Vehicle drive systems

Abstract

To realize a technology that can easily increase the amount of heat generated while suppressing the level of noise that may cause discomfort to vehicle occupants when generating heat required in a vehicle using a rotating electric machine. [Solution] The control device provided in the vehicle drive system is configured to perform a current determination process that determines the d-axis current and the q-axis current according to the target torque of the rotating electric machine, a PWM signal generation process that generates a switching signal for PWM control of the inverter, and a carrier frequency determination process that determines the carrier frequency for PWM control. In the current determination process, the control device selectively performs a normal mode and a heat generation mode. In the carrier frequency determination process, when the heat generation mode is selected, the control device sets the carrier frequency higher than when the normal mode is selected.

Description

[Technical Field]

[0001] The present invention relates to a vehicle drive system comprising a rotating electric machine, an inverter, a control device for controlling the rotating electric machine via the inverter, and a drive transmission mechanism for transmitting the driving force of the rotating electric machine to the wheels. [Background technology]

[0002] An example of such a vehicle drive device is disclosed in Japanese Patent Laid-Open Publication No. 2012-165526 ​​(Patent Document 1). Hereinafter, in the description of the background art, reference numerals in parentheses refer to those in Patent Document 1. The vehicle drive device of Patent Document 1 includes a motor (10), an inverter (11), a motor ECU (12) that controls the motor (10) via the inverter (11) by vector control, and a reducer (1) that transmits the driving force of the motor (10) to driving wheels (2a, 2b). The motor ECU (12) calculates d-axis and q-axis currents in the vector control in accordance with the required driving torque of the motor (10) and converts the calculated d-axis and q-axis currents into pulse signals (PWM signals) for controlling the inverter (11). In accordance with the pulse signals, the inverter (11) converts DC power from a battery (20) into AC power and supplies the AC power to the motor (10). The temperature of the battery (20) rises due to self-heating caused by drawing current from the battery (20).

[0003] In the vehicle drive device of Patent Document 1, when warming up of the battery (20) is required, the motor ECU (12) calculates a target total current (Ia) to be drawn from the battery (20) taking into consideration the warming up of the battery (20) as well as the required drive torque of the motor (10). The motor ECU (12) then sets a d-axis current from the target total current (Ia) and a q-axis current determined according to the required drive torque, using equation (5) described in Patent Document 1. The d-axis current thus set is corrected for warming up, and as described in paragraph 0033 of Patent Document 1, the d-axis current is corrected to increase as the temperature of the battery (20) decreases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-165526 [Overview of the Initiative] [Problem to be solved by the invention]

[0005] As described above, in the technology described in Patent Document 1, the d-axis current is corrected to generate heat required in the vehicle (heat for warming up the battery in Patent Document 1). However, correcting the d-axis current increases the amount of current flowing through the rotating electric machine (a motor in Patent Document 1) compared to when the same amount of torque is generated in the rotating electric machine without correcting the d-axis current. Furthermore, when the amount of current flowing through the rotating electric machine increases, noise that may cause discomfort to vehicle occupants, such as noise due to magnetostriction, tends to increase. Therefore, in the technology described in Patent Document 1, it is necessary to limit the amount of correction of the d-axis current to a range in which the level of noise that may cause discomfort to vehicle occupants is below an acceptable level, which can make it difficult to increase the amount of heat generated.

[0006] Therefore, when using a rotating electric machine to generate the necessary heat in a vehicle, it is desirable to realize a technology that makes it easy to increase the amount of heat generated while keeping the level of noise that could cause discomfort to vehicle occupants low. [Means for solving the problem]

[0007] The vehicle drive system according to this disclosure comprises: a rotating electric machine equipped with a rotor; an inverter that generates AC power to be supplied to the rotating electric machine; a control device that controls the rotating electric machine via the inverter by vector control using an orthogonal vector coordinate system of a d-axis along the direction of the magnetic field of the rotor and a q-axis perpendicular to the d-axis; and a drive transmission mechanism that transmits the driving force of the rotating electric machine to the wheels, wherein the control device performs a current determination process that determines a d-axis current and a q-axis current according to a target torque which is the target output torque of the rotating electric machine, and based on the d-axis current and the q-axis current determined by the current determination process, the control device performs the following: The control device is configured to perform a PWM signal generation process for generating a switching signal for PWM control of a converter, and a carrier frequency determination process for determining the carrier frequency of the PWM control, wherein in the current determination process, the control device selectively executes a normal mode and a heat generation mode, the heat generation mode is a mode in which the magnitude of the combined vector of the d-axis current and the q-axis current is increased for the same target torque compared to the normal mode, and in the carrier frequency determination process, when the heat generation mode is selected, the control device sets the carrier frequency higher than when the normal mode is selected.

[0008] With this configuration, selecting the heat generation mode increases the magnitude of the composite vector, thereby increasing the losses (amount of loss) in the rotating electric machine. Here, when heat generation mode is selected, the carrier frequency is set higher than when normal mode is selected, making it easier to reduce noise generated from the rotating electric machine, such as noise due to magnetostriction, to a frequency that is difficult for humans to perceive. Therefore, in heat generation mode, it is possible to increase the magnitude of the composite vector and increase the losses in the rotating electric machine while keeping the level of noise that could cause discomfort to vehicle occupants low, thereby making it easier to increase the amount of heat generated in heat generation mode. In addition, in heat generation mode, the higher carrier frequency increases the switching loss in the inverter, and thus the losses in the inverter also increase. With this configuration, it is also easier to increase the amount of heat generated in heat generation mode from this point of view.

