Electronic control unit

Abstract

The present disclosure provides an electronic control device that is capable of limiting noise from an electric motor when switching carrier frequencies. This electronic control device controls an electric motor for the travel of a vehicle, the device including a switching condition storage unit (122), a traveling load computing unit (121), a switching condition determining unit (123), and a frequency control unit (124). The switching condition storage unit (122) stores a switching condition in which the rotation speed of the electric motor is less than a predetermined lower limit value and a torque command of the electric motor is higher than a predetermined upper limit value. The traveling load computing unit (121) calculates a traveling load (Lt) of the vehicle on the basis of the rotation speed (ω) and the torque command (Tc) of the electric motor. The switching condition determining unit (123) determines whether the switching condition is satisfied after a predetermined time period has elapsed, on the basis of the traveling load (Lt) of the vehicle and the rotation speed (ω) and the torque command (Tc) of the electric motor. When the switching condition determining unit (123) has determined that the switching condition is satisfied, the frequency control unit (124) reduces the carrier frequency of the electric motor when the torque command of the electric motor is equal to or less than the upper limit value.

Description

[Technical Field]

[0001] The present disclosure relates to an electronic control device for controlling an electric motor. [Background technology]

[0002] There has been known a power output device that outputs driving power (see Patent Document 1 below). This conventional power output device includes, for example, a plurality of electric motors capable of outputting driving power, a plurality of drive circuits that respectively drive the plurality of electric motors, a required power setting means that sets a required power based on an operation by an operator, and a control means that drives and controls the plurality of drive circuits (see Patent Document 1 below, paragraph 0006, claim 1, abstract, etc.).

[0003] The plurality of drive circuits have switching elements and drive the plurality of electric motors by switching the switching elements. The control means controls the drive of the plurality of drive circuits so that power based on the set required power is output from the plurality of electric motors when all of the plurality of drive circuits are in a normal state where they can function normally. Furthermore, the control means controls the drive of the plurality of drive circuits as follows when any of the plurality of drive circuits is in an abnormal state where it cannot function normally.

[0004] That is, the control means controls the driving of the plurality of drive circuits based on the switching frequency of the switching elements of the drive circuits in the abnormal state and the power from the electric motors driven by the drive circuits in the abnormal state. More specifically, the control means controls the driving of the plurality of drive circuits so that, of the switching frequency and the power, the power is limited with priority over the switching frequency, and power based on the set required power is output from the plurality of electric motors.

[0005] This conventional power output device can reduce the burden on a drive circuit in an abnormal state while suppressing noise caused by switching of the switching elements of the drive circuit in the abnormal state. As a result, it is possible to achieve both good drive of the drive circuit and suppress noise caused by drive. Furthermore, it is possible to respond to the required power regardless of whether any of the multiple drive circuits is in the normal state (Patent Document 1, paragraph 0007). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-197717 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional power output device described above, for example, torque is distributed among the multiple electric motors until the temperature of the drive circuit reaches a temperature limit, and therefore the carrier frequency may be switched while the electric motors are outputting high torque. If the carrier frequency is switched while the electric motors are outputting high torque, noise may be generated from the electric motors.

[0008] The present disclosure provides an electronic control device that can suppress noise from an electric motor when switching carrier frequencies. [Means for solving the problem]

[0009] One aspect of the present disclosure is an electronic control device that controls an electric motor for driving a vehicle, comprising: a switching condition memory unit that stores switching conditions under which the rotational speed of the electric motor is lower than a predetermined lower limit value and the torque command of the electric motor is greater than a predetermined upper limit value; a running load calculation unit that calculates the running load of the vehicle based on the rotational speed and torque command of the electric motor; a switching condition determination unit that determines whether the switching condition is met after a predetermined time has elapsed based on the running load of the vehicle and the rotational speed and torque command of the electric motor; and a frequency control unit that lowers the carrier frequency of the electric motor when the torque command of the electric motor is below the upper limit value when the switching condition determination unit determines that the switching condition is met. [Effects of the Invention]

[0010] According to the above aspect of the present disclosure, it is possible to provide an electronic control device that can suppress noise of an electric motor when switching the carrier frequency. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram illustrating an embodiment of an electronic control device according to the present disclosure. [Figure 2] FIG. 2 is a block diagram of a torque control unit that constitutes the electronic control device of FIG. 1. [Figure 3] FIG. 2 is a block diagram of a three-phase current control unit that constitutes the electronic control device of FIG. 1. [Figure 4] 4 is a graph illustrating a switching condition storage unit that configures the three-phase current control unit of FIG. 3; [Figure 5] 4 is a graph illustrating a switching condition storage unit that configures the three-phase current control unit of FIG. 3; [Figure 6] FIG. 4 is a block diagram of a PWM control unit constituting the three-phase current control unit of FIG. 3. [Figure 7] FIG. 2 is a flowchart illustrating the operation of the electronic control device of FIG. 1. [Figure 8] 2 is a state transition diagram of the vehicle under the control of the electronic control unit of FIG. 1. [Figure 9] 9 is a graph showing the torque command etc. of the electric motor in the state (i) of FIG. 8; [Figure 10] 9 is a graph showing the torque command etc. of the electric motor in the state (ii) of FIG. 8; [Figure 11] 9 is a graph showing the torque command etc. of the electric motor in the state (iii) of FIG. 8; [Figure 12] 9 is a graph showing a torque command etc. of the electric motor in state (iv) of FIG. 8; [Figure 13] 9 is a graph showing the torque command etc. of the electric motor in state (v) of FIG. 8; [Figure 14] 9 is a graph showing the torque command etc. of the electric motor in state (vi) of FIG. 8; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of an electronic control device according to the present disclosure will be described with reference to the drawings.

[0013] Fig. 1 is a block diagram showing an embodiment of an electronic control device according to the present disclosure. The electronic control device 100 of this embodiment is mounted on a vehicle 10, such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle, and controls an electric motor 11 for driving the vehicle 10. Although not shown in Fig. 1, the vehicle 10 is also equipped with, for example, a steering device, a braking device, a power transmission device, an electricity storage device, and the like, which are generally equipped in a normal vehicle.

[0014] 1, a vehicle 10 has two electric motors 11 for driving: a first electric motor 11F that drives left and right front wheels 13F via gears 12F, and a second electric motor 11R that drives left and right rear wheels 13R via gears 12R. The vehicle 10 also has, for example, an accelerator position sensor 14 that detects the opening degree of an accelerator pedal, and an acceleration sensor 15 that detects the acceleration of the vehicle 10 in the longitudinal direction.

[0015] 1, the vehicle 10 has, for example, an ABS control unit 16 that constitutes an antilock brake system (ABS) and a TCS control unit 17 that constitutes a traction control system (TCS). Although not shown in FIG. 1, the vehicle 10 also has various sensors that are generally provided in a normal vehicle. The vehicle 10 is only required to have at least one electric motor 11 for driving, and may have four or more electric motors 11 (in-wheel motors) that drive the respective wheels 13.

