AXIAL FLUID MOTOR WITH ADJUSTABLE AIR GAP

Abstract

Axial flux motor (220), comprising: a stator (220S); a rotor (220R) which includes a rotor frame (251) and has a rotation axis (A); an axial air gap (260) separating the stator (220S) and the rotor (220R), wherein the axial air gap (260) corresponds to an axial position of the rotor frame (251); and at least one hydraulic actuator comprising a variable-volume hydraulic fluid chamber (270) defined in the rotor frame (251), wherein a change in the volume of the variable-volume hydraulic fluid chamber (270) causes a change in the axial position of the rotor frame (251) and a corresponding change in the axial air gap (260) separating the stator (220S) and the rotor (220R); characterized in that the at least one hydraulic actuator comprises several hydraulic actuators distributed circumferentially around the rotor (220R).

Description

[0001] The present disclosure relates to permanent magnet axial flux (PM-AF) motors. PM motors can generate a back EMF in the stator windings that is proportional to the motor speed and air gap field strength. Without some type of field weakening above base speed operation, a PM motor can be speed and torque limited.

[0002] The document EP 4 037 166 A1 discloses an axial flux motor according to the preamble of claim 1.

[0003] The document DE 601 01 107 T2 discloses a rolling bearing guide device and a drive system which include a guide rail with a rolling element rolling surface, a running rail with a load rolling element rolling surface, a guide rail rolling element circulation passage, a running rail rolling element circulation passage and a plurality of rolling elements in order to achieve a large extension / retraction length and to absorb a moment load, a radial load and a thrust load.

[0004] The document US 2020 / 0 353 596 A1 discloses a gripper device with a motor-driven pulley that drives another pulley via a belt and drives a ball screw to rotate.

[0005] The object of the invention is to provide an axial flow motor that allows lower system hydraulic pressures and takes into account system balance requirements and total hydraulic force multiplication.

[0006] This object is achieved by the axial flux motor according to claim 1. Advantageous developments of the invention are described in the subclaims. SUMMARY

[0007] In an exemplary embodiment, an axial flux motor may include a stator, a rotor including a rotor frame and having a rotational axis, an axial air gap separating the stator and the rotor, wherein the axial air gap corresponds to an axial position of the rotor frame, and at least one hydraulic actuator including a variable-volume hydraulic fluid chamber defined in the rotor frame, wherein a change in the volume of the variable-volume hydraulic fluid chamber causes a change in the axial position of the rotor frame and a corresponding change in the axial air gap separating the stator and the rotor. The at least one hydraulic actuator comprises a plurality of hydraulic actuators distributed angularly or circumferentially around the rotor.

[0008] In addition to one or more of the features described herein, the at least one hydraulic actuator may be a linear hydraulic actuator.

[0009] In addition to one or more of the features described herein, the at least one hydraulic actuator may be a rotary hydraulic actuator.

[0010] In addition to one or more of the features described herein, the axial flow motor may further include a motor output shaft having a passage that communicates hydraulic fluid to and from the variable volume hydraulic fluid chamber.

[0011] In addition to one or more of the features described herein, the at least one hydraulic actuator may include a plurality of variable volume hydraulic fluid chambers.

[0012] According to the invention, the at least one hydraulic actuator comprises a plurality of hydraulic actuators which are distributed around the rotor in the angular direction or circumferential direction.

[0013] In addition to one or more of the features described herein, the axial flow motor may further include a motor output shaft having a passage communicating hydraulic fluid to the variable volume hydraulic fluid chamber, wherein the variable volume hydraulic fluid chamber may include a cavity in the rotor frame enclosing a vein plate, the vein plate extending radially outward from a cylindrical base surrounding the motor output shaft, the cylindrical base being mounted to the motor output shaft such that the cylindrical base is rotatable and axially fixed with respect to the motor output shaft, and the rotor frame being mounted to the cylindrical base such that the rotor frame is axially displaceable.

[0014] In addition to one or more of the features described herein, the axial flow motor may further include a motor output shaft including a passage communicating hydraulic fluid to the variable volume hydraulic fluid chamber, wherein the variable volume hydraulic fluid chamber may include a cavity in the rotor frame enclosing a wire plate, the wire plate extending radially outward from the motor output shaft, the wire plate being attached to the motor output shaft such that the wire plate is rotationally fixed with respect to the motor output shaft and axially translatable with respect to the motor output shaft, and the rotor frame being attached to the motor output shaft such that the rotor frame is rotationally and axially translatable with respect to the motor output shaft.

[0015] In addition to one or more of the features described herein, the rotor frame may be attached to the motor output shaft by a lead screw coupling.

[0016] In addition to one or more of the features described herein, the lead screw coupling may include a ball screw.

[0017] In addition to one or more of the features described herein, the axial flux motor may include a Belleville spring that is compressible during changes in the axial position of the rotor frame.

[0018] In addition to one or more of the features described herein, the axial flow motor may further include a binary fluid control valve having a first state that supplies the hydraulic fluid to the hydraulic fluid chamber and a second state that discharges the hydraulic fluid from the hydraulic fluid chamber.

[0019] In addition to one or more of the features described herein, the rotor may include surface-mounted permanent magnets.

