Washing machine motor drive device Number:6,737,828 from the United States Patent and Trademark Office (PTO) owispatent

Title: Washing machine motor drive device

Abstract: A washing machine motor drive device drives a motor using an inverter circuit, which implements a constant torque control through a change in the torque-revolution speed characteristic of the motor. This facilitates an easy control of braking torque (negative torque), thereby providing a maximized braking torque. An easy control of regenerative energy is also provided, and back electromotive force is consumed by the internal resistance of the motor. Practically described, DC power of a rectifier circuit connected to an alternating current source is converted by an inverter circuit into AC power for driving the motor for operating an agitator or a washing/spinning tub. Motor rotor position is detected by rotor position detector, motor current is detected by current detector, and a control device controls the inverter circuit for resolving the motor current into a current component corresponding to magnetic flux and a current component corresponding to torque. At a motor braking operation, the current component corresponding to magnetic flux and the current component corresponding to torque are controlled independently. As a result, the torque at high speed revolution can be increased, or the efficiency at low speed revolution can be improved. This leads to the use a downsized and energy-conscious motor, and contributes to the prevention of an abnormal rise of DC voltage in the inverter circuit.

Patent Number: 6,737,828 Issued on 05/18/2004 to Kiuchi,   et al.

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Inventors:	Kiuchi; Mitsuyuki (Nara, JP), Kondo; Norimasa (Osaka, JP), Tamae; Sadayuki (Osaka, JP), Hagiwara; Hisashi (Osaka, JP)
Assignee:	Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
Appl. No.:	10/187,199
Filed:	July 2, 2002

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Foreign Application Priority Data

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Jul 19, 2001 [JP]			2001-219388
Aug 07, 2001 [JP]			2001-238767

Current U.S. Class:	318/779 ; 318/254; 318/269; 318/272; 318/431; 318/432; 318/55; 318/59; 318/62; 318/71; 68/12.02; 68/12.16
Current International Class:	H02P 27/04 (20060101); H02P 27/08 (20060101); H02P 6/08 (20060101)
Field of Search:	318/254,138,439,779,778,802,803,805,806,612,689,55,56,59,60,62,63,71,87,101,269,272,376,431,432,455 68/12.02,12.04,12.16,12.23,12.27,23.7

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References Cited [Referenced By]

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U.S. Patent Documents

	4556827		December 1985		Erdman
	4885518		December 1989		Schauder
	5237256		August 1993		Bashark
	5463301		October 1995		Kim
	5510689		April 1996		Lipo et al.
	5813069		September 1998		Kim
	5998958		December 1999		Lee
	6194864		February 2001		Kinpara et al.
	6229719		May 2001		Sakai et al.
	6262555		July 2001		Hammond et al.
	6495980		December 2002		Cho et al.
	6605912		August 2003		Bharadwaj et al.

Foreign Patent Documents

	11-090088		Apr., 1999		JP
	2001-046777		Feb., 2001		JP
	2002315387		Oct., 2002		JP
	2003088168		Mar., 2003		JP
	2003135883		May., 2003		JP

Other References

Translation Document 11-090088.* . Translation Document 2001-046777..

Primary Examiner: Duda; Rina
Assistant Examiner: San Martin; Edgardo
Attorney, Agent or Firm: Wenderoth, Lind & Ponack, L.L.P.

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Claims

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What is claimed is:

1. A washing machine motor drive device comprising: an alternating current source; a rectifier circuit connected to said alternating current source; an inverter circuit operable to convert DC power of said rectifier circuit into AC power; a DC brushless motor driven by said inverter circuit, said DC brushless motor being operable to drive an agitator or a washing/spinning tub; a rotor position detector operable to detect a rotor position of said DC brushless motor; a current detector operable to detect a current of said DC brushless motor; and a control device operable to control said inverter circuit, wherein said control device resolves the current of said DC brushless motor into a current component that corresponds to magnetic flux and a current component that corresponds to torque, controls the current component corresponding to magnetic flux and the current component corresponding to torque independently, and controls the current component corresponding to magnetic flux so that the current component corresponding to magnetic flux is increased in a negative direction in accordance with a revolution speed of said DC brushless motor.

2. A washing machine motor drive device of claim 1, wherein said control device controls the current component corresponding to magnetic flux so that the current component corresponding to magnetic flux becomes substantially zero when the revolution speed of said DC brushless motor is low.

3. A washing machine motor drive device of claim 1, wherein said control device controls the current component corresponding to magnetic flux so that the current component corresponding to magnetic flux is increased in a negative direction when the revolution speed of said DC brushless motor is high for driving a washing/spinning tub for a dehydration operation.

4. A washing machine motor drive device of claim 1, wherein said control device controls the current component corresponding to magnetic flux so that the current component corresponding to magnetic flux is increased in a negative direction when the revolution speed of said DC brushless motor is high for driving an agitator for a washing operation.

5. A washing machine motor drive device of claim 1, further comprising a clothes amount detector operable to detect an amount of clothes in a washing/spinning tub, wherein said control device controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the amount of clothes detected by said clothes amount detector.

6. A washing machine motor drive device of claim 1, wherein said control device comprises a start control device operable to control motor revolution at a start of revolution, and said control device makes a direct control on a voltage to be applied to said DC brushless motor at the start of revolution via said start control device, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently.

