Drive device for electric vehicle

Abstract

To suppress a certain degree of large electromagnetic noise from being transmitted to a driving wheel via a power transmission path accompanying discharge of a shaft voltage of a motor shaft when the discharge occurs, while suppressing an increase in size of a device.SOLUTION: An electric vehicle drive device includes a motor including a rotor attached to a motor shaft and a stator around which a motor coil is wound, an inverter configured to drive the motor by switching of a switching element, a shaft voltage sensor configured to detect a shaft voltage of the motor shaft, a choke coil attached to a power transmission path from the motor shaft to a drive wheel, and an application control device configured to apply a current for canceling at least a part of electromagnetic noise transmitted to the drive wheel via the power transmission path to the choke coil when a predetermined pulsation of the shaft voltage is detected based on a detection value of the shaft voltage sensor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a drive device for an electric vehicle. [Background technology]

[0002] A conventional electric vehicle drive system includes a motor having a rotor attached to the motor shaft and a stator wound with a motor coil; an inverter for driving the motor; a power transmission coupling (a splined portion and a gear meshing portion) disposed in a power transmission path from the motor shaft to the drive wheels and providing electrical resistance downstream of the motor shaft; and a ground connection body electrically connecting a downstream portion of the power transmission path from the power transmission coupling body to the vehicle body (see, for example, Patent Document 1). In this electric vehicle drive system, the ground connection body includes a sliding brush that slides against the shaft end of a countershaft of a gear reducer in the power transmission path, a lead wire electrically connecting the sliding brush to a gear case of the gear reducer, and a connection line electrically connecting the gear case to the vehicle body. The shaft end is covered by a brush cover fixed to the gear case, and the brush cover defines a brush chamber that communicates with the internal chamber of the gear case. This electric vehicle drive system reduces noise transmission from the inverter through the motor toward the power transmission path, thereby reducing high-frequency noise emitted to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-147293 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described electric vehicle drive device, the brush chamber and the like are provided separately from the internal chamber of the gear case, which increases the space required and leads to an increase in the size of the device, which may result in a decrease in the space available in the passenger compartment.

[0005] The main purpose of the electric vehicle drive device disclosed herein is to suppress the transmission of a relatively large amount of electromagnetic noise to the drive wheels via the power transmission path when a discharge of the axial voltage of the motor shaft occurs, while suppressing an increase in the size of the device. [Means for solving the problem]

[0006] The electric vehicle drive device of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The electric vehicle drive device of the present disclosure is a motor having a rotor attached to a motor shaft and a stator wound with a motor coil; an inverter that drives the motor by switching a switching element; a shaft voltage sensor for detecting a shaft voltage of the motor shaft; a choke coil attached to a power transmission path from the motor shaft to the drive wheels; an application control device that applies a current to the choke coil when a predetermined pulsation of the shaft voltage is detected based on the detection value of the shaft voltage sensor, in order to cancel at least a part of the electromagnetic noise transmitted to the drive wheels via the power transmission path; The gist of the project is to provide the following:

[0008] In the electric vehicle drive device disclosed herein, a choke coil is attached to the power transmission path from the motor shaft to the drive wheels. When a predetermined pulsation in the shaft voltage is detected based on the detected value of a shaft voltage sensor that detects the shaft voltage of the motor shaft, a current is applied to the choke coil to cancel out at least a portion of the electromagnetic noise transmitted to the drive wheels via the power transmission path. When the shaft voltage of the motor shaft discharges, a relatively large pulsation in the shaft voltage occurs. Therefore, the above-described control can suppress transmission of a certain amount of electromagnetic noise to the drive wheels via the power transmission path due to the discharge of the shaft voltage of the motor shaft, while suppressing an increase in the size of the device. Here, the "predetermined pulsation in the shaft voltage" may include only the shaft voltage pulsation caused by the shaft voltage discharge, or may include shaft voltage pulsation caused by the switching of the inverter switching elements in addition to the shaft voltage pulsation caused by the shaft voltage discharge.