[0009] As described above, with this configuration, when using a rotating electric machine to generate the necessary heat in a vehicle, it is easier to increase the amount of heat generated while keeping the noise level that could cause discomfort to vehicle occupants low.

[0010] Further features and advantages of the vehicle drive system will become apparent from the following description of the embodiments, which is given with reference to the drawings. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a vehicle equipped with a vehicle drive device according to an embodiment; [Figure 2] Circuit diagram of an inverter according to an embodiment [Figure 3] Control block diagram of a control device according to an embodiment. [Figure 4] FIG. 10 is an explanatory diagram of a heat generation mode according to an embodiment; [Figure 5] Control flow diagram of carrier frequency determination processing according to an embodiment [Figure 6] FIG. 1 is a diagram showing a carrier frequency map according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of vehicle drive systems will be described with reference to the drawings. In this specification, the term "rotating electric machine" is used as a concept that includes motors, generators, and motor-generators that perform both motor and generator functions as needed. In this specification, "drive coupling" refers to a state in which two rotating elements are coupled in a manner that can transmit driving force, and includes a state in which the two rotating elements are coupled so as to rotate as a whole, or a state in which the two rotating elements are coupled in a manner that can transmit driving force via one or more transmission members. Such transmission members include various members that transmit rotation at the same speed or at a variable speed, such as shafts, gear mechanisms, belts, chains, etc. In addition, the transmission members may include engagement devices that selectively transmit rotation and driving force, such as friction engagement devices, meshing engagement devices, etc.

[0013] The vehicle 100 on which the vehicle drive device 10 is mounted is an electric vehicle, such as a battery electric vehicle (BEV), that has a rotating electric machine 4 as a driving force source for wheels W. The vehicle drive device 10 transmits the driving force of the rotating electric machine 4 to the wheels W to make the vehicle 100 run. FIG. 1 illustrates a case in which the vehicle drive device 10 is configured to transmit only the driving force of the rotating electric machine 4 to the wheels W. The vehicle 100 may also be provided with a driving force source (for example, an internal combustion engine) other than the rotating electric machine 4, and the vehicle drive device 10 may be configured to transmit the driving force of the other driving force source to the wheels W as well.

[0014] As shown in Fig. 1, the vehicle drive system 10 includes a rotating electric machine 4 and a drive transmission mechanism 5 that transmits the driving force of the rotating electric machine 4 to wheels W. As shown in Fig. 2, the vehicle drive system 10 further includes an inverter 7 that generates AC power to be supplied to the rotating electric machine 4, and a control device 1 that controls the rotating electric machine 4 via the inverter 7.

[0015] The rotating electric machine 4 is electrically connected to a DC power supply 6 (see FIG. 2 ), such as a battery or a capacitor, via an inverter 7. The rotating electric machine 4 generates driving force by powering using the electric power stored in the DC power supply 6. The rotating electric machine 4 also generates electricity using driving force transmitted to the rotating electric machine 4 (for example, driving force transmitted from the wheels W), thereby charging the DC power supply 6.

[0016] The rotating electric machine 4 includes a rotor 41. The rotating electric machine 4 further includes a stator 42, and the rotor 41 is supported by a non-rotating member (for example, a case that houses the rotating electric machine 4 and the drive transmission mechanism 5) so as to be rotatable relative to the stator 42. The rotor 41 is fixed to a rotor shaft 40 and rotates integrally with the rotor shaft 40. A stator coil 43 is wound around the stator 42. In this embodiment, the rotating electric machine 4 is a rotating electric machine that is driven by three-phase AC, and three-phase stator coils 43 are wound around the stator 42. FIG. 2 illustrates an example in which the three-phase stator coils 43 are star-connected.

[0017] In this embodiment, the rotating electric machine 4 is a permanent magnet type synchronous rotating electric machine (PMSM), and the rotor 41 is equipped with permanent magnets (not shown). The rotating electric machine 4 may be a synchronous rotating electric machine other than a permanent magnet type. For example, an electrically excited synchronous rotating electric machine (EESM) can be used as the rotating electric machine 4, in which case rotor coils are wound around the rotor 41. Furthermore, the rotating electric machine 4 may be an induction rotating electric machine instead of a synchronous rotating electric machine.

[0018] As shown in Figure 1, in this embodiment, the drive transmission mechanism 5 comprises an input member 51 and a gear mechanism 50. The input member 51 is drive-connected to the rotor shaft 40. The input member 51 is connected to the rotor shaft 40, for example, so as to rotate integrally with the rotor shaft 40. The input member 51 may be integrally formed with the rotor shaft 40. The gear mechanism 50 comprises, for example, a drive shaft and gears. The gear mechanism 50 may include engagement devices such as a clutch or a brake. The gear mechanism 50 is configured to transmit the rotation of the input member 51 to one or more wheels W. In this embodiment, the gear mechanism 50 is configured to transmit the rotation of the input member 51 to a pair of wheels W (left and right wheels W). Specifically, the gear mechanism 50 includes a differential gear mechanism 55 that distributes the rotation transmitted from the input member 51 to a pair of wheels W via a pair of drive shafts 59.

