WO2020137511A1

WO2020137511A1 - Drive-controlling device, motor drive device, and power-steering device

Info

Publication number: WO2020137511A1
Application number: PCT/JP2019/048244
Authority: WO
Inventors: 香織鍋師; 北村　高志
Original assignee: 日本電産株式会社
Priority date: 2018-12-28
Filing date: 2019-12-10
Publication date: 2020-07-02
Also published as: CN113228497B; JP7444075B2; CN113228497A; JPWO2020137511A1

Abstract

One embodiment of this drive-controlling device is a drive-controlling device that controls driving of a motor, wherein the drive-controlling device comprises: a first inverter connected to one end of a winding of the motor; a second inverter connected to the other end corresponding to the one end; a first control circuit that performs PWM control on the first inverter; and a second control circuit that performs PWM control on the second inverter. Between the first control circuit and the second control circuit, the frequency of the carrier signal in PWM control has a frequency difference that is at least the product of the maximum motor speed and the number of pole pairs.

Description

Drive control device, motor drive device, and power steering device

The present invention relates to a drive control device, a motor drive device, and a power steering device.

BACKGROUND ART Conventionally, there is known a connectionless motor having n-phase windings (coils) and no connection between the coils. As a method of driving such a connectionless motor, there is known a driving system called a full bridge in which an inverter is connected to both ends of each phase coil. In the drive of the connectionless motor by the full bridge, two inverters are normally driven and one inverter can be switched to the neutral point to perform three-phase control when an abnormality occurs. From the viewpoint of reducing the failure rate, a structure in which two inverters are controlled by two control circuits is known. In Patent Document 1, for example, the first control unit controls the driving of the first inverter, and the second control unit controls the driving of the second inverter.

JP, 2016-073097, A

From the viewpoint of reducing the failure rate, it is preferable to use the independent drive in which there is no circuit portion shared by the control circuits. However, in the case of a full bridge drive system, if the frequency synchronization of the signals of the PMW carrier in each control circuit is deviated, the torque ripple of the motor deteriorates, which causes problems such as noise and vibration. Therefore, one of the purposes of the present invention is to reduce inconveniences due to torque ripple while ensuring the independence of each control circuit.

One aspect of a drive control device according to the present invention is a drive control device that controls drive of a motor, and is connected to a first inverter connected to one end of a winding of the motor and to the other end of the one end. A second inverter, a first control circuit that performs PWM control on the first inverter, and a second control circuit that performs PWM control on the second inverter, and the first control circuit and the first control circuit. In the two-control circuit, the frequency of the PWM control carrier signal has a frequency difference equal to or more than the product of the maximum rotation speed of the motor and the number of pole pairs. An aspect of the motor drive device according to the present invention includes the drive control device and a motor whose drive is controlled by the drive control device. ‥

Further, an aspect of a power steering device according to the present invention includes the drive control device, a motor whose drive is controlled by the drive control device, and a power steering mechanism driven by the motor.

According to the present invention, it is possible to reduce inconveniences due to torque ripple while ensuring the independence of each control circuit.

FIG. 1 is a diagram schematically showing a typical block configuration of a motor drive unit according to this embodiment. FIG. 2 is a diagram schematically showing a typical circuit configuration of the motor drive unit according to the present embodiment. FIG. 3 is a diagram showing a current value flowing in each coil of each phase of the motor. FIG. 4 is a diagram schematically showing a voltage application state in a switching operation under PWM control. FIG. 5 is a diagram schematically showing a state in which the application is stopped in the switching operation under the PWM control. FIG. 6 is a diagram showing a PWM signal. FIG. 7 is a graph showing the results of the first to fourth tests. FIG. 8 is a graph showing the results of the 5th to 11th tests. FIG. 9 is a diagram showing a circuit configuration of a motor drive unit in a modified example in which circuit wiring is different. FIG. 10 is a diagram schematically showing the configuration of the electric power steering device according to the present embodiment.

Hereinafter, embodiments of a drive control device, a drive device, and a power steering device of the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid unnecessary redundancy in the following description and facilitate understanding by those skilled in the art, detailed description may be omitted more than necessary. For example, detailed description of well-known matters and duplicate description of substantially the same configuration may be omitted. ‥

In the present specification, a drive control device that supplies electric power from a power supply to a three-phase motor having three-phase (U-phase, V-phase, W-phase) windings (may be referred to as “coil”). The embodiments of the present disclosure will be described by way of example. However, a drive control device that supplies electric power from a power source to an n-phase motor having n-phase (n is an integer of 4 or more) winding such as four-phase or five-phase is also within the scope of the present disclosure.

