Reactionless free-spinning motor with double propellers

Abstract

A system includes a first propeller, a second propeller, an electromagnetic field transmitter coupled to the first propeller, and an electromagnetic field receiver coupled to the second propeller. The electromagnetic field transmitter emits an electromagnetic field, and in response to the electromagnetic field, the electromagnetic field receiver and the second propeller rotate in a first rotational direction, and the electromagnetic field transmitter and the first propeller rotate in a second, opposite rotational direction.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 962,630, filed January 17, 2020, entitled “FREE SPINNING MOTOR WITH DUALPROPELLERS,” which is incorporated herein by reference for all purposes. Background Technology

[0003] New battery-powered (i.e., electric) aircraft are under development. For any vehicle (whether battery-powered or equipped with a combustion engine), range and energy efficiency are important performance indicators. New motors and / or propulsion systems that can improve these indicators for battery-powered aircraft are highly anticipated. Attached Figure Description

[0004] Various embodiments of the invention are disclosed in the following detailed description and accompanying drawings.

[0005] Figure 1A This is a side view illustrating an embodiment of a free-rotating motor with twin propellers.

[0006] Figure 1B This is a top view illustrating an embodiment of a free-rotating motor, wherein an electromagnetic field receiver surrounds an electromagnetic field transmitter.

[0007] Figure 1C A second embodiment of a free-rotating motor with twin propellers is shown.

[0008] Figure 2A This is a front view showing an embodiment of an electric aircraft having a motor and a propeller attached laterally relative to the fuselage.

[0009] Figure 2B This is a top view showing an embodiment of an electric aircraft having a motor and a propeller attached laterally relative to the fuselage.

[0010] Figure 3 This is a front view showing an embodiment of an electric conventional takeoff and landing aircraft having a motor and a propeller attached laterally relative to the fuselage.

[0011] Figure 4 This is a front view showing an embodiment of an eVTOL aircraft with a motor and propeller located on top of the fuselage.

[0012] Figure 5A This is a diagram illustrating an embodiment of a free-rotating motor with propellers having different blade lengths.

[0013] Figure 5BThis is a graph illustrating an example of the response function for propellers with different blade lengths. Detailed Implementation

[0014] This invention can be implemented in a variety of ways, including as: a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer-readable storage medium; and / or a processor, such as a processor configured to execute instructions stored on and / or provided by memory linked to the processor. In this specification, these embodiments or any other form of the invention may be referred to as technology. Generally, within the scope of this invention, the order of steps of the disclosed process may be changed. Unless otherwise stated, components such as processors or memory described as configured to perform tasks may be implemented as general-purpose components temporarily configured to perform tasks at a given time or as specific components manufactured to perform tasks. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data such as computer program instructions.

[0015] The following provides a detailed description of one or more embodiments of the present invention, along with accompanying drawings illustrating the principles of the invention. The invention has been described in conjunction with such embodiments, but is not limited to any particular embodiment. The scope of the invention is defined only by the claims, and the invention covers many alternatives, modifications, and equivalents. To provide a full understanding of the invention, numerous specific details are set forth in the following description. These details are provided for illustrative purposes, and the invention may be practiced according to the claims without requiring some or all of these specific details. For clarity, technical materials known in the art related to the invention have not been described in detail so as not to unnecessarily obscure the invention.

[0016] Various embodiments of a propulsion system with a reactionless free-rotating motor (which has twin propellers) are described herein. In some embodiments, the system includes a first propeller, a second propeller, an electromagnetic field emitter coupled to the first propeller, and an electromagnetic field receiver coupled to the second propeller, wherein the electromagnetic field emitter emits an electromagnetic field, and the electromagnetic field receiver and the second propeller rotate in response to the electromagnetic field in a first rotational direction, and the electromagnetic field emitter and the first propeller rotate in a second rotational direction in opposite directions. Both the emitter and the receiver are allowed to rotate freely, so there is no fixed part of the system; in other words, there is no stator. In a typical motor, the field-emitting part of the motor forms the stator, and the field receiver is a rotor typically implemented by a permanent magnet or an induction rotor core. As will be described in more detail below, this arrangement reduces the motor-to-propeller ratio from 1:1 to 1:2, where a single free-rotating motor powers two propellers. The following figures illustrate various embodiments of this propulsion system.

