JP2001211681A - Brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless DC motor capable of reducing ripple current and rotating at high speed. SOLUTION: This brushless DC motor is provided with an armature current controller 7 for controlling a current value supplied to an armature 4 based on an output signal A of a rotational position sensor 6 detecting the rotational position of a rotor 3, and a drive unit 8 having a PWM control circuit 18 and an inverter 19 and supplying armature current to the armature 4 based on the current value. Current smoothing coils 21a, 21b, 21c having larger inductance than that of the armature 4 are provided in the respective phases between the inverter 19 and the armature 4, and a phase controller 9 advancing the phase of the armature current to the output signal A of the rotational position sensor 6 is provided on the armature current controller 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor, and more particularly, to a brushless DC motor driven by a PWM type inverter.

[0002]

2. Description of the Related Art As a brushless DC motor of this kind,
An armature current control device for controlling a current value supplied to an armature based on an output signal of a rotation position sensor for detecting a rotation position of a rotor, and an electric motor having a PWM control unit and an inverter unit, 2. Description of the Related Art There has been known a device provided with a driving device for supplying an armature current to an armature.

By the way, in a brushless DC motor designed for high-speed rotation, the inherent inductance of the armature is inevitably very small. When a brushless DC motor having an extremely small inductance of an armature is driven by a PWM inverter, a current flowing through the armature includes a ripple component. For this reason, there are problems that the rotor does not rotate smoothly and the armature generates heat intensely.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a brushless DC motor capable of reducing a ripple current and rotating at a high speed.

[0005]

A brushless DC motor according to the present invention controls an electric current supplied to an armature based on an output signal of a rotational position sensor for detecting a rotational position of the rotor. A brushless DC motor comprising: a current control unit; and a driving unit that has a PWM control unit and an inverter unit and supplies an armature current to the armature based on the current value. A current smoothing coil having an inductance greater than that of the armature in each of the phases, wherein the armature current control means includes a phase control means for advancing the phase of the armature current with respect to the output signal of the rotational position sensor. Is provided.

[0006] Since a current smoothing coil having a larger inductance than the armature is provided in each phase between the inverter section and the armature, the ripple component of the armature current is reduced, and the rotation of the rotor becomes smooth. And the heat generated by the armature is reduced.

By the way, if a current smoothing coil having a larger inductance than the armature is inserted in each phase between the inverter and the armature, the phase of the armature current is delayed and high-speed rotation becomes difficult.

However, since the armature current control means is provided with the phase control means for advancing the phase of the armature current with respect to the output signal of the rotational position sensor, the phase delay of the armature current can be prevented. . Then, by advancing the phase of the armature current with respect to the output signal of the rotation position sensor, that is, the position of the rotor, a demagnetization effect is generated, and high-speed rotation is smoothed. Further, when the brushless DC motor is operated as a generator, by advancing the phase of the armature current with respect to the position of the rotor, a magnetizing effect occurs, and the apparent capacity of the generator increases.

Therefore, according to the brushless DC motor of the present invention, the ripple component of the armature current can be reduced, the smoothness of the rotation of the rotor can be improved, and the heat generation of the rotor can be reduced. Rotation is possible.

[0010] For example, the phase control means includes current waveform data output means having storage means in which current waveform data representing a predetermined current waveform as a whole is stored in a series of addresses;
And address value control means for sequentially repeating an address value signal corresponding to the series of addresses and outputting the same to the current waveform data output means, wherein the current waveform data output means is output from the address value control means. The current value data of the address of the storage means corresponding to the address value signal is output, and the address value control means sets the phase of the current waveform represented by the current waveform data output from the current waveform data output means to the rotational position sensor. Output the address value signal so as to proceed with respect to the output signal.

As a storage means of the current waveform data output means, for example, a memory such as a PROM is used.

When an address value signal is output from the address value control means, the current waveform data output means reads out the current waveform data from the address of the storage means corresponding to the address value signal and outputs it. The address value signals corresponding to the series of addresses of the storage unit are sequentially and repeatedly output from the address value control unit, so that the current waveform data stored at the series of addresses of the storage unit are sequentially and repeatedly output, and as a result, Current waveform data representing a predetermined current waveform (for example, a sine waveform) as a whole is repeatedly output. The current waveform data output from the current waveform data output means is converted into an analog signal by an appropriate means such as a DA converter, and the analog signal is supplied to the drive means as an armature current value. The address value control means outputs the address value signal so that the phase of the current waveform represented by the current waveform data output from the current waveform data output means advances with respect to the output signal of the rotational position sensor. The armature current value and the phase of the armature current supplied from the driving means to the armature based on the armature current value are advanced with respect to the position of the rotor.