[0020] In another exemplary embodiment, an axial flux motor may include a stator, a rotor including a rotor frame and having a rotational axis, an axial air gap separating the stator and the rotor, the axial air gap corresponding to an axial position of the rotor frame, a motor output shaft, at least one hydraulic actuator including a variable volume hydraulic fluid chamber defined in the rotor frame, the variable volume hydraulic fluid chamber including a cavity in the rotor frame enclosing a flex plate, the flex plate extending radially outward from a cylindrical base surrounding the motor output shaft, the cylindrical base being attached to the motor output shaft such that the cylindrical base is rotatable and axially immovable with respect to the motor output shaft, the rotor frame being attached to the cylindrical base such that the rotor frame is axially displaceable,a change in the volume of the variable-volume hydraulic fluid chamber causes a change in the axial position of the rotor frame and a corresponding change in the axial air gap separating the stator and the rotor, and the motor output shaft communicates hydraulic fluid to and from the variable-volume hydraulic fluid chamber, and a binary fluid control valve having a first state supplying the hydraulic fluid to the hydraulic fluid chamber and a second state discharging the hydraulic fluid from the hydraulic fluid chamber.

[0021] In addition to one or more of the features described herein, the axial flux motor may further include a spring that, when compressed, biases the rotor away from the stator.

[0022] In addition to one or more of the features described herein, the axial flux motor may further include a spring that, when compressed, biases the rotor toward the stator.

[0023] In yet another exemplary embodiment, an axial flux motor may include a motor rotation axis, a stator having a pair of axial sides, a rotor including a respective rotor structure on each axial side of the stator, each rotor structure including a rotor frame, a respective axial air gap separating the stator and each respective rotor structure, each axial air gap corresponding to an axial position of the respective rotor frame, for each rotor structure, at least one respective hydraulic actuator may include a respective variable volume hydraulic fluid chamber defined in the respective rotor frame, and a change in the volume of the respective variable volume hydraulic fluid chamber causes a change in the axial position of the respective rotor frame and a corresponding change in the corresponding axial air gap separating the stator and the respective rotor structure,and a binary fluid control valve having a first state supplying hydraulic fluid to each variable volume hydraulic fluid chamber and a second state discharging the hydraulic fluid from each variable volume hydraulic fluid chamber.

[0024] In addition to one or more of the features described herein, for each rotor structure, the at least one respective hydraulic actuator may be a rectilinear hydraulic actuator.

[0025] In addition to one or more of the features described herein, for each rotor structure, the at least one respective hydraulic actuator may be a rotating hydraulic actuator.

[0026] In addition to one or more of the features described herein, for each rotor structure, the respective variable volume hydraulic fluid chamber may include a respective cavity in the respective rotor frame enclosing a respective core plate, the respective core plate extending radially outward from a respective cylindrical base surrounding a motor output shaft, the respective cylindrical base being attached to the motor output shaft such that the respective cylindrical base is rotatable and axially fixed with respect to the motor output shaft, and the respective rotor frame being attached to the respective cylindrical base such that the respective rotor frame is axially displaceable.

[0027] The above-described features and advantages and other features and advantages of the disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 an electrified vehicle according to one or more embodiments; Fig. 2A and Fig. 2B illustrates an axial flux motor according to one or more embodiments; Fig. 3A and Fig. 3B illustrates an axial flux motor according to one or more embodiments; Fig. 4A and Fig. 4B schematic sectional views of the axial flux motor of Fig. 3A and Fig. 3B according to one or more embodiments; Fig. 5A and Fig. 5B illustrates a diagrammatic control mechanism for an axial flux motor according to one or more embodiments, and Fig. 6 exemplary curves of torque (TQ) versus engine speed (S) according to one or more embodiments. DETAILED DESCRIPTION

[0029] Fig. 1 schematically illustrates one embodiment of an electric drive system 101 in a vehicle 100. Motor vehicle and vehicle are understood to refer to any means of transportation, including non-limiting examples of motorcycles, passenger cars, trucks, buses, excavation, earthmoving, construction and agricultural equipment, rail vehicles such as trains and trams, and watercraft such as ships and boats. The electric drive system 101 may include various control components, electrical systems, and electromechanical systems, including, for example, a rechargeable energy storage system (RESS) 104 and an electric drive unit (EDU) 102. The electric drive system 101 may be used in a powertrain system to generate drive torque, as a replacement for, or in conjunction with, an internal combustion engine in various electric vehicle (EV) applications.Hybrid electric vehicle (HEV) applications.

[0030] The EDU 102 may be of varying complexity, features, and integration. An exemplary highly integrated EDU 102 may include, for example, a rotating electrical machine such as an alternating current (AC) motor (motor) 120 and a traction power inverter module (TPIM) 106, which includes a motor control unit 105 and a power inverter 110. The motor 120 may include a stator 120S and a rotor 120R coupled to a motor output shaft 125, and a position sensor 182, such as a variable reluctance encoder or an encoder. The position sensor 182 may connect directly to the motor control unit 105 and is used to measure the angular position of the rotor (θ e ) of the motor 120. The angular position of the rotor (θ e) of the motor 120 is used by the motor control unit 105 to control the operation of the power inverter 110 that controls the motor 120.

[0031] The engine output shaft 125 can transmit torque between the engine 120 and driveline components (not shown), some of which may be integrated into the EDU 102, e.g., a transmission housing containing reduction and differential gear sets and one or more axle outputs. The transmission housing may simply contain a reduction gear and a propeller shaft output for coupling to a differential gear set. One or more axles may couple to the transmission housing directly or through final drive or differential gear sets, if separate. One or more axles may couple to one or more vehicle wheels for transmitting tractive force between a wheel and a road surface. One of ordinary skill in the art will recognize alternative configurations for driveline components. Drive torque requests or commands 136 (T cmd) can be supplied by a vehicle control unit 103 to the engine control unit 105.