[0016] The electronic control device 100 is configured, for example, by a plurality of electronic circuits including a plurality of microcontrollers and a plurality of electronic components (not shown). Each microcontroller constituting the electronic control device 100 has, for example, an input / output unit, a memory, a timer, and a central processing unit (CPU). The electronic control device 100 realizes various functions, which will be described later, by, for example, executing a program stored in the memory using the CPU.

[0017] 1 , the electronic control device 100 includes, for example, a torque control unit 110 and a three-phase current control unit 120. The electronic control device 100 may also include, for example, an inverter 130. The electronic control device 100 includes, for example, a first three-phase current control unit 120F and a first inverter 130F that control the first electric motor 11F, and a second three-phase current control unit 120R and a second inverter 130R that control the second electric motor 11R. That is, one three-phase current control unit 120 and one inverter 130 are provided for each electric motor 11.

[0018] Torque control unit 110 receives, for example, accelerator pedal operation amount Qac from accelerator position sensor 14 and longitudinal acceleration α of vehicle 10 from acceleration sensor 15. Torque control unit 110 also receives, for example, a control signal Sab related to antilock braking from ABS control unit 16 and a control signal Stc related to traction control from TCS control unit 17.

[0019] Furthermore, the torque control unit 110 receives, for example, an input of the rotation speed ω of the electric motor 11 from the three-phase current control unit 120. In the example shown in Fig. 1, the torque control unit 110 receives, for example, an input of the rotation speed ωF of the first electric motor 11F from the first three-phase current control unit 120F, and an input of the rotation speed ωR of the second electric motor 11R from the second three-phase current control unit 120R.

[0020] The torque control unit 110 outputs a torque command Tc and a torque change rate limit ΔTr based on, for example, the input accelerator pedal operation amount Qac, the acceleration α of the vehicle 10, the rotation speed ω of the electric motor 11, and control signals Sab, Stc, etc. More specifically, the torque control unit 110 outputs a torque command TcF and a torque change rate limit ΔTrF for the first electric motor 11F, and a torque command TcR and a torque change rate limit ΔTrR for the second electric motor 11R.

[0021] The three-phase current control unit 120 receives a torque command Tc and a torque change rate limit ΔTr for the electric motor 11 from the torque control unit 110. More specifically, the first three-phase current control unit 120F receives a torque command TcF and a torque change rate limit ΔTrF for the first electric motor 11F from the torque control unit 110. The second three-phase current control unit 120R receives a torque command TcR and a torque change rate limit ΔTrR for the second electric motor 11R from the torque control unit 110.

[0022] The three-phase current control unit 120 also receives the rotation angle θ from the electric motor 11. More specifically, the first three-phase current control unit 120F receives the rotation angle θ from the first electric motor 11F, and the second three-phase current control unit 120R receives the rotation angle θ from the second electric motor 11R.

[0023] The three-phase current control unit 120 also receives an inverter voltage Vin from the inverter 130. More specifically, the first three-phase current control unit 120F receives an inverter voltage VinF from the first inverter 130F, and the second three-phase current control unit 120R receives an inverter voltage VinR from the second inverter 130R.

[0024] The three-phase current control unit 120 receives the three-phase currents Iu, Iv, and Iw from the inverter 130. More specifically, the first three-phase current control unit 120F and the second three-phase current control unit 120R receive the three-phase currents Iu, Iv, and Iw from the first inverter 130F and the second inverter 130R, respectively.

[0025] The three-phase current control unit 120 outputs gate signals Iu, Iv, Iw, Ix, Iy, and Iz based on the above inputs. More specifically, the first three-phase current control unit 120F outputs gate signals Iu, Iv, Iw, Ix, Iy, and Iz to the first inverter 130F, and the second three-phase current control unit 120R outputs gate signals Iu, Iv, Iw, Ix, Iy, and Iz to the second inverter 130R.

[0026] The inverter 130 is connected to, for example, a power supply voltage Vs, and receives gate signals Iu, Iv, Iw, Ix, Iy, and Iz from the three-phase current control unit 120. More specifically, the first inverter 130F and the second inverter 130R receive gate signals Iu, Iv, Iw, Ix, Iy, and Iz from the first three-phase current control unit 120F and the second three-phase current control unit 120R, respectively.

[0027] Based on the above inputs, the inverter 130 outputs, for example, three-phase currents Iu, Iv, and Iw to the electric motor 11, and outputs an inverter voltage Vin to the three-phase current control unit 120. More specifically, the first inverter 130F and the second inverter 130R output three-phase currents Iu, Iv, and Iw to the first electric motor 11F and the second electric motor 11R, respectively. Furthermore, the first inverter 130F and the second inverter 130R output inverter voltages VinF and VinR to the first three-phase current control unit 120F and the second three-phase current control unit 120R, respectively.

[0028] Fig. 2 is a block diagram of the torque control unit 110 constituting the electronic control device 100 of Fig. 1. The torque control unit 110 has, for example, a required torque generation unit 111, a running load calculation unit 112, a control torque generation unit 113, and a torque command generation unit 114.

[0029] The required torque generation unit 111 receives, for example, the accelerator pedal operation amount Qac and the rotation speeds ω(ωF, ωR) of the electric motors 11. Based on these inputs, the required torque generation unit 111 calculates, for example, a total required torque RTT, a required torque RTF of the first electric motor 11F, and a required torque RTR of the second electric motor 11R, and outputs these to the torque command generation unit 114.

[0030] The running load calculation unit 112 receives, for example, the rotation speed ω(ωF, ωR) of each electric motor 11 and the acceleration α of the vehicle 10 as input. The running load calculation unit 112 estimates a running resistance value due to the gradient from the rotation speed ω of the electric motor 11 and the acceleration α of the vehicle 10. Furthermore, the running load calculation unit 112 calculates a running load Lt of the vehicle 10 using the estimated running resistance value and the weight and frontal projected area of ​​the vehicle 10 stored in memory, and outputs the calculated value to the torque command generation unit 114.

[0031] The control torque generation unit 113 receives, for example, a control signal Sab from the ABS control unit 16 and a control signal Stc from the TCS control unit 17. Based on these inputs, the control torque generation unit 113 calculates a control torque CT required for control to stabilize the vehicle 10, such as antilock braking and traction control, and outputs the calculated control torque CT to the torque command generation unit 114.

[0032] The torque command generation unit 114 receives, for example, the total required torque RTT, the required torque RTF, and the required torque RTR from the required torque generation unit 111, and receives the rotational speed ω of each electric motor 11 from each three-phase current control unit 120. The torque command generation unit 114 also receives the running load Lt from the running load calculation unit 112 and the control torque CT from the control torque generation unit 113. Based on these inputs, the torque command generation unit 114 calculates the torque commands Tc (TcF, TcR) and torque change rate limits ΔTr (ΔTrF, ΔTrR) of each electric motor 11, and outputs them to each three-phase current control unit 120.

