Multi-motor electric drive unit

Abstract

Electric drive unit, comprising: a stator assembly having a first set of stator windings and a second set of stator windings; a first set of rotors, each designed to: interact electromagnetically with the first set of stator windings; and to be rotationally coupled to a specific gear in a first summing gear set; a second set of rotors designed to: interact electromagnetically with the second set of stator windings; and to be rotationally coupled to a specific gear in a second summing gear set; and a first inverter electrically connected to the first set of stator windings and a second inverter electrically connected to the second set of stator windings; wherein the first inverter is configured to independently control the speeds of the first set of rotors, and the second inverter is configured to independently control the speeds of the second set of rotors.

Description

TECHNICAL FIELD

[0001] The present description relates generally to an electric drive unit having a plurality of electric motor sets driving summing gear sets. BACKGROUND AND OVERVIEW

[0002] Electric drives are being used in certain vehicles as the transportation sector moves toward powertrain electrification. Some electric drives utilize gear sets, such as planetary gearboxes, driven by a single, comparatively large traction motor. Other electric drives utilize two electric motors with a comparatively large diameter and short axial length. These electric drives can experience undesirable stator losses, for example, during traction. Furthermore, certain dual-motor electric axles have unused volume in the center of the motors, which compromises the compactness of the electric axle.

[0003] US 9,487,084 B2 by Petersen et al. shows an electric drive with multiple motors providing parallel drive for a Ravigneaux gear. The Ravigneaux gear includes sun gears coupled to planetary gears.

[0004] The inventors identified several problems with Petersen's multi-motor electric drive. Petersen's Ravigneaux gear set, for example, is complex and can be difficult to manufacture. Furthermore, Petersen remains silent about any type of system used to power the motors. Furthermore, the inventors recognized that other electric drive systems that use two motors and inverters have manufacturing and cost issues compared to electric drive systems that use only one motor and one inverter in the electric drive.

[0005] The inventors have recognized the aforementioned challenges and developed an electric drive unit to at least partially overcome the challenges. In one example, the electric drive unit includes a stator assembly including a first set of stator windings and a second set of stator windings, and a first set of rotors, each configured to electromagnetically interact with the stator assembly and to be rotationally coupled to a particular gear in a first summing gear set. The electric drive unit further includes a second set of rotors configured to electromagnetically interact with the second set of stator windings and to be rotationally coupled to a particular gear in a second summing gear set.The electric drive unit further includes a first inverter and a second inverter, both electrically coupled to the first set of stator windings and the second set of stator windings, respectively. In the electric drive unit, the first inverter and the second inverter are configured to independently control the speeds of the first set of rotors and the second set of rotors, respectively. In this way, multiple electric motors are used in the electric drive to reduce the individual input torque for the summing gear sets, thereby reducing component diameters and bearing sizes, which impacts component speed limitations, inertia, wear, and other forms of deterioration of the drive unit. This increases the longevity of the electric drive unit.In addition, by using several relatively small electrical machines as opposed to a single larger machine, manufacturing costs can be reduced through economies of scale.

[0006] In one example, the rotational axes of the first and second sets of rotors may be arranged in parallel. Furthermore, in such an example, the first and second sets of rotors may be arranged between the first and second drive wheels with respect to the rotational axes of the first and second drive wheels, which are arranged coaxially with each other. In this way, the electric drive unit achieves greater space efficiency, allowing the drive unit to be installed in a wider variety of vehicle platforms. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 shows an electric vehicle (EV) with a first example of an electric drive unit. Fig. 2A-2C are various cross-sectional views of the electric drive unit shown in Fig. 1 is shown. Fig. 3 shows a second example of an electric drive unit including a separation unit. Fig. 4 shows a third example of an electric drive unit with a cooling system comprising a pump motor and a coolant pump. Fig. 5A-5B are detailed side views of the electric drive unit shown in Fig. 4 is shown. Fig. 6 is an illustration of a method of operating an electric drive unit. Fig. Figure 7 is an example of the operating sequence of the electric drive unit at partial load. Fig. 8-10 are cross-sectional views of the electric drive unit shown in Fig. 4 is shown. Fig. 11 shows an example of an inverter assembly for an electric drive unit. DETAILED DESCRIPTION

[0007] Electric drive units and systems are described that achieve higher operating efficiency and better space utilization, particularly with regard to the width of the drive unit, by reducing stator iron losses. This reduction in stator iron losses can be particularly beneficial when the vehicle is coasting and in electric drive units that use permanent magnet motors, although the electric drive units described here can use a variety of electric motor types. These operating efficiency gains and the more compact design of the drive units are achieved by designing the electric drive units with electric drives for the opposing drive wheels. Both electric drives employ multiple traction motors that are directly rotationally coupled to specific gears, e.g., planetary gears, in summing gear sets.Reduction gears (e.g., final drive ratios) can be used to connect the summing gear sets to the drive wheels. In one example, the electric drive units can also include a cooling system with a pump motor and a coolant pump arranged circumferentially within the traction motors. In this way, the cooling system is integrated into the drive units in a space-saving manner. This increases the operational and space efficiency of the drive unit.

[0008] Fig. 1 shows an electric vehicle (EV) 100 with a powertrain 102 that includes an electric propulsion system 104 with an electric drive unit 106 (e.g., an electric axle). An electric axle is a powertrain in which both the traction motors and the transmission, and in some cases the inverters, are housed in an axle assembly so that the components are located together. The EV 100 may, in one example, be a pure electric vehicle (e.g., a battery electric vehicle (BEV)) or, in another example, a hybrid vehicle. Thus, in some examples, vehicles using the electric drive units described herein may also have an internal combustion engine (e.g., a gasoline engine, a compression ignition engine, combinations thereof, and the like).The electric drive units described here can be used in cars, trucks, ATVs, commercial vehicles, light vehicles, off-highway vehicles, mining vehicles and the like.

