Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2002-07-02
2004-05-18
Duda, Rina (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S055000, C318S059000, C318S062000, C318S071000, C318S269000, C318S272000, C318S431000, C318S432000, C318S254100, C068S012020, C068S012160
Reexamination Certificate
active
06737828
ABSTRACT:
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
126
a
,
126
b
,
126
c
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 i
Hagiwara Hisashi
Kiuchi Mitsuyuki
Kondo Norimasa
Tamae Sadayuki
Duda Rina
Martin Edgardo San
Wenderoth , Lind & Ponack, L.L.P.
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