Drive unit

Abstract

To provide a driving device that can prevent vibration while preventing cost increase and weight increase.SOLUTION: Provided is a driving device 20 including: a motor MG including a stator 30 having a stator core 32 and a stator coil 34, and a rotor 40; a drive gear 52 connected to a rotor shaft 46 which is a shaft of the rotor 40; and an electronic control device 90 that controls a driving current flowing in the stator coil 34, in which (a) the number of teeth Z of the drive gear 52 is set such that an order of a torque ripple produced in the motor MG and an order of variation in an engaging torque Tgear produced in the drive gear 52 match, and (b) the electronic control device 90 executes harmonic superposition control of, in a case where the magnitude of vibration of the drive gear 52 resulting from the torque ripple and the variation in the engaging torque Tgear exceeds a predetermined determination value, superposing a harmonic current on a fundamental wave of the driving current such that the magnitude of vibration of the drive gear 52 decreases.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drive device that includes a gear connected to the shaft of a rotor of an electric motor and a control device that controls the drive current of the electric motor. [Background technology]

[0002] There is known a drive device that performs control to avoid resonance caused by torque ripple and fluctuations in meshing torque by matching the order of torque ripple generated in an electric motor with the order of fluctuations in meshing torque generated in a gear connected to the shaft of the rotor of the electric motor. For example, the device described in Patent Document 1 is such a device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-118171 Summary of the Invention [Problem to be solved by the invention]

[0004] The drive device described in Patent Document 1 is provided with a clutch that connects and disconnects the shaft of the rotor of the electric motor and the gear. Vibration in the drive device is suppressed by controlling the operation of the clutch so that the phase of the rotor's magnetic poles and the phase of the gear meshing are in opposite phase. As such, the drive device described in Patent Document 1 requires a clutch, and therefore a location for mounting the clutch must be secured, resulting in increased costs and weight.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a drive device that can suppress vibration while suppressing increases in cost and weight. [Means for solving the problem]

[0006] The gist of the present invention is a drive device comprising an electric motor including a stator having a stator core and a stator coil and a rotor, a gear connected to the shaft of the rotor, and a control device that controls a drive current flowing through the stator coil, wherein (a) the number of teeth of the gear is set so that the order of torque ripple generated in the electric motor matches the order of the fluctuations in meshing torque generated in the gear, and (b) when the magnitude of vibration of the gear caused by the torque ripple and the fluctuations in meshing torque exceeds a predetermined judgment value, the control device performs harmonic superposition control that superimposes a harmonic current on the fundamental wave of the drive current so as to reduce the magnitude of the vibration of the gear. [Effects of the Invention]

[0007] According to the drive device of the present invention, (a) the number of teeth of the gears is set so that the order of torque ripple generated by the electric motor matches the order of fluctuations in meshing torque generated by the gears, and (b) when the magnitude of gear vibration caused by the torque ripple and fluctuations in meshing torque exceeds a predetermined threshold, the control device executes harmonic superposition control to superimpose harmonic currents on the fundamental wave of the drive current so as to reduce the magnitude of gear vibration. By executing harmonic superposition control, gear vibration caused by torque ripple generated by the electric motor and fluctuations in meshing torque generated by the gears is suppressed, thereby suppressing vibration in the drive device while minimizing increases in cost and weight. For example, when such a drive device is installed in a vehicle, vehicle body vibration and interior noise are suppressed while minimizing increases in vehicle cost and weight. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a drive device according to an embodiment of the present invention. [Figure 2] 1 is an example of a partial cross-sectional view perpendicular to the axis of an electric motor in which the stator coil is a concentrated winding. [Figure 3] 1 is an example of a partial cross-sectional view perpendicular to the axis of an electric motor in which the stator coil is a distributed winding type. [Figure 4] 1A and 1B are diagrams illustrating examples of waveforms of a drive current and torque ripple in a three-phase synchronous motor. [Figure 5] 10A and 10B are diagrams illustrating vibration of a drive gear caused by torque ripple and fluctuations in meshing torque. [Figure 6] 2 is an example of a flowchart illustrating the control operation of the electronic control device shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings have been appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily accurately depicted. In this specification, the "direction parallel to the axis CL," the "circumferential direction about the axis CL," and the "radial direction about the axis CL" will be simply referred to as the "axis CL direction," the "circumferential direction," and the "radial direction," respectively. [Example]

[0010] FIG. 1 is a schematic diagram of a drive device 20 according to an embodiment of the present invention.