(Structure of motor drive unit 1000)

FIG. 1 is a diagram schematically showing a block configuration of a motor drive unit 1000 according to this embodiment. The motor drive unit 1000 includes

inverters

101 and 102, a motor 200, and

control circuits

301 and 302.

In this specification, a motor drive unit 1000 including a motor 200 as a constituent element will be described. The motor drive unit 1000 including the motor 200 corresponds to an example of the drive device of the present invention. However, the motor drive unit 1000 may be a device for driving the motor 200, in which the motor 200 is omitted as a constituent element. The motor drive unit 1000 in which the motor 200 is omitted corresponds to an example of the drive control device of the present invention. ‥

The motor drive unit 1000 uses the two

inverters

101 and 102 to convert the electric power from the power supply (403 and 404 in FIG. 2) into the electric power supplied to the motor 200. For example, the

inverters

101 and 102 can convert DC power into three-phase AC power that is a U-phase, V-phase, and W-phase pseudo sine wave. The two

inverters

101 and 102 include

current sensors

401 and 402, respectively. ‥

The motor 200 is, for example, a three-phase AC motor. The motor 200 has U-phase, V-phase, and W-phase coils. The winding method of the coil is, for example, concentrated winding or distributed winding. ‥

The first inverter 101 is connected to one end 210 of the coil of the motor 200 and applies a drive voltage to the one end 210, and the second inverter 102 is connected to the other end 220 of the coil of the motor 200 and connected to the other end 220. Apply drive voltage. In the present specification, “connection” between parts (components) means electrical connection unless otherwise specified. ‥

The

control circuits

301 and 302 include

microcontrollers

341 and 342, etc., which will be described in detail later. The

control circuits

301 and 302 control the drive voltage of the

inverters

101 and 102 based on the input signals from the

current sensors

401 and 402 and the

angle sensors

321 and 322. As a control method of the

inverters

101 and 102 by the

control circuits

301 and 302, for example, a control method selected from vector control and direct torque control (DTC) is used. A specific circuit configuration of the motor drive unit 1000 will be described with reference to FIG. FIG. 2 is a diagram schematically showing a circuit configuration of the motor drive unit 1000 according to the present embodiment. ‥

The motor drive unit 1000 is connected to a first power source 403 and a second power source 404, which are independent of each other. The

power supplies

403 and 404 generate a predetermined power supply voltage (for example, 12V). As the

power supplies

403 and 404, for example, a DC power supply is used. However, the

power supplies

403 and 404 may be AC-DC converters or DC-DC converters, or batteries (storage batteries). In FIG. 2, the first power supply 403 for the first inverter 101 and the second power supply 404 for the second inverter 102 are shown as an example, but the motor drive unit 1000 is common to the first inverter 101 and the second inverter 102. May be connected to a single power source. Further, the motor drive unit 1000 may include a power source inside. ‥

The motor drive unit 1000 includes a first system corresponding to the one end 210 side of the motor 200 and a second system corresponding to the other end 220 side of the motor 200. The first system includes the first inverter 101 and the first control circuit 301. The second system includes the second inverter 102 and the second control circuit 302. Electric power is supplied from the first power supply 403 to the inverter 101 and the control circuit 301 of the first system. The second inverter 102 and the control circuit 302 are supplied with power from the second power supply 404. ‥

The first inverter 101 includes a bridge circuit having three legs. Each leg of the first inverter 101 includes a high side switch element connected between the power supply and the motor 200 and a low side switch element connected between the motor 200 and the ground. Specifically, the U-phase leg includes a high-side switch element 113H and a low-side switch element 113L. The V-phase leg includes a high side switch element 114H and a low side switch element 114L. The W-phase leg includes a high side switch element 115H and a low side switch element 115L. As the switch element, for example, a field effect transistor (MOSFET or the like) or an insulated gate bipolar transistor (IGBT or the like) is used. When the switch element is an IGBT, a diode (free wheel) is connected in antiparallel with the switch element. ‥