[0032] Each control unit may contain one or more control modules. As used herein, control module, module, controller, control unit, electronic control unit, processor, and similar terms mean any or various combinations of one or more of one or more application-specific integrated circuits (ASICs), one or more electronic circuits, one or more central processing units (preferably one or more microprocessors), and associated memory and storage (read-only memory (ROM), random access memory (RAM), electrically programmable read-only memory (EPROM), hard disk, etc.).) or microcontrollers executing one or more software or firmware programs or routines, one or more combinational logic circuits, input / output (I / O) circuitry and devices, and suitable signal conditioning and buffering circuitry, a high-speed clock, analog / digital (A / D) circuitry, digital / analog (D / A) circuitry, and other components to provide the described functionality. A control module may include a plurality of communication interfaces, including point-to-point or discrete line, and wired or wireless interfaces to networks, including wide area networks, local area networks, and intra-plant and service-related networks, including over-the-air (O-TA) software updates.Functions of a control module according to this disclosure may be performed in a control architecture distributed among multiple networked control modules. Software, firmware, programs, instructions, routines, code, algorithms, and similar terms mean any controller-executable instruction sets that include calibrations, data structures, and lookup tables. A control module may include a set of control routines executed to provide described functions. Routines are executed, for example, by a central processing unit and are operable to monitor inputs from sensing devices and other networked control modules and to execute control and diagnostic routines to control the operation of actuators. Routines may be executed at regular intervals during ongoing powertrain and vehicle operation.Alternatively, routines can be executed in response to the occurrence of an event, software calls, or on demand via user interface inputs or requests.

[0033] The RESS 104, in one embodiment, may include one or more electrochemical battery assemblies 112, e.g., high-capacity, high-voltage (HV) rechargeable lithium-ion battery assemblies for delivering power to the vehicle via an HV direct current (HV-DC) bus 108. The RESS 104 may also include a battery manager module 114. The RESS 104 may include one or more battery assemblies 112 constructed from multiple battery assembly modules, allowing flexibility in configurations and adaptation to application requirements. Battery assemblies may include multiple battery assembly modules constructed from multiple cells, allowing flexibility in configurations and adaptation to application requirements. Battery assembly modules may include multiple cells, allowing flexibility in configurations and adaptation to application requirements.For example, in vehicle applications, the RESS 104 may be modular in that the number of battery assembly modules can be varied to accommodate a desired energy density or range objective of a particular vehicle platform, an intended use, or a cost target. Battery assemblies and battery assembly modules can be differently and selectively configured according to a desired propulsion architecture and desired charging functions. It should be understood that the RESS 104 may be reconfigurable at any level of integration, including a battery assembly, a battery module, and a cell.

[0034] The motor 120 may be a multi-phase AC motor that receives multi-phase AC power via a multi-phase motor control power bus (an AC bus) 111 coupled to the power inverter 110. In one embodiment, the motor 120 is a three-phase motor and the power inverter 110 is a three-phase inverter. The power inverter 110 may include multiple solid-state switches in a solid-state switching section. The power inverter 110 couples to DC power via the HV DC bus 108 (input DC voltage (V dc )) from the RESS 104, e.g., at 400 or 800 volts. The motor control unit 105 is coupled to the power inverter 110 for its control. The power inverter 110 electrically connects to stator phase windings of a three-phase stator winding of the motor 120 via the AC bus 111, whereby electrical current (I abc) in two or three phases thereof. The power inverter 110 may be configured with suitable control circuits that use paired power transistors (e.g., IGBTs) to convert a high-voltage DC voltage in the HV DC bus 108 to a high-voltage three-phase AC voltage (V abc ) in the AC bus 111 and converting a high-voltage three-phase alternating voltage (V abc ) in the AC bus 111 to a high voltage DC voltage in the HV DC bus 108. The power inverter 110 may employ any suitable pulse width modulation (PWM) control, such as sinusoidal pulse width modulation (SPWM) or space vector pulse width modulation (SVPWM), to generate switching vector signals (S abc) 109 to convert stored DC electrical power originating from the battery assembly 112 of the RESS 104 into AC electrical power to drive the motor 120 to generate torque. Accordingly, the power inverter 110 may convert mechanical power transmitted to the motor 120 into DC electrical power to generate electrical energy storable in the battery assembly 112 of the RESS 104, including as part of a regenerative braking control strategy. The power inverter 110 may be configured to generate the switching vector signals (S abc ) 109 from the engine control unit 105 and receives control inverter states to provide the engine drive and regeneration functionality. Switching vector signals (S abc ) 109 can also be referred to here as management instructions.

[0035] The control of the power inverter 110 may include high-frequency switching of the solid-state switches according to PWM control. Several design and application considerations and constraints determine the inverter switching frequency and PWM control. Inverter controls for AC motor applications may include fixed switching frequencies, e.g., switching frequencies around 10-30 kHz, and PWM controls that minimize switching losses of the IGBTs or other power switches of the power inverter 110.

