Variable flux bridge for electric motor rotors

Abstract

The present disclosure relates to a variable flux bridge for an electric motor rotor. A vehicle motor assembly is provided that includes a stator core, a rotor, and a bridge. The stator core defines a cavity. The rotor is disposed in the cavity and may include a channel defined between two magnets. The bridge is disposed in the channel to translate between at least a first position and a second position. The translation of the bridge adjusts the flux path from the rotor to the stator core based on the position of the bridge. The bridge may be made of ferromagnetic material. The vehicle motor assembly may also include a first non-magnetic guide and a second non-magnetic guide, the first non-magnetic guide being mounted on a first side of the channel at a substantially middle region of the channel, and the second non-magnetic guide being mounted on a second side of the channel at a substantially middle region of the channel.

Description

Technical Field

[0001] The present disclosure relates to an electric machine assembly for an electrified vehicle. Background Art

[0002] Technologies for extending driving range for electrified vehicles, such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), continue to improve. However, achieving these increased ranges generally requires higher power outputs from traction batteries and electric machines compared to previous BEVs and PHEVs and thermal management systems associated with the increased capabilities. Improving the efficiency between the stator core and the rotor of an electric machine can increase the power output of the electric machine. Summary of the invention

[0003] A vehicle motor assembly includes a stator core, a rotor, and a bridge. The stator core defines a cavity. The rotor is disposed in the cavity and includes a channel defined between two magnets. The bridge is disposed in the channel to translate between at least a first position and a second position. The translation of the bridge adjusts the magnetic flux path from the rotor to the stator core based on the position of the bridge. The bridge may be constructed of a ferromagnetic material. The vehicle motor assembly may also include a first non-magnetic guide and a second non-magnetic guide, the first non-magnetic guide being mounted on a first side of the channel at a substantially middle region of the channel, and the second non-magnetic guide being mounted on a second side of the channel at a substantially middle region of the channel. The non-magnetic guide may be constructed of a material having a low friction coefficient property to help facilitate translation of the bridge within the channel. Each of the non-magnetic guides may include a guide edge substantially parallel to a magnet edge of one of the adjacent magnets. The first position may be further defined as a stationary position, at which the centrifugal force generated by the rotation of the rotor is substantially zero, and the second position may be further defined as an effective shunting flux position. When the bridge is in the effective split flux position, the bridge is operable to control the flux path from the rotor to the stator core. The second position can be further defined as an effective split flux position, in which the bridge increases the width of the high permeability path through a portion of the rotor.

[0004] An electrified vehicle motor assembly includes a stator core, a rotor, a bridge, and a spring. The stator core defines a cavity. The rotor is disposed in the cavity and includes a channel located between a first magnet and a second magnet. The bridge is disposed in the channel for translation. The spring is disposed in the channel and is oriented to bias the movement of the bridge in a direction opposite to the direction of the centrifugal force generated by the rotation of the rotor. The spring can be adjusted based on the rotor torque speed specification and the rotor geometry to optimize the position of the bridge in the channel to control the amount of magnetic flux flowing from the rotor to the stator core. The spring constant of the spring can be selected based on the following equation: k = (mrπRPM 2 ) / (30x). The bridge and the channel may define a first air pocket on one side of the bridge within the channel, and may define a second air pocket on the other side of the bridge within the channel. The electrified vehicle motor assembly may also include a first non-magnetic guide and a second non-magnetic guide, the first non-magnetic guide being mounted on the first side of the channel at a substantially middle region of the channel, and the second non-magnetic guide being mounted on the second side of the channel at a substantially middle region of the channel. The non-magnetic guide may be made of a material having a low coefficient of friction property to help facilitate translation of the bridge within the channel. The Q axis may be equidistantly spaced from the edge of the first permanent magnet and the edge of the second permanent magnet, and bisect at least a portion of the channel. The channel may be equidistantly spaced between the first D axis and the second D axis. The current flowing along each of the first D axis and the second D axis may be pulsed at the time of transition from a low torque output to a high torque output or from a high torque output to a low torque output to control the bridge magnetization to be suitable for a predetermined amount of flux shunting.