[0009] In the electric vehicle drive device disclosed herein, the application control device may detect the predetermined pulsation of the shaft voltage when a detected value of the shaft voltage or a filtered value obtained by filtering the detected value reaches or exceeds a threshold value. In this case, the threshold value may be predetermined as a value that is greater than the detected value or the filtered value when the inverter is switching and smaller than the detected value or the filtered value when the shaft voltage is discharging.

[0010] In the electric vehicle drive device of the present disclosure, the motor shaft may be connected to the drive wheels via a gear mechanism, a differential gear, and a drive shaft, and the choke coil may be attached to any of the motor shaft, the shaft of the gear mechanism, or the drive shaft. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle 20 equipped with an electric vehicle drive device according to an embodiment of the present disclosure. [Figure 2]2 is a schematic diagram of an electric drive system including a motor 22 and an inverter 50, and an ECU 70. FIG. [Figure 3] 4 is a flowchart showing an example of a processing routine executed by an ECU 70. [Figure 4] 4 is an explanatory diagram showing an example of the state of the shaft voltage Vs and filtered value Vsf of the motor shaft 25. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] A mode (embodiment) for carrying out the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic configuration diagram of an electric vehicle 20 equipped with an electric vehicle drive device according to an embodiment of the present disclosure. Fig. 2 is a schematic configuration diagram of an electric drive system including a motor 22 and an inverter 50, and an electronic control unit (hereinafter referred to as "ECU") 70. As shown in Figs. 1 and 2, the electric vehicle 20 according to the embodiment includes the motor 22, a gear mechanism 30, a differential gear 40, drive shafts 42a and 42b, the inverter 50, a high-voltage battery 58, a low-voltage battery 60, a DC / DC converter 64, and an ECU 70 (voltage application control device). The motor 22, gear mechanism 30, differential gear 40, drive shafts 42a, 42b, and each of the bearings 27, 28, 35, 36, 44a, and 44b described below are made of metal (conductors), and the motor 22, gear mechanism 30, differential gear 40, portions of the drive shafts 42a and 42b (portions on the differential gear 40 side), and each of the bearings 27, 28, 35, 36, 44a, and 44b are housed in a case (housing) 46.

[0013] Motor 22 is configured as a synchronous generator motor and includes, for example, a rotor 23 having a permanent magnet embedded in a rotor core, and a stator 24 having a three-phase (U-phase, V-phase, W-phase) coil wound around a stator core. Rotor 23 is attached to motor shaft 25. Motor shaft 25 is rotatably supported by case 46 via bearings 27 and 28.

[0014] The gear mechanism 30 includes a counter shaft 31 coaxially connected to the motor shaft 25 by spline fitting or the like, a counter gear 32 attached to the counter shaft 31, and a final gear (differential ring gear) 33 meshing with the counter gear 32 and connected to a differential gear 40. The counter shaft 31 is connected to the motor shaft 25 by spline fitting or the like and rotatably supported by a case 46 via bearings 35 and 36. The differential gear 40 is connected to drive wheels DWa and DWb via drive shafts 42a and 42b. The drive shafts 42a and 42b are rotatably supported by the case 46 via bearings 44a and 44b, respectively. Choke coils 48a and 48b are attached to the drive shafts 42a and 42b, respectively.

[0015] As shown in FIG. 2, the inverter 50 is connected to a high-voltage power line 54. The inverter 50 includes six transistors T11-T16 as switching elements and six diodes D11-D16 connected in parallel to the six transistors T11-T16, respectively. The transistors T11-T16 are arranged in pairs, two at a time, on the source side and two at the sink side of the positive and negative lines of the high-voltage power line 54. Each of the connection points of two transistors in each pair of the transistors T11-T16 is connected to one of the three-phase (U-phase, V-phase, W-phase) coils of the motor 22. A smoothing capacitor 56 is connected to the high-voltage power line 54.