7. A washing machine motor drive device of claim 1, wherein said control device comprises a start control device operable to control motor revolution at a start of revolution, and said control device makes a direct control on a voltage to be applied to said DC brushless motor at the start of revolution via said start control device, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with revolution speed.

8. A washing machine motor drive device of claim 1, wherein said control device controls the current component corresponding to magnetic flux and the current component corresponding to torque independently at a motor braking operation.

9. A motor drive device of claim 8, wherein said control device controls the current component corresponding to torque so that the current component corresponding to torque meets a specified value at the motor braking operation.

10. The motor drive device of claim 8, wherein said control device controls the current component corresponding to torque so that the current component corresponding to torque is specified in a negative value at the motor braking operation.

11. A motor drive device of claim 8, wherein said control device controls the current component corresponding to magnetic flux and the current component corresponding to torque independently so that the current components corresponding to magnetic flux and torque meet respective specified values at the motor braking operation.

12. A motor drive device of claim 8, wherein said control device controls the current component corresponding to magnetic flux so that the current component corresponding to magnetic flux is greater than the current component corresponding to torque at a start of a motor braking operation.

13. A motor drive device of claim 8, further comprising revolution speed detector operable to detect a revolution speed from an output signal of said rotor position detector, wherein said control device controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the revolution speed so that the current components corresponding to magnetic flux and torque meet respective specified values at a motor braking operation.

14. A washing machine motor drive device comprising: an alternating current source; a rectifier circuit connected to said alternating current source; an inverter circuit operable to convert DC power of said rectifier circuit into AC power; a motor driven by said inverter circuit, said motor being operable to drive an agitator or a washing/spinning tub; a rotor position detector operable to detect a rotor position of said motor; a current detector operable to detect a motor current of said motor; a DC voltage detector operable to detect DC voltage of said inverter circuit; and a control device operable to control said inverter circuit, wherein said control device resolves the motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently so that the DC voltage meets a specified value at a motor braking operation.

15. A motor drive device of claim 14, wherein said control device controls the current component corresponding to magnetic flux, or a voltage component, so that the DC voltage of said inverter circuit meets a specified value at the motor braking operation.

16. A washing machine motor drive device comprising: an alternating current source; a rectifier circuit connected to said alternating current source; an inverter circuit operable to convert DC power of said rectifier circuit into AC power; a motor driven by said inverter circuit, said motor being operable to drive an agitator or a washing/spinning tub; a rotor position detector operable to detect a rotor position of said motor; a current detector operable to detect a motor current of said motor; a motor electric power detector operable to detect a power of said motor; and a control device operable to control said inverter circuit, wherein said control device resolves the motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the power of said motor at the motor braking operation.

17. A motor drive device of claim 16, wherein said motor electric power detector makes calculations based on a power component corresponding to magnetic flux and a power component corresponding to torque for performing control.

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Description

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FIELD OF THE INVENTION

The present invention relates to a device for driving washing machine motor using an inverter circuit.

BACKGROUND OF THE INVENTION

It has been proposed to improve performance of a washing machine motor through vector control using an inverter circuit (an example of such a proposal is included in JP 11090088).

FIG. 28 is a block diagram showing the structure of a washing machine of the above-described category. In FIG. 28, a three-phase induction motor 100 drives an agitator 102, or a spin tub 104. Current detectors 126a, 126b, 126c detect the motor current and control the torque current component and the magnetizing current component independently as vectors for driving the motor via an inverter circuit 124. In this way, the motor 100 is increased in torque at low speed revolution, and driven with approximately the same torque characteristic as a DC brushless motor.

It is also proposed to apply electric braking to a washing machine motor using an inverter, for the purpose of improving the braking reliability and lowering the braking noise caused by a mechanical band brake (an example: the Japanese Laid-open Patent No. 2001-46777). Namely, it aims to improve the reliability by controlling at the revolution retardation of the sinusoidal wave voltage phase by means of PWM control so that the power generation energy is consumed by the internal resistance of a motor, in other words dynamic braking, without causing regenerative energy in a DC source of an inverter circuit.

In the above-described conventional configuration, however, vector technology using an inverter circuit for improving the performance of a motor works to improve torque of a three-phase induction motor at low speed revolution, but it is difficult to improve the efficiency of a motor. Moreover, the low efficiency of the three phase induction motor allows a large current to flow, resulting in increased motor noise. These are problems that need to be solved.

With respect to the electric braking of a motor by means of an inverter control, it needs a complicated control to have the entire power generation energy consumed by the internal resistance of a motor. Furthermore, it does not provide sufficient braking torque for the increasing brake current of a motor.

SUMMARY OF THE INVENTION

The present invention addresses the above drawbacks, and aims to offer a compact and energy-conscious motor with which a constant torque control can be performed by changing the motor torque--revolution speed characteristic, and the torque at high speed revolution can be increased, or the efficiency at low speed revolution can be improved.