[0005] A motor assembly includes a stator core, a rotor, and a bridge. The stator core defines a cavity. The rotor is disposed in the cavity and includes a channel between a first magnet and a second magnet. The bridge is disposed in the channel to translate between at least a static position and an effective shunt flux position. The channel and the bridge are arranged relative to each other to define a first air pocket on one side of the bridge in the channel and a second air pocket on the other side of the bridge in the channel, so that the first air pocket and the second air pocket act as flux barriers to prevent rotor flux leakage until the bridge is in the effective shunt flux position. The motor assembly may also include a first non-magnetic guide and a second non-magnetic guide, the first non-magnetic guide being disposed on a first side of the channel and the second non-magnetic guide being disposed on a second side of the channel. The first non-magnetic guide and the second non-magnetic guide may be arranged together with the channel to prevent flux leakage from the bridge to the first magnet and the second magnet. The first non-magnetic guide and the second non-magnetic guide may be arranged together with the channel to facilitate translation of the bridge in the channel. The first air pocket may define a region for a rest position and the second air pocket may define a region for an active flux shunting position. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram showing an example of an electrified vehicle.

[0007] Figure 2 is an exploded perspective view of an example of a portion of an electric machine.

[0008] Figure 3 is a graph showing an example of a torque-rotation speed curve of a motor.

[0009] Figure 4 is a partial front view in cross-section of a portion of an example of a rotor of an electric machine.

[0010] Figure 5 is a graph showing another example of a torque-rotation speed curve of a motor.

[0011] Figure 6 is a schematic diagram showing an example of a relationship between a spring of a rotor and a sliding bridge.

[0012] Fig. 7A A partial front view in cross section of a portion of an example of a rotor and stator of an electric machine showing a bridge in a first position.

[0013] Figure 7B yes Fig. 7A A partial front view in cross-section of a portion of an example of a rotor and a stator of an electric machine showing the bridge in a second position.

[0014] Figure 7Cyes Fig. 7A A partial front view in cross-section of a portion of an example of a rotor and a stator of an electric machine showing the bridge in a third position.

[0015] Figure 8 A partial front view in cross section showing the oriented axes and magnetic flux paths of various electric machine components of a portion of another example of a rotor of an electric machine.

[0016] Fig. 9 A partial front view in cross-section of a portion of another example of a rotor of an electric machine showing examples of magnetic flux flow paths affected by various electric machine components.

[0017] Fig.10 A partial front view in cross-section showing another example of magnetic flux flow paths affected by various machine components, of a portion of another example of a rotor of an electric machine. DETAILED DESCRIPTION

[0018] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various forms and alternative forms. The drawings need not be drawn to scale; some features may be exaggerated or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present disclosure in various forms. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any of the figures may be combined with the features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and variations of features consistent with the teachings of the present disclosure may be desired for specific applications or embodiments.

[0019] Figure 1 is a schematic diagram showing an example of an electrified vehicle. In this example, the electrified vehicle is a PHEV, referred to herein as vehicle 12. Vehicle 12 may include one or more electric machines 14 mechanically connected to a hybrid transmission 16. Each electric machine 14 is capable of operating as a motor or a generator. In addition, hybrid transmission 16 is mechanically connected to engine 18. Hybrid transmission 16 is also mechanically connected to drive shaft 20, which is mechanically connected to wheels 22. Electric machine 14 can provide propulsion and deceleration capabilities when engine 18 is turned on or off. Electric machine 14 can also be used as a generator and can provide fuel economy benefits by recovering energy that would normally be lost as heat in a friction braking system. Because vehicle 12 can operate in electric mode under certain conditions, electric machine 14 can also provide reduced pollutant emissions.

[0020] The traction battery 24 stores energy that can be used by the motor 14. The traction battery 24 generally provides a high voltage direct current (DC) output from one or more battery cell arrays (sometimes referred to as battery cell stacks) within the traction battery 24. The battery cell array may include one or more battery cells. The traction battery 24 is electrically connected to one or more power electronics modules 26 through one or more contactors (not shown). The one or more contactors isolate the traction battery 24 from other components when disconnected and connect the traction battery 24 to other components when closed. The power electronics module 26 is also electrically connected to the motor 14 and provides the ability to transfer electrical energy bidirectionally between the traction battery 24 and the motor 14. For example, a typical traction battery 24 may provide a DC voltage, while the motor 14 may require a three-phase alternating current (AC) voltage to operate. The power electronics module 26 may convert the DC voltage into the three-phase AC voltage required by the motor 14. In regenerative mode, the power electronics module 26 may convert the three-phase AC voltage from the motor 14 used as a generator into the DC voltage required by the traction battery 24. The parts described here are also applicable to pure electric vehicles. For a purely electric vehicle, the hybrid transmission 16 may be a gearbox connected to the electric machine 14 , and the engine 18 may not be present.