[0017] Figure 1A This is a side view illustrating an embodiment of a free-rotating motor with two propellers. In this example, there are two propellers: a first propeller (100) connected via a shaft to an electromagnetic field emitter (102); and a second propeller (104) connected via another shaft to an electromagnetic field receiver (106). In this example, to rotate the two propellers (100 and 104), the emitter (102) uses an electric current or, in response to the current, generates or otherwise emits a magnetic field. The receiver (in this example, a cylindrical sidewall) is made of or otherwise comprises (at least in this example) one or more materials that are attracted or repelled by the generated magnetic field (e.g., magnets, metals, coils, etc.). In response to the generated electromagnetic field from the emitter (102), the receiver (106) rotates in a first orientation (in this example, clockwise when viewed from above). A second propeller (104) connected to the receiver (106) via a shaft rotates in the same orientation, thereby generating thrust and / or lift (downward in this example).

[0018] In this example, the motor (which includes an electromagnetic field transmitter (102) and an electromagnetic field receiver (106)) is free-rotating, meaning both the transmitter and receiver are allowed to rotate. In contrast, a conventional motor would fix one of these parts (e.g., a stator) while allowing the other part to rotate (e.g., a rotor). Accordingly, in response to the torque generated on the receiver, the transmitter (102) will rotate in an orientation opposite to (e.g., anti-axial) to the receiver (104). This causes a first propeller (100) connected to the transmitter (100) via a shaft to also rotate and generate thrust and / or lift.

[0019] The transmitter (102) and its associated portions (e.g., including the first propeller (100)) and the receiver (106) and its associated portions (e.g., including the second propeller (104)) will maintain rotational balance. As will be described in more detail below, in some embodiments, the transmitter, receiver, propeller and / or some other portions may be designed to have specific weight, mass, torque and / or aerodynamic reaction torque distributions to achieve certain desired properties or characteristics (e.g., maintaining rotational balance while also achieving certain desired performance, such as with respect to thrust, rotational speed, etc.).

[0020] In this particular example, the two propellers are coaxial, and therefore, in addition to rotating in opposite directions, they also rotate in opposite axial directions, as will be described in more detail below.

[0021] The advantage of the free-rotating motor system with dual propellers described herein is that the propeller-to-motor ratio changes from one (e.g., conventional) motor (e.g., a motor with a stator and rotor) to one propeller to one (free-rotating) motor to two propellers. The motors weigh significantly more than the propellers, and therefore, the ability to power more propellers with a fixed or given number of motors significantly saves weight (e.g., even with the added weight of certain components, such as slip rings required due to the absence of a stator). More specifically, this arrangement achieves a higher total propeller torque (e.g., specific torque) per unit motor weight, and this improvement may not necessarily be limited to configurations where the motors are eliminated (i.e., it is possible to achieve this benefit or improvement without completely eliminating the motors, such as when the propeller weight can be significantly reduced due to the use of paired propellers with smaller diameters). In any case, regardless of how the weight savings are achieved, it translates into increased flight range. To ensure that the slip ring does not negate the benefits of the eliminated motor, the battery can be designed (e.g., from scratch) to have a higher voltage, and the motor can be designed (e.g., from scratch) to have a higher torque constant. Both of these make it possible to use a smaller and therefore lighter slip ring, so that the added weight of the slip ring is less than the weight of the second motor.

[0022] It should be noted that one constraint on the motor and propeller shown here is that they are driven by the same torque. In other words, the propeller cannot be controlled independently (e.g., because there is a single motor and a single motor control signal sent to it). Another constraint is that the propellers are coaxial, and therefore the lower or downstream propeller will operate in the wake or induced flow of the upper or upstream propeller. Accordingly, the lower or downstream propeller can be designed to operate in the wash of another propeller (e.g., the downstream propeller is affected by the induced flow and turbulence generated by the upstream propeller). Some examples of this will be described in more detail below.

[0023] Another benefit of a free-rotating motor system with twin propellers is that the fuselage is unaffected by reaction torque. In some design configurations, this eliminates the need for reaction torque devices and / or heavy structural components (e.g., parts of the vehicle that would be affected or acted upon by the reaction torque).

[0024] It should be noted that the arrangements shown herein are merely exemplary and not intended to be restrictive. For example, in Figure 1A In this configuration, an electromagnetic field emitter (102) surrounds an electromagnetic field receiver (106). In some embodiments, this arrangement is reversed. For example, Figure 1B This is a top view illustrating an embodiment of a free-rotating motor, in which an electromagnetic field receiver (150) surrounds an electromagnetic field transmitter (152). For example, the transmitter may require more and / or larger components than more receivers, and the interior of the inner cylinder may provide a convenient location for placing these components. Other design considerations may suggest an alternative arrangement.