[0011] The drive device 20 is a drive device mounted on the vehicle 10, which may be, for example, a hybrid vehicle or an electric vehicle, for driving the vehicle. The drive device 20 includes an electric motor MG, a drive gear 52, a driven gear 54, an inverter 70, a battery 72, and an electronic control device 90.

[0012] The electric motor MG is a power source for driving the vehicle 10. The electric motor MG is, for example, a so-called motor generator having a motor function and a generator function, and is a three-phase synchronous motor. The electric motor MG is, for example, an interior permanent magnet type.

[0013] The electric motor MG includes a cylindrical stator 30 centered on an axis CL that is the center line of rotation, and a rotor 40 disposed inside the stator 30.

[0014] The rotor 40 is rotated by the rotating magnetic field generated by the stator 30. The rotor shaft 46 is made of, for example, steel. The rotor shaft 46 is a rotating shaft provided on the rotor 40, and its rotation center line is the axis line CL. The rotor shaft 46 is supported by the case 60 via bearings 62 and 64. In the direction of the axis line CL, the bearing 62 is a bearing located on one end side of the rotor shaft 46, and the bearing 64 is a bearing located on the other end side of the rotor shaft 46. The rotor shaft 46 corresponds to the "shaft" in this invention.

[0015] The drive gear 52 is a gear connected to the rotor shaft 46 so as not to rotate relative to the rotor shaft 46. The driven gear 54 is a gear that meshes with the drive gear 52. The drive gear 52 and the driven gear 54 form a pair of gear pairs 50. The driven gear 54 is connected to drive wheels (not shown). The MG torque Tmg [Nm], which is the output torque of the electric motor MG, is transmitted to the drive wheels via the pair of gear pairs 50. The drive gear 52 corresponds to the "gear" in this invention.

[0016] The inverter 70 is a power supply circuit provided between the electric motor MG and the battery 72, and is controlled by the electronic control device 90 to convert DC to AC and vice versa. The MG torque Tmg is controlled by the inverter 70, which is controlled by the electronic control device 90.

[0017] The battery 72 is a rechargeable secondary battery such as a lithium ion battery or a nickel-metal hydride battery, etc. The battery 72 is used to supply power to drive the electric motor MG, which is a power source, and to store electric power generated by the electric motor MG through regeneration.

[0018] The electronic control unit 90 is a controller including a control device that controls each part in the vehicle 10, and is configured to include, for example, a so-called microcomputer in which a CPU performs signal processing according to a program stored in advance in a ROM while utilizing the temporary storage function of a RAM. The electronic control unit 90 corresponds to the "control device" in the present invention.

[0019] The electronic control unit 90 receives various signals (e.g., the gear rotation speed Ngear [rpm], which is the rotation speed of the drive gear 52) based on detection values ​​from various sensors (e.g., the rotation speed sensor 80) provided on the vehicle 10.

[0020] The electronic control device 90 outputs various command signals (such as an MG control signal Smg for controlling the drive of the electric motor MG) to the devices (such as the electric motor MG) provided in the vehicle 10.

[0021] FIG. 2 is an example of a partial cross-sectional view perpendicular to the axis CL of the electric motor MG when the stator coil 34 is a concentrated winding.

[0022] The stator 30 includes a stator core 32 and a stator coil 34. The stator core 32 is cylindrical and centered on the axis CL. The inner peripheral surface of the stator core 32 is provided with a plurality of grooves, i.e., stator slots 32s, which have a depth extending radially outward and penetrate the stator core 32 in the direction of the axis CL, at equal angular intervals around the axis CL. Teeth protruding radially inward are formed between adjacent stator slots 32s at equal angular intervals around the axis CL. A yoke is a portion of the stator core 32 other than the teeth, which serves as a path for magnetic lines of force between the teeth that act as electromagnets. The stator coil 34 is wound around the teeth.