The first inverter 101 includes, for example, shunt

resistors

113R, 114R, and 115R as current sensors 401 (see FIG. 1) for detecting currents flowing in windings of U-phase, V-phase, and W-phase, respectively. Prepare for each leg. The current sensor 401 includes a current detection circuit (not shown) that detects a current flowing through each shunt resistor. For example, the shunt resistor may be connected between the low

side switch elements

113L, 114L and 115L and the ground. The resistance value of the shunt resistor is, for example, about 0.5 mΩ to 1.0 mΩ. ‥

The number of shunt resistors may be other than three. For example, two

shunt resistors

113R and 114R for U phase and V phase, two

shunt resistors

114R and 115R for V phase and W phase, or two

shunt resistors

113R and 115R for U phase and W phase are used. May be The number of shunt resistors used and the arrangement of shunt resistors are appropriately determined in consideration of product cost, design specifications and the like. ‥

The second inverter 102 includes a bridge circuit having three legs. Each leg of the second inverter 102 includes a high side switch element connected between the power supply and the motor 200 and a low side switch element connected between the motor 200 and the ground. Specifically, the U-phase leg includes a high side switch element 116H and a low side switch element 116L. The V-phase leg includes a high side switch element 117H and a low side switch element 117L. The W-phase leg includes a high side switch element 118H and a low side switch element 118L. Similar to the first inverter 101, the second inverter 102 includes, for example, shunt

resistors

116R, 117R and 118R. ‥

The motor drive unit 1000 includes

capacitors

105 and 106. The

capacitors

105 and 106 are so-called smoothing capacitors, and absorb the circulating current generated in the motor 200 to stabilize the power supply voltage and suppress the torque ripple. The

capacitors

105 and 106 are, for example, electrolytic capacitors, and the capacity and the number of capacitors used are appropriately determined according to design specifications and the like. ‥

Referring back to FIG. The

control circuits

301 and 302 include, for example,

power supply circuits

311, 312,

angle sensors

321, 322,

input circuits

331, 332,

microcontrollers

341, 342, drive

circuits

351, 352, and

ROMs

361, 362. .. The

control circuits

301 and 302 are connected to the

inverters

101 and 102. Then, the first control circuit 301 controls the first inverter 101, and the second control circuit 302 controls the second inverter 102. ‥

The

control circuits

301 and 302 can realize the closed loop control by controlling the target position (rotation angle), rotation speed, current, and the like of the rotor. The rotation speed is obtained, for example, by differentiating the rotation angle (rad) with time, and is represented by the number of rotations (rpm) at which the rotor rotates in a unit time (for example, 1 minute). The

control circuits

301 and 302 can also control the target motor torque. The

control circuits

301 and 302 may include a torque sensor for torque control, but torque control is possible even if the torque sensor is omitted. Further, a sensorless algorithm may be provided instead of the

angle sensors

321 and 322. The

power supply circuits

311 and 312 generate DC voltages (for example, 3V and 5V) required for each block in the

control circuits

301 and 302. ‥

The

angle sensors

321 and 322 are resolvers or Hall ICs, for example. The

angle sensors

321 and 322 are also realized by a combination of an MR sensor having a magnetoresistive (MR) element and a sensor magnet. The

angle sensors

321 and 322 detect the rotation angle of the rotor of the motor 200 and output a rotation signal representing the detected rotation angle to the

microcontrollers

341 and 342. The

angle sensors

321 and 322 may be omitted depending on the motor control method (for example, sensorless control). ‥

The

input circuits

331 and 332 receive the motor current value detected by the current sensors 401 and 402 (hereinafter, referred to as “actual current value”). The

input circuits

331 and 332 convert the level of the actual current value into the input level of the

microcontrollers

341 and 342 as necessary, and output the actual current value to the

microcontrollers

341 and 342. The

input circuits

331 and 332 are analog-digital conversion circuits. ‥

The

microcontrollers

341 and 342 receive the rotation signal of the rotor detected by the

angle sensors

321 and 322 and the actual current value output from the

input circuits

331 and 332. The

microcontrollers

341 and 342 set a target current value according to the actual current value and the rotation signal of the rotor, generate a PWM signal, and output the generated PWM signal to the

drive circuits

351 and 352. For example, the

microcontrollers

341 and 342 generate PWM signals for controlling the switching operation (turn-on or turn-off) of each switch element in the