[0025] return Figure 1AIn some embodiments, the first propeller (100) and the second propeller (104) have different blade designs (e.g., blade length, width, and / or angle). For example, this will achieve / lead to higher system efficiency due to the two propellers rotating at different speeds and due to different aerodynamic environments (e.g., incoming flow rates). In other words, the bottom blade is affected by the wake of the upper blade, as described above. In some embodiments, the bottom blade is designed (e.g., by blade twist and / or blade angle selection) to better handle the wake from the upper blade. Similarly, the lower blade may be longer to take advantage of a narrower wake, such that the tip of the bottom blade operates outside the wake from the upper blade. Naturally, static and dynamic balance considerations (e.g., the upper and lower motors and propellers must have the same torque) and other design and / or trade-off considerations can be taken into account. Other blade or propeller parameters that may differ between the two (e.g., upper and lower) include solidity, taper, airfoil selection, blade count, etc. Typically, changing one or more of these parameters will alter the aerodynamic torque applied to the blade and the blade's moment of inertia, which in turn changes the blade's dynamic and static response to the input torque.

[0026] Figure 1C A second embodiment of a free-rotating motor with dual propellers is shown. In this example, the blades of the two propellers (160a and 160b) rotate in the same horizontal plane using the same motor (162). In this example, there are two mechanical couplings (164a and 164b) (e.g., power transmission mechanisms, gearboxes, and / or belt drives) located between the electromagnetic field receiver (166) and the coupled second propeller (160b), the coupled second propeller (160b) mechanically reorienting the direction of rotation between the electromagnetic field receiver and the second propeller such that the first propeller and the second propeller rotate in opposite directions but are not on the same axis (at least in this example). In some embodiments, this is done on the side of the motor with the first propeller (160a).

[0027] One advantage of this design is that one propeller does not operate in the wake of another propeller. Another advantage is that, for safety reasons, it makes it easier to raise all propellers fully above a person's head.

[0028] The accompanying figures illustrate some exemplary vehicle configurations that incorporate exemplary free-rotating motors with twin propellers. These vehicle configurations are merely exemplary and are not intended to be limiting.

[0029] Figure 2AThis is a front view illustrating an embodiment of an electric aircraft with motors and propellers laterally attached relative to the fuselage. In this example, the fuselage (200a) has two beams extending laterally on both sides: upper beams (202a and 202b) and lower beams (204a and 204b). As shown in close-up view 250, the beams include bearings (252) that surround a shaft (254) and allow the shaft to rotate while providing structural support.

[0030] In this example, at least a portion of the bearing (252), the shaft (254), and the free-rotating motor (208) are protected by a cabin or cover (210). This protects these components from dust or debris, for example, when the vehicle is in flight.

[0031] In this example, the vehicle is an electric vertical takeoff and landing (eVTOL) vehicle, and therefore the propeller is arranged to rotate about a vertical axis of rotation. In some embodiments, the propeller is arranged to rotate about a longitudinal axis of rotation (e.g., because the vehicle performs conventional takeoff and landing). The following figures illustrate such an example.

[0032] Figure 2B This is a top view showing an embodiment of an electric aircraft with a motor and propeller attached laterally relative to the fuselage. Figure 2B continue Figure 2A Example. As shown here, the vehicle is gull-wing type, with beams extending rearward from the fuselage (200b). This allows the internal motors and propellers (260b and 260c) to be located behind the center of gravity (262).

[0033] As it extends further outward, the beam then extends forward, positioning the external motors and propellers (260a and 260d) in front of the center of gravity. By positioning both the motors and propellers in front of and behind the center of gravity, this gives the vehicle pitch control (e.g., allowing it to tilt forward and backward).

[0034] To give the vehicle yaw authority, the motors and propellers can be tilted (i.e., they rotate about an axis that is not perfectly vertical). For example, a quadcopter configuration can tilt two adjacent rotors inward (e.g., towards a longitudinal axis extending from the nose to the tail when viewed from above) and tilt two other rotors outward.

[0035] Figure 3This is a front view illustrating an embodiment of an electric conventional takeoff and landing aircraft with motors and propellers laterally attached relative to the fuselage. In this example, the vehicle performs conventional takeoff and landing, and therefore has main wings (302a and 302b) attached to the fuselage (300). As shown here, a front propeller (e.g., 304) extends ahead of the leading edge of the main wings (302a and 302b) via a corresponding shaft (e.g., 306) oriented longitudinally. The shaft (e.g., 306) extends through the main wings (302a and 302b). Inside the main wings are bearings (e.g., 308) that surround each shaft (e.g., 306) and allow the shafts to rotate while providing structural support. For readability, the blades of the free-rotating motors (e.g., each of which includes an electromagnetic field transmitter and an electromagnetic field receiver) and the rear propeller are not shown here.