A washing machine motor drive device in accordance with the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of the motor, a current detector for detecting motor current, and a control device for controlling the inverter circuit. The control device resolves motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with motor control stages. In the above-described structure, motor current of a DC brushless motor is detected to be resolved into a current component corresponding to magnetic flux and a current component corresponding to torque for practicing vector control. At low speed revolution, mainly the current component corresponding to torque is controlled for yielding maximized efficiency, while at high speed revolution, the current component corresponding to magnetic flux is increased in a negative direction for increasing the current through a flux-weakening control for implementing a maximum torque control. Thereby, the motor torque--revolution speed characteristic can be changed and a constant torque control can be implemented. This enables an increase in torque at high speed revolution, or an improvement in efficiency at low speed revolution. Therefore, a motor can be made smaller in size and more energy-conscious.

A washing machine motor drive device in accordance with the present invention comprises a control device, with which device the current component corresponding to magnetic flux and the current component corresponding to torque are controlled independently in accordance with a revolution speed of a motor. In the above configuration, the motor torque--revolution speed characteristic can be modified.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed. This makes it possible to increase the torque at high speed revolution and perform a precise flux-weakening control.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is controlled to be substantially zero when a motor is revolving at a low speed. This makes it possible to revolve a motor at a highest efficiency in low speed revolution.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed for driving a washing/spinning tub for the purpose of dehydration (drying). This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control, and control the dehydration operation covering up to a high revolution speed. As a result, a rate of the dehydration can be increased by increasing the revolution speed.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed for driving an agitator for the purpose of washing. This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control, and control the agitating operation covering up to a high revolution speed. As a result, the washing capability can be increased by strengthening the water flow.

A washing machine motor drive device in the present invention comprises a clothes amount detector for detecting an amount of clothes in a washing/spinning tub, and a control device for controlling the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the amount of the clothes in the washing/spinning tub detected by the clothes amount detector. This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control in accordance with the amount of clothes, and control the operation covering up to a high revolution speed even in a case where there are many clothes in a washing tub. Thus, the washing capability can be improved, and rate of the dehydration can be raised as well.

A washing machine motor drive device in the present invention comprises a start control device in which the control device controls motor revolution at the startup stage. The start control device performs a direct control on a voltage to be applied to a motor at the startup stage, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently. This makes it easy to introduce a soft-start, where a startup current is suppressed and a starting torque is lowered, and then proceeds smoothly to a current feedback control to the effect of preventing an abnormal increase of revolving speed.

A washing machine motor drive device in the present invention comprises a start control device for controlling motor revolution at the startup stage for the control device. The start control device performs a direct control on a voltage to be applied to a motor at the startup stage, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the revolution speed. Besides making the shift to current feedback control smooth and suppressing the abnormal increase of revolution speed, this makes it possible to use an AC transformer, which is inexpensive, in the current detector. As a result, it is advantageous to implement a motor drive device that is inexpensive yet has high performance.

A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor which is driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, and a control device for controlling an inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently for retarding revolution of a motor. In the above-described structure where a motor current is resolved into the current component corresponding to magnetic flux and the current component corresponding to torque for performing a braking operation through vector control, a highest braking torque is yielded by vector controlling the current component corresponding to torque, while prevention of an abnormal rise of DC voltage in inverter circuit is performed by means of a control on regenerative energy, which is realized through a control on the current component corresponding to magnetic flux.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to torque is controlled to be exhibiting a certain specific value at braking operation. This makes it possible to control a braking torque to be at a certain specific value, and optimize the braking time.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to torque is controlled at braking to show a certain specific negative value. By specifying a negative torque current component, the braking torque can be controlled to show a certain specific value, and the braking time can be shortened.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux and the current component corresponding to torque are controlled at braking to exhibit, respectively, certain specific values. Under this structure, a back electromotive force of a motor and an energy consumption by the internal resistance of the motor can be controlled independently. As a result, the regenerative energy can be controlled, and an abnormal rise of DC voltage in the inverter circuit can be prevented.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is specified to be greater than that corresponding to torque, at the start of motor braking. This makes it possible to avoid an excessive braking torque exerted at the start of braking, as well as an abnormal rise of DC voltage in the inverter circuit caused by regenerative energy.

A washing machine motor drive device in the present invention comprises a revolution speed detector for detecting revolution speed based on output signal generated from the rotor position detector, and a control device for controlling in accordance with revolution speed, the current component corresponding to magnetic flux and the current component corresponding to torque to exhibit respectively certain specific values at braking. Since a braking torque and an energy consumption by the internal resistance of the motor can be controlled independently in accordance with revolution speed, an increase of regenerative energy in the high speed revolution region, as well as a decrease of braking torque in the low speed revolution region, can be prevented.

A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, a DC voltage detector for detecting DC voltage of the inverter circuit, and a control device for controlling the inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently so that the DC voltage is brought to a certain specific value at braking of a motor. In the above-described structure, where the DC voltage of inverter circuit can be controlled to meet a certain specific value through controlling the regenerative energy, energy for driving the inverter circuit is supplied from the back electromotive force of the motor. As a result, a braking failure at power failure can be prevented.

A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux or the voltage component is controlled at braking so that the DC voltage of an inverter circuit is brought to a certain specific value. Under the above-described structure, since the regenerative energy can be controlled to secure a certain specific braking torque, braking time is kept short even with a power failure.