inverters

101 and 102. ‥

Each

microcontroller

341, 342 is equipped with an

internal clock

371, 372. Generation of the PWM signal in each of the

microcontrollers

341 and 342 is executed according to the clock signal from the

internal clocks

371 and 372. That is, each of the

microcontrollers

341 and 342 frequency-converts the clock signals obtained from the oscillators of the

internal clocks

371 and 372 to generate PWM-controlled carrier signals. ‥

The basic frequency of the PWM signal generated by each of the microcontrollers 341 and 342 (that is, the frequency of the carrier signal in the PWM control) has a frequency difference of 1 kHz between the

microcontrollers

341 and 342. As a result, as will be described later in detail, even if a torque ripple due to a frequency difference occurs, it occurs in a sufficiently high frequency region. Therefore, noise and vibration accompanying the torque ripple deviate from the frequency range that can be perceived by humans, and the unpleasant sounds and vibrations for humans are suppressed. ‥

The

drive circuits

351 and 352 are typically gate drivers. The

drive circuits

351 and 352 generate a control signal (for example, a gate control signal) that controls the switching operation of each switch element in the first inverter 101 and the second inverter 102 according to the PWM signal, and generate the control signal to each switch element. Give to. The

microcontrollers

341 and 342 may have the functions of the

drive circuits

351 and 352. In that case, the

drive circuits

351 and 352 are omitted. ‥

The

ROMs

361 and 362 are, for example, writable memories (for example, PROM), rewritable memories (for example, flash memory), or read-only memories. The

ROMs

361 and 362 store control programs including instruction groups for causing the

microcontrollers

341 and 342 to control the

inverters

101 and 102. For example, the control program is once expanded in the RAM (not shown) at boot time.

(Operation of the motor drive unit 1000)

Hereinafter, a specific example of the operation of the motor drive unit 1000 will be described, and a specific example of the operation of the

inverters

101 and 102 will be mainly described.

The

control circuits

301 and 302 drive the motor 200 by performing three-phase energization control using both the first inverter 101 and the second inverter 102. Specifically, the

control circuits

301 and 302 perform three-phase energization control by switching-controlling the switch element of the first inverter 101 and the switch element of the second inverter 102. FIG. 3 is a diagram showing a current value flowing in each coil of each phase of the motor 200. ‥

FIG. 3 is a current obtained by plotting current values flowing in the U-phase, V-phase, and W-phase coils of the motor 200 when the first inverter 101 and the second inverter 102 are controlled according to the three-phase energization control. A waveform (sine wave) is illustrated. The horizontal axis of FIG. 3 represents the motor electrical angle (deg), and the vertical axis represents the current value (A). Ipk represents the maximum current value (peak current value) of each phase. Note that the

inverters

101 and 102 can drive the motor 200 by using, for example, a rectangular wave in addition to the sine wave illustrated in FIG. ‥

The current waveform illustrated in FIG. 3 is generated when a voltage having a waveform corresponding to the current waveform is applied to the motor 200. Then, such a voltage is generated by the switching element of the first inverter 101 and the switching element of the second inverter 102 switching by PWM control at a high speed such as 20 kHz. 4 and 5 are diagrams schematically showing a switching operation under PWM control. FIG. 4 shows a state of voltage application, and FIG. 5 shows a state of application stop. ‥

4 and 5 show, for example, a U-phase leg of the legs of the

inverters

101 and 102. As described above, the U-phase leg includes the high-side switch element 113H and the low-side switch element 113L on the first inverter 101 side, and the high-side switch element 116H and the low-side switch element 116L on the second inverter 102 side. ‥

The high-side switch element 113H and the low-side switch element 113L on the side of the first inverter 101 are not turned on at the same time, and when one is turned on, the other is turned off. Similarly, the high-side switch element 116H and the low-side switch element 116L on the second inverter 102 side are not turned on at the same time. ‥

When a voltage is applied to the winding of the motor 200, the high

side switch elements

113H and 116H are turned on in one of the two inverters 101 and 102 (the second inverter 102 in the case of FIG. 4) and the other (FIG. In the case of 4, the first inverter 101) turns on the low-

side switch elements

113L and 116L. As a result, a current flows from the one side to the other side as indicated by the arrow in the figure. ‥

When the application is stopped, all the switch elements are turned off. Immediately after being turned off, the circulating current from the motor 200 flows through the capacitors (105 and 106 in FIG. 2), but no current flows thereafter. Further, the circulating current does not contribute to the torque of the motor 200. ‥

