, with reference to FIGS. 2-4, a plurality of individual lamination core members 38 are provided. The core members 38 may be of the solid type, preferably formed from powdered metal and insulated with silicon as shown in FIG. 2, and as shown above the line A in FIG. 4. Alternatively, the core members 38 may be formed by a plurality of stacked laminas that are joined together, as shown below line A in FIG. 4. Certain surfaces of the core members 38' which will be exposed to cooling fluid may be coated with a fluid resistant material such as a thin plastic film to prevent fluid from penetrating between the individual laminas of the core member 38', as will become apparent below. As shown in FIGS. 3 and 4, the individual core members 38 are connected via a connecting structure 40 made of insulating material, to form a generally ring-shaped core assembly, generally indicated at 42, with adjacent cores disposed in non-contacting relation. Thus, a gap 44 is provided between adjacent core members 38. This gap 44 reduces magnetic leakage so that the magnetic field may pass to a permanent magnet of the rotor assembly and not leak to adjacent core members 38, as will become apparent below. The connecting structure 40 is preferably made of any type of plastic material which can maintain its shape in a temperature range of -40 to 140 degrees Celsius. As shown in FIG. 4, the connecting structure 40 is preferably over-molded onto surfaces of the individual core members 38. The connecting structure 40 has opposing partition portions 46 and 48, each being generally in the form of an axially extending annular flange. It can be appreciated that the stator assembly 32 has inside laminations, but due to the connecting structure 40, the windings 36 of the stator assembly 32 can be wound with an outside-type winding operation using a conventional winding machine. Thus, with reference to FIG. 6, the stator assembly 32 is shown with windings 36 around the core members 38. The windings 36 are wound about the core members 38 with a portion of the connecting structure 40 being disposed between the winding 36 and each core member 38. To complete the stator assembly 32, a flux ring 37, made of the powdered metal or of the same material as the lamination core members, is disposed about the outer periphery of the core assembly 42. The flux ring 37 is also over-molded with plastic material 52. With reference to FIGS. 1, and 4, the stator assembly 32 has an interior portion defining a rotor chamber 52. A rotor assembly 54, generally indicated at 54, is disposed in the rotor chamber 52. The rotor assembly 54 has the conventional permanent magnets 56 mounted on the outer peripheral portion thereof such that there is a very narrow air gap between the laminations 34 and the magnets 56 to increase motor efficiency. As shown in FIG. 1, a shaft 58 is provided on which the rotor assembly 54 and impeller 16 are mounted. The shaft 58 is hollow and thus fluidly communicates the rotor chamber 52 with the impeller chamber 14 via passage 60 therethrough. The shaft 58 is mounted for rotation via bearing structure, generally indicated at 62, which is operatively associated with the shaft 58 for supporting the shaft for rotational movement. In the illustrated embodiment, the bearing structure 62 includes a pair of bearings 64. As shown in FIG. 1, the bearings 64 are housed in a bearing housing 66 in the form of a boss which is coupled to the pump housing 12. An electronic control unit 68 containing the circuitry necessary to operate the water pump-motor 10 is connected electrically to the windings 36 of the stator assembly 32. The electrical connection includes the use of tab pockets which contain the starting and ending wire connection. This electrical connection is disclosed in commonly assigned U.S. Patent Application No. 08/961,688, filed October 31, 1997, entitled "Pump Motor Having Fluid Cooling System". The electronic control unit 68 has an upper surface 70 in communication with the rotor chamber 52. Surface 70 may be part of a heat sink of the electronic control unit 68. In accordance with an embodiment of the invention, fluid flow path structure, generally indicated at 72, is provided to permit cooling fluid to pass from the high pressure portion 20 of the impeller chamber 14 to an inlet 74 of the motor assembly 26 and enter the rotor chamber 52 so that the rotor assembly 54 may be submerged in the cooling fluid. The flow of cooling fluid in the motor assembly 26 is shown by the arrow in FIG. 1. The cooling fluid contacts the upper surface 70 of the electronic control unit 68 to cool electronic control unit 68. The fluid contacts the core members 82, which have the isolating material thereon as discussed above, to cool the core members 38. The partition portions 46 and 48 of the connecting structure 40 are arranged to provide a seal between the connecting structure 40 and the motor housing and electronic control unit 68 to prevent the cooling fluid from contacting the windings 36. Cooling fluid enters the hollow portion of the shaft 58 to cool the bearing structure 62 and then fluid returns to the low pressure portion 22 of the impeller chamber 14 via passage 60. Thus, it can be seen that the core assembly laminations, bearing structure and the electronic control unit are cooled effectively by the circulating cooling fluid Due to the partition portions of the connecting structure, the cooling fluid in the rotor chamber is isolated from the stator assembly 32 such that the windings 36 thereof may remain dry, out of fluid contact yet may be cooled indirectly from the circulating cooling fluid.