A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, a motor electric power detector for detecting motor electric power, and a control device for controlling the inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls at braking the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with motor electric power. In the above-described structure, the balance between the back electromotive force of a motor and the energy consumption by a motor coil can be judged based on the motor electric power. Therefore, by controlling the current component corresponding to magnetic flux or the voltage component corresponding to magnetic flux in accordance with the small/large of motor electric power, a back electromotive force can be controlled so that it does not cause regeneration in the inverter circuit. Thus, an abnormal rise of DC voltage in the inverter circuit is avoided.

A washing machine motor drive device in the present invention comprises a motor electric power detector for detecting motor electric power, with which a calculation is performed based on the electric power component corresponding to magnetic flux and the electric power component corresponding to torque. Under this structure, since the motor electric power is detected instantaneously, an abnormality in the balance between the back electromotive force of the motor and the energy consumption by the motor coil can be judged instantaneously. Thus, an influence of regenerative power to the DC source in the inverter circuit can be avoided in advance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the structure of a washing machine motor drive device in accordance with a first exemplary embodiment of the present invention.

FIG. 2 is a timing chart used to describe the operation of the washing machine motor drive device in the first embodiment.

FIG. 3 is a chart showing the relationship of amplitude-electric angle .theta. in the operation of the washing machine motor drive device in the first embodiment.

FIG. 4 is a flow chart used to describe the washing operation of the washing machine motor drive device in the first embodiment.

FIG. 5 is a flow chart used to describe a dehydration operation of the washing machine motor drive device in the first embodiment.

FIG. 6 is a flow chart used to describe the operation of a motor drive subroutine in the washing machine motor drive device in the first embodiment.

FIG. 7 is a flow chart used to describe the operation of a carrier signal interruption subroutine in the washing machine motor drive device in the first embodiment.

FIG. 8 is a flow chart used to describe the operation of a position signal interruption subroutine in the washing machine motor drive device in the first embodiment.

FIG. 9 is a flow chart used to describe the operation of a revolution speed control subroutine in the washing machine motor drive device in the first embodiment.

FIG. 10 is a chart showing the relationship between motor revolution speed and current of d-axis Ids in a washing machine motor drive device in a first embodiment.

FIG. 11 is a chart showing the relationship between motor revolution speed by clothes amount and current of d-axis Ids in the washing machine motor drive device in the first embodiment.

FIG. 12 is a vector diagram showing a motor current resolved into d-axis current and q-axis current.

FIG. 13 is a block diagram showing the structure of a washing machine motor drive device in accordance with a second exemplary embodiment of the present invention.

FIG. 14 is a flow chart used to describe the operation of a start control subroutine in the washing machine motor drive device in the second embodiment.

FIG. 15 is a block diagram showing the structure of a washing machine motor drive device in accordance with a third exemplary embodiment of the present invention.

FIG. 16 is a timing chart used to describe the braking operation of the washing machine motor drive device in the third embodiment.

FIG. 17 is a motor current vector diagram showing the normal operation of the washing machine motor drive device in the third embodiment.

FIG. 18 is a motor current vector diagram showing the braking operation of the washing machine motor drive device in the third embodiment.

FIG. 19 is a flow chart used to describe the dehydration operation of the washing machine motor drive device in the third embodiment.

FIG. 20 is a flow chart used to describe the operation of a motor drive subroutine of the washing machine motor drive device in the third embodiment.

FIG. 21 is a flow chart used to describe the operation of a revolution speed control subroutine of the washing machine motor drive device in the third embodiment.

FIG. 22 is a chart showing the relationship among motor revolution speed, current of d-axis and current of q-axis of the washing machine motor drive device in the third embodiment.

FIG. 23 is a vector diagram showing motor current and motor voltage used to describe the operation of the washing machine motor drive device in the third embodiment.

FIG. 24 is a block diagram showing other structure of the washing machine motor drive device in accordance with the third embodiment.

FIG. 25 is a flow chart used to describe the operation of other revolution speed control subroutine of the washing machine motor drive device in the third embodiment.

FIG. 26 is a block diagram showing other structure of the washing machine motor drive device in the third exemplary embodiment.

FIG. 27 is a flow chart showing the operation of other carrier signal interruption subroutine of the washing machine motor drive device in the third embodiment.

FIG. 28 is block diagram showing the structure of a conventional washing machine motor drive device.

DETAILED DESCRIPTION OF THE INVENTION

Now in the following, exemplary embodiments of a washing machine motor drive device in accordance with the present invention are described in detail referring to the drawings.

Embodiment 1

FIG. 1 is a block diagram showing the structure of a washing machine motor drive device in accordance with a first exemplary embodiment of the present invention. In FIG. 1, an AC source 1 delivers alternating current to a rectifier circuit 2 to be converted there into DC power with a rectifier 20 and a capacitor 21. The DC voltage is supplied to an inverter circuit 3.

The inverter circuit 3 is a three-phase full-bridge inverter circuit which is formed of six power switching semiconductor devices and antiparallel diodes. Normally, the inverter circuit 3 has an intelligent power module (IPM) having an insulated gate bipolar transistor (IGBT) and antiparallel diodes with a built-in driver circuit and protection circuit. Output terminal of inverter circuit 3 is connected to a motor 4, the motor 4 for driving an agitator (not shown) or a washing/spinning tub (not shown).

