Control device for an electric vehicle

Abstract

To effectively utilize a drive motor which can change magnetic force.SOLUTION: A magnetic force change determination part 21c determines whether or not there is performed a magnetization process which changes magnetic force of a magnetic force variable magnet 35 according to operation state of a drive motor 3. The magnetic force change determination part 21c acquires a first electric power P1 which the drive motor 3 consumes or generates without the magnetization process, a second electric power P2 which the drive motor 3 consumes or generates with the magnetization process, and energy loss EL which is generated by the magnetization process. Power gain PG obtained by subtracting the first electric power P1 and the second electric power P2 is compared with the power loss PL obtained by converting the energy loss EL, the magnetization process is determined to be performed when the power gain PG is greater than the power loss PL, and the magnetization process is determined not to be performed when the power gain PG is the power loss PL or less.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The disclosed technology relates to a control device for an electric vehicle capable of traveling using electric power, such as an electric vehicle or a hybrid vehicle.

Background Art

[0002] Patent Document 1 discloses a hybrid vehicle equipped with a permanent magnet synchronous drive motor. In that drive motor, a magnetic force variable magnet capable of variably changing the magnitude of the magnetic force is used for the permanent magnet installed on the rotor.

[0003] The output range of the drive motor is divided into four magnetization regions, and an optimal magnetic force value (optimal magnetic force value) is set for each of these magnetization regions. And when the output of the drive motor shifts between each of these magnetization regions, the magnetic force of the magnetic force variable magnet is configured to be changed to the optimal magnetic force value of the destination.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If the magnetic force of the magnetic force variable magnet is changed according to the output of the drive motor as in the above-described hybrid vehicle, the motor efficiency is improved, so that the energy loss of the drive motor can be reduced. Also, since the output of the drive motor is improved, the distance that can be traveled using electric power is increased.

[0006] However, when changing the magnetic force of the variable magnetic force magnet, it is necessary to apply a large current for magnetization (so-called d-axis current) to the coil of the drive motor. Therefore, changing the magnetic force of the variable magnetic force magnet consumes a large amount of power. Changing the magnetic force of the variable magnetic force magnet generates new energy losses.

[0007] In addition, when a large current for magnetization is applied to the drive motor, it interferes with the drive current (so-called q-axis current), and the torque output from the drive motor fluctuates. When this torque fluctuation is transmitted to the drive wheels, a torque shock occurs in the vehicle during running. On the other hand, for torque fluctuations that increase the torque, if the clutch installed between the drive motor and the drive wheels is slipped, the torque shock can be suppressed.

[0008] However, when the clutch is slipped, the output of the drive motor is wasted accordingly. Suppressing the torque shock generated with the change in the magnetic force of the variable magnetic force magnet also generates new energy losses.

[0009] On the other hand, in the above-described hybrid vehicle, the magnetic force of the variable magnetic force magnet is changed by shifting between each of the four magnetized regions partitioned in advance so that the magnetic force becomes optimal. Therefore, although motor efficiency is considered, such energy losses are not sufficiently considered. Torque shock is not considered either. Also, although the drive motor is used as a generator during regeneration, that is not sufficiently considered either. Therefore, there is room for improvement.

[0010] The disclosed technology realizes an electric vehicle that can run more efficiently by effectively using a drive motor whose magnetic force can be changed.

Means for Solving the Problem

[0011] The disclosed technology relates to a control device for an electric vehicle capable of traveling using electric power, which is provided with a drive motor in which the rotor poles are constituted by a variable magnetic force magnet whose magnetic force can be changed.

[0012] The control device includes a magnetization processing unit that performs a magnetization process for changing the magnetic force of the magnetically variable magnet, and a magnetic force change determination unit that determines whether to perform the magnetization process according to the operating state of the drive motor.

[0013] Then, the magnetic force change determination unit acquires each of a first power consumed or generated by the drive motor when the magnetization process is not performed, a second power consumed or generated by the drive motor when the magnetization process is performed, and an energy loss generated by performing the magnetization process.

[0014] Then, a magnitude relationship is compared between a power gain obtained by subtracting the first power and the second power, and a power loss obtained by converting the energy loss. When the power gain is greater than the power loss, it is determined to perform the magnetization process. When the power gain is less than or equal to the power loss, it is determined not to perform the magnetization process.

[0015] That is, this control device targets electric vehicles such as electric cars and hybrid cars that can run using electric power, and the rotor poles of the equipped drive motor are composed of magnetically variable magnets whose magnetic force can be changed.

[0016] And the control device is provided with a magnetization processing unit. By performing the magnetization process by the magnetization processing unit, the magnetic force of the magnetically variable magnet is changed. Thereby, the drive motor can change the magnetic force of the rotor, so that the motor efficiency can be improved.

[0017] Furthermore, the control device is also provided with a magnetic force change determination unit. By performing magnetic force change determination with the magnetic force change determination unit, it is determined whether to perform magnetization processing according to the operating state of the drive motor. For example, when the operating state of the drive motor changes, the magnetic force change determination unit obtains a predetermined power gain and power loss based on a first power and a second power that the drive motor consumes during power running or generates during regeneration, and the energy loss generated by performing magnetization processing, in the cases of performing magnetization processing and not performing magnetization processing. Then, by comparing these magnitude relationships, it is determined whether to perform magnetization processing or not.

[0018] That is, the magnetic force change determination unit determines which case is appropriate from the perspective of energy gain and loss, in the cases of performing magnetization processing and not performing magnetization processing, according to the operating state of the drive motor. By considering the positive and negative elements regarding the energy gain and loss generated with the change of the magnetic force of the magnet with variable magnetic force, it is determined whether to perform magnetization processing or not, so that energy loss can be suppressed. Since the performance of the drive motor whose magnetic force can be changed can be effectively utilized, an electric vehicle that can run more efficiently, such as an improvement in fuel efficiency, can be realized.

[0019] The control device may also include a first energy loss consumed for changing the magnetic force of the magnet with variable magnetic force and a second energy loss generated for reducing torque fluctuations output from the drive motor during magnetization processing.

[0020] As described above, changing the magnetic force of the magnet with variable magnetic force consumes a large amount of power. In this control device, this energy loss is considered as the first energy loss. Furthermore, when changing the magnetic force of the magnet with variable magnetic force, torque fluctuations that can give torque shock are output from the drive motor. Energy loss is generated to reduce the torque fluctuations. In this control device, this energy loss is considered as the second energy loss.