For example, the address value control means outputs a pulse signal for phase control having a predetermined width in response to an external trigger signal, a start end of an output signal of the rotational position sensor and a pulse signal of the phase control pulse signal. A signal synchronizing means for synchronizing the end and outputting a counting pulse signal having a frequency higher than the output signal of the rotational position sensor, and repeating the operation of counting and resetting the counting pulse signal to a predetermined value each time counting is performed. And a counting means for outputting a trigger signal to the pulse generation means when the count value is output to the current waveform data output means as an address value signal and reset.

As the pulse generating means, for example, a monostable multivibrator is used. As the signal synchronization means, for example, a PLL (Phase Locked Loop) circuit or the like is used. As the counting means, for example, a counter is used.

The counting means outputs the count value to the current waveform data output means as an address value signal each time the counting pulse signal from the signal synchronizing means is counted.
During a period from when the counting means is reset to when the count value is counted up to a predetermined value, an address value signal corresponding to a series of addresses in the storage means is output from the counting means to the current waveform data output means. Is output from the current waveform data output means. Then, the counting means repeats the operation of counting up the count pulse signal to a predetermined value and resetting, whereby current waveform data representing a predetermined current waveform as a whole is repeatedly output. The rest is the same as above.

When the counting means counts up and resets, the counting means outputs a trigger signal to the pulse generating means, and the pulse generating means outputs a phase control pulse signal to the signal synchronizing means. At the same time, the first address value signal is output from the counting means, and the first current waveform data is output from the current waveform data output means. Therefore, the phase of a series of current waveform data output from the current waveform data output means, that is, the phase of the armature current is synchronized with the reset of the counting means, that is, the start end of the trigger signal. On the other hand, since the beginning of the output signal of the rotational position sensor and the end of the pulse signal for phase control are synchronized by the signal synchronization means, the phase of the output signal of the rotational position sensor is controlled by the phase control with respect to the armature current. Of the pulse signal for use. That is, the phase of the armature current is different from the phase of the output signal of the rotational position sensor.
This advances by the width of the phase control pulse signal.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the overall configuration of a brushless DC motor. This electric motor is applied, for example, to a power storage flywheel device using a control type magnetic bearing. In this type of flywheel device, a rotor that is non-contact supported by a magnetic bearing in a vacuum in a casing is rotated at high speed by a built-in brushless DC motor.

The motor comprises a motor body (1) and a control section (2).

The motor body (1) has the same structure as that of a normal brushless DC motor, but FIG. 1 shows the rotor (3) on the rotor side and the armature (4) on the stator side. ) Are only shown. The armature (4) is provided with three-phase armature windings (5a) (5b) (5c). Windings are sign
Collectively referred to as (5).

The control section (2) includes a rotational position sensor (6), an armature current control device (7) constituting armature current control means, and a drive device (8) constituting drive means. FIG.
7 shows an example of a signal of a required portion of the armature current control device (7).

The rotation position sensor (6) detects the rotation position of the rotor (3). As shown by a signal A in FIG.
During one rotation of the rotor (3), one or more pulses are generated in proportion to the number of poles of the motor body (1). The rotation position sensor (6) also functions as a sensor that detects the rotation speed of the rotor (3).

The armature current control device (7) controls the armature current value based on the output signal (pulse signal) of the rotation position sensor (6) corresponding to the position of the rotor (3). A phase control device (9) constituting a phase control means, a subtractor (11),
An amplifier (12) and a multiplying DA converter (13) are provided.
The phase control device (9) is for advancing the phase of the armature current with respect to the output signal A of the rotational position sensor (6), and the current waveform data output device (10) constituting current waveform data output means. , And an address value control device (22) constituting address value control means.

The current waveform data output device (10) is provided with a PROM (23) constituting a storage means, and a series of addresses in the PROM (23) are generally represented by a signal E (current value signal) in FIG. Current waveform data representing a certain constant current waveform (sine waveform in this example) is stored. The PROM (23) stores current value data for three phases of the armature (4). When an address value signal is output from the address value control device (22) as will be described later, the current waveform data output device (10) stores the address value stored in the address of the PROM (23) corresponding to the address value. DA converter for current waveform data for each phase
Output to (13).

The address value control device (22) includes a PLL circuit (14) constituting a signal synchronizing means, a counter (15) constituting a counting means, and a monostable multivibrator (16) constituting a pulse generating means. I have.

The multivibrator 16 outputs a phase control pulse signal B having a predetermined width when a trigger signal C described later is input.

