Rotor flux control in permanent magnet electric machines

Abstract

Rotor flux control in a permanent magnet (PM) motor involves controlling fluid flow through a rotor based on a torque-to-speed operating point of the PM motor. When the torque at the given speed falls below a predetermined threshold, the rotor receives a reduced fluid flow compared to when the torque is above the threshold. Fluid flow through the stator is controlled in an opposite manner relative to fluid flow of the rotor such that the stator receives an increased fluid flow when the rotor experiences a reduced fluid flow. The method makes it possible to effectively control the magnetic flux of the rotor, thereby enhancing the performance and efficiency of the PM motor during various operating conditions.

Description

Technical Field

[0001] The present disclosure relates to rotating electrical machines. More particularly, the present disclosure relates to alternating current (AC) permanent magnet (PM) electrical machines. Background Art

[0002] AC PM motors operate in a torque and speed space defined within the peak performance boundaries and are typically divided between constant torque and constant power regions. AC PM motors can be designed with permanent magnets with large flux density, which affects motor performance. Larger flux density is typically desired in AC PM motors, except at low torque outputs, especially at higher speeds above the motor base speed, where back electromotive force (EMF) becomes more pronounced and motor efficiency suffers due to higher copper and iron losses from the additional current required for field weakening operation. Samarium cobalt and neodymium are examples of magnets commonly used in high power motor applications (e.g., automotive powertrains). Such magnets experience reduced flux density when temperature increases. Temperature-dependent flux density changes are typically reversible below a critical temperature, but may be irreversible if the critical temperature is exceeded. Therefore, active motor cooling can be used to keep the magnet temperature below such a critical temperature and may include circulating oil through the rotor and stator. Summary of the invention

[0003] In an exemplary embodiment, a method for rotor flux control in a permanent magnet (PM) motor may include controlling fluid flow through a rotor based on an operating point of the PM motor such that the rotor receives a reduced fluid flow when the operating point of the PM motor is below a predetermined threshold relative to the fluid flow when the operating point of the PM motor is above a predetermined threshold.

[0004] In addition to one or more features described herein, the operating point of the PM motor may include a PM motor torque, and the predetermined threshold may include a torque threshold.

[0005] In addition to one or more features described herein, the operating point of the PM electric machine may include a PM electric machine torque at a machine speed, and the predetermined threshold may include a torque threshold at the machine speed.

[0006] In addition to one or more features described herein, the operating point of the PM motor may include a PM motor torque at a machine speed at a DC voltage, and the predetermined threshold may include a torque threshold at a machine speed at a DC voltage.

[0007] In addition to one or more features described herein, a method for rotor flux control in a PM motor may also include controlling fluid flow through a stator of the PM motor opposite to the fluid flow received by the rotor such that the stator receives increased fluid flow when the rotor receives decreased fluid flow.

[0008] In addition to one or more features described herein, controlling fluid flow through the rotor may include controlling the fluid flow with a solenoid valve.

[0009] In addition to one or more features described herein, fluid flow through the rotor is controlled based on the operating point of the PM motor such that the rotor receives a reduced fluid flow when the operating point of the PM motor is below the predetermined threshold, relative to the fluid flow when the operating point of the PM motor is above a predetermined threshold, occurring above a predetermined PM motor speed.

[0010] In addition to one or more features described herein, the predetermined PM motor speed may include a base speed of the PM motor.

[0011] In another exemplary embodiment, a propulsion system for an electrified vehicle may include a permanent magnet (PM) motor, a gear unit connected to the PM motor, a cooling system for controllably circulating a fluid through a passage in a rotor of the PM motor, the cooling system including a variable force solenoid valve that receives a pressurized fluid and controls circulation of the pressurized fluid through the rotor in response to a control command, and a controller that provides a control command to achieve a fluid flow through the rotor based on an operating point of the PM motor such that the fluid flow through the rotor is reduced when the operating point of the PM motor is below a predetermined threshold relative to the fluid flow through the rotor when the operating point of the PM motor is above a predetermined threshold.

[0012] In addition to one or more features described herein, the operating point of the PM motor may include a PM motor torque, and the predetermined threshold may include a torque threshold.

[0013] In addition to one or more features described herein, the operating point of the PM electric machine may include a PM electric machine torque at a machine speed, and the predetermined threshold may include a torque threshold at the machine speed.

[0014] In addition to one or more features described herein, the operating point of the PM motor may include a PM motor torque at a machine speed at a DC voltage, and the predetermined threshold may include a torque threshold at a machine speed at a DC voltage.

[0015] In addition to one or more features described herein, a cooling system for controllably circulating a fluid through passages in a rotor of a PM motor diverts fluid that is not circulated through passages in the rotor of the PM motor to pass through a stator of the PM motor such that the stator receives increased fluid flow while the rotor receives reduced fluid flow.

