Lubricant-supported electric motor with movable raceway and optimization method for its operation

Abstract

The lubricant-supported electric motor includes a stator having an outer raceway and a rotor extending along an axis and rotatably disposed within the stator. The rotor has an inner raceway spaced apart from the outer raceway to define a gap between them. Lubricant is disposed in the gap to support the rotor within the stator. At least one of the outer or inner raceways may be radially movable toward or away from the other to adjust the gap and optimize the operation of the lubricant-supported electric motor.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 905,487, filed September 25, 2019, and U.S. Patent Application Serial No. 17 / 030,792, filed September 24, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to lubricated electric motors. More specifically, this disclosure relates to lubricated electric motors with movable raceways and methods for optimizing their operation. Background Technology

[0004] This section provides a general summary of the background information, and the notes and examples provided in this section are not necessarily prior art of this disclosure.

[0005] Various powertrain systems in automobiles, trucks, and certain off-highway applications draw power from a central prime mover and distribute it to the wheels using mechanical devices such as transmissions, differentials, driveshafts, and drive shafts. These configurations work well when the prime mover can be large or bulky, such as various internal combustion engines (“ICE”). However, more attention has turned to alternative arrangements of prime movers that offer improved environmental performance, eliminate mechanical drivetrain components, and result in lighter vehicles with more passenger and payload space.

[0006] "Wheel-on," "wheel-in," or "near-wheel" motor configurations are alternative arrangements to conventional ICE prime movers, distributing prime mover functionality to each or some of the multiple wheels via one or more motors located on, within, or near the wheels. For example, in one instance, a traction motor supporting the rotor via a central shaft passing through the rotor and rolling element bearings can be used as a "wheel-on," "wheel-in," or "near-wheel" motor configuration. In another instance, a lubricated motor, such as that described in U.S. Application Serial No. 16 / 144,002 (the disclosure of which is incorporated herein by reference), can be used as a "wheel-on," "wheel-in," or "near-wheel" motor configuration. While each motor configuration in these motor configurations is smaller and lighter than that of an internal combustion engine-based prime mover, they each have certain disadvantages and drawbacks.

[0007] For example, using a traction motor in a "wheel-on," "wheel-in," or "near-wheel" configuration still results in an excessively heavy motor, insufficient to withstand impact loads, and unsuitable for wheel-end applications. In other words, current traction motors are large, heavy-duty structures supported by rolling element bearings, which are too heavy and too large for wheel-end applications. Similarly, in automotive or land vehicle applications, using lubricated motors as "wheel-on," "wheel-in," or "near-wheel" motors presents performance issues when subjected to a wide range of forces at a wide speed range in prime mover applications. Specifically, the wide speed range encountered when using lubricated motors in wheel-end applications generates numerous dynamic effects, such as: deflection critical speed; torsional critical speed; torque and translational forces on the rotor associated with rotor magnetic pole forces; half-speed load vectors (e.g., operating at speeds matching rotor mass imbalance forces and rotor weight, or operating at half-order vibrations generated by other powertrain equipment); rotor whirling at half-speed; and others. Current lubricated motor constructions are not robust enough to operate well under all these conditions and the dynamics encountered in wheel-end motor constructions. Furthermore, in "on-wheel" applications, existing lubricated motor constructions cannot be optimized in real-time to achieve the best trade-offs between these dynamic effects and other competing factors such as efficiency, durability, net system power, noise, vibration and harshness (NVH), rotor stability, etc. Therefore, there remains a need to improve "on-wheel," "in-wheel," or "near-wheel" motors, particularly lubricated motors, that can improve performance over the wide speed range encountered in wheel-end prime mover applications and optimize performance in real-time, while also providing the lighter weight and smaller footprint sought from this alternative prime mover implementation. Summary of the Invention