[0021] In addition to providing energy for propulsion, the traction battery 24 can also provide energy for other vehicle electrical systems. A typical system may include a DC / DC converter module 28 that converts the high voltage DC output of the traction battery 24 to a low voltage DC supply that is compatible with other vehicle loads. Other high voltage loads (such as compressors and electric heaters) may be connected directly to the high voltage without using the DC / DC converter module 28. In a typical vehicle, the low voltage systems are electrically connected to an auxiliary battery 30 (e.g., a 20 volt battery).

[0022] A battery power control module (BECM) 33 may communicate with the traction battery 24. The BECM 33 may serve as a controller for the traction battery 24 and may also include an electronic monitoring system that manages the temperature and state of charge of each cell of the traction battery 24. The traction battery 24 may have a temperature sensor 31 (such as a thermistor or other thermometer). The temperature sensor 31 may communicate with the BECM 33 to provide temperature data related to the traction battery 24.

[0023] The vehicle 12 can be recharged through an external power source 36, such as an electrical outlet. The external power source 36 can be electrically connected to an electric vehicle supply equipment (EVSE) 38. The EVSE 38 can provide circuitry and control to regulate and manage the transfer of electrical energy between the power source 36 and the vehicle 12. The external power source 36 can provide DC power or AC power to the EVSE 38. The EVSE 38 can have a charging connector 40 for plugging into a charging port 34 of the vehicle 12. The charging port 34 can be any type of port configured to transfer power from the EVSE 38 to the vehicle 12. The charging port 34 can be electrically connected to a charger or an on-board power conversion module 32. The power conversion module 32 can condition the power supplied from the EVSE 38 to provide the appropriate voltage level and current level to the traction battery 24. The power conversion module 32 can interface with the EVSE 38 to coordinate the transfer of power to the vehicle 12. The charging connector 40 can have pins that match corresponding recesses of the charging port 34.

[0024] Each of the components discussed above may have one or more associated controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus, such as a controller area network (CAN), or via discrete conductors.

[0025] The battery cells of the traction battery 24 (such as prismatic cells or pouch cells) may include electrochemical elements that convert stored chemical energy into electrical energy. The prismatic cell or pouch cell may include a housing, a positive electrode (cathode), and a negative electrode (anode). The electrolyte allows ions to move between the anode and the cathode during a discharge operation and then return during a recharge operation. The terminals allow current to flow out of the battery cell for use by the vehicle. When located in an array with multiple battery cells, the terminals of each battery cell can be aligned with opposite terminals (positive terminals and negative terminals) adjacent to each other, and bus bars can help facilitate series connection between multiple battery cells. The battery cells can also be arranged in parallel so that similar terminals (positive terminals and positive terminals or negative terminals and negative terminals) are adjacent to each other.

[0026] Figure 21 is a partially exploded view showing an example of multiple parts of an electric machine for an electrified vehicle, which is generally referred to herein as an electric machine 100. The electric machine may include a stator core 102 and a rotor 106. As described above, an electrified vehicle may include two electric machines. One of the electric machines may be used primarily as a motor and the other may be used primarily as a generator. The motor may operate to convert electricity into mechanical power and the generator may operate to convert mechanical power into electricity. The stator core 102 may define an inner surface 108 and a cavity 110. The size of the rotor 106 may be suitable for setting and operation within the cavity 110. The shaft 112 may be operably connected to the rotor 106 and to other vehicle components to transmit mechanical power from the shaft 112.

[0027] The winding 120 may be disposed within the cavity 110 of the stator core 102. In an example where the electric machine is a motor, current may be fed to the winding 120 to obtain a rotational force on the rotor 106. In an example where the electric machine is a generator, the current generated in the winding 120 by the rotation of the rotor 106 may be used to power vehicle components. Multiple portions of the winding 120 (such as the end winding 126) may protrude from the cavity 110. During operation of the electric machine 100, heat may be generated along the winding 120 and the end winding 126. The rotor 106 may include magnets so that the rotation of the rotor 106 cooperates with the current flowing through the end winding 126 to generate one or more magnetic fields. For example, the current flowing through the end winding 126 generates a rotating magnetic field. The magnets of the rotor 106 will be magnetized and rotate with the rotating magnetic field to rotate the shaft 112 to obtain mechanical power.