[0016] In addition to one or more of the features described herein, the controller provides a control command to achieve fluid flow through the rotor based on the operating point of the PM motor, so that the fluid flow through the rotor is reduced when the operating point of the PM motor is below a predetermined threshold relative to the fluid flow through the rotor when the operating point of the PM motor is above a predetermined threshold, and a control command above a predetermined PM motor speed can also be provided.

[0017] In yet another exemplary embodiment, a method for rotor flux control in a permanent magnet (PM) motor may include controlling fluid flow through a rotor based on an operating point of the PM motor including a torque-to-speed relationship such that the rotor receives a reduced fluid flow when the torque of the PM motor at the speed of the PM motor is below a predetermined torque threshold relative to the fluid flow when the torque of the PM motor at the speed of the PM motor is above a predetermined torque threshold, and controlling fluid flow through a stator of the PM motor oppositely relative to the fluid flow through the rotor such that the stator receives an increased fluid flow when the rotor receives a reduced fluid flow.

[0018] In addition to one or more of those described herein, the operating point of the PM machine may also include a DC link voltage, and controlling fluid flow through the rotor is based on the operating point of the PM machine in terms of torque versus speed and the DC link voltage.

[0019] In addition to one or more features described herein, controlling fluid flow through the rotor may include controlling the fluid flow with a solenoid valve.

[0020] In addition to one or more features described herein, fluid flow through the rotor is controlled based on an operating point of the PM motor such that the rotor receives reduced fluid flow when the torque of the PM motor is below a predetermined torque threshold at a speed of the PM motor, relative to fluid flow when the torque of the PM motor is above a predetermined torque threshold at a speed of the PM motor, occurring above a predetermined PM motor speed.

[0021] In addition to one or more features described herein, the predetermined PM motor speed may include a base speed of the PM motor.

[0022] In addition to one or more features described herein, fluid flow through the rotor is controlled based on an operating point of the PM motor such that the rotor receives the reduced fluid flow when the torque of the PM motor at the speed and the DC link voltage of the PM motor is below the predetermined torque threshold, relative to the fluid flow when the torque of the PM motor at the speed and the DC link voltage of the PM motor is above the predetermined torque threshold, occurring above a predetermined PM motor speed.

[0023] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, advantages and details appear, by way of example only, in the following detailed description, which refers to the accompanying drawings, in which:

[0025] Figure 1 is a schematic diagram of an electric vehicle having a drive system including a cooled rotor according to various embodiments;

[0026] Figure 2 According to various embodiments Figure 1 A schematic diagram of a cooling system for a drive system;

[0027] Figure 3 According to various embodiments Figure 1 A schematic cross-sectional view of a portion of a drive system;

[0028] Figure 4 is a diagram showing various embodiments Figures 1 to 3 A data flow diagram of the elements of the cooling control system of the drive and cooling system; and

[0029] Figure 5 is a flow chart of a process for rotor flux control according to various embodiments. DETAILED DESCRIPTION

[0030] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. Throughout the drawings, corresponding reference numerals indicate identical or corresponding parts and features. The description of components and features in one drawing is understood to apply to components and features in other drawings sharing the same reference numeral to the extent that such components and features cannot be otherwise distinguished by one of ordinary skill in the art by inspection of the drawings or by the additional written description herein.

[0031] Embodiments of the present disclosure may be described herein in terms of functional and / or logical block components and various processing steps. It should be understood that such block components may be implemented by any number of hardware, software, and / or firmware components configured to perform specified functions. For example, embodiments of the present disclosure may employ various integrated circuit components, such as memory elements, digital signal processing elements, logic elements, lookup tables, etc., which may perform various functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any number of autonomous driving systems including cruise control systems, automatic driver assistance systems, and autonomous driving systems, and that the vehicle system described herein is merely an exemplary embodiment of the present disclosure.

[0032] For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, and other functional aspects of the system (and the various operating components of the system) may not be described in detail herein. In addition, the connecting lines shown in the various figures included herein are intended to represent example functional relationships and / or physical connections between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in the embodiments of the present disclosure.

[0033] refer to Figure 1 , which illustrates certain features of an electrified vehicle 20 in functional block diagram form. In various embodiments, the electrified vehicle 20 includes a plurality of wheels 22. The electrified vehicle 20 may be any of a number of different types of automobiles, such as a sedan, a wagon, a truck, or a sport utility vehicle, and may be two-wheel drive (i.e., rear-wheel drive or front-wheel drive), four-wheel drive, or all-wheel drive. In other embodiments, the electrified vehicle 20 may be any of another different type of land, sea, or air vehicle having a motor that supplies power to a drive device, such as to propel the electrified vehicle 20. Figure 1 As shown, the electrified vehicle 20 includes a body 24 supported by wheels 22. The body 24 may be disposed on or integrated with a chassis (not shown). In various embodiments, the electrified vehicle 20 may be Figure 1 2. For example, in some embodiments, the number of wheels 22, the drive shaft, and / or the style of the body 24 may vary.

