Magnetically geared DC brushless motor using separate winding sections

Embodiments of the disclosure provide a magnetically geared DC brushless motor and method of using the same. The motor may use multiple separately terminable winding sections wrapped around motor armatures. At least one of the separately terminable winding sections may have windings around adjacent armatures. The motor may be configured to activate certain winding sections to control the velocity and torque outputs of the motor. The winding sections may include copper wire, and the separate winding sections may have wires of different gauge sizes. Various winding sections may be powered by separate voltage sources. Various winding sections may be powered by separate pulse-width modulation voltage sources. The motor may be configured to increase and/or decrease the voltage of a winding section or combination of sections to prepare for the activation or deactivation of another winding section or combination of winding sections.

BACKGROUND

Permanent magnet brushless motors may be used to supply motive power to a variety of systems, including electric vehicles and drone aircrafts. These systems can perform in varying environments, in which the motor may at times operate at relatively higher speeds or carry relatively heavy loads, as the case may be. It is therefore desirable for permanent magnet brushless motors to be able to change their torque and speed outputs to satisfy performance requirements. By way of example, some automobiles have confronted this issue by implementing mechanical gears to accomplish a variety of torque and speed outputs. This solution, however, tends to be costly, inefficient, and impractical in the electrical motor industry, which demands efficiency, reduced weight, and size.

Switches may be used to change a motor's circuitry and thus depart from the typically linear, fixed nature of the relationship between torque and speed characteristics. These methods introduce several problems. One problem is that switch failure may cause the motor to short circuit. Additionally, there is typically a brief inactivity period between switching states, which causes a delay in the motor's operation between states. Benefits that may be associated with rapidly switching between different states to achieve intermediate effects, however, may be limited by the speed at which the circuitry can switch from one state to another. Finally, the circuitry of the windings can be changed in a variety of configurations to yield a variety of motor characteristics, but each variation is typically powered by the same voltage supply. This limits a motor's ability to access a higher supply voltage for acceleration purposes.

BRIEF SUMMARY OF THE DISCLOSURE

In view of the above-described and other shortcomings in conventional DC brushless motors, there exists a need for direct current brushless motors capable of variable torque and speed characteristics by switching between separately terminable winding sections. In particular, there exists a need for a brushless motor with multiple layers of separately terminable winding sections, where the motor is capable of switching between the separate winding sections in order to achieve desired torque and speed outputs.

The present disclosure relates generally to electric motors. More particularly, the present disclosure relates to a magnetically geared brushless motor capable of switching between separately terminable winding sections, for example, to achieve desired torque and speed outputs during the operation of the motor.

The present disclosure provides a brushless motor with multiple layers of separately terminable winding sections, where the motor is capable of switching between the separate winding sections in order to achieve desired torque and speed outputs. In one or more aspects of the present disclosure, a brushless direct current motor includes a plurality of armatures mounted to a stator. The motor also includes a plurality of separately terminable winding sections. Each of the winding sections is wrapped around at least one of the armatures, and at least one of the winding sections includes a winding wrapped around two or more adjacent armatures of the plurality of armatures. The motor further includes a plurality of electronic switch devices. Each of the electronic switch devices is connected to at least one of the winding sections. In certain implementations of these one or more aspects, which may be generally applicable but are also particularly applicable in connection with any other implementation herein, the electronic switch devices are separately terminable.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to a method and device for a magnetically geared direct current brushless motor capable of achieving desired torque and speed characteristics contemporaneously while the motor is in operation. In various deployments described herein, the disclosure involves a direct current brushless motor with multiple separately terminable winding sections wound around the motor armatures. The separately terminable winding sections are activated, either individually, simultaneously, or in a combination thereof, to control the motor velocity constant (Kv) of the motor. The device may be configured in terms of one or more of materials, characteristics, sizes, orientations, and attachment features, such that efficiency may be increased and the torque and speed characteristics of the motor may be made suitable for an intended purpose depending on varying environmental/loading conditions and/or use of the motor.

In embodiments of the disclosure, permanent magnet brushless motors may include multiple armatures mounted around, for example, a circular stator. Copper windings may be wound around the armatures and may act as electromagnets upon being energized with electrical current. An electronic switch controller may receive a direct current signal and transform it in to a three-phase electrical signal to selectively energize a given phase of connected copper windings. As a given phase of copper windings is energized, the copper phase of copper winding may act as a magnetic pole, motivating the permanent magnet to turn towards the magnetic pole. The electronic switch controller may then switch phases, for example, by turning off the energized phase of copper windings and turning on the next phase of adjacent copper windings. This may further motivate the permanent magnet rotor to turn towards the next phase of copper windings. This process may be iterated rapidly in some cases, and for relatively long periods, through the three phases of copper windings to create constant rotational motion of the rotor.

