Integrated alternator for aircraft engines

Abstract

A technique for generating electrical power from an aircraft engine includes providing an alternator disk structure (ADS) between the aircraft engine and a propeller. The ADS is disposed concentrically with an engine drive shaft that drives the propeller and includes at least two concentric regions, a first region having a stator and a second region having a rotor. The first region is rotatably fixed relative to the engine, and the second region is coupled to the engine drive shaft. When the engine rotates the drive shaft, the rotor disposed in the second region rotates concentrically relative to the stator disposed in the first region, thereby inducing a current in a winding of the stator. The rotor and stator thus cooperate to generate electrical power, which is transferred from the stator to electrical subsystems and controls of the aircraft.

Description

Background Art

[0001] Propeller-driven aircraft such as airplanes, helicopters, UAVs (unmanned aerial vehicles), etc. generally generate electric power to drive various subsystems and control devices. Such electric power is generally supplied by an alternator. In a common arrangement, the alternator is coupled to the engine's drive train via a belt. When the engine rotates, a portion of the power from the engine is transmitted to the alternator, and the alternator distributes the power to various subsystems via cables.

[0002] Figures 1A and 1B are respectively a front view and a rear view of a prior design example. As shown, the engine 100 has a drive shaft 110 coupled to the propeller 120. The alternator 130 is coupled to the drive train via a belt 140, and an idler pulley 150 may be adjustable to achieve a desired belt tension. When the engine 100 rotates the propeller 120, the belt 140 rotates the rotor within the alternator 130 relative to the stator. The relative rotation of the rotor with respect to the stator generates electric power. The arrangement of Figures 1A and 1B may further include a second alternator 160. The second alternator 160 may be provided for redundancy and / or as an additional power source.

Summary of the Invention

[0003] Unfortunately, the above configurations are not ideal. For example, the belt-driven alternators in Figures 1A and 1B tend to be heavy and inefficient. Alternators 130 and 160 each weigh several kilograms and typically have a power efficiency of no more than 65%. They also require meticulous maintenance, as the belts wear out and need periodic re-tensioning and eventual replacement. Belt-driven alternators 130 and 160 also tend to consume a large amount of space, especially the space to the sides of the drive shaft. In airplanes and UAVs, such space requirements can result in wider aircraft cowlings than would otherwise be possible, potentially limiting the aerodynamic design to a smaller range than it should be. Aerodynamics can be similarly constrained in both front-propeller configurations (e.g., "tractor") and rear-propeller configurations (e.g., "pusher"). What is needed is a more efficient alternator design.

[0004] In contrast to the preceding approaches described above, an improved technique for generating power from an aircraft engine involves providing an alternator disc structure (ADS) between the aircraft engine and the propeller. The ADS is concentric with the drive shaft that drives the propeller and includes at least two concentric regions: a first region having a stator and a second region having a rotor. The first region is fixed so as to be rotatable relative to the engine, and the second region is coupled to the engine's drive shaft. As the engine rotates the drive shaft, the rotor located in the second region rotates concentrically relative to the stator located in the first region, thereby inducing current in the stator windings. Thus, the rotor and stator work together to generate power, which is transmitted from the stator to the aircraft's electrical subsystems and control systems.

[0005] Advantageously, the improved technology provides alternator functionality without requiring the same external hardware. Weight requirements are significantly reduced. Belts, tensioners, or brackets to hold an external alternator are unnecessary. Furthermore, space requirements on the engine sides are greatly reduced, allowing for more aerodynamic aircraft designs.

[0006] The improved technology could also offer advantages in terms of electrical efficiency. Belt losses are completely eliminated, and the larger radial shape of the ADS compared to that of an external alternator could result in further efficiency benefits.

[0007] A particular embodiment is directed toward a device for generating power in an aircraft having an engine, a propeller, and a drive shaft coupled between the engine and the propeller. The device includes an alternator disc structure (ADS) positioned between the engine and the propeller, the ADS comprising an inner region and an outer region. The inner region of the ADS is fixed so as to be rotatable relative to the engine and includes a stator, the stator having windings. The outer region of the ADS rotates freely relative to the inner region. The outer region is coupled to the drive shaft and includes a rotor having magnets. The rotor of the outer region is configured and positioned to rotate relative to the stator of the inner region in response to the rotation of the drive shaft by the engine, thereby inducing current in the windings of the stator.