[0021] That is, according to this control device, since the main energy loss generated with the change in the magnetic force of the magnet with variable magnetic force is considered, the magnetic force change determination can be performed with high accuracy.

[0022] The control device may also be configured such that when the magnetic force change determination unit compares the magnitude relationship between the power gain and the power loss, a predetermined weighting factor is multiplied by the power gain to compare the magnitude relationship with the power loss.

[0023] There are various external factors that affect the determination of energy gain and loss. For example, among electric vehicles, there are vehicle models that can switch driving modes such as a sports mode and an eco mode. In the case of such vehicle models, the driving mode affects the energy gain and loss. The eco mode has a higher importance for energy gain and loss than the sports mode.

[0024] Therefore, when comparing the magnitude relationship between the power gain and the power loss, by multiplying the power gain by a predetermined weighting factor to compare the magnitude relationship with the power loss, the magnetic force change determination can be performed considering such external factors. The convenience of the electric vehicle is improved.

[0025] When the electric vehicle is further configured to be able to run using fuel by including an engine, that is, when it is a hybrid vehicle, when performing the magnetic force change determination when the electric vehicle is regenerating, a larger value of the weighting factor may be used than when performing the magnetic force change determination when the electric vehicle is powering.

[0026] When the electric vehicle is a hybrid vehicle, it has been found that the effect of improving the motor efficiency obtained by changing the magnetic force of the magnet with variable magnetic force is greater when regenerating than when powering. Therefore, in this control device, by using a larger value of the weighting factor during regeneration than during powering, the motor efficiency can be further improved. Thereby, the energy loss can be further suppressed, and the fuel consumption of the electric vehicle can be effectively suppressed.

[0027] The control device also further includes a battery that supplies power input to the drive motor and stores the power generated by the drive motor, and when performing the magnetic force change determination when the remaining battery level of the battery is in a low charge state less than a predetermined threshold value, a larger value of the weight coefficient may be used than when performing the magnetic force change determination when the remaining battery level of the battery is in a high charge state equal to or higher than the threshold value.

[0028] In the case of this control device, the drive motor is driven by the power input from the battery. Therefore, when the remaining battery level of the battery decreases, the operation of the drive motor is restricted. Therefore, when the remaining battery level of the battery is low (low charge state), the power of the battery is more precious than when the remaining battery level of the battery is high (high charge state). Therefore, in this control device, by using a larger value of the weight coefficient in the low charge state than in the high charge state, the power consumption of the battery can be suppressed. Thereby, the drive motor together with the battery can be used more effectively.

Effects of the Invention

[0029] According to the disclosed technology, a drive motor capable of changing the magnetic force can be used more effectively. As a result, the electric vehicle can run more efficiently.

Brief Description of the Drawings

[0030]

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Mode for Carrying Out the Invention

[0031] Hereinafter, the disclosed technology will be described. However, the following description is merely illustrative in nature.

[0032] <Electric Vehicle> Fig. 1 shows an automobile 1 (an example of an electric vehicle) to which the disclosed technology is applied. This automobile 1 is a hybrid vehicle capable of running using fuel, running using electricity, and running by combining these. An engine 2 and a drive motor 3 are mounted on the drive source of the automobile 1. These cooperate to drive two wheels (drive wheels 4R) that are symmetrically located among the four wheels 4F, 4F, 4R, 4R. Thereby, the automobile 1 runs. Note that the automobile 1 may be an electric vehicle equipped with only the drive motor 3. The automobile 1 may also be four-wheel drive.

[0033] In the case of this automobile 1, the engine 2 is arranged on the front side of the vehicle body, and the drive wheels 4R are arranged on the rear side of the vehicle body. That is, this automobile 1 is a so-called FR vehicle. Further, in the case of this automobile 1, as the drive source, the engine 2 is the main one rather than the drive motor 3, and the drive motor 3 is used in a form that assists the drive of the engine 2 (so-called mild hybrid). The drive motor 3 is also used not only as a drive source but also as a generator when the automobile 1 regenerates.

[0034] In addition to the engine 2 and the drive motor 3, the automobile 1 is equipped with, as devices of the drive system, a first relay clutch 5, an inverter 6, a second relay clutch 7, a transmission 8, a differential gear 9, a battery 10, and the like. The automobile 1 is also equipped with, as devices of the control system, an engine control unit (ECU) 20, a motor control unit (MCU) 21, a transmission control unit (TCU) 22, a brake control unit (BCU) 23, a comprehensive control unit (GCU) 24, and the like.

[0035] An engine rotation sensor 50, a motor rotation sensor 51, a current sensor 52, a magnetic force sensor 53, an accelerator sensor 54, a transmission sensor 55, etc. are also installed in the automobile 1 along with the devices of the control system. The engine rotation sensor 50 is attached to the engine 2, detects the rotational speed of the engine 2, and outputs it to the ECU 20.

[0036] The motor rotation sensor 51 is attached to the drive motor 3, detects the rotational speed and rotational position of the drive motor 3, and outputs them to the MCU 21. The current sensor 52 is attached to the connection cable 36a, detects the current value supplied to each coil 36, and outputs it to the MCU 21. The magnetic force sensor 53 is attached to the drive motor 3, detects the magnetic force of the magnetically variable magnet 35, and outputs it to the MCU 21.

[0037] The accelerator sensor 54 is attached to the accelerator pedal (accelerator pedal 15) that the driver depresses when driving the vehicle 1, and detects the accelerator opening corresponding to the output required for driving the vehicle 1 and outputs it to the ECU 20. The transmission sensor 55 detects the rotational speed and engagement torque of each transmission clutch 83, the rotational speed of the output shaft 81, etc. and outputs them to the TCU 22.

[0038] (Device of the drive system) The engine 2 is an internal combustion engine that burns using, for example, gasoline as fuel. The engine 2 is also a so-called four-cycle engine that generates rotational power by repeating each cycle of intake, compression, expansion, and exhaust. There are various types and forms of engines 2, such as diesel engines, but in the disclosed technology, the type and form of the engine are not particularly limited.

[0039] In this vehicle 1, the engine 2 is arranged at substantially the center in the vehicle width direction with the output shaft for outputting rotational power facing in the longitudinal direction of the vehicle body. Various devices and mechanisms associated with the engine 2, such as an intake system, an exhaust system, and a fuel supply system, are installed in the vehicle 1, but illustration and description of these are omitted.