[0033] Fig. 3 is a block diagram of the three-phase current control unit 120 constituting the electronic control device 100 of Fig. 1. The three-phase current control unit 120 has, for example, a running load calculation unit 121, a switching condition storage unit 122, a switching condition determination unit 123, a frequency control unit 124, and a pulse width modulation (PWM) control unit 125.

[0034] The running load calculation unit 121 estimates the running resistance value of the vehicle 10 due to the gradient, for example, by inputting the torque command Tc and the rotation speed ω of each electric motor 11. Furthermore, the running load calculation unit 121 calculates the running load Lt of the vehicle 10 from the running resistance value, the weight of the vehicle 10, the rotation speed ω of each electric motor 11, the frontal projection area of ​​the vehicle 10, etc., and outputs the calculated value to the switching condition determination unit 123.

[0035] Figures 4 and 5 are graphs illustrating the switching condition storage unit 122, which is part of the three-phase current control unit 120 in Figure 3. More specifically, the graph in Figure 4 shows the operating region OA and switching region SA of the motor 11, with the horizontal axis representing the rotational speed ω of the motor 11 and the vertical axis representing the torque command Tc of the motor 11.

[0036] The switching region SA is, for example, a region where the rotation speed ω of the electric motor 11 is equal to or lower than a predetermined lower limit value ωl and the torque command Tc of the electric motor 11 is equal to or higher than a predetermined upper limit value Tch. In this switching region SA, it is necessary to lower the carrier frequency of the electric motor 11 to protect the inverter 130. That is, the graph shown in Fig. 4 represents the switching conditions that require switching of the carrier frequency as the switching region SA.

[0037] However, if the carrier frequency of the electric motor 11 is switched when the relationship between the torque command Tc and the rotation speed ω of the electric motor 11 is in the switching region SA, noise will be generated. Therefore, it is necessary to avoid switching the carrier frequency of the electric motor 11 in the switching region SA. In other words, the switching region SA is also a restricted region in which switching of the carrier frequency should be restricted from the viewpoint of suppressing noise of the electric motor 11.

[0038] 5, the horizontal axis represents the rotation speed ω of the electric motor 11 and the vertical axis represents the torque command Tc of the electric motor 11, and the relationship between the torque command Tc and the rotation speed ω of the electric motor 11 is shown for each of different magnitudes of running load Lt. As shown in FIG. 5, the larger the running load Lt, the larger the change in torque command Tc relative to the change in rotation speed ω of the electric motor 11. The graphs of FIGS. 4 and 5 are created for each electric motor 11, set and recorded in the switching condition storage unit 122, and output from the switching condition storage unit 122 to the switching condition determination unit 123 as necessary.

[0039] The switching condition determination unit 123 receives, for example, the torque command Tc, torque change rate limit ΔTr, and rotation speed ω of each electric motor 11, as well as the running load Lt of the vehicle 10. The switching condition determination unit 123 acquires, for example, from the switching condition storage unit 122, the operating region OA and switching region SA of each electric motor 11 shown in Fig. 4, and the relationship between the torque command Tc and the rotation speed ω corresponding to the running load Lt shown in Fig. 5. As described above, the switching region SA represents a switching condition that requires switching of the carrier frequency of the electric motor 11.

[0040] The switching condition determination unit 123 determines whether the relationship between the torque command Tc and the rotation speed ω of each electric motor 11 enters the switching region SA after a predetermined time has elapsed, for example, based on the above input, the switching region SA shown in Fig. 4, and the relationship shown in Fig. 5. Whether or not the relationship enters the switching region SA is synonymous with whether or not a switching condition that requires a reduction in the carrier frequency of the electric motor 11 is satisfied. More specifically, the switching condition determination unit 123, for example, overlays the graphs of Fig. 4 and Fig. 5, and determines that the relationship between the torque command Tc and the rotation speed ω of each electric motor 11 satisfies the switching condition after a predetermined time has elapsed if the Tc-ω curve in Fig. 5 enters or is in contact with the switching region SA in Fig. 4.

[0041] The switching condition determination unit 123 outputs a determination result DR to the frequency control unit 124 as to whether or not the relationship between the torque command Tc and the rotational speed ω of the electric motor 11 falls within the switching region SA after a predetermined time has elapsed, i.e., whether or not the switching condition that the rotational speed ω is lower than the lower limit value ωl and the torque command Tc is greater than the upper limit value Tch is satisfied.

[0042] For example, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to lower the carrier frequency of the electric motor 11 to be controlled, based on the determination result DR input from the switching condition determination unit 123. More specifically, when the determination result DR is positive, that is, when it is determined that the relationship between the torque command Tc and the rotation speed ω of the electric motor 11 to be controlled satisfies the switching condition after a predetermined time has elapsed, the frequency control unit 124 outputs the control signal Cfc.

[0043] Fig. 6 is a block diagram of a PWM control unit 125, which is a part of the three-phase current control unit 120 in Fig. 3. The PWM control unit 125 receives as input the three-phase currents Iu, Iv, and Iw of each electric motor 11, the rotation angle θ, and the torque command Tc, the inverter voltage Vin, and the control signal Cfc of the frequency control unit 124, and outputs gate signals Iu, Iv, Iw, Ix, Iy, and Iz and the rotation speed ω.

[0044] The PWM control unit 125 has, for example, a speed calculation unit 125a, a three-phase / dq conversion calculation unit 125b, a current command generation unit 125c, a current control unit 125d, a dq / three-phase conversion calculation unit 125e, and a PMW calculation unit 125f. Each of these units has a general configuration for vector control of the electric motor 11, which is a permanent magnet motor, and therefore description thereof will be omitted. The PWM control unit 125 reduces the carrier frequency of the power switching device in the inverter 130, for example, based on a control signal Cfc that reduces the carrier frequency of each electric motor 11.

[0045] The operation of the electronic control unit 100 of this embodiment will be described below with reference to Fig. 7 to Fig. 14. Fig. 7 is a flow chart illustrating the operation of the electronic control unit 100. Fig. 8 is a state transition diagram of the vehicle 10 under the control of the electronic control unit 100.

[0046] 8 indicates a state in which the electronic control device 100 is not controlling the electric motors 11 (11F, 11R), such as when the vehicle 10 is stopped. When the electronic control device 100 starts controlling the electric motors 11 and the vehicle 10 starts running from this state (o), the vehicle 10 transitions to, for example, state (i) shown in FIG. Then, the electronic control unit 100 executes the process P1 shown in Fig. 7. The state (i) is, for example, The running load Lt of the vehicle 10 is low, and the carrier frequency of the electric motor 11 does not need to be switched.