[0008] In some embodiments, the outer region of the ADS is part of a startering gear support (SRGS) coupled to the electric starter. The SRGS is configured and positioned to rotate the drive shaft for starting the engine.

[0009] In some cases, the ADS is located inside the aircraft's cowling.

[0010] In some cases, the ADS is located outside any oil-filled section of the engine.

[0011] In some cases, the outer region is coupled to the drive shaft via a coupling.

[0012] In some examples, the rotor includes multiple permanent magnets uniformly arranged at regular angular intervals.

[0013] In some examples, the ADS is offered in multiple configurations, including a first configuration in which the rotor has a relatively small diameter suitable for relatively low-power applications, and a second configuration in which the rotor has a relatively large diameter suitable for relatively high-power applications.

[0014] In some examples, the rotor has more magnets in the second configuration than in the first configuration, and the stator has more coils in the second configuration than in the first configuration.

[0015] In some examples, the rotor has a stronger magnet in the second configuration than in the first configuration.

[0016] In some examples, the inner region windings are provided in multiple groups, with the windings within each group being electrically connected together but electrically isolated from the windings of other groups.

[0017] In some examples, the inner region has an outer circumference, and the windings in the inner region are arranged in clusters along the outer circumference so that the windings are not uniformly distributed along the outer circumference.

[0018] In some examples, the device further includes at least one AC-DC converter integrated into the inner region.

[0019] In some examples, the device further includes at least one AC-AC converter integrated into the inner region.

[0020] In some examples, the device further includes an electronic control circuit coupled to the stator, which is configured and positioned to backdrive the stator windings.

[0021] In some examples, an electronic control circuit configured and positioned to backdrive the stator windings is further configured and positioned to start the engine.

[0022] In some examples, an electronic control circuit configured and positioned to backdrive the stator windings is further configured and positioned to supply power to rotate the propeller in a fuel-electric hybrid configuration.

[0023] Other embodiments are directed toward an aircraft, comprising an engine having a drive shaft, a propeller coupled to the drive shaft, and a first disk region fixed rotatably relative to the engine and including a stator, the stator comprising a first disk region having windings and a second disk region coupled to the drive shaft and including a rotor. The first and second disk regions are concentric with the drive shaft. The second region is configured and positioned to rotate relative to the first region in response to the rotation of the drive shaft, thereby causing the rotor to rotate relative to the stator and inducing current in the windings of the stator.

[0024] In some examples, the second area is part of the startering gear support (SRGS) coupled to the electric starter. The SRGS is configured and positioned to rotate the driveshaft in order to start the engine.

[0025] Further embodiments are directed toward a method for generating power in an aircraft. The method includes operating an aircraft engine to rotate a propeller via a drive shaft. The method further includes providing a first disk region fixed rotatably relative to the engine, the first disk region including a stator, and further includes providing a second disk region, the first and second disk regions being concentric with the drive shaft, and the second disk region including a rotor. The method further includes coupling the drive shaft to the second disk region such that an array of magnets on the rotor rotates with the drive shaft. The method further includes inducing an electric current to flow in the windings of the stator as the array of magnets rotates.

[0026] In some examples, this method further includes providing a first configuration in which the rotor has a relatively small diameter suitable for relatively low-output applications and providing a second configuration in which the rotor has a relatively large diameter suitable for relatively high-output applications.

[0027] The foregoing summary is presented for illustrative purposes to enable the reader to readily grasp the exemplary features presented herein, but this summary is not intended to define essential elements or to limit the embodiments herein in any way. The features described above can be combined in any technically reasonable way, and it is to be understood that all such combinations are intended to be disclosed herein whether or not such combinations are explicitly specified.