[0040] The drive motor 3 is arranged in series behind the engine 2 via the first relay clutch 5. The drive motor 3 is a permanent magnet type synchronous motor driven by three-phase alternating current. As shown schematically in FIG. 2, the drive motor 3 is generally composed of a motor case 31, a shaft 32, a rotor 33, a stator 34, etc.

[0041] The motor case 31 is a container having a cylindrical space with its front end face and rear end face sealed inside, and is fixed to the vehicle body of the vehicle 1. The rotor 33 and the stator 34 are housed in the motor case 31. The shaft 32 is rotatably supported by the motor case 31 with each of its front end portion and rear end portion protruding from the motor case 31.

[0042] A first relay clutch 5 is installed so as to be interposed between the front end portion of the shaft 32 and the output shaft of the engine 2. The first relay clutch 5 is configured to be switchable between a state where the output shaft and the shaft 32 are connected (engaged state) and a state where the output shaft and the shaft 32 are separated (non-engaged state).

[0043] A second relay clutch 7 is installed so as to be interposed between the rear end portion of the shaft 32 and the input shaft of the transmission 8. The second relay clutch 7 is configured to be switchable between a state where the shaft 32 and the input shaft of the transmission 8 are connected (engaged state) and a state where the shaft 32 and the input shaft of the transmission 8 are separated (non-engaged state).

[0044] The rotor 33 is composed of a columnar member formed by laminating a plurality of metal plates having a shaft hole at the center. By fixing the intermediate portion of the shaft 32 to the shaft hole of the rotor 33, the rotor 33 is integrated with the shaft 32.

[0045] Magnets 35 are installed over the entire outer peripheral portion of the rotor 33. The magnets 35 are configured such that different magnetic poles in the circumferential direction, that is, S poles and N poles, are arranged alternately at equal intervals. The magnet 35 may be composed of a single cylindrical magnet having a plurality of magnetic poles, or may be composed of a plurality of arc-shaped magnets constituting each magnetic pole.

[0046] In this drive motor 3, further, the magnet 35 is configured such that the magnitude of the magnetic force can be variably increased or decreased (magnetic force variable magnet 35). Usually, for this type of drive motor 3, a magnet (permanent magnet) having a large coercive force (demagnetizing force) and capable of holding the magnetic force over a long period is used. In this drive motor 3, a permanent magnet having a small holding force is used as the magnetic force variable magnet 35 so that the magnetic force can be changed relatively easily. The type and material of the magnetic force variable magnet 35 can be selected according to the specifications and are not particularly limited.

[0047] A cylindrical stator 34 is installed around the rotor 33 with a slight gap (gap) (inner rotor type). The stator 34 has a stator core 34a composed of a plurality of laminated metal plates and a plurality of coils 36 formed by winding electric wires around the stator core 34a.

[0048] The stator core 34a is provided with a plurality of teeth 34b that radially project inward. By winding electric wires around these teeth 34b in a predetermined order, a plurality of coils 36 are formed. These coils 36 constitute a three-phase coil group consisting of a U-phase, a V-phase, and a W-phase. To energize these coils 36, connection cables 36a are led out from each of the coil groups of each phase to the outside of the motor case 31.

[0049] These connection cables 36a are connected to a battery 10 mounted as a drive power source via an inverter 6. In the case of this automobile 1, a DC battery with a rated voltage of 50 V or less, specifically 48 V, is used as the battery 10.

[0050] When the automobile 1 travels using the drive of the drive motor 3 (during power running), the battery 10 supplies DC power to the inverter 6. The inverter 6 converts this DC power into three-phase alternating current and energizes the drive motor 3. Thereby, the rotor 33 is rotationally driven, and the power (rotational power) of the drive motor 3 is output to the transmission 8 via the shaft 32 and the second relay clutch 7.

[0051] The battery 10 also stores the power generated by the drive motor 3 when the automobile 1 uses the drive motor 3 as a generator (during regeneration). Note that "power running" may include the case when the automobile 1 travels without using the drive of the drive motor 3. However, as described above, the power running in this embodiment does not include the case when the automobile 1 travels only by the drive of the engine 2.

[0052] In the case of this vehicle 1, the transmission 8 is a multi-stage automatic transmission (so-called AT). As shown in FIG. 1, the transmission 8 has an input shaft 80 at one end thereof, and the input shaft 80 is connected to the second intermediate clutch 7. At the other end of the transmission 8, there is an output shaft 81 that rotates independently of the input shaft 80. Between these input shaft 80 and output shaft 81, a transmission mechanism composed of a plurality of planetary gear mechanisms 82 and a plurality of transmission clutches 83 (including brakes) is incorporated.

[0053] By switching these transmission mechanisms, it is configured to be able to switch between forward and reverse, and to change the rotational speed between the input shaft 80 and the output shaft 81 of the transmission 8, that is, to switch the gear ratio.

[0054] For example, the input side 83a of each transmission clutch 83 is configured to be connectable to the input shaft 80. The output side 83b of each transmission clutch 83 is connected to the output shaft 81 via the corresponding planetary gear mechanism 82. And when a specific transmission clutch 83 is selected and that transmission clutch 83 is engaged, the input shaft 80 and the output shaft 81 of the transmission are connected via that transmission clutch 83 and the corresponding planetary gear mechanism 82. Thereby, the gear ratio and the like are switched.

[0055] The output shaft 81 is connected to the differential gear 9 via a propeller shaft 11 that extends in the longitudinal direction of the vehicle body and is arranged coaxially with the output shaft 81. To the differential gear 9, a pair of drive shafts 13, 13 that extend in the vehicle width direction and are connected to the left and right drive wheels 4R, 4R are connected. The rotational power output through the propeller shaft 11 is distributed by the differential gear 9 and then transmitted to each drive wheel 4R through these pair of drive shafts 13, 13. To each wheel 4F, 4F, 4R, 4R, a brake 14 is attached to brake its rotation.

[0056] (Device of the control system) In the motor vehicle 1, in order to control its running according to the driver's operations, the above-described units of the ECU 20, MCU 21, TCU 22, BCU 23, and GCU 24 are installed. Each of these units is composed of hardware such as a processor, a memory, and an interface, and software such as a database and a control program.

[0057] The ECU 20 is a unit that mainly controls the operation of the engine 2. The MCU 21 is a unit that mainly controls the operation of the drive motor 3. The TCU 22 is a unit that mainly controls the operation of the transmission 8. The BCU 23 is a unit that mainly controls the operation of the brake 14. The GCU 24 is a higher-level unit that is electrically connected to these ECU 20, MCU 21, TCU 22, and BCU 23 and comprehensively controls them.