[0028] Figure 3 A graph showing an example of a torque-speed curve for an electric machine is shown, which is generally referred to herein as graph 200. X-axis 204 represents rotor speed and Y-axis 206 represents torque at which the electric machine is operated. Torque-speed curve 210 represents the relationship between the typical torque output of the electric machine and the rotor speed. Region 212 represents a region of high torque performance requirements and region 214 represents a region of low torque drive cycle points. The role of the electric machine in a motor vehicle traction application may require high torque for performance related to the amount of torque required to run through most EPA efficiency cycles. Permanent magnet motors are often used due to the high efficiency provided by the "free" rotor magnetic field associated with the permanent magnets. However, one disadvantage is that the free rotor magnetic field is always "on" and the stator core losses in the electric machine are a function of the magnetic field. For high torque points, a large rotor magnetic field is required to produce a large amount of torque using low current. However, for low torque points or zero torque points, a large rotor magnetic field can produce high stator core losses. Therefore, for electric machines that require high maximum torque and low drive cycle torque, a constant permanent magnet rotor magnetic field is usually optimized for only one of the desired conditions.

[0029] Figure 42 is a partial cross-sectional view of an example of a portion of a rotor (referred to herein as rotor 230) of an electric machine. The electric machine may be operated in an electrified vehicle or a vehicle that includes only an internal combustion engine. The rotor 230 includes components to generate a rotor flux field that varies with the speed of the rotor 230 and the position of the bridge by using a sliding bridge, thereby forming a permanent magnet motor with a variable rotor flux. Generating a variable rotor flux provides both high torque output and low torque output to accommodate different torque requirements in a vehicle driving cycle. In the case where the rotor flux is variable, the torque output of the shaft connected to the rotor 230 may be adjusted based on the speed of the rotor 230. For example, the rotor 230 may include a pair of first magnets 232, a pair of second magnets 234, and a channel 236 disposed between each magnet pair. For example, each magnet may be a rare earth magnet (such as a neodymium magnet). The channel 236 may be spaced approximately equidistant from the magnet. The first end of the channel 236 may be spaced apart from the outer surface of the rotor 230 by a distance based on a predetermined stress operating parameter of the rotor 230. The bridge 238 may be disposed within the channel 236 to translate between at least a first position and a second position. For example, the centrifugal force generated by the rotation of the rotor 230 may affect the movement of the bridge 238 within the channel 236. The bridge 238 may be a soft ferromagnetic material having high magnetic susceptibility and high magnetic permeability properties. Examples of materials for the bridge 238 include silicon steel, iron, cobalt, and ferrite.

[0030] By predictably controlling the position of the bridge 238 in the channel 236, the thickness of the shunt flux path can be changed according to the position adjustment of the bridge 238. The first non-magnetic guide 242 and the second non-magnetic guide 244 can be respectively arranged on opposite sides of the channel 236 at or near the substantially central channel area. The first non-magnetic guide 242 and the second non-magnetic guide 244 can be a material (such as a polymer) with a low friction coefficient and non-magnetic properties. For example, compared with the material of the rotor 230 or other materials with a higher friction coefficient, the low friction coefficient can help to affect the easier translation of the bridge 238. When the rotor 230 is stationary, the bridge 238 can be located in the stationary area 246. When the rotor 230 rotates, the bridge 238 can slide through the transition area due to centrifugal force to reach the effective shunt flux area 248. When the bridge 238 is located at the upper wall of the channel 236 or near the upper wall of the channel 236, the bridge 238 is in a complete shunt area. The bridge 238 may be positioned within the channel 236 such that air pockets are defined on either side of the bridge 238. The air pockets may act as flux barriers to prevent rotor flux leakage until the bridge 238 is in the effective shunting flux region 248.