[0036] The motor 120 in the EDU 102 of the electric drive system 101 in one embodiment may be a permanent magnet axial flux (PMAF) motor. The disclosed improvement relates to a mechanically based field weakening device and a control of such a motor. Fig. 2A and Fig. 2B schematically illustrate an embodiment of a PMAF engine 220 in relevant parts and Fig. 3A and Fig. 3B schematically illustrate another embodiment of a PMAF motor 220 in relevant parts. The motor 220 may include a stator 220S, a rotor 220R, and a motor output shaft 225. A motor frame 230 may support the stator 220S and bearings 240. The bearings 240, in turn, rotatably support the motor output shaft 225. Each bearing 240 may include an outer ring 240A attached to the motor frame 230, rolling elements (e.g., balls, rollers, etc.), and an inner ring 240B attached to the motor output shaft 225, e.g., by mounting hardware such as an inner ring extension / concentric collar or a tapered adapter sleeve / lock washer / nut mating member. The stator 220S may be a single-piece structure containing a common core, or it may be segmented and coreless. The rotor 220R may include a rotor structure on one or both axial sides of the stator 220S.In one embodiment, as illustrated, the rotor 220R includes a rotor structure on both axial sides of the stator 220S. In another embodiment, the rotor 220R includes a rotor structure on only one axial side of the stator 220S. Further, for ease of description and understanding, the description herein will refer to a rotor structure on one side of the stator 220S. The rotor structure may include a rotor frame 251, a rotor core 253, and permanent magnets 255. The rotor core 253 may be attached to the rotor frame 251 for rotation therewith. Permanent magnets 255 may be attached to the rotor core 253 for rotation therewith and with the rotor frame 251. The rotor frame 251 may be formed, for example, from a soft magnetic composite, and the rotor core 253 may be made, for example, from electrical steel laminations. In the illustrated embodiments of FIG. Fig. 2A / 2B and Fig. 3A / 3B, the permanent magnets are surface-mounted on the rotor core 253 and are arranged between the rotor core 253 and the stator 220S with air gaps 260 therebetween. In alternative embodiments, the permanent magnets 255 may be contained within the rotor core 253 with the air gaps 260 between the rotor core 253 and the stator 220S.

[0037] The rotor 220R can be movable along the rotational axis (A) of the rotor 220R. Thus, the air gaps 260A / 260B can be varied. In the illustrated embodiments, Fig. 2A and Fig. 3A initially relatively narrow air gaps 260A, whereas Fig. 2B and Fig. 3B secondly shows relatively wide air gaps 260B. The relatively narrow air gaps 260A may represent a minimum achievable air gap for the motor within its mechanical design constraints, e.g., 1 mm. The relatively wide air gaps 260B may represent a maximum achievable air gap for the motor within its mechanical design constraints, e.g., 2 mm. In each of embodiments 2A / 2B and 3A / 3B, the axial displacement of the rotor 220R along the rotational axis (A) may be controlled by hydraulic fluid in variable-volume hydraulic fluid chambers, as further described herein.

[0038] In the embodiment of Fig. 2A and Fig. 2B, the rotor 220R may include at least one hydraulic fluid chamber 270 in the rotor frame 251. Fig. 2A and Fig. 2B illustrate an embodiment that includes two hydraulic fluid chambers 270 that are axially stacked. Fig. 2A and Fig. 2B also illustrates only one hydraulic actuator in section at one angular orientation of the rotor 220R, it being understood that for system balance requirements and total hydraulic force multiplication proportional to the number of hydraulic actuators and hydraulic fluid chambers, which may advantageously enable lower system hydraulic pressures, multiple such hydraulic actuators may be angularly distributed around the entire rotor 220R. Each hydraulic fluid chamber 270 may include a cavity 272 formed in the rotor frame 251 and a vein plate 271 extending radially outward from a cylindrical base 273 surrounding the motor output shaft 225. The cylindrical base 273 is mounted on the motor output shaft 225 such that it is rotationally and axially immobile with respect to the motor output shaft 225.Thus, the hydraulic fluid chamber core plate 271 is rotationally and axially static with respect to the motor output shaft, rotating with it. The rotor frame 251 is mounted to the cylindrical base 273 such that it is axially displaceable. The cavity 272 in the rotor frame 251 encloses the core plate 271 and, together with it, defines the hydraulic fluid chamber 270. Thus, the core plate 271 and the rotor frame rotate together. Elastomer seals 275 can provide hydraulic sealing at the axially displaceable interface of the rotor frame 251 to the cylindrical base 273. Hydraulic fluid can be communicated to and from the hydraulic fluid chamber 270 via passages 277 and a channel 279 through the motor output shaft 225. Volume changes in the hydraulic fluid chamber 270 correspond to an axial displacement of the rotor frame 251.Internal disc springs 281 between the motor output shaft 225 and the rotor frame 251 can provide a preload force when compressed, thus urging the rotor frame 251 away from the stator 220S. Similarly, external disc springs 283 between the bearing inner race 240B (or inner race mounting hardware) and the rotor frame 251 can provide a preload force when compressed, thus urging the rotor frame toward the stator 220S. The hydraulic system of the embodiment of FIG. Fig. 2A and Fig. 2B may be referred to as a linear hydraulic actuator system, wherein the hydraulic actuator effective surface area may correspond to the entire rotor frame surface area facing the wire plates 271 in the hydraulic fluid chambers 270.

