DUAL ROTOR SYSTEM

Abstract

A contra-rotating dual rotor system may be driven by an electric motor disposed outside of the rotor system. A first rotor may be driven by a drive shaft protruding out from the front (or top) of the motor. A second rotor, mounted to the front of the motor, may be driven by the motor housing itself, via an extension of the motor housing which is coaxial with the drive shaft.

Claims

1. Dual rotor system comprising: a motor comprising a housing and a first output shaft (or rotor) extending from a front (top) end of the motor; and an extension of the housing extending from the front end of the motor, said extension being coaxial with the output shaft and functioning as a second output shaft (or rotor).

2. The dual rotor system of claim 1, further comprising: a first propeller (rotor) driven by the first output shaft, in a first direction; and a second propeller (rotor) driven by the second output shaft, in a second direction opposite to the first direction; wherein, when the motor is powered, the rotors rotate in opposite directions.

3. The dual rotor system of claim 1, wherein: the two rotors are disposed on the same end of the motor.

4. The dual rotor system of claim 1, wherein the motor is an electric motor, and further comprising: slip rings (conductive tracks) disposed on an exterior of the motor housing; brushes cooperating with (contacting) the slip rings, and receiving electrical power from an external source to power the electric motor.

5. The dual rotor system of claim 1, further comprising: at least one bearing disposed about the motor housing to support the motor with respect to a fixed external structure (such as airframe or pylon).

6. The dual rotor system of claim 1, further comprising: a universal joint disposed between the motor and the rotors to allow the rotors to tilt.

7. The dual rotor system of claim 6, wherein: the first and second output shafts are relatively long, and the universal joint is disposed relatively close to the rotors.

8. A flying machine incorporating the dual rotor system of claim 1.

9. The dual rotor system of claim 1, further comprising: mass added to one or both of the rotors (or propellers) so their moments of inertial are equal.

10. The dual rotor system of claim 1, further comprising: means for applying braking forces selectively to the rotors.

11. The dual rotor system of claim 1, wherein: bearings of equal size are mounted to support both the inner and outer rotors to a fixed external structure (such as airframe or pylon).

12. The dual rotor system of claim 1, wherein: bearings of equal quantity are mounted to support both the inner and outer rotors to a fixed external structure (such as airframe or pylon).

13. A method of driving contra-rotating propellers, comprising: providing an electric motor comprising a housing and a first output shaft extending from a front (top) end of the motor; and an extension of the housing extending from the front end of the motor, said extension being coaxial with the output shaft and functioning as a second output shaft; disposing propellers on the first and second output shafts; and powering the motor.

14. The method of claim 13, further comprising: adding mass to one or both of the rotors (or propellers) so their moments of inertial are equal.

15. The method of claim 13, further comprising: applying braking forces selectively to the rotors.

16. The method of claim 13, further comprising: mounting bearings of equal size to support both of the rotors to a fixed external structure (such as airframe or pylon).

17. The method of claim 13, further comprising: mounting bearings of equal quantity to support both of the rotors to a fixed external structure (such as airframe or pylon).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Reference will be made in detail to embodiments of the disclosure, non-limiting examples of which may be illustrated in the accompanying drawing figures (FIGs). The figures may generally be in the form of diagrams. Some elements in the figures may be exaggerated, others may be omitted, for illustrative clarity. Some figures may be in the form of diagrams.

[0022] Although the invention may be described in the context of various exemplary embodiments, it should be understood that it is not intended to limit the invention to these particular embodiments, and individual features of various embodiments may be combined with one another. Any text (legends, notes, reference numerals and the like) appearing on the drawings are incorporated by reference herein.

[0023] FIG. 1 is a diagram, in cross-sectional view, of a dual rotor motor system, according to an exemplary embodiment of the invention.

[0024] FIG. 2 is a diagram, in cross-sectional view, of the contra-rotating propeller arrangement of JP 2012011990.

DETAILED DESCRIPTION

[0025] Various embodiments (or examples) may be described to illustrate teachings of the invention(s), and should be construed as illustrative rather than limiting. It should be understood that it is not intended to limit the invention(s) to these particular embodiments. It should be understood that some individual features of various embodiments may be combined in different ways than shown, with one another. Reference herein to one embodiment, an embodiment, or similar formulations, may mean that a particular feature, structure, operation, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Some embodiments may not be explicitly designated as such (an embodiment).