[0028] The foregoing and other features and advantages will become apparent from the following description of particular embodiments shown in the accompanying drawings. Here, like reference characters refer to the same or similar parts throughout the different views. The drawings are not necessarily to scale; instead, emphasis is placed on illustrating the principles of the various embodiments.

Brief Description of the Drawings

[0029] [Figure 1] Figures 1A and 1B are, respectively, a front view and a rear view of an aircraft engine including a conventional alternator for generating electrical power. [Figure 2] Figure 2 is a front view of an alternator disk structure according to an embodiment of the present disclosure. [Figure 3] Figures 3A and 3B are, respectively, a front view and a side view of the alternator disk structure of Figure 2. [Figure 4] Figure 4 is a cross-sectional side view and a cross-sectional front view according to one example. [Figure 5] Figure 5 is a cross-sectional front view according to another example. [Figure 6] Figures 6A and 6B are cross-sectional front views according to respective additional embodiments. [Figure 7] Figure 7 is a side view of an example aircraft. [Modes for carrying out the invention]

[0030] Next, embodiments of the improved technology will be described. It should be understood that such embodiments are provided as examples to illustrate certain features and principles, but are not intended to be limiting.

[0031] An improved technology for generating power from an aircraft engine involves providing an alternator disc structure (ADS) between the aircraft engine and the propeller. The ADS is concentric with the drive shaft that drives the propeller and includes at least two concentric regions: a first region having a stator and a second region having a rotor. The first region is fixed so as to be rotatable relative to the engine, and the second region is coupled to the engine's drive shaft. As the engine rotates the drive shaft, the rotor located in the second region rotates concentrically relative to the stator located in the first region, thereby inducing an electric current in the stator windings. In this way, the rotor and stator work together to generate power, which is then transmitted from the stator to the aircraft's electrical subsystems and control systems.

[0032] In some examples, the first region is the inner region and the second region is the outer region. In other examples, the first region is the outer region and the second region is the inner region.

[0033] In some examples, the second part of the disc is part of an existing structure referred to herein as the startering gear support (SRGS). The SRGS is coupled to an electric starter and is configured to rotate the drive shaft to start the engine.

[0034] In some cases, the ADS is located at the end of the aircraft (forward or rear) to ensure easy access for inspection, maintenance, and servicing. For example, the ADS is located inside the aircraft's cowling, eliminating the need to open any oil-containing parts of the engine itself to access it.

[0035] In some cases, ADS can meet a wide range of power requirements in a scalable manner. For example, the stator design can be modified to provide different numbers or configurations of coils to suit different power requirements. As used herein, “coil” refers to one or more “windings,” i.e., conductive paths formed by windings of conductive material around the magnetically permeable core of the stator. Individual coils can be formed from a single wire or other elongated conductor. Fewer coils may be provided for low-power applications, and more coils for high-power applications. Since the stator does not rotate with the drive shaft, the stator coils can be routed in a convenient manner without worrying about weight balance.

[0036] Various rotor designs may also be offered. For example, smaller diameter rotors can be used for lower power applications, while larger diameter rotors can be used for higher power applications, including hybrid (fuel-electric) drive configurations. Larger diameter rotors allow for the use of larger and / or more numerous magnets located on or near the outer rim of the ADS, effectively doubling the power based on both (i) larger and / or more numerous magnets, and (ii) a higher linear velocity of the rotor magnets relative to the stator coils.

[0037] In some examples, the rotor employs permanent magnets, thus eliminating the need for electrical connections or brushes. In some examples, the permanent magnets are neodymium magnets. However, other types of magnets may be used, such as electromagnets or magnets made from other materials. In some examples, the magnets in the rotor are arranged at equal intervals with uniform angular spacing.

[0038] In some examples, the ADS includes, or is coupled to, an AC-DC converter for converting AC power from the stator to DC power to run various subsystems. Any number of AC-DC converters may be provided. Such AC-DC converters may be integrated with the stator or provided separately on a separate circuit board located, for example, near the engine. In some examples, the ADS may include, or be otherwise coupled to, any number of AC-AC converters (e.g., transformers).