[0058] The "control device" in the disclosed technology is composed of these units. In particular, the MCU 21 that mainly controls the operation of the drive motor 3 and the TCU 22 that mainly controls the operation of the transmission 8 constitute the main body of the control device. By the cooperation of these units, various processes described later are executed.

[0059] FIG. 3 shows the MCU 21 and the main input / output devices related thereto. In the MCU 21, as a functional configuration, a motor output control unit 21a, a magnetization processing unit 21b, and a magnetic force change determination unit 21c are provided by its hardware and software. The motor output control unit 21a has a function of controlling the drive of the drive motor 3, and outputs the power required for the drive motor 3 by controlling the drive current flowing through the coil 36.

[0060] The magnetization processing unit 21b has a function of increasing the power factor of the drive motor 3, and performs a process (magnetization process) of changing the magnetic force of the magnetically variable magnet 35 by controlling the magnetization current flowing through the coil 36. The magnetization current is a pulsed current that generates an electromagnetic force greater than the coercive force of the magnetically variable magnet 35. Due to the magnetization process, the magnetic field between the rotor 33 and the stator 34 changes. Thereby, the magnitude of the magnetic force of the magnetically variable magnet 35 is changed.

[0061] The magnetic force change determination unit 21c has a function of determining the execution and timing of the magnetic force change from the perspective of energy gain and loss, and performs a determination (magnetic force change determination) on whether to perform the magnetization process according to the operating state of the drive motor. For example, when losses occur in the energy balance associated with the change in magnetic force, the magnetization process is not performed. Therefore, the efficiency of the entire system for driving the drive motor 3 can be improved (the magnetic force change determination unit 21c, details of the magnetic force change determination will be described later).

[0062] Fig. 4 shows the TCU 22 and the main input / output devices related thereto. In the TCU 22, a relay clutch control unit 22a and a transmission clutch control unit 22b are provided by its hardware and software as functional configurations. The relay clutch control unit 22a controls the operation of each of the first relay clutch 5 and the second relay clutch 7. The transmission clutch control unit 22b controls the operation of each of the transmission clutches 83.

[0063] For example, when the vehicle 1 travels by the driving force of the engine 2, the ECU 20 controls the operation of the engine 2 based on the detection values of the accelerator sensor 54 and the engine rotation sensor 50. Then, the TCU 22 controls the first relay clutch 5 and the second relay clutch 7 to be in the engaged state.

[0064] During regeneration when power is generated by the drive motor 3, the TCU 22 controls the first relay clutch 5 to be in a non-engaged state or a partially engaged state, and controls the second relay clutch 7 to be in an engaged state. Thereby, the electric power generated by the drive motor 3 is stored in the battery 10.

[0065] <Operation of Drive Motor> The MCU 21 controls the vehicle 1 to travel using the power output by the drive motor 3 in a state where the output of the engine 2 is assisted as necessary.

[0066] Specifically, based on the detection values of the accelerator sensor 54, the engine rotation sensor 50, etc., the ECU 20 sets the torque output by the engine 2. Accordingly, the GCU 24 sets the required torque amount (required torque) for the drive motor 3 according to a preset output distribution ratio between the engine 2 and the drive motor 3. The MCU 21 controls the drive motor 3 so that the required torque is output (so-called torque control). Thereby, the drive motor 3 operates while assisting the engine 2 in a predetermined operation region during the travel of the vehicle 1.

[0067] (Operation Region of Drive Motor) FIG. 5 illustrates the operation region of the drive motor 3. The operation region of the drive motor 3 is defined by the rotational speed and torque (load), which are the operation state amounts of the drive motor 3. And in this drive motor 3, this operation region is divided into four magnetization regions Rm1 to Rm4 of the first to fourth, which serve as the reference for changing the magnetic force of the magnetically variable magnet 35. Predetermined magnetic force values (magnetic force reference values) of different values are set in each of these magnetization regions Rm1 to Rm4 so as to improve the power factor.

[0068] Data such as maps and tables that define such an operation region are preset in the MCU 21. The motor output control unit 21a controls the drive motor 3 within the range of this operation region by referring to the data. Thereby, the vehicle 1 travels (so-called power running). Also, during regeneration of the vehicle 1, the drive motor 3 generates electricity within the range of this operation region.

[0069] During the running of the vehicle 1, the magnetic force change determination unit 21c determines whether to change the magnetic force from the perspective of energy gain and loss according to the operating state of the drive motor 3. And when the magnetic force change determination unit 21c determines not to change the magnetic force, the magnetization processing unit 21b does not perform magnetization processing at that timing. The drive motor 3 changes its operating state according to normal torque control.

[0070] On the other hand, when the magnetic force change determination unit 21c determines to change the magnetic force, the torque control is interrupted. And the magnetization processing unit 21b performs magnetization processing.

[0071] (Magnetization processing and clutch slip associated therewith) When magnetization processing is performed during the running of the vehicle 1, torque fluctuations occur, and a torque shock may be generated in the running vehicle 1. When a torque shock occurs, there is a concern that the driver may feel discomfort.

[0072] The upper diagram of FIG. 6 illustrates the change over time of the torque Tm output by the drive motor 3 during magnetization processing. In this illustration, magnetization processing is being executed during the period from time t1 to t1'. The period from t1' to t2 is a period in which the change in magnetic force is confirmed and control (learning control) is executed to learn the drive current value (the value of the q-axis current) so as to correspond to the changed magnetic force, and the motor torque Tm is made to match the required torque. The learning control is a control associated with flux increasing control and is included in the flux increasing control. Ta is the required torque. Since the drive motor 3 is torque-controlled during the running of the vehicle 1, the motor torque Tm before the execution of magnetization processing matches the required torque Ta.

[0073] Tt is the clutch engagement torque in the transmission 8. The clutch engagement torque Tt is the engagement torque of the transmission clutch 83 that connects the input shaft 80 and the output shaft 81 of the transmission 8, and corresponds to the torque that the transmission clutch 83 can transmit to its output side 83b. In order to reliably transmit the motor torque Tm to the drive wheels, usually, the clutch engagement torque Tt is controlled (first clutch control) to be higher than the required torque Ta.

[0074] In the magnetization process, as described above, a pulsed large magnetization current (so-called d-axis current) is passed through the coil 36. As a result, a high voltage far exceeding the drive voltage is applied to the drive motor 3. Therefore, as shown in the upper diagram of FIG. 6, during the magnetization process, a peak-shaped high motor torque Tm far exceeding the required torque Ta is output from the drive motor 3. As a result, a torque shock is generated in the running automobile 1, and there is a concern that it may give the driver a sense of discomfort.

