JP3239532B2 - Motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a motor, and more particularly to a driving device for converting a DC power supply into an alternating current. The present invention relates to a motor drive device using a 120-degree conduction type inverter that performs variable speed operation by modulating with a signal.

[0002]

2. Description of the Related Art As described in Japanese Patent Application Laid-Open Publication No. Sho 62-171489, a conventional 120-degree conducting type inverter device energizes a phase which has been conducting until then when commutating to switch a conducting phase of a winding. Before stopping, a three-phase energizing mode is added, in which energization of the next phase is started, and thereafter, energization of the phase which has been flowing is terminated.

[0003]

In the above-mentioned prior art, the current is increased by the three-phase energization, and the torque ripple generated at the time of commutation is reduced by this effect. However, since the current increase is only during the three-phase conduction state, the amount of increase in the current is adjusted by adjusting the time in the three-phase conduction mode, and the current is locally increased. For this reason, if the three-phase conduction time is too long, the local current increases too much, and the time change rate of the current proportional to the motor torque may increase.

Furthermore, there is a non-linear relationship between the time in the three-phase conduction mode and the amount of current lift, making it difficult to predict the relationship between the magnitude of torque fluctuation and the time in the three-phase conduction mode. .

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the increase in the time rate of change of the current and to reduce the torque ripple generated at the time of commutation, and to reduce the torque ripple generated at the time of commutation even when the load or the motor speed changes. An object of the present invention is to provide a reduced motor drive device.

Another object of the present invention is to reduce the vibration and noise generated by the resonance of the tub by using the motor driving device as a driving device for a washing tub or a dehydration tub of a washing machine.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, based on a control signal from a control device, a one-phase output from a DC power supply is supplied to a constant energizing pause during an electrical angle of 180 degrees. In a motor drive device that drives a motor at a variable speed by a 120-degree conduction type inverter that obtains three-phase or more AC output, the control device includes a current inclining means for increasing a current in a two-phase conduction section of the inverter so as to rise to the bottom. Was prepared.

Further, in the above configuration, there is provided a current detecting means for detecting a current, and a slope amount command means for designating a slope amount of the current within the commutation cycle, wherein the slope of the current detection value detected by the current detecting means is provided. A correction amount correction unit that corrects a correction amount according to a difference between the tilt amounts output by the tilt amount command unit, or a correction amount correction unit that corrects the correction amount according to the detected motor rotation speed or motor load. ing.

[0009] The present invention is also characterized in that the above-mentioned electric motor drive device is used in a rotary drive component of a washing tub or a dehydration tub of a washing machine.

[0010]

The electric motor driving device of the present invention configured as described above continuously increases the current immediately before commutation during commutation by correcting the commutation rate, and reduces the time of torque generated during commutation. By reducing the rate of change, torque ripple generated during commutation can be reduced.

Further, the amount of increasing the current is changed in accordance with the detected motor speed and load, and commutation at an optimum current value is always possible even when the motor speed or load changes, so that operating conditions can be improved. Corresponding reduction in torque ripple during commutation can be realized.

Further, by performing the variable speed operation of the washing machine using a motor drive device capable of low torque ripple operation irrespective of the motor speed and load, a continuous variable speed operation can be performed without avoiding a mechanical resonance point. Driving can be realized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of a motor driving device according to an embodiment of the present invention. The motor driving device according to the present invention is
Power is supplied from a DC power supply 102 to a brushless DC motor 103 via a 120-degree conduction type inverter 101. The motor speed N is detected by the speed detecting means 109,
The duty ratio DT0 is determined by the duty ratio generating device 104 such that the error becomes zero as compared with the speed command NR output from the speed command device 107. Here, the conduction ratio DT0 is given by DT0 = Ton / T, where T is the period of the pulse width modulation signal, and Ton is the time during which voltage is applied to the winding. Hereinafter, the conduction ratio refers to the ratio of the voltage application time to this winding. The correction device 108 corrects the current ratio DT0 so that the current is inclined, and creates the current ratio DT. The modulation device 105 modulates the drive signal of the inverter at the duty ratio DT and outputs a pulse width modulation signal PD. The drive circuit 106 drives the switching element of the inverter in the drive circuit 106 according to the pulse width modulation signal PD. Occurs. The inverter 101 performs a chopper operation according to the drive signal DV, adjusts a current flowing through the motor, and controls the motor to rotate at the command speed NR.

