Patent Application
20080284273
Electrical motors and generators typically include a stator that is mounted inside a housing and a rotor that is supported for rotation relative to the stator. The rotor can include a shaft and a set of permanent magnets mounted to the shaft. The stator can include a motor casing and coils which can be wound in slots inside of the motor casing. The rotor shaft couples to the motor casing such that the rotor is capable of rotating relative to the casing, and such that the stator coils surround the set of permanent magnets mounted to the shaft. The stator can include a number of stator sections configured to form a ring-like cylinder. The ring-like cylinder of the stator receives the rotor in such a way as to allow the two structures to magnetically interact to create motion.
One aspect of creating this magnetic interaction is found in the stator sections. When a potential is applied through the stator coils an electromagnetic field can be generated. In addition to the electromagnetic field, heat can also be generated due to the electrical resistance of the conductive wire. The more efficiently this heat can be dissipated, the more efficiently the motor can run.
The Figures presented herein provide illustrations of non-limiting example embodiments of the present disclosure. The Figures are not necessarily to scale.
Embodiments of the present disclosure include lead frames, stators, electric motors, and methods of making a stator coupled to the lead frame of the present disclosure. As used herein, lead frames include, but are not limited to, structures that connect an electric motor stator with a control circuit to control the motor commutation process and output currents to the stator in a way that controls the position of a rotor relative to the stator. It will be apparent to those skilled in the art that the following description of the various embodiments of this disclosure are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
As will be described herein, an electric motor includes, among other things, a rotor, a stator disposed around the rotor, and a lead frame coupled to the stator. In the embodiments described in the present disclosure, the stator and lead frame are encapsulated within a thermoset material. In some embodiments, electrically conductive tracks which are part of the lead frame and can form an electrical connection between the stator and a control circuit, extend from the thermoset material. As used herein, a thermoset material includes those polymeric materials that once shaped by heat and pressure so as to form a cross-linked polymeric matrix are incapable of being reprocessed by further application of heat and pressure.
Embodiments of the present disclosure include, but are not limited to, a lead frame for a stator that includes, among other things, two or more control tracks for connection to a stator winding, a Hall-effect sensor coupled to two or more signal tracks for sensing a magnetic field and for providing electric signals to a control circuit, a capacitor coupled to the two or more signal tracks for dampening the electric signal provided by the Hall effect sensor, and a removable support for maintaining a predetermined distance between the two or more control tracks and the two or more signal tracks.
Embodiments of the present disclosure can also include a stator including a stator winding and a lead frame connected to the stator winding, where the lead frame includes two or more electrically conductive tracks to carry electric signals for control of the stator, and an over-molded housing encasing the stator and the lead frame.
Embodiments of the present disclosure can further include an electric motor including a stator, a rotor that rotates relative the stator, a stator winding wound on the stator for generating a magnetic field for driving the rotor, a lead frame connected to the stator winding, and an over-molded housing encasing the stator and the lead frame, where the housing extends between the two or more electrically conductive tracks.
The Figures herein follow a numbering convention in which the first digit or digits correspond to the drawing figure number and the remaining digits identify an element in the drawing. Similar elements between different figures may be identified by the use of similar digits. For example, 102 may reference element “102” in
In some embodiments, the control tracks 102 and signal tracks 104 are formed of an electrically conductive material. For example, the control tracks 102 and signal tracks 104 can be formed of a metal or metal-alloy including copper, gold, silver, aluminum, and/or tin/lead alloys, among others. The control tracks 102 and signal tracks 104 can also be formed of non-metallic materials that are electrically conductive. In some embodiments, the control tracks 102 and signal tracks are formed of the same material. In some embodiments, the control tracks 102 and signal tracks 104 are formed of different materials. The control tracks 102 and signal tracks 104 can then be welded together to form the lead frame 100.
In some embodiments, the lead frame 100 is formed by stamping the control tracks and the signal tracks 102, 104 out of a sheet of material suitable to form the lead frame 100, as discussed herein. The control and signal tracks 102, 104 can then be shaped by bending the tracks 102, 104 into the desired position. In addition, the control and signal tracks 102, 104 can be separated from each other by an electrically-insulative material, as discussed herein.