Permanent magnet brushless motors, according to embodiments of the present disclosure, may generally exhibit linear torque and speed characteristics. The rotation of the permanent magnet rotor relative to the copper windings may produce a voltage counter to the supply voltage in proportion to the rotor's rotational speed. This counter-electromotive force, or back EMF, may increase as the speed of the motor increases. The torque output of a permanent magnet brushless motor is in some cases at a maximum when it is loaded to the point where it is unable to rotate because there is no back electro-magnetic field (EMF). Conversely, the torque output of a permanent magnet brushless motor is in some cases at a minimum when it rotates freely without any load, because the back EMF is at a maximum. The generally linear relationship between a motor's speed and torque characteristics may be described by the motor velocity constant, Kv. Certain design parameters of a permanent magnet brushless motor can be modified in accordance with teachings present disclosure, to control the effective Kv. In embodiments, these parameters include the number of loops of wire around an armature, the gauge of wire, and the number of armatures wound with copper windings, or poles. As the number of poles increases, the torque capabilities of the motor may be increased, for example, due to increased magnetic flux. As the number of poles decreases, the motor may be able to achieve higher speeds, in some cases at the expense of torque capabilities.

The details of some example embodiments of the methods and devices of the present disclosure are set forth in this description and in some cases, in other portions of the disclosure. Other features, objects, and advantages of the disclosure will be apparent to one of skill in the art upon examination of the present disclosure, description, figures, examples, and claims. It is intended that all such additional methods, devices, features, and advantages be included within this description (whether explicitly or by reference), be within the scope of the present disclosure, and be protected by one or more of the accompanying claims.

FIG. 1is a diagram of an example embodiment of the disclosure depicting brushless permanent magnet motor100with three separately terminable winding sections,25,30, and35. Motor armature20, along with the plurality of armatures around motor100, may be fixed to base plate60and mounted vertically to motor stator15. In this illustration, the motor is fixed to attachment arm40. By way of example, this arrangement may be suitable for using motor100as a single rotor on a drone copter aircraft. It will be appreciated, however, that motor100may be attached, fixed, or constrained in any configuration suitable for an intended purpose. Separately terminable winding sections25,30, and35are shown as being arranged vertically relative to one another. Separately terminable winding section25(shown for example as a bottom section inFIG. 1), separately terminable winding section30(shown for example as a middle section inFIG. 1), and separately terminable winding section35(shown for example as a top section inFIG. 1), each include multiple windings wound around the plurality of armatures. In embodiments, it will be appreciated that the present disclosure includes various geometries and configurations of motor100, for example, outrunner, inrunner, and so on.

FIG. 2Ashows that, for example, each horizontal winding section of the motor100may be separate and distinct from the other sections. Winding section30(middle) may have a relatively larger wire gauge and a relatively lesser number of windings around the armatures in some cases. In embodiments, this may provide winding section30with different output characteristics than, for example, winding sections25and/or35. Winding sections25,30, and35as shown in figures of the present disclosure, may be visibly separated in order to demonstrate that they are independent of one another. Upon studying the present disclosure, however, one of skill in the art will appreciate that there is no requirement that winding sections25,30, and/or35be physically separated from each other in any particular way. Nevertheless, each winding section25,30,35may typically be its own electrical circuit that may be independent (e.g., from an electrical perspective) of the other winding sections. For example, with reference toFIG. 8, each winding section25,30,35may in some cases receive a separate supply voltage. This may be done, in some cases, using a separate circuit for one or more of winding sections25,30, and/or35to present independent and/or different voltages winding sections25,30, and/or35. In some cases, a single such circuit may drive more than one winding section25,30, and/or35with the same (electrically coupled) line. In embodiments, a single such circuit may be used to generate more than one independent and/or different voltage to respectively drive winding sections25,30, and/or35. In embodiments, a pulse-width modulation (PWM) circuit may be coupled on the one hand to the output of a voltage step down circuit and on the other hand to one or more of winding sections20,25, and/or30.

In embodiments, the voltage supply line may be coupled to the PWM circuit driving one or more of the winding sections (e.g., winding sections20and25), while the voltage supply line may also be coupled (e.g., in parallel) to other of the winding sections (e.g., winding section30) through a voltage step down circuit. In some cases, the modification to the voltage supply source effected by the (e.g., step down) circuit(s) may be made variable, adaptable, and/or configurable, such that the voltage supplied to one or more winding section may be modified on the fly, including in some cases relative to the other winding sections. In some of these instances, the thickness of a particular winding section may be configured for the winding section to operate on a particular supply voltage or range of supply voltages. Thus, in example implementations, the embodiments provided inFIG. 8and described with reference thereto, as well as additional embodiments described herein, may improve a motor's ability to access a different supply voltages (e.g., for acceleration purposes). Additionally,FIG. 2Aillustrates a small air gap that may be present between permanent magnet rotor10and stator15. This air gap may allow for free rotation motion of the rotor. As rotor10spins, rotor10may transmit rotational energy to motor shaft5.

