Propulsion system with multiple motors having complementary torque bands

Abstract

The present invention discloses a propulsion system with multiple motors having complementary torque bands. The propulsion system includes: a first electric machine including a first set of machine windings configured to rotate a rotor about an axis to selectively drive a transmission during a first vehicle operating condition; and a second electric machine including a second set of machine windings configured to rotate a rotor about an axis to selectively drive the transmission during at least one of a first vehicle operating condition or a second vehicle operating condition. The second vehicle operating condition is different from the first operating condition, and the number of series turns per phase of the first set of machine windings is different from the number of series turns per phase of the second set of machine windings.

Description

Technical Field

[0001] The present disclosure relates to a vehicle electric propulsion system. More particularly, the present disclosure relates to an electric propulsion system having dual motors. Background Art

[0002] Some vehicles have been configured with electric axles and other electric motor devices to transfer and / or enhance the drive to the wheels. In certain vehicles, a multi-speed transmission in the electric axle and other electric drive train devices provides a speed conversion function. Compared with a single-speed transmission, a multi-speed transmission can enable the electric motor to operate more efficiently over a wider range of operating conditions. Summary of the Invention

[0003] According to several aspects, a vehicle propulsion system is disclosed. The vehicle propulsion system includes: a first motor including a first set of machine windings configured to rotate a rotor about an axis to selectively drive a transmission during a first vehicle operating state; and a second motor including a second set of machine windings configured to rotate a rotor about the axis to selectively drive the transmission during at least one of the first vehicle operating state or a second vehicle operating state. The second vehicle operating state is different from the first operating state, and the number of series turns per phase of the first set of machine windings is different from the number of series turns per phase of the second set of machine windings.

[0004] In other features, the vehicle propulsion system includes a controller operably connected to the first electric motor and the second electric motor, wherein the controller is configured to send a control signal to the first electric machine during the first vehicle operating state to cause the first electric machine to drive the transmission.

[0005] In other features, the controller is configured to send a control signal to the second electric machine during the second vehicle operating state to cause the second electric machine to drive the transmission.

[0006] In other features, the first operating state corresponds to a first torque band for operating the vehicle in a low power driving state.

[0007] In other features, the second operating state corresponds to a second torque band for operating the vehicle in a high power driving state.

[0008] In other features, the first motor includes a power converter and a traction motor, and the traction motor includes a first set of machine windings.

[0009] In other features, the power inverter includes a set of semiconductor switches configured to convert direct current (DC) electricity to alternating current (AC) electricity.

[0010] Among other features, the second electric machine includes a power converter and a traction motor, and the traction motor includes a second set of machine windings.

[0011] Among other features, the first electric machine includes a clutch that selectively engages the transmission in a first vehicle operating state.

[0012] Among other features, the second electric machine includes a clutch that selectively engages the transmission in a second vehicle operating state.

[0013] According to several aspects, a vehicle propulsion system is disclosed. The vehicle propulsion system includes: a first electric machine that includes a first set of machine windings configured to rotate a rotor about an axis to selectively drive a first transmission during a first vehicle operating state; and a second electric machine that includes a second set of machine windings configured to rotate a rotor about an axis to selectively drive a second transmission during a second vehicle operating state. The vehicle propulsion system further includes a controller operably connected to the first electric motor and the second electric motor. The controller is configured to send a control signal to the first electric machine during the first vehicle operating state to cause the first electric machine to drive the transmission. The second vehicle operating state is different from the first operating state, and the number of series turns per phase of the first set of machine windings is different from the number of series turns per phase of the second set of machine windings.

[0014] Among other features, the controller is configured to send a control signal to the second electric machine during the second vehicle operating state to cause the second electric machine to drive the transmission.

[0015] Among other features, the first operating state corresponds to a first torque band for operating the vehicle in a low power driving state.

[0016] Among other features, the second operating state corresponds to a second torque band for operating the vehicle in a high power driving state.

[0017] Among other features, the first electric machine includes a power converter and a traction motor, and the traction motor includes a first set of machine windings.

[0018] Among other features, the second electric machine includes a power converter and a traction motor, and the traction motor includes a second set of machine windings.

[0019] Among other features, the traction motor of the first electric machine is magnetically identical to the traction motor of the second electric machine, but the number of series turns per phase is different.

[0020] Among other features, the first electric machine includes a clutch that selectively engages the transmission in a first vehicle operating state.

[0021] Among other features, the second motor includes a clutch that selectively engages a transmission in a second vehicle operating state.