[0016] High-voltage battery 58 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery with a rated voltage of several hundred volts, and is connected to high-voltage power line 54. Low-voltage battery 60 is configured as, for example, a lithium-ion secondary battery or a lead-acid battery with a rated voltage of 12 volts, and is connected to low-voltage power line 62 together with ECU 70 and various auxiliary devices. DC / DC converter 64 steps down the power on high-voltage power line 54 and supplies the power to low-voltage power line 62.

[0017] The ECU 70 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and logic ICs. The ECU 70 receives signals from various sensors. Examples of the sensors include a rotational position sensor 22a that detects the rotational position θm of the rotor of the motor 22, current sensors 22u, 22v, and 22w that detect phase currents Iu, Iv, and Iw flowing through the respective phases (U, V, and W) of the motor 22, and a shaft voltage sensor 25s that detects a shaft voltage Vs of the motor shaft 25. Although not shown, other sensors may also be included: a shift position sensor that detects a shift position SP of the shift lever, an accelerator pedal position sensor that detects an accelerator opening Acc that indicates the amount of depression of the accelerator pedal, a brake pedal position sensor that detects a brake pedal position BP that indicates the amount of depression of the brake pedal, and a vehicle speed sensor that detects the vehicle speed V. The shaft voltage Vs of the motor shaft 25 includes a shaft voltage to ground. The ECU 70 controls the switching of the transistors T11 to T16 of the inverter 50, the energization of the choke coils 48a and 48b, and the DC / DC converter 64.

[0018] In the electric vehicle 20 of this embodiment configured in this manner, the ECU 70 sets the required torque Td* required for driving based on the accelerator opening Acc and the vehicle speed V, sets the torque command Tm* for the motor 22 so that the vehicle drives with the set required torque Td*, and controls the switching of the transistors T11 to T16 of the inverter 50 so that the motor 22 is driven with the torque command Tm*.

[0019] Next, the operation of the electric vehicle 20 according to this embodiment, in particular the energization control of the choke coils 48a, 48b, will be described. Figure 3 is a flowchart showing an example of a processing routine executed by the microcomputer of the ECU 70. This routine is executed repeatedly.

[0020] When this routine is executed, the ECU 70 first performs filtering on the shaft voltage Vs of the motor shaft 25 detected by the shaft voltage sensor 25s to calculate a filtered value Vsf (step S100). Specifically, this processing performs high-pass filtering on the shaft voltage Vs of the motor shaft 25 to extract frequency components higher than a predetermined frequency, thereby calculating the filtered value Vsf. FIG. 4 is an explanatory diagram showing an example of the shaft voltage Vs and filtered value Vsf of the motor shaft 25. As can be seen from FIG. 4, pulsation occurs in the shaft voltage Vs and filtered value Vsf due to the switching of the transistors T11 to T16 of the inverter 50 and the discharge of the shaft voltage of the motor shaft 25. The pulsation of the shaft voltage Vs and filtered value Vsf due to the discharge of the shaft voltage of the motor shaft 25 is larger than the pulsation of the shaft voltage Vs and filtered value Vsf due to the switching of the transistors T11 to T16. The shaft voltage is discharged, for example, when a current flows from the power transmission path from the motor shaft 25 to the drive wheels DWa and DWb to the case 46 via the bearings 27, 28, 35, and 36. In the figure, "Vsfref" will be described later.

[0021] Once the filtered value Vsf is calculated in this manner, the calculated filtered value Vsf is compared with a threshold value Vsfref (step S110). Here, the threshold value Vsfref is a threshold value for detecting a discharge of the shaft voltage of the motor shaft 25 (a predetermined pulsation of the shaft voltage resulting from this). The threshold value Vsfref is determined in advance through experimentation, analysis, machine learning, or the like as a value that is greater than the maximum value of the filtered value Vsf when the transistors T11 to T16 of the inverter 50 are switched and smaller than the maximum value of the filtered value Vsf when the shaft voltage of the motor shaft 25 is discharged. If the filtered value Vsf is less than the threshold value Vsfref, this routine ends without detecting a discharge of the shaft voltage of the motor shaft 25.

