Electric machine with stator sleeve and method of forming the same

Abstract

The invention relates to an electric machine having a stator sleeve and a method of forming the electric machine. An electric machine has a stator wrapped by a stator sleeve coupled to an interior surface of a housing. A thermal barrier is disposed between an outer surface at an axial center of the stator sleeve and the housing.

Description

Background Art

[0001] Contemporary aircraft engines include an electric machine assembly or generator system that provides electrical energy to power systems and components on the aircraft with the aircraft engine in generator mode. Some aircraft engines may further include a starter / generator (S / G) system or motor / generator (M / G) that acts as a motor to start the aircraft engine from a high pressure spool of the aircraft engine or to drive the engine from a low pressure spool of the engine, and as a generator to provide electrical energy to power systems on the aircraft after the engine is running. The motor and generator may be a wet cavity system in which the cavity containing the rotor and stator is exposed to a fluid coolant or a dry cavity system in which the cavity is not exposed to the fluid coolant. Summary of the invention

[0002] Technical Solution 1. A motor, comprising:

[0003] a housing having a housing interior surface defining a first aperture;

[0004] a stator disposed in the first bore, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second bore;

[0005] an annular stator sleeve disposed between the stator and the housing interior surface, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third aperture, the stator sleeve comprising: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposite second diameter end portion axially spaced from the first diameter end portion having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion and having a radially outer third peripheral stator sleeve surface; and

[0006] A thermal barrier is disposed between the radially outer third peripheral stator sleeve surface and the housing interior surface.

[0007] Technical Solution 2. The electric motor according to any of the preceding technical solutions further comprises a rotor disposed in the second hole, the rotor comprising a rotatable shaft rotatable relative to the stator and defining a rotation axis.

[0008] Technical Solution 3. An electric machine according to any of the preceding technical solutions, wherein the radially outer first peripheral stator sleeve surface and the radially outer second peripheral stator sleeve surface are connected to the housing inner surface.

[0009] Technical Solution 4. An electric machine according to any of the preceding technical solutions, wherein the radially outer first peripheral stator sleeve surface and the radially outer second peripheral stator sleeve surface are connected to the housing inner surface via interference fit.

[0010] Technical Solution 5. An electric machine according to any of the preceding technical solutions, wherein the radially inner peripheral stator sleeve surface is coupled to the radially outer peripheral stator surface.

[0011] Technical Solution 6. An electric machine according to any of the preceding technical solutions, wherein the radially inner peripheral stator sleeve surface is coupled to the radially outer peripheral stator surface via an interference fit.

[0012] Technical Solution 7. An electric motor according to any of the foregoing technical solutions, wherein the radially outer first peripheral stator sleeve surface, the radially outer second peripheral stator sleeve surface and the radially outer third peripheral stator sleeve surface respectively define a first diameter, a second diameter and a third diameter.

[0013] Technical Solution 8. An electric motor according to any of the preceding technical solutions, wherein the third diameter is smaller than the first diameter and the second diameter.

[0014] Technical Solution 9. An electric machine according to any of the preceding technical solutions, wherein the radially outer third peripheral stator sleeve surface and the housing interior surface cooperatively define a cavity therebetween.

[0015] Technical Solution 10. An electric machine according to any of the preceding technical solutions, wherein the thermal barrier is disposed in the cavity.

[0016] Technical Solution 11. An electric motor according to any of the preceding technical solutions, wherein the cavity surrounds the stator sleeve.

[0017] Technical Solution 12. An electric machine according to any of the preceding technical solutions, wherein the cavity extends axially between the first diameter end portion and the second diameter end portion of the stator sleeve.

[0018] Technical Solution 13. An electric machine according to any of the preceding technical solutions, wherein the stator sleeve is formed of a first material, and the thermal barrier comprises a second material.

[0019] Technical Solution 14. An electric motor according to any of the preceding technical solutions, wherein the first material has a first thermal conductivity, and the second material has a second thermal conductivity, and wherein the second thermal conductivity is less than the first thermal conductivity.

[0020] Technical Solution 15. An electric motor according to any of the preceding technical solutions, wherein the second material partially fills the cavity.

[0021] Technical Solution 16. An electric machine according to any of the preceding technical solutions, wherein the second material defines a coating disposed on the surface of the radially outer third peripheral stator sleeve.

[0022] Technical Solution 17. An electric motor according to any of the preceding technical solutions, wherein the second material is air.

[0023] Technical Solution 18. A method for forming a motor, comprising:

[0024] disposing a stator in a first aperture defined by an interior surface of the housing, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second aperture;

[0025] disposing an annular stator sleeve between the stator and the housing interior surface, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third aperture, the stator sleeve comprising: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposing second diameter end portion axially spaced from the first diameter end portion having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion having a radially outer third peripheral stator sleeve surface; and

[0026] A thermal barrier is disposed between the radially outer third peripheral stator sleeve surface and the housing interior surface.

[0027] Technical solution 19. The method according to any of the preceding technical solutions, wherein arranging the thermal barrier between the radially outer third peripheral stator sleeve surface and the housing interior surface comprises:

[0028] forming a cavity between the radially outer third peripheral stator sleeve surface and the housing interior surface; and

[0029] The thermal barrier is disposed in the cavity.

[0030] Technical Solution 20. A method according to any of the preceding technical solutions, wherein the stator sleeve is formed of a first material having a first thermal conductivity, and the thermal barrier comprises a second material having a second thermal conductivity, and wherein the second thermal conductivity is less than the first thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the attached picture:

[0032] Figure 1 is a perspective view of a gas turbine engine with a generator according to various aspects described herein.

[0033] Figure 2 Based on the various aspects described in this article Figure 1 A perspective view of the exterior of the generator.

[0034] Figure 3 According to the various aspects described in this article, Figure 2 A schematic cross-sectional view of the generator is taken along line III-III and illustrates the structure of the generator.

[0035] Figure 4 Based on the various aspects described in this article Figure 3 Schematic enlarged view of the generator.

[0036] Figure 5 is a perspective view of an exemplary stator sleeve according to various aspects described herein.