[0039] In the embodiment of Fig. 2A and Fig. 2B, the stroke movement of the linear hydraulic actuator corresponds uniquely to the axial displacement of the rotor frame 251. Thus, small air gap changes (e.g., 1 mm) can advantageously be achieved just as quickly, and such a linear hydraulic actuator arrangement may be advantageous in a two-state air gap control that includes a narrow air gap (e.g., 1 mm) at a first axial movement limit of the rotor frame 251 and a wide air gap (e.g., 2 mm) at a second movement limit of the rotor frame 251.

[0040] In operation, pressurized hydraulic fluid may be supplied to the hydraulic fluid chamber 270 via passages 277 and a channel 279 in the motor output shaft 225 to axially displace the rotor 220R away from the stator 220S along the rotational axis (A) of the rotor 220R to increase the air gap 260. Hydraulic fluid may be discharged from the hydraulic fluid chamber 270 via passages 277 and channel 279 in the motor output shaft 225 to axially displace the rotor 220R toward the stator 220S along the rotational axis (A) of the rotor 220R to decrease the air gap 260. In one embodiment, the offset of the rotor 220R to reduce the air gap 260 may be effected by the force exerted by the compressed outer disc springs 283 between the bearing inner race 240B (or inner race mounting hardware) and the rotor frame 251 and the magnetic attraction force of the permanent magnets 255.

[0041] In the embodiment of Fig. 3A and Fig. 3B, the rotor 220R may include at least one hydraulic fluid chamber 270 in the rotor frame 251. In addition, Fig. 4A and Fig. 4B, which schematically illustrate partial sectional views taken along the respective lines 4A-4A and 4B-4B in Fig. 3A or Fig. 3B were taken. Fig. 3A and Fig. 3B illustrate a hydraulic actuator in section at one angular orientation of the rotor 220R, it being understood that multiple such hydraulic actuators may be angularly distributed around the entire rotor 220R for system balance requirements and total hydraulic force multiplication proportional to the number of hydraulic actuators and hydraulic fluid chambers, which may advantageously enable lower system hydraulic pressures. Fig. 4A and Fig. 4B, for example, illustrate two angularly symmetrical (i.e., 180 degrees apart) hydraulic fluid chambers 270 in the rotor frame 251. Each hydraulic fluid chamber 270 may include a cavity 272 formed in the rotor frame 251 and a wire plate 271 extending radially outward from the motor output shaft 225. The wire plate 271 is attached to the motor output shaft 225, for example, by a splined coupling between the motor output shaft 225 and the wire plate 271 such that it is rotationally immobile with respect to the motor output shaft 225 but axially displaceable. Thus, the hydraulic fluid chamber core plate 271 is rotationally static with respect to the motor output shaft and thus rotates and can be axially displaced along the rotational axis (A) of the rotor 220R. The cavity 272 in the rotor frame 251 encloses the core plate 271 and, together with it, defines the hydraulic fluid chamber 270.The rotor frame 251 is mounted on the motor output shaft 225 such that it is rotatable relative to the lead plate 271 and the motor output shaft 225 in response to volume changes in the hydraulic fluid chamber, and is axially displaceable with the lead plate 271 relative to the motor output shaft 225. The axial and rotational movement of the rotor frame 251 is limited to the motor output shaft by a lead screw coupling therebetween. In the illustrated embodiment of FIG. Fig. 3A and Fig. 3B, the lead screw coupling is shown as a low-friction ball screw 290. The ball screw 290 may include ball recirculation through the rotor frame 251 (not shown) or may be free-running with a ball cage (not shown). Volume changes in the hydraulic fluid chamber 270 correspond to rotation of the rotor frame 251 relative to the lead plate 271 and the motor output shaft 225, resulting in axial displacement of the lead plate 271 and the rotor frame 251 by means of the ball screw 290 proportional to the rotation of the rotor frame 251, which corresponds to the thread pitch 291 of the ball screw 290. Thus, the core plate 271 and the rotor frame 251 can move axially together according to volume changes in the hydraulic fluid chamber 270 (ie, rotations of the rotor frame 251 with respect to the core plate 271).Otherwise, the core plate 271 and the rotor frame may be hydraulically locked together, thereby axially and rotationally locking them to the motor output shaft 225. Elastomer seals 275 may provide hydraulic sealing at the axially displaceable interfaces of the rotor frame 251 to the motor output shaft 225 and from the core plate 271 to the motor output shaft 225. Hydraulic fluid may be communicated to and from the hydraulic fluid chamber 270 via passages 277 and a channel 279 through the motor output shaft 225. Internal disc springs 281 between the motor output shaft 225 and the rotor frame 251 may provide a preload force when compressed, thus urging the rotor frame 251 away from the stator 220S.Accordingly, outer disc springs 283 may provide a preload force between the bearing inner race 240B (or inner race mounting hardware) and the rotor frame 251 when compressed, thus urging the rotor frame toward the stator 220S. The hydraulic system of the embodiment of FIG. Fig. 3A, Fig. 3B, Fig. 4A and Fig. 4B may be referred to as a rotating hydraulic actuator system, wherein the hydraulic actuator effective surface area may correspond to the entire rotor frame surface area facing the wire plate 271 in the hydraulic fluid chamber 270.

[0042] In the embodiment in Fig. 3A and Fig. 3B, the reciprocating motion of the rotating hydraulic actuator corresponds to a proportional fractional axial displacement of the rotor frame 251. For example, a 2 mm lead 291 on the ball screw 290 would result in 1 mm of axial displacement of the rotor frame for 180 degrees of its rotation. Thus, small air gap changes (e.g., 1 mm) can advantageously be achieved in a substantially continuous manner, and such a rotating hydraulic actuator assembly can be advantageous in continuous air gap control between a narrow air gap (e.g., 1 mm) at a first limit of axial movement of the rotor frame 251 and a wide air gap (e.g., 2 mm) at a second limit of movement of the rotor frame 251.