[0008] This invention generally relates to a lubricant-supported electric motor comprising a stator having an outer raceway, and a rotor extending along an axis and rotatably disposed within the stator. The rotor has an inner raceway spaced apart from the outer raceway to define a gap between them, in which lubricant is disposed for supporting the rotor within the stator. One of the outer or inner raceways can be moved relative to the other to adjust the gap between the stator and rotor, and to optimize the operation and performance of the lubricant-supported electric motor in real time. More specifically, one of the outer or inner raceways can be radially moved toward or away from the other to adjust the gap between the inner and outer raceways, advantageously solving and overcoming many dynamic effects arising when using lubricant-supported electric motors in wheel-end applications. For example, during operation, one of the stator or rotor can move radially toward or away from the other based on the actual performance characteristics of the lubricated motor to adjust the clearance between the inner and outer raceways. This, in turn, adjusts the performance characteristics of the lubricant disposed within the clearance to help optimize stiffness, control or alter the critical speed of motor vibration, reduce or control capacity loss due to half-speed load vector effects, and control or change the motor's load capacity over a wider range of operating speeds and dynamic loads, while maintaining parasitic losses. Therefore, a lubricated motor with movable inner or outer raceways provides a wheel-end motor that, when configured as a "on-wheel," "in-wheel," or "near-wheel" motor, can be optimized in real-time based on actual performance characteristics, thus being suitable for impact loads encountered in wheel-end applications. Lubricated motors with movable inner or outer raceways are lightweight and compact, thus contributing to overall design strategies that eliminate weight and size limitations in automotive and land vehicles. Further advantages will be understood from the following more detailed description of the invention. Attached Figure Description

[0009] The accompanying drawings described in this application are for illustrative purposes only for selected embodiments and not all possible implementations, and are not intended to limit the scope of this disclosure.

[0010] Figure 1 This is a schematic diagram of a lubricated electric motor according to one aspect of this disclosure; and

[0011] Figure 2 It is along Figure 1 The cross-sectional view of the lubricant-supported motor, taken from line 2-2, shows the movable raceway that exists on the stator and consists of multiple movable stator segments. Detailed Implementation

[0012] Exemplary embodiments of a lubricant-supported electric motor with movable raceways according to this disclosure will now be described more fully. Each of these exemplary embodiments is provided so that this disclosure is thorough and fully conveys the scope of the inventive concept, features, and advantages to those skilled in the art. To this end, numerous specific details, such as examples of specific components, devices, and mechanisms associated with the lubricant-supported electric motor, are set forth to provide a thorough understanding of each embodiment associated with this disclosure. However, it will be apparent to those skilled in the art that not all the specific details described herein need to be employed, exemplary embodiments may be implemented in many different forms, and therefore should not be construed as limiting the scope of this disclosure.

[0013] Figure 1-2 A lubricant-supported electric motor 10 according to one aspect of the present invention is shown. For example... Figure 1 As shown, the lubricated motor 10 includes a stator 12 and a rotor 14, the rotor 14 extending along axis A and rotatably disposed within the stator 12 to define a gap 16 between them. A lubricant 18 is disposed in the gap 16 to support the rotor 14 within the stator 12 and to provide continuous contact between these components. Therefore, the lubricant 18 can act as a buffer (e.g., suspension) between the rotor 14 and the stator 12 to minimize or prevent contact between them. In other words, the lubricant 18 prevents direct contact between the stator 12 and the rotor 14 and provides the lubricated motor 10 with robustness against shock and vibration loads due to the presence of the lubricant 18. Alternatively, a substantially incompressible lubricant 18 can be used to minimize the gap between the stator 12 and the rotor 14.

[0014] like Figure 1 As shown, the stator 12 defines a channel 20 configured to be in fluid communication with the gap 16 for introducing lubricant 18. However, the channel 20 may be located on any other component of the lubricant-supported motor 10 without departing from the subject matter. According to one aspect, the lubricant 18 may be circulated or pumped through the channel 20 and into the gap 16 in various ways. For example, a high-pressure source (e.g., a pump) 24 for the lubricant 18 may be fluidly coupled to a low-pressure source (e.g., a reservoir) 26 for the lubricant 18, wherein the lubricant 18 may move from the high-pressure source to the low-pressure source, through the channel 20, and into the gap 16. Rotation of the rotor 14 relative to the stator 12 may act as a self-pumping mechanism to drive the lubricant 18 through the channel 20 and into the gap 16.

[0015] like Figure 1As further shown, rotor 14 is interconnected to drive assembly 22 for coupling the lubricated electric motor 10 to one of the vehicle's multiple wheels. For example, in one instance, drive assembly 22 may include a planetary gear system. Alternatively, drive assembly 22 may include one or more parallel shaft gears. Stator 12 and rotor 14 are configured to apply an electromagnetic force between them to convert electrical energy into mechanical energy, moving rotor 14 and ultimately driving the wheel coupled to the lubricated electric motor 10 via drive assembly 22. Drive assembly 20 may provide one or more reduction ratios between the lubricated electric motor 10 and the wheel in response to the movement of rotor 14.