[0019] The gear mechanism 50 may include a transmission that changes the speed (for example, reduces) of the rotation of the input member 51 and transmits it to the differential gear mechanism 55. Also, although Figure 1 illustrates a configuration in which the rotating electric machine 4 and the differential gear mechanism 55 are arranged on separate shafts, it is also possible to configure the rotating electric machine 4 and the differential gear mechanism 55 to be arranged on the same axis.

[0020] As shown in FIG. 2, the inverter 7 is configured to convert power between direct current and multi-phase (three-phase in this embodiment) alternating current. The inverter 7 is configured using a plurality of switching elements. Examples of the switching elements include power transistors such as IGBTs (Insulated Gate Bipolar Transistors), power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and HEMTs (High Electron Mobility Transistors). The inverter 7 includes a plurality of arms each formed by a series circuit of an upper-stage switching element and a lower-stage switching element. The plurality of arms are connected in parallel to form a bridge circuit. In the example shown in FIG. 2, the inverter 7 includes one arm corresponding to each of the three phases, and the three arms are connected in parallel to form a bridge circuit.

[0021] The intermediate point (the connection point between the upper-side switching element and the lower-side switching element) of each arm included in the inverter 7 is connected to the stator coil 43, and the inverter 7 supplies multi-phase (three-phase in this embodiment) AC power to the stator coil 43. A DC link capacitor 63 (smoothing capacitor) that smoothes the voltage on the DC side of the inverter 7 is provided on the DC side of the inverter 7 (i.e., between the inverter 7 and the DC power source 6).

[0022] The vehicle drive device 10 is configured to generate heat required in the vehicle 100 by using the rotating electric machine 4. The heat generated by the rotating electric machine 4 is utilized in heat utilization equipment (for example, a heating device for the vehicle interior or a temperature regulator for a DC power supply 6 such as a battery) provided in the vehicle 100. In this embodiment, the heat generated by the inverter 7 is also utilized in the heat utilization equipment. That is, in this embodiment, the inverter 7, in addition to the rotating electric machine 4, is utilized as a heat source for the heat utilization equipment.

[0023] Although details are omitted, the vehicle drive system 10 is equipped with a heat transfer medium circuit through which a heat transfer medium (heat exchange medium) circulates. The heat transfer medium may be a water-based heat transfer medium or a non-water-based (e.g., fluorine-based) heat transfer medium. An example of a water-based heat transfer medium is antifreeze (cooling water) called LLC (Long Life Coolant). The heat transfer medium circuit is arranged so as to pass through a first heat exchange section where heat exchange takes place between the heat transfer medium and the rotating electric machine 4, a second heat exchange section where heat exchange takes place between the heat transfer medium and the inverter 7, and a third heat exchange section where heat exchange takes place between the heat transfer medium and the heat utilization equipment. Heat is transferred from the rotating electric machine 4 to the heat transfer medium by heat exchange in the first heat exchange section, heat is transferred from the inverter 7 to the heat transfer medium by heat exchange in the second heat exchange section, and heat is transferred from the heat transfer medium to the heat utilization equipment by heat exchange in the third heat exchange section.

[0024] Furthermore, the heat exchange between the heat transfer medium and the objects to be heated (in this case, the rotating electric machine 4, the inverter 7, and the heat utilization equipment) in the heat exchange section may be carried out directly or indirectly (for example, via another heat transfer medium such as oil or gas). For example, if the rotating electric machine 4 is cooled by oil, the first heat exchange section can be configured to perform heat exchange between the heat transfer medium and the oil. In this case, the heat exchange between the heat transfer medium and the rotating electric machine 4 in the first heat exchange section is carried out indirectly via the oil.

[0025] The control device 1 controls the switching of an inverter 7, which is composed of multiple switching elements, to cause the inverter 7 to convert power between DC and multi-phase (3-phase in this embodiment) AC. The control device 1 is composed of logic circuits such as a microcomputer as its core component. Each function of the control device 1 (for example, the functions of each functional unit 11 to 13 shown in Figure 3) is realized through the cooperation of hardware such as a microcomputer and software (program).

[0026] The control device 1 controls the rotating electric machine 4 via the inverter 7 by vector control using an orthogonal vector coordinate system with a d-axis along the direction of the magnetic field (direction of magnetic flux) of the rotor 41 and a q-axis perpendicular to the d-axis. When the rotating electric machine 4 is a permanent magnet type synchronous rotating electric machine like the rotating electric machine 4 of this embodiment, or when the rotating electric machine 4 is a wound field type synchronous rotating electric machine, the direction of the field magnetic flux becomes the d-axis. When the rotating electric machine 4 is an induction rotating electric machine, the direction of the secondary magnetic flux generated in the rotor 41 becomes the d-axis.

[0027] The control device 1 controls the rotating electric machine 4 via the inverter 7 so that the rotating electric machine 4 outputs a target torque. Here, the target torque is a target for the output torque of the rotating electric machine 4. The torque required to be transmitted to the wheels W is defined as the wheel required torque, and the target torque is set, for example, to a torque obtained by converting the wheel required torque into a torque at the rotating electric machine 4 (specifically, a torque obtained by dividing the wheel required torque by the overall gear ratio of the power transmission path from the rotating electric machine 4 to the wheels W). The target torque is determined by the control device 1, or by another device capable of communicating with the control device 1 (for example, a vehicle control device that controls the entire vehicle 100 in an integrated manner). In the latter case, the target torque determined by the other device is provided to the control device 1.