[0043] In operation, pressurized hydraulic fluid can be supplied to the hydraulic fluid chamber 270 by means of the passages 277 and a channel 279 in the motor output shaft 225 to rotate the rotor frame 251 with respect to the wire plate 271 and the motor output shaft 225, thereby axially displacing the wire plate 271 and the rotor frame 251 away from the stator 220S by means of the ball screw 290 along the rotational axis (A) of the rotor 220R to increase the air gap 260. The hydraulic fluid can be discharged from the hydraulic fluid chamber 270 by means of the passages 277 and the channel 279 in the motor output shaft 225 to rotate the rotor frame 251 with respect to the wire plate 271 and the motor output shaft 225, thereby axially displacing the wire plate 271 and the rotor frame 251 along the rotational axis (A) of the rotor 220R relative to the stator 220S by means of the ball screw 290 to reduce the air gap 260.In one embodiment, offset of the rotor 220R to reduce the air gap 260 may be effected by the force exerted by the compressed outer disc springs 283 between the bearing inner race 240B (or inner race mounting hardware) and the rotor frame 251 and the magnetic attraction force of the permanent magnets 255.

[0044] It should be acknowledged that in both embodiments of Fig. 2A / Fig. 2B and Fig. 3A / Fig. 3B, all axial displacement forces of the rotor structure are advantageously contained within the rotating components of the rotor and within the shell generally between the axially static bearings 240. Thus, while the bearing inner race 240B and / or the associated inner race mounting hardware may be axially loaded by the outer disc springs 283, the load is ultimately transferred to the motor output shaft 225 and does not traverse the bearing through the rolling elements.

[0045] Fig. 5A and Fig. 5B schematically illustrate a control mechanism for actuated and deactuated hydraulic control states for establishing the axial positions of the rotor 220R corresponding to narrow and wide air gaps 260A and 260B, respectively. Pressurized hydraulic fluid can be supplied to the hydraulic fluid chamber 270 ( Fig. 5A) or hydraulic fluid can be discharged from the hydraulic fluid chamber 270 ( Fig. 5B). A binary fluid control valve (e.g., a solenoid-controlled spool valve) 501 is illustrated in a first state ( Fig. 5A), connecting a pressurized hydraulic fluid from a high-pressure supply side (S) of a hydraulic system 503 (e.g., pressurized line, pump outlet, accumulator, etc.) to the hydraulic fluid chamber 270. The binary fluid control valve 501 is illustrated in a second state ( Fig. 5B), connecting the hydraulic fluid chamber 270 to a low-pressure exhaust side (E) of the hydraulic system 503 (e.g., pump inlet, reservoir, sump, etc.).

[0046] Hydraulic pressure requirements can be determined according to a force balance relationship in the case of the linear hydraulic actuator embodiment of Fig. 2A and Fig. 2B, which is modeled by a force equilibrium relationship, can be determined as follows: P×A=F where P is the minimum hydraulic pressure required to move the hydraulic actuator; A is the total hydraulic actuator effective surface area and F is the force acting against the hydraulic actuator.

[0047] The force F acting against the hydraulic actuator can essentially originate from permanent magnet attraction forces. The total hydraulic actuator effective surface area A can be the sum of the hydraulic actuator effective surface areas of all hydraulic fluid chambers.

[0048] In the embodiment of Fig. 2A and Fig. 2B, two hydraulic fluid chambers are present, each having a respective hydraulic actuator effective surface area A1 and A2, where A = (A1 + A2). Such a relationship can be solved for the minimum hydraulic pressure P required to move the hydraulic actuator. An exemplary motor 220 may have a permanent magnet attraction force of substantially 10,000 N and hydraulic actuator effective surface areas of A1 = A2 = 5,890 mm 2 = 0.00589 m 2 for a total hydraulic actuator surface area A = A1 + A2 = 2 × 0.00589 m 2 = 0.01178 m 2 Therefore, the minimum hydraulic pressure required to move the hydraulic actuator is P = 10000 N / 0.01178 m 2 = 848896 N / m 2(approx. 8.5 bar). The relationship described above ignores a preload force from the inner disc spring 281 between the motor output shaft 225 and the rotor frame 251. Assuming a compressed spring force of substantially half the permanent magnet attraction force, the inner disc spring 281 can reduce the force opposing the hydraulic actuator to substantially 5000 N and the pressure required to move the hydraulic actuator,

[0049] P = 5000 N / 0.01178 m 2 = 424448 N / m 2 (approx. 4.2 bar). Thus, it is recognized that increasing the total hydraulic actuator effective surface area A and / or reducing the force F acting on the hydraulic actuator can reduce the minimum hydraulic fluid pressure P required to move the hydraulic actuator. The total hydraulic actuator effective surface area can be increased by axially stacking hydraulic fluid chambers (e.g., as in the dual chamber arrangements of Fig. 2A and Fig. 2B) and / or configuring a plurality of such arrangements angularly distributed around the entire rotor 220R.