[0037] Figure 6 is a description of various aspects described herein Figure 4 Schematic diagram of parts of the stator and casing of a generator.

[0038] Figure 7 is a schematic diagram depicting a portion of another exemplary stator and housing for a generator according to various aspects described herein.

[0039] Figure 8 is a flow chart illustrating a method of forming an electric machine according to various aspects described herein. DETAILED DESCRIPTION

[0040] Regardless of whether the electric motor provides driving force or generates electricity, aspects of the present disclosure may be implemented in any environment where electric motors are used. For the purposes of this description, such electric motors will generally be referred to as motors, motor assemblies, or similar language, which is intended to clarify that one or more stator and rotor combinations may be included in a machine. Although the present description is primarily directed to motors that provide power generation (e.g., generators), the present description may also be applicable to motors that provide driving force or motors that provide both driving force and power generation. In addition, although the present description is primarily directed to an aircraft environment, aspects of the present disclosure may be applicable in any environment where electric motors are used. Thus, a brief overview of the envisioned environment should facilitate a more comprehensive understanding.

[0041] As used herein, terms such as “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of individual components.

[0042] Although a "group" of various elements will be described, it will be understood that a "group" may include any number of corresponding elements, including only one element. As used herein, the terms "axial" or "axially" refer to a dimension along the longitudinal axis of the generator or along the longitudinal axis of a component disposed within the generator.

[0043] As used herein, the terms "radial" or "radially" refer to a dimension extending between a central longitudinal axis, an outer circumference, or a circular or annular member disposed thereon. The terms "proximal" or "proximally" used alone or in conjunction with the terms "radial" or "radially" refer to movement in a direction toward the central longitudinal axis or a component being relatively closer to the central longitudinal axis than another component.

[0044] All directional references (e.g., radial, axial, up, down, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are used for identification purposes only to help the reader understand the present disclosure and do not create limitations, especially with respect to its position, orientation, or use. Unless otherwise indicated, connection references (e.g., attached, coupled, connected, and coupled) are to be interpreted broadly and may include intermediate components between a collection of elements and relative movement between elements. As such, connection references do not necessarily imply that two elements are directly connected and in fixed relation to each other.

[0045] As used herein, a "wet" cavity generator includes a cavity containing a rotor and a stator that is exposed to a free fluid coolant (e.g., a coolant that moves freely within the cavity). In contrast, a "dry" cavity generator's rotor and stator may be cooled by a coolant contained within a fluidly sealed passage and confined therein (e.g., does not move freely around the cavity).

[0046] As used herein, the term "disposed below" refers to a relative position that is radially closer to the axis of rotation of the rotatable shaft. Also, as used herein, the term "disposed above" refers to a relative position that is radially farther from the axis of rotation of the rotatable shaft.

[0047] As used herein, the term "electrically insulating" refers to a material that exhibits low electrical conductivity (eg, less than about 10-8 Siemens per meter (S / m)).

[0048] As used herein, the term "thermally insulating" refers to the property of a material that exhibits low thermal conductivity (eg, less than about 200 Watts per meter-Kelvin (W / (mK))).

[0049] As used herein, the term "thermal conductivity" refers to the relative ability of a material to conduct or transfer heat.

[0050] As used herein, the term "thermal barrier" refers to a thermally insulating material or element that operates at elevated temperatures or in an environment having elevated temperatures. That is, a thermal barrier is a material or element formed with a relatively low thermal conductivity (e.g., less than 100 W / mK) that is arranged to prevent or obstruct heat flow therethrough.

[0051] Aspects of the present disclosure described herein are directed to a motor having a rotor assembly arranged to rotate relative to a stator assembly. For purposes of illustration, exemplary aspects will be described herein in the form of a motor (specifically, a generator) for a gas turbine engine and having a rotor assembly. However, it will be appreciated that in a non-limiting example, the motor may be in the form of a generator, a motor, a permanent magnet generator (PMG), or a starter / generator (S / G), etc. However, it will be further understood that the aspects of the present disclosure described herein are not so limited and may have general applicability in other motors or systems. For example, the present disclosure may have applicability for systems in other engines or vehicles, and may be used to provide benefits in industrial applications, commercial applications, and residential applications.

[0052] For example, electric machines (such as conventional wound rotor generators) are the main source of electrical energy for industrial and commercial applications. They are commonly used to convert the mechanical power output of steam turbines, gas turbines, reciprocating engines, and hydro turbines into electrical power. Typically, these electric machines include a central rotatable assembly or "rotor" surrounded by a stationary assembly or "stator". A small air gap separates the rotor from the stator. The rotor may include a rotatable element defining a central axis of rotation and defining a periphery. The rotor typically includes a rotatable shaft and a rotor core having one or more sets of conductive rotor windings. The rotor windings may be wound around the periphery. The rotor windings are typically wound axially around groups of columns or rotor teeth defining slots therebetween. The number of groups of rotor windings typically defines the number of electrical phases of the motor. Portions of the windings of conventional rotors (e.g., end turn portions) typically extend through the rotor or are suspended from the rotor. The end turns of the rotor windings in some electric machines are supported and / or covered by a housing, a cover, or other structure.

[0053] In operation, the rotor of a conventional electric machine is driven to rotate by a rotation source (such as a mechanical machine or electric machine), which may be a gas turbine engine for certain aircraft. The rotor typically rotates at a relatively high number of revolutions per minute (rpm) (e.g., 20,000-500,000 rpm). In many cases, the rotor may spin relative to the stator in response to an electric current. The current passing through the rotor and the stator generates heat. For example, heat is generated in the rotor due to the flow of current through the windings and the changing magnetic field present in the rotor, causing a temperature rise in the rotor. Heat may also be caused by stator core losses, such as due to hysteresis or eddy currents generated during operation. It is desirable to cool the rotor and stator to protect the motor from damage and increase the motor power density to allow greater power from a smaller physical size electric motor.

[0054] Furthermore, due to the relatively linear relationship between the rotational speed and shaft power of an electric machine, increasing the rated speed of a generator can increase the power density and efficiency of the generator. Therefore, there is an increasing demand for conventional electric machines to operate at higher and higher speeds. However, the operation of conventional electric machines at higher speeds can generate more heat that is reduced or removed.