[0034] An electric drive system having a propulsion system 26 is included in the electrified vehicle 20. Generally, the propulsion system 26 may include an electric machine 30, a gear unit 32, and a propulsion control system 34. Figure 1In the illustrated embodiment, the propulsion system 26 supplies torque to drive the wheels 22 via a driveline 36. In various embodiments, the driveline 36 can be configured to couple the front wheels 22 to the propulsion system 26, such as via a shaft 38, a gearbox 40, and an axle 42. In other embodiments, the driveline 36 can be configured to couple the rear wheels 22 to the propulsion system 26, such as via a shaft 44, a gearbox 46, and an axle 48. As shown, the driveline 36 is configured to couple all four wheels 22 to the propulsion system 26.

[0035] The motor 30 can be any of various types of electric motors that operate to supply rotational torque to the drive train 36, such as functioning as a traction motor of the electrified vehicle 20. The motor 30 can also operate as a generator that receives rotational torque from the drive train 36. The gear unit 32 connects the motor 30 to the drive train 36 and is operable to transfer torque in either direction. The gear unit 32 can include a plurality of meshing gears to transfer torque to and from the drive train 36, and can be configured with a single fixed gear ratio. In an embodiment, the motor 30 and the gear unit 32 can be integrated into the electric drive unit. The gearboxes 40, 46 transfer torque from their respective shafts 38, 44 to their respective axles 42, 48, and can provide a differential function in diverting torque to the wheels 22. The gearboxes 40, 46 can also each have a single fixed gear ratio.

[0036] The motor 30 is powered by a rechargeable energy storage system (RESS) 50. The RESS 50 is mounted on the body 24 of the electrified vehicle 20 and is electrically connected to a power electronics device 52. In the current embodiment, the RESS 50 includes at least one rechargeable battery having a set of battery cells. In other embodiments, the RESS 50 includes another type of electrical energy storage device. The power electronics device 52 may include various electric vehicle components, such as a power inverter module that drives the motor 30, an accessory power module, an onboard charger module, etc. Therefore, the RESS 50 can be connected to the power inverter module via a DC link with a DC link voltage corresponding to the RESSDC voltage.

[0037] The controller 54 is coupled to the motor 30, the power electronics 52, the RESS 50, the propulsion system 26, and various sensors as described herein. As will be appreciated, the controller 54 can be coupled to a number of other devices and systems of the electrified vehicle 20. The controller 54 utilizes data and information from various sensors and measurements. Typically, the controller 54 is configured to receive inputs from various sensors that are configured to generate signals proportional to various physical input parameters associated with the electrified vehicle 20, its subsystems, and other related systems. For example, based on these parameters, the controller 54 is configured to operate the motor 30 at various rotational speeds and in both rotational directions to propel the vehicle at various speeds and in forward and backward directions.

[0038] like Figure 1 As shown, the controller 54 is part of or includes a computer system 56. It should be understood that the controller 54 may be different from Figure 1 . The controller 54 may be configured as any number of controllers and / or microcontrollers that communicate with each other. For example, separate individual controllers may control various aspects of the propulsion system 26 and the RESS 50. Therefore, reference to a controller includes arrangements having one or more controllers. The controller 54 is coupled to the propulsion control system 34, such as coupled to the propulsion system 26, and coupled to other devices and systems of the electrified vehicle 20. The controller 54 may receive information from various sources, process the information, and provide control commands based on the information to achieve results such as the operation of the electrified vehicle 20 and its systems (including the propulsion control system 34). In the depicted embodiment, the controller 54 includes a processor 62 and a memory device 64, and is coupled to a storage device 66. The processor 62 performs the computational and control functions of the controller 54, and may include any type of processor or multiple processors, a single integrated circuit such as a microprocessor, or any suitable number of integrated circuit devices and / or circuit boards that work in cooperation to complete the functions of the processing unit. During operation, the processor 62 may execute one or more programs and may use data, each of which may be contained within the storage device 66, and thus, the processor 62 controls the general operation of the controller 54 when performing the processes described herein, such as the processes and methods described in more detail herein.

[0039] The memory device 64 may be any type of suitable memory. For example, the memory device 64 may include volatile and non-volatile storage devices such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile processor that can be used to store various operating variables when the memory 62 is powered off. The memory device 64 may be implemented using any of a number of known memory devices, such as PROM (programmable read-only memory), EPROM (erasable PROM), EEPROM (electrically erasable PROM), flash memory, or any other electrical, magnetic, optical, or combination memory device capable of storing data, some of which represent executable instructions used by the controller 54. In the depicted embodiment, the memory device 64 may store the above-mentioned programs as well as one or more stored values ​​of data, such as for short-term data access.