[0026] The embodiments and aspects thereof may be described and illustrated in conjunction with systems, devices and methods which are meant to be exemplary and illustrative, not limiting in scope. Specific configurations and details may be set forth in order to provide an understanding of the invention(s). However, it should be apparent to one skilled in the art that the invention(s) may be practiced without some of the specific details being presented herein. Furthermore, some well-known steps or components may be described only generally, or even omitted, for the sake of illustrative clarity. Elements referred to in the singular (e.g., a widget) may be interpreted to include the possibility of plural instances of the element (e.g., at least one widget), unless explicitly otherwise stated (e.g., one and only one widget).

[0027] In the following descriptions, some specific details may be set forth in order to provide an understanding of the invention(s) disclosed herein. It should be apparent to those skilled in the art that these invention(s) may be practiced without these specific details. Any dimensions and materials or processes set forth herein should be considered to be approximate and exemplary, unless otherwise indicated. Headings (typically underlined) may be provided as an aid to the reader, and should not be construed as limiting.

[0028] FIG. 1 is a cross-sectional view of a dual rotor motor system 100, according to an exemplary embodiment of the invention. The system 100 generally comprises an electric motor 110 with a housing 112. The system further comprises two rotors (or propellers) 120 and 122.

[0029] A drive shaft 114 is shown exiting the front (or top) end of the motor 110. The rotor 120 is connected in any suitable manner (such as with a hub, not shown) to the drive shaft 114.

[0030] An extension 116 of the motor housing is shown projecting from the front (or top) end of the motor 110. The rotor 122 is connected in any suitable manner (such as with a hub, not shown) to the extension.

[0031] The drive shaft 114 may pass through a hub for the rotor 122.

[0032] The extension 116 may be coaxial with the drive shaft 114. The extension 116 may extend a distance (D1) from the front of the motor. The drive shaft 112 may extend a distance (D2) from the front of the motor. The distance D2 may be greater than the distance D1, which would put the rotor 120 ahead of (or atop) the rotor 122. The distances D1 and D2 may be such that the motor 110 is disposed at a substantial distance from the two rotors.

[0033] In use, when the motor is powered up, the rotors 120, 122 may turn in opposite directions from one another. For example, the front (or topmost) rotor 120 (and the drive shaft 114) may turn in a clockwise (CW) direction, whilst the rear (or bottom) rotor 122 (and the motor housing 112) may turn in a counter-clockwise (CCW) direction. Such contra-rotation of rotors has several advantages, which are well known and which have been mentioned elsewhere. The two rotors 120 and 122 may be referred to as a rotor system (or propeller system, or thrust system).

[0034] The motor 110 may be mounted to a fixed support structure 130, such as an airframe of an aircraft, in a manner that allows the motor itself to rotate (spin about its axis) relative to the fixed structure. (In the figure, the fixed structure is shown spaced apart from the motor, for illustrative clarity.) To this end, bearings 132 and 134 may be provided between the fixed structure and the motor housing 112, supporting the motor housing. One such bearing 132 may be disposed towards a front end (top) of the motor. Another such bearing 134 may be disposed towards the back end (bottom) of the motor. With the two bearings, located as shown (and described), this will ensure that the motor remains fixed in position with respect to the fixed structure, while being able to rotate freely.

[0035] In order to power the motor, two or three slip rings (or power rails) 136 may be disposed on an exterior surface of the motor, and corresponding two or three brush assemblies 138 may be disposed in a suitable manner on the support structure 130. (A single brush assembly may comprise a single brush, but better if it has two or more brushes contacting its corresponding slip ring.) Two slip rings and brushes are shown, such as for 2-phase AC or for DC operation of the motor. Three slip rings and brushes may be required for 3-phase operation. The motor housing itself may be ground (earth).

[0036] The slip rings should be electrically insulated from the motor housing, and may be mounted on spokes or the like so that they are located a bit radially outward from the outer surface of the motor housing. This would enable one slip ring assembly to be used with motors of different sizes (diameters), without changing the size of the brush assembly.

[0037] Internal electrics of the motor are omitted, for illustrative clarity. A braking mechanism (if any) is omitted, for illustrative clarity. External controls for monitoring and controlling the operation of the motor are also omitted. The propellers (or rotors) are exemplary of any driven devices, such as turbine blades and the like. Control rods (if any) for varying the pitch of the blades are not shown.