[0028] The target torque is a torque required by the vehicle 100. The target torque is determined, for example, in response to a driving operation by the driver or in response to a command from a system such as a driving assistance system or an automatic driving system. The vehicle 100 is provided with sensors that detect information necessary for determining the target torque. For example, the vehicle 100 is provided with sensors that detect the driving operation by the driver (accelerator operation, brake operation, steering operation, etc.) and sensors that detect the vehicle state (travel speed of the vehicle 100, acceleration of the vehicle 100, etc.).

[0029] The control device 1 is configured to execute a current determination process, a PWM signal generation process, and a carrier frequency determination process. Specifically, as shown in Fig. 3, the control device 1 includes a current determination unit 11 which is a functional unit that executes the current determination process, a PWM signal generation unit 13 which is a functional unit that executes the PWM signal generation process, and a carrier frequency determination unit 12 which is a functional unit that executes the carrier frequency determination process. Note that these functional units 11 to 13 are at least logically or conceptually distinct, and do not necessarily need to be physically distinct.

[0030] The current determination process is a process for determining a d-axis current Id and a q-axis current Iq in accordance with a target torque. The d-axis current Id and the q-axis current Iq are two-phase currents in a dq-axis Cartesian coordinate system. Specifically, the d-axis current Id is the d-axis component of a current vector representing a current (an armature current in this embodiment) flowing through the rotating electric machine 4 (specifically, the stator coil 43), and the q-axis current Iq is the q-axis component of the current vector. That is, the resultant vector Idq (see FIG. 4) of the d-axis current Id and the q-axis current Iq becomes the above-mentioned current vector.

[0031] The control device 1 selectively executes a normal mode or a heat generation mode in the current determination process. The modes selectively executed by the control device 1 in the current determination process may include modes other than the normal mode and the heat generation mode. The control device 1 selectively executes the normal mode or the heat generation mode, for example, depending on whether or not there is a heat generation request from the vehicle 100. In this case, the control device 1 executes the normal mode when there is no heat generation request, and executes the heat generation mode when there is a heat generation request. For example, when it is determined that the amount of heat required for the heat utilization equipment described above (e.g., the amount of heat required to heat the passenger compartment or the amount of heat required to warm up the DC power source 6 such as a battery) is insufficient, it is determined that there is a heat generation request. The presence or absence of a heat generation request may be determined by the control device 1 or by another device capable of communicating with the control device 1 (e.g., the vehicle control device described above). In the latter case, the result of the determination by the other device as to whether or not there is a heat generation request is provided to the control device 1.

[0032] The normal mode is a mode in which control that increases losses in the rotating electric machine 4 (inefficiency control) is not performed. In this embodiment, in the normal mode, the d-axis current Id and the q-axis current Iq are determined by maximum torque control. The maximum torque control is control that determines the phase (current phase) of the resultant vector Idq so that the output torque of the rotating electric machine 4 is maximized for the same current. The maximum torque control makes it possible to generate the target torque with the minimum current (the resultant vector Idq of the minimum magnitude). Note that the normal mode can also be configured to determine the d-axis current Id and the q-axis current Iq by control other than the maximum torque control. An example of control other than the maximum torque control is maximum efficiency control. While the maximum torque control is control that determines the resultant vector Idq so that the current is minimized for the same output torque, the maximum efficiency control is control that determines the resultant vector Idq so that the loss is minimized for the same output torque.

[0033] The heat generation mode is a mode in which the magnitude of a resultant vector Idq of the d-axis current Id and the q-axis current Iq is increased for the same target torque compared to the normal mode. A specific example of the heat generation mode will be described with reference to FIG. 4. FIG. 4 shows an equal torque line L1, a maximum torque control line L2, a voltage limit ellipse L3, and a current limit circle L4. The equal torque line L1 represents the locus of the resultant vector Idq at which the rotating electric machine 4 outputs a certain target torque. The maximum torque control line L2 represents the locus of the resultant vector Idq determined by maximum torque control. The voltage limit ellipse L3 represents a limit determined according to the DC side voltage of the inverter 7 (the voltage of the DC power supply 6 in the example shown in FIG. 2) and the rotational speed of the rotating electric machine 4. The current limit circle L4 represents a limit determined according to the rated current of the rotating electric machine 4. The operating point of the rotating electric machine 4 must be inside the voltage limit ellipse L3 and the current limit circle L4.

[0034] In this embodiment, in the normal mode, the operating point of the rotary electric machine 4 is determined by maximum torque control. Therefore, in Fig. 4, the intersection of the equal torque line L1 and the maximum torque control line L2 is the operating point in the normal mode (first operating point P1). That is, the d-axis current Id and the q-axis current Iq at the first operating point P1 are the d-axis current Id and the q-axis current Iq determined according to the target torque in the normal mode.

[0035] In the heat creation mode, the operating point of the rotating electric machine 4 is determined to be a point on the equal torque line L1 that is different from the first operating point P1 (a point with a different current phase from the first operating point P1). That is, in the heat creation mode, the operating point of the rotating electric machine 4 is determined to be a point moved from the first operating point P1 along the equal torque line L1. This allows the rotating electric machine 4 to output the same target torque as in the normal mode while increasing the magnitude of the resultant vector Idq compared to the normal mode. The second operating point P2 and the third operating point P3 in FIG. 4 are examples of operating points in the heat creation mode. The d-axis current Id and the q-axis current Iq at the second operating point P2 and the third operating point P3 are the d-axis current Id and the q-axis current Iq determined according to the target torque in the heat creation mode.