[0023] When driving the electric motor MG, three-phase AC currents of U, V, and W phases are respectively passed through the stator coil 34. For example, the U, V, and W phases are sinusoidal drive currents with a phase difference of 120 degrees. The drive currents are currents passed through the stator coil 34 to control the MG rotation speed Nmg [rpm] and MG torque Tmg of the electric motor MG. The MG rotation speed Nmg is the rotation speed of the electric motor MG. The three-phase AC currents of U, V, and W phases cause the stator 30 to generate a rotating magnetic field. In the electric motor MG, the phase of the drive current is controlled based on the rotational position of the rotor 40 so that the rotation of the rotor 40 can follow the rotating magnetic field generated by the stator 30. Note that these sinusoidal drive currents correspond to the "fundamental wave of the drive current" in this invention.

[0024] The rotor 40 includes a rotor core 42 and permanent magnets 44. The rotor core 42 is cylindrical and centered on the axis CL. A rotor shaft 46 is inserted into the hollow portion inside the rotor core 42. The rotor core 42 and the rotor shaft 46 are, for example, fitted together so as to be unable to rotate relative to each other. The outer circumferential surface of the rotor core 42 faces the inner circumferential surface of the stator core 32 in the radial direction. A plurality of rotor slots, which are through holes extending in the direction of the axis CL, are provided inside the rotor core 42. Permanent magnets 44 are inserted into the rotor slots so that N poles and S poles are alternately arranged at poles adjacent to each other in the circumferential direction of the rotor 42. The number of magnetic pole pairs in the circumferential direction of the rotor 40, i.e., the number of sets of N poles and S poles, is referred to as the "number of pole pairs."

[0025] The number of teeth Z of the drive gear 52 is set so that the order of the torque ripple [Nm] generated by the electric motor MG matches the order of the fluctuation of the meshing torque Tgear [Nm] generated by the drive gear 52. "Torque ripple" refers to pulsation in the MG torque Tmg caused by the interaction between the magnetic flux of the permanent magnet 44 and the magnetic flux of the stator coil 34, resulting in variations in magnetic flux density, when the rotor 40 of the electric motor MG is rotating. "Fluctuation in meshing torque Tgear" refers to pulsation in the meshing torque Tgear generated when the drive gear 52 meshes with the driven gear 54. Torque ripple and fluctuation in meshing torque Tgear cause vibration and noise. Vibration of the drive gear 52 caused by the torque ripple and fluctuation in meshing torque Tgear is transmitted to the case 60 via, for example, the rotor shaft 46 and bearings 62 and 64. This causes the case 60 to vibrate, resulting in vehicle body vibration and noise inside the vehicle cabin. Here, "order" refers to a frequency that is a specific multiple of the MG rotation speed Nmg of the electric motor MG. Specifically, "order 2" is a frequency that is twice the frequency of the MG rotation speed Nmg, and "order 3" is a frequency that is three times the frequency of the MG rotation speed Nmg.

[0026] The meshing torque Tgear generated by the drive gear 52 undergoes torque fluctuations the number of times corresponding to the number of teeth Z of the drive gear 52 per rotation of the drive gear 52.

[0027] As is well known, in the case of a three-phase synchronous motor, for example, torque ripple occurs with a frequency six times the number of pole pairs of the rotor 40 per rotation.

[0028] 2, three stator slots 32s face one pole pair in the rotor 40. When the total number of stator slots 32s is Ns (Ns is a multiple of 3), the number of pole pairs in the rotor 40 is Ns / 3. Torque ripple occurs per rotation of the rotor 40 (Ns / 3) × 6 = 2 × Ns times.

[0029] When the order of the torque ripple and the order of fluctuation of the meshing torque Tgear match, the following equation (1) holds. Z / n=2×Ns (where n is a natural number) (1)

[0030] Therefore, when the electric motor MG has the configuration shown in FIG. 2, the number of teeth Z of the drive gear 52, at which the order of the torque ripple and the order of the fluctuation of the meshing torque Tgear match, can be calculated by the following equation (2). Z = 2n × Ns (where n is a natural number) (2)

[0031] Fig. 3 is an example of a partial cross-sectional view perpendicular to the axis CL of the electric motor MG when the stator coil 34 is a distributed winding. In Fig. 3, the explanation will focus on the parts that are different from Fig. 2, and the same reference numerals will be used to denote substantially the same parts, and explanations thereof will be omitted as appropriate.