Claims: A stator (32) for an electric motor (26), the stator (32) comprising: a plurality of core members (38) forming a generally annular core assembly (42); windings (36) disposed around the core members (38), characterised in that it further comprises: a connecting structure (40) composed of insulating material over-molding said plurality of core members (38) and extending therebetween at radially inner end portions of adjacent core members (38) to maintain the plurality of core members (38) in fixed spaced apart relationship and coupling said core members (38) with respect to each other to form the generally annular core assembly (42). The stator (32) according to claim 1, wherein said connecting structure (40) is composed of plastics material. The stator (32) according to claim 2, wherein said plastics material is constructed and arranged to maintain its shape in a temperature range of approximately -40 to 140 degrees Celsius. The stator (32) according to claim 1, wherein each of said core members (38) is composed of powdered metal The stator (32) according to claim 1, wherein each of said core members (38) is composed of a plurality of laminas. The stator (32) according to claim 1, further comprising a flux ring coupled to an outer peripheral portion of said core assembly. The stator (32) according to claim 1, wherein said connection structure (40) defines an inner diameter portion and further defines partition portions (46, 48) extending axially from that opposing surfaces to define annular flanges (46, 48) isolating said windings (36) from said inner diameter portion. A method of manufacturing a stator assembly (32) for an electric motor (26), the method including: providing a plurality of individual core members (38), characterised by the step of over-molding a connecting structure (40) composed of insulating material over and between said core members (38) at radially inner portions of adjacent cores to maintain the core members (38) in fixed spaced apart relationship thereby forming a generally annular core assembly; and performing an outside type winding operation to wind wire about said core members (38). The method according to claim 8, wherein said step of over-molding said connecting structure (40) includes over-moulding plastics material onto surfaces on the core members (38). The method according to claim 9, wherein said plastics material maintains the annular shape in temperature range of -40 to 140 degrees Celsius. The method according to any of the claims 9 to 10, further comprising the step of providing a flux ring (37) on an outer peripheral portion of the core member assembly (38) after said winding operation. The method according to any of the claims 9 to 11, wherein each core member (38) is provided as a solid powdered-metal member. The method according to any of the claims 9 to 12, wherein each core member (38) is provided as a plurality of stacked lamina (34) that are joined together. The method according to any of the claims 9 to 13, wherein fluid resistant material is provided on certain surfaces of said core members (38). The method according to any of the 9 to 14, wherein said connection structure (40) is over-moulded to define opposing, axial extending annual flanges (46,48). The method according to claim 15, wherein said wire is wound so as to be adjacent said annular flanges (46,48). The method according to claims 15 or 16, wherein a flux ring (37) is provided on an outer peripheral portion of said core members (38) such that said wound wire is deposed generally between said flanges (46,48) and that flux ring (37).

Inventors: HORSKI MAREK, KERSHAW PETER A, HORSKI, MAREK, KERSHAW, PETER A.
Applicants: SIEMENS VDO AUTOMOTIVE INC, SIEMENS VDO AUTOMOTIVE INC.
Application year: 1999
Main classification: H02K1
IPC codes: F04D29, H02K5, H02K1, F04D13, H02K3, H02K9