[0036] The second operating point P2 is an operating point (hereinafter referred to as an "operating point on the retard side") that is set so that the d-axis current Id has a value on the positive side (field-strengthening side) compared to the first operating point P1. The third operating point P3 is an operating point (hereinafter referred to as an "operating point on the advance side") that is set so that the d-axis current Id has a value on the negative side (field-weakening side) compared to the first operating point P1. For example, of an operating point on the retard side such as the second operating point P2 and an operating point on the advance side such as the third operating point P3, the operating point that can increase the loss of the rotating electric machine 4 can be determined as the operating point of the rotating electric machine 4 in the heat generation mode.

[0037] In the heat creation mode, the magnitude of the resultant vector Idq is made larger than in the normal mode, thereby making it possible to increase losses (particularly copper losses) of the rotating electric machine 4. Preferably, in the heat creation mode, the resultant vector Idq (operating point of the rotating electric machine 4) is determined so that losses (losses including copper loss and iron loss) of the rotating electric machine 4 are larger than in the normal mode. For example, of an operating point on the retard side and an operating point on the advance side, an operating point that can increase losses (losses including copper loss and iron loss) of the rotating electric machine 4 can be determined as the operating point of the rotating electric machine 4 in the heat creation mode. In general, iron losses of the rotating electric machine 4 are larger at an operating point on the retard side than at an operating point on the advance side, and therefore losses (losses including copper loss and iron loss) of the rotating electric machine 4 are more likely to be increased.

[0038] The PWM signal generation process is a process of generating a switching signal for PWM (Pulse Width Modulation) control of the inverter 7 based on the d-axis current Id and q-axis current Iq determined by the current determination process. The switching signal is a control signal (on / off signal) that controls the switching of a switching element included in the inverter 7. The switching signal is, for example, a gate drive signal. Between the control device 1 and the inverter 7, for example, a driver (drive circuit) is provided that amplifies the voltage of the switching signal output from the control device 1, increases the driving force, and supplies it to the inverter 7.

[0039] PWM control is a control that modulates the pulse width (on time) of a control signal for a switching element. In the PWM signal generation process, a PWM signal, which is a switching signal for PWM control, is generated based on the carrier frequency determined by the carrier frequency determination process. Specifically, in the PWM signal generation process, a voltage command (in this embodiment, a three-phase voltage command) is generated based on the d-axis current Id and q-axis current Iq determined by the current determination process. Then, a PWM signal with a pulse waveform of the carrier frequency is generated from the generated voltage command. For example, the PWM signal is generated from the voltage command using a carrier comparison method that compares the voltage command with a carrier signal of the carrier frequency.

[0040] In the PWM signal generation process, a PWM signal is generated by asynchronous PWM control. With asynchronous PWM control, it is not necessary to synchronize the carrier with the voltage command, so the carrier frequency can be set arbitrarily. Although details are omitted, in certain situations (for example, when the vehicle speed of the vehicle 100 is in a speed range where asynchronous PWM control cannot properly drive the rotating electric machine 4), the control device 1 can also be configured to drive the rotating electric machine 4 by synchronous PWM control (for example, 1-pulse control) using a carrier synchronized with the voltage command.

[0041] In this embodiment, voltage commands are generated by performing current feedback control during the PWM signal generation process. Current feedback control is performed based on the rotational position of the rotor 41 (in this embodiment, the magnetic pole position of the field), the rotational speed of the rotor 41, and the current flowing through the stator coils 43 of each phase. In the example shown in Figure 2, the current flowing through the stator coils 43 is detected by a current sensor 61, and the rotational position and rotational speed of the rotor 41 are detected by a rotation sensor 62, such as a resolver or an inductive position sensor.

[0042] In current feedback control, a voltage command is generated based on the deviation between the current command and the feedback current, for example, by performing proportional-integral control or proportional-integral-derivative control. Specifically, the d-axis current Id and q-axis current Iq determined by the current determination process become the two-phase current command. In addition, the current flowing through the stator coil 43 of each phase is converted into a two-phase feedback current by coordinate transformation (three-phase to two-phase coordinate transformation). Then, a d-axis voltage command is generated based on the deviation between the d-axis current command and the d-axis feedback current, and a q-axis voltage command is generated based on the deviation between the q-axis current command and the q-axis feedback current. The two-phase voltage commands of the d-axis and q-axis are converted into a three-phase voltage command by coordinate transformation (two-phase to three-phase coordinate transformation).

[0043] The carrier frequency determination process determines the carrier frequency for PWM control. The carrier frequency determination process determines the carrier frequency used for asynchronous PWM control. In the heat generation mode, the magnitude of the resultant vector Idq is larger for the same target torque than in the normal mode, resulting in a larger amount of current flowing through the rotating electric machine 4. A larger amount of current flowing through the rotating electric machine 4 increases the change in the magnetic field, which tends to increase noise due to magnetostriction. In consideration of this, when the heat generation mode is selected in the carrier frequency determination process, the control device 1 sets a higher carrier frequency than when the normal mode is selected. By increasing the carrier frequency, noise generated by the rotating electric machine 4, such as noise due to magnetostriction, tends to be at a frequency that is difficult for humans to detect. On the other hand, in the normal mode, lowering the carrier frequency can reduce switching loss in the inverter 7. Note that lowering the carrier frequency can increase iron loss in the rotating electric machine 4 and reduce controllability of the rotating electric machine 4. Therefore, the carrier frequency in the normal mode is set taking these iron loss and controllability into consideration.