[0047] 7, for example, as described above, the accelerator pedal operation amount Qac, the acceleration α of the vehicle 10, and the control signals Sab and Stc of the ABS control unit 16 and the TCS control unit 17 are input to the torque control unit 110 of the electronic control device 100. Based on these inputs, the torque control unit 110 outputs a torque command Tc and a torque change rate limit ΔTr to each of the three-phase current control units 120 that control each of the electric motors 11, as described above.

[0048] Next, the electronic control device 100 executes a process P2 for acquiring a switching condition. In this process P2, the switching condition determination unit 123 constituting the three-phase current control unit 120 of the electronic control device 100 acquires, for each electric motor 11, for example, the operating region OA and the switching region SA in Fig. 4 and the relationship between the torque command Tc and the rotation speed ω according to the running load Lt in Fig. 5 from the switching condition storage unit 122.

[0049] Next, the electronic control unit 100 executes process P3 to determine whether the switching conditions are met. In process P3, as described above, the torque command Tc, torque change rate limit ΔTr, and rotation speed ω of each electric motor 11, as well as the running load Lt of the vehicle 10, are input to the switching condition determination unit 123 of the electronic control unit 100. Based on these inputs and the graphs of Figures 4 and 5 acquired in the previous process P2, for example, the switching condition determination unit 123 determines whether each electric motor 11 satisfies the switching conditions after a predetermined time has elapsed.

[0050] FIG. 9 shows the torque command Tc(T 9 is a graph showing an example of torque commands TcF, TcR, carrier frequency, and total torque of all electric motors 11. The first and second graphs of torque commands TcF, TcR from the top in Fig. 9 show maximum torques T1max, T2max of the first electric motor 11F and the second electric motor 11R, respectively, and torques T1q, T2q that can sufficiently suppress noise when the carrier frequency is switched.

[0051] In the state (i) of the vehicle 10, the running load Lt is relatively small, so as shown in FIG. Furthermore, the change in the torque command Tc relative to the change in the rotation speed ω of each electric motor 11 becomes relatively small. As a result, the torque commands Tc (TcF, TcR) of each electric motor 11 after a predetermined time has elapsed do not enter the switching region SA shown in FIG. 4, and the switching condition is not satisfied after the predetermined time has elapsed.

[0052] 7, the switching condition determination unit 123 determines that the switching condition is not satisfied (NO) after a predetermined time, and the electronic control device 100 executes process P5 without executing process P4, which will be described later. In process P5, the PWM control unit 125f constituting the PWM control unit 125 of the three-phase current control unit 120 controls the control signal Cfc and the command voltage Vu to lower the carrier frequency. * ,Vv * ,Vw * The control circuit 10 outputs gate signals Iu, Iv, Iw, Ix, Iy, and Iz according to the above.

[0053] Here, the torque control unit 110 may, for example, distribute the torque between the first electric motor 11F and the second electric motor 11R so that the relationship between the torque commands TcF, TcR and the rotational speeds ωF, ωR of the first electric motor 11F and the second electric motor 11R does not fall within the switching region SA shown in Figure 4.

[0054] The same applies when the vehicle 10 has four or more electric motors 11. That is, the torque control unit 110 may appropriately distribute torque among the plurality of electric motors 11 so that the relationship between the torque command Tc and the rotation speed ω does not fall within the switching region SA and switching of the carrier frequency is not required. In addition, in this process P5, the torque control unit 110 does not change the torque change rate limit ΔTr, for example.

[0055] Based on the input gate signals Iu, Iv, Iw, Ix, Iy, and Iz, each inverter 130 outputs three-phase currents Iu, Iv, and Iw to each electric motor 11. This causes each electric motor 11 to rotate, rotating the left and right front wheels 13F and the left and right rear wheels 13R via gears 12F and 12R, and causing the vehicle 10 to travel. Thereafter, the electronic control device 100, for example, ends the processing shown in FIG. 7 and repeatedly executes it at a predetermined cycle.

[0056] For example, if the vehicle 10 starts traveling and the traveling load Lt increases due to traveling uphill, the state of the vehicle 10 transitions from state (o) to state (ii) shown in Fig. 8. In state (ii), for example, the traveling load Lt of the vehicle 10 is higher than in state (i) and the plurality of electric motors 1 1, it is necessary to switch the carrier frequency to protect the inverter 130.

[0057] In the electronic control device 100 of this embodiment, state (ii) is, for example, a state in which it is necessary to switch the carrier frequency of the second electric motor 11R between the first electric motor 11F that drives the front wheels 13F and the second electric motor 11R that drives the rear wheels 13R. When the electronic control device 100 executes the above-described process P3 in this state (ii), for example, as shown in Fig. 5, the traveling load Lt of the vehicle 10 increases, and as a result, the change in the torque command Tc (TcR) relative to the change in the rotation speed ω (ωR) of the second electric motor 11R becomes larger than in the above-described state (i).

[0058] As a result, the switching condition determination unit 123 determines, for example, in process P3, that the relationship between the torque command TcR and the rotation speed ωR of the second electric motor 11R enters the switching region SA shown in FIG. 4 after a predetermined time has elapsed, satisfying the switching condition (YES). Also, the switching condition determination unit 123 determines, for example, in process P3, that the relationship between the torque command TcF and the rotation speed ωF of the first electric motor 11F does not enter the switching region SA shown in FIG. 4 after a predetermined time has elapsed, satisfying the switching condition (NO). Thereafter, the frequency control unit 124 outputs the determination result DR of process P3 to the PWM control unit 125.

[0059] In process P3, if it is determined that the switching condition is met (YES) for at least one electric motor 11 after a predetermined time has elapsed, the electronic control device 100 executes the next process P4. In process P4, the electronic control device 100 distributes torque among the multiple electric motors 11 and reduces the carrier frequency of the electric motor 11 that is determined to meet the switching condition after a predetermined time has elapsed.

[0060] Fig. 10 is a graph showing an example of the torque commands Tc (TcF, TcR) of each electric motor 11, the carrier frequency, and the total torque of all electric motors 11 (11F, 11R) in state (ii) of the vehicle 10 in Fig. 8. The first and second graphs of the torque commands TcF, TcR from the top of Fig. 10 show torques T1q, T2q that can sufficiently suppress noise when the carrier frequency is switched.

[0061] In process P4, the electronic control device 100, for example, in the second three-phase current control unit 120R that controls the second electric motor 11R, outputs a control signal Cfc that reduces the carrier frequency from the frequency control unit 124 to the PWM control unit 125. Here, the frequency control unit 124 outputs the control signal Cfc to the PWM control unit 125 before the torque command TcR of the second electric motor 11R exceeds a torque T2q that can sufficiently suppress noise when the carrier frequency is switched.

[0062] As a result, as shown in the second graph from the top and the second graph from the bottom in Fig. 10, before the torque command TcR of the second electric motor 11R exceeds the torque T2q, the carrier frequency of the second electric motor 11R is reduced to a predetermined frequency that can protect the inverter 130. This makes it possible to sufficiently suppress noise that is generated when the carrier frequency of the second electric motor 11R that drives the rear wheels 13R of the vehicle 10 is reduced.