FIG. 2Bis illustrates example embodiments involving motor100, and in particular depicts a top view of permanent magnet rotor10and motor shaft5. Rotor10may include permanent magnets that alternate in polarity. For example, permanent magnet45may be a south magnetic pole, and adjacent permanent magnet50may be a north magnetic pole. The polarity of the permanent magnets45,50, etc. may alternate around rotor10. The number, size, strength, and orientation of permanent magnets45,50, etc. fixed to rotor10in some cases depends on at least the number armatures, and particular configuration of multiple separate winding sections, and/or the intended use of the motor.

The assembly of motor100in accordance with example embodiments is shown inFIG. 3, which further illustrates armature20, along with an array of what in some cases may be similar armatures, mounted to base plate60. Separate winding sections25,30, and35may be wrapped (e.g., horizontally) around armatures20and arranged vertically relative to one another. Each winding section25,30, and35may include horizontal windings around each of the plurality of armatures20. Winding sections25,30, and35may also be wound vertically, at an angle, or in any other orientation depending on the performance conditions and needs of a particular motor application.

Bottom winding section25is further from permanent magnet rotor10relative to middle winding section30and top winding section35. Accordingly, bottom winding section25may have less of an interaction with the magnetic fields that may be present in conjunction with the permanent magnets (e.g.,45,50, etc.) fixed on rotor10. In some cases, an optional bottom rotor55, which in some cases may be substantially similar or identical to the top rotor10, may be mounted and fixed to transmit rotational energy to shaft5. In embodiments, rotors10and55may be mounted vertically on both sides of winding sections25,30, and35. In example implementations, any other orientation may be used with respect to rotors10and/or55, including, but not limited to an in-runner orientation, where rotor10and/or55is within the core of winding sections25,30, and/or35, or an out-runner orientation, where rotor10and/or55surrounds the outside of the winding sections25,30, and/or35.

FIG. 4Adepicts an example winding configuration of bottom winding section25(with reference by way of example toFIG. 2A). Winding section25in this case includes three phases, A, B, and C, identified inFIG. 4Aas25a,25b, and25c, respectively. Each of phases25a,25b, and25cmay involve a number of distinct coils wrapped around one or more armatures. For example, phases25a,25b, and/or25cmay involve windings of four coils of enameled copper wire wound around four of the motor armatures. In the example shown inFIG. 4A, phase25aincludes windings of the four coils, A1, A2, A3, and A4. Each of coils (e.g., A1-A4) of a given phase may be separated by two coils of the other two phases. For example, the coils of phase25a(e.g., A1-A4) are shown inFIG. 4Ato be separated by one coil of phase25b(e.g., B1-B4) and one coil of phase25c(e.g., C1-C4). When a given phase25a,25b, and/or25cis energized by an electronic switch controller, each of the phase's coils may act as an electromagnet, exerting magnetic force on a permanent magnet rotor (e.g., rotor10with reference by way of example toFIG. 3). As the permanent magnet rotor turns toward the coils of the energized phase, the electronic switch controller may switch that phase off and activate the next adjacent phase, further motivating the rotor to turn. This process may be iterated, in some cases rapidly and continuously, thus accelerating the rotor to a rotational velocity that may be constant. The rotation of the motor therefore can depend in part on the speed at which the electronic switch controller can switch between phases, for example, phases (25a,25b,25cshown by way of example inFIG. 4A).

The winding configuration of bottom winding section25may in some cases be identical or substantially similar to the winding configuration of the middle winding section30. In example embodiments, bottom and middle winding sections25and30may include three phases, with each phase including windings of four coils wrapped around the motor armatures. Referring back toFIG. 3, middle winding section30may consist of wire of a relatively larger gauge and have a relatively lesser number of windings around each of the armatures than, for example the bottom winding section25. As such, the wire properties and the winding arrangement of the middle winding section30may provide for a higher Kvthan, for example, bottom winding section25, even though winding sections25and30may share an at least similar winding configuration around the motor armatures. With a higher Kv, middle winding section30may be able to achieve higher speeds than bottom winding section25, but may in some cases have diminished torque capacity.