[0044] As an example, in the carrier frequency determination process, when the control device 1 selects the heat generation mode, it is preferable to set the carrier frequency so that the frequency of magnetostrictive vibrations (frequency of magnetostrictive noise) generated at that carrier frequency is higher than the human audible range. Empirically, the frequency (peak frequency) of magnetostrictive vibrations is approximately twice the carrier frequency. Therefore, for example, by setting the carrier frequency to a frequency equal to or higher than half the upper limit frequency of the human audible range (e.g., 20 kHz), the frequency of magnetostrictive vibrations can be made higher than the human audible range. For example, by setting the carrier frequency in the heat generation mode to 10 kHz or higher, the frequency of magnetostrictive vibrations can be made higher than the human audible range. Note that the carrier frequency in the normal mode is set to, for example, 5 kHz.

[0045] 5, when the heat generation mode is selected (step #01: Yes), the control device 1 sets the carrier frequency by referring to the heat generation mode map (carrier frequency map for the heat generation mode) (step #02). When the heat generation mode is not selected (step #01: No), that is, when the normal mode is selected, the control device 1 sets the carrier frequency by referring to the normal mode map (carrier frequency map for the normal mode) (step #03).

[0046] 6 shows an example of a carrier frequency map. Although the carrier frequency can be configured not to change according to the traveling speed of the vehicle 100, in this embodiment, the control device 1 is configured to change the carrier frequency according to the traveling speed of the vehicle 100. Therefore, the carrier frequency map defines the relationship between the carrier frequency and the traveling speed of the vehicle 100, and the control device 1 refers to the carrier frequency map to obtain the carrier frequency according to the traveling speed of the vehicle 100. In this embodiment, the control device 1 is configured to change the carrier frequency according to the traveling speed of the vehicle 100 in both the normal mode and the heat generation mode.

[0047] 6, the first frequency f1 and the second frequency f2 are carrier frequencies set in the normal mode, and the third frequency f3 and the fourth frequency f4 are carrier frequencies set in the heat generation mode. The first frequency f1, the second frequency f2, the third frequency f3, and the fourth frequency f4 are set in advance. The first set vehicle speed V1 and the second set vehicle speed V2 are vehicle speeds (traveling speeds of the vehicle 100) that are set in advance. The first set vehicle speed V1 is set to a value within a range of 30 km / h to 50 km / h, for example. The second set vehicle speed V2 may be set to a value lower than the first set vehicle speed V1, set to the same value as the first set vehicle speed V1, or set to a value higher than the first set vehicle speed V1. In this embodiment, the second set vehicle speed V2 is set to a value higher than the first set vehicle speed V1. The vehicle speed range below the first set vehicle speed V1 is defined as the "low vehicle speed range," the vehicle speed range higher than the first set vehicle speed V1 and below the second set vehicle speed V2 is defined as the "medium vehicle speed range," and the vehicle speed range higher than the second set vehicle speed V2 is defined as the "high vehicle speed range."

[0048] When using the carrier frequency map shown in Figure 6, in normal mode, the carrier frequency is set to the first frequency f1 when the vehicle 100 is traveling at low speed and medium speed ranges, and the carrier frequency is set to the second frequency f2 when the vehicle 100 is traveling at high speed ranges. In the example shown in Figure 6, the second frequency f2 is set to a higher frequency than the first frequency f1. This makes it easier to ensure the controllability of the rotating electric machine 4 at high speed ranges. Furthermore, when using the carrier frequency map shown in Figure 6, in heat generation mode, the carrier frequency is set to the fourth frequency f4 when the vehicle 100 is traveling at low speed and high speed ranges, and the carrier frequency is set to the third frequency f3 when the vehicle 100 is traveling at medium speed ranges.

[0049] In this embodiment, when the heat generation mode is selected, the control device 1 sets the carrier frequency lower when the vehicle speed 100 is higher than the first set vehicle speed V1 compared to when the vehicle speed 100 is less than or equal to the first set vehicle speed V1. Therefore, in the carrier frequency map shown in Figure 6, the third frequency f3 is set to a lower value than the fourth frequency f4. Alternatively, an upper limit may be set for the vehicle speed range in which the carrier frequency is set lower (vehicle speed range higher than the first set vehicle speed V1), so that when the vehicle speed 100 is higher than the first set vehicle speed V1 but less than or equal to the set upper limit vehicle speed, the carrier frequency is set lower compared to when the vehicle speed 100 is less than or equal to the first set vehicle speed V1. In other words, the above-mentioned "when the vehicle speed 100 is higher than the first set vehicle speed V1" includes "when the vehicle speed 100 is higher than the first set vehicle speed V1 but less than or equal to the set upper limit vehicle speed".