[0032] 3, 12 stator slots 32s face one pole pair in the rotor 40. When the total number of stator slots 32s is Ns (Ns is a multiple of 6), the number of pole pairs in the rotor 40 is Ns / 12. Torque ripple occurs (Ns / 12) × 6 = Ns / 2 times per rotation of the rotor 40.

[0033] When the order of the torque ripple and the order of the torque fluctuation of the meshing torque Tgear match, the following equation (3) holds. Z / n=Ns / 2 (where n is a natural number) (3)

[0034] Therefore, when the electric motor MG has the configuration shown in FIG. 3, the number of teeth Z of the drive gear 52, at which the order of the torque ripple and the order of the fluctuation of the meshing torque Tgear match, can be calculated by the following equation (4). Z = (n / 2) × Ns (where n is a natural number) (4)

[0035] In this way, the number of teeth Z of the drive gear 52 is set based on the number of phases of the AC current flowing through the stator coil 34, the total number of stator slots 32s, and the number of pole pairs of the rotor 40 so that the order of the torque ripple generated in the electric motor MG matches the order of the fluctuations in meshing torque Tgear generated in the drive gear 52. Note that, because the order of the torque ripple matches the order of the fluctuations in meshing torque Tgear, the generation of a beat noise, which is an interference noise based on a slight difference between the frequency of the torque ripple and the frequency of the fluctuations in meshing torque Tgear, is suppressed.

[0036] 1, a description will be given of the control functions of the electronic control unit 90. The electronic control unit 90 functionally comprises a rotation fluctuation calculation unit 90a, a rotation fluctuation determination unit 90b, and a drive control unit 90c.

[0037] The rotation fluctuation calculation unit 90a calculates the actual fluctuation amount ΔNgear of the gear rotation speed Ngear based on the gear rotation speed Ngear. The actual fluctuation amount ΔNgear is the actual fluctuation amount per time of the gear rotation speed Ngear. The gear rotation speed Ngear changes periodically according to the order of the torque ripple (and the order of fluctuation of the meshing torque Tgear). The actual fluctuation amount ΔNgear is the difference between the maximum and minimum values ​​of this periodically changing gear rotation speed Ngear. The rotation fluctuation calculation unit 90a calculates the actual fluctuation amount ΔNgear, for example, every predetermined sampling time Δt that is sufficiently short to detect fluctuations in the actual fluctuation amount ΔNgear. The actual fluctuation amount ΔNgear changes according to fluctuations in the torque ripple and meshing torque Tgear. When the amplitude of the combined waveform of the torque ripple and the meshing torque Tgear fluctuations increases, the actual fluctuation amount ΔNgear increases, and when the amplitude of the combined waveform of the torque ripple and the meshing torque Tgear fluctuations decreases, the actual fluctuation amount ΔNgear decreases. The actual fluctuation amount ΔNgear corresponds to the "magnitude of gear vibration" and the "amount of fluctuation in gear rotation speed" in this invention.

[0038] When the rotation fluctuation calculation unit 90a calculates the actual fluctuation amount ΔNgear, the rotation fluctuation determination unit 90b determines whether the actual fluctuation amount ΔNgear exceeds a determination value ΔNgear_jdg. The determination value ΔNgear_jdg is a predetermined determination value of the actual fluctuation amount ΔNgear that is determined experimentally or by design in order to determine whether the vibration caused by the fluctuation of the torque ripple and the meshing torque Tgear falls outside the acceptable range for the vehicle occupants, including the driver. The determination value ΔNgear_jdg corresponds to the "predetermined determination value" in this invention. When the actual fluctuation amount ΔNgear is equal to or less than the determination value ΔNgear_jdg, the vibration caused by the fluctuation of the torque ripple and the meshing torque Tgear falls within the acceptable range for the vehicle occupants. When the actual fluctuation amount ΔNgear exceeds the determination value ΔNgear_jdg, the vibration caused by the fluctuation of the torque ripple and the meshing torque Tgear falls outside the acceptable range for the vehicle occupants.