In the two

inverters

101 and 102, the voltage application state shown in FIG. 4 and the application stop state shown in FIG. 5 are repeated at high speed. The repetition of the voltage application and the voltage application stop in the

inverters

101 and 102 is executed according to the PWM signal generated by the

microcontrollers

341 and 342 of the

control circuits

301 and 302. FIG. 6 is a diagram showing a PWM signal. ‥

The PWM signal is a binary pulse signal, and a first value representing voltage application and a second value representing application stop occur alternately. The pulse of the PWM signal is repeated at a cycle T0, and the cycle T0 is divided into a first value duration T1 and a second value duration T2. ‥

As described above, the PWM signal is a high frequency signal of, for example, 20 kHz, so the cycle T0 is a short cycle of, for example, 50 μsec. Therefore, the effective voltage (effective voltage) applied to the motor 200 becomes a voltage leveled in the cycle T0, and the ratio (duty) between the cycle T0 and the duration T1 of the first value is the power supply voltage and the effective voltage. Equal to the ratio of. The effective voltage is a voltage that changes with time corresponding to a changing current value as shown in the current waveform of FIG. 3, for example. Such time change of the effective voltage is realized by controlling the duty of the PWM signal by the

microcontrollers

341 and 342. ‥

Each of the two

microcontrollers

341 and 342 generates a carrier signal having a period T0 and generates a PWM signal based on the carrier signal. However, as described above, there is a difference in carrier signal frequency between the

microcontrollers

341 and 342. .. Therefore, the periods T0 do not match between the

microcontrollers

341 and 342, and the frequencies of the PWM signals are out of synchronization. Such a synchronization shift causes a torque ripple in the motor 200. Here, the simulation test of torque ripple caused by the frequency difference between PWM signals will be described. Table 1 shows the test conditions from the first test to the fourth test. ‥

In the first to fourth tests, the frequency (frequency of the first system) of the PWM signal generated by the microcontroller 341 of the first control circuit 301 for driving the first inverter 101 is fixed to 20 kHz. Then, the frequency (frequency of the second system) of the PWM signal generated by the microcontroller 342 of the second control circuit 302 for driving the second inverter 102 is changed. In the first test, the frequency of the second system is set to 19.95 kHz, and the frequency difference between the first system and the second system is 50 Hz. In the second test, the frequency of the second system is set to 19.995 kHz, and the frequency difference between the first system and the second system is 5 Hz. In the third test, the frequency of the second system is set to 19.9995 kHz, and the frequency difference between the first system and the second system is 0.5 Hz. In the 4th test, the frequency of the 2nd system is set to 19.99995kHz, and the frequency difference between the 1st system and the 2nd system is 0.05Hz. FIG. 7 is a graph showing the results of the first to fourth tests. A three-dimensional graph is shown in FIG. 7, where the height axis represents the torque intensity, the left back direction axis represents the frequency, and the right back direction axis represents the test number. The large peak near 500 Hz in the graph is the peak of the frequency component corresponding to the motor speed, not the torque ripple. ‥

In the graph showing the result of the first test, there are many peaks in the frequency region of several hundred Hz, and the peak at the position of 100 Hz corresponding to twice the frequency difference is particularly large. It can be seen that under the conditions of the first test, a large torque ripple corresponding to this large peak is generated. ‥

In the second to fourth tests, a large peak does not occur in the frequency region of several hundred Hz. Therefore, it is understood that the torque ripple hardly occurs when the frequency difference is about 5 Hz or less. However, in the case of a clock element using a crystal oscillator, for example, a frequency difference of 10 Hz or more easily occurs due to individual differences of the crystal oscillator, and it is difficult to suppress the frequency between the

independent microcontrollers

341 and 342 to about 5 Hz or less. .. Therefore, on the contrary, a simulation test was conducted in which the frequency difference was widened. Table 2 shows the test conditions from the 5th test to the 11th test. ‥

In the fifth test, both the frequency of the first system and the frequency of the second system are set to the fundamental frequency of 20.0 kHz, and the frequency difference between the first system and the second system is 0 Hz. That is, the frequencies of the PWM signals are completely synchronized between the first system and the second system. ‥

In the sixth test, the frequency of the first system is set to 21.0 kHz, which is +1000 Hz of the basic frequency, and the frequency of the second system is set to 20.0 kHz, the basic frequency. ‥