[0009] In the example shown, the electric drive unit 106 comprises independent drives for the drive wheels (which are shown in the Fig. 1 are the left and right drive wheels). The electric drive unit 106 includes the electric drives 108 and 110. In other words, the electric drive unit 106 includes motor and transmission assemblies for each of the drive wheels, which can be operated independently of one another.

[0010] A stator assembly 112 is provided in the electric drive unit 106. The stator assembly 112 can be included in both electric drives 108 and 110. The stator assembly 112 can include a laminated core 113 and multiple sets of stator windings that cause the rotation of a corresponding rotor through electromagnetic interaction. In particular, a first set of stator windings 114 is included in the stator assembly 112 and, in the example shown, is associated with the electric drive 108. The first group of stator windings 114 surrounds a rotor at the periphery. The electric drive unit 106 can conceptually also include a first set of rotors 116 associated with the first set of stator windings 114. A first set of end windings 118 can correspond to the first set of stator windings 114. The first set of stator windings 114 and the first set of rotors 116 are included in the electric drive 108.The first set of stator windings 114, the first set of rotors 116, and the first set of end windings 118 form a first set of electric motors 119 in the electric drive 108. Each of the laminations in the stators described herein contains end windings. Therefore, the end windings may be referred to as sets or groups of end windings. In a specific example, the first and second sets of rotors may each comprise three rotors, and the stator assembly may include end windings associated with each of these rotors. In such an example, the equivalent diameter of the individual motors may be 1 / 3 of the total diameter of the stator assembly. However, other drive units with fewer or greater numbers of rotors and associated stator windings are also possible.

[0011] The rotors of the first set of rotors 116 each include a shaft 120 and a rotor body 122. The traction motors described herein may take various forms. For example, the traction motors described herein may be, but are not limited to, multi-phase (e.g., three-, four-, six-phase, etc.) AC motors. Additionally, the electric motors described herein may be permanent magnet motors that include permanent magnets in the rotors. However, in other examples, a variety of motors may be used. Furthermore, in some cases, the electric motors described herein may be configured to operate in both a drive mode and a regenerative mode. In regenerative mode, the machine generates electrical energy. In other examples, the traction motors described herein may be induction motors, also known as asynchronous motors.However, in other examples, other types of traction motors may be used in the electric drive unit 106.

[0012] The rotors of the first set of rotors 116 are each coupled to a specific gear in a first summing gear set 124 associated with the electric drive 108. In the illustrated embodiment, the rotor shaft of the first set of rotors 116 is each coupled to a planetary gear 126 in the first summing gear set 124.

[0013] Although in the Fig. 1, only a single rotor and a single planetary gear are visible in the electric drive 108, it will be understood that the first summing gear set 124 includes additional planetary gears. For example, the first summing gear set 124 may include three planetary gears. In other examples, the first summing gear set 124 may include, for example, two planetary gears or more than three planetary gears.

[0014] The planetary gears 126 mesh with a sun gear 128. In addition, a countershaft 130 rotatably couples the sun gear 128 to a reduction gear 132 (e.g., a first final gear ratio). It is understood that the countershaft 130 and the reduction gear 132 belong to the electric drive 108. The reduction gear 132 includes a gear 134 that is fixedly coupled to and rotates with the countershaft 130, and a gear 136 that meshes with the gear 134. The gear 136, in turn, is rotationally coupled (e.g., directly rotationally coupled) to a drive gear 138 via a drive shaft 140.

[0015] The electric drive 110 includes a second set of electric motors 142 having a second set of rotors 144, a second set of stator windings 146, and a second set of end windings 149. The second set of stator windings 146 includes individual stacks surrounding and electromagnetically cooperating with each of the rotors in the second set of rotors 144. The second set of stator windings 146 is contained within the stator assembly 112. Furthermore, each of the rotors in the second set of rotors 144 includes a rotor shaft 145 and a rotor body 147.

[0016] The second set of rotors 144 is each rotatably coupled to a planetary gear 148 in a second summing gear set 150. Furthermore, the planetary gears 148 mesh with a sun gear 152, which is rotationally coupled to a countershaft 154. A reduction gear 156 (e.g., a final drive) is also included in the electric drive unit 110 of the electric drive unit 106. The reduction gear 156 includes a gear 158 that is fixedly coupled to and rotates with the countershaft 154, and a gear 160 that meshes with the gear 158. The gear 160, in turn, is rotationally coupled (e.g., directly rotationally coupled) to a drive gear 162 via a shaft 164.

[0017] In the illustrated example, a first inverter 166 and a second inverter 168 are electrically coupled to the first set of electric motors 119 and the second set of electric motors 142. Inverters 166 and 168 convert direct current to alternating current and vice versa. However, in alternative examples, one inverter may be used to power both electric machines, or the inverters may be omitted if DC electric machines are used in the powertrain.

[0018] Inverters 166 and 168 may receive electrical energy from one or more energy storage devices 170 (e.g., traction batteries, capacitors, fuel cells, combinations thereof, and the like). Arrows 172 indicate the electrical energy transfer between inverters 166 and 168 and the energy storage device(s) 170, which may occur during various operating modes of the system. Of course, electrical energy is also transferred from the inverters to the motors of the electric drive. In one example, inverters 166 and 168 may each be electrically coupled to one or more energy storage devices 170. In other examples, however, inverters 166 and 168 may also be electrically coupled to different energy storage devices. The other inverters described herein may be electrically coupled to similar energy storage devices.For the sake of clarity, a redundant description of the energy storage systems is therefore omitted.

[0019] As in Fig. 1, the EV 100 may also include a control system 190 having a controller 192. The controller 192 may include a microcomputer with components such as a processor 194 (e.g., a microprocessor unit), input / output ports, an electronic storage medium 196 for executable programs and calibration values, e.g., a read-only memory chip, read-only memory, diagnostic memory, a data bus, and the like. The storage medium may be programmed with computer-readable data representing instructions executable by a processor to perform the methods, control techniques, etc., described herein, as well as other variations that are expected but not explicitly listed.Thus, instructions may be stored in the electronic storage medium 196 which, when executed by the processor 194, cause the controller 192 to perform the various method steps described herein.