[0063] In addition, before the curve showing the relationship between the torque command TcR and the rotational speed ωR of the second electric motor 11R enters the switching region SA, that is, when the torque command TcR of the second electric motor 11R is equal to or lower than the upper limit value Tch, it is possible to obtain a noise suppression effect by lowering the carrier frequency of the second electric motor 11R.

[0064] 7, the electronic control device 100 distributes torque to the plurality of electric motors 11, for example, by the torque control unit 110. More specifically, for example, the torque command generation unit 114 shown in FIG. 2 distributes torque commands TcF and TcR to the first electric motor 11F and the second electric motor 11R within a range that does not require switching of the carrier frequency of the first electric motor 11F.

[0065] The first and second graphs of torque commands TcF, TcR from the top in Fig. 10 show the maximum torques T1max, T2max of the first electric motor 11F and the second electric motor 11R, respectively, and the upper limit values ​​Tch of the torque commands TcF, TcR. These upper limit values ​​Tch are set so that the curves showing the relationship between the torque commands Tc and the rotation speed ω of the first electric motor 11F and the second electric motor 11R shown in Fig. 5 do not fall within the switching region SA shown in Fig. 4.

[0066] In process P4, the torque control unit 110 distributes the torque of the first electric motor 11F and the second electric motor 11R so that the torque command TcF of the first electric motor 11F that drives the front wheels 13F of the vehicle 10 does not enter the switching region SA shown in Fig. 4. More specifically, the torque control unit 110 limits the torque command TcF of the first electric motor 11F that does not lower the carrier frequency to an upper limit value Tch or less.

[0067] Furthermore, the torque control unit 110 increases the torque command TcR of the second electric motor 11R, whose carrier frequency has been reduced, beyond the upper limit value Tch, within a range that does not exceed the maximum torque T2max. Furthermore, in process P4, the torque control unit 110 reduces the torque change rate limit ΔTrR of the second electric motor 11R, for example, and does not change the torque change rate limit ΔTrF of the first electric motor 11F.

[0068] Thereafter, the electronic control device 100 executes, for example, the above-mentioned process P5, and ends the process shown in Fig. 7. As a result, the torque shortage caused by limiting the torque command TcF of the first electric motor 11F to be equal to or less than the upper limit value Tch is compensated for by the torque of the second electric motor 11R, and it becomes possible to output a desired total torque by the first electric motor 11F and the second electric motor 11R.

[0069] Furthermore, when the vehicle 10 travels on a steep uphill slope and the travel load Lt increases significantly or when the vehicle 10 is suddenly accelerated, the state of the vehicle 10 transitions from state (o) to state (iii) shown in FIG. 8, for example. In the state (iii), for example, the running load Lt of the vehicle 10 is higher than in the state (ii), and all This is a state in which the carrier frequency needs to be switched in order to protect the inverter 130 in the electric motor 11.

[0070] In the electronic control device 100 of this embodiment, the state (iii) is, for example, when the front wheel 13F is In this state (iii), it is necessary to switch the carrier frequencies of both the first electric motor 11F that drives the front wheel 13R and the second electric motor 11R that drives the rear wheel 13R. When the above-described process P3 is executed, the running load Lt of the vehicle 10 increases, and as a result, for example, as shown in FIG. 5, the change in the torque command Tc (TcF, TcR) relative to the change in the rotation speed ω (ωF, ωR) of the first electric motor 11F and the second electric motor 11R becomes larger than in state (ii).

[0071] As a result, the switching condition determination unit 123 determines, for example, in process P3, that the relationship between the torque commands TcF, TcR and the rotational speeds ωF, ωR of the first electric motor 11F and the second electric motor 11R enters the switching region SA shown in Figure 4 after a predetermined time has elapsed, satisfying the switching condition (YES). Thereafter, the frequency control unit 124 outputs this determination result DR to the PWM control unit 125.

[0072] Thereafter, the electronic control device 100 executes, for example, the next process P4. In this process P4, the electronic control device 100 reduces the carrier frequencies of both the first electric motor 11F and the second electric motor 11R that are determined to satisfy the switching condition after a predetermined time has elapsed, and distributes torque between the first electric motor 11F and the second electric motor 11R.

[0073] FIG. 11 shows the torque command Tc (TcF, TcR) of the electric motor 11 in the state (iii) of FIG. 11 is a graph showing an example of the torque commands TcF and TcR, the carrier frequency, and the total torque of all the electric motors 11 (11F, 11R). The first and second graphs of the torque commands TcF and TcR from the top in FIG. 11 show torques T1q and T2q that can sufficiently suppress noise when the carrier frequency is switched.

[0074] In process P4, the electronic control device 100 outputs a control signal Cfc to lower the carrier frequency from the frequency control unit 124 to the PWM control unit 125 in each of the three-phase current control units 120 that control the first electric motor 11F and the second electric motor 11R. Here, the frequency control unit 124 of each three-phase current control unit 120 outputs the control signal Cfc to the PWM control unit 125 before the torque commands TcF, TcR of the first electric motor 11F and the second electric motor 11R exceed the respective torques T1q, T2q that can sufficiently suppress noise when the carrier frequency is switched.

[0075] 11, before the torque commands TcF and TcR of the first electric motor 11F and the second electric motor 11R, respectively, exceed the torques T1q and T2q, the carrier frequencies of the first electric motor 11F and the second electric motor 11R are reduced to a predetermined frequency that can protect the inverter 130. This makes it possible to sufficiently suppress noise that is generated when the carrier frequencies of the first electric motor 11F and the second electric motor 11R of the vehicle 10 are reduced.

[0076] It is possible to obtain a noise suppression effect by lowering the carrier frequencies of the first electric motor 11F and the second electric motor 11R before the torque commands TcR of the first electric motor 11F and the second electric motor 11R exceed the upper limit value Tch and enter the switching region SA, that is, before the switching condition is satisfied. Furthermore, in this process P4, the electronic control device 100, for example, appropriately distributes torque to the first electric motor 11F and the second electric motor 11R using the torque control unit 110.

[0077] Thereafter, the electronic control unit 100 executes, for example, the above-mentioned process P5, and ends the process shown in FIG. 7. As described above, the electronic control unit 100 executes the process shown in FIG. 7 in the state (iii) of the vehicle 10. Therefore, the carrier frequencies of the first electric motor 11F and the second electric motor 11R are reduced before the torque commands TcF, TcR exceed the torques Tq1, Tq2 or the upper limit value Tch that does not fall within the switching region SA. This makes it possible to suppress noise that is generated when the carrier frequencies of the first electric motor 11F and the second electric motor 11R of the vehicle 10 are reduced.