[0039] When the rotation fluctuation determination unit 90b determines that the actual fluctuation amount ΔNgear exceeds the determination value ΔNgear_jdg, the drive control unit 90c executes harmonic superposition control to superimpose harmonic currents on the fundamental wave of the drive current in the drive control of the electric motor MG. The frequency of the harmonic current is a frequency that can reduce the actual fluctuation amount ΔNgear. For example, the frequency of the harmonic current is the same as or higher than the frequency of the actual fluctuation amount ΔNgear. The waveform of the harmonic current is, for example, a sine wave.

[0040] Harmonic superposition control includes, for example, feedback control that adjusts the phase of the harmonic current relative to the fundamental wave of the drive current so that the actual fluctuation amount ΔNgear decreases. Specifically, when the electronic control device 90 advances the phase of the harmonic current relative to the fundamental wave, if the actual fluctuation amount ΔNgear increases, the electronic control device 90 executes feedback control to delay the phase of the harmonic current. On the other hand, if the actual fluctuation amount ΔNgear decreases, the electronic control device 90 executes feedback control to further advance the phase of the harmonic current. For example, when the electronic control device 90 delays the phase of the harmonic current relative to the fundamental wave, if the actual fluctuation amount ΔNgear increases, the electronic control device 90 executes feedback control to further advance the phase of the harmonic current. On the other hand, if the actual fluctuation amount ΔNgear decreases, the electronic control device 90 executes feedback control to further delay the phase of the harmonic current.

[0041] Harmonic superposition control includes, for example, feedback control that adjusts the amplitude of harmonic currents so as to reduce the actual fluctuation amount ΔNgear. Specifically, when the electronic control device 90 increases the amplitude of harmonic currents, if the actual fluctuation amount ΔNgear increases, the electronic control device 90 executes feedback control to reduce the amplitude of harmonic currents. On the other hand, if the actual fluctuation amount ΔNgear decreases, the electronic control device 90 executes feedback control to further increase the amplitude of harmonic currents. For example, when the electronic control device 90 decreases the amplitude of harmonic currents, if the actual fluctuation amount ΔNgear increases, the electronic control device 90 executes feedback control to increase the amplitude of harmonic currents. On the other hand, if the actual fluctuation amount ΔNgear decreases, the electronic control device 90 executes feedback control to further reduce the amplitude of harmonic currents. Note that the amplitude of harmonic currents is adjusted within a range of amplitude values ​​determined, for example, from a map that is experimentally or design-based, depending on the magnitude of the actual fluctuation amount ΔNgear. The larger the actual fluctuation amount ΔNgear, the larger the amplitude value obtained from the map.

[0042] The drive control unit 90c preferably prioritizes the execution of feedback control that adjusts the phase of the harmonic current relative to the fundamental wave of the drive current over feedback control that adjusts the amplitude of the harmonic current. This is because the actual fluctuation amount ΔNgear can be reduced more quickly when the phase of the harmonic current is adjusted first (for example, when the frequency of the harmonic current is the same as the frequency of the actual fluctuation amount ΔNgear, the harmonic current is quickly made to be in opposite phase with respect to the actual fluctuation amount ΔNgear) compared to when the amplitude of the harmonic current is adjusted first.

[0043] When the rotation fluctuation determination unit 90b determines that the actual fluctuation amount ΔNgear is less than or equal to the determination value ΔNgear_jdg, the drive control unit 90c does not perform harmonic superposition control in the drive control of the electric motor MG, i.e., performs normal drive control in which the drive current is only the fundamental wave.

[0044] Fig. 4 is an explanatory diagram showing an example of waveforms of a drive current and torque ripple in a three-phase synchronous motor. In Fig. 4, in order to facilitate understanding of the invention, the center position between the maximum and minimum amplitude values ​​in the torque ripple waveform is illustrated as being the same as the center position between the maximum and minimum amplitude values ​​of the three-phase AC.