[0038] The combined motor and rotor system disclosed herein may be useful for providing lift to flying machines such as helicopters or drones. Other applications which utilize the displacement of fluid for propulsion or to propel fluids where the benefits of torque balance provides advantages such as boats, submarines, torpedoes, wind turbines, hydroelectric generators, submerged pumps, ceiling cooling fans may also benefit from the techniques disclosed herein.

APPENDICES

[0039] APPENDIX 1, incorporated by reference herein, is an illustrated presentation describing (i) prior art, (ii) the innovation disclosed herein, (iii) embodiment example, (iv) effects of breaking (sic) the rotors (v) car embodiment, (vi) additional notes.

[0040] Note: breaking should read braking.

[0041] Some of the text of APPENDIX 1 may be presented/paraphrased here:

[0042] A conventional electric motor has an output shaft (rotor 1) which extends from the front end of the motor and which spins in one (a given) direction. Left unrestrained, the motor housing would tend to rotate in the opposite direction from the rotor.

[0043] Step 1a. provide conductive tracks (rails) on the exterior of the motor housing, and external brushes to get power into the (electric) motor. This may be akin to a commutator/brush arrangement.

[0044] Step 1b. extend the front of motor housing to provide a second output shaft (rotor 2) coaxial with and surrounding rotor 1. With the motor housing (and rotor 2) left unrestrained, the motor housing (and rotor 2) would tend to rotate in the opposite direction from the rotor. Alternatively, the rear of the housing could be extended to provide the second, contra-rotating, collinear (coaxial) rotor. Rather than extending, a separate piece (collar) may be mounted to the housing.

[0045] Step 2. provide external bearings on the motor housing, so that it may be mounted to (or in) a fixed structure, such as an airframe, or a wind turbine pylon.

[0046] With contra-rotating coaxial rotors, braking (breaking) of one rotor may cause a net torque for controlling the yaw of the aircraft.

[0047] APPENDIX 2, incorporated by reference herein, shows the dual rotor system of the present invention in a vertical orientation with the contra-rotating rotors (propellers) disposed above a user who is standing on a platform representative of (for example) a helicopter. There are 3 figures.

[0048] View A shows the rotors disposed above the user, and the motor is disposed much lower, resulting in a low center of gravity.

[0049] View B shows the propeller force (top large arrow), the weight force (bottom large arrow), and the center of gravity. The low center of gravity results in greater stability, versus top heavy (unstable)

[0050] View C-1 shows that the incorporation of a universal joint (or pivot) in the drive allows for the rotors to easily be tilted, in all directions, which is necessary for directing the flight path of the helicopter. Here, the motor swings (tilts) in a direction opposite from that of the rotor.

[0051] View C-2 shows that the incorporation of a universal joint in the drive allows for the rotors to easily be tilted, in all directions, which is necessary for directing the flight path of the helicopter. Here, the motor is not tilted.

[0052] View D

[0053] The torque () applied to each rotor axis is the product of the moment of inertia (I) and the angular acceleration ().

=I

[0054] The moment of inertia is a quantity expressing a body's tendency to resist angular acceleration. It is the sum of the products of the mass of each particle in the body with the square of its distance from the axis of rotation. Since both axes rotate about the same axis it is expected that the internal and external rotors would have differing moments of inertia based on the mechanics and selection of motor magnets and windings configurations.

[0055] Since the torque generated by the motor is split equally between the outer (o) and inner (i) rotors the toque equation may be expressed as follows:

.sub.o=I.sub.o.sub.o .sub.i=I.sub.i.sub.i

I.sub.o.sub.o=I.sub.i.sub.i

[0056] If the internal rotor and external rotor moment of inertia differ then during motor start up, as the rotors spin-up under motor force, they would experience different accelerations. So when acceleration reaches zero and the motor is not changing power rates, each rotor would have a different rotational speed.

[0057] Different rotational speed would lead to difference in forces (downward, drag, etc) generated by the internal and external propellers. This force differential would lead to net forces acting on the system and would require other mechanisms for balancing them out.

[0058] However, equalizing the moments of inertia of both rotors would lead to both rotors experiencing and reaching the same rotational speeds. This would eliminate the unequal forces generated by the propellers due to the differing rotational speeds.

[0059] Mass may be added to one or both of the rotors (or propellers) so that their moments of inertial are equal.