[0055] In some cases, heat is removed by passing air across and through the motor. In other cases, oil or other fluid coolant is passed through the electric motor near the stator. The fluid coolant typically flows through a passage formed in the motor housing adjacent to the stator. In still other cases, the coolant passes through a passage formed in the stator. In some cases, the fluid coolant or oil is splashed on the end turn portions of the rotor windings and stator windings that extend through or are suspended from the rotor or stator, respectively (i.e., at the axial ends of the motor).

[0056] Some conventional electric machines may also include an external cooling jacket to surround the stator and conduct heat away from the stator. For example, the cooling jacket is typically a cylindrical sleeve that contacts the entire axial length of the circumference of the stator to maximize the heat flow from the stator to the cooling jacket. Conventional external cooling jackets typically also include a coolant passage defined therein to surround at least a portion of the stator. The coolant passage has a heat-conducting fluid coolant disposed therein, which is fluidly coupled to a fluid coolant source. The fluid coolant traverses the cooling jacket via the coolant passage, and provides cooling by heat conduction from the stator to the jacket along the entire axial length of the stator to ensure desired generator operation.

[0057] However, such conventional cooling systems increase the cost, complexity, and weight and size requirements of the generator system. Another problem with conventional electric machines is that conventional cooling systems may have difficulty removing heat generated by the stator or at least one of the groups of stator windings. For example, using conventional cooling techniques, heat is typically retained near the axial center of the stator. This typically results in a central "hot spot" where the temperature measured at the axial center of the periphery of the stator is relatively higher than the temperature measured at the axial ends of the stator, which may result in reduced generator performance or output. Cooling such a central hot spot may be challenging, while the axial ends of the stator are relatively easier to cool via thermal convection or thermal conduction.

[0058] As described herein, aspects of the present disclosure are provided to beneficially remove heat from a stator and reduce or eliminate hot spots or relatively higher local temperatures at the axial center of the stator. In both dry-cavity and wet-cavity electric machines, aspects of the present disclosure may be implemented without the need for fluid cooling or in conjunction with a fluid cooling system. As further described herein, aspects are arranged to provide a relatively greater heat flow from the stator to the housing wall surrounding the stator and the axial end of the stator sleeve for improved cooling relative to conventional techniques.

[0059] The exemplary drawings are for illustrative purposes only, and the dimensions, positions, sequences, and relative sizes reflected in the drawings attached hereto may vary. In addition, in some drawings, parts may be omitted for clarity.

[0060] Figure 1 A gas turbine engine 10 having an accessory gearbox (AGB) 12 and an electric motor or generator 14 is illustrated in accordance with aspects of the present disclosure. The gas turbine engine 10 may be a turbofan engine commonly used in modern commercial and military aviation, such as a General Electric GEnx or CF6 series engine, or the gas turbine engine 10 may be a variety of other known gas turbine engines, such as a turboprop or turboshaft engine. The AGB 12 may be coupled to a turbine shaft (not shown) of the gas turbine engine 10 by way of a mechanical power output device 16. The gas turbine engine 10 may be any suitable gas turbine engine used in modern aviation, or the gas turbine engine 10 may be a variety of other known gas turbine engines, such as a turboprop or turboshaft engine. The type and details of the gas turbine engine 10 are not germane to the present disclosure and will not be further described herein. Although a generator 14 is shown and described, by way of non-limiting example, aspects of the present disclosure are not so limited, and aspects may include any electric or electrical machine, such as, but not limited to, a motor or generator, an exciter, and the like.

[0061] Figure 2A non-limiting example of a generator 14 and its housing 18 according to aspects of the present disclosure is more clearly illustrated. The generator 14 may include a clamping interface 20 for clamping the generator 14 to an AGB (not shown). A plurality of electrical connectors may be provided on the exterior of the generator 14 to provide for the transfer of electrical power to and from the generator 14. The electrical connectors may further be connected by cables to an electrical power distribution node of an aircraft having a gas turbine engine 10 to provide power for various items on the aircraft (such as lights and seat back monitors). The generator 14 may include a fluid coolant system for cooling components of the generator 14 or components close to the generator 14 (a non-limiting example of which may be the gas turbine engine 10) or dissipating heat generated thereby. For example, the generator 14 may include a fluid cooling system using oil as a coolant.

[0062] The fluid cooling system may include a cooling fluid inlet port 82 and a cooling fluid outlet port 84 for controlling the supply of coolant to the generator 14. In one non-limiting example, the cooling fluid inlet port 82 and the cooling fluid outlet port 84 may be used to cool at least a portion of the rotor or stator of the generator 14. The fluid cooling system may also include a second coolant outlet port 91 shown at a rotatable shaft portion of the generator 14. Optionally, by way of non-limiting example, the fluid cooling system may include a rotatable shaft coolant inlet port 94 or a generator coolant outlet port 95. Although not shown, aspects of the present disclosure may further include other fluid cooling system components, such as a fluid coolant reservoir fluidly coupled to the cooling fluid inlet port 82, the rotatable shaft coolant inlet port 94, the cooling fluid outlet port 84, or the generator coolant outlet port 95, and a fluid coolant pump (not shown) to forcibly supply coolant through ports 82, 84, 94, 95, or the generator 14.

[0063] exist Figure 3 The non-limiting interior of generator 14 is best seen in Figure 3 It is taken along line III-III. Figure 2. A cross-sectional view of the generator 14 shown in FIG. A rotatable shaft 40 is located within the generator 14 and is the primary structure for supporting a variety of components. The rotatable shaft 40 may have a single diameter or a diameter that may vary along its length. The rotatable shaft 40 is supported by spaced bearings 42 and 44 and is configured to rotate around an axis of rotation 41. Several of the elements of the generator 14 have fixed components and rotating components, wherein the fixed components are fixed relative to the housing 18, and wherein the rotating components are disposed on the rotatable shaft 40 or are rotatably fixed relative to the rotatable shaft 40. Examples of these components may include a host 50 housed in a host cavity 51. The rotating component may include a rotor 52, and the corresponding fixed component includes a stator 54 or a stator core. In this way, the rotor 52 is disposed on the rotatable shaft 40 and rotates with the rotatable shaft 40. The fixed component may be mounted to any suitable portion of the housing 18. The fixed components collectively define an interior through which the rotatable shaft 40 extends and rotates relative thereto.