[0039] In some examples, an electronic control circuit coupled to the stator is provided to backdrive the stator windings. Such backdriving has the effect of inducing the rotation of the rotor, and consequently the rotation of the aircraft's drive shaft and propeller, and can therefore be a suitable alternative to a separate starter motor. It can also support electric drive in hybrid fuel and electric configurations, for example. For instance, the backdrive circuit can be connected to a battery and directly drive the propeller via electric power. Electric power can assist in takeoff and help offset the maximum power requirements of the engine.

[0040] Figure 2 shows an exemplary alternator disk structure (ADS) 202 according to an embodiment of immediate disclosure. As shown, the ADS 202 comprises an outer region 210 (e.g., a first region) and an inner region 220 (e.g., a second region). The outer region 210 houses the rotor, and the inner region 220 houses the stator. The outer region 210 includes the rotor magnets 212, which are permanent magnets such as neodymium magnets. Such magnets are lightweight and high strength. Other suitable examples of permanent magnets include ferrite, alnico, samarium cobalt, etc. Alternatively, other types of magnets, such as electromagnets, may be used. The magnets 212 have alternating north-south polarity and may be mounted on a support made of, for example, steel or laminated steel. The inner region 220 includes the stator coils 222. Although shown as separate parts (the figure is a cross-sectional view), the stator coils 222 include windings 224 that wrap around projections of the stator's laminated core 226. In one example, the core is made of steel such as electrical steel, and lamination is provided to reduce eddy current losses. The stator coil can be made of any elongated conductive material having external insulation to avoid short circuits with adjacent windings 224 or other conductive components. Non-limiting examples include insulated copper or aluminum wire (e.g., circular, square, or any other suitable cross-sectional shape), insulated metal foil, etc. The stator, and therefore the stator coil 222, is stationary relative to the engine 100. Thus, the stator coil 222 can be wired in any convenient way to the electronics within the aircraft.

[0041] Figure 2 also shows a propeller 120 coupled to the drive shaft 110 of engine 100. The coupling 240, drawn for schematic purposes only, connects the outer region 210, including the rotor, to the drive shaft 110 so that the outer region 210 rotates with the drive shaft 110, while the inner region 220 remains stationary. When engine 100 rotates the propeller 120, the magnets 212 in the outer region 210 (rotor) move through the windings 224 of the stator coil 222 in the inner region 220 (stator), inducing an electric current that can be distributed to various loads in the aircraft.

[0042] In the example shown in Figure 2, the ADS202 is provided as part of the starter gear support (SRGS)250. The SRGS250 is disc-shaped and has external teeth that form a starter gear 252, which is arranged to mesh with the teeth of the starter motor 260. When in operation, the starter motor 260 rotates the SRGS250, which in turn rotates the drive shaft 110 to start the engine 100.

[0043] By providing the ADS202 as part of the SRGS250, the design leverages existing hardware that would typically be provided as part of a standard aircraft. Therefore, the ADS202 can be implemented with minimal additional weight and components. However, providing the ADS202 as part of the SRGS250 is merely one example. Alternatively, the ADS202 may be provided separately from any SRGS, such as on its own dedicated disk assembly.

[0044] The ADS202 offers many advantages over belt-driven alternators. Because the ADS202 does not require a belt, there is no need to tension or replace belts. Furthermore, the permanent magnet design in some embodiments does not require brushes, eliminating the need for maintenance and replacement. Therefore, the ADS202 can be expected to have a long, failure-free lifespan.

[0045] The arrangement in Figure 2 may be modified to suit various power requirements. For example, the magnet 212 may be positioned closer to the outer edge of the outer region 210 (e.g., where the gear 252 is shown), or the outer region 210 itself may be modified to have a larger diameter. The stator coil 222 may be moved outward accordingly. The effect of moving the magnet 212 and coil 222 outward is to increase the output because the linear velocity (and therefore the power generated) of the magnet 212 across the coil 222 increases with radial distance. Furthermore, positioning them further outward allows for the use of more magnets and / or coils, further increasing the output.

[0046] Figures 3A and 3B show additional examples of the ADS202 (front and side views, respectively). Further additional components for engine 100 are shown.