In some embodiments, the control tracks 102 and signal tracks 104 of the lead frame 100 can be formed of a thin strip or wire of a metal or metal-alloy, as discussed herein, and inserted into a plastic sleeve to hold the control tracks 102 and signal tracks 104 in a desired position. In such embodiments,
As illustrated in
In some embodiments, the removable support 106 can have a bridge structure formed of the same material as the lead frame control tracks 102 and/or signal tracks 104, where the bridge structure is positioned between the control tracks 102 and signal tracks 104. In this embodiment, once the lead frame 100 is formed, the removable support 106 can be removed to electrically separate the control tracks 102 and the signal tracks 104. For example, the bridge structure can be formed such that the bridge between the tracks 102, 104 can be punched out. Other methods of removing the removable support 106 are also possible.
The adhesive can also be either natural based on vegetable, food, and mineral sources, or synthetic such as an elastomer, thermoplastic, or thermosetting adhesive. Since the insulative sheet 110 is formed of an insulative material, the insulative sheet 110 can be placed on the lead frame 100 to hold the control tracks 102 and the signal tracks 104 a predetermined distance apart. In some embodiments, the insulative sheet 110 can remain on the lead frame 100 while the lead frame 100 is encapsulated with an over-molded housing, as discussed herein. Alternatively, the insulative sheet 110 can be removed from the lead frame 100 before the lead frame 100 is encapsulated with an over-molded housing.
As shown in
In some embodiments, the two or more signal tracks 104 can include a first signal track 122, a second signal track 124, and a third signal track 126. In some embodiments, the Hall-effect sensor 116 can be coupled to the first, second, and third signal tracks 122, 124, 126. In some embodiments, a first capacitor 128 can be coupled to the third signal track 126 and the second signal track 124 and a second capacitor 130 can be coupled to the first signal track 122 and the second signal track 124 at a point distal to the Hall-effect sensor 116. In this embodiment, the first and second capacitors 128, 130 can dampen the electric signals sent by the Hall-effect sensor 116 to a control circuit.
In some embodiments, the two or more control tracks 102, as discussed herein, can include a first control track 132 and a second control track 134. In such embodiments, the removable support 106, as discussed herein, can include a first bridge structure 136 positioned between the first control track 132 and second control track 134 proximal to the Hall-effect sensor 116. As discussed herein, the removable support 106 can also be an insulative fabric with an adhesive backing to keep the first control track 132 and second control track 134 a predetermined distance 108 apart.
In some embodiments, the removable support 106 can also include a second, third, fourth, and fifth bridge structure 138, 140, 142, 144 positioned between the first control track 132, the second control track 134, the first signal track 122, the second signal track 124, and the third signal track 126. Other configurations are also possible depending on the number of control tracks 102 and signal tracks 104 that make up the lead frame 100. As discussed herein, the removable support 106 can also be an insulative fabric with an adhesive backing to keep the first control track 132, the second control track 134, the first signal track 122, the second signal track 124, and the third signal track 126 a predetermined distance 108 apart.
In some embodiments, the first, second, and third signal tracks 122, 124, 126 can be positioned between the first and second control tracks 132, 134. Other configurations are also possible.
As the reader will appreciate, the dimensions of the various portions of the stator 246 can be designed to accommodate varying diameters and lengths of insulated conductive wires that form the stator windings 249. In various embodiments, the insulated conductive wire can include various cross-sectional shapes. For example, in some embodiments, the insulated conductive wires can include a round cross-sectional shape, and in other embodiments, the insulated conductive wire can include a planar or rectangular cross-sectional shape (i.e., flat).