[0078] 8, the state (i) in which the running load Lt of the vehicle 10 is low and it is not necessary to reduce the carrier frequency of all the electric motors 11 is, for example, The state (iv) is a state in which, for example, the running load Lt of the vehicle 10 is higher than in the state (i) and some of the electric motors 11 are inverter-driven. This is a state in which it is necessary to switch the carrier frequency to protect the capacitor 130.

[0079] In the electronic control device 100 of this embodiment, state (iv) is, for example, a state in which switching of the carrier frequency of the second electric motor 11R is required between the first electric motor 11F that drives the front wheels 13F and the second electric motor 11R that drives the rear wheels 13R. When the electronic control device 100 executes the above-described process P3 in this state (iv), the switching condition determination unit 123 determines that the relationship between the torque command TcR and the rotation speed ωR of the second electric motor 11R enters the switching region SA shown in FIG. 4 after a predetermined time has elapsed, satisfying the switching condition (YES). Thereafter, the frequency control unit 124 outputs this determination result DR to the PWM control unit 125.

[0080] Thereafter, the electronic control device 100 executes, for example, the following process P4. In this process P4, the electronic control device 100 first distributes torque between the first electric motor 11F and the second electric motor 11R, and then reduces the carrier frequency of the second electric motor 11R.

[0081] 12 is a graph showing an example of the torque commands Tc (TcF, TcR) of the electric motors 11, the carrier frequency, and the total torque of all the electric motors 11 (11F, 11R) in state (iv) of FIG. 8. In process P4, before the frequency control unit 124 reduces the carrier frequency of the second electric motor 11R, the torque control unit 110, for example, reduces the torque command TcR of the second electric motor 11R and increases the torque command TcF of the first electric motor 11F to maintain the total torque at a constant value. At this time, the torque control unit 110, for example, increases the torque change rate limits ΔTrF and ΔTrR of the first electric motor 11F and the second electric motor 11R.

[0082] Thereafter, when the torque command TcR of the second electric motor 11R drops to a predetermined value that allows noise caused by switching of the carrier frequency to be suppressed, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to lower the carrier frequency of the second electric motor 11R, thereby making it possible to suppress noise caused by switching of the carrier frequency of the second electric motor 11R.

[0083] For example, the torque control unit 110 reduces the torque change rate limit ΔTrR at the timing when it is desired to switch the carrier frequency of the second electric motor 11R. Furthermore, for example, after the frequency control unit 124 reduces the carrier frequency of the second electric motor 11R, the torque control unit 110 increases the torque command TcR of the second electric motor 11R and limits the torque command TcF of the first electric motor 11F to an upper limit value Tch or less that falls within the switching region SA. This eliminates the need to switch the carrier frequency of the first electric motor 11F, and prevents noise that would occur when switching the carrier frequency at high torque.

[0084] As shown in FIG. 8, the state (i) in which the running load Lt of the vehicle 10 is low and it is not necessary to reduce the carrier frequency of all the electric motors 11 is, for example, when the running load Lt of the vehicle 10 is The sudden increase causes a transition to state (iii) via state (v). For example, the running load Lt of the vehicle 10 is higher than in the state (ii), and it is necessary to switch the carrier frequency in order to protect the inverters 130 of all the electric motors 11.

[0085] When the electronic control unit 100 executes the above-mentioned process P3 in this state (v), the switching condition determination unit The switching condition determination unit 123 determines whether the relationship between the torque commands TcF, TcR and the rotational speeds ωF, ωR of the first electric motor 11F and the second electric motor 11R enters the switching region SA shown in FIG. 4 after a predetermined time has elapsed, and the switching condition is satisfied (YES). The switching condition determination unit 123 outputs this determination result DR to the frequency control unit 124.

[0086] Thereafter, the electronic control device 100 executes, for example, the following process P4. In this process P4, the electronic control device 100 first reduces the carrier frequency of the second electric motor 11R, then distributes torque between the first electric motor 11F and the second electric motor 11R, and then reduces the carrier frequency of the first electric motor 11F.

[0087] FIG. 13 shows the torque command Tc (TcF, TcR) of the electric motor 11 in the state (v) of FIG. 4 is a graph showing an example of the carrier frequency and the total torque of all the electric motors 11 (11F, 11R). In process P4, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to reduce the carrier frequency of the second electric motor 11R before the relationship between the torque command TcR and the rotation speed ωR of the second electric motor 11R enters the switching region SA shown in FIG. 4 and satisfies the switching condition.

[0088] Thereafter, in process P4, the torque control unit 110, for example, decreases the torque command TcF of the first electric motor 11F and increases the torque command TcR of the second electric motor 11R to maintain the total torque at a constant value. At this time, the torque control unit 110, for example, increases the torque change rate limits ΔTrF and ΔTrR of the first electric motor 11F and the second electric motor 11R.

[0089] Thereafter, when the torque command TcF of the first electric motor 11F decreases to a torque T1q that can sufficiently suppress noise caused by switching of the carrier frequency, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to lower the carrier frequency of the first electric motor 11F, thereby suppressing noise caused by switching of the carrier frequency of the first electric motor 11F.

[0090] For example, the torque control unit 110 reduces the torque change rate limit ΔTrF at the timing when it is desired to switch the carrier frequency of the first electric motor 11F. Furthermore, for example, after lowering the carrier frequency of the first electric motor 11F, the torque control unit 110 increases the torque command TcF to the maximum torque T1max and maintains the torque command TcR of the second electric motor 11R at the maximum torque T2max.

[0091] 8, the state (ii) in which the carrier frequency of some of the electric motors 11 of the vehicle 10 needs to be reduced transitions to the above-mentioned state (iii) via state (vi) due to, for example, a further increase in the running load Lt of the vehicle 10. The running load Lt is higher than in the state (ii), and in all the electric motors 11, the carrier frequency needs to be switched to protect the inverters 130.

[0092] When the electronic control device 100 executes the above-described process P3 in this state (vi), the switching condition determination unit 123 determines that the relationship between the torque commands TcF, TcR and the rotational speeds ωF, ωR of the first electric motor 11F and the second electric motor 11R enters the switching region SA shown in Figure 4 after a predetermined time has elapsed, satisfying the switching condition (YES). Thereafter, the frequency control unit 124 outputs this determination result DR to the PWM control unit 125.

[0093] Thereafter, the electronic control device 100 executes, for example, the following process P4. In this process P4, the electronic control device 100 first reduces the carrier frequency of the second electric motor 11R, then distributes torque between the first electric motor 11F and the second electric motor 11R, and then reduces the carrier frequency of the first electric motor 11F.

[0094] Fig. 14 is a graph showing an example of the torque command Tc (TcF, TcR) of the electric motor 11, the carrier frequency, and the total torque of all the electric motors 11 (11F, 11R) in the state (vi) of Fig. 8. In process P4, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to reduce the carrier frequency of the second electric motor 11R before the relationship between the torque command TcR and the rotation speed ωR of the second electric motor 11R enters the switching region SA shown in Fig. 4 and satisfies the switching condition.