[0047] Figure 4 shows a first design example. Here, the ADS202 may have two independent, dedicated coils 222. Alternatively, the outputs of coils 202 can be combined, for example, by connecting them in series, parallel, or in other suitable ways. Figure 4 shows a fully mounted configuration in which the stator coil 222 extends around the entire 360 ​​degrees. This configuration is suitable for higher power demands.

[0048] Figure 4 further shows an embodiment of the coupling 240 (Figure 2), which is shown here as a dome-shaped cover, similar to the cover of the SRGS250. The depicted cover is integrated with the magnets 212 of the outer region 210 (rotor), so that the outer extent of the cover can be considered as the outer region 210 described above. As the drive shaft 110 rotates, the coupling / cover 240 rotates with the drive shaft 110, and the magnets 212 move beyond the coils 222 of the stator, which remain rotatably fixed relative to the engine 100. For example, as shown on the right side of Figure 4, a bracket 410 may be provided to attach the inner region 220 (stator) to a stationary part of the engine 100, such as the crankcase, engine block, or other engine structure.

[0049] Figure 5 shows another example. Here, the stator winding (coil) 222 is located over only a portion of the inner region 220, such as the length of a partial arc. Thus, the arrangement in Figure 5 is suitable for medium power requirements. The arrangement in Figure 5 is simpler and lighter than the arrangement in Figure 4, and requires fewer brackets 410. In the particular example shown, three coils 222 supply three-phase power, which could be suitable for powering, for example, a three-phase ECU (electronic control unit).

[0050] Figures 6A and 6B show additional examples. Figure 6A shows an example of a two-coil single-phase ADS202 suitable for driving two subsystems. The coil 222 in Figure 6A can share the same stator stack (core 226) and bracket 410. Figure 6B is similar but offers a lighter configuration. The configurations in Figures 6A and 6B are suitable for low-power applications, as well as when two independent outputs are desired.

[0051] Figure 7 shows an example of the arrangement of the engine 100 and ADS202 described above within an aircraft 700. As shown in the figure, the ADS202 can be positioned between the engine 100 and the propeller 120 for easy access for inspection, maintenance, and servicing. Although the example shown illustrates a tractor arrangement, the same principle applies to a pusher arrangement where the propeller is located at the rear of the aircraft.

[0052] While specific embodiments have been described, numerous alternative embodiments or variations are possible. For example, some arrangements may swap the positions of the rotor and stator, such that the rotor is located in the inner region 220 and the stator is located in the outer region 210. Alternatively, embodiments of single-disk or dual-disk arrangements can be configured such that the rotor magnets pass through the stator coils axially rather than radially.

[0053] Furthermore, the embodiments disclosed above show an ADS202 having only a single rotor. This is merely illustrative, and alternative embodiments may provide two separate rotors. For example, the ADS may include an internal rotor in addition to the external rotor (as shown above). The two rotors in this arrangement are coupled to rotate with the drive shaft. In this dual-rotor design, a separate stator coil may be provided near the inner edge of the stator so that the magnets of the internal rotor pass near such stator coils as the rotor rotates relative to the stator.

[0054] Furthermore, it should be understood that the term “alternator” as used herein is intended to refer to any electromechanical device that converts rotational energy into electrical energy. Therefore, this definition of “alternator” can include not only devices commonly referred to as “generators,” but also devices commonly referred to as “alternators.”

[0055] Furthermore, while features have been described and illustrated with reference to specific embodiments of this specification, such features may be included in any of the disclosed embodiments and their modifications, and are also included in this specification. Thus, it can be seen that features disclosed in relation to any embodiment are also included in any other embodiment.