[0036] In some embodiments, the propeller is positioned above the fuselage. This can reduce the vehicle's footprint for takeoff and / or landing, and / or make it safer, as the propeller will be high enough that it will not hit any pedestrians when the vehicle is on the ground. The accompanying figure below illustrates such an example.

[0037] Figure 4 This is a front view showing an embodiment of an eVTOL aircraft with motors and propellers mounted above the fuselage. In this example, a main shaft (402) extends upward from the fuselage (400). A beam extends outward from the axis and holds a pair of free-rotating motors and propellers in place: one on the left side of the fuselage and one on the right side.

[0038] The upper beams (404a and 404b) extend diagonally upwards and outwards to maintain the vertical shaft connected to the upper rotors (408a and 408b). The lower beams (406a and 406b) extend outwards (e.g., laterally) from the main shaft (402) to maintain the vertical shaft connected to the lower rotors (410a and 410b). As in the example above, bearings allow the shafts (and attached portions) to rotate while providing structural support. As shown here, in some embodiments, the propeller rotates in a plane above the top of the fuselage.

[0039] In some embodiments, the propeller includes a swash plate or some other blade pitch controller (not shown here) to allow yaw, pitch, and / or roll control, enabling the vehicle to maneuver. Alternatively, the propeller and motor may be arranged as described above to provide such control or authority (e.g., tilted, positioning the motor and propeller in front of and behind the center of mass, etc.).

[0040] Figure 5AThis is a diagram illustrating an embodiment of a free-rotating motor with propellers having different blade lengths. In this example, the upper propeller (500) has longer blades, while the lower propeller (502) has shorter blades. Generally speaking, longer blades are desirable due to their better aerodynamic efficiency (e.g., greater thrust per unit surface area) and noise performance (e.g., propeller noise is a function of terminal velocity, and longer blades are able to generate the required thrust at slower speeds, and therefore are quieter), while shorter blades are better in terms of maneuverability.

[0041] In this example, a change in the thrust from the propulsion system is desired, and thus the commanded and controlled torque sent to the free-rotating motor is altered. The change in torque is distributed among the two propellers (500 and 502), and its effect is segmented, where the angular acceleration from the torque share depends on the inertia of the rotating load (i.e., the inertia of a particular propeller, which depends on the blade length) and the counter-torque generated by its rotation. The accompanying figures below illustrate examples of the different response functions produced.

[0042] Figure 5B This is a graph illustrating an embodiment of the response function for propellers with different blade lengths. As described above, propellers with shorter blades (e.g., Figure 5A The 502 in the middle has a smaller moment of inertia, while the propeller with longer blades (e.g., Figure 5A The 500 in the model has a large moment of inertia. In some embodiments, in addition to selecting a specific blade length and / or as an alternative to selecting a specific blade length, the propeller(s) pitch settings (e.g., blade pitch) are designed or otherwise selected for the desired response thrust response of the vehicle.

[0043] In this example, when a command is issued to the motor to increase the propeller's torque output and thus its revolutions per minute (RPM) by increasing angular acceleration, the smaller propeller initially accelerates more quickly and produces a rapid change in thrust response. See, for example, the initial "boom" in the RPM function (552) for the propeller with shorter blades. Over time, the longer-bladed, larger-inertia propeller eventually accelerates and takes on the lifting load. Note, for example, the slower ramp-up in the RPM function (550) for the longer-bladed propeller, where the longer-bladed propeller eventually exceeds the speed of the shorter-bladed propeller. Eventually, both RPM functions stabilize to steady-state speeds (e.g., assuming no further changes or disturbances in the input or system), where the longer-bladed propeller rotates at a faster steady-state speed than the shorter-bladed propeller.

[0044] In other words, the exemplary configuration enables the vehicle to have a single propulsion unit capable of providing both high-bandwidth (e.g., rapid) thrust response (see, for example, the initial rise of the shorter-bladed RPM function (552)) and efficient steady-state lift generation (e.g., the longer-bladed RPM function (550) once the propeller reaches speed) within a single high-specific-torque propulsion unit. In other words, a shorter-bladed propeller is desirable for its rapid response and / or maneuverability, while a longer-bladed propeller is desirable for its lower noise output and efficient steady-state performance, and this configuration provides some of both desirable aspects.

[0045] It should be noted that the way torque is distributed between the two propellers (e.g., the shape of the two response functions) can be adjusted to obtain favorable and / or desired effects (e.g., how quickly the propeller with the longer blades reaches speed, the duration and / or height of the initial bulge of the RPM function of the shorter blades, the two steady-state speeds, etc.).