[0022] According to several aspects, a method is disclosed. The method can include: receiving a torque request signal; comparing a torque value corresponding to the torque request signal with a current operating state of the vehicle; and propelling the vehicle based on the comparison using at least one of a first motor or a second motor. The first motor includes a first set of machine windings, the second motor includes a second set of machine windings, and the number of series turns per phase of the first set of machine windings is different from the number of series turns per phase of the second set of machine windings.

[0023] From the description provided herein, further application areas will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

[0025] Figure 1 is a block diagram of a vehicle propulsion system according to an example implementation;

[0026] Figure 2 is a block diagram of another vehicle propulsion system according to another example implementation;

[0027] Figure 3 is a block diagram of a first motor for a vehicle propulsion system according to an example implementation;

[0028] Figure 4 is a block diagram of a second motor for a vehicle propulsion system according to an example implementation; and

[0029] Figure 5 is a flowchart of an example process for selecting a motor to propel a vehicle based on a torque request signal according to an example implementation. DETAILED DESCRIPTION

[0030] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0031] A battery electric vehicle (BEV) can include a propulsion system driven by an electric motor, the electric motor including a power inverter and a traction motor. Generally, these electric motors are configured to efficiently generate torque during certain operating modes. For example, a conventional machine with a constant power speed ratio greater than three may suffer from field weakening losses and the motor power may not be fully utilized. However, a wide torque band machine can be achieved by reducing the number of series turns per phase to provide higher power and lower high-speed losses, with a loss in cycle efficiency.

[0032] As described herein, a vehicle can include a propulsion system that includes a first electric machine having a first torque band characteristic and a second electric machine having a second torque band characteristic. The vehicle can include a controller that selects which electric machine to propel the vehicle based on a torque request signal to allow for optimal vehicle performance in normal (e.g., commuting) and high-performance driving conditions. For example, during commuting driving conditions, the controller selects the electric machine having the first torque band characteristic. During high-performance driving conditions (e.g., minimum power and torque loss above eight thousand revolutions per minute), the controller can select the electric machine having the second torque band characteristic. The controller can select which electric machine to propel the vehicle based on the operating state of the vehicle. The operating state can correspond to, for example, the revolutions per minute (RPM) value of the vehicle.

[0033] As used herein, the commuting driving condition can be referred to as a low-power driving condition, and the high-performance driving condition can be referred to as a high-power driving condition. The low-power driving condition can be defined as a vehicle driving mode where the total propulsion power of the vehicle is less than or equal to twenty percent (20%) and the vehicle speed can be less than or equal to fifty miles per hour (50 mph). The high-power driving condition can be defined as a vehicle driving mode where the total propulsion power of the vehicle is greater than or equal to eighty percent (80%) to achieve the maximum vehicle speed. In some cases, the total propulsion power of the vehicle in the high-power driving condition may be significantly more than eighty percent, i.e., at least five percent (5%) higher.

[0034] Figure 1 An example propulsion system 100 of a vehicle 102 according to an example embodiment is shown. In various embodiments, the vehicle 102 includes a battery electric vehicle (BEV). The propulsion system 100 can include vehicle 102 components such as the vehicle's powertrain and / or traction drive components, whose general function can include powering a traction motor to generate motor torque and transferring it to the drive wheels to propel the vehicle or perform other useful work on the vehicle 102. As shown, the propulsion system 100 can include a battery 104, a controller 106, a first electric machine 108, and a second electric machine 110.

[0035] In an example embodiment, the battery 104 can include an on-board rechargeable energy storage system (RESS), which can include one or more high-voltage, independently rechargeable battery packs that are adapted to store high-voltage electrical energy for propelling an electric drive vehicle. The RESS can be a deep-cycle, high ampere-capacity battery system, e.g., rated at approximately four hundred (400) to eight hundred (800) volts direct current (VDC) or higher, e.g., depending on the desired vehicle range, vehicle gross weight, and the rated power of the various loads drawing power from the RESS.

[0036] The controller 106 may include at least one processor and sufficient memory for storing computer-readable instructions. The memory includes tangible, non-transitory memory, such as read-only memory, whether optical, magnetic, flash, or other memory. The controller 106 also includes a sufficient amount of random access memory, electrically erasable programmable read-only memory, etc., as well as a high-speed clock, analog-to-digital and digital-to-analog circuitry, input / output circuitry and devices, and appropriate signal conditioning and buffering circuitry. The controller 106 may receive request signals issued by one or more electronic control units (ECUs) of the vehicle represented by the arrows. For example, an ECU associated with the vehicle 102 may provide a torque increase request signal. Based on the torque request signal, the controller 106 may send control signals to one or more switches that control the supply of electrical energy to the first motor 108 and / or the second motor 110. As described below, the motors 108, 110 may include clutches that selectively engage a transmission to propel the vehicle based on the torque request signal.