[0031] The first non-magnetic guide 242 and the second non-magnetic guide 244 can help prevent flux leakage from occurring in the direction indicated by arrow 245 from the bridge 238 to one of the magnet pairs. The shape of each of the first non-magnetic guide 242 and the second non-magnetic guide 244 can vary based on the angle or orientation of the magnets mounted to the rotor 230 and located near each of the first non-magnetic guide 242 and the second non-magnetic guide 244. For example, each non-magnetic guide may include a guide edge that is substantially parallel to the magnet edge of one of the adjacent magnets of the pair of first magnets 232 or the pair of second magnets 234. In this example, each non-magnetic guide is shown as having a substantially elongated triangular shape, however, it is contemplated that the non-magnetic guide may have other shapes (such as, in an embodiment where the adjacent magnets are oriented to define an edge or plane parallel to the rectangular side of the non-magnetic guide, the non-magnetic guide is substantially rectangular in shape).

[0032] Optionally, a spring 250 may be disposed within the channel 236 to bias the movement of the bridge 238 in a predictable manner. For example, as described above, when the rotor 230 rotates, the spring 250 may be oriented within the channel 236 to predictably affect the centripetal force, thereby resisting the centrifugal force acting on the bridge 238. Additionally, when the rotor 230 is not rotating, the spring 250 may be used to keep the bridge 238 within the stationary region 246. The spring 250 may be secured to one end of the bridge 238 and to the inner surface of the channel 236. Under certain conditions (rotor 230 rotating at a certain speed), the spring 250 may be used to predictably affect the bridge 238 so that the bridge 238 is located within the effective shunt flux region 248. The bias of the spring 250 may be adjusted based on the size of the rotor, the range of centrifugal forces depending on the operating conditions of the rotor 230, and the motor torque speed specification.

[0033] Figure 5 and Figure 6 An example of the mechanical relationship between a spring, a bridge, and a rotor (such as spring 250, bridge 238, and rotor 230) is shown. Figure 5 In FIG. 2 , the X-axis 251 represents revolutions per minute (RPM), and the Y-axis 252 represents torque. Line 253 represents a torque-speed curve. The speed of the rotor is represented by line 254 of RPM1, line 255 of RPM2, and line 256 of RPM3. As described above, the centrifugal force (at Figure 6 The force F represented by the arrow cdenoted) can affect the movement of the bridge 238 within the channel 236. When the rotor 230 rotates at RPM1, the bridge 238 can be in a stationary position. When the rotor 230 rotates at RPM2, the bridge 238 can be between the transition region and the effective flow splitting region. When the rotor 230 rotates at RPM3, the bridge 238 can be in a fully splitting position.

[0034] To affect the position adjustment of the bridge 238 within the channel 236 , the spring constant of the spring 250 may be based on the mass of the bridge 238 and the desired movement of the bridge 238 . Figure 6 Schematic diagrams of rotor 230, bridge 238, and spring 250 are shown. Line 257 at X1 may correspond to the rest position of bridge 238. Line 258 at X2 may correspond to the position of bridge 238 between the transition region and the effective flow-dividing region. Line 259 at X3 may correspond to the fully-dividing position of bridge 238.

[0035] The force equation for spring 250 can be expressed as:

[0036] F s =kx

[0037] The force equation for the mass of the sliding bridge 238 under acceleration can be expressed as:

[0038] F c =mrω 2 =mrπRPM 2 / 30

[0039] The system equations can be expressed as:

[0040] or

[0041] To identify the spring constant and deformation of the spring 250, the desired rotational speeds for conversion RPM1, RPM2, and RPM3 are defined based on the performance requirements of the rotor 230. Then, X1 may be selected and k may be solved at RPM1. By using k, X2 may be solved at RPM2, and X3 may be solved at RPM3.

[0042] FIG. 7A to FIG. 7C An example of the location of the bridge 238 that produces different flux paths relative to the stator core 260 having the end windings 262 is shown. The shunted flux produced by one of the pair of first magnets 232 and one of the pair of second magnets 234 adjacent to each other is represented by flow path 261. The flux produced by the stator core 260 is represented by flow path 263. Fig. 7A , bridge 238 is shown as not engaged with flow path 261 and in a static position within static region 246. In this position, bridge 238 facilitates magnetic flux flow to stator core 260. Figure 7B , bridge 238 is shown partially engaging flow path 261 in a transition region on the way to active split flux region 248. Figure 7C , the bridge 238 is shown engaged with the flow path 261 and in an effective shunting position within the effective shunting flux region 248. In this position, the bridge 238 facilitates the flux flow generated by the pair of first magnets 232 and the pair of second magnets 234 to minimize the induced voltage and magnetic losses by maintaining the magnetic flux within the rotor 230 while minimizing the interaction with the end windings 262.