[0046] While alternative solutions could include a free-rotating motor comprising both a set of longer-bladed propellers with matching sets and a set of shorter-bladed propellers, available surface area on the aircraft frame, vehicle footprint, and / or other space and weight constraints may make the use of matching propellers unattractive. In such applications, the configuration shown here may be a more desirable option because it is a single system occupying less space and simultaneously provides at least some of the desirable characteristics associated with both types of propellers.

[0047] As illustrated in this example, in some embodiments, the first propeller has a first blade length, and the second propeller has a second blade length different from the first blade length. In some embodiments, the first propeller has a first blade pitch setting, and the second propeller has a second blade pitch setting different from the first blade pitch setting. If both blade length and blade pitch setting are used to regulate or otherwise adjust the inertia and aerodynamic counter-torque of the two propellers, the propeller with shorter blades will have a higher pitch setting. This allows the propeller with lower inertia to accelerate rapidly in order to dynamically respond to changes in the commanded torque. A higher blade pitch setting on the smaller diameter propeller results in a situation where the magnitude of the aerodynamic counter-torque response on the smaller diameter propeller is higher during transient events than it is in steady state (e.g., see the bulge in the RPM function 552 before steady state). This reversal to steady state occurs when the larger diameter propeller with higher inertia accelerates to its steady-state speed and relieves the torque load on the smaller propeller.

[0048] While examples of propeller radius and blade pitch are used here as our independent inputs to change the moment of inertia and aerodynamic counter-torque from the propeller, there are numerous options available for tuning these parameters to achieve the desired transient and steady-state propulsion response.

[0049] Although the foregoing embodiments have been described in detail to a certain extent for clarity of understanding, the invention is not limited to the details provided. Many alternative ways of implementing the invention exist. The disclosed embodiments are illustrative and not restrictive.

Claims

1. A propulsion system, comprising: First propeller; Second propeller; Motors, including: An electromagnetic field emitter, which is connected to the first propeller; and An electromagnetic field receiver is coupled to the second propeller, wherein the electromagnetic field transmitter emits an electromagnetic field and responds to the electromagnetic field: The electromagnetic field receiver and the second propeller rotate in the first rotation direction; and The electromagnetic field emitter and the first propeller rotate in opposite second rotational directions; The system also includes at least one of the following: A first mechanical coupling mechanically reorients the direction of rotation between the electromagnetic field receiver and the second propeller, such that the first propeller and the second propeller are not coaxial; or The second mechanical coupling mechanically reorients the direction of rotation between the electromagnetic field emitter and the first propeller, such that the first propeller and the second propeller are not on the same axis.

2. The propulsion system according to claim 1, characterized in that: The system is included in a vertical takeoff and landing vehicle; and The first propeller and the second propeller rotate about a substantially vertical axis of rotation.

3. The propulsion system according to claim 1, characterized in that, The first propeller has a first blade length, and the second propeller has a second blade length different from the first blade length.

4. The propulsion system according to claim 1, characterized in that, The first propeller has a first blade pitch setting, and the second propeller has a second blade pitch setting that is different from the first blade pitch setting.

5. The propulsion system according to claim 1, characterized in that: The first propeller has a shorter blade length than the second propeller; and The first propeller has a higher blade pitch setting than the second propeller.

6. A propulsion method, comprising: Provide the first propeller; Provide a second propeller; A motor is provided, comprising: an electromagnetic field transmitter coupled to a first propeller; and an electromagnetic field receiver coupled to a second propeller, wherein the electromagnetic field transmitter emits an electromagnetic field and responds to the electromagnetic field: The electromagnetic field receiver and the second propeller rotate in the first rotation direction; and The electromagnetic field emitter and the first propeller rotate in opposite second rotational directions; and The method further includes providing at least one of the following: A first mechanical coupling mechanically reorients the direction of rotation between the electromagnetic field receiver and the second propeller, such that the first propeller and the second propeller are not on the same axis; or A second mechanical coupling mechanically reorients the direction of rotation between the electromagnetic field emitter and the first propeller, such that the first propeller and the second propeller are not on the same axis.

7. The propulsion method according to claim 6, characterized in that: The method is performed by a vertical takeoff and landing vehicle; and The first propeller and the second propeller rotate about a substantially vertical axis of rotation.

8. The propulsion method according to claim 6, characterized in that, The first propeller has a first blade length, and the second propeller has a second blade length different from the first blade length.

9. The propulsion method according to claim 6, characterized in that, The first propeller has a first blade pitch setting, and the second propeller has a second blade pitch setting that is different from the first blade pitch setting.

10. The propulsion method according to claim 6, characterized in that: The first propeller has a shorter blade length than the second propeller; and The first propeller has a higher blade pitch setting than the second propeller.

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