[0037] In Figure 1 In the illustrated embodiment, the first motor 108 and the second motor 110 are connected to a transmission 112. More specifically, the first motor 108 and the second motor 110 are rotatably connected to the input shaft of the transmission 112. In some embodiments, the transmission 112 may have a fixed gear ratio relationship that provides a single gear ratio between the input shaft and the output shaft of the transmission 112. A torque converter or a starting clutch may be provided between the first motor 108 and the transmission 112. In this embodiment, another torque converter or another starting clutch may be provided between the second motor 110 and the transmission 112. In another exemplary embodiment, the transmission 112 may be a multi-stage automatic transmission.

[0038] The output axle of the transmission 112 may be connected to a differential that drives the wheels 114-1, 114-2 via axles 116 connected to the differential. The differential delivers substantially equal torque to each of the wheels 114-1, 114-2 while allowing for minor speed differences, such as when the vehicle is turning. Different types of differentials or similar devices may be used to distribute torque from the powertrain to one or more wheels. In some applications, the torque distribution may vary according to the operating state or conditions. In the present disclosure, the axles 116 may be referred to as a fully electronic axle assembly, or an "e-axle" assembly.

[0039] The first electric machine 108 and the second electric machine 110 each include a respective power inverter 118, 120 and a respective traction motor 122, 124, which will be described in more detail below.

[0040] During a first operating state, the vehicle 102 can be driven by the first electric machine 108, and during a second operating state, the vehicle 102 can be driven by the second electric machine 110. In an example embodiment, the first operating state can include operating the vehicle 102 at a torque value within a first torque band, while the second operating state can include operating the vehicle 102 at a torque value within a second torque band. The torque band can represent a torque relationship as a function of revolutions per minute (RPM) and power. For example, the base speed of a battery electric vehicle with a particular propulsion system, measured in revolutions per minute, corresponds to the optimal operating efficiency, i.e., the minimum energy loss of the particular propulsion system. The base speed can be determined based on traction motor parameters (i.e., number of machine winding turns, operating voltage, power inverter type, etc.). In other words, if the speed of the vehicle increases beyond the base speed, there is energy loss and / or torque loss in the traction motor.

[0041] Based on the vehicle operating state, the controller 106 can select the first electric machine 110 such that the first electric machine 110 drives the transmission 112. In another example, based on the vehicle operating state, the controller 106 can select the second electric machine 112 such that the second electric machine 112 drives the transmission 112. In an example embodiment, the controller 106 can send control signals to the power inverters of the corresponding electric machines 108, 110 such that the selected electric machines 108, 110 are in an operating state, while the other of the electric machines 108, 110 is in an idle state. In another example embodiment, the electric machines 108, 110 can include respective clutches 126, 128 that selectively engage the input shaft of the transmission 112. In this embodiment, the clutches 126, 128 of the idle electric machines 108, 110 are disengaged.

[0042] Figure 2 An example propulsion system 200 of the vehicle 102 according to another example embodiment of the present disclosure is shown. As shown, the vehicle 102 can include two e - axle assemblies. For example, the vehicle 102 can include a first transmission 202 operatively connected to a first axle 204, and can include a second transmission 206 operatively connected to a second axle 208. The vehicle 102 also includes a first electric machine 108 operatively connected to the first transmission 202 and a second electric machine 110 operatively connected to the second transmission 206. The first transmission 202 can drive the first axle 204, and the second transmission 206 can drive the second axle 208. As shown, a first set of wheels 210 - 1, 210 - 2 are connected to the first axle 204, and a second set of wheels 212 - 1, 212 - 2 are connected to the second axle 208. In this embodiment, the clutch 126 of the first electric machine 108 can selectively engage the input shaft of the transmission 204 during operation, and the clutch 128 of the second electric machine 110 can engage the input shaft of the transmission 206 during operation.

[0043] As described herein, the controller 106 determines the vehicle operating state based on the torque request signal and selects the electric machines 108, 110 to propel the vehicle 102 based on the vehicle operating state. The torque request signal can be generated based on, for example, the pedal position within the vehicle 102. For example, the ECU of the vehicle 102 can receive an electrical signal from the pedal. Based on the electrical signal, the ECU accesses a look-up table that correlates the electrical signal value with a torque value.