[0056] Where used throughout this specification, the words “equip,” “include,” “contain,” and “have” are intended to define a particular item, step, element, or aspect of something in an open-ended form. Also, where used herein, unless otherwise stated, the word “a set” means one or more things. This is true regardless of whether the phrase “a set” is followed by a singular or plural object or whether a singular or plural verb is conjugated. Also, “a set” of elements may represent fewer elements than all elements present. Thus, there may be more elements of the same kind that are not included in that set. Furthermore, ordinal expressions such as “first,” “second,” and “third” may be used herein as adjectives for identification purposes. Unless specifically indicated, these ordinal expressions do not imply any order or sequence. Thus, for example, the “second” event may occur before or after the “first” event, and may occur even if the first event does not occur. Furthermore, in this specification, identifying a particular element, feature, or act as the “first” such element, feature, or act should not be construed as requiring the existence of a “second” or other such element, feature, or act. Rather, the “first” item may be unique. Also, unless otherwise stated, “based on” is intended to be non-exclusive. Therefore, unless otherwise specified, “based on” should be interpreted as “at least partially based on” rather than “exclusively based on.” While certain embodiments are disclosed herein, it should be understood that these are provided for illustrative purposes only and should not be construed as limiting.

[0057] Therefore, those skilled in the art will understand that various modifications of form and detail can be made to the embodiments disclosed herein without departing from the scope of the following claims.

Claims

1. A device for generating electricity in an aircraft having an engine, a propeller, and a drive shaft coupled between the engine and the propeller, Between the engine and the propeller, an alternator disc structure (ADS) including an inner region and an outer region is arranged. The ADS, which is rotatably fixed relative to the engine block of the engine and includes a stator, has a stator disposed in its inner region, and the stator has windings. The outer region of the ADS, which rotates freely relative to the inner region, is coupled to the drive shaft and includes a rotor. The rotor in the outer region is configured and positioned to rotate relative to the stator in the inner region in response to the rotation of the drive shaft by the engine, thereby inducing current in the windings of the stator. The outer region of the ADS is part of a startering gear support (SRGS) coupled to an electric starter, the SRGS being configured and positioned to rotate the drive shaft in order to start the engine. The SRGS is concentric with the drive shaft and has a starter ring gear configured and positioned to mesh with the gear teeth of the electric starter, the electric starter is configured and positioned to rotate the starter ring gear via the gear teeth, thereby rotating the drive shaft to start the engine.

2. The apparatus according to claim 1, wherein the ADS is located within the cowling of the aircraft.

3. The apparatus according to claim 2, wherein the engine has an oil-filling portion, and the ADS is located outside the oil-filling portion.

4. The apparatus according to claim 1, wherein the outer region is coupled to the drive shaft via a coupling.

5. The apparatus according to claim 1, wherein the rotor includes a plurality of permanent magnets uniformly arranged at a constant angular interval.

6. The apparatus according to any one of claims 1 to 5, wherein the ADS is provided in a plurality of configurations, the plurality of configurations including a first configuration in which the rotor has a relatively small diameter suitable for relatively low-power applications, and a second configuration in which the rotor has a relatively large diameter suitable for relatively high-power applications.

7. The apparatus according to claim 6, wherein the rotor has more magnets in the second configuration than in the first configuration, and the stator has more coils in the second configuration than in the first configuration.

8. The apparatus according to claim 6, wherein the rotor has a stronger magnet in the second configuration than in the first configuration.

9. The apparatus according to claim 1, wherein the windings in the inner region are divided into a plurality of groups, and the windings within each group are electrically connected to each other but are electrically insulated from the windings of other groups.

10. The apparatus according to claim 1, wherein the inner region has an outer circumference, and the windings in the inner region are arranged in a cluster shape along the outer circumference so as not to be uniformly distributed along the outer circumference.

11. The apparatus according to claim 1, further comprising at least one AC-DC converter integrated into the inner region.

12. The apparatus according to claim 1, further comprising at least one AC-AC converter integrated into the inner region.

13. The apparatus according to claim 1, further comprising an electronic control circuit coupled to the stator, wherein the electronic control circuit is configured and arranged to backdrive the windings of the stator.

14. The apparatus according to claim 13, wherein the electronic control circuit, configured and positioned to backdrive the windings of the stator, is further configured and positioned to start the engine.

15. The apparatus according to claim 13, wherein the electronic control circuit configured and positioned to backdrive the windings of the stator is further configured and positioned to supply power for rotating the propeller in a fuel-electric hybrid configuration.

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