[0064] It will be appreciated that the rotor 52 may have sets of rotor poles and the stator 54 may have sets of stator poles. The sets of rotor poles may generate sets of magnetic fields relative to the sets of stator poles such that rotation of the rotor magnetic fields relative to the stator poles generates current in the corresponding stator components.

[0065] At least one of the rotor poles and the stator poles may be formed by a core having a post and a wire wound around the post to form a winding or coil, wherein the winding has at least one end turn. The illustrated aspects of the present disclosure include a stator 54 having at least one set of stator windings 90 arranged longitudinally along the stator 54 (i.e., parallel to the axis of rotation 41). The set of stator windings 90 may also include a set of stator winding end turns 92 extending axially beyond opposite ends of the longitudinal length of the stator 54.

[0066] The components of the generator 14 may be any combination of known generators. For example, the main machine 50 may be a synchronous generator or an asynchronous generator. In addition to the accessories shown in this aspect, there may be other components that need to be operated for a specific application. For example, in addition to the electromechanical accessories shown, there may be other accessories driven from the same rotatable shaft 40, such as a fluid coolant pump, a fluid compressor, or a hydraulic pump.

[0067] As explained above, the generator 14 may use a cooling fluid, such as oil, and thus may include a cooling system 80. The cooling oil or fluid may be used to dissipate heat generated by the electrical and mechanical functions of the generator 14. The cooling system 80 using the cooling fluid may also provide lubrication of the generator 14. In the illustrated aspect, the generator 14 may be an oil-cooled wet cavity type cooling system 80, which includes a cooling fluid inlet port 82 and a cooling fluid outlet port 84 for controlling the supply of cooling fluid to the cooling system 80. The cooling system 80 may further include, for example, a cooling fluid reservoir 86 and a plurality of cooling passages. The rotatable shaft 40 may provide one or more channels or paths for a coolant or fluid coolant flow 85 (schematically shown as arrows) for the rotor 52 and a second coolant outlet port 91, wherein residual, unused or unspent oil may be discharged from the rotatable shaft 40.

[0068] In a non-limiting example of the generator 14, the fluid coolant flow 85 may further be directed, exposed, sprayed, or otherwise deposited onto the set of stator windings 90, the set of stator winding end turns 92, or an alternative or additional component. In this example, the fluid coolant flow 85 may flow radially outward from the rotatable shaft 40 toward the set of stator windings 90 or the set of stator winding end turns 92. In this sense, the coolant may cool the corresponding set of stator windings 90 or the set of stator winding end turns 92.

[0069] Figure 4 Partial cross section Figure 3 1 is a perspective view of a portion of the housing 18 and stator 54 of the generator 14, wherein some portions (e.g., the rotor 52, the rotatable shaft 40, etc.) are omitted for clarity. As shown, the generator 14 includes the housing 18, the stator 54 (including the set of stator windings 90), and the stator sleeve 55. The stator 54 circumferentially surrounds the axis of rotation 41.

[0070] The housing 18 includes a housing interior surface 181 and an opposing housing exterior surface 182 spaced from the housing interior surface 181. The housing interior surface 181 is arranged to define a first aperture 191. The housing interior surface 181 circumferentially surrounds or encloses the stator 54. For example, the stator 54 may be disposed in the first aperture 191.

[0071] The stator 54 may define a radially inner peripheral stator surface 151 and an opposite radially outer peripheral stator surface 152 spaced radially outward from the radially inner peripheral stator surface 151. The radially inner peripheral stator surface 151 defines a second aperture 192. The stator 54 may include a stator winding 90 disposed longitudinally or axially (i.e., parallel to the axis of rotation 41) along the radially inner peripheral stator surface 151. The stator winding 90 may be disposed in a slot 96 defined on the radially inner peripheral stator surface 151. The stator winding end turns 92 extend axially beyond opposite ends of the longitudinal length of the stator 54. The rotor 52 and the rotatable shaft 40 (both at Figure 3 ) can be disposed in the second hole 192 and can rotate relative to the stator 54 and define a rotation axis 41.

[0072] Although a substantially rectangular stator winding 90 cross-section is illustrated, in aspects of the present disclosure, any geometric cross-section may be included, including but not limited to circular, oval, square, etc. Non-limiting aspects of the present disclosure may also be included in which the grouped stator windings 90 include a layer of electrically insulating material (not shown) outside the grouped stator windings 90 and encapsulating the grouped stator windings 90 to electrically isolate the grouped stator windings 90 from another group of stator windings 90 and the stator 54 or stator sleeve 55.

[0073] The stator sleeve 55 circumferentially surrounds the stator 54. The stator sleeve 55 is disposed between the stator 54 and the housing 18. More specifically, the stator sleeve is disposed between the radially outer peripheral stator surface 152 and the housing inner surface 181.

[0074] Figure 5 Graphics Figure 4193. The stator sleeve 55 is generally annular with a radially inner peripheral stator sleeve surface 170 defining a third hole 193. The stator sleeve 55 may include: a first diameter end portion 161 having a radially outer first peripheral stator sleeve surface 171; an opposite second diameter end portion 162 axially spaced from the first diameter end portion 161 having a radially outer second peripheral stator sleeve surface 172. An annular intermediate wall portion 163 extends axially between the first diameter end portion 161 and the second diameter end portion 162 and is coupled to the first diameter end portion 161 and the second diameter end portion 162. In non-limiting aspects, the intermediate wall portion 163 may extend along 66% of the axial length of the stator sleeve. In other non-limiting aspects, the intermediate wall portion 163 may extend along between 50-75% of the axial length of the stator sleeve. In other non-limiting aspects, the intermediate wall portion 163 may extend along between 30-90% of the axial length of the stator sleeve 55. Other aspects are not so limited, and the intermediate wall portion 163 may extend along any desired percentage of the axial length of the stator sleeve 55 without departing from the scope of the present disclosure. The intermediate wall portion 163 includes a third radially outer peripheral stator sleeve surface 173. The first peripheral stator sleeve surface 171, the second peripheral stator sleeve surface 172, and the third peripheral stator sleeve surface 173 are radially spaced outwardly and opposite the radially inner peripheral stator sleeve surface 170. In non-limiting aspects, mounting bosses 156 may be formed on the stator sleeve 55 to enable the stator sleeve 55 to be attached to the housing 18, for example, using screws, rivets, or other fasteners (not shown).