[0020] The controller 192 may receive various signals from sensors 197 coupled to various areas of the vehicle 100, and in particular, the electric drive unit 106. The sensors 197 may include, for example, one or more engine speed sensors in the form of resolvers, which will be discussed in more detail below, one or more electric motor load sensors, shaft / transmission speed sensors, a pedal position sensor for detecting the depression of a driver-operated pedal (e.g., an accelerator pedal and / or a brake pedal), speed sensors at the vehicle wheels, etc. An input device 198 (e.g., accelerator pedal, brake pedal, gear selector, combinations thereof, and the like) may also provide input signals indicative of the driver's intent for vehicle control.

[0021] After receiving the signals from the various sensors 197 from Fig. 1, the controller 192 processes the received signals and deploys various vehicle component actuators 199 to adjust the components based on the received signals and the instructions stored in the memory of the controller 192. For example, the controller 192 may receive an accelerator pedal signal indicating a driver request for an adjustment in vehicle acceleration. In response, the controller 192 may command operation of the inverters 166 and 168, which are electrically coupled to the electric motor sets 119 and 142, to increase the power delivered by the motors to the summing gear sets 124 and 150. The other controllable components in the vehicle may function in a similar manner, e.g., with respect to sensor signals, control commands, and actuator adjustment. Furthermore, the control system 190 may be employed in any of the electric drive systems and assemblies described herein.

[0022] A first resolver 180, coupled to the countershaft 130, may be used in the electric drive 108 to determine the speed of the first set of electric motors 119. Similarly, a second resolver 182, coupled to the countershaft 154, may be used in the electric drive 110 to determine the speed of the second set of electric motors 142.

[0023] An axis system is in Fig. 1 and in the Fig. 2A-5B and 8-11 for reference. In one example, the z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., a horizontal axis), and the y-axis may be a longitudinal axis. In other examples, the axes may also have other orientations. The rotational axes 184 of the electric motors of the first and second sets of electric motors 119 and 142 are shown in Fig. 1. In addition, Fig. 1 shows the rotational axes 186 of the countershafts 130 and 154. Furthermore, Fig. 1 the rotational axes 188 of the drive wheels 138 and 162 are shown. Fig. 1 and Fig. The cross sections shown in Figures 3-4 lie in the zx-plane and run through the rotation axes mentioned above.

[0024] Due to the smaller size of the rotors compared to electric drives with a smaller number of motors, the electric motors of the electric drive unit 106 can be operated at a speed > 25,000 revolutions per minute (rpm) if desired. Furthermore, the gear ratios of the left and right electric drives 108 and 110 can be 1:16 in a specific example. In such an example, the gear ratio of the summing gear set and the subsequent reduction gear for the left and right electric drives can each be 4:1. In this way, the electric drive unit 106 is capable of achieving the target speed of the drive wheels. For example, the speeds of the drive wheels can be approximately 1,800 rpm under certain conditions. However, the electric drive unit can also have other suitable gear ratios for the left and right drives in alternative examples.The gear ratio can be selected based on the type of electric motors used in the drive unit, the expected operating speed of the motors, the efficiency curves of the motors, the powertrain performance objectives for the end use, etc.

[0025] In another example, the electric drive unit 106 may also include a cooling system configured to enable direct cooling of the lamination and cooling of the dip winding. Furthermore, a baffle plate could be developed to provide hydraulic oil guidance. An example of a drive unit cooling system is shown in Fig. 4 and in the Fig. 8-10 and is explained in more detail here.

[0026] Fig. Figure 2A shows a cross-sectional view of the electric drive unit 106 with the stator assembly 112 in the zy plane. The first set of electric motors 119 with the first set of rotors 116 and the first set of stator windings 114 is depicted. Similarly, the second set of electric motors 142 with the second set of rotors 144 and the second set of stator windings 146 is depicted.

[0027] The first set of electric motors 119 and the second set of electric motors 142 are arranged circumferentially. The motors of the first set of electric motors 119 may be spaced 120° apart from a central axis 200. Similarly, the motors of the second set of electric motors 142 may be offset 120° from the central axis 200. Furthermore, the motors of the first group of electric motors 119 are arranged between the motors of the second group of electric motors 142. Thus, adjacent motors in the first and second sets of electric motors may be spaced 60° apart from the central axis. However, in other embodiments, the motors may have another suitable arrangement.

[0028] The planet gears 126 and the sun gear 128 in the first summing gear set 124 are in Fig. 2A. The countershaft 130 is in Fig. 2A together with the reduction gear 132, which includes the gears 134 and 136.

[0029] In the illustrated example, the outer diameter 250 of the stator assembly 112 corresponds to the outer diameter 252 of the gear 136. In this way, a desired form factor of the electric drive unit can be achieved. However, in other examples, the stator assembly 112 and the gear 136 may also have different size ratios.

[0030] Fig. 2B shows the electric drive unit 106 with the Fig. 2A, which has been omitted to show the underlying components. For clarity, Fig. 2B shows the first set of rotors 116, wherein each of the rotors, and in particular the rotor shafts 120, are shown with a pitch of 120° in the illustrated example. However, in alternative examples, a different number of rotors and thus motors with a different pitch may be used. In another example, six motors may be used in each of the electric drive units.

[0031] The second set of electric motors 142 is in Fig. 2A. The first set of electric motors 119 and the second set of electric motors 142 are arranged around a circle 260 in the example shown so that the motors can be compactly housed within the drive unit and provide pinion inputs to the summing gear sets for the left and right electric drives. The circular arrangement of the electric motors for the left and right drive units allows the compactness of the electric drive unit to be increased and, in particular, the lateral width of the drive unit to be reduced, so that the drive unit can be installed in a wider variety of vehicle platforms. The use of the planetary gears as inputs to the summing gear sets enables this space-saving motor arrangement and allows the summing gear sets to achieve a desired gear ratio.