[0045] In a three-phase synchronous motor, the drive current flowing through the stator core 32 is a three-phase AC current of U-phase, V-phase, and W-phase, which are shifted in phase by 120 degrees each other. As mentioned above, the frequency of the torque ripple is six times the frequency of the three-phase AC current.

[0046] Fig. 5 is an explanatory diagram of the vibration of the drive gear 52 caused by the torque ripple and the fluctuation of the meshing torque Tgear. In Fig. 5, in order to facilitate understanding of the invention, the center value between the maximum and minimum values ​​of the amplitude in the waveform of the torque ripple, the center value between the maximum and minimum values ​​of the amplitude in the waveform of the fluctuation of the meshing torque Tgear, and the center value between the maximum and minimum values ​​of the amplitude in the waveform of the actual fluctuation amount ΔNgear are each shown as zero.

[0047] The frequency of the fluctuation of the meshing torque Tgear generated in the drive gear 52 and the frequency of the torque ripple generated in the electric motor MG match.

[0048] As described above, torque ripple is a pulsation that occurs in the MG torque Tmg when the rotor 40 of the electric motor MG rotates due to the interaction between the magnetic flux of the permanent magnets 44 and the magnetic flux of the stator coil 34, resulting in variations in magnetic flux density. The magnetic flux state of the permanent magnets 44 is determined by the rotation angle of the rotor 40 from a predetermined reference position, and the magnetic flux state of the stator coil 34 is determined by the phase of the fundamental wave of the drive current. Hereinafter, the rotation angle of the rotor 40 from the predetermined reference position will be referred to as the "rotational position of the rotor 40." Because the rotor core 42 and the rotor shaft 46 cannot rotate relative to each other, the rotational position of the rotor 40 is uniquely determined by the rotational position of the rotor shaft 46. Note that the rotational position of the rotor shaft 46 is the rotational angle of the rotor shaft 46 from the predetermined reference position. The rotational position of the rotor 40 (= the rotational position of the rotor shaft 46) is uniquely determined based on the phase of the fundamental wave of the drive current and the load angle. The "load angle" is the angle by which the rotor 40 lags behind the rotating magnetic field, i.e., the phase of the fundamental wave of the drive current. The load angle is zero when the load on the motor MG is zero, and increases as the load on the motor MG increases. Therefore, the torque ripple generated by the interaction between the magnetic flux of the permanent magnet 44 and the magnetic flux of the stator coil 34 is uniquely determined based on the phase of the fundamental wave of the drive current and the load angle.

[0049] As described above, the drive gear 52 is connected to the rotor shaft 46 so as not to rotate relative to the rotor shaft 46. Therefore, fluctuations in the meshing torque Tgear are uniquely determined based on the rotational position of the rotor shaft 46. As described above, when the electric motor MG is a three-phase synchronous motor, the rotational position of the rotor shaft 46 is uniquely determined based on the phase and load angle of the fundamental wave of the drive current. Therefore, fluctuations in the meshing torque Tgear are uniquely determined based on the phase and load angle of the fundamental wave of the drive current.

[0050] In this way, the torque ripple and the fluctuation of the meshing torque Tgear are both uniquely determined based on the phase of the fundamental wave of the drive current and the load angle. Therefore, the phase difference between the torque ripple and the fluctuation of the meshing torque Tgear is determined by the phase of the fundamental wave of the drive current and the load angle.

[0051] 5 shows the cases where the phase of the torque ripple relative to the waveform of the fluctuation of the meshing torque Tgear is (a) 0 degrees, (b) 90 degrees ahead, and (c) 135 degrees behind. The waveform of the vibration of the drive gear 52 is determined by the combination of the waveform of the torque ripple and the waveform of the fluctuation of the meshing torque Tgear.

[0052] Fig. 6 is an example of a flowchart illustrating the control operation of the electronic control device 90 shown in Fig. 1. The flowchart in Fig. 6 is repeatedly executed.

[0053] First, in step S10 (hereinafter, "step" will be omitted), which corresponds to the function of the rotation fluctuation calculation unit 90a, the actual fluctuation amount ΔNgear of the gear rotation speed Ngear is calculated.