[0075] The stator sleeve 55 may be formed of a first material 177. The first material 177 may include a metal. By way of non-limiting example, the metal included in the first material 177 may be steel (i.e., a steel alloy), magnesium (i.e., a magnesium alloy), aluminum (i.e., an aluminum alloy), zinc (i.e., a zinc alloy), or any combination thereof. Although described as including a metal, it is contemplated that the first material 177 may be made of a non-metallic material. By way of non-limiting example, the first material 177 may include carbon. The first material 177 is thermally conductive and has a first thermal conductivity (designated as "TC1"). For example, the first thermal conductivity TC1 may be greater than 200 w / mK. It is further contemplated that the first material 177 may be electrically conductive. That is, the first material 177 may have a volume resistivity of less than 1 x 104 ohm-cm.

[0076] Figure 6 Depicted in cross section Figure 41 is a schematic diagram of a portion of a stator and a housing of a generator 14, wherein some portions (e.g., stator windings 90, rotor 52, rotatable shaft 40, etc.) are omitted for clarity. As shown, the stator sleeve 55 is disposed in a first hole 191 defined by the housing interior surface 181, and the stator 54 is disposed in a third hole 193 defined by the stator sleeve 55. The rotor 52 and the rotatable shaft 40 (both at Figure 3 192 and define the axis of rotation 41. The third radially outer peripheral stator sleeve surface 173 and the housing interior surface 181 cooperatively define a cavity 175 therebetween. In non-limiting aspects, a second material 178 may be disposed in the cavity 175. As illustrated, the proportions of some portions have been exaggerated for clarity. For example, the radial thickness of the cavity 175 and the stator sleeve 55 are exaggerated for visual clarity. It is contemplated that, in practice, the thickness of the stator sleeve or the cavity 175 or both may be proportionally much smaller without departing from the scope of the present disclosure.

[0077] The cavity 175 may surround the stator sleeve 55. In non-limiting aspects, the cavity 175 extends axially between the first diameter end portion 161 to the second diameter end portion 162 of the stator sleeve 55 and radially from the third radially outer peripheral stator sleeve surface 173 to the housing interior surface 181.

[0078] The first radially outer peripheral stator sleeve surface 171 may define a first outer diameter D1, and the second radially outer peripheral stator sleeve surface 172 may define a second outer diameter D2. In non-limiting aspects, the first outer diameter D1 and the second outer diameter D2 may be the same size. The third radially outer peripheral stator sleeve surface 173 defines a third outer diameter D3. The third outer diameter D3 may be smaller than the first diameter D1 and the second diameter D2. As will be appreciated, the third diameter D3, which is smaller relative to the first diameter D1 and the second diameter D2, can position the cavity 175 between the third radially outer peripheral stator sleeve surface 173 and the housing interior surface 181, and enhance the flexibility of the stator sleeve 55 to absorb mechanical stress during operation.

[0079] As illustrated, in non-limiting aspects, the first radially outer peripheral stator sleeve surface 171 and the second radially outer peripheral stator sleeve surface 172 face and are coupled to the housing interior surface 181. For example, the first radially outer peripheral stator sleeve surface 171 and the second radially outer peripheral stator sleeve surface 172 may be secured to the housing interior surface 181 using one or more bolts, screws, pins, keys, or other known fasteners (not shown). In other non-limiting aspects, the first radially outer peripheral stator sleeve surface 171 and the second radially outer peripheral stator sleeve surface 172 may be coupled to the housing interior surface 181 via an interference fit, friction fit, or press fit engagement between the first radially outer peripheral stator sleeve surface 171 and the second radially outer peripheral stator sleeve surface 172 and the housing interior surface 181. Other aspects are not so limited, and it is contemplated that the first radially outer peripheral stator sleeve surface 171 and the second radially outer peripheral stator sleeve surface 172 may be rotatably coupled to the housing interior surface 181 via any desired attachment mechanism.

[0080] As further illustrated, the inner peripheral stator sleeve surface 170 is coupled to the radially outer peripheral stator surface 152. The inner peripheral stator sleeve surface 170 may be secured to the radially outer peripheral stator surface 152 using one or more bolts, screws, pins, keys, or other known fasteners (not shown). In other non-limiting aspects, the inner peripheral stator sleeve surface 170 may be coupled to the radially outer peripheral stator surface 152 via an interference fit, friction fit, or press fit engagement between the inner peripheral stator sleeve surface 170 and the radially outer peripheral stator surface 152. Other aspects are not so limited, and it is contemplated that the inner peripheral stator sleeve surface 170 may be rotatably coupled to the radially outer peripheral stator surface 152 via any desired attachment mechanism.