[0095] More specifically, the frequency control unit 124 outputs a control signal Cfc to the PWM control unit 125 to lower the carrier frequency of the second electric motor 11R before the torque command TcR of the second electric motor 11R exceeds the torque T2q that can sufficiently suppress noise when the carrier frequency is switched. This makes it possible to more reliably suppress noise caused by switching the carrier frequency of the second electric motor 11R.

[0096] Thereafter, in process P4, the torque control unit 110, for example, decreases the torque command TcF of the first electric motor 11F and increases the torque command TcR of the second electric motor 11R to maintain the total torque at a constant value. At this time, the torque control unit 110, for example, increases the torque change rate limits ΔTrF and ΔTrR of the first electric motor 11F and the second electric motor 11R.

[0097] Thereafter, when the torque command TcF of the first electric motor 11F falls to a predetermined value that makes it possible to suppress noise caused by switching of the carrier frequency, the electronic control device 100 outputs a control signal Cfc from the frequency control unit 124 to the PWM control unit 125 to lower the carrier frequency of the first electric motor 11F, thereby making it possible to suppress noise caused by switching of the carrier frequency of the first electric motor 11F.

[0098] For example, the torque control unit 110 reduces the torque change rate limit ΔTrF at the timing when it is desired to switch the carrier frequency of the first electric motor 11F. Furthermore, for example, after lowering the carrier frequency of the first electric motor 11F, the torque control unit 110 increases the torque command TcF and limits the torque command TcR of the second electric motor 11R to a maximum torque T2max or less.

[0099] As described above, the electronic control device 100 of this embodiment includes a switching condition storage unit 122, a running load calculation unit 121, a switching condition determination unit 123, and a frequency control unit 124, and controls the electric motor 11 for traveling the vehicle 10. The switching condition storage unit 122 stores a switching region SA as a switching condition in which the rotation speed ω of the electric motor 11 is lower than a predetermined lower limit ωl and the torque command Tc of the electric motor 11 is greater than a predetermined upper limit Tch. The running load calculation unit 121 calculates the running load Lt of the vehicle 10 based on the rotation speed ω and torque command Tc of the electric motor 11. The switching condition determination unit 123 determines whether the switching condition is satisfied after a predetermined time has elapsed based on the running load Lt of the vehicle 10, the rotation speed ω of the electric motor 11, and the torque command Tc of the electric motor 11. When the switching condition determination unit 123 determines that the switching condition is satisfied, the frequency control unit 124 reduces the carrier frequency of the electric motor 11 when the torque command Tc of the electric motor 11 is equal to or lower than the upper limit Tch.

[0100] With this configuration, the electronic control device 100 of this embodiment can suppress noise of the electric motor 11 when switching the carrier frequency. More specifically, the electronic control device 100 of this embodiment can determine, by the switching condition determination unit 123, whether the electric motor 11 satisfies the switching condition after a predetermined time has elapsed. This switching condition corresponds to the switching region SA shown in FIG. 4, and is a condition in which the rotation speed ω of the electric motor 11 is lower than a predetermined lower limit value ωl and the torque command Tc of the electric motor 11 is greater than a predetermined upper limit value Tch, and the carrier frequency of the electric motor 11 must be reduced. However, if the carrier frequency is reduced after the electric motor 11 satisfies the switching condition, the carrier frequency will be switched while the torque command Tc of the electric motor 11 is high, which may generate noise. Therefore, in the electronic control device 100 of this embodiment, when the switching condition determination unit 123 determines that the switching condition is satisfied after a predetermined time has elapsed, the frequency control unit 124 lowers the carrier frequency of the electric motor 11 when the torque command Tc of the electric motor 11 is equal to or lower than a predetermined upper limit value Tch, i.e., before the switching condition is satisfied. This makes it possible to lower the carrier frequency of the electric motor 11 when the torque command Tc is lower than when the electric motor 11 waits until the switching condition is satisfied, and makes it possible to suppress noise caused by switching of the carrier frequency.

[0101] Furthermore, in the electronic control device 100 of this embodiment, the electric motors 11 include at least a first electric motor 11F and a second electric motor 11R. Furthermore, the switching condition determination unit 123 determines whether or not the switching condition is satisfied for each of the first electric motor 11F and the second electric motor 11R. Then, the frequency control unit 124 reduces the carrier frequency of at least one of the first electric motor 11F and the second electric motor 11R, which is determined by the switching condition determination unit 123 to satisfy the switching condition after a predetermined time has elapsed, before the switching condition is satisfied.

[0102] With this configuration, the electronic control device 100 of this embodiment can reduce the carrier frequency of the electric motor 11 when the torque command TcF, TcR of at least one of the first electric motor 11F and the second electric motor 11R is equal to or lower than a predetermined upper limit value Tch. Therefore, noise generated when switching the carrier frequency can be suppressed compared to when the torque command Tc of the electric motor 11 is higher than the upper limit value Tch.

[0103] The electronic control device 100 of this embodiment also includes a torque control unit 110 that outputs torque commands TcF and TcR to the first electric motor 11F and the second electric motor 11R, respectively. For example, as shown in FIG. 12 , the torque control unit 110 increases the torque command Tc output to one of the first electric motor 11F or the second electric motor 11R, which is not a carrier frequency switching target and for which the switching condition determination unit 123 determines that the switching condition is not satisfied, within a range not exceeding a predetermined upper limit value Tch. The torque control unit 110 also reduces the torque command Tc output to the other of the first electric motor 11F or the second electric motor 11R, which is a carrier frequency switching target and for which the switching condition determination unit 123 determines that the switching condition is satisfied, to a predetermined value. When the torque control unit 110 reduces the torque command Tc output to the electric motor 11 to be switched to a predetermined value, the frequency control unit 124 reduces the carrier frequency of the electric motor 11 to be switched.

[0104] With this configuration, the electronic control device 100 of this embodiment can prevent the electric motor 11 that is not the target of carrier frequency switching from satisfying the switching condition. Therefore, it is possible to suppress noise caused by switching the carrier frequency of the electric motor 11 that is not the target of carrier frequency switching. Furthermore, the torque command Tc output to the electric motor 11 that is the target of carrier frequency switching is reduced to a predetermined value, and then the carrier frequency of the electric motor 11 that is the target of carrier frequency switching is reduced. Therefore, it is possible to suppress noise caused by switching the carrier frequency of the electric motor 11 that is the target of carrier frequency switching at a high torque.

[0105] Furthermore, in the electronic control device 100 of this embodiment, the torque control unit 110 reduces the torque command Tc output to the electric motor 11 that is the switching target to a predetermined value, for example, as shown in Fig. 12. Thereafter, the torque control unit 110 may increase the torque command Tc output to the electric motor 11 that is the switching target, for example, when the torque command Tc output to the electric motor 11 that is not the switching target reaches a predetermined upper limit value Tch.