In the seventh test, the frequency of the first system is set to 20.0 kHz, which is the basic frequency, and the frequency of the second system is set to 19.0 kHz, which is -1000 Hz with respect to the basic frequency. ‥

In the eighth test, the frequency of the first system is set to 20.5 kHz, which is +500 Hz of the basic frequency, and the frequency of the second system is set to 20.0 kHz, the basic frequency. ‥

In the ninth test, the frequency of the first system is set to 20.0 kHz, which is the basic frequency, and the frequency of the second system is set to 19.5 kHz, which is -500 Hz with respect to the basic frequency. ‥

In the tenth test, the frequency of the first system is set to 20.1 kHz, which is +100 Hz with respect to the basic frequency, and the frequency of the second system is set to 20.0 kHz, which is the basic frequency. ‥

In the eleventh test, the frequency of the first system is set to 20.0 kHz, which is the basic frequency, and the frequency of the second system is set to 19.9 kHz, which is -100 Hz with respect to the basic frequency. FIG. 8 is a graph showing the results of the 5th to 11th tests. A three-dimensional graph is also shown in Fig. 8, where the height axis represents the torque intensity, the left back direction axis represents the frequency, and the right back direction axis represents the test number. Also in FIG. 8, the large peak near 500 Hz in the graph is the peak of the frequency component corresponding to the rotation speed of the motor, not the torque ripple. The graph showing the results of the 5th test does not show any particular peak in the frequency range of several hundred Hz. Therefore, it can be seen that torque ripple does not occur if the frequencies are synchronized. ‥

The graphs showing the results of the 10th test and the 11th test have many peaks in the frequency region of several hundred Hz, and the peak at the position of 200 Hz corresponding to twice the frequency difference is particularly large. It can be seen that under the conditions of the 10th test and the 11th test, a large torque ripple corresponding to this large peak occurs. ‥

In the sixth to ninth tests, a large peak does not occur in the frequency region of several hundred Hz. In the eighth to ninth tests, twice the frequency difference is 1 kHz, and a somewhat large peak appears at the 1 kHz position in the graph. Then, a torque ripple corresponding to this peak occurs. However, since the vibration of 1 kHz is outside the human sense range, problems such as noise due to torque ripple are suppressed. In the sixth to seventh tests, twice the frequency difference is 2 kHz, and noise and the like are further out of the human sense range. ‥

For example, when it is used in a power steering device or the like, the rotation speed of the motor 200 changes depending on the situation. If the rotation speed of the motor 200 changes and the vibration frequency of the torque ripple overlaps as a result of the change in the rotation speed of the motor as described above, the drive control of the motor may be disturbed. ‥

When the frequency of the PWM control carrier signal has a frequency difference equal to or more than the product of the maximum rotation speed of the motor 200 and the number of pole pairs, the frequency difference becomes 2n times (n is a natural number) between the first system and the second system. The frequency of the generated torque ripple deviates from the rotation speed of the motor 200 and also deviates from the human sense range. As a result, problems such as noise, vibration and control disturbance due to the torque ripple are suppressed. ‥

Further, it is desirable that the frequency difference between the carrier signals in the PWM control is a value excluding 3n times (n is a natural number) the product in mechanical angle. Even when the frequencies of the carrier signals in the first system and the second system are completely synchronized, a 6n-order torque ripple is generated in the motor 200. When the frequency difference of the carrier signals is 3n times the product in terms of mechanical angle, it is possible to prevent the torque ripple due to the frequency difference from overlapping with the torque ripple of the 6nth order. There are two possible configurations for obtaining the frequency difference between carrier signals. ‥

The first configuration is a configuration in which, as the two

internal clocks

371 and 372 shown in FIG. 1, clock elements whose clock signal frequencies are different from each other by, for example, about 5% are used. By using such a clock element, the same program can be used as a drive control program (particularly a carrier signal generation and PWM control program) in the two

microcontrollers

341 and 342. ‥

In the second configuration, the

microcontrollers

341, 3 having two frequency conversion coefficients are used.
42 is different from each other by, for example, about 5%. This conversion coefficient is used when the two

microcontrollers

341 and 342 frequency-convert the clock signals from the

internal clocks

371 and 372 to generate a carrier signal for PWM control. The microcontroller 341 of the first control circuit 301 frequency-converts at a first conversion ratio, and the microcontroller 342 of the second control circuit 302 frequency-converts at a second conversion ratio different from the first conversion ratio. To do.