[0081] The second material 178 has a second thermal conductivity (labeled as "TC2"). The second thermal conductivity TC2 is less than the first thermal conductivity TC1. For example, the second thermal conductivity TC2 may be less than 200w / mK. In one non-limiting aspect, the second material 178 may include air. In some other non-limiting aspects, the second material 178 may include an annular structure 178a formed by an organic (e.g., resin) or an inorganic (e.g., aluminum oxide) material or a combination thereof. For example, the second material 178 may include a mixture of an aluminum oxide composite and a titanium carbide composite. In other aspects, the second material 178 may include a mixture of aluminum oxide and zirconium dioxide. In some aspects, the second material 178 may be a ceramic material. For example, the second material 172 may include, alone or in a variety of combinations of the following, including but not limited to: aluminum oxide (Al 2 O 3 ), silicon carbide (SiC), silicon dioxide (SiO 2)、MgO、ZrO 2 ), yttria-stabilized zirconia (YSZ), silicon nitride (Si 3 N 4 ), aluminum nitride (AlN), boron carbide (B 4 C) and boron nitride (BN). In addition, the second material 178 can include any of glass and glass ceramics, such as borosilicate glass, quartz, aluminosilicate, silicate ceramics, or magnesium silicate, alone or in various combinations thereof. In still other non-limiting aspects, the second material 178 can include, alone or in various combinations thereof, such as aluminum titanate (Al 2 TiO 5 ), barium titanate (BaTiO 3 ) or zirconium titanate (ZrTiO 4 In yet other non-limiting aspects, the second material 178 may include a conductive ceramic such as a carbide, boride, nitride, silicide of a d-block element, including, for example, titanium oxide (TiO x , where x < 1), titanium carbide (TiC x ), titanium nitride (TiN x ), titanium diboride (TiB 2 ), zirconium diboride (ZrB 2 ), Hafnium diboride (HfB 2 )、tungsten carbide (WC), molybdenum disilicide (MoSi 2 ).

[0082] In non-limiting aspects, as illustrated, the second material 178 can be disposed in the cavity 175 to substantially fill the cavity 175. In other aspects, the second material 178 can only partially fill the cavity 175.

[0083] Figure 7 is a schematic diagram depicting portions of another non-limiting aspect of the generator 14 , with some portions (eg, stator windings 90 , rotor 52 , rotatable shaft 40 , etc.) omitted for clarity. Figure 7 An exemplary aspect is similar to Figure 6 However, in Figure 6 The non-limiting aspects of the generator 14 schematically depicted in Figure 7 A significant difference between the generators 14 schematically depicted in FIG. 1 is that, although Figure 7The cavity 175 in has a second material 178 disposed therein, but the second material 178 is arranged as a coating 178b. As shown, the coating 178b may be disposed on the third radially outer peripheral stator sleeve surface 173. Additionally or alternatively, in other non-limiting aspects, the coating 178b may be disposed on a portion of the housing interior surface 181 facing the third radially outer peripheral stator sleeve surface 173. For clarity, the proportion of the coating 178b has been enlarged. Most notably, for clarity, the thickness of the coating 178b is enlarged. It is envisioned that the thickness of the coating 178b may be much smaller in proportion. However, in various aspects, without departing from the scope of the present disclosure, the coating 178b may have any desired thickness. For example, in non-limiting aspects, the coating 178b may have a thickness of 0.005 inches (i.e., 0.5 mils) or less.

[0084] In addition, to enhance the wettability or bonding ability of the coating 178b (i.e., bonding to the third radially outer peripheral stator sleeve surface 173 or the portion of the housing interior surface 181 facing the third radially outer peripheral stator sleeve surface 173, or both), the second material 178 may further optionally include a reactive element. For example, in non-limiting aspects, the reactive element may include any of chromium (Cr), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), or palladium (Pd), either alone or in various combinations thereof. In one aspect, the reactive metal may be premixed with the second material 178 or otherwise included in the second material 178. In other aspects, the reactive element may be deposited on one or both of the third radially outer peripheral stator sleeve surface 173 or the portion of the housing interior surface 181 facing the third radially outer peripheral stator sleeve surface 173 by any number of conventional deposition techniques, such as sputtering deposition or physical vapor deposition. The reactive element is operable to react and bond with the second material 178 and the stator sleeve 55 or housing 18 .

[0085] Regardless of whether the second material 178 is disposed in the cavity 175 as an annular structure 178a or as a coating 178b, the cavity 175 and the second material 178 define a thermal barrier 179 between the stator sleeve 55 and the housing 18. More specifically, the second material 178 defines a thermal barrier 179 between the third radially outer peripheral stator sleeve surface 173 and a portion of the housing interior surface 181 that faces the third radially outer peripheral stator sleeve surface 173.

[0086] refer to Figure 3During power generation operation, the rotation of the rotatable shaft 40 relative to the stationary generator 14 components ultimately causes current to be generated in the stator windings 90, which is further provided to the generator power outlet, which can be used to power or energize a group of electrical loads. Specifically, when the current traverses the corresponding resistive windings, the rotation of the rotor 52 relative to the stator 54 will generate heat due to thermal losses, copper losses, resistive losses, winding losses, etc. In addition to winding losses, the stator windings 90 may also generate or retain unwanted heat due to, for example, core losses (due to hysteresis or eddy currents).

[0087] Also returns reference Figure 6 and Figure 7 In operation, heat generated in the stator 54 is conducted radially outward to the stator sleeve 55. The heat received by the stator sleeve 55 is then conducted radially outward to the housing 18. However, the heat barrier 179 provided at the axial center of the stator sleeve 55 between the stator sleeve 55 and the housing 18 will cause heat to flow more easily from the first diameter end portion 161 and the second diameter end portion 162 of the stator sleeve 55 to the housing 18 than from the intermediate wall portion 163 to the housing 18. That is, due to the heat barrier 179, a relatively larger heat flow from the axial ends of the stator sleeve 55 (i.e., the first diameter end portion 161 and the second diameter end portion 162) to the housing 18 is arranged than from the axial center portion of the stator sleeve 55 (i.e., the intermediate wall portion 163) to the housing 18. In this way, the thermal barrier 179 can be operable to reduce or eliminate hot spots or relatively higher local temperatures at the axial center of the stator sleeve 55, wherein more heat is transferred to the casing at the first diameter end portion 161 and the second diameter end portion 162, where the casing can be more easily cooled (e.g., via convection or a fluid cooling system).

[0088] Thus, in both dry cavity and wet cavity electric machines, aspects of the present disclosure may be implemented without the need for fluid cooling or may be implemented in conjunction with a fluid cooling system. For example, aspects of the present disclosure implement or provide a generator 14 having improved cooling capabilities relative to contemporary generators. Because aspects of the present disclosure significantly improve the cooling capabilities of the stator 54 or the grouped stator windings 90, the generator 14 may be designed or operated so that there is no or no additional cooling system outside the generator 14 other than the cooling system 80 described herein. For example, aspects of the present disclosure may provide a dry cavity generator 14, wherein the system may be designed or operated so that at least there is no or no external fluid cooling jacket, such that the system provides cooling greater than or equal to a predetermined level, wherein the predetermined level is based on the external fluid cooling jacket. Alternatively or in addition to the aforementioned benefits, the aspects described above implement or provide a generator 14 that operates at a higher power density or generates an improved power level without a loss in power generation efficiency due to undesirable heating.