[0016] like Figure 2 As shown, the rotor 10 has an inner raceway 28, and the stator 12 has an outer raceway 30. One of the inner raceway 28 or the outer raceway 30 may be movable relative to the other to adjust the clearance 16 in real time and optimize the performance of the lubricated motor 10. For example, the clearance 16 between the inner raceway 28 and the outer raceway 30 determines the dynamic pressure generated when the lubricated motor 10 is in hydrodynamic mode. The clearance 16 between the inner raceway 28 and the outer raceway 30 also determines the pressure in the bearing housing (clearance area) when the lubricated motor 10 is in static mode. For both reasons, and as will be described in more detail below, the performance of the lubricated motor 10 is optimized by controlling the clearance 16 by moving one of the inner or outer raceways 28, 30 relative to the other (i.e., by moving the stator 12 or rotor 14 radially toward or away from the other).

[0017] In a preferred configuration, the stator 12 can be radially moved toward or away from the rotor 14 to correspondingly radially move the outer raceway 30 toward or away from the inner raceway 28 and adjust the clearance 16. At least one actuator 32 is operatively coupled to the stator 12 to achieve the said radial movement of the stator 12. For example, the actuator 32 may be a hydraulic actuator that applies or releases hydraulic pressure to the back or rear of the stator 12 to cause the stator 12 to move radially toward or away from the rotor 14. Alternatively, the actuator 32 may be a piezoelectric actuator that applies or releases piezoelectric force to the back or rear of the stator 12. Furthermore, the actuator 32 may be a magnetic actuator that applies or releases magnetic force to the back or rear of the stator 12.

[0018] In each configuration of actuator 32, the radial movement of stator 12 toward or away from rotor 14 is achieved in response to a number of different real-time operating conditions of the lubricated motor 10. For example, as Figure 2As shown, the lubricant-supported motor 10 also includes a controller 34, which is configured to be electrically connected to the actuator 32 and is configured to monitor at least one operating condition of the lubricant-supported motor 10, including but not limited to:

[0019] • Motor speed;

[0020] • Lubricant properties - such as viscosity, compressibility (air entrainment);

[0021] • Radial static load of the electric motor - such as rotor weight;

[0022] • Radial dynamic loads on the motor related to the rotor angular position – for example, loads from connecting mechanisms such as gears;

[0023] • Radial dynamic loads on the motor that are independent of the rotor angular position - for example, external shocks or vibrations applied to a lubricated motor;

[0024] • Stability of the lubricant under given operating conditions - for example, operation near the critical resonant speed of the stator-lubricant-rotor system (torque, displacement, or half-speed load vector drive);

[0025] • Bearing load angle – the angle difference between the peak dynamic vector and the load vector; and

[0026] • Rotor whirl - that is, the rotor rotates slightly within the inner circumference of the stator.

[0027] The controller 34 is then configured to adjust the clearance 16 between the inner raceway 28 and the outer raceway 30 in response to any or all of these real-time operating conditions of the lubricated motor 10, such as by actuating the actuator 32 to move the stator 12 radially toward or away from the rotor 14. As described in the introduction, the real-time adjustment of the clearance 16 between the inner raceway 28 and the outer raceway 30 causes the lubricated motor 10 to operate in a manner that produces the correct load capacity, the correct stiffness, minimal lubricant shear loss, controlled lubricant stability, and correct rotor stability.

[0028] In a preferred setting, such as Figure 2 As shown, the stator 12 comprises a plurality of stator segments 36 that collectively define an outer raceway 30, and each stator segment can be independently moved radially toward or away from the inner raceway 24 of the rotor 14 to adjust the clearance 16. In other words, the outer raceway 30 of the stator 12 can be moved radially toward or away from the inner raceway 28 of the rotor 14 in a segmented manner. Although the plurality of stator segments 36 are shown as spanning the entire outer raceway 30 of the stator 12, the plurality of stator segments 36 may also be small segments covering only a smaller subset or portion of the outer raceway 30 without departing from the scope of the disclosure herein. Figure 2As best shown, at least one actuator 32 includes a plurality of actuators 32, each actuator 32 being associated with one of the stator segments 36 and being individually actuated to cause a corresponding one of the stator segments 36 to move radially toward or away from the inner raceway 28 of the rotor 14 in an individual manner.