In this configuration, clock elements having the same frequency can be adopted as the

internal clocks

371 and 372, and each carrier signal having a desired frequency difference can be easily obtained by the conversion coefficient. The clock element having the same frequency is, for example, a clock element in which a crystalline lens of the same standard is built in, and an increase in the kinds of parts can be avoided. Further, the

internal clocks

371 and 372 may have individual differences. That is, in the case of a lens of the same standard, an individual difference of about 50 Hz may occur as described above, but if the conversion coefficient differs by about 5%, a frequency difference far exceeding such an individual difference occurs, so that there is no individual difference. It doesn't matter. ‥

Note that, as another configuration, a configuration in which a circuit for confirming the synchronization state of the frequencies of the carrier signals is provided and the frequency of the carrier signal is changed based on the confirmed synchronization state to obtain a desired frequency difference is also conceivable. .. This configuration has an advantage that a desired frequency difference can be obtained even if the same variable is erroneously set as the conversion coefficient. Next, a modified example of the present embodiment will be described. FIG. 9 is a diagram showing a circuit configuration of a motor drive unit 1000 in a modified example in which circuit wiring is different. In the modification shown in FIG. 9, the ground ends of the first inverter 101 and the second inverter 102 are separated. Even with such a separated structure, a torque ripple occurs when the frequency of the carrier signal shifts. Therefore, also in the modification shown in FIG. 9, the frequency of the torque ripple deviates from the rotation speed of the motor 200 by providing the above-described difference in the frequency of the carrier signal of the PWM control between the first system and the second system. At the same time, the human sense area is out. As a result, problems such as noise, vibration, and control disturbance due to the torque ripple are suppressed.

(Embodiment of power steering device)

Vehicles such as automobiles generally include a power steering device. The power steering device generates an assist torque for assisting a steering torque of a steering system generated by a driver operating a steering wheel. The auxiliary torque is generated by the auxiliary torque mechanism, and the driver's operation load can be reduced. For example, the auxiliary torque mechanism is composed of a steering torque sensor, an ECU, a motor, a speed reduction mechanism, and the like. The steering torque sensor detects a steering torque in the steering system. The ECU generates a drive signal based on the detection signal of the steering torque sensor. The motor generates an auxiliary torque according to the steering torque based on the drive signal, and transmits the auxiliary torque to the steering system via the speed reduction mechanism. ‥

The motor drive unit 1000 of the above embodiment is preferably used for a power steering device. FIG. 10 is a diagram schematically showing the configuration of the electric power steering device 2000 according to the present embodiment. The electric power steering device 2000 includes a steering system 520 and an auxiliary torque mechanism 540. ‥

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522 (also referred to as “steering column”),

universal shaft couplings

523A and 523B, and a rotary shaft 524 (also referred to as “pinion shaft” or “input shaft”). ). ‥

Further, the steering system 520 includes, for example, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B,

tie rods

527A and 527B,

knuckles

528A and 528B, and left and right steering wheels (for example, left and right front wheels) 529A, 529B. ‥

The steering handle 521 is connected to the rotating shaft 524 via the steering shaft 522 and the

universal shaft couplings

523A and 523B. A rack shaft 526 is connected to the rotating shaft 524 via a rack and pinion mechanism 525. The rack and pinion mechanism 525 has a pinion 531 provided on the rotating shaft 524 and a rack 532 provided on the rack shaft 526. The right steering wheel 529A is connected to the right end of the rack shaft 526 through a ball joint 552A, a tie rod 527A, and a knuckle 528A in this order. Similar to the right side, the left steering wheel 529B is connected to the left end of the rack shaft 526 via a ball joint 552B, a tie rod 527B, and a knuckle 528B in this order. Here, the right side and the left side correspond to the right side and the left side as seen from the driver sitting in the seat, respectively. ‥

According to the steering system 520, steering torque is generated by the driver operating the steering wheel 521, and is transmitted to the left and right steering wheels 529A and 529B via the rack and pinion mechanism 525. This allows the driver to operate the left and right steering wheels 529A and 529B. ‥

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU 542, a motor 543, a speed reduction mechanism 544, and a power supply device 545. The auxiliary torque mechanism 540 applies an auxiliary torque to the steering system 520 extending from the steering wheel 521 to the left and right steering wheels 529A and 529B. The auxiliary torque may be referred to as "additional torque". ‥