[0050] In the carrier frequency map shown in Fig. 6, the second set vehicle speed V2 is the set upper limit vehicle speed. Therefore, when using the carrier frequency map shown in Fig. 6, the carrier frequency is set as follows in the heat generation mode. That is, when the traveling speed of the vehicle 100 is higher than the first set vehicle speed V1 and equal to or lower than the second set vehicle speed V2, the carrier frequency is set lower than when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1. Furthermore, when the traveling speed of the vehicle 100 is higher than the second set vehicle speed V2, the carrier frequency is set to the same value as when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1. Note that it is also possible to configure the carrier frequency to be set higher when the traveling speed of the vehicle 100 is higher than the second set vehicle speed V2 than when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1.

[0051] Noise generated by the rotating electric machine 4, such as noise due to magnetostriction, is likely to cause discomfort to occupants of the vehicle 100 at relatively low vehicle speeds where road noise and wind noise are low. In consideration of this, when the heat generation mode is selected, the control device 1 sets the carrier frequency higher than when the normal mode is selected, at least when the traveling speed of the vehicle 100 is equal to or lower than a set vehicle speed. In the carrier frequency map shown in FIG. 6, the fourth frequency f4 is set to a value higher than the first frequency f1. Therefore, when the carrier frequency map shown in FIG. 6 is used, the first set vehicle speed V1 becomes the set vehicle speed, and the control device 1 sets the carrier frequency higher than when the normal mode is selected, at least when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1.

[0052] In this embodiment, regardless of the traveling speed of the vehicle 100 (i.e., over the entire vehicle speed range), when the heat generation mode is selected, the control device 1 sets the carrier frequency higher than when the normal mode is selected. Specifically, when the traveling speed of the vehicle 100 is higher than the first set vehicle speed V1 and equal to or lower than the second set vehicle speed V2, the control device 1 sets the carrier frequency higher when the heat generation mode is selected than when the normal mode is selected. Furthermore, when the traveling speed of the vehicle 100 is higher than the second set vehicle speed V2, the control device 1 sets the carrier frequency higher than when the normal mode is selected. Therefore, in the carrier frequency map shown in FIG. 6, the third frequency f3 is set to a value higher than the first frequency f1, and the fourth frequency f4 is set to a value higher than the second frequency f2.

[0053] Other Embodiments (1) In the above embodiment, an example has been described in which, when the control device 1 selects the heat generation mode, if the traveling speed of the vehicle 100 is higher than the first set vehicle speed V1, the carrier frequency is set lower than when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1. However, the present disclosure is not limited to such a configuration. The control device 1 may also be configured to, when the control device 1 selects the heat generation mode, if the traveling speed of the vehicle 100 is higher than the first set vehicle speed V1, the carrier frequency is set higher than when the traveling speed of the vehicle 100 is equal to or lower than the first set vehicle speed V1. For example, such a configuration can be achieved by setting the third frequency f3 to a value higher than the fourth frequency f4 in the carrier frequency map shown in FIG. 6. Alternatively, the control device 1 may be configured to set the carrier frequency to the same frequency regardless of the traveling speed of the vehicle 100 when the heat generation mode is selected.

[0054] (2) In the above embodiment, the control device 1 was described as having a configuration in which, when the vehicle 100 is traveling at a speed higher than the second set vehicle speed V2 and the heat generation mode is selected, the carrier frequency is set higher than when the normal mode is selected. However, the present disclosure is not limited to such a configuration, and for example, the control device 1 may be configured to set the same carrier frequency as when the normal mode is selected when the vehicle 100 is traveling at a speed higher than the second set vehicle speed V2 and the heat generation mode is selected.

[0055] (3) The configurations disclosed in each of the embodiments described above can be applied in combination with configurations disclosed in other embodiments (including combinations of embodiments described as other embodiments), as long as no inconsistencies arise. With regard to other configurations, the embodiments disclosed herein are merely illustrative in all respects. Therefore, various modifications can be made as appropriate without departing from the spirit of this disclosure.

[0056] [Summary of this embodiment] The above-described embodiment of the vehicle drive device will be summarized below.

[0057] The vehicle drive device (10) includes: a rotating electric machine (4) having a rotor (41); an inverter (7) that generates AC power to be supplied to the rotating electric machine (4); a control device (1) that controls the rotating electric machine (4) via the inverter (7) by vector control using an orthogonal vector coordinate system having a d-axis along the direction of the magnetic field of the rotor (41) and a q-axis orthogonal to the d-axis; and a drive transmission mechanism (5) that transmits driving force of the rotating electric machine (4) to wheels (W), wherein the control device (1) performs a current determination process that determines a d-axis current (Id) and a q-axis current (Iq) according to a target torque that is a target for output torque of the rotating electric machine (4); The control device (1) is configured to execute a PWM signal generation process for generating a switching signal for PWM control of the inverter (7) based on the q-axis current (Iq), and a carrier frequency determination process for determining a carrier frequency for the PWM control, wherein in the current determination process, the control device (1) selectively executes a normal mode and a heat creation mode, and the heat creation mode is a mode in which the magnitude of a resultant vector (Idq) of the d-axis current (Id) and the q-axis current (Iq) is made larger for the same target torque than in the normal mode, and in the carrier frequency determination process, when the control device (1) selects the heat creation mode, the control device (1) sets the carrier frequency higher than when the control device (1) selects the normal mode.