[0043] Figures 8 to 10 300 . The rotor 300 may be operated in an electric motor of an electrified vehicle or a vehicle having only an internal combustion engine. The rotor 300 includes a component for generating a permanent magnet motor having a variable rotor flux. For example, the rotor 300 may include a pair of first magnets 304, a pair of second magnets 306, and a variable flux magnet 310 embedded in a bridge 312. Each of the first magnets 304 and the second magnets 306 may be, for example, a rare earth magnet (such as a neodymium magnet). As further described herein, the variable flux magnet 310 may be, for example, a magnet having a lower coercive force property (such as aluminum nickel cobalt (AlNiCo), ferrite, or a low-energy rare earth metal). Each of the first magnets 304 may be arranged with each other to form an inverted V shape. Each of the second magnets 306 may be arranged with each other to form an inverted V shape. A space 316 may be defined by the rotor 300 on both sides of each magnet of the pair of first magnets 304, and a space 318 may be defined by the rotor 300 on both sides of each magnet of the pair of second magnets 306. The spaces 316 and 318 provide a structure for assisting in orienting the pair of first magnets 304 and the pair of second magnets 306 relative to the variable flux magnet 310.

[0044] The shunt magnetic flux generated by one magnet of the pair of first magnets 304 and one magnet of the pair of second magnets 306 adjacent to each other is represented by a flow path 315. The magnetic flux generated by the stator core (not shown) is represented by a flow path 317.

[0045] Embedding the variable flux magnets 310 within the bridge 312 helps shunt the flux when high torque is not required by preventing excess flux from reaching the adjacent stator core. Depending on the magnetization state of the variable flux magnets 310, the flux from the main path along the Q axis from the rotor 300 to the stator can be added, subtracted, or ignored. The variable flux magnets 310 can have the property of resisting the flux from the main path while also being controllable with a reasonable D axis current. For example, AlNiCo is a material that can be used due to its lower coercivity properties and higher temperature insensitivity. Ferrites or weaker / thinner rare earth grade materials can also be used.

[0046] Variable flux magnets 310 may be wedge-shaped to help control the flux during operation of rotor 300. For example, Figure 8 As shown, the variable flux magnet 310 may have a trapezoidal shape with an outer side 319 having a length less than the inner side 321. It is also contemplated that in another component example, the outer side 319 may have a length greater than the inner side 321. The trapezoidal shape may help provide a flux path with a variable length to control the magnetization characteristics, because the system efficiency may be improved with the increased control of the interchanged south and north poles of the variable flux magnet 310. For example, a thinner path may require a smaller magnetic field to magnetize or demagnetize the variable flux magnet 310 to generate a smaller D-axis current. A thicker path may require a larger magnetic field to magnetize or demagnetize the variable flux magnet 310 to generate a larger D-axis current. The D-axis current may be pulsed to help control the magnetization of the bridge 312. For example, the D-axis current may be pulsed at a transition between a low torque output to a high torque output (or a transition between a high torque output to a low torque output) to control the bridge magnetization to an amount suitable for the desired flux split.

[0047] A first D axis 324 may be defined between the pair of first magnets 304 and spaced equidistantly from the edge of each adjacent space 316. A second D axis 326 may be defined between the pair of second magnets 306 and spaced equidistantly from the edge of each adjacent space 318. Each of the first D axis 324 and the second D axis 326 represents a centerline of a magnetic pole. For example, the pair of first magnets 304 may represent a south pole and the pair of second magnets 306 may represent a north pole. It is contemplated that similar D axes will be dispersed throughout the rotor 300 at similar positions relative to other adjacent magnet pairs.

[0048] The Q axis 332 may be defined between one of the pair of first magnets 304 and one of the pair of second magnets 306, spaced equidistantly from the edges of the space 316 and the space 318 adjacent to each other, and disposed between the first D axis 324 and the second D axis 326. It is contemplated that similar Q axes will be dispersed throughout the rotor 300 in similar positions relative to other adjacent magnets. The variable flux magnet 310 may be bisected by the Q axis 332 or may be offset from the Q axis 332 in either direction. Current flowing along the Q axis 332 may help control the torque output of the rotor 300.