[0032] Fig. Figure 2C shows a cross-sectional view of the electric drive unit 106 on the opposite side (relative to the x-axis) to show the rotor shafts 145 of the second set of electric motors 142 connected to the planetary gears 148 in the second summing gear set 150. Also shown is the sun gear 152 in the second summing gear set 150. As shown in Fig. 1, the sun gear 152 is fixedly coupled to the countershaft 154, to which the gear 158 is fixedly coupled. Fig. 1 shown gearbox 160 is in Fig. 2C omitted to show the underlying components of the electric drive unit.

[0033] Fig. 3 shows another example of an electric drive unit 300. The electric drive unit 300 again includes a first electric drive 302 and a second electric drive 304, which enable power to be delivered independently to laterally opposite drive wheels by a first set of electric motors 306 and a second set of electric motors 308. Both the first and second sets of electric motors 306 and 308 again include rotors 310 circumferentially surrounded by stators 312 containing laminations 314 and end windings 316, similar to the previously described electric motors. Redundant description is omitted for clarity.

[0034] The first set of electric motors 306 is coupled to a compound summing gear set 318 (e.g., a stepped summing gear set). The summing gear set 318 includes a first sun gear 320, a second sun gear 322, a first set of planet gears 324 that mesh with the first sun gear 320, and a second set of planet gears 326 that mesh with the second sun gear 322. The two sun gears 320 and 322 are rotationally coupled to a countershaft 328.

[0035] A portion of the motors 330 in the first set of electric motors 306 are rotationally coupled to planetary gears 324 that mesh with the first sun gear 320 in the summing gear set 318. Another portion of the motors 332 in the first set of electric motors 306 are rotationally coupled to planetary gears 326 that mesh with the second sun gear 322 in the summing gear set 318. Although only the rotor shafts 334 of the portions of the motors 332 in the first group of electric motors 306 are depicted, it is assumed that the motors include stator windings similar to those of the other motors described herein. Both the first sun gear 320 and the second sun gear 322 are arranged coaxially with the countershaft 328. In particular, the second sun gear 322 can be fixedly coupled to the countershaft 328 and the first sun gear 320 can be selectively coupled to the countershaft 328 via a separating clutch 336.If the first group of electric motors 306 includes three motors, the group of motors 330 may include two motors and the group of motors 332 may include one motor, or vice versa. For example, the dual countershaft summing gear sets may have a V-configuration, in which the first sun gear 320 and the second sun gear 322 may be helical gears and designed symmetrically. This allows the axial force on the intermediate shaft bearing to be reduced.

[0036] Similarly, a portion of the motors 338 in the second set of electric motors 308 are rotationally coupled to planetary gears 340 that mesh with a first sun gear 342 in a compound summing gear set 344 (e.g., a stepped summing gear set). Another portion of the motors 346 in the second set of electric motors 308 are rotationally coupled to planetary gears 348 that mesh with a second sun gear 350 in the summing gear set 344. Although only the rotor shafts 352 of the portions of the motors 346 in the second set of electric motors 308 are depicted, the motors will include stator windings similar to those of the other motors described herein. If the second group of electric motors 308 includes three motors, the group of motors 338 may include two motors and the group of motors 346 may include one motor, or vice versa. Furthermore, each of the left and right electric drives 304 and 306 may have a corresponding number of motors.The other electric drive unit can also have a corresponding number of motors in both electric drives.

[0037] Both the first sun gear 342 and the second sun gear 350 are arranged coaxially with a countershaft 354. In particular, the second sun gear 350 can be fixedly coupled to the countershaft 354, and the first sun gear 342 can be selectively coupled to the countershaft via a disconnect clutch 356. The disconnect clutches 336 and 356 can be friction clutches or dog clutches in various examples.

[0038] In the example shown, a first inverter 358 and a second inverter 360 are electrically coupled to the first set of electric motors 306 and the second set of electric motors 308. The inverters 358, 360 convert direct current to alternating current and vice versa. The inverters 358 and 360 can be equipped with switches that can be used to deactivate the different motor groups independently of one another. For example, via an electromagnetic actuator or electrical semiconductor switches or a relay system.

[0039] Fig. 11 shows an example of an inverter assembly 1100 with a first inverter 1101 and a second inverter 1102, which may be included in any of the electric drive units described herein. Each of the inverters 1101 and 1102 includes a plurality of multi-phase (e.g., three-phase) power modules 1104 having multi-phase electrical interfaces 1106. Furthermore, each of the power modules 1104 may be electrically connected to a DC link capacitor 1108 shared between the first and second inverters via DC electrical connections 1110. Each power module controls the phases of a single motor. In the Fig. In the embodiment shown in Figure 11, the separate power modules can be used to synchronize each motor with the wheel speed, if desired.

[0040] In alternative examples, one inverter may be used to power both electric machines. If a single inverter is used in the electric drive unit 300, a synchronizing device may be used in each of the Fig. 3. Specifically, each synchronizing device may be configured to lock the rotation of the deactivated rotor in the corresponding drive unit to the operating rotors.

[0041] The electric drive unit 300 in turn includes reduction gears 362 and 364 (e.g., final gear ratios) for each of the electric drives 302 and 304, which enable the summing gear sets 318 and 344 to be rotationally coupled to the drive gears 366 and 368, respectively.

[0042] Each of the gear reductions 362 and 364 includes a gear 370 that is fixedly coupled to the associated countershaft so as to rotate therewith, and a gear 372 that meshes with the gear 370 and is rotationally coupled (e.g., directly rotationally coupled) to the corresponding drive gear.