[0060] View E

[0061] Selectively applying braking forces selectively to internal and external rotors to generate net rotation whereby .sub.o.sub.i, and causing the system to rotate about itself.

[0062] 114=internal rotor

[0063] 116=external rotor

[0064] View F

[0065] Further improvements in system torque equalization may be achieved by applying bearings of equal size and quantity to each of the inner and outer rotors, thereby distributing and balancing the bearing drag forces to both rotors so D.sub.i=D.sub.o.

[0066] 114=inner rotor

[0067] 116=outer rotor

Distinguishing Over JP 2012011990

[0068] This publication (JP 990) shows a thrust device that can easily produce machines capable of vertical takeoff and landing.

[0069] As best understood, FIG. 2 shows a contra-rotating propeller, as follows:

[0070] 1 motor having a field case (housing)

[0071] 2 output (drive) shaft coming out of the front (top) of the motor

[0072] 3 first propeller (or rotor) disposed on the front of the motor, driven by the drive shaft 2

[0073] 3a hub for the first propeller 3

[0074] The drive shaft rotates in one direction while the motor case rotates in an opposite direction.

[0075] 4 second propeller (or rotor) disposed on the back (bottom) of the motor

[0076] 4a hub for the second propeller 4

[0077] 5a shaft mounted to the motor, at the back of the motor

[0078] 6 bearings supporting the shaft

[0079] 7 electrodes attached to the shaft

[0080] 8 power supply brushes attached to the bearing case

[0081] In a vertical orientation, the front of the motor will be the top of the motor, and the back (or rear) of the motor will be the bottom of the motor.

[0082] JP 990 has a motor, and two contra-rotating propellers. A first propeller is attached to the output shaft of the motor, and rotates in a first direction, at the front of the motor. A second propeller is attached to the motor housing, and rotates in a second direction, at the rear of the motor. Applicant similarly has a motor, and two contra-rotating propellers. A first propeller is attached to the output shaft of the motor, and rotates in a first direction, at the front of the motor. A second propeller is attached to the motor housing, and rotates in a second direction, also at the front of the motor.

[0083] JP 990 locates the motor between the two contra-rotating propellers. One propeller is disposed at the front of the motor, the other propeller is disposed at the rear of the motor. The motor is therefore in the airflow between the two propellers. Applicant locates both of the two contra-rotating propellers at one end (the front) of the motor. In this manner, the motor does not restrict (or otherwise interfere) with the airflow.

[0084] JP 990's motor is disposed within the contra-rotating propeller system. In a vertical orientation (such as for a helicopter) this results in an undesirably high center of gravity Applicant's motor is disposed away (distant) from the contra-rotating propeller system, resulting in a desirably low center of gravity. Applicant's motor is position independent, meaning that it can be located away from the rotors.

[0085] Locating the motor between the rotors is also an obstacle, for example, to having pitch control rods (such as for control rods, cyclic and collective) extending to the front rotor. Locating the motor remote from the propeller system enables control rods and the like to be disposed in the space between the two rotors.

[0086] Locating the motor between the rotors may also limit the size (or impose some gnarly design restraints) on the second rotor 4. Applicant's design does not suffer from these drawbacks.)

[0087] Locating the motor between the rotors also means that in order to tilt the propellers (rotor system), it is necessary to tilt the motor with the rotor.

[0088] JP 990 supports the motor by a shaft 4 extending from the back of the motor. The motor is not well supported. This cantilevered support is not robust. Applicant's motor is well supported by bearings 134 disposed directly on the motor casing.

[0089] JP 990 powers the motor via slip rings and brushes (electrodes 7) located on a shaft 5 mounted to the motor, at the back of the motor. Applicant's slip rings 136 are disposed about the motor housing, resulting in a larger diameter. A larger diameter slip ring, disposed on the outside of the motor housing may be better than a smaller one (as in JP 990) because (i) traditional motor configurations have the power connections on the case (housing) and not on the the internal rotor and (ii) larger slip rings allow for higher power transfers since the perimeter (circumference, hence surface area) is larger allowing for more cooling of the surface of the slip ring(s) between brush passes. Alternatively, Applicant could use the slip ring/brush arrangement of JP 990.

[0090] While the invention(s) has/have been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention(s), but rather as examples of some of the embodiments. Those skilled in the art may envision other possible variations, modifications, and implementations that are also within the scope of the invention(s), based on the disclosure(s) set forth herein.