[0049] The first D axis 324 may be perpendicular to the first tangential axis 340. The first tangential axis 340 may represent a tangent to the outer surface of the rotor 300. The second D axis may be perpendicular to the second tangential axis 342. The second tangential axis 342 may represent another tangent to the outer surface of the rotor 300. The Q axis may be perpendicular to the third tangential axis 344. The third tangential axis 344 may represent another tangent to the outer surface of the rotor 300.

[0050] The first offset axis 350 can be spaced parallel to the first tangential axis 340 and perpendicular to the first D axis 324. The first offset axis 350 can intersect a corner of each magnet in the pair of first magnets 304. Each magnet in the pair of first magnets 304 can include an edge 352 defining a first edge axis 354. Each first edge axis 354 can be arranged at an angle between zero and ninety degrees relative to the first offset axis 350 (represented by angle 358). In one example, each first edge axis 354 is arranged at a thirty degree angle relative to the first offset axis 350.

[0051] The second offset axis 360 may be spaced parallel to the second tangential axis 342 and perpendicular to the second D axis 326. The second offset axis 360 may intersect a corner of each magnet in the pair of second magnets 306. Each magnet in the pair of second magnets 306 may include an edge 362 defining a second edge axis 364. Each second edge axis 364 may be arranged at an angle between zero and ninety degrees relative to the second offset axis 360 (represented by angle 368). In one example, each second edge axis 364 is arranged at a thirty degree angle relative to the second offset axis 360.

[0052] Each inverted V-shape defined by the pair of first magnets 304 and the pair of second magnets 306 helps to concentrate the D-axis magnetic flux into the variable flux magnet 310 to allow the effect of the D-axis current on the magnetization to be amplified. Fig. 9 , each of the pair of first magnets 304 and the pair of second magnets 306 is arranged so as not to interfere with the magnetic flux generated by the stator core and represented by flow path 365. This arrangement helps guide flow path 365 into variable flux magnet 310.

[0053] Various orientations of each magnet in the pair of first magnets 304 and the pair of second magnets 306 may be used to arrange the magnets to help direct the flow path 365 into the variable flux magnet 310. For example, an upper outer corner 370 of one magnet in the pair of first magnets 304 and an upper outer corner 372 of one magnet in the pair of second magnets 306 may be spaced apart from the outer surface of the rotor 300 by a distance based on a predetermined stress operating parameter of the rotor 300. An upper inner corner 379 of one magnet in the pair of first magnets 304 and an upper inner corner 376 of one magnet in the pair of second magnets 306 may be spaced apart from the outer surface of the rotor 300 by a distance based on a predetermined stress operating parameter of the rotor 300.

[0054] Each of the first side flux barrier 380 and the second side flux barrier 382 may be mounted to the rotor 300 on opposite sides of the variable flux magnet 310. The first side flux barrier 380 and the second side flux barrier 382 may help prevent the Q-axis current or flux from affecting the magnetization state of the variable flux magnet 310. For example, Fig.10 Compared to the flow path 392 in FIG. 1 , the first side flux barrier 380 and the second side flux barrier 382 may affect the flux flowing through the variable flux magnet 310 to be in a substantially horizontal direction (represented by Fig.10 390 in FIG. 1 ). The first side flux barrier 380 and the second side flux barrier 382 may also provide a measure of separation of the D-axis flux from the stator and the D-axis flux from the pair of first magnets 304 and the pair of second magnets 306 to help facilitate better magnetization control of the variable flux magnet 310. Although the first side flux barrier 380 and the second side flux barrier 382 are shown as having three generally straight-line shaped barriers in this example, it is contemplated that a greater number of barriers having curved shapes may be used.

[0055] The words used in the specification are descriptive words rather than restrictive words, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of each embodiment can be combined to form further embodiments of the present invention that may not be clearly described or shown. Although each embodiment may be described as providing advantages or being superior to other embodiments or prior art embodiments in one or more desired characteristics, it should be appreciated by those of ordinary skill in the art that one or more features or characteristics can be compromised to achieve desired overall system properties according to specific applications and embodiments. These attributes may include but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as being less desirable than other embodiments or prior art embodiments in one or more characteristics are not outside the scope of the present disclosure, and can be expected to be used for specific applications.