Hereinafter, each element will be described in more detail.

The 120-degree conduction type inverter 101 has three-phase windings 1Ia to 1I of the brushless DC motor 103 by switching elements T1 to T6 and diodes D1 to D6.
c. The switching elements T1, T2, and T3 connect the motor winding to the positive terminal of the DC power supply 102, and turn on these to apply a positive voltage to the motor winding. Switching elements T4, T5 and T
Numeral 6 connects the motor winding to the negative terminal of the DC power supply 102, and turns on these to apply a negative voltage to the motor winding.

The drive circuit 106 outputs six drive signals DV which are control signals for turning on / off these switching elements.

The speed detecting means 109 detects and outputs the speed N of the electric motor. The speed detecting means 109 detects the magnetic pole position of the motor with a Hall sensor and detects the speed from the magnetic pole position, or detects the back electromotive force generated in the motor winding, and determines the speed based on the back electromotive force. Can be used.

The speed command device 107 outputs a speed command NR which is a speed at which the motor should rotate.

The duty ratio generating device 104 is provided with the speed command NR
And the conduction rate DT such that the difference between the detected speed N and the motor speed becomes zero.
0 is determined and output. That is, when the speed N is greater than the speed command NR, the flow rate is reduced, and conversely, when the speed N is
When it is smaller than R, the average torque of the electric motor is adjusted by increasing the conduction ratio to accelerate and decelerate to control the speed.

As will be described later, the correcting device 108 corrects the conduction rate DT0 by inclining the average current of the winding current so as to be slightly larger, thereby creating a conduction rate DT. The modulation device 105 generates and outputs a pulse width modulation signal PD according to the duty ratio DT.

The drive circuit 106 generates a pulse width modulated signal P
A drive signal DV for turning on / off the switching elements T1 to T6 of the inverter according to D is generated, and the average torque is controlled by adjusting the voltage applied to the three phases 1Ia, 1Ib, and 1Ic of the motor according to this signal. Speed control is realized by the

FIG. 2 is an explanatory diagram of the operation in one embodiment of the present invention, showing the three-phase winding currents (Ia, Ib, Ic) and the torque component current (IT). The torque component current IT is the sum of the absolute values of the currents flowing through the three phases of the motor. Since the motor driven by the 120-degree conduction type inverter generates torque near the peak of the back electromotive force of the motor, The back electromotive force when the current flows is relatively flat, and the motor torque is approximately proportional to the current corresponding to the torque. In one embodiment of the present invention, the correction device 108 corrects the conduction ratio so that the torque component current IT has a slope within the electrical angle of 60 degrees (T60 section) that is conducted between the same two phases with respect to the average torque. Add.

FIG. 3 is a diagram for explaining the operation in the prior art, and shows three-phase winding currents (Ia, Ia) as in FIG.
b, Ic) and torque component current (IT). The figure shows the case where the constant current control is performed so that the torque current IT becomes flat within the electrical angle of 60 degrees (section T60), which is energized between the same two phases. In this case, the torque component current becomes flat in the T60 section, but after the commutation, a sudden change in the torque component current IT occurs transiently (circled in the figure). The magnitude of the sudden change in the torque component current IT varies depending on the motor load torque and speed, but tends to increase as the load torque and speed increase.

