electric vehicles

Abstract

To suppress generation of booming while limiting increase of a production cost.SOLUTION: An electric vehicle includes: first and second motors; first and second inverters for respectively driving the first and second motors; and a control device for setting first and second current effective value instructions and first and second current advance angle value instructions of respective first and second current vectors in dq coordinates with a d-axis and a q-axis as coordinate axes on the basis of first and second torque instructions of the first and second motors, respectively, thus controlling the first and second inverters. In a case where a torque difference that is a difference between the first and second torque instructions is a given torque difference or less, with a rotation speed difference that is a difference between first and second rotation speeds of the first and second motors being a given rotation speed difference or less, the control device sets the first and second current effective value instructions and first and second current advance angle value instructions so that a torque variance difference that is a difference between first and second torque variance of the first and second motors becomes equal to or higher than a given torque variance difference.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to electric vehicles.

Background Art

[0002] Conventionally, as this type of electric vehicle, there has been proposed one equipped with in-wheel motors each having a motor and a reduction mechanism for each wheel (see, for example, Patent Document 1). In this electric vehicle, between at least one combination of in-wheel motors, by varying the combination of the number of teeth of the reduction mechanisms, the frequencies of the sounds generated from the in-wheel motors of that combination are actively made different, suppressing the interference of these sounds to generate a booming sound.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When varying the components (hardware configuration) of the in-wheel motors as in the above-described electric vehicle, it leads to an increase in manufacturing cost. For this reason, suppressing the generation of a booming sound while suppressing an increase in manufacturing cost is regarded as one of the problems.

[0005] The main object of the electric vehicle of this disclosure is to suppress the generation of a booming sound while suppressing an increase in manufacturing cost.

Means for Solving the Problems

[0006] The electric vehicle of this disclosure has adopted the following means to achieve the above-described main object.

[0007] The electric vehicle of this disclosure a first and a second motor, and The first and second inverters drive the first and second motors, respectively, An electric vehicle comprising: a control device that controls the first and second inverters by setting first and second RMS current value commands and first and second current advance angle value commands for first and second current vectors in a dq coordinate system with the d axis and q axis as coordinate axes, based on first and second torque commands of the first and second motors, The control device sets the first and second effective current command and the first and second current advance value command so that the torque difference, which is the difference between the first and second torque commands, is less than or equal to a predetermined torque difference, and the rotational speed difference, which is the difference between the first and second rotational speeds of the first and second motors, is less than or equal to a predetermined rotational speed difference, so that the torque fluctuation difference, which is the difference between the first and second torque fluctuations of the first and second motors, is greater than or equal to a predetermined torque fluctuation difference. This is the gist of it.

[0008] In the electric vehicle of this disclosure, when the torque difference, which is the difference between the first and second torque commands, is less than or equal to a predetermined torque difference, and the rotational speed difference, which is the difference between the first and second rotational speeds of the first and second motors, is less than or equal to a predetermined rotational speed difference, the first and second RMS current command and the first and second current advance value command are set so that the torque fluctuation difference, which is the difference between the first and second torque fluctuations of the first and second motors, is greater than or equal to a predetermined torque fluctuation difference. Through experiments and analyses, the inventors have confirmed that when the torque difference is less than or equal to a predetermined torque difference and the rotational speed difference is less than or equal to a predetermined rotational speed difference, the greater the torque fluctuation of the first and second motors, the more likely the noise and vibration of the first and second motors are to increase, and when the noise and vibration of the first and second motors are of a similar degree, a humming noise is more likely to occur. Therefore, when the torque difference is less than or equal to a predetermined torque difference and the rotational speed difference is less than or equal to a predetermined rotational speed difference, by controlling the inverter to set the first and second current effective value commands and the first and second current advance value commands so that the torque fluctuation difference is greater than or equal to a predetermined torque fluctuation difference, it is possible to amplify and make noticeable the sound and vibration of one of the first and second motors while reducing and making inconspicuous the sound and vibration of the other. As a result, it is possible to suppress the generation of humming noise. In other words, it is possible to suppress the generation of humming noise while suppressing the increase in manufacturing costs compared to changing the hardware configuration of the electric vehicle.