Claims

1. A vehicle motor assembly, comprising: a stator core defining a cavity; a rotor disposed within the cavity and including a channel defined between the first magnet and the second magnet; a bridge disposed within the channel for translation between at least a first position and a second position, a first non-magnetic guide mounted on a first side of the channel at a mid-region of the channel; as well as a second non-magnetic guide mounted on a second side of the channel at a middle region of the channel, wherein translation of the bridge adjusts a magnetic flux path from the rotor to the stator core based on a position of the bridge, The first non-magnetic guide and the second non-magnetic guide extend into the rotor away from the channel, The first non-magnetic guide has a first surface defining the channel and a second surface opposite to the first surface and parallel to an end of the first magnet, and The second non-magnetic guide has a first surface defining the passage and a second surface opposite to the first surface and parallel to an end of the second magnet.

2. The vehicle motor assembly of claim 1, wherein: The bridge is composed of a ferromagnetic material.

3. The vehicle motor assembly of claim 1, wherein: The non-magnetic guide is constructed of a material having low coefficient of friction properties to help facilitate translation of the bridge within the channel.

4. The vehicle motor assembly of claim 1, wherein: The first position is further defined as a stationary position, in which the centrifugal force generated by the rotation of the rotor is substantially zero, and the second position is further defined as an effective split flux position, and wherein, when the bridge is in the effective split flux position, the bridge operates to control the flux path from the rotor to the stator core.

5. The vehicle motor assembly of claim 1, wherein: The second position is further defined as an effective split flux position where the bridge increases the width of a high permeability path through a portion of the rotor.

6. An electric vehicle motor assembly, comprising: a stator core defining a cavity; a rotor disposed within the cavity and including a passage between the first magnet and the second magnet; a bridge, arranged in the channel for translation; a spring disposed within the channel and oriented to bias the movement of the bridge in a direction opposite to the direction of the centrifugal force generated by the rotation of the rotor, a first non-magnetic guide mounted on a first side of the channel at a mid-region of the channel; as well as a second non-magnetic guide mounted on a second side of the channel at a middle region of the channel, The first non-magnetic guide and the second non-magnetic guide extend into the rotor away from the channel, The first non-magnetic guide has a first surface defining the channel and a second surface opposite to the first surface and parallel to an end of the first magnet, and The second non-magnetic guide has a first surface defining the passage and a second surface opposite to the first surface and parallel to an end of the second magnet.

7. The electric vehicle motor assembly of claim 6, wherein: The spring is adjusted based on rotor torque-speed specifications and rotor geometry to optimize the position of the bridge within the channel to control the amount of magnetic flux flowing from the rotor to the stator core.

8. The electric vehicle motor assembly of claim 7, wherein: The spring constant of the spring is selected based on the following equation: .

9. The electric vehicle motor assembly of claim 6, wherein: The bridge and channel define a first air pocket on one side of the bridge within the channel and a second air pocket on the other side of the bridge within the channel.

10. The electric vehicle motor assembly of claim 6, wherein: The non-magnetic guide is constructed of a material having low coefficient of friction properties to help facilitate translation of the bridge within the channel.

11. The electric vehicle motor assembly of claim 6, wherein: The Q axis is equidistantly spaced from an edge of the first permanent magnet and an edge of the second permanent magnet and bisects at least a portion of the channel.

12. The electric vehicle motor assembly of claim 6, wherein: The channels are equally spaced between the first D-axis and the second D-axis, and wherein current flowing along each of the first D-axis and the second D-axis is pulsed at a transition between a low torque output to a high torque output or vice versa to control the bridge magnetization to be suitable for a predetermined amount of flux splitting.

13. A motor assembly, comprising: a stator core defining a cavity; a rotor disposed within the cavity and including a passage between the first magnet and the second magnet; a bridge disposed within the channel for translation between at least a rest position and an effective flux-dividing position, a first non-magnetic guide mounted on a first side of the channel at a mid-region of the channel; as well as a second non-magnetic guide mounted on a second side of the channel at a middle region of the channel, wherein the channel and the bridge are arranged relative to each other to define a first air pocket on one side of the bridge within the channel and a second air pocket on the other side of the bridge within the channel, such that the first air pocket and the second air pocket act as flux barriers to prevent rotor flux leakage until the bridge is in an effective flux-diverting position, The first non-magnetic guide and the second non-magnetic guide extend into the rotor away from the channel.

14. The motor assembly of claim 13, wherein: The first and second non-magnetic guides are arranged with the channel to block leakage of magnetic flux from the bridge to the first and second magnets.

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