[0022] If the filtered value Vsf is equal to or greater than the threshold value Vsfref in step S110, a discharge of the shaft voltage of motor shaft 25 is detected, target application currents Ica* and Icb* to be applied to choke coils 48a and 48b are set (step S120), the set target application currents Ica* and Icb* are applied to choke coils 48a and 48b (step S130), and this routine ends. Here, the target application currents Ica* and Icb* are determined as currents (current waveforms) for canceling out at least a portion of the electromagnetic noise that, when a discharge of the shaft voltage of motor shaft 25 occurs, is transmitted to drive wheels DWa and DWb via the power transmission path from motor shaft 25 to drive wheels DWa and DWb. The target applied currents Ica* and Icb* may use a predetermined uniform frequency or current value, or may be determined based on the maximum value of the filtered value Vsf, the amount of change (rate of change) per unit time of the filtered value Vsf when the filtered value Vsf reaches or exceeds the threshold value Vsfref, etc. By such control, when a discharge of the shaft voltage of the motor shaft 25 occurs, it is possible to suppress transmission of a certain level of electromagnetic noise to the drive wheels DWa and DWb via the power transmission path due to the discharge.

[0023] In the electric vehicle 20 according to the embodiment described above, the shaft voltage Vs of the motor shaft 25 detected by the shaft voltage sensor 25s is filtered to calculate the filtered value Vsf. When the calculated filtered value Vsf is equal to or greater than the threshold value Vsfref, a discharge of the shaft voltage of the motor shaft 25 is detected. Target applied currents Ica* and Icb* to be applied to the choke coils 48a and 48b are set, and the set target applied currents Ica* and Icb* are applied to the choke coils 48a and 48b. The target applied currents Ica* and Icb* are determined as currents (current waveforms) for canceling at least a portion of the electromagnetic noise that, when a discharge of the shaft voltage of the motor shaft 25 occurs, is transmitted to the drive wheels DWa and DWb via the power transmission path from the motor shaft 25 to the drive wheels DWa and DWb. This prevents a certain level of electromagnetic noise from being transmitted to the drive wheels DWa and DWb via the power transmission path when a discharge of the shaft voltage of the motor shaft 25 occurs. Moreover, compared to the device disclosed in Patent Document 1, where a brush chamber and the like are provided separately from the internal chamber of the gear case, the device does not need to be large.

[0024] In the above-described embodiment, a discharge of the shaft voltage of the motor shaft 25 is detected when the filtered value Vsf calculated by filtering the shaft voltage Vs of the motor shaft 25 detected by the shaft voltage sensor 25s is equal to or greater than the threshold value Vsfref. However, a discharge of the shaft voltage of the motor shaft 25 may also be detected when the shaft voltage Vs of the motor shaft 25 is equal to or greater than the threshold value Vsref. The threshold value Vsref is determined in advance by experiment, analysis, machine learning, or the like as a value that is greater than the maximum value of the shaft voltage Vs when the transistors T11 to T16 of the inverter 50 are switched and smaller than the maximum value of the shaft voltage Vs when the shaft voltage of the motor shaft 25 is discharged.