The insulated conductive wire can be formed around the stator sections 248 using methods known in the art into the desired stator-winding configuration to form the stator coil. For example, the wires may be shaped to form a complete poly-phase stator winding, or may be shaped to form separate single-phase stator windings, which subsequently may be combined into a multiple phase configuration, if the desired application so requires. In various embodiments, the stator windings 249 can be produced from conductive wire of a desired gauge, the conductive wire comprising a single strand conductive wire pre-coated with insulation.
The stator sections 248 can include a stator core formed, for example, of stacked metal laminations, where a portion of the stator core serves as a magnetic pole for the stator. The stator core can include various types of stacks of metal laminations. For example, in some embodiments, the stacked laminations forming the stator sections 248 can be iron and/or other metal or metal-alloys that can provide a magnetic field (e.g., cobalt, nickel, alloys thereof). As will be appreciated, the stator core can be formed of varying numbers of blocks of stacked laminations of metal (e.g., one block or more).
In addition, in some embodiments, the stator 246 can also include stator winding and locking features, wire guides, sensor board mountings, and wire insulation. Also, in some embodiments, the stator 246 can include terminals 252 for connecting the lead frame 200 to the stator 246. In some embodiments, the lead frame 200 control tracks 202 can be crimped over the terminals 252 and coupled to the terminals 252 using a plasma arc weld. Other methods of coupling the terminals 252 and the control tracks 202 are also possible.
As illustrated, the lead frame 200 can be connected to the stator 246 via the terminals 252 on the top surface of the bobbin 247. In such embodiments, the lead frame 200 extends from the terminals 252 parallel relative the top surface of the bobbin 247. Embodiments of the present disclosure are not limited to lead frames 200 extending from the terminals 252 parallel relative the top surface of the bobbin 247. In some embodiments, the lead frame 200 can extend from the terminals 252 at an acute or obtuse angle relative the top surface of the bobbin 247.
In some embodiments, the terminals 252 can be placed circumferentially around the top surface of the stator 246 to allow the stator windings 249 to be connected to more than one lead frame 200. Alternatively, a circular lead frame 200 can be connected to terminals 252 placed circumferentially around the top surface of the stator. Other configurations for the lead frame 200 are also possible, including a half-circle shape, among others.
In some embodiments, the lead frame 200 can include a Hall-effect sensor 216, as discussed herein. The Hall-effect sensor 216 can be coupled to two or more signal tracks 204 to sense a magnetic field and to provide electric signals to a control circuit via the signal tracks 204. In some embodiments, the lead frame 200 can also include capacitors 218 for dampening the electric signal provided by the Hall-effect sensor 216, as discussed herein.
As discussed herein, the stator 246 can be coupled to the lead frame 200 using the terminals 252, which are in turn, coupled to terminal portions of the stator windings 249. The stator windings 249 are coupled to the lead frame 200 such that the terminals 252, the lead frame 200, and the stator windings 249 form an electrical conduit for conducting electrical potential between the stator 246 and a power source and/or a control circuit. In some embodiments, the lead frame 200 can be connected to the terminals 252 by soldering, welding, or a plug connection.
Methods and processes for forming the various components of the stator described herein are provided as non-limiting examples of the present disclosure. As will be appreciated, a variety of molding processes exist that can be used to form the stator components. Examples of such molding processes can include resin transfer molding, compression molding, transfer molding, and injection molding, among others.
Embodiments of the stator 246 components can also be formed from a number of different materials. For example, the bobbin 247 can be formed of, by way of illustration and not by limitation, thermoplastic and thermoset polymers. As used herein, a thermoset polymer includes those polymeric materials that once shaped by heat and pressure so as to form a cross-linked polymeric matrix are incapable of being reprocessed by further application of heat and pressure. As provided herein, thermoset materials can be formed from the polymerization and cross-linking of a thermoset precursor. Such thermoset precursors can include one or more liquid resin thermoset precursors. In one embodiment, liquid resin thermoset precursors include those resins in an A-stage of cure. Characteristics of resins in an A-stage of cure include those having a viscosity of 1,000 to 500,000 centipoises measured at 77° F. (Handbook of Plastics and Elastomers, Editor Charles A. Harper, 1975).
