Drive device

Abstract

To suppress an increase in noise and vibration of a motor.SOLUTION: The drive device includes a motor having a rotor and a stator of which one end or both ends in an axial direction are fixed to a case, and a control unit that controls driving of the motor. One of the rotor and the stator has a skew structure. The control unit performs current control of the motor such that a compelling force with the rotor at a portion of the stator on a side far from a fixed end with the case in the axial direction is smaller than a compelling force with the rotor at a portion on a near side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a drive device. [Background technology]

[0002] A driving device has been proposed that includes a motor having a rotor and a stator, and a control unit that controls the motor (see, for example, Patent Document 1). Here, the rotor includes an A-phase rotor section and a B-phase rotor section that are divided axially, and the stator includes an A-phase stator and a B-phase stator that are divided axially. The A-phase rotor section and the A-phase stator section form an A-phase motor section, and the B-phase rotor section and the B-phase stator section form a B-phase motor section. The A-phase motor section and the B-phase motor section are combined while being shifted circumferentially so as to have a phase difference of 90 electrical degrees. The control unit sets fundamental currents of the A-phase drive current and the B-phase drive current, and at least one higher-order harmonic of (4n±1) order as a higher-order harmonic current to be superimposed on the fundamental currents to suppress the 4n-order component of torque pulsation of the combined torque of the A-phase motor section and the B-phase motor section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-9861 Summary of the Invention [Problem to be solved by the invention]

[0004] In such drive units, it is difficult to achieve an ideal motor force (electromagnetic force) due to variations in the hardware configuration (rotor and stator) and control. If the force between the rotor and the stator in the axial direction, which is far from the end fixed to the case, is large, there is a concern that the motor will resonate due to this force, resulting in increased noise and vibration.

[0005] The main object of the drive device of the present disclosure is to suppress an increase in noise and vibration of the motor. [Means for solving the problem]

[0006] The driving device of the present disclosure employs the following means to achieve the above-mentioned main object.

[0007] The drive device of the present disclosure comprises: A drive device comprising: a motor having a rotor and a stator having one or both axial ends fixed to a case; and a control unit that drives and controls the motor, one of the rotor and the stator has a skew structure, the control unit controls the current of the motor so that a force acting on the rotor at a portion of the stator farther from an end of the stator fixed to the case in the axial direction is smaller than a force acting on the rotor at a portion closer to the end of the stator fixed to the case in the axial direction. The gist of this is as follows.

[0008] In the drive device disclosed herein, either the rotor or the stator has a skewed structure. The control unit that drives and controls the motor controls the motor current so that the forcing force (electromagnetic forcing force) between the rotor and the stator at the portion of the stator farther from the end fixed to the case in the axial direction is smaller than the forcing force between the rotor and the portion of the stator closer to the end. This makes it possible to suppress noise and vibration caused by motor resonance excited by the forcing force. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a drive device 10 according to an embodiment. [Figure 2] FIG. 10 is a schematic diagram of a modified driving device 110. [Figure 3] FIG. 10 is a schematic diagram of a modified driving device 210. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 a drive device 10 according to an embodiment of the present disclosure. The drive device 10 according to the embodiment is mounted on vehicles such as electric vehicles, hybrid vehicles, and fuel cell vehicles, as well as on stationary construction equipment, and as shown in the figure, includes a motor 20, an inverter 40 as a control unit for controlling the drive of the motor 20, and an electronic control unit (hereinafter referred to as "ECU") 42.

[0011] The motor 20 is configured as a three-phase AC motor and includes a rotor 22 and a stator 28. The rotor 22 has two rotor sections 23 and 24 (arranged in this order from the top in FIG. 1). The rotor sections 23 and 24 are configured to the same specifications, with permanent magnets embedded in the rotor core at a circumferentially spaced interval. The rotor sections 23 and 24 are fixed to each other so as to form a skewed structure offset by a predetermined angle in the circumferential direction, and are also fixed to a rotor shaft 26. The rotor shaft 26 is rotatably supported by a case 30 via bearings 32 and is attached to a drive shaft connected to a drive wheel. The stator 28 is configured by a three-phase coil wound around a stator core. The stator 28 is fastened to the case 30 at one axial end (the lower end in FIG. 1) using, for example, bolts 34. Thus, the stator 28 is cantilevered by the case 30.