[0029] In another embodiment, the operation and performance of the lubricant-supported motor 10 can be optimized in real time by controlling the lubricant 18 supplied to the gap 16 through channel 20. For example, the state of the lubricant 18 supplied to the gap 16 determines the hydrodynamic and hydrostatic characteristics of the lubricant-supported motor 10. The characteristics of the lubricant 18, such as pressure, flow resistance, stiffness of the pressure supply, and inertial or flow stabilization effects, determine the performance of the lubricant-supported motor 10 during operation. Therefore, as Figure 1 As best shown, controller 34 is configured to be electrically connected to pump 24 and reservoir 26, and is also configured to use a variety of different techniques to control the state of lubricant 18 supplied to gap 16, thereby controlling the state of lubricant 18 supplied to lubricant-supported motor 10:

[0030] • Provide uniform pressure to all the multiple stator sections 36, where a low-resistance source of lubricant flows through the channel 20;

[0031] • Provide uniform pressure to all the multiple stator sections 36, where the high-resistance source of lubricant flows through the channel 20;

[0032] • A non-uniform supply is provided to the outer raceway 30 defined by multiple stator segments 36, wherein the lubricant supply pressure and flow resistance vary segment by segment; and

[0033] • Control the pressure, flow resistance, supply pressure stiffness, and supply inertia factor (or similar R, C, L) of the lubricant 18 supplied to the gap 18 through the channel 20.

[0034] Therefore, as shown in the examples listed above, lubricant 18 can be supplied as a whole to the lubricant-supported motor 10, or alternatively, it can be supplied to... Figure 2 The selection is shown between corresponding portions of the inner raceway 28 of the stator section 36 and the rotor 14. Lubricant flow restriction can be achieved by using orifices within the channel 20 to create choked flow or capillary action, thereby limiting surface friction of the flow. Pressure stiffness can also be varied using hydraulic accumulators of different sizes. Supply inertia can also be controlled by altering the mass of the lubricant 18 flowing in the lubricant-supported motor 10.

[0035] In another embodiment, the operation and performance of the lubricant-supported motor 10 are also optimized in real time by controlling the properties of the lubricant 18 supplied to the gap 16. The properties of the lubricant 18 determine the hydrodynamic, hydrostatic, and resonant characteristics of the lubricant-supported motor 10. The main characteristics of the lubricant are viscosity, compressibility, and contamination. The viscosity of the lubricant is determined by the chemical composition of the lubricant 18, the additive package of the lubricant, and the temperature of the lubricant 18. The compressibility of the lubricant is primarily a function of the amount of entrained gas present in the lubricant 18. Furthermore, lubricant contamination is controlled by filters, chemical getters, and water / oil separators. Therefore, by communicating with the pump 24 and the reservoir 26, the controller 34 is also configured to adjust the state of the lubricant 18 based on the operating conditions of the lubricant-supported motor 10.

[0036] The net force on the rotor defines the so-called load vector. This load vector has both direction and magnitude. During normal operation, the load vector is primarily affected by the mass of the rotor pulled down by gravity. In some cases, the load vector can be altered by wheel-end movement or by a small imbalance in the magnetic force applied to the rotor by the stator. In an alternative embodiment, the load vector is controlled in such a way that the hydrodynamic operating range of the lubricated motor 10 is improved. This is achieved by controlling the angle of the load vector relative to the rotor's rotational angle. For example, moving the load vector angle at half the rotational speed in the same direction as the rotor 14's rotation will significantly reduce the hydrodynamic bearing pressure. Alternatively, moving the load vector in the opposite direction of the rotor's rotation will increase the hydrodynamic pressure. Thus, in one embodiment, the hydrodynamic pressure can be controlled along with parasitic loads generated in the peak hydrodynamic pressure region. For example, forces on the rotor can be increased or removed by using actuator 32 in a coordinated manner. As described above, these coordinated movements of the actuator, when synchronized with the rotor's rotational motion, can have the effect of increasing or decreasing the hydrodynamic pressure of the bearing.