A DC brushless motor is used for motor 4. The relative positioning (rotor position) between a rotor, which is a permanent magnet, and a stator is detected by a rotor position detector 4a. The rotor position detector 4a is normally formed of three hall ICs, and detects the position signal at each electric angle of 60.degree.. A current detector 5 is provided for detecting the phase currents Iu, Iv, Iw of motor 4, and a DC transformer that can measure low frequencies including DC current is normally used. However, an AC transformer can also detect the phase currents, and a description will be made on this point later. In the case of a three-phase motor, it is a normal practice to first obtain the current for two phases and then the remaining one phase is calculated from the Kirchhoff laws (Iu+Iv+Iw=0).

Control device 6 is provided for controlling the inverter circuit 3. The control device 6 roughly, is formed of a microcomputer, an inverter control timer (PWM timer) built in the microcomputer, a high speed AID converter, and a memory circuit (ROM, RAM), etc. Describing the control device 6 more in detail, it is formed of an electric angle detector 60 for detecting electric angle based on the output signal from rotor position detector 4a, a three-phase/two-phase d-q converter 61 for resolving into a current component Id corresponding to magnetic flux and a current component Iq corresponding torque based on the output signal from current detector 5 and the signal from electric angle detector 60, a revolution speed detector 62 for detecting rotor revolution speed, a memory unit 63 for storing sinusoidal wave data (sin, cos data) needed when converting a stationary coordinate frame into a rotational coordinate frame or vice-versa, a two-phase/three-phase d-q inverse converter 64 for converting a voltage component Vd corresponding to magnetic flux and a voltage component Vq corresponding to torque into the three-phase motor drive control voltages vu, vv, vw, and a PWM control device 65 which controls the switching of IGBT in inverter circuit 3 in accordance with the three-phase motor drive control voltages vu, vv, vw.

The control device 6 also contains a process control device 66 for controlling the start, the stop of revolution and the braking, etc. of motor 4 in accordance with a washing stage or dehydration stage, a revolution speed control device 67 for controlling the number of revolutions of motor 4 in accordance with an output signal from revolution speed detection device 62, a motor current control device 68 for calculating a voltage component Vd corresponding to magnetic flux and a voltage component Vq corresponding to torque which are needed for controlling the motor current, after comparing d-axis (direct axis) current specifying signal Ids from process control device 66 and revolution speed control device 67, q-axis (quadrature axis: horizontal axis in perpendicular amplitude modulation) current specifying signal Iqs and Id, Iq calculated from the three-phase/two-phase d-q converter 61, and a clothes amount detector 69.

A constant torque control can be implemented by introducing a feedback control so that the q-axis current Iq corresponding to torque is made to meet a specified value Iqs. However, when the revolution speed goes high the motor induction voltage rises and the torque current Iq stops increasing. So, if the d-axis current is increased in accordance with the revolution speed, the q-axis current can also be increased leading to an increased torque.

FIG. 2 shows waveforms at respective parts. The edge signal of output signals H1, H2, H3 from rotor position detector 4a changes at each 60.degree. thereby exhibiting an angle of 360.degree. divided by six. Taking the high edge of signal H1, where it goes from low to high, as reference electric angle 0.degree., the induction voltage Ec at U-phase winding of motor 4 assumes a waveform lagging behind the reference signal H1 by 30.degree.. The efficiency is maximized when the U-phase motor current Iu and the motor induction voltage Ec have a same phase. The motor induction voltage Ec takes an axis that is identical to the q-axis, while the d-axis is behind by 90.degree.. Since the q-axis current shares the same phase as the motor induction voltage, it is called a torque current.

Referring to FIG. 2, the U-phase motor current Iu is slightly ahead of the U-phase winding induction voltage Ec, while the motor voltage Vu has a waveform that is ahead of the U-phase winding induction voltage Ec by 30.degree.. The Vc represents a sawtooth carrier signal generated in the PWM control device 65, while the Vu is U-phase control voltage having a sinusoidal waveform. A PWM signal U is generated in the PWM control device 65 by comparing the carrier signal Vc and the U-phase control voltage Vu. The PWM signal is added as a control signal to the U-phase upper arm transistor in inverter circuit 3. The Ck represents a synchronous signal of the carrier signal Vc which is the interrupt signal that works when a carrier counter counts-up and overflows.

An electric angle at which the axis of rotor magnet and the axis of stator magnetic flux of motor 4 coincide is established as the d-axis, and conversion from the stationary coordinate system to the revolving coordinate system, by means of a d-q conversion, is conducted with the reference electric angle 0.degree.. So, the electric angle detector 60 detects electric angles 30.degree., 90.degree., 150.degree., etc. from the output signals H1, H2, H3 of rotor position detector 4a, and an electric angle .theta. other than that at every 60.degree. is provided by inference.

The current component that corresponds to magnetic flux is generally called the d-axis current Id. Since the magnetic flux of the permanent magnet and the magnetic flux of the field magnet share the same axis and the permanent magnet is being pulled by the field magnet, the torque at this state is zero.