The PLL circuit (14) includes a rotational position sensor (6)
And the pulse signal B from the multivibrator (16). The PLL circuit (14) synchronizes the beginning (rising) of the signal A with the ending (rising) of the signal B, and outputs a counting pulse signal having a frequency higher than the frequency of the signal A by the frequency division ratio of the counter (15). Counter (15)
Output to

The counter (15) repeats the operation of counting and resetting the count pulse signal from the PLL circuit (14) to a predetermined value, and outputs the count value as an address value signal D every time counting. A trigger signal C is output to the multivibrator (16) when resetting, in addition to outputting to the device (23).

The output signal of the rotational position sensor (6) is
The rotation speed signal is converted into an analog rotation speed signal by an appropriate means such as a monostable multivibrator (not shown). Subtractor
In (11), the difference between the rotational speed signal and a preset speed set value is calculated, and the output of the subtracter (11) is
The signal is input to the DA converter (13) as a speed difference signal via (12).

The DA converter (13) is connected to the current waveform data device (1).
Each time the three-phase current waveform data is input from (0), these are converted to analog values, and the
Multiply the speed difference signal from (12) to obtain the current value signal E for three phases.
Is output to the driving device (8).

The driving device (8) includes three subtractors (17a) (17b) (17c) corresponding to the three-phase armature windings (5), respectively, and PWM.
The control unit includes a PWM control circuit (18) and an inverter unit (19). The subtractors are collectively referred to by reference numeral (17).
Three-phase current value signals E from the DA converter (13) of the armature current control device (7) are input to the corresponding subtracters (17). Each armature winding (5) is provided with a current detector (20a) (20b) (20c), and these voltage outputs are input to the corresponding subtracters (17). The current detector is generically referred to by reference numeral (20). Also,
Current smoothing coils (inductors) (21a), (21b), and (21c) having larger inductance than the armature winding (5) are provided between the inverter section (19) and each armature winding (5). Have been. The coils are collectively referred to by reference numeral (21). PWM control circuit (1
8) is the PW of the corresponding phase based on the output of each subtractor (17).
An M control signal is output to the inverter section (19). The inverter unit (19) performs armature winding of each phase based on the PWM control signal.
Supply armature current to (5). The PWM control circuit (1
A well-known appropriate configuration can be adopted for 8) and the inverter section (19).

In the above armature current control device (7),
The counter (15) outputs the count value to the current waveform data output device (10) as the address value signal D every time the counting pulse signal from the PLL circuit (14) is counted, and the counter (15) is reset. During the period from when the counter value is counted up to a predetermined value, an address value signal D corresponding to a series of addresses of the PROM (23) is output from the counter (15) to the current waveform data output device (10). When the address value signal D is output from the counter (15), the current waveform data output device
In (10), the PRO corresponding to the address value signal D
The current waveform data is read from the address of M (23),
This is output to the DA converter (13). An address value signal corresponding to a series of addresses of the PROM (23) is sequentially and repeatedly output from the counter (15), whereby the PROM (2
The current waveform data stored in the series of addresses of 3) is sequentially and repeatedly output. As a result, current waveform data representing a constant current waveform as a whole, such as signal E in FIG. ) Is output. The current waveform data output from the current waveform data output device (10) is converted by the DA converter (13).
Is converted into an analog value current value signal E proportional to the speed difference signal from the amplifier (12), and this current value signal E is supplied to the drive unit (8) as an armature current value.

Each phase between the inverter unit (19) and the armature (4) is provided with a coil (21) having a larger inductance than the armature winding (5), so that the armature current ripple is reduced. The components are reduced, the smoothness of rotation of the rotor (3) is improved, and the heat generation of the rotor is reduced. However, since there is a coil (21) having a large inductance in each phase between the inverter (19) and the armature (4), the phase of the armature current is delayed, and high-speed rotation becomes difficult. However, in the above-described motor, as described below, the phase control device
According to (9), the phase of the armature current is advanced with respect to the output signal of the rotation position sensor (6), so that a phase delay of the armature current can be prevented, and high-speed rotation can be performed.

The operation of the phase controller 9 when the multivibrator 16 is not provided in the address value controller 22 is as follows (see FIG. 2).

When the counter (15) counts up and resets, the counter (15) outputs a trigger signal C,
If the multi-vibrator (16) is not provided in the address value control device (22), the trigger signal C is output from the PLL circuit (1).
Enter directly in 4). At the same time that the trigger signal C is output from the counter (15), the PROM (2
The address value signal D corresponding to the first address in 3) is output, and the first current waveform data is output from the current waveform data output device (10). Therefore, the phase of the series of current waveform data output from the current waveform data output device (10), that is, the phase of the current value signal E, is synchronized with the reset of the counter (15), that is, the start of the trigger signal C. On the other hand, P
In the LL circuit (14), the start of the output signal A of the rotational position sensor (6) and the start of the trigger signal C are synchronized,
The phase of the current value signal E, that is, the phase of the armature current matches the phase of the output signal A of the rotational position sensor.