[0058] According to this configuration, by selecting the heat creation mode, the magnitude of the resultant vector (Idq) can be increased, thereby increasing the loss (amount of loss) in the rotating electric machine (4). Here, when the heat creation mode is selected, the carrier frequency is set higher than when the normal mode is selected, so that noise generated by the rotating electric machine (4), such as noise due to magnetostriction, is likely to be noise with a frequency that is difficult for humans to detect. Therefore, in the heat creation mode, the magnitude of the resultant vector (Idq) can be increased to increase the loss in the rotating electric machine (4) while keeping the level of noise that may cause discomfort to vehicle occupants low, which makes it easy to increase the amount of heat generated in the heat creation mode. Note that in the heat creation mode, setting the carrier frequency higher increases switching loss in the inverter (7), which in turn increases loss in the inverter (7). This configuration also makes it easy to increase the amount of heat generated in the heat creation mode.

[0059] As described above, according to this configuration, when the rotating electric machine (4) is used to generate the heat required for the vehicle (100), it is easy to increase the amount of heat generated while keeping the noise level that may cause discomfort to the occupants of the vehicle (100) low.

[0060] Here, in the carrier frequency determination process, when the control device (1) selects the heat generation mode, it is preferable that the control device (1) sets the carrier frequency so that the frequency of the magnetostrictive vibration generated at the carrier frequency is higher than the human audible range.

[0061] According to this configuration, in the heat generation mode, it is easy to increase the amount of heat generated while keeping the noise level low, which may cause discomfort to the occupants of the vehicle (100).

[0062] In addition, when the heat generation mode is selected, if the traveling speed of the vehicle (100) equipped with the vehicle drive device (10) is higher than a preset first set vehicle speed (V1), the control device (1) preferably sets the carrier frequency lower than when the traveling speed is equal to or lower than the first set vehicle speed (V1).

[0063] When the vehicle (100) is traveling at a relatively high speed, the rotational speed of the rotating electric machine (4) is usually also at a relatively high speed. When the rotational speed of the rotating electric machine (4) is at a relatively high speed, lowering the carrier frequency generally tends to increase iron loss in the rotating electric machine (4). According to this configuration, when the heat generation mode is selected, if the vehicle speed, which is the traveling speed of the vehicle (100), is higher than the first set vehicle speed, the carrier frequency is set lower than when the vehicle speed is equal to or lower than the first set vehicle speed. Therefore, in a vehicle speed range where lowering the carrier frequency tends to increase iron loss in the rotating electric machine (4), the loss in the rotating electric machine (4) is increased, and the amount of heat generated is likely to increase.

[0064] In addition, when the traveling speed of the vehicle (100) equipped with the vehicle drive device (10) is higher than a preset second set vehicle speed (V2), if the heat generation mode is selected, it is preferable that the control device (1) sets the carrier frequency higher than when the normal mode is selected.

[0065] According to this configuration, even when the vehicle (100) is traveling at a relatively high speed, the carrier frequency is increased to increase the switching loss in the inverter (7), and the amount of heat generated in the heat generation mode is likely to increase.

[0066] It is sufficient for the vehicle drive device according to the present disclosure to achieve at least one of the above-described effects. [Explanation of symbols]

[0067] 1: control device, 4: rotating electric machine, 5: drive transmission mechanism, 7: inverter, 10: vehicle drive device, 41: rotor, 100: vehicle, Id: d-axis current, Iq: q-axis current, Idq: resultant vector, V1: first set vehicle speed, V2: second set vehicle speed, W: wheel

Claims

1. A vehicle drive device including: a rotating electric machine having a rotor; an inverter that generates AC power to be supplied to the rotating electric machine; a control device that controls the rotating electric machine via the inverter by vector control using an orthogonal vector coordinate system having a d-axis along the direction of a magnetic field of the rotor and a q-axis orthogonal to the d-axis; and a drive transmission mechanism that transmits a drive force of the rotating electric machine to wheels, The control device a current determination process for determining a d-axis current and a q-axis current according to a target torque that is a target for the output torque of the rotary electric machine; a PWM signal generation process for generating a switching signal for PWM control of the inverter based on the d-axis current and the q-axis current determined by the current determination process; a carrier frequency determination process for determining a carrier frequency for the PWM control; configured to run In the current determination process, the control device selectively executes a normal mode and a heat generation mode, the heat generation mode is a mode in which, compared to the normal mode, a magnitude of a resultant vector of the d-axis current and the q-axis current is increased for the same target torque; In the carrier frequency determination process, when the heat generation mode is selected, the control device sets the carrier frequency higher than when the normal mode is selected.

2. 2. The vehicle drive device according to claim 1, wherein, in the carrier frequency determination process, when the heat generation mode is selected, the control device sets the carrier frequency so that a frequency of magnetostrictive vibration generated at the carrier frequency is higher than the human audible range.

3. 3. The vehicle drive device according to claim 1, wherein when the heat generation mode is selected, if the traveling speed of the vehicle equipped with the vehicle drive device is higher than a predetermined first set vehicle speed, the control device sets the carrier frequency lower than when the traveling speed is equal to or lower than the first set vehicle speed.

4. 3. The vehicle drive device according to claim 1, wherein when the driving speed of a vehicle equipped with the vehicle drive device is higher than a predetermined second set vehicle speed, if the heat generation mode is selected, the control device sets the carrier frequency higher than when the normal mode is selected.

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