[0075] Therefore, in order to suppress such torque fluctuations, in this automobile 1, the MCU 21 cooperates with the TCU 22 to slip the transmission clutch 83 during the magnetization process. When the transmission clutch control unit 22b acquires information regarding the execution of the magnetization process from the GCU 24, it controls the operation of the used transmission clutch 83 accordingly to slip it.

[0076] Specifically, as shown in the lower diagram of FIG. 6, the transmission clutch control unit 22b changes from the first clutch control to the second clutch control before the execution of the magnetization process (time t0), and controls the clutch engagement torque Tt to match the required torque Ta until the magnetization process is completed. Thereby, during the magnetization process, the clutch engagement torque Tt is reduced and the transmission clutch 83 is slipped. As a result, even if a high motor torque Tm is output from the drive motor 3, it is transmitted to the transmission clutch 83 in a reduced state. Therefore, torque shock can be suppressed.

[0077] <Magnetic force change determination of drive motor> During the operation of the drive motor 3, when shifting between each of the magnetization regions Rm1 to Rm4, if the magnetic force of the magnetically variable magnet 35 is changed to the magnetic force reference value of the destination, the power factor of the drive motor 3 can be increased. Therefore, the motor efficiency is improved. If the motor efficiency is improved, the energy loss of the drive motor 3 can be reduced. Also, since the output of the drive motor 3 is improved, the distance that the automobile 1 can travel using electric power is also increased.

[0078] On the other hand, when changing the magnetic force of the magnetically variable magnet 35, it is necessary to apply a high voltage for magnetization by passing a large current through the coil 36. Therefore, when changing the magnetic force of the magnetically variable magnet 35, a large amount of power is consumed. Accordingly, new energy losses occur, which do not occur during the operation of the normal drive motor 3.

[0079] Also, as described above, when performing the second clutch control to suppress torque fluctuations, the rotational power of the drive motor 3 is consumed due to the slip of the transmission clutch 83, so that the output of the drive motor 3 is wasted accordingly. New energy losses also occur due to the slip of the transmission clutch 83.

[0080] That is, from the perspective of energy gain and loss, there are positive and negative factors in changing the magnetic force of the magnetically variable magnet 35. Therefore, unless these factors are considered and the execution and timing of the magnetic force change are determined, there is a risk of ultimately generating energy loss even if the magnetic force is changed.

[0081] For example, assume a state where the drive motor 3 is operating (power running) at the operating point P2 shown in FIG. 5. Suppose the operating state of the drive motor 3 changes from the operating point P2 to the operating point P1. In this case, since it shifts from the magnetization region Rm2 to the magnetization region Rm1, based on the viewpoint of improving the power factor of the drive motor 3, it is necessary to perform magnetization processing in the direction of increasing the magnetic field.

[0082] When performing magnetization processing in the direction of increasing the magnetic field, torque fluctuations occur due to the high motor torque Tm. In order to suppress the torque fluctuations, energy losses occur by slipping the transmission clutch 83.

[0083] The same applies to the case of performing magnetization processing in the direction of decreasing the magnetic field. When the operating state of the drive motor 3 changes from the operating point P2 to the operating point P3, since it shifts from the magnetization region Rm2 to the magnetization region Rm3, it is necessary to perform magnetization processing in the direction of decreasing the magnetic field. Even when performing magnetization processing in the direction of decreasing the magnetic field, torque fluctuations occur due to the low motor torque Tm.

[0084] To suppress such torque fluctuations, new energy losses occur. The higher the torque when shifting regions, the greater the torque fluctuations. And the greater the torque fluctuations, the greater the energy losses required to suppress them.

[0085] Thus, when the operating state of drive motor 3 changes and it shifts to different magnetization regions Rm, if the execution and timing of magnetic force change are not determined according to the change in the operating state, even if the magnetic force change is performed, there is a risk of ultimately generating energy losses.

[0086] Therefore, in this control device, when performing magnetization processing, a magnetic force change determination unit 21c is provided in the TCU 22 so that no losses occur in the energy balance due to the magnetization processing.

[0087] (Magnetic force change determination unit 21c) Fig. 7 shows a block diagram representing the main configuration of the magnetic force change determination unit 21c. The magnetic force change determination unit 21c is provided with four maps related to the gain and loss of energy generated during magnetization processing (the first to fourth maps). Note that these maps may be models, tables, logics, arithmetic expressions, etc. having equivalent functions.

[0088] The first map has a function of enabling the output of the electric power (first electric power) consumed or generated by drive motor 3 when no magnetization processing is performed on drive motor 3 operating at that operating state amount by inputting the operating state amount (rotation speed, torque, etc.) of drive motor 3. The second map has a function of enabling the output of the electric power (second electric power) consumed or generated by drive motor 3 when magnetization processing is performed on drive motor 3 operating at that operating state amount by inputting the operating state amount of drive motor 3.

[0089] The third map has a function that enables the output of the weighting factor α for the energy balance of the first power and the second power by inputting the operating state quantity of the drive motor 3 and a predetermined external factor. The external factor is an element for determining the change in magnetic force different from the operating state quantity of the drive motor 3, and is an element that affects the determination of energy gain and loss.

[0090] As an example of such an external factor, the driving mode of the automobile 1 can be cited. For example, there may be a case where the automobile 1 is equipped with a driving mode that can switch the driving performance of the automobile 1, such as a sports mode that prioritizes drivability over fuel efficiency, and an eco mode that prioritizes fuel efficiency over drivability. When the automobile 1 is equipped with such a driving mode, the driving mode affects the determination of energy gain and loss. The eco mode has a higher importance for energy gain and loss than the sports mode.

[0091] Also, as another external factor, the driving state (power running or regeneration) of the automobile 1, the state of charge of the battery, etc. can be cited. These will be described later as application examples.

[0092] The fourth map has a function that enables the output of the energy loss generated by performing magnetization processing on the drive motor 3 operating with the operating state quantity by inputting the operating state quantity of the drive motor 3.

[0093] Then, the magnetic force change determination unit 21c calculates the energy balance by magnetization processing from the energy gain and the energy loss output by inputting the operating state quantity of the drive motor 3 and the external factor into these first to fourth maps, and performs magnetic force change determination based on this.