[0050] Hydraulic pressure requirements can be determined according to a torque balance relationship in the case of the rotating hydraulic actuator embodiment of Fig. 3A and Fig. 3B, which is modeled by a torque equilibrium relationship, can be determined as follows: P×(A×r)=T where P is the minimum hydraulic pressure required to move the hydraulic actuator; A is the total hydraulic actuator effective surface area; r is the equivalent radius of the hydraulic actuator effective surface and T is the torque counteracting the hydraulic actuator.

[0051] The force T opposing the hydraulic actuator can essentially originate from permanent magnet attraction forces. The total hydraulic actuator effective surface area A can be the sum of the hydraulic actuator effective surface areas of all hydraulic fluid chambers.

[0052] In the embodiment of Fig. 3A, Fig. 3B, Fig. 4A and Fig. 4B, two chambers are present, each having a respective hydraulic actuator effective surface area A1 and A2, where A = (A1 + A2). Such a relationship can be solved for the minimum hydraulic pressure P required to move the hydraulic actuator. An exemplary motor 220 may have a permanent magnet attraction force of substantially 10,000 N. This force can be related to the torque T opposing the hydraulic actuator via a ball screw relationship as follows: T=F×L2π where F is the permanent magnet attraction force and L is the axial distance per revolution (i.e. the pitch). Thus, in the present example, the torque counteracting the hydraulic actuator is T = (10000 N × 2 mm) / 2π = (10000 N × ,000002 m) / 2π = 0.0032 Nm.

[0053] The exemplary motor 220 can achieve hydraulic actuator effective surface areas of A1 = A2 = 600 mm 2 = 0.0006 m 2 for a total hydraulic actuator surface area A = (A1 + A2) = 2 × 0.0006 m 2 = 0.0012 m 2 The exemplary motor 220 may have a hydraulic actuator effective surface inner radius R1 = 25 mm and an outer radius R2 = 55 mm. Thus, the equivalent radius r of the hydraulic actuator effective surface can be determined from the following relationship: r=R12+R222

[0054] Thus, in the present example, r = √[(25 mm)2 + (55 mm)2] / 2 = 0.000030 m and the minimum hydraulic pressure required to move the hydraulic actuator is P = T / (A × r) = 0.0032 Nm / (0.0012 m 2 × 0.000030 m) = 88889 N / m 2 (approx. 0.89 bar). The relationship described above ignores a preload force from the inner disc spring 281 between the motor output shaft 225 and the rotor frame 251. Assuming a compressed spring force of substantially half the permanent magnet attraction force, the inner disc spring 281 can reduce the force opposing the hydraulic actuator to substantially 5000 N and the pressure P required to move the hydraulic actuator by half, or approximately 44,445 N / m 2(approximately 0.44 bar). Thus, it should be appreciated that increasing a total hydraulic actuator effective surface area A and / or decreasing a force F acting against the hydraulic actuator can reduce the minimum hydraulic fluid pressure P required to move the hydraulic actuator. The total hydraulic actuator effective surface area can be increased by adding hydraulic fluid chambers angularly distributed around the entire rotor 220R. However, it should be understood that multiple hydraulic fluid chambers at the same axial location can further limit the angular range of movement of the hydraulic actuators.

[0055] Fig. Figure 6 illustrates exemplary curves of torque (TQ) versus motor speed (S) corresponding to motor operation at relatively narrow air gaps of 260A (ie Fig. 2A and Fig. 3A) and relatively wide air gaps 260B (ie Fig. 2B and Fig. 3B). The relative motor torque (TQ) is plotted along the vertical axis with increasing torque from zero as the motor moves away from the origin (O), and the relative motor speed (S) is plotted along the horizontal axis with increasing speed as the motor moves away from the origin (O). Narrow air gap 260A operation may exhibit a constant torque output TQ1 from zero speed up to a base speed B1 corresponding to the narrow air gap 260A, after which motor operation in the constant power region at higher speeds exhibits a characteristic reduced torque output up to a terminal speed S1.Operation with a wide air gap 260B may exhibit a constant torque output TQ2 from zero speed up to a base speed B2 corresponding to the wide air gap 260B, after which motor operation in the constant power region at higher speeds exhibits a characteristic reduced torque output up to a terminal speed S2. Thus, it can be appreciated that the narrow air gap 260A may have higher available torque at low motor speeds and a more restricted torque output at higher motor speeds. Further, it can be appreciated that the wide air gap 260B may have lower available torque at low motor speeds but a less restricted torque output at higher motor speeds. The extended speed and torque operating range of the motor with a wide air gap 260B may be attributed to the field weakening achieved by the larger physical air gap.

[0056] In an automotive application, such as an electric drive system 101 in a vehicle 100, as described herein, it will be appreciated that adjustable air gaps in an axial flux motor 220 can provide selective mechanical flow attenuation. Such selective control may be effected in the form of the hydraulic system 503 with binary fluid control valve 501, which is described herein with respect to Fig. 5A and Fig. 5B. The binary fluid control valve 501 may be controlled in response to a control signal from a control module, e.g., the vehicle control unit 103 and / or the engine control unit 105, as described herein with respect to Fig.1. Advantageously, mechanical flux weakening by widening the air gap above the motor base speed, which corresponds to a narrow air gap, can reduce copper losses associated with alternative electrically induced field weakening controls (e.g., current injections). Advantageously, the air gap can be controlled wider at low vehicle loads to reduce motor cogging. Efficiency gains can be realized by operating wider air gaps when stator core losses exceed copper losses. And widening the air gap can advantageously extend useful torque / speed operation in the constant power operating region of the motor above the base speed, which corresponds to a narrow air gap, due to the advantageous mechanical flux weakening. Further, it is recognized that in an automotive application such asIn an electric propulsion system 101 in a vehicle 100 described herein, adjustable air gaps in an axial flux motor 220 may provide selective, operator-selectable vehicle response mode control. For example, an economy mode associated with gentle acceleration and a stable powertrain load may benefit from a wide air gap setting. Similarly, a sport mode associated with vigorous acceleration, eager throttle use, and faster throttle tip-in and tip-out may benefit from a narrow air gap at least within the constant-torque operating range below the engine base speed corresponding to a narrow air gap.