An axis that takes the same phase as the induction voltage phase at 90.degree. from the d-axis in electric angle is called as q-axis, at which the torque is maximized. Since it is a current component corresponding to torque, it is referred to as q-axis current Iq. Furthermore, if the d-axis current is increased in the negative direction, it creates an effect that is equivalent to weakening the field magnet magnetic flux on d-axis. This is referred to as flux-weakening control. Since it performs a resolution into d-axis current and q-axis current, and controls them independently, it is referred to as vector control.

The three-phase/two-phase d-q converter 61 converts motor currents Iu, Iv, Iw into the d-axis current Id and the q-axis current Iq in accordance with (formula 1). The Id, Iq are calculated based on the instantaneous value of motor current detected corresponding to the electric angle .theta.. ##EQU1##

Data about the amplitude and the electric angle .theta. of sin .theta., cos .theta. shown in FIG. 3 are stored in memory unit 63. So, the resolution into d-axis current Id and q-axis current Iq can be made by calling out the data corresponding to the electric angle and doing the sum and integration thereon. Detection of the electric angle .theta. and the instantaneous value of motor current is conducted in synchronization with the carrier signal. Details of this procedure will be described later referring to a relevant flow chart.

Revolution speed detector 62 detects motor revolution counts from the output reference signal H1 of rotor position detector 4a, and delivers the signal on revolution counts to the process control device 66, the revolution speed control device 67 and the clothes amount detector 69. The process control device 66 controls the start of motor 4 and specifies number of revolutions as well as the d-axis current corresponding to the revolution counts. The revolution counts specifying signal Ns is delivered to the revolution speed control device 67, while the d-axis setting signal Ids is delivered to the motor current control device 68.

The revolution speed control device 67 is formed of a revolution counts comparison device 67a for comparing a detected number of revolutions N with revolution count specifying signal Ns, and a torque current specifying device 67b for controlling q-axis current specified value Iqs in accordance with an error signal .DELTA.N between revolution counts N and specified revolution counts Ns and a shift ratio (acceleration) of revolution speed. It controls the q-axis current Iq corresponding to torque of motor 4 to meet with the specified value Iqs.

The motor current control device 68 outputs control voltage signals Vq, Vd after comparing the output signals Iq, Id of three-phase/two-phase d-q converter 61 with the specified signals Iqs, Ids, respectively. The motor current control device 68 is formed of a q-axis current comparison device 68a, a q-axis voltage specifying device 68c a d-axis current comparison device 68b and a d-axis voltage specifying device 68d, and generates voltage signals Vq, Vd, which control the q-axis current and the d-axis current, respectively.

The two-phase/three-phase d-q inverse converter 64 calculates three-phase motor drive control voltages vu, vv, vw from voltage signals Vq, Vd in accordance with (formula 2). The inverse converter 64 delivers in synchronization with the carrier signal, the sinusoidal waveform signal that corresponds to the electric angle .theta. detected by the electric angle detector 60 to the PWM control device. The method of processing the sin .theta. and cos .theta. data stored in memory unit 63 remains almost the same as that used in the three-phase/two-phase d-q converter 61. ##EQU2##

Next, the operation of the control device 6 built in the washing machine motor drive device in the first embodiment of the present invention is described. FIG. 4 is a flow chart showing the washing operation in accordance with the present invention. The washing starts at step S100, various initial settings for washing are made at step S101, and then at S102 the amount of clothes within a washing/spinning tub is detected. The clothes amount is generally detected by moving the agitator with motor 4 and observing the startup speed of motor revolution, or observing the internal revolution after discontinuation of driving.

At S103, water level, water flow, etc. for the clothes amount are specified, and then a water feed valve (not shown) is opened at S104, whether or not the level of water in washing/spinning tub reached the specified level is judged at S105. As soon as it reaches the specified level, the water feed valve is shut at S106, if the specified level has not yet been reached, the level the water feed valve is kept open.

An agitation process starts at S107, and based on a flag, forward revolution or reverse revolution is judged. If the judgement is forward revolution, the operation proceeds to S108 to drive the motor 4 in forward direction, or if reverse revolution is indicated, the operation proceeds to S109 to drive the motor in reverse direction. A detailed flow chart for driving the motor will be described later at a motor drive subroutine referring to FIG. 6.

After the motor drive subroutine is executed and the agitator is put in operation for a certain specific time, the forward/reverse flag is controlled at S110, and then the operation proceeds to S111 and the motor 4 is stopped for a certain specific time span. Then the operation proceeds to S112, where it is judged whether the washing procedure is finished or not. If the washing procedure is judged to be finished, the operation proceeds to the subsequent step, if the washing procedure is judged not to be finished, the operation returns to S107.

FIG. 5 is a flow chart of the dehydration operation. The dehydration operation starts at step S120, the highest revolving speed Ns max. during the dehydration operation, the speed of increasing the revolution, and the like initial settings are made at S121, and then at S122, the revolution speed is specified so that the specified revolution speed goes higher along with the lapse of time.

Then at S123, a motor drive subroutine shown in FIG. 6 is executed, and at S124 whether or not the specified revolution speed Ns reached the highest value Ns max. is judged. When the highest value Ns max. is reached, the operation proceeds to S125, where whether or not the motor revolution speed N is substantially identical to the highest specified value Ns max. is judged. If the revolution speed N has not yet reached within a range of a certain specified number of revolutions, the operation proceeds to S126 to have the d-axis current specified value Ids increased in the negative direction and then proceeds to S127. If the revolution speed N is substantially identical with the highest specified value Ns max., the operation jumps to S127 without executing S1126 executed.