[0094] FIG. 8 shows the flow of the specific magnetic force change determination process performed by the magnetic force change determination unit 21c. The magnetic force change determination unit 21c determines an operating point to be the subject of magnetic force change determination based on the operating state quantities (such as rotational speed and torque) of the drive motor 3 (step S1). When the operating point is determined, the magnetic force change determination unit 21c performs, in parallel, each of the calculation process C1 regarding the energy gain (power gain) generated when magnetization processing is performed at that operating point, and the calculation process C2 regarding the energy loss (power loss). Note that performing these calculation processes C1 and C2 in parallel is effective for shortening the processing time, but is not essential.

[0095] In the calculation process C1 regarding the energy gain, the magnetic force change determination unit 21c calculates the motor power (first power P1) when magnetization processing is not performed and the motor power (second power P2) when magnetization processing is performed, using the first map and the second map (steps S2, S3). Each of these first power P1 and second power P2 is the power consumed or generated by the drive motor 3 when the drive motor 3 is operated at the operating point that is the subject of magnetic force change determination.

[0096] The power consumed by the drive motor 3 is the power that is input to the drive motor 3 and converted into rotational power during power running. The power generated by the drive motor 3 is the power obtained by converting the rotational power input to the drive motor 3 into electricity during regeneration. In this calculation, the power consumed by the drive motor 3 is treated as a positive value (P1, P2 > 0), and the power generated by the drive motor 3 is treated as a negative value (P1, P2 < 0).

[0097] When the magnetic force change determination unit 21c calculates the first power P1 and the second power P2, it subtracts these first power and second power to calculate the power gain PG (step S4). Specifically, the second power is subtracted from the first power to calculate the power gain PG.

[0098] On the other hand, in the calculation process C2 regarding energy loss, the magnetic force change determination unit 21c uses the fourth map to calculate the energy loss (first energy loss) consumed to change the magnetic force of the magnetically variable magnet 35, and the energy loss (second energy loss) generated to reduce the torque fluctuation caused by the high torque output from the drive motor 3 during the magnetization process (steps S5, S6).

[0099] The first energy loss is the electrical energy Ec output during the magnetization process, that is, the energy required for the energization of the magnetization current. The second energy loss is the energy Et lost due to the slip of the transmission clutch 83 described above. In this calculation, these energies Ec and Et are treated as positive values (Ec, Et > 0).

[0100] The magnetic force change determination unit 21c adds these first energy loss and second energy loss to calculate the energy loss EL (step S7). The magnetic force change determination unit 21c obtains the power loss PL by converting this energy loss EL into a power equivalent value comparable to the power gain PG (step S8).

[0101] Then, the magnetic force change determination unit 21c compares the magnitude relationship between the obtained power gain PG and the power loss PL. Specifically, the magnetic force change determination unit 21c subtracts the power loss PL from the power gain PG to obtain the power balance value PB of the power (step S9). Then, it is determined whether this balance value PB is greater than 0 (step S10). When obtaining the balance value PB, the magnetic force change determination unit 21c performs a process of multiplying the power gain PG by a predetermined weighting factor α (weighting process) by using the third map as necessary.

[0102] Normally, when there is no difference in importance regarding energy gain and loss, the weighting factor α is set to 1. On the other hand, as described above, when the automobile 1 is equipped with a driving mode or the like and there is a difference in importance regarding energy gain and loss, the weighting factor α corresponding to the content is appropriately selected and used for the weighting process.

[0103] As a result of comparing the magnitude relationship between the power gain PG and the power loss PL, when the power gain PG is greater than the power loss PL (balance value PB > 0), the magnetic force change determination unit 21c determines that magnetization processing is to be performed (step S11). On the other hand, when the power gain PG is less than or equal to the power loss PL (balance value PB ≤ 0), the magnetic force change determination unit 21c determines that magnetization processing is not to be performed (step S12).

[0104] Thus, in the control device of this vehicle 1, during the operation of the drive motor 3, when shifting between each of the preset magnetization regions Rm1 to Rm4, the execution and timing of the magnetization processing are determined in consideration of not only the magnetization processing uniformly but also the gain and loss of energy generated by the magnetization processing. Thereby, the generation of energy loss can be suppressed, so that the drive motor 3 can be used more effectively. As a result, the vehicle 1 can run more efficiently.

[0105] <Application Example 1> In the control device of Application Example 1, the criteria for determining magnetic force change are changed during power running (state where the drive motor 3 consumes power and drives) and regeneration (state where the drive motor 3 generates electricity) of the vehicle 1, respectively. Application Example 1 is based on the finding that the gain and loss of energy are different even when the operating state of the drive motor 3 is the same between the case of consuming power and the case of generating power.

[0106] Fig. 9 shows a simplified graph comparing the motor efficiency (average value) obtained during power running and regeneration of the vehicle 1 with respect to the presence or absence of magnetic force change. In both power running and regeneration, the improvement effect of the motor efficiency is recognized more when there is a magnetic force change than when there is no magnetic force change. However, the improvement effect ΔME of the motor efficiency is greater during regeneration than during power running.

[0107] Power running is an operating state in which the drive motor 3 outputs power in cooperation with the engine 2, and the degree of freedom of the operating point of the drive motor 3 is relatively high. On the other hand, regeneration is an operating state in which the drive motor 3 decelerates in cooperation with the brakes when the vehicle 1 brakes, and the degree of freedom of the operating point of the drive motor 3 is relatively low. Therefore, during regeneration, the motor efficiency tends to be worse than during power running.

[0108] On the other hand, when the magnetic force is changed, an effect of expanding the region with high motor efficiency can be obtained. Due to this effect, during regeneration with low motor efficiency, the influence received by the magnetic force change is greater than during power running with high motor efficiency, so the effect of improving the motor efficiency becomes greater. Therefore, in the magnetic force change determination unit 21c of this Application Example 1, when performing magnetic force change determination during regeneration, it is configured to use a weighting coefficient α with a larger value than when performing magnetic force change determination during power running.

[0109] Fig. 10 shows the flow of the specific magnetic force change determination process performed by the magnetic force change determination unit 21c of Application Example 1. The basic process flow is the same as that of the above-described embodiment (see Fig. 8). The same reference numerals are used for the processes with the same content, and the description thereof is omitted or simplified.

[0110] When the magnetic force change determination unit 21c determines the operating point to be the object of magnetic force change determination (step S1), together with the calculation process C1 regarding the power gain PG and the calculation process C2 regarding the power loss PL at that operating point, it also performs in parallel the determination process as to whether the operating state of the vehicle 1 is power running or regeneration (step S31). Note that performing these calculation processes C1, C2 and the determination process in parallel is effective for shortening the processing time, but is not essential.