[0043] Fig. 4 shows another example of an electric drive unit 400. The electric drive unit 400 includes a first set of electric motors 402, a first summing gear set 404, and a reduction gear 406 in a first electric drive 408. The electric drive unit 400 further includes a second set of electric motors 410, a second summing gear set 412, and a reduction gear 414 in a second electric drive 416. The structure and function of the electric motor and the summing gear set in the Fig. The electric drive unit 400 shown in Figure 4 is similar to the structure and function of the electric motor and the summing gear set in the Fig. 1. A redundant description of the features of the electric motor and the summing gear set is omitted for the sake of brevity.

[0044] A stator assembly 417 is part of the electric drive unit 400. The stator assembly 417 may include a laminated core 419 and multiple sets of stator windings 423, similar to the other drive unit embodiments described herein.

[0045] The electric drive unit 400 includes a cooling system 418 with a pump motor 420 positioned radially inward of the first group of electric motors 402 and the second group of electric motors 410, which are arranged in a circle in the illustrated example. The pump motor 420 includes stator windings 421 and a rotor 425, which may be constructed similarly to the other electric motors described herein. The stator windings 421 may be contained in the stator assembly 417. In this way, the pump motor is integrated into the drive unit in a space-saving manner.

[0046] The pump motor 420 is rotatably coupled to a coolant pump 422 (e.g., an oil pump), which may be arranged coaxially with the electric pump. The coolant pump 422 is also arranged radially within the first and second motor sets 402 and 410. This increases the compactness of the electric drive unit while simultaneously enabling cooling of the drive unit.

[0047] The coolant pump 422 has an outlet 424 with radial channels 427 that direct the coolant (e.g., oil) to an oil distribution plate 429. The stator lamination stack may be split into two sub-packets. In such an example, the oil distribution plate may be disposed between the two sub-stacks. The arrows 431 generally show the direction of coolant flow through the stator windings and into the housings 426 around the end windings 428. In particular, one or more axial coolant channels may extend through each set of stator windings. In one example, the coolant is directed through the stator windings in opposite axial directions. However, in other examples, the coolant may be directed through the stator windings in only one axial direction. Although the flow of coolants is illustrated with arrows, in practice the flow of coolants may be more complex.The housings 426 can be configured to cool the end windings by immersion. This increases the efficiency of the electric drive unit. Furthermore, in the illustrated embodiment, the openings 430 in each of the housings 426 are in fluid communication with an inlet 432 of the coolant pump. Specifically, the inlet 432 can be in fluid communication with a sump 433 that receives coolant from the housings 426.

[0048] The cooling system 418 is further configured to direct coolant to housings 426 surrounding the end windings 428 of each of the stators in both the first set of electric motors 402 and the second set of electric motors 410. In one example, oil deflectors may be used in the cooling system 418 to collect and direct oil to the bearings and / or gears. Generally, the housing 426 may be configured to capture and direct oil to the bearings and / or gears.

[0049] The section plane AA' indicates the location of the Fig. 8, the section plane BB' is the location of the Fig. 9 and the section plane CC' the location of the Fig. 10 shown cross-sectional view.

[0050] In the Fig. In one example of the electric drive unit 400 shown in Figure 4, the pump motor 420 can be conceptually integrated into the unit as a seventh motor. The electric drive unit 400 can have a shorter stack length compared to drive units with a single motor due to the lower power of each motor. This remaining stack length can be used to integrate the coolant pump 422 into the drive unit in a space-saving manner.

[0051] Fig. 8-10 show cross-sectional views of the electric drive unit 400 with the stator assembly 417 and the cooling system 418. The pump outlet 424 and the radial cooling channels 427 are shown for clarity. The radial cooling channels are in fluid communication (e.g., direct fluid communication) with the axial cooling channels 900 adjacent to the end windings in the various sets of end windings 423. In this way, the end windings can be effectively cooled, increasing the efficiency of the drive unit.

[0052] As in Fig. 8-10, the stator assembly 417 further includes sets of stator windings 423, which include a plurality of end windings 902 associated with each rotor in the drive unit. In the example shown, the drive unit includes six rotors and the associated end windings, as well as a seventh set of end windings (in Fig. 10) and rotor for the pump motor in the cooling system. The stator windings 421 of the pump motor are in Fig. 10. However, other drive units with a larger or smaller number of motors were also considered.

[0053] Fig. 5A and Fig. 5B show detailed side views (with respect to the x-axis) with the planetary gear ratios and final gear ratios omitted to show the underlying components. Fig. Figure 5A shows a detailed side view of the electric drive unit 400, and in particular, the first set of electric motors 402, the second set of electric motors 410, and the pump motor 420. As shown, the first and second sets of electric motors 402 and 410 are again arranged in a circle 500 in the example shown to increase the space efficiency of the drive unit. The pump motor 420 is offset radially inward from the motors to further increase the space requirement of the drive unit.

[0054] Fig. 5B is another detailed side view of the first set of electric motors 402, the second set of electric motors 410, and the coolant pump 422. The first and second sets of electric motors 402 and 410 are also arranged in a circle, and the coolant pump 422 is positioned radially inward of the motors to further increase the compactness of the drive unit.

[0055] Fig. 6 shows a method 700 for operating an electric drive unit. The method 700 can be implemented by the Fig. 3 or another suitable electric drive unit including disconnect clutches configured to deactivate a portion of the motors in the left and right electric drives during selected operating conditions, such as partial load conditions.

[0056] At 702, the control method includes determining the operating conditions. The operating conditions may include the load on the electric drive unit, the speeds of the electric motor, the speed of the drive wheel, the position of the accelerator pedal, the state of charge of the battery, and the like. These operating conditions may be determined through sensor inputs, modeling, combinations thereof, and the like.

[0057] At 704, the method includes determining that the electric drive unit is operating under a partial load condition. This determination may be compared to a measured or calculated load of the drive unit, which may be determined via load sensors on one or more of the electric motors and / or other inputs such as inverter power, wheel speed, and the like.

[0058] If it is determined that the electric drive unit is not operating at partial load (NO at 704), the method proceeds to 706, where the method includes maintaining engagement of the disconnect clutches in the first electric drive and the second electric drive. For example, an electromechanical, hydraulic, or pneumatic actuator may maintain engagement of the disconnect clutches so that power is transferred across the clutches.