At S127, whether or not the dehydration operation is finished is judged. If judged finished, the operation proceeds to S128 for braking. Braking step S128 involves turning the torque instruction in the motor drive subroutine negative. Namely, if the q-axis current is set to be negative, the motor 4 goes into braking operation. In this stage, however, an appropriate d-axis current needs to be provided in order to prevent a back electromotive force from causing regenerative power in the DC source side, which might result in a high tension DC voltage destroying power semiconductor devices in the rectifier circuit 2 and the inverter circuit 3.

FIG. 6 is a flow chart of a motor drive subroutine. The subroutine starts at step S200. Step S201 is the initial setting performed at the beginning of execution of the subroutine, where the parameter exchange with the main routine and various other settings are made, and then the subroutine proceeds to S202 for initiating the revolution start control. The steps S201 and S202 are executed only once at the start.

The start control is performed by applying a certain voltage to a motor for 120.degree. at the initial stage, where revolution speed feedback control is impossible. It provides a soft start by starting with a low voltage and gradually raising the voltage along with the lapse of time.

Then at S203, whether or not there is an interrupting carrier signal is determined. The interrupting carrier signal arises when carrier counter at PWM control means 65 overflows and generates an interruption signal ck. If there is an interruption signal ck, the subroutine proceeds to S204 to execute a carrier signal interruption subroutine.

The carrier signal interruption subroutine is shown in detail in a flow chart in FIG. 7. Referring to FIG. 7, the subroutine starts at S300, and counts the interruption signal ck at S301. Then at S302, the subroutine calculates the rotor position electric angle .theta.. The rotor position signal .theta. is obtained through an inference, by adding a value k.multidot..DELTA..theta., which has been made available separately by multiplying an electric angle .DELTA..theta. for one carrier signal cycle with a count value k of carrier counter, and the electric angle .phi. detected by the rotor position detector 4a at each 60.degree..

Assuming that the motor 4 is an 8-pole motor, the carrier frequency is 15.6 kHz, the revolution speed is 900 r/m, the motor driving frequency becomes 60 Hz and the count value k of carrier counter within electric angle 60.degree. becomes approximately 43. Accordingly, the .DELTA..theta. is approximately 1.4.degree.. Since the count value k within electric angle 60.degree. increases and the processing capability for detecting and defining the electric angle improves at a lower revolution speed of a motor, it can be understood that the present processing works well even in a case where the revolution speed is low and the required level of precision is high.

Now at S303, motor currents Iu, Iv are detected. If the current is detected only once, there remains a possibility of a noise contained therein. So at S304, the current detection is performed once again. At S305, the mean value is provided in order to remove the noise, and motor current Iw is calculated in accordance with a formula, Iw=-(Iu+Iv).

At S306, the calculation as shown in (formula 1) is conducted from the electric angle .theta. and the motor current, and the three-phase/two-phase d-q conversion is made to yield the d-axis current Id, the q-axis current Iq. Then at S307, the Id, Iq are stored in a memory to be used separately as data for revolution speed control.

At S308, the d-axis control voltage Vd and the q-axis control voltage Vq are called, and then at S309 the two-phase/three-phase d-q inverse conversion is performed as per the (formula 2) to yield the three-phase control voltages vu, vv, vw. The inverse conversion is performed in the same way as in S306, using the data of sin .theta., cos .theta. corresponding to electric angle stored in memory unit 63, by sum and integration at high speed. At S31, the PWM control is performed corresponding to the three-phase control voltages vu, vv, vw, and then at S310 the carrier signal interruption subroutine is returned.

The PWM control, as described earlier referring to FIG. 2, compares the sawtooth (or triangular) carrier signal with the control voltages vu, vv, vw, corresponding to each of the U-phase, V-phase, W-phase, to generate IGBT on/off control signal of inverter circuit 3, for applying a sinusoidal wave drive to the motor 4. The waveform of signals in the upper arm transistor and lower arm transistor is reversed with respect to each other. When the conduction ratio is increased with the upper arm transistor, the output voltage increases in positive voltage, and when the conduction ratio of the lower arm transistor is increased, the output voltage increases in negative voltage. At the conduction ratio of 50%, the output voltage becomes zero.

When the control voltage is changed in the sinusoidal waveform in correspondence to electric angle .theta., electric current of sinusoidal waveform flows. In the case of sinusoidal waveform driving, the output voltage reaches the highest with the rate of modulation Am 100% when the conduction ratio of transistor is made to be the maximum 100% and the output voltage becomes the lowest with the rate of modulation Am of 0% when the highest value of the conduction ratio is made to be 50%.

After the carrier signal interruption subroutine shown in FIG. 7 is executed, the motor drive subroutine shown in FIG. 6 is returned to, and proceeds to S205 where judgement is made as to whether or not there is an interruption of position signal. When either one of the position signals H1, H2, H3 is changed, an interruption signal is generated, and the subroutine proceeds to S206 to execute the position signal interruption subroutine shown in FIG. 8. The interruption signal is generated at each electric angle 60.degree., as shown in FIG. 2.