[0040] The storage device 66 stores data, such as long-term data access for use in automatically controlling the electrified vehicle 20 and its systems. The storage device 66 can be any suitable type of storage device, including direct access storage devices, such as disk drives and flash memory systems. The storage device 66 includes a non-transitory computer-readable medium configured to store data, such as on the electrified vehicle 20. In an exemplary embodiment, the storage device 66 includes a source from which the memory device 64 receives a program that performs one or more embodiments of one or more processes of the present disclosure. In another exemplary embodiment, the program can be directly stored in the memory device 64 and / or otherwise accessed by the memory device 64. The program represents executable instructions used by the controller 54 to process information and control the electrified vehicle 20 and its systems, including the propulsion control system 34 and the cooling system 68 associated with the motor 30 and the gear unit 32, as further described herein.

[0041] As part of the cooling system 68, the gear unit 32 includes a sump 70 containing a supply of fluid (in this case oil) circulated by a pump 72. The pump 72 may be electrically driven and, in this embodiment, is coupled to the controller 54 for controlled operation. Typically, the pump 72 provides a pressurized fluid 88 for controlled circulation within the gear unit 32 and the motor 30. A cooling control system 74 is provided, which typically includes the controller 54, a control valve 76, a temperature sensor 78 disposed in the sump 70, a throttle position sensor 80, a DC voltage sensor 51, a vehicle speed sensor 82, and a machine speed sensor 28, and is coupled to the pump 72. In other embodiments, the cooling control system 74 may typically monitor other parameters of the propulsion system 26 or the electrified vehicle 20, and may command control actions based on those other parameters. Although components of the propulsion control system 34 and the cooling control system 74 are depicted as part of the same system, it should be understood that in certain embodiments, these features may include multiple systems. Additionally, in various embodiments, the cooling control system 74 may include all or a portion of, and / or may be coupled to, various other vehicle devices and systems, such as, in particular, the propulsion system 26 and / or other systems of the electrified vehicle 20 .

[0042] refer to Figure 2 , a portion of the cooling system 68 is shown in schematic form and with increased detail. The motor 30 includes a stator 84 and a rotor 86. The sump 70 contains a quantity of fluid 88, in this embodiment oil. The pump 72 is driven by an electric motor 73, which is coupled to the controller 54. The pump 72 delivers a supply 90 of fluid 88 from the sump 70 to each of the gear unit 32, the stator 84, and the rotor 86 through a conduit system 92. The fluid 88 returns to the sump 70 after flowing through each of the gear unit 32, the stator 84, and the rotor 86. The supply 90 of fluid 88 directed to the gear unit 32 can be delivered at a set design flow rate for the output pressure of the pump 72 within the conduit system 92, and the supply 90 delivered to the stator 84 is also delivered at a set design flow rate, in each case, such as by including a calibrated orifice size in the conduit system 92.

[0043] The supply 90 of fluid 88 directed to the rotor 86 passes through the control valve 76. Thus, by varying the degree to which the control valve 76 is opened, the flow of fluid 88 can be controlled according to identifiable parameters of the propulsion system 26 and / or the electrified vehicle 20. In the current embodiment, the control valve 76 is a variable force solenoid valve that includes an electric actuator in the form of a solenoid 94. Thus, the control valve 76 controls the pressure (and therefore the flow) of the fluid 88 delivered to the rotor 86, for example in proportion to the current level of the signal supplied to the solenoid controlled by the controller 54. A higher pressure output from the control valve 76 results in an increase in the flow of the fluid 88 supplied to cool the rotor 86. A lower pressure output from the control valve 76 results in a decrease in the flow of the fluid 88 supplied to cool the rotor 86. The control can be calibrated to optimize the fluid flow, thereby balancing operating efficiency with cooling requirements under a range of operating conditions of the motor 30. In other embodiments, different types of valve actuators may be used. For example, other electrically driven translatable or rotatable actuator elements may be used to control orifice size, or selective valve state open (full flow) or closed (no flow).

[0044] Reference Figure 3 , a schematic cross-section of a portion of the motor 30 illustrates the location of the control valve 76 in this embodiment. The rotor 86 is rotatably supported within the stator 84 and on the housing 102 of the motor 30 by a bearing assembly 104. The rotor 86 includes a shaft 106 and a core assembly 108 supported on the shaft 106. The core assembly 108 can be made of stacked laminates 108A of electrical steel between end plates 108B. The stator 84 can also be made of stacked laminates of electrical steel. An output gear 110 is fixed to the shaft 106 and meshes with a gear 112 of the gear unit 32 to supply torque from the motor 30. The shaft 106 has a longitudinal bore 114 that opens through its end 116 and registers with a cavity 118 in the housing 102. The cavity 118 forms part of the conduit system 92 that is supplied with fluid 88 by the pump 72.