[0059] If it is determined that the electric drive unit is operating at partial load (YES at 704), the method proceeds to 708, where the method includes disengaging a disconnect clutch in each of the first and second electric drives. For example, the clutch actuators may be actuated to disengage the disconnect clutches, interrupting power transmission through the clutches. Next, at 710, the method interrupts power from the inverters to the de-energized electric motors. For example, switches that enable power transmission to the de-energized motors may be opened to interrupt power supply from the inverters to the motors. Method 700 enables the operating efficiency of the electric drive unit to be increased when the drive unit is operating at partial load.

[0060] Fig. Figure 7 shows a timing diagram 800 for an application scenario of an electric drive unit. Specifically, the control strategy shown in the timing diagram 800 can be implemented by the Fig. 3 or another suitable electric drive unit that includes disconnect clutches configured to deactivate a portion of the motors in the left and right electric drives during selected operating conditions, such as partial load conditions. In each graph, time is indicated on the abscissa and increases from left to right. The ordinate of graph 802 indicates the load on the electric drive unit. Although no specific values ​​are indicated in the graph, the load increases from bottom to top. The ordinates for graphs 804, 806, 808, and 810 indicate the operating states (i.e., "operational" and "deactivated") of the first electric motor group, the second electric motor group, the third electric motor group, and the fourth electric motor group, respectively. For clarity, when the Fig. 3 shown electric drive unit 300 which in Fig. 7, the first electric motor group corresponds to the group of motors 330 coupled to the planetary gears 324, the second electric motor group corresponds to the group of motors 332 coupled to the planetary gears 326, the third electric motor group corresponds to the group of motors 338 coupled to the planetary gears 340, and the fourth electric motor group corresponds to the group of motors 346 coupled to the planetary gears 348.

[0061] As in Fig. As shown in Figure 7, at time t0, all motor groups are operating. At t1, the load of the electric drive unit falls below a threshold 850, indicating a partial load condition. When the load of the drive unit falls below the threshold, the first electric motor group and the third electric motor group are shut down. Shutting down the electric motor groups involves disengaging the disconnect clutches associated with the motor groups and interrupting power transmission from the inverter to the motor groups. Interrupting the electrical power transmission may involve energizing inverters corresponding to the second and fourth electric motor groups. If the electric drive unit includes an inverter supplying all motors, as previously mentioned, synchronizers may be switched on in each of the left and right electric drives.

[0062] The gearbox and motor sizes are in Fig. 1-5B is drawn approximately to scale, and the electric drive unit in Fig. 8-10 are drawn approximately to scale. However, in other embodiments, the components may have different relative dimensions.

[0063] Fig.1-5B and 8-11 show example configurations with relative positioning of the various components. When these elements are in direct contact with each other or are directly coupled, they may be referred to as being in direct contact or directly coupled, respectively, at least in one example. Similarly, elements shown side by side or adjacent to each other may be adjacent to each other or adjacent to each other, at least in one example. For example, components that are in surface-to-surface contact with each other may be referred to as being in surface-to-surface contact. As another example, in at least one instance, elements that are separated from each other with only a space between them and that do not have any other components may be referred to as such.In yet another example, elements depicted above / below, on opposite sides, or to the left / right of each other may be referred to as such, relative to each other. Further, in at least one example, as depicted in the figures, a topmost element or point of an element may be referred to as a "top" of the component, and a bottommost element or point of the element may be referred to as a "bottom" of the component. As used herein, the terms top / bottom, upper / lower, above / below may refer to a vertical axis of the figures and may be used to describe the positioning of elements of the figures relative to each other. Thus, in one example, elements displayed above other elements are arranged vertically above the other elements.As another example, the shapes of the elements depicted in the figures may be referred to as such (e.g., circular, straight, flat, curved, rounded, beveled, angled, and the like). Furthermore, in one example, elements that are coaxial with each other may be referred to as such. Further, in at least one example, the depicted elements that intersect each other may be referred to as intersecting elements or as intersecting elements. Furthermore, an element depicted inside another element or outside another element may be referred to as such. In other examples, elements that are offset from each other may also be referred to as such.

[0064] The invention is further described in the following paragraphs. In one aspect, an electric drive unit is provided comprising: a stator assembly having a first set of stator windings and a second set of stator windings; a first set of rotors, each configured to: electromagnetically engage the first set of stator windings; and rotatably couple to a particular gear in a first summing gear set; a second set of rotors, each configured to: electromagnetically engage the second set of stator windings; and rotatably couple to a particular gear in a second summing gear set; and a first inverter and a second inverter electrically connected to the first set of stator windings and a second set of stator windings, respectively.the second set of stator windings; wherein the first inverter and the second inverter are configured to independently control the speeds of the first set of rotors and the second set of rotors, respectively. In one example, the axes of rotation of the first and second sets of rotors may be arranged in parallel. In another example, the first and second sets of rotors may be arranged between the first and second drive gears with respect to the axes of rotation of the first and second drive gears, which are arranged coaxially with each other. In one example, the particular gears in the first and second summing gear sets may be a first set of planetary gears and a second set of planetary gears, respectively, where the first and second sets of planetary gears may be the only planetary gears in the first and second summing gear sets, respectively.In another example, the motors of the first and second motor sets are higher-speed motors designed to operate at greater than 25,000 revolutions per minute (rpm). In one example, the electric drive unit may further include a first resolver positioned on a first countershaft in the first summing gear set and a second resolver positioned on a second countershaft in the second summing gear set, wherein the first resolver and the second resolver generate data indicative of a speed of the first set of rotors and a speed of the second set of rotors, respectively.In another example, the electric drive unit may further include a cooling system configured to direct coolant through a first set of laminations, a second set of laminations, end windings associated with the first set of laminations, and end windings associated with the second set of laminations included in the stator assembly. In another example, the electric drive unit may further include a pump motor rotatably coupled to a coolant pump, wherein the pump motor and the coolant pump are integrated into the first set of laminations and the second set of laminations. In one example, the coolant may also be oil. In one example, the first lamination and the second lamination may be separated by an oil distribution plate. In another example, a baffle may be used to distribute the coolant within the stator assembly.In another example, the first summing gear set may be rotationally coupled to a first drive gear via a first final gear ratio; and the second summing gear set may be rotationally coupled to a second drive gear via a second final gear ratio.