[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms "a" and "an" do not imply a limitation of number, but rather indicate the presence of at least one of the referenced elements. The term "or" means "and / or" unless a context clearly indicates otherwise. Reference throughout the specification to "an aspect" means that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one aspect described herein and may or may not be present in additional aspects. Additionally, it is to be understood that the described elements in the various aspects may be combined in any suitable manner.

[0058] All numerical values ​​herein are assumed to be modified by the term "about," whether expressly stated or not. For the purposes of the present disclosure, ranges may be expressed as from "about" one particular value to "about" another particular value. The term "about" generally refers to a range of numerical values ​​that one of ordinary skill in the art would consider equal to the recited numerical value, that achieves the same function or result, or that generally falls reasonably within manufacturing tolerances of the recited numerical value. Accordingly, numerical values ​​set forth herein are by way of non-limiting examples and may be nominal values, it being understood that actual values ​​may vary from nominal values ​​according to environment, design and manufacturing tolerances, age, and other factors.

[0059] When an element, such as a layer, lamina, region, or substrate, is referred to as being "on" another element, it may be directly disposed on the other element, or there may also be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements. Therefore, unless expressly described as "direct," when the disclosure described above describes a relationship between a first and a second element, that relationship may be a direct relationship, with no other intervening elements between the first and second elements, but it may also be an indirect relationship, with one or more intervening elements (either spatial or functional) between the first and second elements.

[0060] One or more steps in a method may be performed in different orders (or overlapping in time) without altering the principles of the present disclosure. Furthermore, although each of the embodiments has been described above with certain features, one or more of those features described with respect to any embodiment of the disclosure may be implemented in any of the other embodiments and / or combined with their features, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0061] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0062] Unless otherwise specified herein, all examination standards shall be the most recent standard in force as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0063] While the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements without departing from the scope thereof. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within its scope.

Claims

[1] Axial flux motor (220), comprising: a stator (220S); a rotor (220R) including a rotor frame (251) and having a rotation axis (A); an axial air gap (260) separating the stator (220S) and the rotor (220R), the axial air gap (260) corresponding to an axial position of the rotor frame (251); and at least one hydraulic actuator comprising a variable volume hydraulic fluid chamber (270) defined in the rotor frame (251), wherein a change in the volume of the variable volume hydraulic fluid chamber (270) causes a change in the axial position of the rotor frame (251) and a corresponding change in the axial air gap (260) separating the stator (220S) and the rotor (220R); characterized by that the at least one hydraulic actuator comprises a plurality of hydraulic actuators distributed around the rotor (220R) in the circumferential direction. [2] The axial flux motor (220) of claim 1, wherein the at least one hydraulic actuator comprises a linear hydraulic actuator. [3] The axial flux motor (220) of claim 1, wherein the at least one hydraulic actuator comprises a rotating hydraulic actuator. [4] The axial flow motor (220) of claim 1, further comprising a motor output shaft (225) including a passage (277) communicating hydraulic fluid to and from the variable volume hydraulic fluid chamber (270). [5] The axial flow motor (220) of claim 2, wherein the at least one hydraulic actuator comprises a plurality of variable volume hydraulic fluid chambers (270). [6] The axial flow motor (220) of claim 2, further comprising a motor output shaft (225) containing a passage (277) communicating hydraulic fluid to the variable volume hydraulic fluid chamber (270), the variable volume hydraulic fluid chamber (270) comprising a cavity (272) in the rotor frame (251) enclosing a stator plate (271), the stator plate (271) extending radially outward from a cylindrical base (273) surrounding the motor output shaft (225), the cylindrical base (273) being mounted to the motor output shaft (225) such that the cylindrical base (273) is rotationally fixed with respect to the motor output shaft (225) and axially fixed, and the rotor frame (251) being mounted to the cylindrical base (273) such that the rotor frame (251) is axially displaceable. [7] The axial flux motor (220) of claim 3, further comprising a motor output shaft (225) containing a passage (277) communicating hydraulic fluid to the variable volume hydraulic fluid chamber (270), the variable volume hydraulic fluid chamber (270) comprising a cavity (272) in the rotor frame (251) enclosing a wire plate (271), the wire plate (271) extending radially outward from the motor output shaft (225), the wire plate (271) being mounted to the motor output shaft (225) such that the wire plate (271) is rotationally fixed with respect to the motor output shaft (225) and axially displaceable with respect to the motor output shaft (225), and the rotor frame (251) being mounted to the motor output shaft (225) such that the Rotor frame (251) is rotatable and axially displaceable with respect to the motor output shaft (225). [8] The axial flux motor (220) of claim 7, wherein the rotor frame (251) is attached to the motor output shaft (225) by a lead screw coupling. [9] The axial flux motor (220) of claim 8, wherein the lead screw coupling comprises a ball screw (290).

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