[0089] In non-limiting aspects, operating the cooling system 80 to achieve or provide increased cooling capacity and thus achieve or provide higher power generation operating capacity further enables or provides the generator 14 having a higher overall power density compared to conventional electric machines.

[0090] Yet another advantage of the aspects described above may include improved efficiency with respect to the cooling system. For example, wet cavity type cooling is an effective cooling strategy for the generator, but is not as efficient as the dry cavity cooling described herein. In another non-limiting example, the inefficiency in wet cavity cooling due to the interaction of the oil with the moving components in the cavity causes significant dynamic losses for the generator. Aspects of the present disclosure may provide a configuration of a dry cavity generator including high efficiency cooling and high power density.

[0091] The aspects of the generator 14 described herein may also be included in the method 300 of forming the generator 14. Although for ease of understanding, the aspects of the generator 14 described herein will be described in detail with respect to Figure 3-7 While the method 300 is described with respect to the generator 14 and associated components, it is not otherwise so limited and the method 300 may be implemented using any electric machine without departing from the scope of the present disclosure.

[0092] Figure 8A flow chart depicting a method 300 of forming an electric machine according to various aspects as described herein. For example, the method 300 of forming an electric machine, such as a generator 14, may include, at 310, arranging or positioning a stator 54 in a first aperture 191 defined by a housing interior surface 181. The stator 54 may include a radially outer peripheral stator surface 152 and a radially inner peripheral stator surface 151 that defines a second aperture 192.

[0093] The method 300 may further include arranging or disposing the annular stator sleeve 55 between the stator 54 and the housing interior surface 181 at 320. The stator sleeve 55 may have a radially inner peripheral stator sleeve surface 170 defining a third hole 193. The stator sleeve 55 may further include: a first diameter end portion 161 having a radially outer first peripheral stator sleeve surface 171; an opposite second diameter end portion 162 axially spaced from the first diameter end portion 161 having a radially outer second peripheral stator sleeve surface 172; and an intermediate wall portion 163 extending axially between the first diameter end portion 161 and the second diameter end portion 162 having a third radially outer peripheral stator sleeve surface 173. In a non-limiting aspect, the stator sleeve 55 is formed of a first material 177 having a first thermal conductivity TC1, and the thermal barrier 179 includes a second material having a second thermal conductivity TC2, wherein the second thermal conductivity TC2 is less than the first thermal conductivity TC1.

[0094] The method 300 may further include arranging or disposing the thermal barrier 179 between the third radially outer peripheral stator sleeve surface 173 and the housing interior surface 181 at 330. In non-limiting aspects, arranging the thermal barrier 179 between the third radially outer peripheral stator sleeve surface 173 and the housing interior surface 181 may include: forming a cavity 175 between the third radially outer peripheral stator sleeve surface 173 and the housing interior surface 181; and arranging or disposing the thermal barrier 179 in the cavity 175.

[0095] The described method is for illustrative purposes only and is not intended to limit the method in any way, as it is understood that portions of the method may be performed in a different logical order, may include additional or intervening portions, or described portions of the method may be divided into multiple portions, or described portions of the method may be omitted without detracting from the described method.

[0096] Although the above aspects have been described in terms of generators for gas turbine engines, the aspects described above may be used in any electric machine to significantly increase stator or rotor power generation or cooling capabilities. The aspects of the present disclosure described above may be well suited for certain generator applications, such as bipolar generators (e.g., two stator poles and two rotor poles), which are located close to turbine engines and thus create a high temperature and space or volume constrained environment for generator operation.

[0097] The aspects described above provide multiple benefits, including that they have higher efficiency, high reliability, less maintenance, full attitude operation, and lighter weight. By obtaining the improved cooling capacity of a dry cavity motor without a cooling system outside the machine except for those cooling systems described herein, the motor can eliminate the additional cost, complexity, weight, and size requirements of the additional cooling system that would otherwise be required. The resulting motor is lighter, smaller, and has lower complexity than a conventional dry cavity machine. The resulting motor also has a higher power density due to at least one of the reduced axial length of the rotatable shaft, increased power generation (due to improved cooling capacity), or a combination thereof. Such weight reduction, improved cooling capacity, or higher power density is important in a turbine engine environment and provides a competitive advantage during flight. Reduced complexity can also correspond to reduced maintenance over time, thereby also providing lower operating costs.

[0098] To the extent not already described, the different features and structures of the various aspects may be used in combination with other aspects as desired. The fact that a feature may not be illustrated in some of the aspects is not intended to be interpreted as that the feature may not be illustrated in some of the aspects, but is done for simplicity of description. Thus, the various features of the different aspects may be mixed and matched as desired to form new aspects, whether or not the new aspects are explicitly described.

[0099] This written description uses examples in the present disclosure (including the best mode) and also enables any person skilled in the art to practice the claimed subject matter (including making and using any devices or systems and performing any incorporated methods). The patentable scope of the present disclosure is defined by the claims and may include other examples that occur to one skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if such other examples include equivalent structural elements that are not substantially different from the literal language of the claims.

[0100] The various features, aspects and advantages of the present disclosure may also be embodied in any arrangement of the aspects of the present disclosure, including but not limited to the following technical solutions as defined in the enumerated aspects:

[0101] An electric machine comprises: a housing having an inner surface of the housing defining a first hole; a stator disposed in the first hole, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second hole; an annular stator sleeve disposed between the stator and the inner surface of the housing, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third hole, the stator sleeve comprising: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposite second diameter end portion axially spaced from the first diameter end portion, having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion and having a radially outer third peripheral stator sleeve surface; and a thermal barrier disposed between the radially outer third peripheral stator sleeve surface and the inner surface of the housing.