[0065] In another aspect, a method of operating an electric axle is provided, comprising operating a first inverter to effect mechanical power transfer from a first set of rotors to a first summing gear set; and operating a second inverter to effect mechanical power transfer from a second set of rotors to a second summing gear set; wherein each of the rotors in the first and second sets of rotors is configured to electromagnetically cooperate with a stator assembly including a first set of stator windings and a second set of stator windings circumferentially surrounding the first set of rotors and the second set of rotors, respectively; wherein the first summing gear set is rotationally coupled to a first drive gear; and wherein the second summing gear set is rotationally coupled to a second drive gear.In one example, the first inverter and the second inverter may be operated independently of each other. In another example, the first inverter may be operated based on data generated by a first resolver located on a first countershaft in the first summing gear set; and the second inverter may be operated based on data generated by a second resolver located on a second countershaft in the second summing gear set. The method may further include, in one example, operating a pump motor rotationally coupled to a coolant pump to drive coolant flow in a cooling system configured to circulate coolant through the stator assembly.

[0066] In another aspect, an electrical axis is provided that includes a stator assembly including a first set of stator laminations and a second set of stator laminations; a first set of rotors configured to electromagnetically cooperate with the first set of stator laminations; and a second set of rotors configured to electromagnetically cooperate with the second set of stator laminations; a first inverter electrically coupled in parallel with the first set of stator laminations; and a second inverter electrically coupled in parallel with the second set of stator laminations; wherein the axes of rotation of the first and second sets of rotors are circumferentially arranged in parallel.In one example, the electric axle may further include an oil cooling system configured to direct oil through a first set of laminations, a second set of laminations, end windings associated with the first set of laminations, and end windings associated with the second set of laminations included in the stator assembly. In another example, the electric axle may further include a pump motor rotationally coupled to an oil pump, the pump motor and oil pump circumferentially disposed within the first and second sets of electric motors arranged circumferentially. In another example, the first summing gear set may include a sun gear rotationally coupled to a first drive gear via a first final gear ratio; and the second summing gear set may include a sun gear rotationally coupled to a second drive gear via a second final gear ratio.In another example, the first and second summing gear sets are simple summing gear sets.

[0067] In another aspect, an electric drive unit is provided that includes a stator assembly including a first set of stator windings and a second set of stator windings; a first set of rotors, in which each rotor is configured to: electromagnetically interact with the first set of stator windings; and is rotationally coupled to a particular gear in a first summing gear set; a second set of rotors, in which each rotor is configured to: electromagnetically interact with the second set of stator windings; and be rotationally coupled to a particular gear in a second summing gear set; a first disconnect clutch configured to rotationally disconnect a first rotor in the first set of rotors from the first summing gear set; and a second disconnect clutch configured toto rotationally disconnect a first rotor in the second set of rotors from the second summing gear set. In one example, the first and second summing gear sets may be compound summing gear sets. In another example, the compound summing gear sets may be stepped summing gear sets. In one example, the electric drive unit may further include a controller having instructions stored in memory that, when executed, cause the controller to disengage the first disconnect clutch and the second disconnect clutch during a partial load condition. In another example, the axes of rotation of the first set of rotors and the second set of rotors may be circumferentially arranged. In another example, the electric drive unit may further include a first synchronizer configured toto selectively lock the rotational position of the first rotor in the first group of rotors when the first disconnect clutch is disengaged; and a second synchronizer configured to selectively lock the rotational position of the first rotor in the second group of rotors when the second disconnect clutch is disengaged. In another example, the electric drive unit may further include a cooling system configured to direct coolant through a first set of laminations, a second set of laminations, end windings associated with the first set of laminations, and end windings associated with the second set of laminations included in the stator assembly. In another example, the electric drive unit may further include a first inverter and a second inverter, each electrically coupled to the stator assembly. In another example, the first inverter may include switches,configured to independently electrically de-energize a lamination stack corresponding to the first rotor in the first group of rotors; and the second inverter may include switches configured to independently electrically de-energize a lamination stack corresponding to the first rotor in the second group of rotors. Further, in one example, the first summing gear set and the second summing gear set may each have a V-arrangement.

[0068] In another aspect, a method of operating an electric drive unit is provided, comprising actuating a first disconnect clutch to selectively rotationally disconnect a rotor in a first set of rotors from a first summing gear set; and actuating a second disconnect clutch to selectively rotationally disconnect a rotor in a second set of rotors from a second summing gear set; the electric drive unit comprising: a stator assembly; wherein the first set of rotors is each configured to: electromagnetically cooperate with the stator assembly; and rotationally couple to a particular gear in a first summing gear set; and the second set of rotors is configured to: electromagnetically cooperate with the stator assembly; and rotationally couple to a particular gear in a second summing gear set.In one example, the method may further comprise operating a first inverter to interrupt the mechanical power transmission from the one rotor in the first set of rotors to the first summing gear set; and operating a second inverter to interrupt the mechanical power transmission from the one rotor in the second set of rotors to the second summing gear set.In another example, the method may further include operating a first synchronizer to lock a rotational position of the one rotor in the first group of rotors relative to the other rotors in the first group of rotors when the first disconnect clutch is disengaged; and operating a second synchronizer to lock a rotational position of a rotor in the second group of rotors relative to the other rotors in the second group of rotors when the second disconnect clutch is disengaged.In another example, operation of the first inverter may include operation of a first set of switches associated with stator windings that electromagnetically interact with the inactive rotor in the first set of rotors, and operation of the second inverter may include operation of a second set of switches associated with stator windings that electromagnetically interact with the inactive rotor in the second set of rotors. In another example, the method may further include providing electrical power to a first set of stator windings and a second set of stator windings by the first inverter and the second inverter, respectively, wherein the first set of laminations corresponds to active rotors in the first set of rotors and the second set of stator windings corresponds to active rotors in the second set of rotors.