FIG. 4 is an explanatory diagram of the operation in one embodiment of the present invention, which is shown in comparison with the prior art. (A) shows the operation of the present invention, and (b) shows the operation of the constant current control shown in FIG. In addition, 1 of each column
The second row shows the two-phase winding currents that are switched during commutation superimposed. The second row shows the motor torque and the average torque, which are almost determined by the torque current IT. The third row shows the magnitude of the motor vibration. The differential of the above-mentioned torque component current is shown for comparison. Note that this differential value indicates an envelope change excluding a change due to pulse width modulation.

According to the present invention, the time (recirculation time) t1 until the return current Ir (current goes to zero) of the phase in which the flow is completed becomes zero and the rise current Iu of the phase in which the flow is newly started are averaged. The conduction ratio D is set so that the current within the electrical angle of 60 degrees is inclined so that the rise time t2 reaching the current value is equal.
Add a correction to T0.

On the other hand, in the conventional constant current control, as shown in column (b), the duty ratio is changed so that the winding current coincides with the average current and becomes substantially constant, and the average current becomes flat. Is controlled so that In this case, the load torque
As the speed increases, the recirculation time t1 becomes shorter than the rise time t2, and the time difference causes a drop in the motor torque as shown in the second stage.

Next, when the motor torque is differentiated, a large torque change occurs as shown in the figure during commutation in the constant current control, resulting in vibration and noise. In the present invention, a slight increase in torque occurs within an electrical angle of 60 degrees, but the magnitude is small and very slow, so that a change in torque generated during commutation can be suppressed to a small value.

FIG. 5 shows a correction method according to an embodiment of the present invention. The broken line shown in the figure is the conduction ratio generator 104.
Is the conduction ratio DT0 determined by the following equation, and the solid line is the correction device.
The conduction ratio DT corrected by 108. In these figures, the ordinate indicates the conduction ratio and the abscissa indicates time, and shows how the electrical angle changes during a time T60 of 60 degrees. The figures show six types of correction methods (a) to (f), but the correction method may be selected according to the characteristics of the electric motor, the speed control range, and the like. As shown in the column of FIG. 4 (a), another method may be used as long as the magnitude of the correction is determined so that the winding current immediately before commutation is such that the reflux time t1 = the rise time t2.

The correction amount is determined by measuring the operating characteristics of the motor in advance to obtain a correction amount such that the recirculation time t1 = the rise time t2 as shown in FIG. With such a configuration, torque ripple reduction during commutation can be realized.

Next, another embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 6 is a block diagram of a motor driving device according to another embodiment of the present invention. 1 denote the same parts.

In this embodiment, a detection resistor 201 for detecting a DC current supplied to the motor through an inverter and a correction amount setting device 202 for determining a correction amount based on a current detection value Id detected thereby are used. Detection resistor 201
Is the current obtained by removing the return current flowing through the diodes D1 to D6 out of the winding current of the motor, and there are cases where the winding current is visible and invisible depending on the ON / OFF state of the switching element. Correction amount setting device 202
Detects the magnitude of the winding current using the state in which the winding current is visible, and calculates a correction amount D of the current immediately before commutation, which will be described later.
The duty ratio correction amount DDT is determined so as to realize Id.
As a result, feedback by current detection is provided, and the duty ratio correction amount can be changed according to changes in the operating state (load torque, speed, etc.) of the motor, and corrections can be made according to load fluctuations and speed fluctuations become.

The operation of the correction amount setting device 202 will be described below with reference to FIGS.

FIG. 7 is a conceptual diagram of commutation. FIG. 7A schematically shows the waveform of the winding current shown in the first stage of FIG. FIG. 4B shows the torque current IT.
Is shown. In the commutation, the rise current Iu rises fastest and the rise time t2 becomes minimum when the conduction ratio becomes 1 during this period, and FIG. 7 shows the current waveform in this case. The average current of the currents flowing before and after the commutation is defined as Im, the commutation is performed at time t0, and the time until the reflux current Ir becomes zero is the reflux time t1, and the rising current Iu is Im.
Is a rise time t2. At this time, the winding resistance R and the winding inductance L of the motor, the applied voltage E1 <0 (corresponding to the difference between the applied DC voltage and the back electromotive force) applied to the phase for which the conduction has been completed, and the conduction current Applied voltage E2> 0 (corresponding to the difference between the applied DC voltage and the back electromotive force) applied to the phase that starts the operation, a positive voltage is applied to one of the three phases, and a negative voltage is applied to the remaining two phases. It is given by the following equation from the three-phase flow model obtained.