[0102] An electric machine according to any preceding clause, further comprising a rotor disposed within the second bore, the rotor comprising a rotatable shaft rotatable relative to the stator and defining an axis of rotation.

[0103] An electric machine according to any preceding clause, wherein the radially outer first peripheral stator sleeve surface and the radially outer second peripheral stator sleeve surface are coupled to the housing interior surface.

[0104] An electric machine according to any preceding clause, wherein the radially outer first peripheral stator sleeve surface and the radially outer second peripheral stator sleeve surface are coupled to the housing interior surface via an interference fit.

[0105] An electric machine according to any preceding clause, wherein the radially inner peripheral stator sleeve surface is coupled to the radially outer peripheral stator surface.

[0106] An electric machine according to any preceding clause, wherein the radially inner peripheral stator sleeve surface is coupled to the radially outer peripheral stator surface via an interference fit.

[0107] An electric machine according to any preceding clause, wherein the radially outer first peripheral stator sleeve surface, the radially outer second peripheral stator sleeve surface and the radially outer third peripheral stator sleeve surface define a first diameter, a second diameter and a third diameter respectively.

[0108] An electric machine according to any preceding clause, wherein the third diameter is smaller than the first diameter and the second diameter.

[0109] An electric machine according to any preceding clause, wherein the radially outer third peripheral stator sleeve surface and the housing interior surface cooperatively define a cavity therebetween.

[0110] An electric machine according to any preceding clause, wherein the thermal barrier is provided in the cavity.

[0111] An electric machine according to any preceding clause, wherein the cavity surrounds the stator sleeve.

[0112] An electric machine according to any preceding clause, wherein the cavity extends axially between a first diameter end portion and a second diameter end portion of the stator sleeve.

[0113] An electric machine according to any preceding clause, wherein the stator sleeve is formed from a first material and the thermal barrier comprises a second material.

[0114] An electric machine according to any preceding clause, wherein the first material has a first thermal conductivity, and the second material has a second thermal conductivity, and wherein the second thermal conductivity is less than the first thermal conductivity.

[0115] An electric machine according to any preceding clause, wherein the second material partially fills the cavity.

[0116] An electric machine according to any preceding clause, wherein the second material defines a coating provided on the radially outer third peripheral stator sleeve surface.

[0117] An electric machine according to any preceding clause, wherein the second material is air.

[0118] A method of forming an electric machine includes: disposing a stator in a first hole defined by an interior surface of a housing, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second hole; disposing an annular stator sleeve between the stator and the interior surface of the housing, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third hole, the stator sleeve including: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposite second diameter end portion axially spaced from the first diameter end portion, having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion, having a radially outer third peripheral stator sleeve surface; and disposing a thermal barrier between the radially outer third peripheral stator sleeve surface and the interior surface of the housing.

[0119] A method according to any preceding clause, wherein disposing the thermal barrier between the radially outer third peripheral stator sleeve surface and the housing interior surface comprises: forming a cavity between the radially outer third peripheral stator sleeve surface and the housing interior surface; and disposing the thermal barrier in the cavity.

[0120] A method according to any preceding clause, wherein the stator sleeve is formed of a first material having a first thermal conductivity, and the thermal barrier comprises a second material having a second thermal conductivity, and wherein the second thermal conductivity is less than the first thermal conductivity.

Claims

1. A motor, comprising: a housing having a housing interior surface defining a first aperture; a stator disposed in the first bore, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second bore; an annular stator sleeve disposed between the stator and the housing interior surface, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third aperture, the stator sleeve comprising: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposite second diameter end portion axially spaced from the first diameter end portion having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion and having a radially outer third peripheral stator sleeve surface; and A thermal barrier is disposed between the radially outer third peripheral stator sleeve surface and the housing interior surface.

2. The motor according to claim 1, wherein: The radially outer first peripheral stator sleeve surface and the radially outer second peripheral stator sleeve surface are coupled to the housing interior surface.

3. The motor according to claim 1, wherein: The radially inner peripheral stator sleeve surface is coupled to the radially outer peripheral stator surface.

4. The motor according to claim 1, wherein: The radially outer first, second and third peripheral stator sleeve surfaces define first, second and third diameters, respectively, and wherein the third diameter is smaller than the first and second diameters.

5. The motor according to claim 1, wherein: The radially outer third peripheral stator sleeve surface and the housing interior surface cooperatively define a cavity therebetween.

6. The motor according to claim 5, wherein: The thermal barrier is disposed in the cavity.

7. The motor according to claim 6, wherein: The stator sleeve is formed of a first material and the thermal barrier comprises a second material, wherein the first material has a first thermal conductivity and the second material has a second thermal conductivity and wherein the second thermal conductivity is less than the first thermal conductivity.

8. A method of forming an electric machine, comprising: disposing a stator in a first aperture defined by an interior surface of the housing, the stator having a radially outer peripheral stator surface and a radially inner peripheral stator surface, the radially inner peripheral stator surface defining a second aperture; disposing an annular stator sleeve between the stator and the housing interior surface, the stator sleeve having a radially inner peripheral stator sleeve surface defining a third aperture, the stator sleeve comprising: a first diameter end portion having a radially outer first peripheral stator sleeve surface; an opposing second diameter end portion axially spaced from the first diameter end portion having a radially outer second peripheral stator sleeve surface; and an intermediate wall portion extending axially between the first diameter end portion and the second diameter end portion having a radially outer third peripheral stator sleeve surface; and A thermal barrier is disposed between the radially outer third peripheral stator sleeve surface and the housing interior surface.

9. The method according to claim 8, wherein: Disposing the thermal barrier between the radially outer third peripheral stator sleeve surface and the housing interior surface comprises: forming a cavity between the radially outer third peripheral stator sleeve surface and the housing interior surface; and The thermal barrier is disposed in the cavity.

10. The method according to claim 9, wherein: The stator sleeve is formed of a first material having a first thermal conductivity, and the thermal barrier comprises a second material having a second thermal conductivity, and wherein the second thermal conductivity is less than the first thermal conductivity.

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