[0012] The inverter 40 has a plurality of switching elements. By switching the plurality of switching elements of the inverter 40, DC power from the battery 44 is converted into three-phase AC power and supplied to the three-phase coils of the stator 28, which generates a rotating magnetic field in the three-phase coils, thereby rotating the rotor 22 (rotor shaft 26). The battery 44 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery.

[0013] The ECU 42 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. Signals are input to the ECU 42 from various sensors. While not shown, the ECU 42 also receives, for example, the rotational position θm of the rotor shaft 26 from a rotational position sensor and the phase currents Iu, Iv, and Iw of each phase (U-phase, V-phase, and W-phase) from three current sensors. The ECU 42 outputs switching control signals to multiple switching elements of the inverter 40. The ECU 42 calculates the electrical angle θe and rotation speed Nm of the motor 20 (rotor shaft 26) based on the rotational position θm of the rotor shaft 26.

[0014] In the drive system 10 of the embodiment, the ECU 42 controls the switching of a plurality of switching elements of the inverter 40 based on a torque command Tm* of the motor 20. For example, when the drive system 10 is installed in an electric vehicle, the torque command Tm* is set so that the vehicle travels with a required torque Td* for travel that is based on the accelerator pedal depression amount and the vehicle speed.

[0015] Here, the control of the inverter 40 will be described. The ECU 42 first performs coordinate transformation (three-phase to two-phase transformation) of the phase currents Iu, Iv, and Iw of the motor 20 into d-axis and q-axis currents Id and Iq using the electrical angle θe of the rotor shaft 26. Next, the ECU 42 sets the d-axis and q-axis current commands Id* and Iq* based on the torque command Tm* of the motor 20. Then, the ECU 42 calculates the d-axis and q-axis voltage commands Vd* and Vq* by current feedback control so that the differences between the d-axis and q-axis current commands Id* and Iq* and the currents Id and Iq are canceled out. In addition, the ECU 42 performs coordinate transformation (two-phase to three-phase transformation) of the d-axis and q-axis voltage commands Vd* and Vq* into voltage commands Vu*, Vv*, and Vw* of the phases using the electrical angle θe. Furthermore, the voltage commands Vu*, Vv*, Vw for each phase are compared with a carrier wave (triangular wave) to generate PWM signals for a plurality of switching elements of the inverter 40, thereby controlling the switching of the plurality of switching elements.

[0016] In the embodiment, in setting the d-axis and q-axis current commands Id* and Iq*, the torque The torque command Tm* is applied to a current command map, which is determined in advance through experiments, analysis, etc., as the relationship between the torque command Tm* and the d-axis and q-axis current commands Id* and Iq*. The corresponding d-axis and q-axis current commands Id* and Iq* are derived and set from the current command map. The current command map is determined so that the forcing force (electromagnetic forcing force) between the rotor 22 and the stator 28 at a portion of the stator 28 farther from the axial end of the stator 28 fixed to the case 30 (the portion radially facing the rotor unit 23) is smaller than the forcing force between the rotor 22 and the stator 28 at a portion closer to the axial end (the portion radially facing the rotor unit 24). Noise and vibration caused by resonance of the motor 20, excited by the forcing force between the rotor 22 and the stator 28, tend to be larger at portions of the stator 28 farther from the fixed end than at portions closer to the fixed end. Therefore, by controlling the switching of the multiple switching elements of the inverter 40 using the current command map set as described above to drive and control the motor 120, it is possible to suppress noise and vibration caused by resonance of the motor 20 excited by the forcing force between the rotor 22 and the stator 28.

[0017] In the drive device 10 according to the embodiment described above, the rotor 22 of the motor 20 has two rotor portions 23 and 24, which are fixed to each other so as to form a skewed structure. The ECU 42 controls the switching of multiple switching elements of the inverter 40 using a current command map to drive and control the motor 120. The current command map is defined so that the forcing force (electromagnetic forcing force) between the rotor 22 and the stator 28 at a portion of the stator 28 farther from the end of the stator 28 fixed to the case 30 in the axial direction (a portion radially facing the rotor portion 23) is smaller than the forcing force between the rotor 22 and the stator 28 at a portion closer to the end (a portion radially facing the rotor portion 24). This suppresses noise and vibration due to resonance of the motor 120 induced by the forcing force between the rotor 122 and the stator 28.