[0009] In the electric vehicle of this disclosure, the control device may set the first and second current effective value commands and the first and second current advance value commands so that one of the first and second torque fluctuations is minimized. This makes the noise and vibration of the first and second motors less noticeable and less noticeable.

[0010] In the electric vehicle of this disclosure, the first and second motors may be mounted to drive the left and right drive wheels, respectively. In this case, the conditions that the torque difference is less than or equal to a predetermined torque difference and the rotational speed difference is less than or equal to a predetermined rotational speed difference are more likely to be met when driving in a straight line, etc., which is why the present invention is significant. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the electric vehicle 20 according to the embodiment of the present disclosure. [Figure 2] This is a schematic diagram of the electric drive system of electric vehicle 20. [Figure 3] This flowchart shows an example of a setting processing routine executed by the electronic control unit 70. [Figure 4] This is an explanatory diagram illustrating an example of the relationship between the torque commands Tma*, Tmb* and torque fluctuations TFma, TFmb of motors 32 and 42, the current advance value commands φia*, φib*, and the current effective value commands Ira*, Irb*. [Figure 5] This is a schematic diagram of a modified electric vehicle 120. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of an electric vehicle 20 according to an embodiment of this disclosure. Figure 2 is a schematic diagram of the electric drive system provided by the electric vehicle 20. As shown in Figure 1, the electric vehicle 20 of the embodiment includes two motors 32, 42, two inverters 34, 44, a battery 50 as an energy storage device, and an electronic control unit 70 as a control device.

[0013] Motors 32 and 42 are configured as synchronous regenerative motors (in-wheel motors) mounted within the left and right drive wheels 22a and 22b, respectively, and drive the left and right drive wheels 22a and 22b. Motors 32 and 42 are configured to have the same specifications.

[0014] Inverters 34 and 44 are used to drive motors 32 and 42 and are connected to power line 54. As shown in Figure 2, inverter 34 has six switching elements, transistors T11 to T16, and six diodes D11 to D16 connected in parallel to each of the six transistors T11 to T16. Transistors T11 to T16 are arranged in pairs, with two on each side, acting as the source and sink sides with respect to the positive and negative terminal lines of power line 54. Each connection point of a pair of transistors T11 to T16 is connected to each of the three-phase (U-phase, V-phase, W-phase) coils of motor 32. Therefore, when voltage is applied to inverter 34, the electronic control unit 70 adjusts the ratio of on-times for each pair of transistors T11 to T16, thereby forming a rotating magnetic field in the three-phase coils and driving motor 32 to rotate. Inverter 44, like inverter 34, has six transistors T21-T26 and six diodes D21-D26. When voltage is applied to inverter 44, the electronic control unit 70 adjusts the ratio of on-times for each pair of transistors T21-T26, thereby forming a rotating magnetic field in the three-phase coil and driving the motor 42 to rotate.

[0015] As shown in Figure 1, the battery 50 is connected to the power line 54 together with the inverters 34 and 44. This battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery.

[0016] The electronic control unit 70 includes a microcomputer with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. The electronic control unit 70 receives signals from various sensors via input ports. For example, the electronic control unit 70 receives rotational positions θma and θmb from rotational position sensors 32a and 42a that detect the rotational position of the rotors of motors 32 and 42, and phase currents Iua, Iva, Iub, and Ivb from current sensors 32u, 32v, 42u, and 42v that detect the phase currents of the U and V phases of motors 32 and 42. The electronic control unit 70 also receives voltage Vb from a voltage sensor attached between the terminals of the battery 50 and current Ib from a current sensor attached to the output terminal of the battery 50. The electronic control unit 70 also receives a start signal from the start switch 80 and a shift position SP from a shift position sensor 82 that detects the operating position of the shift lever 81. The electronic control unit 70 also receives inputs from the accelerator pedal position sensor 84, which detects the amount the accelerator pedal 83 is pressed, the brake pedal position BP from the brake pedal position sensor 86, which detects the amount the brake pedal 85 is pressed, the vehicle speed V from the vehicle speed sensor 87, and the steering angle θst from the steering angle sensor 88.