[0111] When the magnetic force change determination unit 21c determines that the vehicle 1 is in power running, it adopts a predetermined weighting coefficient αA as the weighting coefficient α (step S32). On the other hand, when the magnetic force change determination unit 21c determines that the vehicle 1 is in regeneration, it adopts a predetermined weighting coefficient αB as the weighting coefficient α (step S33). These weighting coefficients αA, αB are both set based on the third map.

[0112] As described above, the improvement effect ΔME of the motor efficiency obtained by changing the magnetic force of the variable magnetic force magnet 35 is greater during regeneration than during power running. Accordingly, the weight coefficient αB for regeneration is usually set to be greater than 1 and greater than the weight coefficient αA for power running (αB > 1, αB > αA). By doing so, a further improvement effect of the motor efficiency can be expected, energy loss can be suppressed, and the fuel consumption of the vehicle 1 can be effectively suppressed.

[0113] The magnetic force change determination unit 21c performs a weighting process on the power gain PG using the weight coefficient α set based on such determination processing, and then subtracts the power loss PL from the power gain PG to obtain a power balance value (step S9). Then, it is determined whether or not this balance value is greater than 0 (step S10). Thus, when the power gain PG is greater than the power loss PL (balance value PB > 0), the magnetic force change determination unit 21c determines that magnetization processing is to be performed (step S11). On the other hand, when the power gain PG is less than or equal to the power loss PL (balance value PB ≤ 0), the magnetic force change determination unit 21c determines that magnetization processing is not to be performed (step S12).

[0114] <Application Example 2> In the control device of Application Example 2, the criterion for magnetic force change determination is changed according to the state of charge (SOC) of the battery 10. Note that the SOC is an index representing the remaining battery level. The SOC is a percentage value with a fully charged state being 100%.

[0115] The drive motor 3 is driven by the power input from the battery 10. Therefore, when the remaining battery level of the battery 10 decreases, the operation of the drive motor 3 is restricted. Also, it is difficult to charge the battery 10 in a short time, and the opportunity to charge the battery 10 is limited. For example, in the case of an electric vehicle, the battery 10 can be charged only during regeneration while driving. In the case of a hybrid vehicle, the battery 10 can be charged using the power of the engine in addition to during regeneration, but the fuel consumption deteriorates.

[0116] Therefore, when the SOC of the battery 10 is low (low state of charge), the power of the battery 10 is more precious than when the SOC of the battery 10 is high (high state of charge). Thus, in the magnetic force change determination unit 21c of this Application Example 2, when performing magnetic force change determination in a low state of charge, it is configured to use a weighting coefficient α with a larger value than when performing magnetic force change determination in a high state of charge.

[0117] FIG. 11 shows the flow of the specific magnetic force change determination process performed by the magnetic force change determination unit 21c of Application Example 2. The basic process flow is the same as that of the above-described embodiment (see FIG. 8). The same reference numerals are used for the processes with the same content, and the description thereof is omitted or simplified.

[0118] When the magnetic force change determination unit 21c determines an operating point to be the target of magnetic force change determination (step S1), it also performs in parallel a determination process (step S41) as to whether the SOC of the battery 10 is equal to or higher than a predetermined threshold X (%). The threshold X is a value serving as a weighting criterion regarding the remaining battery level of the battery 10 and is set in the magnetic force change determination unit 21c. Note that performing these calculation processes C1, C2 and the determination process in parallel is effective for shortening the processing time, but is not essential.

[0119] When the magnetic force change determination unit 21c determines that the SOC of the battery 10 is equal to or higher than the threshold X, it adopts a predetermined weighting coefficient αC as the weighting coefficient α (step S42). On the other hand, when the magnetic force change determination unit 21c determines that the SOC of the battery 10 is less than the threshold X, it adopts a predetermined weighting coefficient αD as the weighting coefficient α (step S43). These weighting coefficients αC and αD are both set based on a third map.

[0120] As described above, when the SOC of the battery 10 is low (low state of charge), the power of the battery 10 is more precious than when the SOC of the battery 10 is high (high state of charge). Accordingly, the weighting factor αD in the low state of charge is usually set to be greater than 1 and greater than the weighting factor αC in the high state of charge (1 < αD, αC < αD). By doing so, the power consumption of the battery 10 can be suppressed in the low state of charge more than in the high state of charge, and the drive motor 3 can be used more effectively together with the battery 10.

[0121] The magnetic force change determination unit 21c performs a weighting process on the power gain PG using the weighting factor α set based on such determination processing, and then subtracts the power loss PL from the power gain PG to obtain a power balance value (step S9). Then, it is determined whether this balance value is greater than 0 (step S10). Thus, when the power gain PG is greater than the power loss PL (balance value PB > 0), the magnetic force change determination unit 21c determines that magnetization processing is to be performed (step S11). On the other hand, when the power gain PG is less than or equal to the power loss PL (balance value PB ≤ 0), the magnetic force change determination unit 21c determines that magnetization processing is not to be performed (step S12).

[0122] <Application Example 3> In the control device of Application Example 3, the criterion for magnetic force change determination is changed in consideration of both the determination of whether the vehicle 1 is in the power running state or the regeneration state and the determination of whether the battery 10 is in the low state of charge or the high state of charge. That is, the control device of this Application Example 3 is configured to include the contents of both Application Example 1 and Application Example 2.

[0123] Fig. 12 shows the flow of the specific magnetic force change determination process performed by the magnetic force change determination unit 21c of Application Example 3. The basic flow of the process is the same as that of the above-described embodiment (see Fig. 8). The same reference numerals are used for the processes with the same content, and the description thereof is omitted or simplified.

[0124] When the magnetic force change determination unit 21c determines the operating point to be the target of magnetic force change determination (step S1), it also performs, in parallel with each of the calculation process C1 regarding the power gain PG and the calculation process C2 regarding the power loss PL at that operating point, the determination process as to whether the driving state of the vehicle 1 is power running or regeneration (step S51). Note that performing these calculation processes C1, C2 and the determination process in parallel is effective in shortening the processing time, but is not essential.

[0125] When the magnetic force change determination unit 21c determines that the vehicle 1 is power running, it performs the determination process as to whether the SOC of the battery 10 is equal to or higher than a predetermined threshold value X (%) (step S52). Then, when the magnetic force change determination unit 21c determines that the SOC of the battery 10 is equal to or higher than the threshold value X, it adopts the first weight coefficient α1 as the weight coefficient α (step S53). When it determines that the SOC of the battery 10 is less than the threshold value X, the magnetic force change determination unit 21c adopts the second weight coefficient α2 as the weight coefficient α (step S54).