Now reference is made to FIG. 8 where a position signal interruption subroutine starts at S400. At S401, position signals H1, H2, H3 are input, and at S402 rotor electric angle .theta.c is detected from the position signal. At S403, the count value k counted by the carrier signal interruption subroutine is memorized in kc, then at S404 the count value k is cleared, and then at S405 electric angle .DELTA..theta. of one carrier is calculated from the carrier counter count value kc in the electric angle 60.degree..

At S406, judgement is made as to whether it is an interruption signal by the reference position signal H1. If it is the reference position signal, the subroutine proceeds to S407 where the count value T of a revolution cycle measuring timer is memorized as cycle To. And then at S408, the timer T is cleared, and number of motor revolutions N is calculated at S409. At S410, counting at the revolution cycle measuring timer is started, and at S411 the position signal interruption subroutine is returned.

Assuming the capability of detecting and defining in the revolution cycle measuring timer to be at precision level 8 bit, the clock becomes 64 .mu.s, so the carrier signal can be used for the clock. In order to improve the capability of revolution control, the capability of detecting and defining the revolution cycle needs to be raised, and the clock cycle needs to be set at somewhere within a range 1-10 .mu.s. In this case, the system clock of the microcomputer may be divided for use as the clock.

After the position signal interruption subroutine of FIG. 8 is executed, the motor drive subroutine shown in FIG. 6 is returned to for executing a revolution speed control subroutine at S207. Details of the revolution speed control subroutine are shown in FIG. 9.

Referring to FIG. 9, a revolution speed control subroutine starts at S500, the number of motor revolutions N is called at S501, and then at S502 the d-axis current value Ids is specified in accordance with number of revolutions. A relationship between the number of motor revolutions and the d-axis current -Ids is on the graph shown in FIG. 10. At a low revolution speed, the d-axis current value -Ids is set at zero; in a revolution speed higher than a certain specific value, the Ids is increased in the negative direction in accordance with the number of revolutions.

The number of motor revolutions may either be a detected revolution or a specified revolution. However, the control stability is improved when the d-axis current specified value Ids is increased in the negative direction in accordance with specified number of revolutions Ns. Namely, in a case where the -Ids is increased in accordance with detected revolution speed, the -Ids increases along with increasing number of revolutions, and the increased -Ids causes an increased revolution speed. So, in a case of a small load, the revolution speed control is feared to go out of control.

At S503, the d-axis current Id obtained at three-phase/two-phase d-q converter 61 is called, and at S504, large/small of the Id and Ids is compared. If the d-axis current Id is judged larger than the specified value Ids, the subroutine proceeds to S505 to have the d-axis control voltage Vd decreased; if the d-axis current Id is judged smaller than the specified value Ids, the subroutine proceeds to S506 to have the d-axis control voltage Vd increased.

At S507, the q-axis current Iq obtained at three-phase/two-phase d-q converter 61 is called, and at S508, large/small of the Iq and Iqs is compared. If the q-axis current Iq is judged larger than the specified value Iqs, the subroutine proceeds to S509 to have the q-axis control voltage Vq decreased; if the q-axis current Iq is judged smaller than the specified value Iqs, the subroutine proceeds to S510 to have the q-axis control voltage Vq increased. Next at S511, the calculated d-axis control voltage Vd and q-axis control voltage Vq are memorized respectively, and then at S512 the revolution speed control subroutine is returned.

Since the d-axis current Id and the q-axis current Iq are converted at approximately each carrier signal, there is a large fluctuation, including torque ripple. If the converted d-axis current Id and the converted q-axis current Iq are compared to the specified values of Ids and Iqs at each carrier, there will be too many fluctuation factors, which would lead to an instability of control. Therefore, averaging or like concept of integration needs to be added to.

Because of the above reason, the revolution control subroutine S207 is not executed in the carrier signal interruption subroutine S204, or the position signal interruption subroutine S206, but is executed independently in a motor drive control subroutine as shown in FIG. 6. For the purpose of a quicker response in the revolution control, it may be considered to have the subroutine executed in a position signal interruption subroutine. However, it is to be noted that the response speed might turn out to be slow in a case where the revolution speed is low.

Referring to FIG. 10, when the d-axis current specified value -Ids is increased in accordance with the specified revolution speed, it becomes a flux-weakening control at high speed revolution. So, the torque can be increased by increasing a motor current. During high speed revolution for dehydration, among other operations, the number of spinning revolutions can be specified to be high by increasing the d-axis current specified value -Ids. This leads to a higher rate of dehydration.

In order to specify the revolution speed to also be high for a washing-agitation operation, the d-axis current specified value -Ids may be increased. This implements a high speed revolution with an increased torque. So, the washing torque can be increased for encountering a high clothes amount. This leads to a higher rate of washing.

As described in the foregoing, since control is performed by specifying the d-axis current value Ids at substantially zero in the low speed revolution region, the operation is conducted at a maximum efficiency; while in the high speed revolution region, the d-axis current value -Ids is specified to be high for a high torque operation. So, the motor efficiency can be improved during dehydration operation or washing operation.

FIG. 11 shows a case where the d-axis current specified value -Ids, which corresponds to revolution speed, is varied in accordance with the amount of clothes. Curve A represents a case where the clothes amount detector 69 judged that the amount of clothes is large, while curve B repres