[0106] With this configuration, the electronic control device 100 of this embodiment can reduce the torque command Tc output to the electric motor 11 whose carrier frequency is to be switched to a predetermined value, thereby reducing noise when the carrier frequency is switched. Furthermore, the torque command Tc of the electric motor 11 that is not the target of the switching can be suppressed to an upper limit value Tch or less, thereby preventing the need for switching the carrier frequency. Furthermore, the torque shortage caused by suppressing the torque command Tc of the electric motor 11 that is not the target of the switching can be compensated for by increasing the torque command Tc of the electric motor 11 after the carrier frequency is switched.

[0107] The electronic control device 100 of this embodiment also includes a torque control unit 110 that outputs torque commands TcF and TcR to the first electric motor 11F and the second electric motor 11R, respectively. When the switching condition determination unit 123 determines that the first electric motor 11F and the second electric motor 11R satisfy the switching condition after a predetermined time has elapsed, the frequency control unit 124 reduces the carrier frequency of one of the first electric motor 11F and the second electric motor 11R before that one of the first electric motor 11F and the second electric motor 11R satisfies the switching condition, as shown in Figures 13 and 14. After the frequency control unit 124 reduces the carrier frequency of the one of the electric motors 11, the torque control unit 110 increases the torque command Tc of the one of the electric motors 11 and reduces the torque command Tc of the other of the first electric motor 11F and the second electric motor 11R to a predetermined value. Furthermore, the frequency control unit 124 reduces the carrier frequency of the other electric motor 11 when the torque control unit 110 reduces the torque command Tc of the other electric motor 11 to the predetermined value.

[0108] With this configuration, the electronic control device 100 of this embodiment can suppress noise by switching the carrier frequency of the one electric motor 11 when the torque command Tc of that electric motor 11 is lower than the upper limit value Tch. Furthermore, noise can be suppressed by lowering the torque command Tc of the other electric motor 11 to a predetermined value and then lowering the carrier frequency of that electric motor 11. In addition, when lowering the torque command Tc of the other electric motor 11, a decrease in total torque can be suppressed by increasing the torque command Tc of the one electric motor 11 whose carrier frequency has been switched.

[0109] Furthermore, in the electronic control device 100 of this embodiment, the torque control unit 110 reduces the torque command Tc of the other electric motor 11 to the predetermined value. Thereafter, when the relationship between the torque command Tc and the rotation speed ω of the one electric motor 11 reaches the upper limit of the operating range of the one electric motor 11, the torque control unit 110 increases the torque command Tc of the other electric motor 11.

[0110] With this configuration, the electronic control device 100 of this embodiment can distribute torque between the first electric motor 11F and the second electric motor 11R, and can suppress noise by switching the carrier frequency when the torque command Tc is lower than the upper limit value Tch. Also, by distributing torque between the first electric motor 11F and the second electric motor 11R, a decrease in total torque can be suppressed.

[0111] Although the embodiments of the electronic control device according to the present disclosure have been described above in detail using the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope of the present disclosure are also included in the present disclosure. For example, in the above-described embodiment, the electronic control device suppresses switching of the carrier frequency of the first electric motor close to the driver's seat of the vehicle by preferentially switching the carrier frequency of the second electric motor farther from the driver's seat of the vehicle. However, the electronic control device may preferentially switch the carrier frequency of the first electric motor close to the driver's seat of the vehicle. Furthermore, the electronic control device may include a machine learning unit that learns the driving tendencies of the vehicle driver and updates the information stored in the switching condition storage unit. [Explanation of symbols]

[0112] 10 vehicles 11 Electric motor 11F 1st electric motor 11R 2nd electric motor 100 Electronic control device 110 Torque control section 121 Running load calculation unit 122 Switching condition memory unit 123 Switching condition determination unit 124 Frequency Control Unit Lt running load Tc Torque command TcF Torque command Tch upper limit TcR Torque command ω rotation speed ωF rotation speed ωl lower limit ωR rotation speed

Claims

1. An electronic control device that controls an electric motor for driving a vehicle, a switching condition storage unit that stores a switching condition in which the rotation speed of the electric motor is lower than a predetermined lower limit value and the torque command of the electric motor is greater than a predetermined upper limit value; a running load calculation unit that calculates a running load of the vehicle based on the rotation speed and torque command of the electric motor; a switching condition determination unit that determines whether the switching condition is satisfied after a predetermined time has elapsed based on the running load of the vehicle and the rotational speed and torque command of the electric motor; a frequency control unit that reduces a carrier frequency of the electric motor when a torque command of the electric motor is equal to or less than the upper limit value when the switching condition determination unit determines that the switching condition is satisfied; An electronic control device comprising:

2. the electric motors include at least a first electric motor and a second electric motor; the switching condition determination unit determines whether the switching condition is satisfied for each of the first electric motor and the second electric motor; 2. The electronic control device according to claim 1, wherein the frequency control unit reduces the carrier frequency of at least one of the first electric motor and the second electric motor, which is determined by the switching condition determination unit to satisfy the switching condition after a predetermined time has elapsed, before the switching condition is satisfied.

3. a torque control unit that outputs a torque command to each of the first electric motor and the second electric motor; the torque control unit increases, within a range equal to or less than the upper limit value, a torque command to be output to one of the first electric motor or the second electric motor, which is not a target for carrier frequency switching and which is determined by the switching condition determination unit to not satisfy the switching condition, and reduces, to a predetermined value, a torque command to be output to the other of the first electric motor or the second electric motor, which is a target for carrier frequency switching and which is determined by the switching condition determination unit to satisfy the switching condition; 3. The electronic control device according to claim 2, wherein the frequency control unit reduces the carrier frequency of the electric motor to be switched when the torque control unit reduces the torque command output to the electric motor to the predetermined value.

4. 4. The electronic control device according to claim 3, wherein the torque control unit increases the torque command output to the electric motor that is the target of switching when the torque command output to the electric motor that is not the target of switching reaches the upper limit value after reducing the torque command output to the predetermined value.

5. a torque control unit that outputs a torque command to each of the first electric motor and the second electric motor; When the switching condition determination unit determines that the first motor and the second motor satisfy the switching condition after a predetermined time has elapsed, the frequency control unit reduces a carrier frequency of one of the first motor and the second motor before the one of the first motor and the second motor satisfies the switching condition, the torque control unit increases a torque command for the one of the electric motors after the frequency control unit reduces the carrier frequency of the one of the electric motors, and reduces a torque command for the other of the first electric motor and the second electric motor to a predetermined value; 3. The electronic control device according to claim 2, wherein the frequency control unit reduces the carrier frequency of the other of the electric motors when the torque control unit reduces the torque command of the other of the electric motors to the predetermined value.

6. 6. The electronic control device according to claim 5, wherein the torque control unit increases the torque command of the other electric motor when a relationship between the torque command and the rotation speed of one of the electric motors reaches an upper limit of an operating range of the one of the electric motors after reducing the torque command of the other of the electric motors to the predetermined value.

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