[0044] In some cases, the two motors 108, 110 can operate simultaneously to maximize power throughput, optimize efficiency, and / or reduce shift transients in the case of a multi-speed transmission. In some embodiments, when the vehicle 102 is operating in a low power driving state, the motors 108, 110 can operate simultaneously and are configured to provide intermittent supplementary torque to the electric motors 108, 110 configured to operate in a high power driving state. In other embodiments, when the vehicle 102 is operating in a high power driving state, the electric motors 108, 110 can operate simultaneously.

[0045] Reference Figure 3 and Figure 4 , the first motor 108 includes a power inverter 116 and a traction motor 122, and the second motor 110 includes a power inverter 116 and a traction motor 124. The respective power inverters 116, 118 control the electrical energy transfer between the corresponding traction motors 122, 124.

[0046] Reference Figure 3 , the traction motor 122 includes a first set of three machine windings L1, L2, and L3 that provide three-phase current to generate a rotating magnetic field to rotate the rotor of the traction motor 122. According to an embodiment of the present disclosure, the rotor of the traction motor 122 can be connected to the input shaft of the corresponding transmission. For example, a clutch 126 can be located between the rotor and the output shaft of the transmission.

[0047] Reference Figure 4 , the traction motor 124 includes a second set of three machine windings L4, L5, and L6 that provide three-phase current to generate a rotating magnetic field to rotate the rotor of the traction motor 124. According to an embodiment of the present disclosure, the rotor of the traction motor 124 can be connected to the input shaft of the corresponding transmission. For example, a clutch 128 can be located between the rotor and the output shaft of the transmission. Although three-phase current is described above, it should be understood that the traction motors 122, 124 can include additional machine windings to provide additional phases. For example, in some embodiments, there can be three to six phases. In other embodiments, the traction motor can be extended to nine phases.

[0048] Vehicle 102 can be propelled by at least one of a first electric machine 108 or a second electric machine 110. A first set 301 of machine windings L1, L2, and L3 is different from a second set 303 of machine windings L4, L5, and L6. For example, the first set 301 of machine windings L1, L2, and L3 can correspond to a first torque band, and the second set 303 of machine windings L4, L5, and L6 can correspond to a second torque band. In an example embodiment, the number of series turns per phase of the first set 301 of machine windings L1, L2, and L3 can be less than the number of series turns per phase of the second set 303 of machine windings L4, L5, and L6. In this embodiment, the first set 301 of machine windings L1, L2, and L3 can correspond to a first torque band, and the second set 303 of machine windings L4, L5, and L6 corresponds to a second torque band. The torque band ratio between the first electric machine 108 and the second electric machine 110 can vary according to the vehicle operating state and / or the available battery 104 voltage.

[0049] As described above, the number of series turns per phase included in the first set 301 of machine windings L1, L2, and L3 is different from the number of series turns per phase of the second set 303 of machine windings L4, L5, and L6. For example, the number of series turns per phase of the machine windings L1, L2, and L3 can be less than the number of series turns per phase of the machine windings L4, L5, and L6, e.g., the number of series turns per phase of the machine windings L4, L5, and L6 is more. However, in addition to the difference in the number of series turns per phase, the first electric machine 108 and the second electric machine 110 are identical in magnetic design. In an example embodiment, the first electric machine 108 including the machine windings L1, L2, and L3, i.e., the machine with the larger torque band, can include an integrated multi-speed transmission 127 therein.

[0050] The power inverters 116, 118 may each include a set of semiconductor switches (also referred to herein as "inverter switches") that cooperate during vehicle operation to convert direct current (DC) power from the battery 104 into alternating current (AC) power for powering the corresponding traction motors 122, 124 through high-frequency switching. Each semiconductor switch may be embodied as a voltage-controlled switching device in the form of a silicon insulated-gate bipolar transistor (IGBT), a silicon carbide (SiC) metal-oxide semiconductor field-effect transistor (MOSFET), a silicon (Si) superjunction MOSFET, a gallium nitride (GaN) field-effect transistor (FET), a SiC junction-gate field-effect transistor (JFET), other wide-bandgap (WBG) or ultra-wide-bandgap semiconductor power switching devices (UWBG), or other suitable switches with corresponding gates to which a gate signal is applied to change the on / off state of a given switch. Each phase leg 302, 304, 306 of the three-phase traction motors 122, 124 typically has at least a pair of semiconductor switches, and each phase leg 302, 304, 306 of the power inverters 116, 118 is connected to a corresponding motor phase terminal, such as one of the machine windings of the corresponding traction motors 122, 124.