FIG. 4Bdepicts an example implementation of a winding configuration that may be used for the top winding section35in accordance with embodiments of the present disclosure. As described above, in the winding sections of the bottom winding section25and middle winding section30depicted inFIG. 4A, each phase may include four coils which are individually wrapped around each of the armatures. Top winding section35may likewise have three phases,35a,35b, and35c. Each of phases35a,35b, and35cmay have two effective coils, which may be formed by connecting the windings of adjacent armatures in pairs. For example, phase35amay include windings A1and A2, where both A1and A2are formed by a connection (e.g., an uninterrupted connection) between the windings of a pair of adjacent armatures. The pair of connected, adjacent windings may be wound in the same direction in order to exhibit similar electromagnetic field properties. One benefit of this configuration is that the effective Kvof winding section35may be improved, for example because the number of switches between phases per revolution made by the electronic switch controller associated with winding section35may be reduced relative to the switch control for the bottom and middle winding sections (e.g.,25and30, with reference by way of example toFIG. 3).

Referring again, by way of example, to bottom winding section25shown inFIG. 4A, in order for the rotor (e.g., rotor10) to complete one revolution, the electronic switch controller may need to cycle through each of phases25a,25b,25cfour times. The four coils (e.g., A1-A4) of phases25a,25b,25cmay each be wrapped around an individual armature. Thus, the electronic switch controller may need to switch twelve times in order for the rotor to make one revolution. Generally, the time associated with one revolution of a motor may be limited by the time it takes for the electronic switch controller to make the number of switches that may be needed for one revolution (e.g., 12 switches in this particular instance).

Middle winding section30and the associated configuration may have similar properties, because, as mentioned middle winding section30may use a similar winding configuration as bottom winding section25. For example, while middle winding section30may in some cases use wire of a larger gauge and/or may have less windings around each armature, embodiments of winding section30may still utilize three phases with four coils per phase. In the top winding section depicted inFIG. 4B, however, coils of adjacent armatures are connected together to form pairs of connected coils.

Top winding section35may include a similar number of phases (e.g., three phases35a,35b,35c, referencingFIG. 4Bby way of example) vis-à-vis bottom and/or middle winding sections25and/or30. Nevertheless, in embodiments, each phase35a,35b,35cmay include a different number of effective groups of coils vis-à-vis bottom and/or middle winding sections25and/or30. For example, two effective groups of coils (e.g., A1, A2) may be used (referencingFIG. 4B) in conjunction with top winding section35. In some such embodiments, connecting the windings of adjacent armatures may enable the electronic switch controller to make fewer switches per revolution, thus increasing the speed capacity of the motor.

The connection of (e.g., adjacent) coils according to embodiments of the present disclosure is further illustrated inFIG. 4C. As shown inFIG. 4C, in embodiments, rather than connecting individual armature windings in pairs (e.g., as shown inFIG. 4B), the windings may be physically wrapped around adjacent armatures. The winding configurations shownFIG. 4Cmay be subject to the switching speed/frequency of the electronic switch controller, as described in connection withFIG. 4B, because both configurations to some extent utilize a number switches per revolution. Nevertheless, the winding configuration ofFIG. 4Bmay in some cases utilize more magnetic flux, for example, because the windings may be wrapped substantially (and/or entirely) around each of the armatures, thus reducing gaps between the armatures.

FIG. 5Ais an example embodiment of the disclosure200depicting the separately terminable winding sections and the motor armatures isolated from the rotor and stator assembly. The separate winding sections,25,30, and35, may be wound around the motor armatures20. The bottom winding section25and middle winding section30may be configured in a winding configuration described above with reference toFIG. 4A. The top winding section35may be configured in a winding configuration described above with reference toFIG. 4B.

FIG. 5Billustrates another embodiment of the disclosure. Referring toFIG. 5B, separately terminable winding sections and motor armatures may be isolated from the rotor and stator assembly. The separate winding sections,25,30, and35, may be wound around the motor armatures20. The bottom winding section25and middle winding section30may be configured in a winding configuration as described above with reference toFIG. 4A. The top winding section35may be configured in the winding configuration as described above with reference toFIG. 4C.

FIG. 6illustrates an example electrical winding configuration600with three separately terminable winding sections. Each separately terminable winding section may be connected to a separate electronic switch controller. The electronic switch controllers may be connected to a common ground70. As illustrated, the bottom winding section600amay be connected to the electronic switch controller600a′; the middle winding section600bmay be connected to the electronic switch controller600b; and the top winding section600cmay be connected to the electronic switch controller600c′. Connecting each of the winding sections to a separate electronic switch controller allows for added versatility in selecting different speed controllers for each winding section based on the desired performance of each separate winding section. The electronic switch controllers may receive power from power source75. In some examples, each winding section receives power from a separate power supply.