[0017] The electronic control unit 70 outputs various control signals via its output ports. For example, the electronic control unit 70 outputs switching control signals to transistors T11-T16 and T21-T26 of inverters 34 and 44. Based on the rotational positions θma and θmb of the rotors of motors 32 and 42 from rotational position sensors 32a and 42a, the electronic control unit 70 calculates the electrical angles θea and θeb, angular velocities ωma and ωmb, and rotational speeds Nma and Nmb of motors 32 and 42.

[0018] In the electric vehicle 20 of the embodiment configured in this way, the electronic control unit 70 first sets the required torque Td* for running based on the accelerator opening Acc and the vehicle speed V. Subsequently, the torque distribution ratios Da and Db (Da + Db = 1) of the motors 32 and 42 are set based on the steering angle θst and the like. Then, the torque commands Tma* and Tmb* of the motors 32 and 42 are set by multiplying the required torque Td* by the torque distribution ratios Da and Db. When the torque commands Tma* and Tmb* are set in this way, switching control of the transistors T11 to T16 and T21 to T26 of the inverters 34 and 44 is performed so that the motors 32 and 42 are driven by the torque commands Tma* and Tmb*.

[0019] Here, the control of the inverters 34 and 44 by the electronic control unit 70 will be described. The inverters 34 and 44 are basically controlled by pulse width modulation control (PWM control). In the control of the inverters 34 and 44, first, assuming that the sum of the phase currents of each phase of the motors 32 and 42 is the value 0, the phase currents Iua and Iub of the U phase and the phase currents Iva and Ivb of the V phase are converted to the d-axis current Ida and Idb and the q-axis current Iqa and Iqb in the dq coordinate system with the d-axis and q-axis as coordinate axes using the electrical angles θea and θeb of the motors 32 and 42 (three-phase to two-phase conversion). Subsequently, based on the torque commands Tma* and Tmb* of the motors 32 and 42, the current effective value commands Ira* and Irb* and the current advance angle value commands φia* and φib* of the current vector in the dq coordinate system are set by the setting processing routine described later. The current effective value commands Ira* and Irb* are the command values of the effective value of the current supplied by the motors 32 and 42, and the current advance angle value commands φia* and φib* are the command values of the angle (advance angle value) with respect to the q-axis of the current supplied to the motor 32.

[0020] When the effective current commands Ira*, Irb* and the current advance angle commands φia*, φib* are set in this way, based on the effective current commands Ira*, Irb* and the current advance angle commands φia*, φib*, the d-axis current commands Ida*, Idb* and the q-axis current commands Iqa*, Iqb* are set. This process is carried out in consideration of the fact that the effective current commands Ira*, Irb* are obtained as the square root of the sum of the squares of the d-axis current commands Ida*, Idb* and the q-axis current commands Iqa*, Iqb*, and the fact that the current advance angle commands φia*, φib* are obtained as the angle (advance angle value) of the current vector in the dq coordinate system (the vector with the d-axis current commands Ida*, Idb* and the q-axis current commands Iqa*, Iqb* as components) with respect to the q-axis.

[0021] When the d-axis current commands Ida*, Idb* and the q-axis current commands Iqa*, Iqb* are set in this way, the d-axis voltage commands Vda*, Vdb* and the q-axis voltage commands Vqa*, Vqb* are set so that the differences between the d-axis current commands Ida*, Idb* and the q-axis current commands Iqa*, Iqb* and the d-axis currents Ida, Idb and the q-axis currents Iqa, Iqb are canceled out. Subsequently, using the electrical angles θea, θeb of the motors 32, 42, the d-axis voltage commands Vda*, Vdb* and the q-axis voltage commands Vqa*, Vqb* are coordinate-transformed (two-phase to three-phase conversion) into the U-phase voltage commands Vua*, Vub*, the V-phase voltage commands Vva*, Vvb*, and the W-phase voltage commands Vwa*, Vwb*. Then, by comparing the U-phase voltage commands Vua*, Vub*, the V-phase voltage commands Vva*, Vvb*, the W-phase voltage commands Vwa*, Vwb*, and the carrier voltage, PWM signals for the transistors T11~T16, T21~T26 are generated, and switching control of the transistors T11~T16, T21~T26 is performed using the PWM signals for the transistors T11~T16, T21~T26.