[0054] After S10 is executed, in S20 corresponding to the function of the rotation fluctuation determination unit 90b, it is determined whether or not the actual fluctuation amount ΔNgear exceeds the determination value ΔNgear_jdg.

[0055] If the determination in S20 is NO, in S30, which corresponds to the function of the drive control unit 90c, harmonic superposition control is not performed in the drive control of the electric motor MG, and normal drive control is performed in which the drive current is only the fundamental wave.

[0056] If the determination in S20 is YES, in S40, which corresponds to the function of the drive control section 90c, harmonic superposition control is executed in the drive control of the electric motor MG.

[0057] According to this embodiment, (a) the number of teeth Z of the drive gear 52 is set so that the order of the torque ripple generated in the electric motor MG matches the order of the fluctuation of the meshing torque Tgear generated in the drive gear 52, and (b) when the actual fluctuation amount ΔNgear of the drive gear 52 caused by the torque ripple and fluctuations in the meshing torque Tgear exceeds the judgment value ΔNgear_jdg, the electronic control device 90 executes harmonic superposition control to superimpose a harmonic current on the fundamental wave of the drive current so as to reduce the actual fluctuation amount ΔNgear. By executing the harmonic superposition control, the actual fluctuation amount ΔNgear of the drive gear 52 caused by fluctuations in the torque ripple and the meshing torque Tgear, i.e., the magnitude of the vibration of the drive gear 52, is suppressed, thereby suppressing increases in cost and weight and suppressing vibration in the drive device 20. For example, when such a drive unit 20 is mounted on a vehicle 10, increases in the cost and weight of the vehicle 10 are suppressed, while vibrations of the vehicle body and noise inside the vehicle cabin are suppressed.

[0058] According to this embodiment, the electronic control device 90 executes feedback control in the harmonic superposition control to adjust the phase of the harmonic current relative to the fundamental wave so as to reduce the actual fluctuation amount ΔNgear of the drive gear 52. Adjusting the phase of the harmonic current relative to the fundamental wave through feedback control reduces the magnitude of vibration of the drive gear 52. This suppresses vibration in the drive device 20.

[0059] According to this embodiment, the electronic control device 90 executes feedback control in the harmonic superposition control to adjust the amplitude of the harmonic current so as to reduce the magnitude of vibration of the drive gear 52. Adjusting the amplitude of the harmonic current through feedback control reduces the magnitude of vibration of the drive gear 52. This suppresses vibration in the drive device 20.

[0060] According to this embodiment, the execution of feedback control that adjusts the phase of the harmonic current relative to the fundamental wave of the drive current is prioritized over the feedback control that adjusts the amplitude of the harmonic current. Compared to when the amplitude of the harmonic current is adjusted first, when the phase of the harmonic current is adjusted first (for example, when the frequency of the harmonic current is the same as the frequency of the actual fluctuation amount ΔNgear, the harmonic current is quickly made to be in opposite phase with respect to the actual fluctuation amount ΔNgear), the actual fluctuation amount ΔNgear is quickly reduced, and the magnitude of vibration of the drive gear 52 is quickly reduced.

[0061] According to this embodiment, the electronic control device 90 determines the magnitude of vibration of the drive gear 52 based on the actual fluctuation amount ΔNgear of the gear rotation speed Ngear, which changes depending on the magnitude of vibration of the drive gear 52. The gear rotation speed Ngear, which is the rotation speed of the drive gear 52, is equivalent to the MG rotation speed Nmg, which is the rotation speed of the electric motor MG. The rotation positions of the drive gear 52 and the rotor 40 are uniquely determined based on the rotation position of one of them. When the rotation control of the electric motor MG is executed based on the MG rotation speed Nmg and the rotation position of the rotor 40, there is no need to provide additional sensors to detect the gear rotation speed Ngear and the rotation position of the rotor 40. This prevents increases in cost and weight and suppresses vibration in the drive device 20.

[0062] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0063] In the above-described embodiment, the fundamental wave of the drive current is a sine wave, but the present invention is not limited to this. For example, the fundamental wave of the drive current may be a square wave or a trapezoidal wave.

[0064] In the above-described embodiment, the motor MG is a three-phase synchronous motor, but the present invention is not limited to this. For example, the motor MG may be a motor driven by two-phase AC or four-phase AC.