[0037] Each of the above embodiments of the lubricant-supported motor 10 provides an optimized operating method for the lubricant-supported motor 10, resulting in correct load capacity, correct stiffness, minimal lubricant shear loss, controlled / constrained lubricant stability, and correct rotor stability. These operating procedures are model-based and learned and adjusted based on the actual field performance of the lubricant-supported motor 10. In other words, the above techniques are dynamic elements of the lubricant-supported motor 10 that respond to real-time operating conditions. In some applications, the lubricant-supported motor may have various diameters and various hydrostatic and hydrodynamic surfaces.

[0038] The foregoing description of the embodiments has been provided for illustration and description. It is not intended to be exhaustive or limiting of this disclosure. Even if not specifically shown or described, individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in selected embodiments. Variations are also possible in various ways. Such variations are not considered to depart from this disclosure, and all such variations are intended to be included within the scope of this disclosure.

Claims

1. A lubricant-supported electric motor, characterized in that, The lubricant-supported electric motor includes: The stator has an outer raceway; The rotor extends along the axis and is rotatably disposed within the stator; The rotor has an inner raceway, which is spaced apart from the outer raceway to define a gap between them; A lubricant, disposed in the gap, serves to support the rotor within the stator, and At least one of the outer raceway or the inner raceway may be radially moved toward or away from the other to adjust the gap and optimize the operation of the lubricant-supported motor.

2. The lubricant-supported electric motor according to claim 1, characterized in that, The stator can move radially toward or away from the rotor to adjust the gap between the inner raceway and the outer raceway accordingly.

3. The lubricant-supported electric motor according to claim 2, characterized in that, The lubricant-supported electric motor also includes an actuator operatively coupled to the stator to achieve the radial movement of the stator.

4. The lubricant-supported electric motor according to claim 3, characterized in that, The actuator includes a hydraulic actuator configured to apply or release hydraulic pressure to the stator to achieve the radial movement.

5. The lubricant-supported electric motor according to claim 3, characterized in that, The actuator includes a piezoelectric actuator configured to apply or release piezoelectric force to the stator to achieve the radial movement.

6. The lubricant-supported electric motor according to claim 3, characterized in that, The actuator includes a magnetic actuator configured to apply or release magnetic force to the stator to achieve the radial movement.

7. The lubricant-supported electric motor according to claim 2, characterized in that, The stator includes multiple stator segments that collectively define the outer raceway, and the multiple stator segments are independently radially movable toward or away from the inner raceway of the rotor to adjust the clearance.

8. The lubricant-supported electric motor according to claim 7, characterized in that, The lubricant-supported motor also includes an actuator operatively coupled to each of the plurality of stator segments to achieve the independent radial movement of each of the stator segments.

9. The lubricant-supported electric motor according to claim 8, characterized in that, The lubricant-supported motor further includes a controller configured to be electrically connected to each of the actuators and configured to monitor at least one operating condition of the lubricant-supported motor and adjust the clearance between the inner and outer raceways in response to the at least one operating condition.

10. The lubricant-supported electric motor according to claim 9, characterized in that, The at least one operating condition of the lubricant-supported motor includes: the speed of the lubricant-supported motor, the properties of the lubricant, the radial static load of the motor, the radial dynamic load of the motor related to the rotor angular position, the radial dynamic load of the motor independent of the rotor angular position, the load angle of the lubricant-supported motor, or rotor whirl.

11. The lubricant-supported electric motor according to claim 9, characterized in that, The stator is defined as a channel fluidly communicating with the gap and the high-pressure and low-pressure sources of the lubricant. The controller is configured to be electrically communicating with the high-pressure and low-pressure sources and to control the properties of the lubricant supplied to the gap based on the operating conditions of the lubricant-supported motor.

12. The lubricant-supported electric motor according to claim 11, characterized in that, The controller is configured to control at least one of the following: viscosity, temperature, additive package, or compressibility of the lubricant, based on the operating conditions of the lubricant-supported motor.

13. The lubricant-supported electric motor according to claim 11, characterized in that, The controller is further configured to adjust the supply of lubricant to the gap based on the operating conditions of the lubricant-supported motor.

14. The lubricant-supported electric motor according to claim 1, characterized in that, The rotor is operatively connected to a final drive unit, which is interconnected with the vehicle's wheels.

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