[0036]

(Equation 1)

[0037]

(Equation 2)

FIG. 8 is a diagram for explaining the operation according to another embodiment of the present invention, and shows the relationship between the magnitude of the current derived therefrom and the reflux time t1 and the rise time t2.
From this, when the average current flowing before and after commutation is fixed at Im, the state of FIG. 4 is realized only at the point where the magnitude of the current is I0, and low torque ripple during commutation is realized. Although it is possible, when the current value changes, t2> t1 and FIG.
(B) A drop in the motor torque shown in column -2 occurs. Conversely, when t2 <t1, the torque ripple can be reduced by current control with the conduction ratio <1.

FIG. 9 shows the lifting amount in the correction amount setting device of the present invention. FIG. 9A shows the dip amount DI and the lifting amount DId with respect to the motor current.

FIG. 10 conceptually shows the shape of the current in the winding current waveform in the embodiment of the present invention, and the current pulsation due to the pulse width modulation is omitted. As shown in FIG. 9A, when the magnitude of the current increases, the amount of dip DI increases in the constant current control (when the average current of the current flowing before and after the commutation is fixed at Im). A sudden change in torque will occur. FIG. 9 (b) shows a lifting amount DId required for the drop amount ID = 0, which shows the difference between the average current Im and the current before commutation as shown in FIG. The correction amount setting device 202 in the embodiment of the present invention determines the lifting amount DId based on FIG. 9B, and determines the conduction ratio correction amount DDT such that the current detection value Id has the shape shown in FIG. . In practice, the lifting amount DId is
, And the difference between the average current value Im1 (average current obtained from Expression 1) and the average current value Im2 (average current obtained from Expression 2) that satisfies t1 = t2 in Expression 2, and the current feedback The conduction ratio correction amount DDT is determined so as to realize the obtained lifting amount.
In general, DId> ID from Expressions 1 and 2.

In this embodiment, the supply power that changes according to the magnitude of the load torque (almost the detected current value I when the DC voltage is constant)
(proportional to d) can be detected, and the torque ripple can be reduced accordingly.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 11 is a block diagram of a motor driving device according to another embodiment of the present invention. 1 denote the same parts.

In this embodiment, a correction amount setting device 302 for determining the duty ratio correction amount DDT3 according to the speed N is used. Hereinafter, the operation of the correction amount setting device 302 will be described with reference to FIG.

FIG. 12 shows the lift amount in the correction amount setting device of the present invention, and shows the drop amount DI shown in FIG.
And the change of the required lifting amount DId with respect to the speed change. As is clear from the figure, when the rotation speed changes, the back electromotive force changes.
By changing E1 and E2 in Equation 2, the amount of depression DI and the required amount of lifting DId change. The correction amount setting device 302 determines the lift amount DId according to the relationship shown in FIG. 12B, and determines the conduction ratio correction amount DDT3 such that the current detection value Id has the shape shown in FIG.
Actually, the lifting amount DId is equal to t1 in Equations 1 and 2.
= T2, which is obtained by calculating the difference between the average current value Im1 (average current obtained from Equation 1) and the average current value Im2 (average current obtained from Equation 2). The duty ratio correction amount DDT3 is determined so as to be realized.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 13 is a block diagram of a motor driving device according to another embodiment of the present invention. 1 to 12 indicate the same parts.

In this embodiment, the detected current value I of the motor windings 1Ia, 1Ib, 1Ic is replaced with the detected DC current value of FIG.
A correction amount setting device 402 that determines the duty ratio correction amount DDT4 using a, Ib, and Ic is used. Hereinafter, the operation of the correction amount setting device 402 will be described with reference to FIG.