[0025] In the above-described embodiment, a discharge of the shaft voltage of the motor shaft 25 is detected when the filtered value Vsf is equal to or greater than the threshold value Vsfref. However, instead, a predetermined pulsation of the shaft voltage may be detected when the filtered value Vsf is equal to or greater than a threshold value Vsfref2 that is lower than the threshold value Vsfref. The threshold value Vsfref2 is determined in advance through experimentation, analysis, machine learning, or the like as a value slightly smaller than the maximum value of the filtered value Vsf when the transistors T11 to T16 of the inverter 50 are switched. In this case, the predetermined pulsation of the shaft voltage includes not only fluctuations in the shaft voltage caused by the discharge of the shaft voltage of the motor shaft 25 but also fluctuations in the shaft voltage caused by the switching of the transistors T11 to T16 of the inverter 50. In this case, the target applied currents Ica* and Icb* may be set in consideration of the magnitude relationship between the maximum value of the filtered value Vsf and the threshold value Vsfref, or may be set uniformly regardless of this magnitude relationship. Just as threshold value Vsfref2 may be used instead of threshold value Vsfref, threshold value Vsref2 may be used instead of the above-described threshold value Vsref. Threshold value Vsref2 is determined in advance by experiment, analysis, machine learning, or the like as a value slightly smaller than the maximum value of shaft voltage Vs when transistors T11 to T16 of inverter 50 are switched.

[0026] In the above-described embodiment, the choke coils 48a, 48b are attached to the drive shafts 42a, 42b. However, this is not limited to this, and any choke coil may be attached to the power transmission path from the motor shaft 25 to the drive wheels DWa, DWb. For example, a choke coil may be attached to only one of the drive shafts 42a, 42b, a choke coil may be attached to the counter shaft 31, or a choke coil may be attached to the motor shaft 25.

[0027] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problems" section will be described below. In the embodiment, the motor shaft 25 corresponds to the "motor shaft," the rotor 23 corresponds to the "rotor," the stator 24 corresponds to the "stator," the motor 22 corresponds to the "motor," the inverter 50 corresponds to the "inverter," the shaft voltage sensor 25s corresponds to the "shaft voltage sensor," the choke coils 48a and 48b correspond to the "choke coils," and the ECU 70 corresponds to the "voltage control device." In addition, the gear mechanism 30 corresponds to the "gear mechanism," the differential gear 40 corresponds to the "differential gear," and the drive shafts 42a and 42b correspond to the "drive shafts."

[0028] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0029] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0030] The present disclosure is applicable to industries such as the manufacturing industry of drive devices for electric vehicles. [Explanation of symbols]

[0031] 20 electric vehicle, 22 motor, 22a rotational position sensor, 22u, 22v, 22w current sensors, 23 rotor, 24 stator, 25 motor shaft, 25s shaft voltage sensor, 27, 28, 35, 36, 44a, 44b bearings, 30 gear mechanism, 31 counter shaft, 32 counter gear, 40 differential gear, 42a drive shaft, 46 case, 48a, 48b choke coil, 50 inverter, 54 high voltage power line, 56 capacitor, 58 high voltage battery, 60 low voltage battery, 62 low voltage power line, 64 DC / DC converter, 70 ECU, D11 to D16 diodes, T11 to T16 transistors.

Claims

1. a motor having a rotor attached to a motor shaft and a stator wound with a motor coil; an inverter that drives the motor by switching a switching element; a shaft voltage sensor for detecting a shaft voltage of the motor shaft; a choke coil attached to a power transmission path from the motor shaft to the drive wheels; an application control device that applies a current to the choke coil when a predetermined pulsation of the shaft voltage is detected based on the detection value of the shaft voltage sensor, in order to cancel at least a part of the electromagnetic noise transmitted to the drive wheels via the power transmission path; A drive device for an electric vehicle comprising:

2. 2. The electric vehicle drive device according to claim 1, The voltage application control device detects the predetermined pulsation of the shaft voltage when the detected value of the shaft voltage or a filtered value obtained by filtering the detected value reaches a threshold value or more. Drive unit for electric vehicles.

3. 3. The electric vehicle drive device according to claim 2, The threshold value is predetermined as a value that is greater than the detected value or the filtered value when the inverter is switched and is smaller than the detected value or the filtered value when the shaft voltage is discharged. Drive unit for electric vehicles.

4. 4. The electric vehicle drive device according to claim 1, the motor shaft is connected to the drive wheels via a gear mechanism, a differential gear, and a drive shaft; the choke coil is attached to any one of the motor shaft, the shaft of the gear mechanism, and the drive shaft; Drive unit for electric vehicles.

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