In the embodiments described herein, the liquid resin thermoset precursor can be selected from an unsaturated polyester, a polyurethane, an epoxy, an epoxy vinyl ester, a phenolic, a silicone, an alkyd, an allylic, a vinyl ester, a furan, a polyimide, a cyanate ester, a bismaleimide, a polybutadiene, and a polyetheramide. As will be appreciated, the thermoset precursor can be formed into the thermoset material by a polymerization reaction initiated by heat, pressure, catalysts, and/or ultraviolet light.
As will be appreciated, the thermoset material used in the embodiments of the present disclosure can include non-electrically conducting reinforcement materials and/or additives such as non-electrically conductive fillers, fibers, curing agents, inhibitors, catalysts, and toughening agents (e.g., elastomers), among others, to achieve a desirable combination of physical, mechanical, and/or thermal properties.
Non-electrically conductive reinforcement materials can include woven and/or nonwoven fibrous materials, particulate materials, and high strength dielectric materials. Examples of non-electrically conductive reinforcement materials can include, but are not limited to, glass fibers, including glass fiber variants, synthetic fibers, natural fibers, and ceramic fibers.
Non-electrically conductive fillers include materials added to the matrix of the thermoset material to alter its physical, mechanical, thermal, or electrical properties. Such fillers can include, but are not limited to, non-electrically conductive organic and inorganic materials, clays, silicates, mica, talcs, asbestos, rubbers, fines, and paper, among others.
In an additional embodiment, the liquid resin thermoset precursor can include a polymerizable material sold under the trade designator “Luxolene” from the Kurz-Kasch Company of Dayton, Ohio.
Examples of thermoplastic polymers include polyolefins such as polyethylene and polypropylene, polyesters such as Dacron, polyethylene terephthalate and polybutylene terephthalate, vinyl halide polymers such as polyvinyl chloride (PVC), polyvinylacetate such as ethyl vinyl acetate (EVA), polyurethanes, polymethylmethacrylate, pellethane, polyamides such as nylon 4, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12 and polycaprolactam, polyaramids (e.g., KEVLAR), segmented poly(carbonate-urethane), Rayon, fluoropolymers such as polytetrafluoroethylene (PTFE or TFE) or expanded polytetrafluoroethylene (ePTFE), ethylene-chlorofluoroethylene (ECTFE), fluorinated ethylene propylene (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylfluoride (PVF), or polyvinylidenefluoride (PVDF).
In one embodiment, the bobbin 247 can be formed through an injection molding process. For example, a single mold can be configured to provide for the shape of the bobbin 247. The thermoplastic material, or thermoset material, can be injected into the mold to form the bobbin 247. In alternative embodiment, the bobbin 247 could be formed in a casting process or stamping. In alternative embodiment, segments of the bobbin 247 can be individually formed and then coupled together to form the bobbin 247. For example, one or more of the circular surfaces 254 can be individually formed. The individual segments can then be coupled together to form the bobbin 247 as illustrated in
Similarly, the stator sections 248 can be individually formed from a thermoset material, as discussed herein, and positioned in the bobbin 247 after the stator windings 249 have been wound around the stator sections 248. The stator sections 248 can then be secured into the appropriate configuration using, for example, an adhesive. Alternatively, the bobbin 247 can be formed with the stator sections 248 as a single part. In this embodiment, the stator windings 249 can be wound around the stator sections 248 after the bobbin 247 has been formed.
As illustrated, the housing 356 encases at least a portion of the stator 346. In addition,
In some embodiments, the over-molded housing 356 can be formed of a material that has characteristics determined by the designer based on environmental, mechanical, and thermal stresses that will be applied to the stator 346 and lead frame 300. For example, in some embodiments, the over-molded housing 356 can be formed of a material with a sufficiently high thermal conductivity to conduct heat away from the stator 346 and the lead frame 300 to operate the stator 346 and the lead frame 300, including other components on the lead frame 300, as discussed herein. A higher thermal conductivity can permit heat rise in the stator windings to be minimized and thus keep stator winding resistance down and the stator winding power up. In addition, the currents through the stator windings generate heat which can have a detrimental affect on the Hall-effect sensor. In particular, many Hall-effect sensors have a maximum operating temperature which is less than one hundred fifty (150) degrees Celsius.