FIG. 14 is an explanatory diagram of the operation in one embodiment of the present invention. The figure shows the three-phase winding currents of the a-phase, b-phase, and c-phase when switching from the state in which the current flows from the a-phase to the c-phase by commutation, to the state in which the current flows from the b-phase to the c-phase. ing. Further, the reflux time t1 and the rise time t2 are t1
> T2, t1 = t2, t1 <t2.

The phase in which the flow does not switch (in this case, c
The phase) current exhibits a characteristic shape in the relationship between t1 and t2. If t1 <t2, the c-phase current has a dip DI1 when commutating. Conversely, when t1> t2, the c-phase current has a very large lifting amount, and DId1 occurs. From this, when a three-phase current is detected, a current waveform of a phase in which conduction is not switched due to commutation (here, c phase) is detected, and a lifting amount DI0 is determined so that the dip amount DI1 becomes zero. Good. As described above, the correction amount setting device 402 according to the present embodiment determines the lifting amount DId0 so that the current dip amount DI1 of the phase in which conduction does not switch during commutation becomes zero, and the current detection value immediately before commutation is determined. The duty ratio correction amount DDT4 is determined so that the lift amount DId0 is larger than the average current. Actually, the duty ratio correction amount D
Repeating the detection of the dip amount DI1 when the DT4 is changed and the correction of the conduction rate correction amount DDT4 so that it becomes zero, the lift amount DId0 is determined by feedback control.

In this embodiment, since the correction amount setting device can directly detect the reflux time t1 by detecting the reflux current Ir, the detected reflux time t1 and the rise time t2 at which the current rises to the average value can be determined. The lifting amount DId0 may be determined so that the measured values coincide with each other.

In this embodiment, since the overlap time during commutation can be automatically adjusted based on the detected value of the winding current, low torque ripple control can be automatically realized regardless of the characteristics of the motor.

Next, another embodiment of the present invention FIG. 16
This will be described with reference to FIG.

FIG. 16 is a block diagram of a motor driving device according to another embodiment of the present invention. 1 to 12 indicate the same parts.

In this embodiment, the speed control device 501 outputs the current command IR so that the difference between the detected speed N and the speed command NR becomes zero, and the current control device 502 flows through the same phase. The conduction ratio DT is determined such that the current detection value Id is raised by the lifting amount DId shown in the previous embodiments with respect to the current command IR within the cycle. Thus, the current controller 502 automatically adjusts the lifting amount without knowing the relationship between the change in the duty ratio and the change in the current lifting amount, so that the lifting amount DId according to the speed or the magnitude of the load is adjusted.
With only information, low torque ripple control can be realized.

[0056] Next, a system to which the motor driving device of the present invention will be described with reference to FIG. 15.

FIG. 15 is a block diagram of a washing machine according to another embodiment of the present invention. In the present embodiment, the operation control device 90
4 is a weight sensor 902 provided below the washing tub 905.
Detects the amount of laundry put in the washing tub and operates the washing machine at a variable speed according to this amount. That is, the operation is performed by changing the speed command Ns according to the laundry amount. The motor driving device 901 controls the brushless DC motor 10 so as to match the speed command output from the operation control device 904.
3 speed is controlled. In this embodiment, in addition to the variable speed operation during washing, even when the rotation speed during dehydration is continuously changed,
The current waveform is automatically adjusted so that the torque ripple always decreases according to the rotation speed of the motor and the magnitude of the load, thereby achieving low vibration and low noise operation. In particular, in the washing machine, the washing tub plays a role of a loudspeaker, so that a small amount of vibration conventionally generates a large noise, but the present invention has remarkably reduced the noise.