[0126] On the other hand, when the magnetic force change determination unit 21c determines that the vehicle 1 is in regeneration, it performs the determination process as to whether the SOC of the battery 10 is equal to or higher than a predetermined threshold value X (%) (step S55). Then, when the magnetic force change determination unit 21c determines that the SOC of the battery 10 is equal to or higher than the threshold value X, it adopts the third weight coefficient α3 as the weight coefficient α (step S56). When it determines that the SOC of the battery 10 is less than the threshold value X, the magnetic force change determination unit 21c adopts the fourth weight coefficient α4 as the weight coefficient α (step S57).

[0127] These first to fourth weight coefficients α1, α2, α3, α4 are all set based on the third map. Fig. 13 shows the magnitude relationship of these first to fourth weight coefficients α1, α2, α3, α4. The magnitude relationship of these first to fourth weight coefficients α1, α2, α3, α4 is set to increase in the direction indicated by the arrow.

[0128] That is, the first weighting coefficient α1 used when the vehicle is in power running and in a high state of charge is set to a relatively small value. The fourth weighting coefficient α4 used when the vehicle is in regeneration and in a low state of charge is set to a relatively large value. And each of the second weighting coefficient α2 used when the vehicle is in power running and in a low state of charge and the third weighting coefficient α3 used when the vehicle is in regeneration and in a high state of charge is set to a value approximately intermediate between those of the first and fourth weighting coefficients α1 and α4.

[0129] In this way, in the control device of Application Example 3, the criterion for magnetic force change determination is changed in consideration of both the determination of whether the vehicle 1 is in power running or regeneration and the determination of whether the battery 10 is in a low state of charge or a high state of charge. As a result, it is possible to achieve a good balance between suppression of energy loss based on the difference in the operating state of the drive motor 3 and suppression of power consumption based on the state of charge of the battery 10.

[0130] The magnetic force change determination unit 21c performs a weighting process on the power gain PG using the weighting coefficient α set based on such determination processing, and then subtracts the power loss PL from the power gain PG to obtain a power balance value (step S9). Then, it is determined whether this balance value is greater than 0 (step S10). Thus, when the power gain PG is greater than the power loss PL (balance value PB>0), the magnetic force change determination unit 21c determines that magnetization processing is to be performed (step S11). On the other hand, when the power gain PG is less than or equal to the power loss PL (balance value PB≦0), the magnetic force change determination unit 21c determines that magnetization processing is not to be performed (step S12).

[0131] As described above, according to the control device of this vehicle 1, magnetization processing is not performed uniformly at the timing of shifting between the predetermined magnetization regions Rm, but magnetization processing is performed in consideration of the energy balance of the entire system that drives the drive motor 3. Thereby, energy loss can be suppressed. Therefore, since the drive motor 3 can be used more effectively, the vehicle 1 can run more efficiently and the fuel efficiency can also be improved.

[0132] Note that the disclosed technology is not limited to the above-described embodiments, and includes various other configurations. That is, the configurations such as the vehicle 1 and the drive motor 3 shown in the embodiments are merely examples. These configurations can be appropriately changed according to the specifications. For example, when the vehicle 1 is a hybrid vehicle, it may be a strong hybrid vehicle.

[0133] Also, in the above-described embodiments, the second energy loss generated to reduce the torque fluctuation generated during the magnetization process has been described as the energy loss when the high torque generated during the magnetization is slipped. However, it is not limited thereto, and the second energy loss may be, for example, the energy loss generated by supplementing the low torque generated during the demagnetization with the torque of a drive source different from the drive motor 3, for example, a second motor.

Explanation of Reference Numerals

[0134] 1 Vehicle (electric vehicle) 2 Engine 3 Drive motor 10 Battery 20 Engine control unit (ECU) 21 Motor control unit (MCU) 21a Motor output control unit 21b Magnetization processing unit 21c Magnetic force change determination unit 22 Transmission control unit (TCU) 22a Relay clutch control unit 22b Transmission clutch control unit 23 Brake control unit (BCU) 24 Integrated control unit (GCU) 35 Magnet (magnetic force variable magnet) 83 Transmission clutch

Claims

1. A control device for an electric vehicle equipped with a drive motor in which the magnetic poles of a rotor are constituted by a magnet with variable magnetic force capable of changing the magnetic force, and capable of traveling using electric power, a magnetization processing unit that performs magnetization processing for changing the magnetic force of the variable magnetic force magnet; a magnetic force change determination unit that determines whether or not to perform the magnetization processing from the viewpoint of energy gain and loss according to the operating state of the drive motor based on the rotational speed and torque; comprising: wherein the magnetic force change determination unit acquires each of a first electric power consumed or generated by the drive motor when the magnetization processing is not performed, a second electric power consumed or generated by the drive motor when the magnetization processing is performed, and an energy loss generated by performing the magnetization processing; compares the magnitude relationship between the power gain obtained by subtracting the first electric power and the second electric power, and the power loss obtained by converting the energy loss; A control device that determines to perform the magnetization processing when the power gain is greater than the power loss, and determines not to perform the magnetization processing when the power gain is less than or equal to the power loss.

2. In the control device according to claim 1, the energy loss includes a first energy loss consumed for changing the magnetic force of the variable magnetic force magnet and a second energy loss generated for reducing torque fluctuations output from the drive motor during the magnetization processing. A control device.

3. In the control device according to claim 1 or 2, when the magnetic force change determination unit compares the magnitude relationship between the power gain and the power loss, it multiplies the power gain by a predetermined weighting factor and compares it with the power loss. A control device.

4. In the control device according to claim 3, the electric vehicle is further configured to be able to travel using fuel by further including an engine, When performing the magnetic force change determination when the electric vehicle is regenerating, a larger value of the weighting factor is used than when performing the magnetic force change determination when the electric vehicle is powering. A control device.

5. In the control device according to claim 3 or 4, the electric vehicle further includes a battery that supplies electric power input to the drive motor and stores electric power generated by the drive motor. When performing the magnetic force change determination when the remaining battery level of the battery is in a low charge state less than a predetermined threshold, a larger value of the weight coefficient is used than when performing the magnetic force change determination when the remaining battery level of the battery is in a high charge state equal to or higher than the threshold. A control device.

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