On the other hand, the operation of the phase control device (9) in FIG. 1 is as follows (see FIG. 3).

When the counter (15) counts up and resets, the trigger signal C is output from the counter (15) to the multivibrator (16), and the phase control pulse signal is sent from the multivibrator (16) to the PLL circuit (14). B is output. At the same time, the counter (15) outputs an address value signal D corresponding to the first address of the PROM (23),
First current waveform data is output from the current waveform data output device (10). Therefore, the current waveform data output device (1
The phase of a series of current waveform data output from 0), that is, the phase of the current value signal E, is synchronized with the reset of the counter (15), that is, the beginning of the trigger signal C. On the other hand, in the PLL circuit (14), the beginning of the output signal A of the rotation position sensor (6) and the end of the phase control pulse signal B are synchronized, so that the phase of the output signal A of the rotation position sensor (6) is The phase of the current value signal E is delayed by the width (a) of the phase control pulse signal B. That is, the phase of the current value signal E, that is, the phase of the armature current is determined by the rotation position sensor (6).
With respect to the phase of the output signal A of FIG.
Of the width of (a). The phase advance (a) is determined so as to be optimal in consideration of the characteristics of the electric motor and the like. However, when the cycle of the armature current is 360 degrees, it is, for example, 15 degrees or less.

The configuration of the brushless DC motor, the configuration of the armature current control device (7) and the configuration of the drive device (8) are not limited to those of the above-described embodiment, but can be changed as appropriate.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a brushless DC motor showing an embodiment of the present invention.

FIG. 2 is a time chart showing signals of respective parts of the address value control device when it is assumed that a monostable multivibrator is not provided in the address value control device of the phase control device.

FIG. 3 is a time chart showing signals of respective parts of an address value control device of the phase control device in the embodiment of FIG. 1;

[Explanation of symbols]

(3) Rotor (4) Armature (6) Rotary position sensor (7) Armature current control device (armature current control means) (8) Drive device (drive device) (9) Phase control device (phase control device) (10) Current waveform data output device (current waveform data output means) (14) PLL circuit (signal synchronization means) (15) Counter (counting means) (16) Monostable multivibrator (pulse generation means) (18) PWM Control circuit (PWM control section) (19) Inverter section (21a) (21b) (21c) Current smoothing coil (22) Address control device (address control means) (23) PROM (storage means)

Continued on the front page (72) Inventor Yasushi Yokoi 3- 25-7 Nakamiya Oike, Hirakata-shi, Osaka F-term in Nihon Inverter Co., Ltd. 5H560 AA10 BB04 BB12 DA07 DB20 DC12 EB01 EC01 GG04 RR01 RR05 TT02 TT03 TT12 TT15 TT20 XA02 XA04 XA12 XA15 5H576 AA20 BB04 DD02 DD07 EE11 GG02 GG04 GG06 HB01 JJ08 JJ11 JJ12 JJ16 JJ17 KK06 LL07 LL22 LL41

Claims (3)

[Claims] 1. An armature current control means for controlling a current value supplied to an armature based on an output signal of a rotation position sensor for detecting a rotation position of a rotor, and a PWM control unit and an inverter unit. A brushless DC motor having a driving means for supplying an armature current to the armature based on a value, wherein in each phase between the inverter section and the armature, a current smoothing having a larger inductance than the armature is provided. A brushless DC motor, further comprising: a coil for use in the motor; and a phase control unit for advancing the phase of the armature current with respect to the output signal of the rotational position sensor in the armature current control unit. 2. The current control circuit according to claim 1, wherein said phase control means has a storage means storing current waveform data representing a predetermined current waveform in a series of addresses, and an address value corresponding to said series of addresses. Address value control means for sequentially repeating a signal and outputting the current waveform data output means to the current waveform data output means, wherein the current waveform data output means includes an address value control means for storing the address value signal output from the address value control means. The current waveform data of the address is output, and the address value control means controls the address so that the phase of the current waveform represented by the current waveform data output from the current waveform data output means advances with respect to the output signal of the rotational position sensor. 2. The brushless DC motor according to claim 1, wherein the brushless DC motor outputs a value signal. 3. The pulse value generating means for outputting a phase control pulse signal having a predetermined width in response to an external trigger signal, a start end of an output signal of the rotational position sensor and a pulse signal of the phase control pulse signal. A signal synchronizing means for synchronizing the end and outputting a counting pulse signal having a frequency higher than the output signal of the rotational position sensor, and repeating the operation of counting and resetting the counting pulse signal to a predetermined value each time counting is performed. 2. A brushless DC motor according to claim 1, further comprising counting means for outputting a count value as an address value signal to said current waveform data output means and outputting a trigger signal to said pulse generation means when reset. .