[0045] The guide 120 is disposed at the interface between the shaft 106 and the housing 102. The guide 120 includes a cylindrical portion 122 disposed in the cavity 118, a flange 124 extending radially outward from the cylindrical portion 122 and abutting the housing 102 at a shoulder 126, and a pin 128 extending into the bore 114. The pin 128 extends longitudinally from the flange 124 on a side of the flange 124 opposite the cylindrical portion 122 and is sized to fit within the bore 114. The pin 128 includes a tapered end 130 at its end opposite the flange 124. The tapered end 130 has a diameter that is substantially smaller than the diameter of the bore 114. The bore 132 extends from its end 116 in the cavity 118 through the guide 120 to the tapered end 130 in the bore 114. Thus, the guide 120 provides a flow path from the cavity 118 through the bore 132 to the bore 114. The shaft 106 includes a plurality of openings 136 extending radially therethrough and arranged to align with the holes 114 and fluid passages formed in the core assembly 108 of the rotor 86. Thus, the fluid 88 enters these rotor fluid passages via the holes 132, 114 and the openings 136 to cool the rotor 86. The stator may have similar fluid passages formed therein, wherein the fluid 88 enters therein via the conduit system 92 including calibrated orifices. In the present embodiment, since the conduit system 92 supplies the fluid 88 to both the rotor 86 and the stator 84 as well as the gear unit 32, a reduction in the fluid flow to the rotor results in an increase in the fluid flow to the stator 84 and the gear unit 32.

[0046] The control valve 76 is positioned in the bore 132 of the guide 120 to control the fluid 88 flowing therethrough, thereby being able to control the amount of fluid 88 allowed to enter through the rotor 86. The solenoid 94 is disposed in the cavity 118. The solenoid 94 includes a coil 138 and a core 134 that moves in response to a magnetic field generated by the coil 138 (such as in response to an electric current supplied under the control of the controller 54). The control valve 76 includes a spool 142 connected to the core 134. The guide 120 serves as a valve body containing the spool 142. An orifice 144 is disposed through the guide 120 to supply fluid from the cavity 118 to the spool 142. The spool 142 includes an orifice 146 that is aligned with the orifice 144 to varying degrees depending on the positioning of the spool 134. The orifice 146 is aligned with a longitudinal hole 148 in the spool 142 that leads to the bore 132. The sizes of the orifices 144 and 146, the longitudinal bore 148, and the bore 132 are designed to deliver the maximum flow required by the rotor 86 under all operating conditions when the control valve 76 is fully open. The movement of the spool 142 by the core 138 can result in a fully open state, a series of throttling states, or a fully closed state of the control valve 76, depending on the cooling needs of the rotor 86.

[0047] When assembling the motor 30, the control valve 76 is inserted into the bore 132 and then the guide 120 is inserted into the cavity 118 until the flange 124 engages the shoulder 126 of the housing 102. The bearing assembly 104 may be positioned into the housing 102 before or after the guide 120 is inserted. The rotor 86 is then moved into position with the tapered end 130 of the guide 120 entering the bore 114 and guiding the shaft 106 into an axially centered position. As the shaft 106 moves closer to the flange 124, the guide 120 centers the shaft 106 relative to the bearing assembly 104 so that the shaft 106 can be moved into its assembled position with its end 116 engaging the flange 124 and extending through the bearing assembly 104. Thus, in addition to providing a controlled flow path for the fluid 88, the guide 120 also serves a guiding function when assembling the rotor 86 to be supported by the bearing assembly 104.

[0048] refer to Figure 4 , according to various embodiments, elements of a cooling control system 74 for dynamic flow control are shown in data flow diagram form. As will be appreciated, various embodiments of a cooling control system 74 according to the present disclosure may include any number of modules embedded within a controller 54 or multiple controllers, which may be combined and / or further divided to implement the systems and methods described herein. Inputs to the cooling control system 74 may be received from various sensors of the electrified vehicle 20, including a temperature sensor 78, a throttle position sensor 80, a DC voltage sensor 51, a vehicle speed sensor 82, and a machine speed sensor 28, received from other control modules (not shown) associated with the electrified vehicle 20, and / or determined by other submodules (not shown) within the controller 54. For simplicity, the description may refer to one controller 54, which means one or more controllers. The cooling control system 74 may be configured to include a flow requirement module 150, a compound rotor flow module 152, a pump flow module 154, a cooling system control module 156, and a data memory 158.