[0022] Next, the operation of the electric vehicle 20 of the embodiment will be described, in particular the process of setting the current effective value commands Ira*, Irb* and current advance value commands φia*, φib* for the motors 32 and 42. Figure 3 is a flowchart of an example of a setting process routine executed by the electronic control unit 70. This routine is executed repeatedly.

[0023] When this routine is executed, the electronic control unit 70 first calculates the difference between the torque commands Tma* and Tmb* of motors 32 and 42 (the absolute value of the value obtained by subtracting one from the other), ΔTm (step S100), and also calculates the difference between the rotational speeds Nma and Nmb of motors 32 and 42 (the absolute value of the value obtained by subtracting one from the other), ΔNm (step S110).

[0024] Next, it is determined whether the difference ΔTm is less than or equal to the threshold ΔTmth (step S120), and whether the difference ΔNm is less than or equal to the threshold ΔNmth (step S130). Here, the threshold ΔTmth is a threshold used to determine whether the torque command Tma* of motor 32 and the torque command Tmb* of motor 42 are close together, and is predetermined by experimentation or analysis, for example, a value of several tens of rpm is used. The threshold ΔNmth is a threshold used to determine whether the rotational speed Nma of motor 32 and the rotational speed Nmb of motor 42 are close together, and is predetermined by experimentation or analysis, for example, a value of several tens of Nm is used. The inventors have confirmed that when the torque command Tma* of motor 32 and the torque command Tmb* of motor 42 are close together and the rotational speed Nma of motor 32 and the rotational speed Nmb of motor 42 are close together, a humming sound may be generated based on the sound and vibration generated by motors 32 and 42, which may cause discomfort to the occupants. The threshold values ​​ΔNmth and ΔTmth are predetermined through experiments, analyses, etc., as upper limits to the range of difference ΔNm and difference ΔTm, respectively, within which a beat sound can be produced.

[0025] If it is determined in step S120 that the difference ΔTm is greater than the threshold ΔTmth, or if it is determined in step S130 that the difference ΔNm is greater than the threshold ΔNmth, it is determined that no humming sound will be produced. In this case, the current RMS value commands Ira*, Irb* and current advance value commands φia*, φib* are set using the first setting method (step S140), and this routine is terminated.

[0026] If it is determined in step S120 that the difference ΔTm is less than or equal to the threshold ΔTmth, and in step S130 that the difference ΔNm is less than or equal to the threshold ΔNmth, then it is determined that a humming sound may be produced. In this case, the current RMS value commands Ira*, Irb* and current advance value commands φia*, φib* are set using the second setting method (step S150), and this routine is terminated.

[0027] Here, the first and second setting methods will be explained. Figure 4 is an explanatory diagram showing an example of the relationship between the torque commands Tma*, Tmb* and torque fluctuations TFma, TFmb of motors 32 and 42, and the current advance value commands φia*, φib* and current RMS value commands Ira*, Irb*. Figure 4(A) is an explanatory diagram showing an example of the relationship between the torque commands Tma*, Tmb* and current advance value commands φia*, φib* and current RMS value commands Ira*, Irb* of motors 32 and 42. Figure 4(B) is an explanatory diagram showing an example of the relationship between the torque fluctuations TFma, TFmb and current advance value commands φia*, φib* and current RMS value commands Ira*, Irb* of motors 32 and 42. As described above, motors 32 and 42 are configured to have the same specifications. Therefore, in this embodiment, a common relationship is used for motors 32 and 42.

[0028] In the first setting method, the relationship shown in Figure 4(A) and the motors 32 and 42 are set using torque commands Tma* and Tmb* to realize the torque commands Tma* and Tmb* while minimizing the effective current command Ira* and Irb*, and the current advance value command φia* and φib* are set.