[0058]

According to the present invention, the commutation rate is continuously increased from the current flowing immediately before commutation in accordance with the commutation characteristics of the inverter, and the time change rate of the torque generated during commutation is obtained. Has the effect of reducing torque ripple generated during commutation.

Further, according to the present invention, the variable speed operation of the washing machine is performed by using the motor driving device which always reduces the torque ripple at the time of commutation irrespective of the rotation speed of the motor or the magnitude of the load. There is an effect of realizing continuous low-noise variable-speed operation without avoiding a mechanical resonance point until high-speed rotation such as described above is achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a motor drive device according to an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram in one embodiment of the present invention.

FIG. 3 is an explanatory diagram of an operation in a conventional technique.

FIG. 4 is an operation explanatory diagram in one embodiment of the present invention.

FIG. 5 shows a correction method according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of a motor driving device according to another embodiment of the present invention.

FIG. 7 is a conceptual diagram of commutation in a 120-degree conduction type inverter.

FIG. 8 is an operation explanatory diagram according to another embodiment of the present invention.

FIG. 9 shows a lifting amount according to another embodiment of the present invention.

FIG. 10 is a current waveform according to another embodiment of the present invention.

FIG. 11 is a configuration diagram of a motor drive device according to another embodiment of the present invention.

FIG. 12 shows a lifting amount according to another embodiment of the present invention.

FIG. 13 is a configuration diagram of a motor drive device according to another embodiment of the present invention.

FIG. 14 is an operation explanatory diagram in another embodiment of the present invention.

FIG. 15 is a configuration diagram of a washing machine according to another embodiment of the present invention.
It is.

FIG. 16 shows a motor driving device according to another embodiment of the present invention .
FIG.

[Explanation of symbols]

101: Inverter, 102: DC power supply, 103: Brushless DC motor, 104: Conductivity generator, 105:
Modulation device, 106: drive circuit, 107: speed command device, 108, 208: correction device, 109: speed detection means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Yamamoto 5-2-1, Kamimizuhoncho, Kodaira-shi, Tokyo In the Semiconductor Division, Hitachi, Ltd. No. 1 Hitachi, Ltd. Living Equipment Division (72) Inventor Kazuyoshi Matsuo 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Living Equipment Division (56) References JP 3 -143285 (JP, A) JP-A-4-165987 (JP, A) JP-A-4-281390 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/10

Claims (4)

(57) [Claims] 1. A one-phase output from a DC power supply based on a control signal from a control device is obtained by a 120-degree conduction type inverter which obtains a three-phase or more AC output having a constant conduction suspension interval during an electrical angle of 180 degrees. In a motor driving device that drives a motor at a variable speed, the motor is a brushless DC motor, and the control device terminates commutation in a two-phase energizing section of the inverter.
An electric motor drive device comprising: current gradient means for increasing the current immediately before the end of the conduction section from the current immediately after the current . 2. The control device according to claim 1, wherein the control device uses a pulse width modulation signal obtained by comparing a duty ratio command for instructing an output current of the inverter and a carrier wave as the control signal. tilting means, rolling the conduction ratio of the carrier in the two-phase through flow section of the inverter
The flow rate immediately after the end of the flow is shorter than the flow rate
An electric motor drive device comprising a means for increasing the current flow rate . 3. The motor driving device according to claim 1, wherein the inverter is a P-modulated pulse width modulated signal.
A WM inverter, a motor driven by the inverter, speed detecting means for detecting the speed of the motor, speed command means for setting the speed of the motor, and a speed detected by the speed detecting means and designated by the speed command means. Speed control means for outputting a current command of the inverter in accordance with the difference in command speed, and current detection means for detecting current.
The current command output by the speed control means is provided with a slope in the current command during the period in which the current is flowing between the same two phases, and the sloped current command and the current detected by the current detection means are provided. An electric motor driving device comprising current control means for determining a conduction ratio so as to match. 4. A washing machine characterized in that any one of the electric motor driving devices according to claim 1 is used as a rotary drive component of a washing tub or a dehydration tub.