[0049] In various embodiments, the flow request module 150 receives as inputs sensed data 160, such as from the data storage 158, and flow model data 162. The sensed data 160 may include data from the temperature sensor 78, the throttle position sensor 80, the DC voltage sensor 51, the vehicle speed sensor 82, the machine speed sensor 28, and other sensors as desired to take into account parameters selected for control purposes. The flow model data 162 may include a model of the propulsion system 26 that relates the sensed data 160 to the flow request. As an example, the model for flow may include a two-dimensional lookup table that plots flow as a function of torque demand indicated by the throttle position sensor 80 versus motor speed indicated by the machine speed sensor 28. Additionally, the model for flow may also include a three-dimensional lookup table that plots flow as a function of torque demand indicated by the throttle position sensor 80 versus motor speed indicated by the machine speed sensor 28 versus DC voltage indicated by the DC voltage sensor 51. Similar methods may be used for other parameters. In other embodiments, a mathematically based model may be constructed using commercially available modeling software and / or by characterizing various parameters indicative of the cooling load requirements of the rotor 86. A similar approach may be used for all models described herein. The flow requirement module 150 generates flow data 164, which may include a plurality of flow requirements based on different parameters. Thus, the flow data 164 includes a plurality of data points representing the flow requirements of the rotor 86 based on different parameters. The flow data 164 obtained from the flow model data 162 and / or the sensed data 160 is stored in the data storage 158.

[0050] In various embodiments, the composite rotor flow module 152 receives as input the flow data 164 and the combined model data 166, for example, from the data storage 158. Because the flow data 164 includes multiple data points representing the flow requirements of the rotor 86 based on different parameters, the composite rotor flow module 152 calculates a single flow requirement for setting the control valve 76 based on the current parameters. The combined model data 166 may be stored in the data storage when the electrified vehicle 20 is manufactured, and associates various values ​​of the flow data 164 with a single calibrated flow requirement of the rotor 86. The composite rotor flow module 152 uses the flow data 164 and the combined model data 166 to calculate the required flow data 168 value of the control valve 76. In some embodiments, the composite rotor flow module 152 may select the value with the largest magnitude in the flow data 164, thereby ensuring that the supplied flow meets all requirements. In other embodiments, the combined model data 166 may weight the individual flow requirements and calculate a composite value that is different from any individual value. For example, a number of parameters may compound the cooling requirements and result in calculating a flow that matches the composite amount. The value of the required flow data 168 represents the flow rate of the fluid 88 supplied to the rotor 86 through the control valve 76. The required flow data 168 is stored in the data memory 158.

[0051] In various embodiments, the pump flow module 154 receives as inputs the desired flow data 168, the pump model data 170 (such as from the data storage 158), and the pump requirement data 172 (such as from a remote module that determines the pump flow requirements of the gear unit 32 and the stator 84). In some embodiments, the pump requirement data 172 can be a fixed constant value regardless of the operating parameters, where these values ​​are determined during product development to ensure sufficient flow under all operating conditions. In other embodiments, the pump requirements can be determined in real time based on current parameters. In an embodiment, the pump flow module 154 adds the pump flow requirements of the gear unit 32 and the stator 84 received in the pump requirement data 172 to the desired flow data 168 to produce a value for the total pump flow data 174.

[0052] Using the total pump flow data 174, the required flow data 168, the pump model data 170, and the control valve model data 176 (such as received from the data memory), the cooling system control module 156 generates control data 180 to control the cooling system 68, such as by setting the opening state of the control valve 76 via a variable current signal, and setting the speed of the pump 72 via a variable current and / or voltage signal. For example, a lookup table or multiple lookup tables can be used to associate the flow requirement with the current supply based on the flow. In other embodiments, a more complex model can be used, where the model is constructed using computational modeling software for analyzing the propulsion system 26 and / or using characteristic testing.

[0053] refer to Figure 5 , a method 200 for operation of the cooling control system 74 is shown. As will be understood from this disclosure, the order of operation of the steps within the method 200 is not limited to the following. Figure 5 200 is not performed in the order shown, but may be performed in one or more variations of the order where applicable and in accordance with the present disclosure. In various embodiments, the method 200 may be arranged to run based on one or more predetermined events, and / or may run continuously during operation of the electrified vehicle 20. The method 200 reads 202 the torque demand indicated by the throttle position sensor 80. The input on the throttle is an indication of how fast and how much the electrified vehicle 20 is accelerating, and determines the amount of torque to be supplied by the motor 30. The torque demand is related to heat generation and generally indicates the amount of cooling required for system components. The amount of cooling required for the rotor 86 can be determined based on modeling using computing software and / or by experimental / characteristic testing for various torque requirements. Therefore, the torque demand can be equivalent to the flow required for the rotor 86, such as by using a lookup table or another model. The method 200 calculates 204 the flow of the fluid 88 required to cool the rotor 86 based on the torque demand that produces the calculated flow 204.