[0051] Figure 5 FIG. 500 is a flow chart of an example process 500 for selecting the electric machines 108, 110 for propelling the vehicle 102. The blocks of process 500 may be executed by the controller 106. Process 500 begins at block 502 where it is determined whether a torque request signal is received. If no torque request signal is received, process 500 returns to block 502.

[0052] Otherwise, at block 504, the controller 106 compares the torque value corresponding to the torque request signal with the current operating state of the vehicle 102. The current operating state may be defined as a low-power driving state or a high-power driving state, such as an increased vehicle speed or a wide-open throttle (WOT) condition. The controller 106 may include a look-up table that associates the torque value with the vehicle operating state and the losses associated with the electric motors and the power inverters. In some examples, the controller logic takes into account pre-calibrated losses to optimize the efficiency of which motor 108, 110 should operate at a defined load level.

[0053] At block 506, the controller 106 decides whether to switch from one electric machine (e.g., one of electric machines 108 or 110) to another electric machine (e.g., the other of electric machines 108 or 110) based on the comparison. For example, based on the comparison, the torque value may indicate that vehicle 102 will operate at a vehicle operating state that is increased relative to the current vehicle operating state. In another example, based on the comparison, the torque value may indicate that vehicle 102 will operate at a vehicle operating state that is decreased relative to the current vehicle operating state. Thus, based on this comparison, the controller 106 can determine the electric machines 108, 110 for optimization purposes because the first electric machine 108 includes machine windings configured for a first torque band while the second electric machine 110 includes machine windings configured for a second torque band.

[0054] If the controller 106 decides that no switch is needed, the process 500 returns to block 502. Otherwise, at block 508, the controller 106 generates one or more control signals to cause one of the electric machines 108, 110 to transition between an operating state and an idle state so that the other of the electric machines 108, 110 propels the vehicle 102. For example, the controller 106 may send control signals to the corresponding power inverters 116, 118 to control the operation of the inverter switches. In another example, the controller 106 may send control signals to the corresponding clutches 126, 128 to selectively engage or disengage from the input shaft of the transmission. When the vehicle 102 is operating in a high power driving state, the controller 106 may select the electric machine 108, 110 having the fewest number of series turns per phase of the machine windings. When the vehicle 102 is operating in a low power driving state, the controller 106 may select the electric machine 108, 110 having a larger number of series turns per phase of the machine windings. Then, the process 500 ends.

[0055] The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. Such variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A vehicle propulsion system, comprising: A first electric machine, including a first set of machine windings configured to rotate a rotor about an axis to selectively drive a transmission during a first vehicle operating condition; And A second electric machine, including a second set of machine windings configured to rotate a rotor about the axis to selectively drive the transmission during at least one of the first vehicle operating condition or a second vehicle operating condition, the second vehicle operating condition being different from the first vehicle operating condition, Wherein, the total number of series turns per phase of the first set of machine windings is different from the total number of series turns per phase of the second set of machine windings.

2. The vehicle propulsion system according to claim 1 further includes a controller operatively connected to the first motor and the second motor, wherein, The controller is configured to send a control signal to the first electric machine during the first vehicle operating condition to cause the first electric machine to drive the transmission.

3. The vehicle propulsion system according to claim 2, wherein, The controller is configured to send a control signal to the second electric machine during the second vehicle operating condition to cause the second electric machine to drive the transmission.

4. The vehicle propulsion system according to claim 1, wherein, The first vehicle operating condition corresponds to a first torque band for operating the vehicle in a low power driving condition.

5. The vehicle propulsion system according to claim 4, wherein, The second vehicle operating condition corresponds to a second torque band for operating the vehicle in a high power driving condition.

6. The vehicle propulsion system according to claim 1, wherein, The first electric machine includes a power converter and a traction motor, the traction motor including the first set of machine windings.

7. The vehicle propulsion system according to claim 6, wherein, The power converter includes a set of semiconductor switches configured to convert direct current (DC) electricity to alternating current (AC) electricity.

8. The vehicle propulsion system according to claim 1, wherein The second electric machine includes a power converter and a traction motor, the traction motor including the second set of machine windings.

9. The vehicle propulsion system according to claim 1, wherein, The first electric machine includes a clutch that selectively engages the transmission in the first vehicle operating condition.

10. The vehicle propulsion system according to claim 1, wherein, The second electric machine includes a clutch that selectively engages the transmission in the second vehicle operating condition.

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