[0029] In the second setting method, the current RMS value commands Ira*, Irb* and current advance value commands φia*, φib* are set according to either the first or second pattern. In the first pattern, the current RMS value commands Ira* and current advance value commands φia* are set using Figures 4(A) and 4(B) and the torque command Tma* of motor 32 to realize the torque command Tma* while minimizing the torque fluctuation TFma of motor 32. The current RMS value commands Irb* and current advance value commands φib* are set using Figures 4(A) and 4(B) and the torque command Tmb* of motor 42 to realize the torque command Tmb* while ensuring that the difference ΔTFm between the torque fluctuations TFma and TFmb of motors 32 and 42 is greater than or equal to the threshold ΔTFmth. The threshold ΔTFmth is determined in advance through experiments or analyses to suppress the generation of humming noise. In the second pattern, using Figures 4(A) and 4(B) and the torque command Tmb* for motor 42, the RMS current command Irb* and the current advance command φib* are set so that the torque fluctuation FTmb of motor 42 is minimized while realizing the torque command Tmb*. Using Figures 4(A) and 4(B) and the torque command Tma* for motor 32, the RMS current command Ira* and the current advance command φia* are set so that the difference ΔTFm is greater than or equal to the threshold ΔTFmth while realizing the torque command Tma*. Note that either the first or second pattern may be used at all times, or they may be switched periodically (for example, at predetermined intervals).

[0030] The inventors, through experiments and analyses, confirmed that when the difference ΔTm is less than or equal to the threshold ΔTmth and the difference ΔNm is less than or equal to the threshold ΔNmth, the greater the torque fluctuation of motors 32 and 42, the more likely it is that the noise and vibration of motors 32 and 42 will increase, and when the noise and vibration of motors 32 and 42 are of a similar magnitude, a humming noise is more likely to occur. In the embodiment, when the difference ΔTm is less than or equal to the threshold ΔTmth and the difference ΔNm is less than or equal to the threshold ΔNmth, by setting the effective current value commands Ira*, Irb* and the advance current value commands φia*, φib* so that the difference ΔTFm is greater than or equal to the threshold ΔTFmth, it is possible to make the noise and vibration of one motor 32 or 42 more noticeable while making the noise and vibration of the other less noticeable. As a result, the generation of humming noise can be suppressed. That is, it is possible to suppress the generation of humming noise while suppressing the increase in manufacturing costs compared to changing the hardware configuration of the electric vehicle 20. By suppressing the generation of humming noises, discomfort to the occupants can be reduced. Furthermore, by setting the current effective value commands Ira*, Irb* and current advance value commands φia*, φib* so that the torque fluctuation of motor 32 is minimized in the first pattern and the torque fluctuation of motor 42 is minimized in the second pattern, the aforementioned noise and vibration of motors 32 and 42 can be made even smaller and less noticeable. In order to prevent the aforementioned noise and vibration of motors 32 and 42 from becoming too loud, it is preferable to make the difference ΔTFm as small as possible within a range greater than or equal to the threshold ΔTFmth, for example, so that the difference ΔTFm is equal to the threshold ΔTFmth.

[0031] In the electric vehicle 20 of this embodiment described above, when the difference ΔTm between the torque commands Tma* and Tmb* of motors 32 and 42 is less than or equal to the threshold ΔTmth, and the difference ΔNm between the rotational speeds Nma and Nmb of motors 32 and 42 is less than or equal to the threshold ΔNmth, the effective current value commands Ira*, Irb* and current advance value commands φia*, φib* are set so that the difference ΔTFm is greater than or equal to the threshold ΔTFmth. This makes it possible to amplify and highlight the sound and vibration of one of the motors 32 and 42 while reducing and making the sound and vibration of the other less noticeable, thereby suppressing the generation of humming noise. In other words, it is possible to suppress the generation of humming noise while suppressing an increase in manufacturing costs compared to changing the hardware configuration of the electric vehicle 20.