[0065] In the above-described embodiment, the motor MG is an embedded magnet type, but the present invention is not limited to this. For example, the motor MG may be a surface magnet type motor.

[0066] In the above-described embodiment, the determination is made based on the actual fluctuation amount ΔNgear that changes in accordance with the magnitude of vibration of the drive gear 52, instead of the "magnitude of vibration of the drive gear 52," but the present invention is not limited to this. For example, instead of the "magnitude of vibration of the drive gear 52," the determination may be made based on the actual fluctuation amount per time of the rotation speed of the driven gear 54, which changes in accordance with the magnitude of vibration of the drive gear 52. For example, instead of the "magnitude of vibration of the drive gear 52," the determination may be made based on the actual fluctuation amount per time of the sound pressure waveform, which is detected by a sound pressure sensor and which is generated from the drive gear 52 and changes in accordance with the magnitude of vibration of the drive gear 52.

[0067] In the above-described embodiment, the harmonic superposition control includes feedback control for adjusting the phase of the harmonic current and feedback control for adjusting the amplitude of the harmonic current, but the present invention is not limited to this. For example, the harmonic superposition control may include feedback control for adjusting the phase of the harmonic current but not feedback control for adjusting the amplitude of the harmonic current. In this embodiment, the amplitude of the harmonic current is set to an amplitude value determined, for example, from a map that is determined experimentally or by design in advance according to the magnitude of the actual fluctuation amount ΔNgear.

[0068] In the above-described embodiment, harmonic superposition control is not executed when the actual fluctuation amount ΔNgear is equal to or less than the reference value ΔNgear_jdg, but it may be executed.

[0069] In the above-described embodiment, the electric motor MG is a motor generator, but the present invention is not limited to this. For example, the electric motor MG may be an electric motor having only a motor function without a generator function.

[0070] It should be noted that the above-described embodiments are merely examples of the present invention, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art, without departing from the spirit of the present invention. [Explanation of symbols]

[0071] 20: drive unit, 30: stator, 32: stator core, 34: stator coil, 40: rotor, 46: rotor shaft (shaft), 52: drive gear (gear), 90: electronic control unit (control unit), MG: electric motor, Tgear: meshing torque, Z: number of teeth, ΔNgear: actual fluctuation amount (magnitude of gear vibration), ΔNgear_jdg: judgment value (predetermined judgment value)

Claims

1. A drive device comprising: an electric motor including a stator having a stator core and a stator coil, and a rotor; a gear connected to a shaft of the rotor; and a control device that controls a drive current flowing through the stator coil, the number of teeth of the gear is set so that the order of torque ripple generated in the electric motor matches the order of fluctuation of meshing torque generated in the gear, When the magnitude of the gear vibration caused by the torque ripple and the fluctuation of the meshing torque exceeds a predetermined judgment value, the control device executes harmonic superposition control to superimpose a harmonic current on the fundamental wave of the drive current so as to reduce the magnitude of the gear vibration. A drive device characterized by:

2. The control device performs feedback control to adjust the phase of the harmonic current relative to the fundamental wave in the harmonic superposition control so that the magnitude of vibration of the gear is reduced.

2. The drive device according to claim 1.

3. The control device performs feedback control to adjust the amplitude of the harmonic current in the harmonic superposition control so that the magnitude of vibration of the gear is reduced.

2. The drive device according to claim 1.

4. the control device executes feedback control in the harmonic superposition control to adjust a phase of the harmonic current relative to the fundamental wave so as to reduce the magnitude of vibration of the gear, and executes feedback control in the harmonic superposition control to adjust an amplitude of the harmonic current so as to reduce the magnitude of vibration of the gear, The execution of feedback control for adjusting the phase of the harmonic current relative to the fundamental wave is prioritized over the execution of feedback control for adjusting the amplitude of the harmonic current.

2. The drive device according to claim 1.

5. The control device determines the magnitude of the vibration of the gear based on the amount of fluctuation in the rotation speed of the gear, which changes depending on the magnitude of the vibration of the gear.

5. The drive device according to claim 1, wherein the drive device is a drive unit.

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