In some embodiments, the material for the over-molded housing 356 can be chosen based on mechanical and environmental stresses on the stator 346 and lead frame 300. For example, an over-molded housing 356 formed of Nylon 6/6 can provide for mechanical strength by restraining the stator winding in the assembly and environmental strength by protecting the stator winding from external contamination.
In an alternative embodiment, the stator 346 can be over-molded with a thermoset material, as discussed herein. As will be appreciated, the stator 348 can be placed within a molding tool and the thermoset material can be supplied to the molding tool to encapsulate the stator 348. In one embodiment, the thermoset material can be supplied to the molding tool to completely encapsulate the stator 348 and the lead frame 300.
Providing the thermoset material can include injecting a thermoset precursor (e.g., low-viscosity thermoset precursor) and catalyst (optional) into the molding under low pressure to fill the mold cavity volume such that the thermoset material encapsulates the stator 348 and the lead frame 300, except the signal and control tracks 302, 304, which extend therefrom. Since the thermoset precursor can include a low viscosity, the thermoset precursor can substantially fill spaces defined by various surfaces of the stator 348 and the lead frame 300, such as spaces between and around the signal and control tracks 304, 302, spaces within slots and grooves, and spaces between stator sections, the stator windings of the stator 346, among other spaces. Heat and pressure can then be applied to cure the thermoset precursor to form the over-molded housing 356. A post cure process can also be used. After curing, the over-molded housing 356 encasing the stator 348 and lead frame 300 can be removed from a molding tool.
Encapsulating (e.g., completely encapsulating) the stator 346 within a thermoset material can provide for improved heat transfer characteristics there from. For example, the thermoset material encasing the stator windings serves to efficiently conduct heat away from the windings and also to fill the gaps between the windings. In addition, the various portions of the stator 346 can be tightly secured together by complete encapsulation. For example, the capsule serves to secure the stator windings to the stator sections 248 to prevent movement of the windings. The thermoset material also serves to secure the stator sections to each other to help prevent the movement of the stator sections with respect to each other.
As will be appreciated, embodiments of the stator 446 and the rotor 458 of the present disclosure can be utilized in a variety of motor configurations. For example, suitable motor configurations can include motors that operate on alternating current (AC) (i.e., induction or synchronous AC motor, switched reluctance motor) and/or direct current (DC) (e.g., a universal motor or a DC motor). As understood, AC motors can be configured as a single-phase, split-phase, poly-phase, or a three-phase motor. Furthermore, it will be apparent to those skilled in the art from this disclosure that although embodiments of the present disclosure are used with an electric motor, the embodiments can also be used with other rotary type electric machines such as a generator or motor/generator.
As illustrated in
As will be appreciated, the rotor 458 can be housed at least partially within and rotate relative the stator about a rotational shaft 464 supported by structures that include bearings. As discussed herein, the stator can include a stator section including a stator core and a number of stator windings formed of insulated conductive wire wound around the stator section. The stator windings can generate a magnetic field for driving the rotor 458.
In some embodiments, the over-molded housing 456 can encase both the stator and the lead frame, as discussed herein. The lead frame can be connected to the stator windings and can include two or more electrically conductive tracks for transmitting electric signals from and/or to the stator windings. As discussed herein, the over-molded housing 456 can extend between the two or more electrically conductive tracks of the lead frame.
While the present disclosure has been shown and described in detail above, it will be clear to the person skilled in the art that changes and modifications may be made without departing from the spirit and scope of the disclosure. As such, that which is set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the disclosure is intended to be defined by the following claims, along with the full range of equivalents to which such claims are entitled.
In addition, one of ordinary skill in the art will appreciate upon reading and understanding this disclosure that other variations for the disclosure described herein can be included within the scope of the present disclosure.