[0018] In the above-described driving device 10, the rotor 22 of the motor 20 includes two rotor portions 23 and 24. However, this is not limiting. For example, as shown in a modified driving device 110 in FIG. 2, the rotor 122 of the motor 120 may include three rotor portions 123, 124, and 125 (arranged in this order from the top of FIG. 2). The rotor portions 123, 124, and 125 are fixed to each other so as to form a skew structure in which they are offset from each other by a predetermined angle in the circumferential direction, and are also fixed to the rotor shaft 26. In this case, as in the driving device 10, the current command map is set so that the forcing force (electromagnetic forcing force) between the rotor 122 and the stator 28 at a portion of the stator 28 farther from the fixed end of the stator 28 to the case 30 in the axial direction (the portion radially facing the rotor portion 123) is smaller than the forcing force between the rotor 122 and the stator 28 at a portion closer to the fixed end (the lower end of FIG. 2) of the stator 28 (the portion radially facing the rotor portions 124 and 125). In the drive unit 110, by using this current command map to control the switching of multiple switching elements of the inverter 40 and drive control the motor 120, noise and vibration caused by resonance of the motor 120 excited by the forcing force between the rotor 122 and the stator 28 can be suppressed, just like the drive unit 10.

[0019] In the above-described drive device 110, similar to the drive device 10, the stator 28 is fastened to the case 30 at one end in the axial direction (the lower end in FIG. 2 ) and thereby supported in a cantilevered manner by the case 30. However, the present invention is not limited to this. For example, as shown in a modified drive device 210 in FIG. 3 , the stator 28 may be fastened to the case 30 at both ends in the axial direction (the upper and lower ends in FIG. 2 ) using bolts 34 and nuts 35, thereby being supported at both ends by the case 30. In this case, similar to the drive devices 10 and 110, the current command map is set so that the forcing force (electromagnetic forcing force) between the rotor 122 and the stator 28 at a portion of the stator 28 farther from the fixed end of the stator 28 to the case 30 in the axial direction (the portion radially facing the rotor unit 124) is smaller than the forcing force between the rotor 122 and the stator 28 at a portion closer to the fixed end (the upper and lower ends in FIG. 3 ) of the stator 28 to the case 30 (the portion radially facing the rotor units 123 and 125). In the drive device 210, by using this current command map to control the switching of multiple switching elements of the inverter 40 and drive control the motor 120, noise and vibration caused by resonance of the motor 120 excited by the forcing force between the rotor 122 and the stator 28 can be suppressed, similar to the drive devices 10 and 110.

[0020] In the above-described driving device 10, the rotor 22 of the motor 20 has two rotor portions 23 and 24. In addition, in the driving devices 110 and 210, the rotor 122 of the motor 120 has three rotor portions 123, 124, and 125, but the rotor of the motor may have four or more rotor portions.

[0021] In the above-described embodiment, the rotor 22 has a skew structure out of the rotor 22 and the stator 28. However, instead of this, the stator 28 may have a skew structure.

[0022] 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 20 corresponds to the "motor," and the inverter 40 and the ECU 42 correspond to the "controller."

[0023] 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.

[0024] 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]

[0025] The present disclosure is applicable to industries such as the drive device manufacturing industry. [Explanation of symbols]

[0026] 10,110,210 Drive unit, 20,120 Motor, 22,122 Rotor, 23,24,123,124,125 Rotor section, 26 Rotor shaft, 28 Stator, 30 Case, 32 Bearing, 34 Bolt, 35 Nut, 40 Inverter, 42 ECU, 44 Battery.

Claims

[Claim 1] A drive device comprising: a motor having a rotor and a stator having one or both axial ends fixed to a case; and a control unit that drives and controls the motor, one of the rotor and the stator has a skew structure, the control unit controls the current of the motor so that a force acting on the rotor at a portion of the stator farther from an end of the stator fixed to the case in the axial direction is smaller than a force acting on the rotor at a portion closer to the end of the stator fixed to the case in the axial direction. Drive unit.

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