As the ECU 542, for example, the

control circuits

301 and 302 shown in FIG. 1 and the like are used. Further, as the power supply device 545, for example, the

inverters

101 and 102 shown in FIG. 1 and the like are used. As the motor 543, for example, the motor 200 shown in FIG. 1 or the like is used. The ECU 542, the motor 543, and the power supply device 545 may form a unit generally referred to as a "mechanical integrated motor". Of the elements shown in FIG. 10, the mechanism including the elements other than the ECU 542, the motor 543, and the power supply device 545 corresponds to an example of a power steering mechanism driven by the motor 543. ‥

The steering torque sensor 541 detects the steering torque of the steering system 520 provided by the steering handle 521. The ECU 542 generates a drive signal for driving the motor 543 based on the detection signal from the steering torque sensor 541 (hereinafter referred to as “torque signal”). The motor 543 generates an auxiliary torque according to the steering torque based on the drive signal. The auxiliary torque is transmitted to the rotary shaft 524 of the steering system 520 via the speed reduction mechanism 544. The reduction mechanism 544 is, for example, a worm gear mechanism. The auxiliary torque is further transmitted from the rotary shaft 524 to the rack and pinion mechanism 525. ‥

The power steering device 2000 is classified into a pinion assist type, a rack assist type, a column assist type, and the like, depending on the location where the auxiliary torque is applied to the steering system 520. FIG. 10 shows a pinion assist type power steering device 2000. However, the power steering device 2000 is also applied to a rack assist type, a column assist type and the like. ‥

Not only the torque signal but also a vehicle speed signal may be input to the ECU 542. The microcontroller of the ECU 542 can PWM-control the motor 543 based on the torque signal, the vehicle speed signal, and the like. ‥

The ECU 542 sets the target current value based on at least the torque signal. It is preferable that the ECU 542 set the target current value in consideration of the vehicle speed signal detected by the vehicle speed sensor, and further in consideration of the rotor rotation signal detected by the angle sensor. The ECU 542 can control the drive signal of the motor 543, that is, the drive current so that the actual current value detected by the current sensor (see FIG. 1) matches the target current value. ‥

According to the power steering device 2000, the left and right steered wheels 529A and 529B can be operated by the rack shaft 526 using a composite torque obtained by adding the assist torque of the motor 543 to the steering torque of the driver. In particular, by using the motor drive unit 1000 of the above embodiment, problems such as noise and vibration due to torque ripple are reduced, and smooth power assist is realized. ‥

Although the power steering device is mentioned here as an example of the drive control device of the present invention and the method of use in the drive device, the use method of the drive control device and drive device of the present invention is not limited to the above, and a pump, a compressor It can be used in a wide range. ‥

The embodiments described above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above-described embodiments but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

101, 102: Inverter 200: Motor 301, 302: Control circuit 311, 312: Power supply circuit 321, 322: Angle sensor 331, 332: Input circuit 341, 342: Microcontroller 351, 352: Drive circuit 361, 362: ROM 371 , 372: internal clock 401, 402: current sensor 403, 404: power supply 1000: motor drive unit 2000: power steering device

Claims

A drive control device for controlling drive of a motor, wherein a first inverter connected to one end of a winding of the motor, a second inverter connected to the other end with respect to the one end, and a first inverter to the first inverter A first control circuit for performing PWM control and a second control circuit for performing PWM control for the second inverter are provided, and the first control circuit and the second control circuit include a carrier signal for PWM control. A drive controller in which the frequency has a frequency difference equal to or larger than the product of the maximum number of rotations of the motor and the number of pole pairs.
The drive control device according to claim 1, wherein the frequency difference is a value excluding 3n times (n is a natural number) the product in mechanical angle.
The first control circuit and the second control circuit frequency-convert a clock signal obtained from a vibrator to generate a PWM-controlled carrier signal, and the first control circuit frequency-converts at a first conversion ratio. The drive control device according to claim 1 or 2, wherein the second control circuit performs frequency conversion at a second conversion ratio different from the first conversion ratio.
A motor drive device comprising: the drive control device according to any one of claims 1 to 3; and a motor whose drive is controlled by the drive control device.
A power steering device comprising: the drive control device according to claim 1; a motor whose drive is controlled by the drive control device; and a power steering mechanism driven by the motor.