[0054] The method 200 reads 206 the DC voltage indicated by the DC voltage sensor 51. The DC voltage indicates how much current the system may need to meet the power requirements of the machine. For equivalent power requirements, higher currents are required at lower voltages. The current is directly related to the copper losses of the machine. The flow rate required for the rotor 86 can be determined based on modeling using calculation software and / or through experimental / characteristic testing for various DC voltages. Therefore, the DC voltage can be equated to the flow rate required for the rotor 86, such as by using a lookup table or another model. The method 200 calculates 208 the flow rate of the fluid 88 required to cool the rotor 86 based on the DC voltage that produces the calculated flow rate 208.

[0055] The method 200 reads 210 the speed of the motor 30 indicated by the vehicle speed sensor 82 or the machine speed sensor 28. The speed sensor 82 can be a sensor for determining the speed of the electrified vehicle 20 and is directly related to the rotational speed of the motor 30. The machine speed sensor 28 is directly related to the rotor speed and can be used for motor control. The rotational speed of the motor 30 is an indication of how much heat the rotor 86 generates. The flow required for the rotor 86 can be determined based on modeling using computing software and / or by experimental / characteristic testing for various speeds. Therefore, the speed can be equated to the flow required for the rotor 86, such as by using a lookup table or another model. The method 200 calculates 212 the flow of the fluid 88 required to cool the rotor 86 based on the speed that produces the calculated flow 212.

[0056] The method 200 calculates 214 a composite flow for cooling the rotor 86. Given the calculated flows 204, 208, and 212, the individual flow requirements of the rotor 86 are determined. In an embodiment, the maximum magnitude of the calculated flows 204, 208, and 212 may be selected to ensure that the calculated composite flow 214 satisfies all of the individual flows. In other embodiments, each of the calculated flows 204, 208, and 212 may be weighted and aggregated to calculate 214 a composite flow that takes all parameters into account. For example, a multi-dimensional lookup table may be used to factor in each of the calculated flows 204, 208, and 212 to give a single flow that factors in any cumulative effects of the parameters. The composite flow calculated 214 is the flow to be achieved by the opening setting of the control valve 76.

[0057] The method 200 adds the calculated 214 composite flow to the flow requirement of the pump 72 for supplying the gear unit 32 and the stator 84 to determine 216 the pump flow. The determined 216 pump flow may be a reduced value of the calculated 214 composite flow of the rotor 86. Because the control valve 76 is throttled, more pressure retention is available for supplying the gear unit 32 and the stator 84. Therefore, a compound efficiency improvement can be achieved, which benefits from the reduction of the resistance of the rotor 86 and the reduction of the energy consumption of the electric motor 73 of the pump 72. The method 200 sets 218 the control valve 76 to provide the calculated 214 composite flow to the rotor 86, for example by selecting a corresponding current (or voltage) value from a lookup table, and sets the pump speed to provide the required flow from the pump 72, for example by selecting a current (or voltage) value from another lookup table. Setting the opening state of the control valve 76 via a variable current and / or voltage signal and setting the speed of the pump 72 via a variable current and / or voltage signal enables dynamically controlled fluid flow to be provided according to operating conditions. The setting of the control valve 76 corresponds to the cooling demand of the rotor 86. When the cooling demand of the rotor 86 decreases, the speed setting of the pump 72 can be reduced, thereby further compounding the savings due to the need for less electrical energy to rotate the rotor 86 and the electric motor 73 of the pump 72. For example, when the maximum torque demand is applied to the motor 30, such as during acceleration, the control valve 76 can be fully opened. When less torque is required, the control valve 76 can be actively closed to different degrees based on the demand level. When very little torque is required to maintain the speed of the electrified vehicle 20, the control valve 76 can be fully closed to maximize efficiency. When the flow to the rotor 86 increases, the speed of the pump 72 can be increased, and when the flow to the rotor 86 decreases, the speed of the pump 72 can be reduced. A similar method can be applied to the parameters of speed and sump temperature, where the proportion of the control valve 76 opening is related to the magnitude of the parameter. Monitoring the parameters enables continuous active control during the operation of the electrified vehicle 20. As long as the propulsion system 26 is in operation, the method 200 can repeatedly return to step 202.

[0058] In this embodiment, the permanent magnet flux can be controlled via the flow of fluid 88 through the rotor. Although there may be a general goal to reduce motor temperature and therefore reduce rotor temperature, certain motor operating areas may actually benefit from higher rotor temperatures. For example, at relatively high torque demands, cooler permanent magnets will provide higher flux, which is beneficial to torque production per unit stator current, thereby facilitating motor torque production, while also reducing motor power consumption and copper losses at the rotor. At relatively low torque demands, and particularly at higher speeds (e.g., above base speed) where high magnetic flux from the permanent magnets results in higher back EMF and therefore higher field-weakening stator current components, warmer permanent magnets will provide lower flux, which reduces the back EMF and field-weakening stator current components, resulting in lower machine power consumption and reduced copper losses at the stator windings and reduced iron losses in the steel laminations. In the present embodiment, where flow control of fluid 88 through rotor 86 inversely affects flow of fluid through stator 84, flow through rotor 86 is reduced during medium and low torque demands to achieve increased permanent magnet temperature and reduced flux, resulting in increased flow through stator 84, reducing stator 84 temperature and advantageously reducing machine power consumption and reducing copper losses at the stator. Advantageously, since the drive cycle can include significant operation of the motor in the low to medium torque region, such selective fluid flow control can improve overall drive cycle performance efficiency and range.