[0069] In another aspect, an electric axle is provided that includes a first set of rotors, each rotor configured to: electromagnetically interact with a first set of stator windings; and rotationally couple to a planetary gear in a first summing gear set; a second set of rotors, each rotor configured to: electromagnetically interact with a second set of stator windings; and rotationally couple to a separate gear in a second summing gear set; a first disconnect clutch configured to rotationally disconnect a first rotor in the first set of rotors from the first summing gear set; and a second disconnect clutch configured to rotationally disconnect a first rotor in the second set of rotors from the second summing gear set.In another example, the electric axle may further include a first inverter including switches configured to independently electrically deactivate a stator winding in the first set of stator windings; and a second inverter including switches configured to independently electrically deactivate a stator winding in the second set of stator windings. In another example, the electric axle may further include a first synchronizer configured to selectively lock the rotational position of the first rotor in the first set of rotors when the first disconnect clutch is disengaged; and a second synchronizer configured to selectively lock the rotational position of the first rotor in the second set of rotors when the second disconnect clutch is disengaged.Further, in one example, the first disconnect clutch may be configured to disconnect a first sun gear in the first summing gear set, and the second disconnect clutch may be configured to disconnect a second sun gear in the second summing gear set. In another example, the first summing gear set may include a third sun gear and the second summing gear set may include a fourth sun gear.

[0070] The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by an electric drive unit and / or a system including the controller in combination with the various sensors and actuators. Furthermore, portions of the methods may be physical actions performed in the real world to change the state of a device. The specific routines described herein may represent one or more arbitrary processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various illustrated acts, operations, and / or functions may be performed in parallel in the order presented or, in some cases, omitted.Likewise, the order of processing is not required to achieve the features and advantages of the examples described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the strategy used. Further, the described actions, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer-readable storage medium in the control system, wherein the described actions are carried out by execution of the instructions in a system including the various hardware components in combination with the electronic controller. One or more of the method steps described herein may also be omitted if desired.

[0071] Although various embodiments have been described above, these are intended as examples and not as restrictions or limitations. It should be understood that the configurations and operations disclosed herein are exemplary in nature, and that these specific examples should not be considered limiting, as numerous variations are possible. For example, the technology described above may be applied to powertrains that include various types of power sources, including various types of electric machines, internal combustion engines, and / or transmissions.The technology may be used as a standalone system or in combination with other powertrain systems, including, but not limited to, machines and drive systems for various types of electric axles, HEVs, BEVs, agriculture, marine, motorcycles, recreational vehicles, and on- and off-road vehicles, to name a few examples. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or properties disclosed herein. Those skilled in the art will appreciate that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter.

[0072] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be construed as including the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope than the original claims, are also to be considered included within the subject matter of the present disclosure.

[0073] The term “approximately” means plus or minus one percent of the range unless otherwise specified. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 9,487,084 B2

[0003]

Claims

[1] Electric drive unit, comprising: a stator assembly having a first set of stator windings and a second set of stator windings; a first set of rotors, each designed to: interact electromagnetically with the first set of stator windings; and to be rotationally coupled to a specific gear in a first summing gear set; a second set of rotors designed to: interact electromagnetically with the second set of stator windings; and to be rotationally coupled to a specific gear in a second summing gear set; and a first inverter electrically connected to the first set of stator windings and a second inverter electrically connected to the second set of stator windings; wherein the first inverter is configured to independently control the speeds of the first set of rotors, and the second inverter is configured to independently control the speeds of the second set of rotors. [2] Electric drive unit according to claim 1, wherein the axes of rotation of the first and second sets of rotors are arranged in parallel. [3] An electric drive unit according to any one of the preceding claims, wherein the first set of rotors and the second set of rotors are arranged between a first drive wheel and a second drive wheel with respect to the axes of rotation of the first and second drive wheels, which are arranged coaxially with each other. [4] An electric drive unit according to any preceding claim, wherein the particular gears in the first summing gear sets are a first set of planetary gears and in the second summing gear sets are a second set of planetary gears, and wherein the first set of planetary gears are the only planetary gears in the first summing gear sets and the second set of planetary gears are the only planetary gears in the second summing gear sets. [5] An electric drive unit according to any preceding claim, wherein each of the first set of rotors and the second set of rotors is arranged to operate at a speed of more than 25,000 revolutions per minute (rpm). [6] An electric drive unit according to any preceding claim, further comprising a first resolver disposed on a first countershaft in the first summing gear set, and a second resolver disposed on a second countershaft in the second summing gear set, the first resolver generating data indicative of a speed and position of the first set of rotors, and the second resolver generating data indicative of a speed of the second set of rotors. [7] An electric drive unit according to any preceding claim, further comprising a cooling system configured to direct coolant through a first set of laminations, a second set of laminations, end windings associated with the first set of laminations, and end windings associated with the second set of laminations included in the stator assembly. [8] The electric drive unit of claim 7, further comprising a pump motor rotatably coupled to a coolant pump, wherein the pump motor and the coolant pump are integrated into the first set of laminations and the second set of laminations. [9] Electric drive unit according to claim 7 or 8, wherein: the first set of laminations and the second set of laminations are separated by an oil distribution plate; and / or a baffle is used to distribute the coolant to the stator assembly. [10] Electric drive unit according to one of the preceding claims, wherein: the first summing gear set is rotationally coupled to a first drive wheel via a first final gear ratio; and the second summing gear set is rotationally coupled to a second drive wheel via a second final drive ratio.

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