[0032] In the embodiments described above, the electronic control unit 70 sets the effective current value commands Ira*, Irb* and the current advance value commands φia*, φib* so that when the difference ΔTm is less than or equal to the threshold ΔTmth and the difference ΔNm is less than or equal to the threshold ΔNmth, the torque fluctuation TFma of the motor 32 is minimized in the first pattern, and the torque fluctuation TFmb of the motor 42 is minimized in the second pattern. However, it is not limited to this. For example, the effective current value commands Ira*, Irb* and the current advance value commands φia*, φib* may be set so that in the first pattern the torque fluctuation TFma of the motor 32 falls within a predetermined range including the minimum, and in the second pattern the torque fluctuation TFmb of the motor 42 falls within this predetermined range.

[0033] In the embodiment described above, a battery 50 was used as the energy storage device, but the invention is not limited to this. For example, a capacitor or the like may be used as the energy storage device in addition to or instead of the battery 50.

[0034] In the embodiment described above, the motors 32 and 42 were mounted in the left and right drive wheels 22a and 22b, but are not limited to this. For example, the motors 32 and 42 may be mounted on the left and right axles.

[0035] In the embodiment described above, the electric vehicle 20 includes motors 32 and 42 mounted in the left and right drive wheels 22a and 22b, inverters 34 and 44 that drive the motors 32 and 42, and a battery 50 connected to the inverters 34 and 44 via a power line 52, as shown in Figure 1, but is not limited to this. For example, as shown in the modified electric vehicle 120 in Figure 5, it may include a motor 132 connected to the front wheels 122a and 122b, a motor 142 connected to the rear wheels 122c and 122d, inverters 134 and 144 that drive the motors 132 and 142, and a battery 150 connected to the inverters 134 and 144 via a power line 152.

[0036] In the embodiment described above, the electric vehicle 20 was configured to have two motors 32 and 42, but it is not limited to this. For example, it may be configured as a hybrid vehicle further equipped with an engine in addition to the two motors, or as a fuel cell vehicle equipped with a fuel cell in addition to the two motors.

[0037] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, motors 32 and 42 correspond to the "first and second motors," inverters 34 and 44 correspond to the "first and second inverters," and the electronic control unit 70 corresponds to the "control device."

[0038] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0039] While embodiments for implementing this disclosure have been described above, this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0040] This disclosure can be used in industries such as electric vehicle manufacturing. [Explanation of symbols]

[0041] 20,120 Electric vehicle, 22a,22b Drive wheels, 32,42,132,142 Motor, 32a,42a Rotation position sensor, 32u,32v,42u,42v Current sensor, 34,44,134,144 Inverter, 50,150 Battery, 54,154 Power line, 70 Electronic control unit, 80 Start switch, 81 Shift lever, 82 Shift position sensor, 83 Accelerator pedal, 84 Accelerator pedal position sensor, 85 Brake pedal, 86 Brake pedal position sensor, 87 Vehicle speed sensor, D11~D16, D21~D26 Diode, T11~T16, T21~T26 Transistor.

Claims

1. First and second motors, The first and second inverters drive the first and second motors, respectively, An electric vehicle comprising: a control device that controls the first and second inverters by setting first and second RMS current value commands and first and second current advance angle value commands for first and second current vectors in a dq coordinate system with the d axis and q axis as coordinate axes, based on first and second torque commands of the first and second motors, The control device sets the first and second effective current command and the first and second current advance value command so that the torque difference, which is the difference between the first and second torque commands, is less than or equal to a predetermined torque difference, and the rotational speed difference, which is the difference between the first and second rotational speeds of the first and second motors, is less than or equal to a predetermined rotational speed difference, so that the torque fluctuation difference, which is the difference between the first and second torque fluctuations of the first and second motors, is greater than or equal to a predetermined torque fluctuation difference. Electric car.

2. The electric vehicle according to claim 1, The control device sets the first and second current effective value commands and the first and second current advance value commands so that one of the first and second torque fluctuations is minimized. Electric car.

3. An electric vehicle according to claim 1 or 2, The first and second motors are mounted to drive the left and right drive wheels, respectively. Electric car.

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