[0059] Through the foregoing, propulsion system 26 with cooling system 68 is able to control flow to rotor 86 and improve efficiency through selective temperature control of rotor and permanent magnet flux. In addition, simultaneous inverse control of rotor cooling flow and stator cooling flow provides additional efficiency benefits not previously realized.

[0060] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to also include the plural forms, unless the context clearly indicates otherwise. It will be further understood that when used in this specification, the terms "include" and / or "comprise" specify the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.

[0061] All numerical values ​​herein are assumed to be modified by the term "about", whether explicitly stated or not. For purposes of this disclosure, ranges may be expressed as from "about" one particular value to "about" another particular value. The term "about" generally refers to a numerical range that one skilled in the art would consider equivalent to the numerical value, having the same function or result, or generally being reasonably within the manufacturing tolerance of the numerical value. Similarly, the numerical values ​​set forth herein are provided as non-limiting examples and may be nominal values, it being understood that actual values ​​may differ from the nominal values ​​depending on the environment, design and manufacturing tolerances, age, and other factors.

[0062] When an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element, or there can be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements. Therefore, unless explicitly described as "directly," when describing a relationship between a first element and a second element in the above disclosure, the relationship can be a direct relationship between the first element and the second element without other intervening elements, but can also be an indirect relationship between the first element and the second element with one or more intervening elements (either spatially or functionally) present.

[0063] One or more steps within the method may be performed in a different order (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure may be implemented in and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the permutation of one or more embodiments with respect to each other is still within the scope of the present disclosure.

[0064] Unless defined otherwise, 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.

[0065] Unless stated to the contrary herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0066] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A method for rotor flux control in a permanent magnet (PM) motor, comprising: Fluid flow through the rotor is controlled based on an operating point of the PM motor such that the rotor receives a reduced fluid flow when the operating point of the PM motor is below a predetermined threshold relative to the fluid flow when the operating point of the PM motor is above the predetermined threshold. 2 . The method for rotor flux control in a PM motor according to claim 1 , wherein the operating point of the PM motor comprises a PM motor torque, and the predetermined threshold comprises a torque threshold. 3 . The method for rotor flux control in a PM motor of claim 1 , wherein the operating point of the PM motor comprises a PM motor torque at a machine speed, and the predetermined threshold comprises a torque threshold at the machine speed.

4. The method for rotor flux control in a PM motor of claim 1 , wherein the operating point of the PM motor comprises a PM motor torque at a machine speed at a DC voltage, and the predetermined threshold comprises a torque threshold at the machine speed at the DC voltage.

5. The method for rotor flux control in a PM motor of claim 1 further comprising controlling fluid flow through a stator of the PM motor inversely relative to fluid flow received by the rotor such that when the rotor receives a decreased fluid flow, the stator receives an increased fluid flow. 6 . The method for rotor flux control in a PM electric machine of claim 1 , wherein controlling fluid flow through the rotor comprises controlling the fluid flow using a solenoid valve.

7. A method for rotor flux control in a PM motor according to claim 1, wherein the fluid flow through the rotor is controlled based on the operating point of the PM motor, so that the rotor receives a reduced fluid flow when the operating point of the PM motor is below the predetermined threshold relative to the fluid flow when the operating point of the PM motor is above the predetermined threshold, occurring above a predetermined PM motor speed. 8 . The method for rotor flux control in a PM electric machine according to claim 7 , wherein the predetermined PM electric machine speed comprises a base speed of the PM electric machine.

9. A propulsion system for an electrified vehicle, comprising: Permanent magnet (PM) motor; a gear unit connected to the PM motor; a cooling system for controllably circulating a fluid through passages in a rotor of the PM motor, the cooling system including a variable force solenoid valve that receives pressurized fluid and controls circulation of the pressurized fluid through the rotor in response to a control command; as well as A controller is provided for providing a control command for achieving a fluid flow through the rotor based on an operating point of the PM motor, such that the fluid flow through the rotor is reduced when the operating point of the PM motor is below a predetermined threshold value relative to the fluid flow through the rotor when the operating point of the PM motor is above the predetermined threshold value.

10. The propulsion system for an electrified vehicle of claim 9, wherein a cooling system for controllably circulating fluid through passages in a rotor of the PM motor diverts fluid that is not circulated through passages in the rotor of the PM motor to pass through a stator of the PM motor such that when the rotor receives a reduced fluid flow, the stator receives an increased fluid flow.

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