Within each separate winding section, the three phases may be electrically configured in wye or delta electrical winding configurations. For example, as illustrated inFIG. 6, bottom winding section600aand top winding section600cmay be configured in a wye configuration and middle winding section600bmay be configured in a delta configuration. Alternate configurations for each winding section (e.g., wye or delta) may be used as would be known in the art. Wye configurations may supply higher torque, but lower speeds, whereas delta configurations may supply lower torque, but higher speeds. The ability to switch between the configurations, in addition to switching the number of windings in each configuration as described with respect toFIGS. 4A-5C, enables control over the desired motor outputs with respect to torque and speed, similar to switching gears on a bicycle or car.

Various embodiments of the disclosure may employ different numbers of armatures and winding patterns, with various configurations and numbers of separate winding sections in any orientation, and any configuration of connected groups of adjacent armature windings. For example, one example may include a brushless permanent magnet motor with twenty-four armatures and four separate winding sections. The first separate winding section may have three phases, each phase having eight coils around eight individual armatures. The second separate winding section may have three phases, each phase having four coils, with each coil consisting of connected windings of two adjacent armatures. The third separate winding section may have three phases, each phase having two coils, each coil consisting of connected windings of four adjacent armatures. The fourth separate winding section may have three phases, each phase having only one coil, where each coil consists of connected windings of eight adjacent armatures. It will be appreciated, that other numbers of separate winding sections may be employed with different numbers of phases and/or coils. Each separately terminable section may be configured the same or differently, for example, to further have a particular electrical configuration, either delta or wye, a particular number of windings around each armature, a particular wire gauge, and a particular power supply. Each of the electronic switch controllers may be selected based on their switching abilities. It is also possible that a single electronic switch controller activates multiple separate winding sections at once. The present disclosure allows for other possible combinations as would be known in the art.

Embodiments of the disclosure function similarly to a magnetically geared motor because of the ability of the motor to switch between the separate winding sections. The separate winding sections have varying magnetic properties that yield selectable torque and output characteristics. The process of switching between the separate winding sections may be automatic (e.g., controlled by sensors used to detect motor output, speed of the vehicle, etc.) or manual.

FIG. 7is a graph illustrating example torque and speed characteristics of a motor following selection of different winding sections and configurations of an example embodiment of the disclosure. For example, plot80may represent torque and speed characteristics of the motor when the bottom winding section is activated. A possible desired time to switch between the bottom winding section and middle winding section85may be represented by the intersection point of the with plot80′. Likewise, a possible desired time to switch between middle winding85section and top winding section90may be at the intersection point with plot85′. By measuring the rotations per minute (RPM) of the motor using a Hall-effect sensor, tachometer, or other sensor as known in the art, programmed circuitry may automatically “change gears” by switching between winding sections. Transitions between the separate winding sections may also be manually controlled. There is no requirement that the winding sections be switched in any particular order. In some examples, aspects of the motor may be configured to function as a “brake,” and this may be done in some embodiments using a particular winding configurations. For example, one or more of the winding sections may be configured to achieve torque outputs in a direction opposite to the normal operating torque of the motor. Such winding sections may be inactive during the normal use motor, but may be activated to counter the motion of rotor to brake, slow down, or stop the rotor, depending on the level of the torque output applied by the winding section(s).

Other winding properties that may be selected to adjust the characteristics of the motor may include wire gauge, number of winding around the armatures, number of connected adjacent armatures, electronic controllers, and/or power supplies. Multiple winding sections may be operated simultaneously, or in various combinations, to achieve various desired results.

Using windings that are separately terminable may improve transition between different winding sections. For example, electric motors that enable switching between multiple winding configurations tend to experience a temporary inactivity during the switching state. Embodiments disclosed herein include electronic switch controllers (e.g., as illustrated inFIG. 6) which may be capable of pulse width modulation. If a user desires to switch from the middle winding section to the top winding section, the electronic switch controller may slowly ramp up the top winding section to prepare it to be fully activated. Once the switch from the middle winding section to the top winding section is made, the middle winding section may be slowly ramped down, rather than completely turned off. The ability to separately control the power of each winding section through pulse-width modulation may improve seamless switching sequences to mitigate the “jerking” effect associated with switching gears.

Various embodiments have been described with reference to specific example features thereof. It will be evident to one of ordinary skill in the art that various modifications and changes may be made to those embodiments without departing from the broader spirit and scope of the disclosure. The specification and figures are illustrative and should not be construed to limit or restrict the scope of the disclosure or the claims.